Study of sub-pixel position resolution with time-correlated transient signals in 3D pixelated CdZnTe detectors with varying pixel sizes

NASA Astrophysics Data System (ADS)

Ocampo Giraldo, L.; Bolotnikov, A. E.; Camarda, G. S.; De Geronimo, G.; Fried, J.; Gul, R.; Hodges, D.; Hossain, A.; Ünlü, K.; Vernon, E.; Yang, G.; James, R. B.

2018-03-01

We evaluated the sub-pixel position resolution achievable in large-volume CdZnTe pixelated detectors with conventional pixel patterns and for several different pixel sizes: 2.8 mm, 1.72 mm, 1.4 mm and 0.8 mm. Achieving position resolution below the physical dimensions of pixels (sub-pixel resolution) is a practical path for making high-granularity position-sensitive detectors, <100 μm, using a limited number of pixels dictated by the mechanical constraints and multi-channel readout electronics. High position sensitivity is important for improving the imaging capability of CZT gamma cameras. It also allows for making more accurate corrections of response non-uniformities caused by crystal defects, thus enabling use of standard-grade (unselected) and less expensive CZT crystals for producing large-volume position-sensitive CZT detectors feasible for many practical applications. We analyzed the digitized charge signals from a representative 9 pixels and the cathode, generated using a pulsed-laser light beam focused down to 10 μm (650 nm) to scan over a selected 3 × 3 pixel area. We applied our digital pulse processing technique to the time-correlated signals captured from adjacent pixels to achieve and evaluate the capability for sub-pixel position resolution. As an example, we also demonstrated an application of 3D corrections to improve the energy resolution and positional information of the events for the tested detectors.

Study of sub-pixel position resolution with time-correlated transient signals in 3D pixelated CdZnTe detectors with varying pixel sizes

DOE PAGES

Giraldo, L. Ocampo; Bolotnikov, A. E.; Camarda, G. S.; ...

2017-12-18

Here, we evaluated the sub-pixel position resolution achievable in large-volume CdZnTe pixelated detectors with conventional pixel patterns and for several different pixel sizes: 2.8 mm, 1.72 mm, 1.4 mm and 0.8 mm. Achieving position resolution below the physical dimensions of pixels (sub-pixel resolution) is a practical path for making high-granularity position-sensitive detectors, <100 μμm, using a limited number of pixels dictated by the mechanical constraints and multi-channel readout electronics. High position sensitivity is important for improving the imaging capability of CZT gamma cameras. It also allows for making more accurate corrections of response non-uniformities caused by crystal defects, thus enablingmore » use of standard-grade (unselected) and less expensive CZT crystals for producing large-volume position-sensitive CZT detectors feasible for many practical applications. We analyzed the digitized charge signals from a representative 9 pixels and the cathode, generated using a pulsed-laser light beam focused down to 10 m (650 nm) to scan over a selected 3×3 pixel area. We applied our digital pulse processing technique to the time-correlated signals captured from adjacent pixels to achieve and evaluate the capability for sub-pixel position resolution. As an example, we also demonstrated an application of 3D corrections to improve the energy resolution and positional information of the events for the tested detectors.« less

Study of sub-pixel position resolution with time-correlated transient signals in 3D pixelated CdZnTe detectors with varying pixel sizes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Giraldo, L. Ocampo; Bolotnikov, A. E.; Camarda, G. S.

Here, we evaluated the sub-pixel position resolution achievable in large-volume CdZnTe pixelated detectors with conventional pixel patterns and for several different pixel sizes: 2.8 mm, 1.72 mm, 1.4 mm and 0.8 mm. Achieving position resolution below the physical dimensions of pixels (sub-pixel resolution) is a practical path for making high-granularity position-sensitive detectors, <100 μμm, using a limited number of pixels dictated by the mechanical constraints and multi-channel readout electronics. High position sensitivity is important for improving the imaging capability of CZT gamma cameras. It also allows for making more accurate corrections of response non-uniformities caused by crystal defects, thus enablingmore » use of standard-grade (unselected) and less expensive CZT crystals for producing large-volume position-sensitive CZT detectors feasible for many practical applications. We analyzed the digitized charge signals from a representative 9 pixels and the cathode, generated using a pulsed-laser light beam focused down to 10 m (650 nm) to scan over a selected 3×3 pixel area. We applied our digital pulse processing technique to the time-correlated signals captured from adjacent pixels to achieve and evaluate the capability for sub-pixel position resolution. As an example, we also demonstrated an application of 3D corrections to improve the energy resolution and positional information of the events for the tested detectors.« less

The Substructure of the Solar Corona Observed in the Hi-C Telescope

NASA Technical Reports Server (NTRS)

Winebarger, A.; Cirtain, J.; Golub, L.; DeLuca, E.; Savage, S.; Alexander, C.; Schuler, T.

2014-01-01

In the summer of 2012, the High-resolution Coronal Imager (Hi-C) flew aboard a NASA sounding rocket and collected the highest spatial resolution images ever obtained of the solar corona. One of the goals of the Hi-C flight was to characterize the substructure of the solar corona. We therefore calculate how the intensity scales from a low-resolution (AIA) pixels to high-resolution (Hi-C) pixels for both the dynamic events and "background" emission (meaning, the steady emission over the 5 minutes of data acquisition time). We find there is no evidence of substructure in the background corona; the intensity scales smoothly from low-resolution to high-resolution Hi-C pixels. In transient events, however, the intensity observed with Hi-C is, on average, 2.6 times larger than observed with AIA. This increase in intensity suggests that AIA is not resolving these events. This result suggests a finely structured dynamic corona embedded in a smoothly varying background.

Optimum viewing distance for target acquisition

NASA Astrophysics Data System (ADS)

Holst, Gerald C.

2015-05-01

Human visual system (HVS) "resolution" (a.k.a. visual acuity) varies with illumination level, target characteristics, and target contrast. For signage, computer displays, cell phones, and TVs a viewing distance and display size are selected. Then the number of display pixels is chosen such that each pixel subtends 1 min-1. Resolution of low contrast targets is quite different. It is best described by Barten's contrast sensitivity function. Target acquisition models predict maximum range when the display pixel subtends 3.3 min-1. The optimum viewing distance is nearly independent of magnification. Noise increases the optimum viewing distance.

Wavelength scanning achieves pixel super-resolution in holographic on-chip microscopy

NASA Astrophysics Data System (ADS)

Luo, Wei; Göröcs, Zoltan; Zhang, Yibo; Feizi, Alborz; Greenbaum, Alon; Ozcan, Aydogan

2016-03-01

Lensfree holographic on-chip imaging is a potent solution for high-resolution and field-portable bright-field imaging over a wide field-of-view. Previous lensfree imaging approaches utilize a pixel super-resolution technique, which relies on sub-pixel lateral displacements between the lensfree diffraction patterns and the image sensor's pixel-array, to achieve sub-micron resolution under unit magnification using state-of-the-art CMOS imager chips, commonly used in e.g., mobile-phones. Here we report, for the first time, a wavelength scanning based pixel super-resolution technique in lensfree holographic imaging. We developed an iterative super-resolution algorithm, which generates high-resolution reconstructions of the specimen from low-resolution (i.e., under-sampled) diffraction patterns recorded at multiple wavelengths within a narrow spectral range (e.g., 10-30 nm). Compared with lateral shift-based pixel super-resolution, this wavelength scanning approach does not require any physical shifts in the imaging setup, and the resolution improvement is uniform in all directions across the sensor-array. Our wavelength scanning super-resolution approach can also be integrated with multi-height and/or multi-angle on-chip imaging techniques to obtain even higher resolution reconstructions. For example, using wavelength scanning together with multi-angle illumination, we achieved a halfpitch resolution of 250 nm, corresponding to a numerical aperture of 1. In addition to pixel super-resolution, the small scanning steps in wavelength also enable us to robustly unwrap phase, revealing the specimen's optical path length in our reconstructed images. We believe that this new wavelength scanning based pixel super-resolution approach can provide competitive microscopy solutions for high-resolution and field-portable imaging needs, potentially impacting tele-pathology applications in resource-limited-settings.

A CMOS-based high-resolution fluoroscope (HRF) detector prototype with 49.5μm pixels for use in endovascular image guided interventions (EIGI)

NASA Astrophysics Data System (ADS)

Russ, M.; Shankar, A.; Setlur Nagesh, S. V.; Ionita, C. N.; Bednarek, D. R.; Rudin, S.

2017-03-01

X-ray detectors to meet the high-resolution requirements for endovascular image-guided interventions (EIGIs) are being developed and evaluated. A new 49.5-micron pixel prototype detector is being investigated and compared to the current suite of high-resolution fluoroscopic (HRF) detectors. This detector featuring a 300-micron thick CsI(Tl) scintillator, and low electronic noise CMOS readout is designated the HRF- CMOS50. To compare the abilities of this detector with other existing high resolution detectors, a standard performance metric analysis was applied, including the determination of the modulation transfer function (MTF), noise power spectra (NPS), noise equivalent quanta (NEQ), and detective quantum efficiency (DQE) for a range of energies and exposure levels. The advantage of the smaller pixel size and reduced blurring due to the thin phosphor was exemplified when the MTF of the HRF-CMOS50 was compared to the other high resolution detectors, which utilize larger pixels, other optical designs or thicker scintillators. However, the thinner scintillator has the disadvantage of a lower quantum detective efficiency (QDE) for higher diagnostic x-ray energies. The performance of the detector as part of an imaging chain was examined by employing the generalized metrics GMTF, GNEQ, and GDQE, taking standard focal spot size and clinical imaging parameters into consideration. As expected, the disparaging effects of focal spot unsharpness, exacerbated by increasing magnification, degraded the higher-frequency performance of the HRF-CMOS50, while increasing scatter fraction diminished low-frequency performance. Nevertheless, the HRF-CMOS50 brings improved resolution capabilities for EIGIs, but would require increased sensitivity and dynamic range for future clinical application.

Portable lensless wide-field microscopy imaging platform based on digital inline holography and multi-frame pixel super-resolution

PubMed Central

Sobieranski, Antonio C; Inci, Fatih; Tekin, H Cumhur; Yuksekkaya, Mehmet; Comunello, Eros; Cobra, Daniel; von Wangenheim, Aldo; Demirci, Utkan

2017-01-01

In this paper, an irregular displacement-based lensless wide-field microscopy imaging platform is presented by combining digital in-line holography and computational pixel super-resolution using multi-frame processing. The samples are illuminated by a nearly coherent illumination system, where the hologram shadows are projected into a complementary metal-oxide semiconductor-based imaging sensor. To increase the resolution, a multi-frame pixel resolution approach is employed to produce a single holographic image from multiple frame observations of the scene, with small planar displacements. Displacements are resolved by a hybrid approach: (i) alignment of the LR images by a fast feature-based registration method, and (ii) fine adjustment of the sub-pixel information using a continuous optimization approach designed to find the global optimum solution. Numerical method for phase-retrieval is applied to decode the signal and reconstruct the morphological details of the analyzed sample. The presented approach was evaluated with various biological samples including sperm and platelets, whose dimensions are in the order of a few microns. The obtained results demonstrate a spatial resolution of 1.55 µm on a field-of-view of ≈30 mm2. PMID:29657866

Circuit for high resolution decoding of multi-anode microchannel array detectors

NASA Technical Reports Server (NTRS)

Kasle, David B. (Inventor)

1995-01-01

A circuit for high resolution decoding of multi-anode microchannel array detectors consisting of input registers accepting transient inputs from the anode array; anode encoding logic circuits connected to the input registers; midpoint pipeline registers connected to the anode encoding logic circuits; and pixel decoding logic circuits connected to the midpoint pipeline registers is described. A high resolution algorithm circuit operates in parallel with the pixel decoding logic circuit and computes a high resolution least significant bit to enhance the multianode microchannel array detector's spatial resolution by halving the pixel size and doubling the number of pixels in each axis of the anode array. A multiplexer is connected to the pixel decoding logic circuit and allows a user selectable pixel address output according to the actual multi-anode microchannel array detector anode array size. An output register concatenates the high resolution least significant bit onto the standard ten bit pixel address location to provide an eleven bit pixel address, and also stores the full eleven bit pixel address. A timing and control state machine is connected to the input registers, the anode encoding logic circuits, and the output register for managing the overall operation of the circuit.

Time multiplexing for increased FOV and resolution in virtual reality

NASA Astrophysics Data System (ADS)

Miñano, Juan C.; Benitez, Pablo; Grabovičkić, Dejan; Zamora, Pablo; Buljan, Marina; Narasimhan, Bharathwaj

2017-06-01

We introduce a time multiplexing strategy to increase the total pixel count of the virtual image seen in a VR headset. This translates into an improvement of the pixel density or the Field of View FOV (or both) A given virtual image is displayed by generating a succession of partial real images, each representing part of the virtual image and together representing the virtual image. Each partial real image uses the full set of physical pixels available in the display. The partial real images are successively formed and combine spatially and temporally to form a virtual image viewable from the eye position. Partial real images are imaged through different optical channels depending of its time slot. Shutters or other schemes are used to avoid that a partial real image be imaged through the wrong optical channels or at the wrong time slot. This time multiplexing strategy needs real images be shown at high frame rates (>120fps). Available display and shutters technologies are discussed. Several optical designs for achieving this time multiplexing scheme in a compact format are shown. This time multiplexing scheme allows increasing the resolution/FOV of the virtual image not only by increasing the physical pixel density but also by decreasing the pixels switching time, a feature that may be simpler to achieve in certain circumstances.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gao, Lan; Hill, K. W.; Bitter, M.

Here, a high spatial resolution of a few μm is often required for probing small-scale high-energy-density plasmas using high resolution x-ray imaging spectroscopy. This resolution can be achieved by adjusting system magnification to overcome the inherent limitation of the detector pixel size. Laboratory experiments on investigating the relation between spatial resolution and system magnification for a spherical crystal spectrometer are presented. Tungsten Lβ 2 rays from a tungsten-target micro-focus x-ray tube were diffracted by a Ge 440 crystal, which was spherically bent to a radius of 223 mm, and imaged onto an x-ray CCD with 13-μm pixel size. The source-to-crystalmore » (p) and crystal-to-detector (q) distances were varied to produce spatial magnifications ( M = q/p) ranging from 2 to 10. The inferred instrumental spatial width reduces with increasing system magnification M. However, the experimental measurement at each M is larger than the theoretical value of pixel size divided by M. Future work will focus on investigating possible broadening mechanisms that limit the spatial resolution.« less

Velocity map imaging using an in-vacuum pixel detector.

PubMed

Gademann, Georg; Huismans, Ymkje; Gijsbertsen, Arjan; Jungmann, Julia; Visschers, Jan; Vrakking, Marc J J

2009-10-01

The use of a new type in-vacuum pixel detector in velocity map imaging (VMI) is introduced. The Medipix2 and Timepix semiconductor pixel detectors (256 x 256 square pixels, 55 x 55 microm2) are well suited for charged particle detection. They offer high resolution, low noise, and high quantum efficiency. The Medipix2 chip allows double energy discrimination by offering a low and a high energy threshold. The Timepix detector allows to record the incidence time of a particle with a temporal resolution of 10 ns and a dynamic range of 160 micros. Results of the first time application of the Medipix2 detector to VMI are presented, investigating the quantum efficiency as well as the possibility to operate at increased background pressure in the vacuum chamber.

Characterization of Pixelated Cadmium-Zinc-Telluride Detectors for Astrophysical Applications

NASA Technical Reports Server (NTRS)

Gaskin, Jessica; Sharma, Dharma; Ramsey, Brian; Seller, Paul

2003-01-01

Comparisons of charge sharing and charge loss measurements between two pixelated Cadmium-Zinc-Telluride (CdZnTe) detectors are discussed. These properties along with the detector geometry help to define the limiting energy resolution and spatial resolution of the detector in question. The first detector consists of a 1-mm-thick piece of CdZnTe sputtered with a 4x4 array of pixels with pixel pitch of 750 microns (inter-pixel gap is 100 microns). Signal readout is via discrete ultra-low-noise preamplifiers, one for each of the 16 pixels. The second detector consists of a 2-mm-thick piece of CdZnTe sputtered with a 16x16 array of pixels with a pixel pitch of 300 microns (inter-pixel gap is 50 microns). This crystal is bonded to a custom-built readout chip (ASIC) providing all front-end electronics to each of the 256 independent pixels. These detectors act as precursors to that which will be used at the focal plane of the High Energy Replicated Optics (HERO) telescope currently being developed at Marshall Space Flight Center. With a telescope focal length of 6 meters, the detector needs to have a spatial resolution of around 200 microns in order to take full advantage of the HERO angular resolution. We discuss to what degree charge sharing will degrade energy resolution but will improve our spatial resolution through position interpolation.

Evaluation of position-estimation methods applied to CZT-based photon-counting detectors for dedicated breast CT

PubMed Central

Makeev, Andrey; Clajus, Martin; Snyder, Scott; Wang, Xiaolang; Glick, Stephen J.

2015-01-01

Abstract. Semiconductor photon-counting detectors based on high atomic number, high density materials [cadmium zinc telluride (CZT)/cadmium telluride (CdTe)] for x-ray computed tomography (CT) provide advantages over conventional energy-integrating detectors, including reduced electronic and Swank noise, wider dynamic range, capability of spectral CT, and improved signal-to-noise ratio. Certain CT applications require high spatial resolution. In breast CT, for example, visualization of microcalcifications and assessment of tumor microvasculature after contrast enhancement require resolution on the order of 100  μm. A straightforward approach to increasing spatial resolution of pixellated CZT-based radiation detectors by merely decreasing the pixel size leads to two problems: (1) fabricating circuitry with small pixels becomes costly and (2) inter-pixel charge spreading can obviate any improvement in spatial resolution. We have used computer simulations to investigate position estimation algorithms that utilize charge sharing to achieve subpixel position resolution. To study these algorithms, we model a simple detector geometry with a 5×5 array of 200  μm pixels, and use a conditional probability function to model charge transport in CZT. We used COMSOL finite element method software to map the distribution of charge pulses and the Monte Carlo package PENELOPE for simulating fluorescent radiation. Performance of two x-ray interaction position estimation algorithms was evaluated: the method of maximum-likelihood estimation and a fast, practical algorithm that can be implemented in a readout application-specific integrated circuit and allows for identification of a quadrant of the pixel in which the interaction occurred. Both methods demonstrate good subpixel resolution; however, their actual efficiency is limited by the presence of fluorescent K-escape photons. Current experimental breast CT systems typically use detectors with a pixel size of 194  μm, with 2×2 binning during the acquisition giving an effective pixel size of 388  μm. Thus, it would be expected that the position estimate accuracy reported in this study would improve detection and visualization of microcalcifications as compared to that with conventional detectors. PMID:26158095

Evaluation of position-estimation methods applied to CZT-based photon-counting detectors for dedicated breast CT.

PubMed

Makeev, Andrey; Clajus, Martin; Snyder, Scott; Wang, Xiaolang; Glick, Stephen J

2015-04-01

Semiconductor photon-counting detectors based on high atomic number, high density materials [cadmium zinc telluride (CZT)/cadmium telluride (CdTe)] for x-ray computed tomography (CT) provide advantages over conventional energy-integrating detectors, including reduced electronic and Swank noise, wider dynamic range, capability of spectral CT, and improved signal-to-noise ratio. Certain CT applications require high spatial resolution. In breast CT, for example, visualization of microcalcifications and assessment of tumor microvasculature after contrast enhancement require resolution on the order of [Formula: see text]. A straightforward approach to increasing spatial resolution of pixellated CZT-based radiation detectors by merely decreasing the pixel size leads to two problems: (1) fabricating circuitry with small pixels becomes costly and (2) inter-pixel charge spreading can obviate any improvement in spatial resolution. We have used computer simulations to investigate position estimation algorithms that utilize charge sharing to achieve subpixel position resolution. To study these algorithms, we model a simple detector geometry with a [Formula: see text] array of [Formula: see text] pixels, and use a conditional probability function to model charge transport in CZT. We used COMSOL finite element method software to map the distribution of charge pulses and the Monte Carlo package PENELOPE for simulating fluorescent radiation. Performance of two x-ray interaction position estimation algorithms was evaluated: the method of maximum-likelihood estimation and a fast, practical algorithm that can be implemented in a readout application-specific integrated circuit and allows for identification of a quadrant of the pixel in which the interaction occurred. Both methods demonstrate good subpixel resolution; however, their actual efficiency is limited by the presence of fluorescent [Formula: see text]-escape photons. Current experimental breast CT systems typically use detectors with a pixel size of [Formula: see text], with [Formula: see text] binning during the acquisition giving an effective pixel size of [Formula: see text]. Thus, it would be expected that the position estimate accuracy reported in this study would improve detection and visualization of microcalcifications as compared to that with conventional detectors.

Spatial resolution of a spherical x-ray crystal spectrometer at various magnifications

DOE PAGES

Gao, Lan; Hill, K. W.; Bitter, M.; ...

2016-08-23

Here, a high spatial resolution of a few μm is often required for probing small-scale high-energy-density plasmas using high resolution x-ray imaging spectroscopy. This resolution can be achieved by adjusting system magnification to overcome the inherent limitation of the detector pixel size. Laboratory experiments on investigating the relation between spatial resolution and system magnification for a spherical crystal spectrometer are presented. Tungsten Lβ 2 rays from a tungsten-target micro-focus x-ray tube were diffracted by a Ge 440 crystal, which was spherically bent to a radius of 223 mm, and imaged onto an x-ray CCD with 13-μm pixel size. The source-to-crystalmore » (p) and crystal-to-detector (q) distances were varied to produce spatial magnifications ( M = q/p) ranging from 2 to 10. The inferred instrumental spatial width reduces with increasing system magnification M. However, the experimental measurement at each M is larger than the theoretical value of pixel size divided by M. Future work will focus on investigating possible broadening mechanisms that limit the spatial resolution.« less

Dual-gate photo thin-film transistor: a “smart” pixel for high- resolution and low-dose X-ray imaging

NASA Astrophysics Data System (ADS)

Wang, Kai; Ou, Hai; Chen, Jun

2015-06-01

Since its emergence a decade ago, amorphous silicon flat panel X-ray detector has established itself as a ubiquitous platform for an array of digital radiography modalities. The fundamental building block of a flat panel detector is called a pixel. In all current pixel architectures, sensing, storage, and readout are unanimously kept separate, inevitably compromising resolution by increasing pixel size. To address this issue, we hereby propose a “smart” pixel architecture where the aforementioned three components are combined in a single dual-gate photo thin-film transistor (TFT). In other words, the dual-gate photo TFT itself functions as a sensor, a storage capacitor, and a switch concurrently. Additionally, by harnessing the amplification effect of such a thin-film transistor, we for the first time created a single-transistor active pixel sensor. The proof-of-concept device had a W/L ratio of 250μm/20μm and was fabricated using a simple five-mask photolithography process, where a 130nm transparent ITO was used as the top photo gate, and a 200nm amorphous silicon as the absorbing channel layer. The preliminary results demonstrated that the photocurrent had been increased by four orders of magnitude due to light-induced threshold voltage shift in the sub-threshold region. The device sensitivity could be simply tuned by photo gate bias to specifically target low-level light detection. The dependence of threshold voltage on light illumination indicated that a dynamic range of at least 80dB could be achieved. The "smart" pixel technology holds tremendous promise for developing high-resolution and low-dose X-ray imaging and may potentially lower the cancer risk imposed by radiation, especially among paediatric patients.

Framework for Detection and Localization of Extreme Climate Event with Pixel Recursive Super Resolution

NASA Astrophysics Data System (ADS)

Kim, S. K.; Lee, J.; Zhang, C.; Ames, S.; Williams, D. N.

2017-12-01

Deep learning techniques have been successfully applied to solve many problems in climate and geoscience using massive-scaled observed and modeled data. For extreme climate event detections, several models based on deep neural networks have been recently proposed and attend superior performance that overshadows all previous handcrafted expert based method. The issue arising, though, is that accurate localization of events requires high quality of climate data. In this work, we propose framework capable of detecting and localizing extreme climate events in very coarse climate data. Our framework is based on two models using deep neural networks, (1) Convolutional Neural Networks (CNNs) to detect and localize extreme climate events, and (2) Pixel recursive recursive super resolution model to reconstruct high resolution climate data from low resolution climate data. Based on our preliminary work, we have presented two CNNs in our framework for different purposes, detection and localization. Our results using CNNs for extreme climate events detection shows that simple neural nets can capture the pattern of extreme climate events with high accuracy from very coarse reanalysis data. However, localization accuracy is relatively low due to the coarse resolution. To resolve this issue, the pixel recursive super resolution model reconstructs the resolution of input of localization CNNs. We present a best networks using pixel recursive super resolution model that synthesizes details of tropical cyclone in ground truth data while enhancing their resolution. Therefore, this approach not only dramat- ically reduces the human effort, but also suggests possibility to reduce computing cost required for downscaling process to increase resolution of data.

Per-Pixel Coded Exposure for High-Speed and High-Resolution Imaging Using a Digital Micromirror Device Camera

PubMed Central

Feng, Wei; Zhang, Fumin; Qu, Xinghua; Zheng, Shiwei

2016-01-01

High-speed photography is an important tool for studying rapid physical phenomena. However, low-frame-rate CCD (charge coupled device) or CMOS (complementary metal oxide semiconductor) camera cannot effectively capture the rapid phenomena with high-speed and high-resolution. In this paper, we incorporate the hardware restrictions of existing image sensors, design the sampling functions, and implement a hardware prototype with a digital micromirror device (DMD) camera in which spatial and temporal information can be flexibly modulated. Combined with the optical model of DMD camera, we theoretically analyze the per-pixel coded exposure and propose a three-element median quicksort method to increase the temporal resolution of the imaging system. Theoretically, this approach can rapidly increase the temporal resolution several, or even hundreds, of times without increasing bandwidth requirements of the camera. We demonstrate the effectiveness of our method via extensive examples and achieve 100 fps (frames per second) gain in temporal resolution by using a 25 fps camera. PMID:26959023

Per-Pixel Coded Exposure for High-Speed and High-Resolution Imaging Using a Digital Micromirror Device Camera.

PubMed

Feng, Wei; Zhang, Fumin; Qu, Xinghua; Zheng, Shiwei

2016-03-04

High-speed photography is an important tool for studying rapid physical phenomena. However, low-frame-rate CCD (charge coupled device) or CMOS (complementary metal oxide semiconductor) camera cannot effectively capture the rapid phenomena with high-speed and high-resolution. In this paper, we incorporate the hardware restrictions of existing image sensors, design the sampling functions, and implement a hardware prototype with a digital micromirror device (DMD) camera in which spatial and temporal information can be flexibly modulated. Combined with the optical model of DMD camera, we theoretically analyze the per-pixel coded exposure and propose a three-element median quicksort method to increase the temporal resolution of the imaging system. Theoretically, this approach can rapidly increase the temporal resolution several, or even hundreds, of times without increasing bandwidth requirements of the camera. We demonstrate the effectiveness of our method via extensive examples and achieve 100 fps (frames per second) gain in temporal resolution by using a 25 fps camera.

Achieving subpixel resolution with time-correlated transient signals in pixelated CdZnTe gamma-ray sensors using a focused laser beam (Conference Presentation)

NASA Astrophysics Data System (ADS)

Ocampo Giraldo, Luis A.; Bolotnikov, Aleksey E.; Camarda, Giuseppe S.; Cui, Yonggang; De Geronimo, Gianluigi; Gul, Rubi; Fried, Jack; Hossain, Anwar; Unlu, Kenan; Vernon, Emerson; Yang, Ge; James, Ralph B.

2017-05-01

High-resolution position-sensitive detectors have been proposed to correct response non-uniformities in Cadmium Zinc Telluride (CZT) crystals by virtually subdividing the detectors area into small voxels and equalizing responses from each voxel. 3D pixelated detectors coupled with multichannel readout electronics are the most advanced type of CZT devices offering many options in signal processing and enhancing detector performance. One recent innovation proposed for pixelated detectors is to use the induced (transient) signals from neighboring pixels to achieve high sub-pixel position resolution while keeping large pixel sizes. The main hurdle in achieving this goal is the relatively low signal induced on the neighboring pixels because of the electrostatic shielding effect caused by the collecting pixel. In addition, to achieve high position sensitivity one should rely on time-correlated transient signals, which means that digitized output signals must be used. We present the results of our studies to measure the amplitude of the pixel signals so that these can be used to measure positions of the interaction points. This is done with the processing of digitized correlated time signals measured from several adjacent pixels taking into account rise-time and charge-sharing effects. In these measurements we used a focused pulsed laser to generate a 10-micron beam at one milliwatt (650-nm wavelength) over the detector surface while the collecting pixel was moved in cardinal directions. The results include measurements that present the benefits of combining conventional pixel geometry with digital pulse processing for the best approach in achieving sub-pixel position resolution with the pixel dimensions of approximately 2 mm. We also present the sub-pixel resolution measurements at comparable energies from various gamma emitting isotopes.

Velocity map imaging using an in-vacuum pixel detector

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gademann, Georg; Huismans, Ymkje; Gijsbertsen, Arjan

The use of a new type in-vacuum pixel detector in velocity map imaging (VMI) is introduced. The Medipix2 and Timepix semiconductor pixel detectors (256x256 square pixels, 55x55 {mu}m{sup 2}) are well suited for charged particle detection. They offer high resolution, low noise, and high quantum efficiency. The Medipix2 chip allows double energy discrimination by offering a low and a high energy threshold. The Timepix detector allows to record the incidence time of a particle with a temporal resolution of 10 ns and a dynamic range of 160 {mu}s. Results of the first time application of the Medipix2 detector to VMImore » are presented, investigating the quantum efficiency as well as the possibility to operate at increased background pressure in the vacuum chamber.« less

Improvement of spatial resolution in a Timepix based CdTe photon counting detector using ToT method

NASA Astrophysics Data System (ADS)

Park, Kyeongjin; Lee, Daehee; Lim, Kyung Taek; Kim, Giyoon; Chang, Hojong; Yi, Yun; Cho, Gyuseong

2018-05-01

Photon counting detectors (PCDs) have been recognized as potential candidates in X-ray radiography and computed tomography due to their many advantages over conventional energy-integrating detectors. In particular, a PCD-based X-ray system shows an improved contrast-to-noise ratio, reduced radiation exposure dose, and more importantly, exhibits a capability for material decomposition with energy binning. For some applications, a very high resolution is required, which translates into smaller pixel size. Unfortunately, small pixels may suffer from energy spectral distortions (distortion in energy resolution) due to charge sharing effects (CSEs). In this work, we propose a method for correcting CSEs by measuring the point of interaction of an incident X-ray photon by the time-of-threshold (ToT) method. Moreover, we also show that it is possible to obtain an X-ray image with a reduced pixel size by using the concept of virtual pixels at a given pixel size. To verify the proposed method, modulation transfer function (MTF) and signal-to-noise ratio (SNR) measurements were carried out with the Timepix chip combined with the CdTe pixel sensor. The X-ray test condition was set at 80 kVp with 5 μA, and a tungsten edge phantom and a lead line phantom were used for the measurements. Enhanced spatial resolution was achieved by applying the proposed method when compared to that of the conventional photon counting method. From experiment results, MTF increased from 6.3 (conventional counting method) to 8.3 lp/mm (proposed method) at 0.3 MTF. On the other hand, the SNR decreased from 33.08 to 26.85 dB due to four virtual pixels.

Synthetic aperture radar images with composite azimuth resolution

DOEpatents

Bielek, Timothy P; Bickel, Douglas L

2015-03-31

A synthetic aperture radar (SAR) image is produced by using all phase histories of a set of phase histories to produce a first pixel array having a first azimuth resolution, and using less than all phase histories of the set to produce a second pixel array having a second azimuth resolution that is coarser than the first azimuth resolution. The first and second pixel arrays are combined to produce a third pixel array defining a desired SAR image that shows distinct shadows of moving objects while preserving detail in stationary background clutter.

Pixelation Effects in Weak Lensing

NASA Technical Reports Server (NTRS)

High, F. William; Rhodes, Jason; Massey, Richard; Ellis, Richard

2007-01-01

Weak gravitational lensing can be used to investigate both dark matter and dark energy but requires accurate measurements of the shapes of faint, distant galaxies. Such measurements are hindered by the finite resolution and pixel scale of digital cameras. We investigate the optimum choice of pixel scale for a space-based mission, using the engineering model and survey strategy of the proposed Supernova Acceleration Probe as a baseline. We do this by simulating realistic astronomical images containing a known input shear signal and then attempting to recover the signal using the Rhodes, Refregier, and Groth algorithm. We find that the quality of shear measurement is always improved by smaller pixels. However, in practice, telescopes are usually limited to a finite number of pixels and operational life span, so the total area of a survey increases with pixel size. We therefore fix the survey lifetime and the number of pixels in the focal plane while varying the pixel scale, thereby effectively varying the survey size. In a pure trade-off for image resolution versus survey area, we find that measurements of the matter power spectrum would have minimum statistical error with a pixel scale of 0.09' for a 0.14' FWHM point-spread function (PSF). The pixel scale could be increased to 0.16' if images dithered by exactly half-pixel offsets were always available. Some of our results do depend on our adopted shape measurement method and should be regarded as an upper limit: future pipelines may require smaller pixels to overcome systematic floors not yet accessible, and, in certain circumstances, measuring the shape of the PSF might be more difficult than those of galaxies. However, the relative trends in our analysis are robust, especially those of the surface density of resolved galaxies. Our approach thus provides a snapshot of potential in available technology, and a practical counterpart to analytic studies of pixelation, which necessarily assume an idealized shape measurement method.

Investigation of the limitations of the highly pixilated CdZnTe detector for PET applications

PubMed Central

Komarov, Sergey; Yin, Yongzhi; Wu, Heyu; Wen, Jie; Krawczynski, Henric; Meng, Ling-Jian; Tai, Yuan-Chuan

2016-01-01

We are investigating the feasibility of a high resolution positron emission tomography (PET) insert device based on the CdZnTe detector with 350 μm anode pixel pitch to be integrated into a conventional animal PET scanner to improve its image resolution. In this paper, we have used a simplified version of the multi pixel CdZnTe planar detector, 5 mm thick with 9 anode pixels only. This simplified 9 anode pixel structure makes it possible to carry out experiments without a complete application-specific integrated circuits readout system that is still under development. Special attention was paid to the double pixel (or charge sharing) detections. The following characteristics were obtained in experiment: energy resolution full-width-at-half-maximum (FWHM) is 7% for single pixel and 9% for double pixel photoelectric detections of 511 keV gammas; timing resolution (FWHM) from the anode signals is 30 ns for single pixel and 35 ns for double pixel detections (for photoelectric interactions only the corresponding values are 20 and 25 ns); position resolution is 350 μm in x,y-plane and ~0.4 mm in depth-of-interaction. The experimental measurements were accompanied by Monte Carlo (MC) simulations to find a limitation imposed by spatial charge distribution. Results from MC simulations suggest the limitation of the intrinsic spatial resolution of the CdZnTe detector for 511 keV photoelectric interactions is 170 μm. The interpixel interpolation cannot recover the resolution beyond the limit mentioned above for photoelectric interactions. However, it is possible to achieve higher spatial resolution using interpolation for Compton scattered events. Energy and timing resolution of the proposed 350 μm anode pixel pitch detector is no better than 0.6% FWHM at 511 keV, and 2 ns FWHM, respectively. These MC results should be used as a guide to understand the performance limits of the pixelated CdZnTe detector due to the underlying detection processes, with the understanding of the inherent limitations of MC methods. PMID:23079763

Investigation of the limitations of the highly pixilated CdZnTe detector for PET applications.

PubMed

Komarov, Sergey; Yin, Yongzhi; Wu, Heyu; Wen, Jie; Krawczynski, Henric; Meng, Ling-Jian; Tai, Yuan-Chuan

2012-11-21

We are investigating the feasibility of a high resolution positron emission tomography (PET) insert device based on the CdZnTe detector with 350 µm anode pixel pitch to be integrated into a conventional animal PET scanner to improve its image resolution. In this paper, we have used a simplified version of the multi pixel CdZnTe planar detector, 5 mm thick with 9 anode pixels only. This simplified 9 anode pixel structure makes it possible to carry out experiments without a complete application-specific integrated circuits readout system that is still under development. Special attention was paid to the double pixel (or charge sharing) detections. The following characteristics were obtained in experiment: energy resolution full-width-at-half-maximum (FWHM) is 7% for single pixel and 9% for double pixel photoelectric detections of 511 keV gammas; timing resolution (FWHM) from the anode signals is 30 ns for single pixel and 35 ns for double pixel detections (for photoelectric interactions only the corresponding values are 20 and 25 ns); position resolution is 350 µm in x,y-plane and ∼0.4 mm in depth-of-interaction. The experimental measurements were accompanied by Monte Carlo (MC) simulations to find a limitation imposed by spatial charge distribution. Results from MC simulations suggest the limitation of the intrinsic spatial resolution of the CdZnTe detector for 511 keV photoelectric interactions is 170 µm. The interpixel interpolation cannot recover the resolution beyond the limit mentioned above for photoelectric interactions. However, it is possible to achieve higher spatial resolution using interpolation for Compton scattered events. Energy and timing resolution of the proposed 350 µm anode pixel pitch detector is no better than 0.6% FWHM at 511 keV, and 2 ns FWHM, respectively. These MC results should be used as a guide to understand the performance limits of the pixelated CdZnTe detector due to the underlying detection processes, with the understanding of the inherent limitations of MC methods.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gao, Lan, E-mail: lgao@pppl.gov; Hill, K. W.; Bitter, M.

A high spatial resolution of a few μm is often required for probing small-scale high-energy-density plasmas using high resolution x-ray imaging spectroscopy. This resolution can be achieved by adjusting system magnification to overcome the inherent limitation of the detector pixel size. Laboratory experiments on investigating the relation between spatial resolution and system magnification for a spherical crystal spectrometer are presented. Tungsten Lβ{sub 2} rays from a tungsten-target micro-focus x-ray tube were diffracted by a Ge 440 crystal, which was spherically bent to a radius of 223 mm, and imaged onto an x-ray CCD with 13-μm pixel size. The source-to-crystal (p)more » and crystal-to-detector (q) distances were varied to produce spatial magnifications (M = q/p) ranging from 2 to 10. The inferred instrumental spatial width reduces with increasing system magnification M. However, the experimental measurement at each M is larger than the theoretical value of pixel size divided by M. Future work will focus on investigating possible broadening mechanisms that limit the spatial resolution.« less

Automatic Sub-Pixel Co-Registration of LandSat-8 OLI and Sentinel-2A MSI Images Using Phase Correlation and Machine Learning Based Mapping

NASA Technical Reports Server (NTRS)

Skakun, Sergii; Roger, Jean-Claude; Vermote, Eric F.; Masek, Jeffrey G.; Justice, Christopher O.

2017-01-01

This study investigates misregistration issues between Landsat-8/OLI and Sentinel-2A/MSI at 30 m resolution, and between multi-temporal Sentinel-2A images at 10 m resolution using a phase correlation approach and multiple transformation functions. Co-registration of 45 Landsat-8 to Sentinel-2A pairs and 37 Sentinel-2A to Sentinel-2A pairs were analyzed. Phase correlation proved to be a robust approach that allowed us to identify hundreds and thousands of control points on images acquired more than 100 days apart. Overall, misregistration of up to 1.6 pixels at 30 m resolution between Landsat-8 and Sentinel-2A images, and 1.2 pixels and 2.8 pixels at 10 m resolution between multi-temporal Sentinel-2A images from the same and different orbits, respectively, were observed. The non-linear Random Forest regression used for constructing the mapping function showed best results in terms of root mean square error (RMSE), yielding an average RMSE error of 0.07+/-0.02 pixels at 30 m resolution, and 0.09+/-0.05 and 0.15+/-0.06 pixels at 10 m resolution for the same and adjacent Sentinel-2A orbits, respectively, for multiple tiles and multiple conditions. A simpler 1st order polynomial function (affine transformation) yielded RMSE of 0.08+/-0.02 pixels at 30 m resolution and 0.12+/-0.06 (same Sentinel-2A orbits) and 0.20+/-0.09 (adjacent orbits) pixels at 10 m resolution.

NASA/GEWEX shortwave surface radiation budget: Integrated data product with reprocessed radiance, cloud, and meteorology inputs, and new surface albedo treatment

NASA Astrophysics Data System (ADS)

Cox, Stephen J.; Stackhouse, Paul W.; Gupta, Shashi K.; Mikovitz, J. Colleen; Zhang, Taiping

2017-02-01

The NASA/GEWEX Surface Radiation Budget (SRB) project produces shortwave and longwave surface and top of atmosphere radiative fluxes for the 1983-near present time period. Spatial resolution is 1 degree. The current Release 3.0 (available at gewex-srb.larc.nasa.gov) uses the International Satellite Cloud Climatology Project (ISCCP) DX product for pixel level radiance and cloud information. This product is subsampled to 30 km. ISCCP is currently recalibrating and recomputing their entire data series, to be released as the H product, at 10km resolution. The ninefold increase in pixel number will allow SRB a higher resolution gridded product (e.g. 0.5 degree), as well as the production of pixel-level fluxes. Other key input improvements include a detailed aerosol history using the Max Planck Institute Aerosol Climatology (MAC), and temperature and moisture profiles from nnHIRS.

Construction of pixel-level resolution DEMs from monocular images by shape and albedo from shading constrained with low-resolution DEM

NASA Astrophysics Data System (ADS)

Wu, Bo; Liu, Wai Chung; Grumpe, Arne; Wöhler, Christian

2018-06-01

Lunar Digital Elevation Model (DEM) is important for lunar successful landing and exploration missions. Lunar DEMs are typically generated by photogrammetry or laser altimetry approaches. Photogrammetric methods require multiple stereo images of the region of interest and it may not be applicable in cases where stereo coverage is not available. In contrast, reflectance based shape reconstruction techniques, such as shape from shading (SfS) and shape and albedo from shading (SAfS), apply monocular images to generate DEMs with pixel-level resolution. We present a novel hierarchical SAfS method that refines a lower-resolution DEM to pixel-level resolution given a monocular image with known light source. We also estimate the corresponding pixel-wise albedo map in the process and based on that to regularize the shape reconstruction with pixel-level resolution based on the low-resolution DEM. In this study, a Lunar-Lambertian reflectance model is applied to estimate the albedo map. Experiments were carried out using monocular images from the Lunar Reconnaissance Orbiter Narrow Angle Camera (LRO NAC), with spatial resolution of 0.5-1.5 m per pixel, constrained by the Selenological and Engineering Explorer and LRO Elevation Model (SLDEM), with spatial resolution of 60 m. The results indicate that local details are well recovered by the proposed algorithm with plausible albedo estimation. The low-frequency topographic consistency depends on the quality of low-resolution DEM and the resolution difference between the image and the low-resolution DEM.

Resolution and quality enhancement in terahertz in-line holography by sub-pixel sampling with double-distance reconstruction.

PubMed

Li, Zeyu; Li, Lei; Qin, Yu; Li, Guangbin; Wang, Du; Zhou, Xun

2016-09-05

We demonstrate the enhancement of resolution and image quality in terahertz (THz) lens-free in-line digital holography by sub-pixel sampling with double-distance reconstruction. Multiple sub-pixel shifted low-resolution (LR) holograms recorded by a pyroelectric array detector (100 μm × 100 μm pixel pitch, 124 × 124 pixels) are aligned precisely to synthesize a high-resolution (HR) hologram. By this method, the lateral resolution is no more limited by the pixel pitch, and lateral resolution of 150 μm is obtained, which corresponds to 1.26λ with respect to the illuminating wavelength of 118.8 μm (2.52 THz). Compared with other published works, to date, this is the highest resolution in THz digital holography when considering the illuminating wavelength. In addition, to suppress the twin-image and zero-order artifacts, the complex amplitude distributions of both object and illuminaing background wave fields are reconstructed simultaneously. This is achieved by iterative phase retrieval between the double HR holograms and background images at two recording planes, which does not require any constraints on object plane or a priori knowledge of the sample.

Multi-Scale Fractal Analysis of Image Texture and Pattern

NASA Technical Reports Server (NTRS)

Emerson, Charles W.; Lam, Nina Siu-Ngan; Quattrochi, Dale A.

1999-01-01

Analyses of the fractal dimension of Normalized Difference Vegetation Index (NDVI) images of homogeneous land covers near Huntsville, Alabama revealed that the fractal dimension of an image of an agricultural land cover indicates greater complexity as pixel size increases, a forested land cover gradually grows smoother, and an urban image remains roughly self-similar over the range of pixel sizes analyzed (10 to 80 meters). A similar analysis of Landsat Thematic Mapper images of the East Humboldt Range in Nevada taken four months apart show a more complex relation between pixel size and fractal dimension. The major visible difference between the spring and late summer NDVI images is the absence of high elevation snow cover in the summer image. This change significantly alters the relation between fractal dimension and pixel size. The slope of the fractal dimension-resolution relation provides indications of how image classification or feature identification will be affected by changes in sensor spatial resolution.

Multi-Scale Fractal Analysis of Image Texture and Pattern

NASA Technical Reports Server (NTRS)

Emerson, Charles W.; Lam, Nina Siu-Ngan; Quattrochi, Dale A.

1999-01-01

Analyses of the fractal dimension of Normalized Difference Vegetation Index (NDVI) images of homogeneous land covers near Huntsville, Alabama revealed that the fractal dimension of an image of an agricultural land cover indicates greater complexity as pixel size increases, a forested land cover gradually grows smoother, and an urban image remains roughly self-similar over the range of pixel sizes analyzed (10 to 80 meters). A similar analysis of Landsat Thematic Mapper images of the East Humboldt Range in Nevada taken four months apart show a more complex relation between pixel size and fractal dimension. The major visible difference between the spring and late summer NDVI images of the absence of high elevation snow cover in the summer image. This change significantly alters the relation between fractal dimension and pixel size. The slope of the fractal dimensional-resolution relation provides indications of how image classification or feature identification will be affected by changes in sensor spatial resolution.

Spatial resolution requirements for automated cartographic road extraction

USGS Publications Warehouse

Benjamin, S.; Gaydos, L.

1990-01-01

Ground resolution requirements for detection and extraction of road locations in a digitized large-scale photographic database were investigated. A color infrared photograph of Sunnyvale, California was scanned, registered to a map grid, and spatially degraded to 1- to 5-metre resolution pixels. Road locations in each data set were extracted using a combination of image processing and CAD programs. These locations were compared to a photointerpretation of road locations to determine a preferred pixel size for the extraction method. Based on road pixel omission error computations, a 3-metre pixel resolution appears to be the best choice for this extraction method. -Authors

Development of pixellated Ir-TESs

NASA Astrophysics Data System (ADS)

Zen, Nobuyuki; Takahashi, Hiroyuki; Kunieda, Yuichi; Damayanthi, Rathnayaka M. T.; Mori, Fumiakira; Fujita, Kaoru; Nakazawa, Masaharu; Fukuda, Daiji; Ohkubo, Masataka

2006-04-01

We have been developing Ir-based pixellated superconducting transition edge sensors (TESs). In the area of material or astronomical applications, the sensor with few eV energy resolution and over 1000 pixels imaging property is desired. In order to achieve this goal, we have been analyzing signals from pixellated TESs. In the case of a 20 pixel array of Ir-TESs, with 45 μm×45 μm pixel sizes, the incident X-ray signals have been classified into 16 groups. We have applied numerical signal analysis. On the one hand, the energy resolution of our pixellated TES is strongly degraded. However, using pulse shape analysis, we can dramatically improve the resolution. Thus, we consider that the pulse signal analysis will lead this device to be used as a practical photon incident position identifying TES.

Multi-Decadal Pathfinder Data Sets of Global Land Biophysical Variables from AVHRR and MODIS and their Use in GCM Studies of Biogeophysics and Biogeochemistry

NASA Technical Reports Server (NTRS)

Myneni, Ranga

2003-01-01

The problem of how the scale, or spatial resolution, of reflectance data impacts retrievals of vegetation leaf area index (LAI) and fraction absorbed photosynthetically active radiation (PAR) has been investigated. We define the goal of scaling as the process by which it is established that LAI and FPAR values derived from coarse resolution sensor data equal the arithmetic average of values derived independently from fine resolution sensor data. The increasing probability of land cover mixtures with decreasing resolution is defined as heterogeneity, which is a key concept in scaling studies. The effect of pixel heterogeneity on spectral reflectances and LAI/FPAR retrievals is investigated with 1 km Advanced Very High Resolution Radiometer (AVHRR) data aggregated to different coarse spatial resolutions. It is shown that LAI retrieval errors at coarse resolution are inversely related to the proportion of the dominant land cover in such pixel. Further, large errors in LAI retrievals are incurred when forests are minority biomes in non-forest pixels compared to when forest biomes are mixed with one another, and vice-versa. A physically based technique for scaling with explicit spatial resolution dependent radiative transfer formulation is developed. The successful application of this theory to scaling LAI retrievals from AVHRR data of different resolutions is demonstrated

Development of a 300,000-pixel ultrahigh-speed high-sensitivity CCD

NASA Astrophysics Data System (ADS)

Ohtake, H.; Hayashida, T.; Kitamura, K.; Arai, T.; Yonai, J.; Tanioka, K.; Maruyama, H.; Etoh, T. Goji; Poggemann, D.; Ruckelshausen, A.; van Kuijk, H.; Bosiers, Jan T.

2006-02-01

We are developing an ultrahigh-speed, high-sensitivity broadcast camera that is capable of capturing clear, smooth slow-motion videos even where lighting is limited, such as at professional baseball games played at night. In earlier work, we developed an ultrahigh-speed broadcast color camera1) using three 80,000-pixel ultrahigh-speed, highsensitivity CCDs2). This camera had about ten times the sensitivity of standard high-speed cameras, and enabled an entirely new style of presentation for sports broadcasts and science programs. Most notably, increasing the pixel count is crucially important for applying ultrahigh-speed, high-sensitivity CCDs to HDTV broadcasting. This paper provides a summary of our experimental development aimed at improving the resolution of CCD even further: a new ultrahigh-speed high-sensitivity CCD that increases the pixel count four-fold to 300,000 pixels.

Design and fabrication of AlGaInP-based micro-light-emitting-diode array devices

NASA Astrophysics Data System (ADS)

Bao, Xingzhen; Liang, Jingqiu; Liang, Zhongzhu; Wang, Weibiao; Tian, Chao; Qin, Yuxin; Lü, Jinguang

2016-04-01

An integrated high-resolution (individual pixel size 80 μm×80 μm) solid-state self-emissive active matrix programmed with 320×240 micro-light-emitting-diode arrays structure was designed and fabricated on an AlGaInP semiconductor chip using micro electro-mechanical systems, microstructure and semiconductor fabricating techniques. Row pixels share a p-electrode and line pixels share an n-electrode. We experimentally investigated GaAs substrate thickness affects the electrical and optical characteristics of the pixels. For a 150-μm-thick GaAs substrate, the single pixel output power was 167.4 μW at 5 mA, and increased to 326.4 μW when current increase to 10 mA. The device investigated potentially plays an important role in many fields.

Beam test results of the BTeV silicon pixel detector

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gabriele Chiodini et al.

2000-09-28

The authors have described the results of the BTeV silicon pixel detector beam test. The pixel detectors under test used samples of the first two generations of Fermilab pixel readout chips, FPIX0 and FPIX1, (indium bump-bonded to ATLAS sensor prototypes). The spatial resolution achieved using analog charge information is excellent for a large range of track inclination. The resolution is still very good using only 2-bit charge information. A relatively small dependence of the resolution on bias voltage is observed. The resolution is observed to depend dramatically on the discriminator threshold, and it deteriorates rapidly for threshold above 4000e{sup {minus}}.

An Integrated Photogrammetric and Photoclinometric Approach for Pixel-Resolution 3d Modelling of Lunar Surface

NASA Astrophysics Data System (ADS)

Liu, W. C.; Wu, B.

2018-04-01

High-resolution 3D modelling of lunar surface is important for lunar scientific research and exploration missions. Photogrammetry is known for 3D mapping and modelling from a pair of stereo images based on dense image matching. However dense matching may fail in poorly textured areas and in situations when the image pair has large illumination differences. As a result, the actual achievable spatial resolution of the 3D model from photogrammetry is limited by the performance of dense image matching. On the other hand, photoclinometry (i.e., shape from shading) is characterised by its ability to recover pixel-wise surface shapes based on image intensity and imaging conditions such as illumination and viewing directions. More robust shape reconstruction through photoclinometry can be achieved by incorporating images acquired under different illumination conditions (i.e., photometric stereo). Introducing photoclinometry into photogrammetric processing can therefore effectively increase the achievable resolution of the mapping result while maintaining its overall accuracy. This research presents an integrated photogrammetric and photoclinometric approach for pixel-resolution 3D modelling of the lunar surface. First, photoclinometry is interacted with stereo image matching to create robust and spatially well distributed dense conjugate points. Then, based on the 3D point cloud derived from photogrammetric processing of the dense conjugate points, photoclinometry is further introduced to derive the 3D positions of the unmatched points and to refine the final point cloud. The approach is able to produce one 3D point for each image pixel within the overlapping area of the stereo pair so that to obtain pixel-resolution 3D models. Experiments using the Lunar Reconnaissance Orbiter Camera - Narrow Angle Camera (LROC NAC) images show the superior performances of the approach compared with traditional photogrammetric technique. The results and findings from this research contribute to optimal exploitation of image information for high-resolution 3D modelling of the lunar surface, which is of significance for the advancement of lunar and planetary mapping.

Automatic Segmentation of Fluorescence Lifetime Microscopy Images of Cells Using Multi-Resolution Community Detection -A First Study

PubMed Central

Hu, Dandan; Sarder, Pinaki; Ronhovde, Peter; Orthaus, Sandra; Achilefu, Samuel; Nussinov, Zohar

2014-01-01

Inspired by a multi-resolution community detection (MCD) based network segmentation method, we suggest an automatic method for segmenting fluorescence lifetime (FLT) imaging microscopy (FLIM) images of cells in a first pilot investigation on two selected images. The image processing problem is framed as identifying segments with respective average FLTs against the background in FLIM images. The proposed method segments a FLIM image for a given resolution of the network defined using image pixels as the nodes and similarity between the FLTs of the pixels as the edges. In the resulting segmentation, low network resolution leads to larger segments, and high network resolution leads to smaller segments. Further, using the proposed method, the mean-square error (MSE) in estimating the FLT segments in a FLIM image was found to consistently decrease with increasing resolution of the corresponding network. The MCD method appeared to perform better than a popular spectral clustering based method in performing FLIM image segmentation. At high resolution, the spectral segmentation method introduced noisy segments in its output, and it was unable to achieve a consistent decrease in MSE with increasing resolution. PMID:24251410

High resolution laboratory grating-based x-ray phase-contrast CT

NASA Astrophysics Data System (ADS)

Viermetz, Manuel P.; Birnbacher, Lorenz J. B.; Fehringer, Andreas; Willner, Marian; Noel, Peter B.; Pfeiffer, Franz; Herzen, Julia

2017-03-01

Grating-based phase-contrast computed tomography (gbPC-CT) is a promising imaging method for imaging of soft tissue contrast without the need of any contrast agent. The focus of this study is the increase in spatial resolution without loss in sensitivity to allow visualization of pathologies comparable to the convincing results obtained at the synchrotron. To improve the effective pixel size a super-resolution reconstruction based on subpixel shifts involving a deconvolution of the image is applied on differential phase-contrast data. In our study we could achieve an effective pixel sizes of 28mm without any drawback in terms of sensitivity or the ability to measure quantitative data.

Fabrication and characterization of a 0.5-mm lutetium oxyorthosilicate detector array for high-resolution PET applications.

PubMed

Stickel, Jennifer R; Qi, Jinyi; Cherry, Simon R

2007-01-01

With the increasing use of in vivo imaging in mouse models of disease, there are many interesting applications that demand imaging of organs and tissues with submillimeter resolution. Though there are other contributing factors, the spatial resolution in small-animal PET is still largely determined by the detector pixel dimensions. In this work, a pair of lutetium oxyorthosilicate (LSO) arrays with 0.5-mm pixels was coupled to multichannel photomultiplier tubes and evaluated for use as high-resolution PET detectors. Flood histograms demonstrated that most crystals were clearly identifiable. Energy resolution varied from 22% to 38%. The coincidence timing resolution was 1.42-ns full width at half maximum (FWHM). The intrinsic spatial resolution was 0.68-mm FWHM as measured with a 30-gauge needle filled with (18)F. The improvement in spatial resolution in a tomographic setting is demonstrated using images of a line source phantom reconstructed with filtered backprojection and compared with images obtained from 2 dedicated small-animal PET scanners. Finally, a projection image of the mouse foot is shown to demonstrate the application of these 0.5-mm LSO detectors to a biologic task. A pair of highly pixelated LSO detections has been constructed and characterized for use as high-spatial-resolution PET detectors. It appears that small-animal PET systems capable of a FWHM spatial resolution of 600 microm or less are feasible and should be pursued.

Array-scale performance of TES X-ray Calorimeters Suitable for Constellation-X

NASA Technical Reports Server (NTRS)

Kilbourne, C. A.; Bandler, S. R.; Brown, A. D.; Chervenak, J. A.; Eckart, M. E.; Finkbeiner, F. M.; Iyomoto, N.; Kelley, R. L.; Porter, F. S.; Smith, S. J.;

Impact of defective pixels in AMLCDs on the perception of medical images

NASA Astrophysics Data System (ADS)

Kimpe, Tom; Sneyders, Yuri

2006-03-01

With LCD displays, each pixel has its own individual transistor that controls the transmittance of that pixel. Occasionally, these individual transistors will short or alternatively malfunction, resulting in a defective pixel that always shows the same brightness. With ever increasing resolution of displays the number of defect pixels per display increases accordingly. State of the art processes are capable of producing displays with no more than one faulty transistor out of 3 million. A five Mega Pixel medical LCD panel contains 15 million individual sub pixels (3 sub pixels per pixel), each having an individual transistor. This means that a five Mega Pixel display on average will have 5 failing pixels. This paper investigates the visibility of defective pixels and analyzes the possible impact of defective pixels on the perception of medical images. JND simulations were done to study the effect of defective pixels on medical images. Our results indicate that defective LCD pixels can mask subtle features in medical images in an unexpectedly broad area around the defect and therefore may reduce the quality of diagnosis for specific high-demanding areas such as mammography. As a second contribution an innovative solution is proposed. A specialized image processing algorithm can make defective pixels completely invisible and moreover can also recover the information of the defect so that the radiologist perceives the medical image correctly. This correction algorithm has been validated with both JND simulations and psycho visual tests.

Lensfree on-chip microscopy over a wide field-of-view using pixel super-resolution

PubMed Central

Bishara, Waheb; Su, Ting-Wei; Coskun, Ahmet F.; Ozcan, Aydogan

2010-01-01

We demonstrate lensfree holographic microscopy on a chip to achieve ~0.6 µm spatial resolution corresponding to a numerical aperture of ~0.5 over a large field-of-view of ~24 mm2. By using partially coherent illumination from a large aperture (~50 µm), we acquire lower resolution lensfree in-line holograms of the objects with unit fringe magnification. For each lensfree hologram, the pixel size at the sensor chip limits the spatial resolution of the reconstructed image. To circumvent this limitation, we implement a sub-pixel shifting based super-resolution algorithm to effectively recover much higher resolution digital holograms of the objects, permitting sub-micron spatial resolution to be achieved across the entire sensor chip active area, which is also equivalent to the imaging field-of-view (24 mm2) due to unit magnification. We demonstrate the success of this pixel super-resolution approach by imaging patterned transparent substrates, blood smear samples, as well as Caenoharbditis Elegans. PMID:20588977

All-passive pixel super-resolution of time-stretch imaging

PubMed Central

Chan, Antony C. S.; Ng, Ho-Cheung; Bogaraju, Sharat C. V.; So, Hayden K. H.; Lam, Edmund Y.; Tsia, Kevin K.

2017-01-01

Based on image encoding in a serial-temporal format, optical time-stretch imaging entails a stringent requirement of state-of-the-art fast data acquisition unit in order to preserve high image resolution at an ultrahigh frame rate — hampering the widespread utilities of such technology. Here, we propose a pixel super-resolution (pixel-SR) technique tailored for time-stretch imaging that preserves pixel resolution at a relaxed sampling rate. It harnesses the subpixel shifts between image frames inherently introduced by asynchronous digital sampling of the continuous time-stretch imaging process. Precise pixel registration is thus accomplished without any active opto-mechanical subpixel-shift control or other additional hardware. Here, we present the experimental pixel-SR image reconstruction pipeline that restores high-resolution time-stretch images of microparticles and biological cells (phytoplankton) at a relaxed sampling rate (≈2–5 GSa/s)—more than four times lower than the originally required readout rate (20 GSa/s) — is thus effective for high-throughput label-free, morphology-based cellular classification down to single-cell precision. Upon integration with the high-throughput image processing technology, this pixel-SR time-stretch imaging technique represents a cost-effective and practical solution for large scale cell-based phenotypic screening in biomedical diagnosis and machine vision for quality control in manufacturing. PMID:28303936

Angular resolution of the gaseous micro-pixel detector Gossip

NASA Astrophysics Data System (ADS)

Bilevych, Y.; Blanco Carballo, V.; van Dijk, M.; Fransen, M.; van der Graaf, H.; Hartjes, F.; Hessey, N.; Koppert, W.; Nauta, S.; Rogers, M.; Romaniouk, A.; Veenhof, R.

2011-06-01

Gossip is a gaseous micro-pixel detector with a very thin drift gap intended for a high rate environment like at the pixel layers of ATLAS at the sLHC. The detector outputs not only the crossing point of a traversing MIP, but also the angle of the track, thus greatly simplifying track reconstruction. In this paper we describe a testbeam experiment to examine the angular resolution of the reconstructed track segments in Gossip. We used here the low diffusion gas mixture DME/CO 2 50/50. An angular resolution of 20 mrad for perpendicular tracks could be obtained from a 1.5 mm thin drift volume. However, for the prototype detector used at the testbeam experiment, the resolution of slanting tracks was worsened by poor time resolution of the pixel chip used.

Position and time resolution measurements with a microchannel plate image intensifier: A comparison of monolithic and pixelated CeBr3 scintillators

NASA Astrophysics Data System (ADS)

Ackermann, Ulrich; Eschbaumer, Stephan; Bergmaier, Andreas; Egger, Werner; Sperr, Peter; Greubel, Christoph; Löwe, Benjamin; Schotanus, Paul; Dollinger, Günther

2016-07-01

To perform Four Dimensional Age Momentum Correlation measurements in the near future, where one obtains the positron lifetime in coincidence with the three dimensional momentum of the electron annihilating with the positron, we have investigated the time and position resolution of two CeBr3 scintillators (monolithic and an array of pixels) using a Photek IPD340/Q/BI/RS microchannel plate image intensifier. The microchannel plate image intensifier has an active diameter of 40 mm and a stack of two microchannel plates in chevron configuration. The monolithic CeBr3 scintillator was cylindrically shaped with a diameter of 40 mm and a height of 5 mm. The pixelated scintillator array covered the whole active area of the microchannel plate image intensifier and the shape of each pixel was 2.5·2.5·8 mm3 with a pixel pitch of 3.3 mm. For the monolithic setup the measured mean single time resolution was 330 ps (FWHM) at a gamma energy of 511 keV. No significant dependence on the position was detected. The position resolution at the center of the monolithic scintillator was about 2.5 mm (FWHM) at a gamma energy of 662 keV. The single time resolution of the pixelated crystal setup reached 320 ps (FWHM) in the region of the center of the active area of the microchannel plate image intensifier. The position resolution was limited by the cross-section of the pixels. The gamma energy for the pixel setup measurements was 511 keV.

Integrated sensor with frame memory and programmable resolution for light adaptive imaging

NASA Technical Reports Server (NTRS)

Zhou, Zhimin (Inventor); Fossum, Eric R. (Inventor); Pain, Bedabrata (Inventor)

2004-01-01

An image sensor operable to vary the output spatial resolution according to a received light level while maintaining a desired signal-to-noise ratio. Signals from neighboring pixels in a pixel patch with an adjustable size are added to increase both the image brightness and signal-to-noise ratio. One embodiment comprises a sensor array for receiving input signals, a frame memory array for temporarily storing a full frame, and an array of self-calibration column integrators for uniform column-parallel signal summation. The column integrators are capable of substantially canceling fixed pattern noise.

3D detectors with high space and time resolution

NASA Astrophysics Data System (ADS)

Loi, A.

2018-01-01

For future high luminosity LHC experiments it will be important to develop new detector systems with increased space and time resolution and also better radiation hardness in order to operate in high luminosity environment. A possible technology which could give such performances is 3D silicon detectors. This work explores the possibility of a pixel geometry by designing and simulating different solutions, using Sentaurus Tecnology Computer Aided Design (TCAD) as design and simulation tool, and analysing their performances. A key factor during the selection was the generated electric field and the carrier velocity inside the active area of the pixel.

Design Studies of a CZT-based Detector Combined with a Pixel-Geometry-Matching Collimator for SPECT Imaging.

PubMed

Weng, Fenghua; Bagchi, Srijeeta; Huang, Qiu; Seo, Youngho

2013-10-01

Single Photon Emission Computed Tomography (SPECT) suffers limited efficiency due to the need for collimators. Collimator properties largely decide the data statistics and image quality. Various materials and configurations of collimators have been investigated in many years. The main thrust of our study is to evaluate the design of pixel-geometry-matching collimators to investigate their potential performances using Geant4 Monte Carlo simulations. Here, a pixel-geometry-matching collimator is defined as a collimator which is divided into the same number of pixels as the detector's and the center of each pixel in the collimator is a one-to-one correspondence to that in the detector. The detector is made of Cadmium Zinc Telluride (CZT), which is one of the most promising materials for applications to detect hard X-rays and γ -rays due to its ability to obtain good energy resolution and high light output at room temperature. For our current project, we have designed a large-area, CZT-based gamma camera (20.192 cm×20.192 cm) with a small pixel pitch (1.60 mm). The detector is pixelated and hence the intrinsic resolution can be as small as the size of the pixel. Materials of collimator, collimator hole geometry, detection efficiency, and spatial resolution of the CZT detector combined with the pixel-matching collimator were calculated and analyzed under different conditions. From the simulation studies, we found that such a camera using rectangular holes has promising imaging characteristics in terms of spatial resolution, detection efficiency, and energy resolution.

Using a pulsed laser beam to investigate the feasibility of sub-pixel position resolution with time-correlated transient signals in 3D pixelated CdZnTe detectors

DOE PAGES

Giraldo, L. Ocampo; Bolotnikov, A. E.; Camarda, G. S.; ...

2017-04-20

For this study, we evaluated the X-Y position resolution achievable in 3D pixelated detectors by processing the signal waveforms readout from neighboring pixels. In these measurements we used a focused light beam, down to 10 μm, generated by a ~1 mW pulsed laser (650 nm) to carry out raster scans over selected 3×3 pixel areas, while recording the charge signals from the 9 pixels and the cathode using two synchronized digital oscilloscopes.

Image acquisition system using on sensor compressed sampling technique

NASA Astrophysics Data System (ADS)

Gupta, Pravir Singh; Choi, Gwan Seong

2018-01-01

Advances in CMOS technology have made high-resolution image sensors possible. These image sensors pose significant challenges in terms of the amount of raw data generated, energy efficiency, and frame rate. This paper presents a design methodology for an imaging system and a simplified image sensor pixel design to be used in the system so that the compressed sensing (CS) technique can be implemented easily at the sensor level. This results in significant energy savings as it not only cuts the raw data rate but also reduces transistor count per pixel; decreases pixel size; increases fill factor; simplifies analog-to-digital converter, JPEG encoder, and JPEG decoder design; decreases wiring; and reduces the decoder size by half. Thus, CS has the potential to increase the resolution of image sensors for a given technology and die size while significantly decreasing the power consumption and design complexity. We show that it has potential to reduce power consumption by about 23% to 65%.

Sub-pixel mapping of hyperspectral imagery using super-resolution

NASA Astrophysics Data System (ADS)

Sharma, Shreya; Sharma, Shakti; Buddhiraju, Krishna M.

2016-04-01

With the development of remote sensing technologies, it has become possible to obtain an overview of landscape elements which helps in studying the changes on earth's surface due to climate, geological, geomorphological and human activities. Remote sensing measures the electromagnetic radiations from the earth's surface and match the spectral similarity between the observed signature and the known standard signatures of the various targets. However, problem lies when image classification techniques assume pixels to be pure. In hyperspectral imagery, images have high spectral resolution but poor spatial resolution. Therefore, the spectra obtained is often contaminated due to the presence of mixed pixels and causes misclassification. To utilise this high spectral information, spatial resolution has to be enhanced. Many factors make the spatial resolution one of the most expensive and hardest to improve in imaging systems. To solve this problem, post-processing of hyperspectral images is done to retrieve more information from the already acquired images. The algorithm to enhance spatial resolution of the images by dividing them into sub-pixels is known as super-resolution and several researches have been done in this domain.In this paper, we propose a new method for super-resolution based on ant colony optimization and review the popular methods of sub-pixel mapping of hyperspectral images along with their comparative analysis.

Advanced aerosense display interfaces

NASA Astrophysics Data System (ADS)

Hopper, Darrel G.; Meyer, Frederick M.

1998-09-01

High-resolution display technologies are being developed to meet the ever-increasing demand for realistic detail. The requirement for evermore visual information exceeds the capacity of fielded aerospace display interfaces. In this paper we begin an exploration of display interfaces and evolving aerospace requirements. Current and evolving standards for avionics, commercial, and flat panel displays are summarized and compared to near term goals for military and aerospace applications. Aerospace and military applications prior to 2005 up to UXGA and digital HDTV resolution can be met by using commercial interface standard developments. Advanced aerospace requirements require yet higher resolutions (2560 X 2048 color pixels, 5120 X 4096 color pixels at 85 Hz, etc.) and necessitate the initiation of discussion herein of an 'ultra digital interface standard (UDIS)' which includes 'smart interface' features such as large memory and blazingly fast resizing microcomputer. Interface capacity, IT, increased about 105 from 1973 to 1998; 102 more is needed for UDIS.

3D track reconstruction capability of a silicon hybrid active pixel detector

NASA Astrophysics Data System (ADS)

Bergmann, Benedikt; Pichotka, Martin; Pospisil, Stanislav; Vycpalek, Jiri; Burian, Petr; Broulim, Pavel; Jakubek, Jan

2017-06-01

Timepix3 detectors are the latest generation of hybrid active pixel detectors of the Medipix/Timepix family. Such detectors consist of an active sensor layer which is connected to the readout ASIC (application specific integrated circuit), segmenting the detector into a square matrix of 256 × 256 pixels (pixel pitch 55 μm). Particles interacting in the active sensor material create charge carriers, which drift towards the pixelated electrode, where they are collected. In each pixel, the time of the interaction (time resolution 1.56 ns) and the amount of created charge carriers are measured. Such a device was employed in an experiment in a 120 GeV/c pion beam. It is demonstrated, how the drift time information can be used for "4D" particle tracking, with the three spatial dimensions and the energy losses along the particle trajectory (dE/dx). Since the coordinates in the detector plane are given by the pixelation ( x, y), the x- and y-resolution is determined by the pixel pitch (55 μm). A z-resolution of 50.4 μm could be achieved (for a 500 μm thick silicon sensor at 130 V bias), whereby the drift time model independent z-resolution was found to be 28.5 μm.

Improving Science Communication with Responsive Web Design

NASA Astrophysics Data System (ADS)

Hilverda, M.

2013-12-01

Effective science communication requires clarity in both content and presentation. Content is increasingly being viewed via the Web across a broad range of devices, which can vary in screen size, resolution, and pixel density. Readers access the same content from desktop computers, tablets, smartphones, and wearable computing devices. Creating separate presentation formats optimized for each device is inefficient and unrealistic as new devices continually enter the marketplace. Responsive web design is an approach that puts content first within a presentation design that responds automatically to its environment. This allows for one platform to be maintained that can be used effectively for every screen. The layout adapts to screens of all sizes ensuring easy viewing of content for readers regardless of their device. Responsive design is accomplished primarily by the use of media queries within style sheets, which allows for changes to layout properties to be defined based on media types (i.e. screen, print) and resolution. Images and other types of multimedia can also be defined to scale automatically to fit different screen dimensions, although some media types require additional effort for proper implementation. Hardware changes, such as high pixel density screens, also present new challenges for effective presentation of content. High pixel density screens contain a greater number of pixels within a screen area increasing the pixels per inch (PPI) compared to standard screens. The result is increased clarity for text and vector media types, but often decreased clarity for standard resolution raster images. Media queries and other custom solutions can assist by specifying higher resolution images for high pixel density screens. Unfortunately, increasing image resolution results in significantly more data being transferred to the device. Web traffic on mobile devices such as smartphones and tablets is on a steady growth trajectory and many mobile devices around the world use low-bandwidth connections. Communicating science effectively includes efficient delivery of the information to the reader. To meet this criteria, responsive designs should also incorporate "mobile first" elements such as serving ideal image sizes (a low resolution cell phone does not need to receive a large desktop image) and a focus on fast, readable content delivery. The technical implementation of responsive web design is constantly changing as new web standards and approaches become available. However, fundamental design principles such as grid layouts, clear typography, and proper use of white space should be an important part of content delivery within any responsive design. This presentation will discuss current responsive design approaches for improving scientific communication across multiple devices, operating systems, and bandwidth capacities. The presentation will also include example responsive designs for scientific papers and websites. Implementing a responsive design approach with a focus on content and fundamental design principles is an important step to ensuring scientific information remains clear and accessible as screens and devices continue to evolve.

Photon-counting hexagonal pixel array CdTe detector: Spatial resolution characteristics for image-guided interventional applications

PubMed Central

Shrestha, Suman; Karellas, Andrew; Shi, Linxi; Gounis, Matthew J.; Bellazzini, Ronaldo; Spandre, Gloria; Brez, Alessandro; Minuti, Massimo

2016-01-01

Purpose: High-resolution, photon-counting, energy-resolved detector with fast-framing capability can facilitate simultaneous acquisition of precontrast and postcontrast images for subtraction angiography without pixel registration artifacts and can facilitate high-resolution real-time imaging during image-guided interventions. Hence, this study was conducted to determine the spatial resolution characteristics of a hexagonal pixel array photon-counting cadmium telluride (CdTe) detector. Methods: A 650 μm thick CdTe Schottky photon-counting detector capable of concurrently acquiring up to two energy-windowed images was operated in a single energy-window mode to include photons of 10 keV or higher. The detector had hexagonal pixels with apothem of 30 μm resulting in pixel pitch of 60 and 51.96 μm along the two orthogonal directions. The detector was characterized at IEC-RQA5 spectral conditions. Linear response of the detector was determined over the air kerma rate relevant to image-guided interventional procedures ranging from 1.3 nGy/frame to 91.4 μGy/frame. Presampled modulation transfer was determined using a tungsten edge test device. The edge-spread function and the finely sampled line spread function accounted for hexagonal sampling, from which the presampled modulation transfer function (MTF) was determined. Since detectors with hexagonal pixels require resampling to square pixels for distortion-free display, the optimal square pixel size was determined by minimizing the root-mean-squared-error of the aperture functions for the square and hexagonal pixels up to the Nyquist limit. Results: At Nyquist frequencies of 8.33 and 9.62 cycles/mm along the apothem and orthogonal to the apothem directions, the modulation factors were 0.397 and 0.228, respectively. For the corresponding axis, the limiting resolution defined as 10% MTF occurred at 13.3 and 12 cycles/mm, respectively. Evaluation of the aperture functions yielded an optimal square pixel size of 54 μm. After resampling to 54 μm square pixels using trilinear interpolation, the presampled MTF at Nyquist frequency of 9.26 cycles/mm was 0.29 and 0.24 along the orthogonal directions and the limiting resolution (10% MTF) occurred at approximately 12 cycles/mm. Visual analysis of a bar pattern image showed the ability to resolve close to 12 line-pairs/mm and qualitative evaluation of a neurovascular nitinol-stent showed the ability to visualize its struts at clinically relevant conditions. Conclusions: Hexagonal pixel array photon-counting CdTe detector provides high spatial resolution in single-photon counting mode. After resampling to optimal square pixel size for distortion-free display, the spatial resolution is preserved. The dual-energy capabilities of the detector could allow for artifact-free subtraction angiography and basis material decomposition. The proposed high-resolution photon-counting detector with energy-resolving capability can be of importance for several image-guided interventional procedures as well as for pediatric applications. PMID:27147324

Photon-counting hexagonal pixel array CdTe detector: Spatial resolution characteristics for image-guided interventional applications.

PubMed

Vedantham, Srinivasan; Shrestha, Suman; Karellas, Andrew; Shi, Linxi; Gounis, Matthew J; Bellazzini, Ronaldo; Spandre, Gloria; Brez, Alessandro; Minuti, Massimo

2016-05-01

High-resolution, photon-counting, energy-resolved detector with fast-framing capability can facilitate simultaneous acquisition of precontrast and postcontrast images for subtraction angiography without pixel registration artifacts and can facilitate high-resolution real-time imaging during image-guided interventions. Hence, this study was conducted to determine the spatial resolution characteristics of a hexagonal pixel array photon-counting cadmium telluride (CdTe) detector. A 650 μm thick CdTe Schottky photon-counting detector capable of concurrently acquiring up to two energy-windowed images was operated in a single energy-window mode to include photons of 10 keV or higher. The detector had hexagonal pixels with apothem of 30 μm resulting in pixel pitch of 60 and 51.96 μm along the two orthogonal directions. The detector was characterized at IEC-RQA5 spectral conditions. Linear response of the detector was determined over the air kerma rate relevant to image-guided interventional procedures ranging from 1.3 nGy/frame to 91.4 μGy/frame. Presampled modulation transfer was determined using a tungsten edge test device. The edge-spread function and the finely sampled line spread function accounted for hexagonal sampling, from which the presampled modulation transfer function (MTF) was determined. Since detectors with hexagonal pixels require resampling to square pixels for distortion-free display, the optimal square pixel size was determined by minimizing the root-mean-squared-error of the aperture functions for the square and hexagonal pixels up to the Nyquist limit. At Nyquist frequencies of 8.33 and 9.62 cycles/mm along the apothem and orthogonal to the apothem directions, the modulation factors were 0.397 and 0.228, respectively. For the corresponding axis, the limiting resolution defined as 10% MTF occurred at 13.3 and 12 cycles/mm, respectively. Evaluation of the aperture functions yielded an optimal square pixel size of 54 μm. After resampling to 54 μm square pixels using trilinear interpolation, the presampled MTF at Nyquist frequency of 9.26 cycles/mm was 0.29 and 0.24 along the orthogonal directions and the limiting resolution (10% MTF) occurred at approximately 12 cycles/mm. Visual analysis of a bar pattern image showed the ability to resolve close to 12 line-pairs/mm and qualitative evaluation of a neurovascular nitinol-stent showed the ability to visualize its struts at clinically relevant conditions. Hexagonal pixel array photon-counting CdTe detector provides high spatial resolution in single-photon counting mode. After resampling to optimal square pixel size for distortion-free display, the spatial resolution is preserved. The dual-energy capabilities of the detector could allow for artifact-free subtraction angiography and basis material decomposition. The proposed high-resolution photon-counting detector with energy-resolving capability can be of importance for several image-guided interventional procedures as well as for pediatric applications.

Subpixel resolution from multiple images

NASA Technical Reports Server (NTRS)

Cheeseman, Peter; Kanefsky, Rob; Stutz, John; Kraft, Richard

1994-01-01

Multiple images taken from similar locations and under similar lighting conditions contain similar, but not identical, information. Slight differences in instrument orientation and position produces mismatches between the projected pixel grids. These mismatches ensure that any point on the ground is sampled differently in each image. If all the images can be registered with respect to each other to a small fraction of a pixel accuracy, then the information from the multiple images can be combined to increase linear resolution by roughly the square root of the number of images. In addition, the gray-scale resolution of the composite image is also improved. We describe methods for multiple image registration and combination, and discuss some of the problems encountered in developing and extending them. We display test results with 8:1 resolution enhancement, and Viking Orbiter imagery with 2:1 and 4:1 enhancements.

Measurements with MÖNCH, a 25 μm pixel pitch hybrid pixel detector

NASA Astrophysics Data System (ADS)

Ramilli, M.; Bergamaschi, A.; Andrae, M.; Brückner, M.; Cartier, S.; Dinapoli, R.; Fröjdh, E.; Greiffenberg, D.; Hutwelker, T.; Lopez-Cuenca, C.; Mezza, D.; Mozzanica, A.; Ruat, M.; Redford, S.; Schmitt, B.; Shi, X.; Tinti, G.; Zhang, J.

2017-01-01

MÖNCH is a hybrid silicon pixel detector based on charge integration and with analog readout, featuring a pixel size of 25×25 μm2. The latest working prototype consists of an array of 400×400 identical pixels for a total active area of 1×1 cm2. Its design is optimized for the single photon regime. An exhaustive characterization of this large area prototype has been carried out in the past months, and it confirms an ENC in the order of 35 electrons RMS and a dynamic range of ~4×12 keV photons in high gain mode, which increases to ~100×12 keV photons with the lowest gain setting. The low noise levels of MÖNCH make it a suitable candidate for X-ray detection at energies around 1 keV and below. Imaging applications in particular can benefit significantly from the use of MÖNCH: due to its extremely small pixel pitch, the detector intrinsically offers excellent position resolution. Moreover, in low flux conditions, charge sharing between neighboring pixels allows the use of position interpolation algorithms which grant a resolution at the micrometer-level. Its energy reconstruction and imaging capabilities have been tested for the first time at a low energy beamline at PSI, with photon energies between 1.75 keV and 3.5 keV, and results will be shown.

Effects of Atmospheric Water Vapor and Clouds on NOAA (National Oceanic and Atmospheric Administration) AVHRR (Advanced Very High Resolution Radiometer) Satellite Data.

DTIC Science & Technology

1984-07-01

aerosols and sub pixel-sized clouds all tend to increase Channel 1 with respect to Channel 2 and reduce the computed VIN. Further, the Guide states that... computation of the VIN. Large scale cloud contamination of pixels, while diffi- cult to correct for, can at least be monitored and affected pixels...techniques have been developed for computer cloud screening. See, for example, Horvath et al. (1982), Gray and McCrary (1981a) and Nixon et al. (1983

Applications of Fractal Analytical Techniques in the Estimation of Operational Scale

NASA Technical Reports Server (NTRS)

Emerson, Charles W.; Quattrochi, Dale A.

2000-01-01

The observational scale and the resolution of remotely sensed imagery are essential considerations in the interpretation process. Many atmospheric, hydrologic, and other natural and human-influenced spatial phenomena are inherently scale dependent and are governed by different physical processes at different spatial domains. This spatial and operational heterogeneity constrains the ability to compare interpretations of phenomena and processes observed in higher spatial resolution imagery to similar interpretations obtained from lower resolution imagery. This is a particularly acute problem, since longterm global change investigations will require high spatial resolution Earth Observing System (EOS), Landsat 7, or commercial satellite data to be combined with lower resolution imagery from older sensors such as Landsat TM and MSS. Fractal analysis is a useful technique for identifying the effects of scale changes on remotely sensed imagery. The fractal dimension of an image is a non-integer value between two and three which indicates the degree of complexity in the texture and shapes depicted in the image. A true fractal surface exhibits self-similarity, a property of curves or surfaces where each part is indistinguishable from the whole, or where the form of the curve or surface is invariant with respect to scale. Theoretically, if the digital numbers of a remotely sensed image resemble an ideal fractal surface, then due to the self-similarity property, the fractal dimension of the image will not vary with scale and resolution, and the slope of the fractal dimension-resolution relationship would be zero. Most geographical phenomena, however, are not self-similar at all scales, but they can be modeled by a stochastic fractal in which the scaling properties of the image exhibit patterns that can be described by statistics such as area-perimeter ratios and autocovariances. Stochastic fractal sets relax the self-similarity assumption and measure many scales and resolutions to represent the varying form of a phenomenon as the pixel size is increased in a convolution process. We have observed that for images of homogeneous land covers, the fractal dimension varies linearly with changes in resolution or pixel size over the range of past, current, and planned space-borne sensors. This relationship differs significantly in images of agricultural, urban, and forest land covers, with urban areas retaining the same level of complexity, forested areas growing smoother, and agricultural areas growing more complex as small pixels are aggregated into larger, mixed pixels. Images of scenes having a mixture of land covers have fractal dimensions that exhibit a non-linear, complex relationship to pixel size. Measuring the fractal dimension of a difference image derived from two images of the same area obtained on different dates showed that the fractal dimension increased steadily, then exhibited a sharp decrease at increasing levels of pixel aggregation. This breakpoint of the fractal dimension/resolution plot is related to the spatial domain or operational scale of the phenomenon exhibiting the predominant visible difference between the two images (in this case, mountain snow cover). The degree to which an image departs from a theoretical ideal fractal surface provides clues as to how much information is altered or lost in the processes of rescaling and rectification. The measured fractal dimension of complex, composite land covers such as urban areas also provides a useful textural index that can assist image classification of complex scenes.

Assessment and Prediction of Natural Hazards from Satellite Imagery

PubMed Central

Gillespie, Thomas W.; Chu, Jasmine; Frankenberg, Elizabeth; Thomas, Duncan

2013-01-01

Since 2000, there have been a number of spaceborne satellites that have changed the way we assess and predict natural hazards. These satellites are able to quantify physical geographic phenomena associated with the movements of the earth’s surface (earthquakes, mass movements), water (floods, tsunamis, storms), and fire (wildfires). Most of these satellites contain active or passive sensors that can be utilized by the scientific community for the remote sensing of natural hazards over a number of spatial and temporal scales. The most useful satellite imagery for the assessment of earthquake damage comes from high-resolution (0.6 m to 1 m pixel size) passive sensors and moderate resolution active sensors that can quantify the vertical and horizontal movement of the earth’s surface. High-resolution passive sensors have been used to successfully assess flood damage while predictive maps of flood vulnerability areas are possible based on physical variables collected from passive and active sensors. Recent moderate resolution sensors are able to provide near real time data on fires and provide quantitative data used in fire behavior models. Limitations currently exist due to atmospheric interference, pixel resolution, and revisit times. However, a number of new microsatellites and constellations of satellites will be launched in the next five years that contain increased resolution (0.5 m to 1 m pixel resolution for active sensors) and revisit times (daily ≤ 2.5 m resolution images from passive sensors) that will significantly improve our ability to assess and predict natural hazards from space. PMID:25170186

Automatic segmentation of fluorescence lifetime microscopy images of cells using multiresolution community detection--a first study.

PubMed

Hu, D; Sarder, P; Ronhovde, P; Orthaus, S; Achilefu, S; Nussinov, Z

2014-01-01

Inspired by a multiresolution community detection based network segmentation method, we suggest an automatic method for segmenting fluorescence lifetime (FLT) imaging microscopy (FLIM) images of cells in a first pilot investigation on two selected images. The image processing problem is framed as identifying segments with respective average FLTs against the background in FLIM images. The proposed method segments a FLIM image for a given resolution of the network defined using image pixels as the nodes and similarity between the FLTs of the pixels as the edges. In the resulting segmentation, low network resolution leads to larger segments, and high network resolution leads to smaller segments. Furthermore, using the proposed method, the mean-square error in estimating the FLT segments in a FLIM image was found to consistently decrease with increasing resolution of the corresponding network. The multiresolution community detection method appeared to perform better than a popular spectral clustering-based method in performing FLIM image segmentation. At high resolution, the spectral segmentation method introduced noisy segments in its output, and it was unable to achieve a consistent decrease in mean-square error with increasing resolution. © 2013 The Authors Journal of Microscopy © 2013 Royal Microscopical Society.

Prevalence of pure versus mixed snow cover pixels across spatial resolutions in alpine environments: implications for binary and fractional remote sensing approaches

USGS Publications Warehouse

Selkowitz, David J.; Forster, Richard; Caldwell, Megan K.

2014-01-01

Remote sensing of snow-covered area (SCA) can be binary (indicating the presence/absence of snow cover at each pixel) or fractional (indicating the fraction of each pixel covered by snow). Fractional SCA mapping provides more information than binary SCA, but is more difficult to implement and may not be feasible with all types of remote sensing data. The utility of fractional SCA mapping relative to binary SCA mapping varies with the intended application as well as by spatial resolution, temporal resolution and period of interest, and climate. We quantified the frequency of occurrence of partially snow-covered (mixed) pixels at spatial resolutions between 1 m and 500 m over five dates at two study areas in the western U.S., using 0.5 m binary SCA maps derived from high spatial resolution imagery aggregated to fractional SCA at coarser spatial resolutions. In addition, we used in situ monitoring to estimate the frequency of partially snow-covered conditions for the period September 2013–August 2014 at 10 60-m grid cell footprints at two study areas with continental snow climates. Results from the image analysis indicate that at 40 m, slightly above the nominal spatial resolution of Landsat, mixed pixels accounted for 25%–93% of total pixels, while at 500 m, the nominal spatial resolution of MODIS bands used for snow cover mapping, mixed pixels accounted for 67%–100% of total pixels. Mixed pixels occurred more commonly at the continental snow climate site than at the maritime snow climate site. The in situ data indicate that some snow cover was present between 186 and 303 days, and partial snow cover conditions occurred on 10%–98% of days with snow cover. Four sites remained partially snow-free throughout most of the winter and spring, while six sites were entirely snow covered throughout most or all of the winter and spring. Within 60 m grid cells, the late spring/summer transition from snow-covered to snow-free conditions lasted 17–56 days and averaged 37 days. Our results suggest that mixed snow-covered snow-free pixels are common at the spatial resolutions imaged by both the Landsat and MODIS sensors. This highlights the additional information available from fractional SCA products and suggests fractional SCA can provide a major advantage for hydrological and climatological monitoring and modeling, particularly when accurate representation of the spatial distribution of snow cover is critical.

Super-Resolution Enhancement From Multiple Overlapping Images: A Fractional Area Technique

NASA Astrophysics Data System (ADS)

Michaels, Joshua A.

With the availability of large quantities of relatively low-resolution data from several decades of space borne imaging, methods of creating an accurate, higher-resolution image from the multiple lower-resolution images (i.e. super-resolution), have been developed almost since such imagery has been around. The fractional-area super-resolution technique developed in this thesis has never before been documented. Satellite orbits, like Landsat, have a quantifiable variation, which means each image is not centered on the exact same spot more than once and the overlapping information from these multiple images may be used for super-resolution enhancement. By splitting a single initial pixel into many smaller, desired pixels, a relationship can be created between them using the ratio of the area within the initial pixel. The ideal goal for this technique is to obtain smaller pixels with exact values and no error, yielding a better potential result than those methods that yield interpolated pixel values with consequential loss of spatial resolution. A Fortran 95 program was developed to perform all calculations associated with the fractional-area super-resolution technique. The fractional areas are calculated using traditional trigonometry and coordinate geometry and Linear Algebra Package (LAPACK; Anderson et al., 1999) is used to solve for the higher-resolution pixel values. In order to demonstrate proof-of-concept, a synthetic dataset was created using the intrinsic Fortran random number generator and Adobe Illustrator CS4 (for geometry). To test the real-life application, digital pictures from a Sony DSC-S600 digital point-and-shoot camera with a tripod were taken of a large US geological map under fluorescent lighting. While the fractional-area super-resolution technique works in perfect synthetic conditions, it did not successfully produce a reasonable or consistent solution in the digital photograph enhancement test. The prohibitive amount of processing time (up to 60 days for a relatively small enhancement area) severely limits the practical usefulness of fraction-area super-resolution. Fractional-area super-resolution is very sensitive to relative input image co-registration, which must be accurate to a sub-pixel degree. However, use of this technique, if input conditions permit, could be applied as a "pinpoint" super-resolution technique. Such an application could be possible by only applying it to only very small areas with very good input image co-registration.

The Effect Of Pixel Size On The Detection Rate Of Early Pulmonary Sarcoidosis In Digital Chest Radiographic Systems

NASA Astrophysics Data System (ADS)

MacMahon, Heber; Vyborny, Carl; Powell, Gregory; Doi, Kunio; Metz, Charles E.

1984-08-01

In digital radiography the pixel size used determines the potential spatial resolution of the system. The need for spatial resolution varies depending on the subject matter imaged. In many areas, including the chest, the minimum spatial resolution requirements have not been determined. Sarcoidosis is a disease which frequently causes subtle interstitial infiltrates in the lungs. As the initial step in an investigation designed to determine the minimum pixel size required in digital chest radiographic systems, we have studied 1 mm pixel digitized images on patients with early pulmonary sarcoidosis. The results of this preliminary study suggest that neither mild interstitial pulmonary infiltrates nor other abnormalities such as pneumothoraces may be detected reliably with 1 mm pixel digital images.

3-D Spatial Resolution of 350 μm Pitch Pixelated CdZnTe Detectors for Imaging Applications.

PubMed

Yin, Yongzhi; Chen, Ximeng; Wu, Heyu; Komarov, Sergey; Garson, Alfred; Li, Qiang; Guo, Qingzhen; Krawczynski, Henric; Meng, Ling-Jian; Tai, Yuan-Chuan

2013-02-01

We are currently investigating the feasibility of using highly pixelated Cadmium Zinc Telluride (CdZnTe) detectors for sub-500 μ m resolution PET imaging applications. A 20 mm × 20 mm × 5 mm CdZnTe substrate was fabricated with 350 μ m pitch pixels (250 μ m anode pixels with 100 μ m gap) and coplanar cathode. Charge sharing among the pixels of a 350 μ m pitch detector was studied using collimated 122 keV and 511 keV gamma ray sources. For a 350 μ m pitch CdZnTe detector, scatter plots of the charge signal of two neighboring pixels clearly show more charge sharing when the collimated beam hits the gap between adjacent pixels. Using collimated Co-57 and Ge-68 sources, we measured the count profiles and estimated the intrinsic spatial resolution of 350 μ m pitch detector biased at -1000 V. Depth of interaction was analyzed based on two methods, i.e., cathode/anode ratio and electron drift time, in both 122 keV and 511 keV measurements. For single-pixel photopeak events, a linear correlation between cathode/anode ratio and electron drift time was shown, which would be useful for estimating the DOI information and preserving image resolution in CdZnTe PET imaging applications.

3-D Spatial Resolution of 350 μm Pitch Pixelated CdZnTe Detectors for Imaging Applications

PubMed Central

Yin, Yongzhi; Chen, Ximeng; Wu, Heyu; Komarov, Sergey; Garson, Alfred; Li, Qiang; Guo, Qingzhen; Krawczynski, Henric; Meng, Ling-Jian; Tai, Yuan-Chuan

2016-01-01

We are currently investigating the feasibility of using highly pixelated Cadmium Zinc Telluride (CdZnTe) detectors for sub-500 μm resolution PET imaging applications. A 20 mm × 20 mm × 5 mm CdZnTe substrate was fabricated with 350 μm pitch pixels (250 μm anode pixels with 100 μm gap) and coplanar cathode. Charge sharing among the pixels of a 350 μm pitch detector was studied using collimated 122 keV and 511 keV gamma ray sources. For a 350 μm pitch CdZnTe detector, scatter plots of the charge signal of two neighboring pixels clearly show more charge sharing when the collimated beam hits the gap between adjacent pixels. Using collimated Co-57 and Ge-68 sources, we measured the count profiles and estimated the intrinsic spatial resolution of 350 μm pitch detector biased at −1000 V. Depth of interaction was analyzed based on two methods, i.e., cathode/anode ratio and electron drift time, in both 122 keV and 511 keV measurements. For single-pixel photopeak events, a linear correlation between cathode/anode ratio and electron drift time was shown, which would be useful for estimating the DOI information and preserving image resolution in CdZnTe PET imaging applications. PMID:28250476

A Phenology-based Method For Identifying the Planting Fraction of Winter Wheat Using Moderate-resolution Satellite Data

NASA Astrophysics Data System (ADS)

Dong, J.; Liu, W.; Han, W.; Lei, T.; Xia, J.; Yuan, W.

2017-12-01

Winter wheat is a staple food crop for most of the world's population, and the area and spatial distribution of winter wheat are key elements in estimating crop production and ensuring food security. However, winter wheat planting areas contain substantial spatial heterogeneity with mixed pixels for coarse- and moderate-resolution satellite data, leading to significant errors in crop acreage estimation. This study has developed a phenology-based approach using moderate-resolution satellite data to estimate sub-pixel planting fractions of winter wheat. Based on unmanned aerial vehicle (UAV) observations, the unique characteristics of winter wheat with high vegetation index values at the heading stage (May) and low values at the harvest stage (June) were investigated. The differences in vegetation index between heading and harvest stages increased with the planting fraction of winter wheat, and therefore the planting fractions were estimated by comparing the NDVI differences of a given pixel with those of predetermined pure winter wheat and non-winter wheat pixels. This approach was evaluated using aerial images and agricultural statistical data in an intensive agricultural region, Shandong Province in North China. The method explained 60% and 85% of the spatial variation in county- and municipal-level statistical data, respectively. More importantly, the predetermined pure winter wheat and non-winter wheat pixels can be automatically identified using MODIS data according to their NDVI differences, which strengthens the potential to use this method at regional and global scales without any field observations as references.

Advanced SLMs for microscopy

NASA Astrophysics Data System (ADS)

Linnenberger, A.

2018-02-01

Wavefront shaping devices such as deformable mirrors, liquid crystal spatial light modulators (SLMs), and active lenses are of considerable interest in microscopy for aberration correction, volumetric imaging, and programmable excitation. Liquid crystal SLMs are high resolution phase modulators capable of creating complex phase profiles to reshape, or redirect light within a three-dimensional (3D) volume. Recent advances in Meadowlark Optics (MLO) SLMs reduce losses by increasing fill factor from 83.4% to 96%, and improving resolution from 512 x 512 pixels to 1920 x 1152 pixels while maintaining a liquid crystal response time of 300 Hz at 1064 nm. This paper summarizes new SLM capabilities, and benefits for microscopy.

Land cover mapping at sub-pixel scales

NASA Astrophysics Data System (ADS)

Makido, Yasuyo Kato

One of the biggest drawbacks of land cover mapping from remotely sensed images relates to spatial resolution, which determines the level of spatial details depicted in an image. Fine spatial resolution images from satellite sensors such as IKONOS and QuickBird are now available. However, these images are not suitable for large-area studies, since a single image is very small and therefore it is costly for large area studies. Much research has focused on attempting to extract land cover types at sub-pixel scale, and little research has been conducted concerning the spatial allocation of land cover types within a pixel. This study is devoted to the development of new algorithms for predicting land cover distribution using remote sensory imagery at sub-pixel level. The "pixel-swapping" optimization algorithm, which was proposed by Atkinson for predicting sub-pixel land cover distribution, is investigated in this study. Two limitations of this method, the arbitrary spatial range value and the arbitrary exponential model of spatial autocorrelation, are assessed. Various weighting functions, as alternatives to the exponential model, are evaluated in order to derive the optimum weighting function. Two different simulation models were employed to develop spatially autocorrelated binary class maps. In all tested models, Gaussian, Exponential, and IDW, the pixel swapping method improved classification accuracy compared with the initial random allocation of sub-pixels. However the results suggested that equal weight could be used to increase accuracy and sub-pixel spatial autocorrelation instead of using these more complex models of spatial structure. New algorithms for modeling the spatial distribution of multiple land cover classes at sub-pixel scales are developed and evaluated. Three methods are examined: sequential categorical swapping, simultaneous categorical swapping, and simulated annealing. These three methods are applied to classified Landsat ETM+ data that has been resampled to 210 meters. The result suggested that the simultaneous method can be considered as the optimum method in terms of accuracy performance and computation time. The case study employs remote sensing imagery at the following sites: tropical forests in Brazil and temperate multiple land mosaic in East China. Sub-areas for both sites are used to examine how the characteristics of the landscape affect the ability of the optimum technique. Three types of measurement: Moran's I, mean patch size (MPS), and patch size standard deviation (STDEV), are used to characterize the landscape. All results suggested that this technique could increase the classification accuracy more than traditional hard classification. The methods developed in this study can benefit researchers who employ coarse remote sensing imagery but are interested in detailed landscape information. In many cases, the satellite sensor that provides large spatial coverage has insufficient spatial detail to identify landscape patterns. Application of the super-resolution technique described in this dissertation could potentially solve this problem by providing detailed land cover predictions from the coarse resolution satellite sensor imagery.

Influence of detector pixel size, TOF resolution and DOI on image quality in MR-compatible whole-body PET.

PubMed

Thoen, Hendrik; Keereman, Vincent; Mollet, Pieter; Van Holen, Roel; Vandenberghe, Stefaan

2013-09-21

The optimization of a whole-body PET system remains a challenging task, as the imaging performance is influenced by a complex interaction of different design parameters. However, it is not always clear which parameters have the largest impact on image quality and are most eligible for optimization. To determine this, we need to be able to assess their influence on image quality. We performed Monte-Carlo simulations of a whole-body PET scanner to predict the influence on image quality of three detector parameters: the TOF resolution, the transverse pixel size and depth-of-interaction (DOI)-correction. The inner diameter of the PET scanner was 65 cm, small enough to allow physical integration into a simultaneous PET-MR system. Point sources were used to evaluate the influence of transverse pixel size and DOI-correction on spatial resolution as function of radial distance. To evaluate the influence on contrast recovery and pixel noise a cylindrical phantom of 35 cm diameter was used, representing a large patient. The phantom contained multiple hot lesions with 5 mm diameter. These lesions were placed at radial distances of 50, 100 and 150 mm from the center of the field-of-view, to be able to study the effects at different radial positions. The non-prewhitening (NPW) observer was used for objective analysis of the detectability of the hot lesions in the cylindrical phantom. Based on this analysis the NPW-SNR was used to quantify the relative improvements in image quality due to changes of the variable detector parameters. The image quality of a whole-body PET scanner can be improved significantly by reducing the transverse pixel size from 4 to 2.6 mm and improving the TOF resolution from 600 to 400 ps and further from 400 to 200 ps. Compared to pixel size, the TOF resolution has the larger potential to increase image quality for the simulated phantom. The introduction of two layer DOI-correction only leads to a modest improvement for the spheres at radial distance of 150 mm from the center of the transaxial FOV.

Imaging During MESSENGER's Second Flyby of Mercury

NASA Astrophysics Data System (ADS)

Chabot, N. L.; Prockter, L. M.; Murchie, S. L.; Robinson, M. S.; Laslo, N. R.; Kang, H. K.; Hawkins, S. E.; Vaughan, R. M.; Head, J. W.; Solomon, S. C.; MESSENGER Team

2008-12-01

During MESSENGER's second flyby of Mercury on October 6, 2008, the Mercury Dual Imaging System (MDIS) will acquire 1287 images. The images will include coverage of about 30% of Mercury's surface not previously seen by spacecraft. A portion of the newly imaged terrain will be viewed during the inbound portion of the flyby. On the outbound leg, MDIS will image additional previously unseen terrain as well as regions imaged under different illumination geometry by Mariner 10. These new images, when combined with images from Mariner 10 and from MESSENGER's first Mercury flyby, will enable the first regional- resolution global view of Mercury constituting a combined total coverage of about 96% of the planet's surface. MDIS consists of both a Wide Angle Camera (WAC) and a Narrow Angle Camera (NAC). During MESSENGER's second Mercury flyby, the following imaging activities are planned: about 86 minutes before the spacecraft's closest pass by the planet, the WAC will acquire images through 11 different narrow-band color filters of the approaching crescent planet at a resolution of about 5 km/pixel. At slightly less than 1 hour to closest approach, the NAC will acquire a 4-column x 11-row mosaic with an approximate resolution of 450 m/pixel. At 8 minutes after closest approach, the WAC will obtain the highest-resolution multispectral images to date of Mercury's surface, imaging a portion of the surface through 11 color filters at resolutions of about 250-600 m/pixel. A strip of high-resolution NAC images, with a resolution of approximately 100 m/pixel, will follow these WAC observations. The NAC will next acquire a 15-column x 13- row high-resolution mosaic of the northern hemisphere of the departing planet, beginning approximately 21 minutes after closest approach, with resolutions of 140-300 m/pixel; this mosaic will fill a large gore in the Mariner 10 data. At about 42 minutes following closest approach, the WAC will acquire a 3x3, 11-filter, full- planet mosaic with an average resolution of 2.5 km/pixel. Two NAC mosaics of the entire departing planet will be acquired beginning about 66 minutes after closest approach, with resolutions of 500-700 m/pixel. About 89 minutes following closest approach, the WAC will acquire a multispectral image set with a resolution of about 5 km/pixel. Following this WAC image set, MDIS will continue to acquire occasional images with both the WAC and NAC until 20 hours after closest approach, at which time the flyby data will begin being transmitted to Earth.

Architecture and applications of a high resolution gated SPAD image sensor

PubMed Central

Burri, Samuel; Maruyama, Yuki; Michalet, Xavier; Regazzoni, Francesco; Bruschini, Claudio; Charbon, Edoardo

2014-01-01

We present the architecture and three applications of the largest resolution image sensor based on single-photon avalanche diodes (SPADs) published to date. The sensor, fabricated in a high-voltage CMOS process, has a resolution of 512 × 128 pixels and a pitch of 24 μm. The fill-factor of 5% can be increased to 30% with the use of microlenses. For precise control of the exposure and for time-resolved imaging, we use fast global gating signals to define exposure windows as small as 4 ns. The uniformity of the gate edges location is ∼140 ps (FWHM) over the whole array, while in-pixel digital counting enables frame rates as high as 156 kfps. Currently, our camera is used as a highly sensitive sensor with high temporal resolution, for applications ranging from fluorescence lifetime measurements to fluorescence correlation spectroscopy and generation of true random numbers. PMID:25090572

Full complex spatial filtering with a phase mostly DMD. [Deformable Mirror Device

NASA Technical Reports Server (NTRS)

Florence, James M.; Juday, Richard D.

1991-01-01

A new technique for implementing fully complex spatial filters with a phase mostly deformable mirror device (DMD) light modulator is described. The technique combines two or more phase-modulating flexure-beam mirror elements into a single macro-pixel. By manipulating the relative phases of the individual sub-pixels within the macro-pixel, the amplitude and the phase can be independently set for this filtering element. The combination of DMD sub-pixels into a macro-pixel is accomplished by adjusting the optical system resolution, thereby trading off system space bandwidth product for increased filtering flexibility. Volume in the larger dimensioned space, space bandwidth-complex axes count, is conserved. Experimental results are presented mapping out the coupled amplitude and phase characteristics of the individual flexure-beam DMD elements and demonstrating the independent control of amplitude and phase in a combined macro-pixel. This technique is generally applicable for implementation with any type of phase modulating light modulator.

Reduced-Scale Transition-Edge Sensor Detectors for Solar and X-Ray Astrophysics

NASA Technical Reports Server (NTRS)

Datesman, Aaron M.; Adams, Joseph S.; Bandler, Simon R.; Betancourt-Martinez, Gabriele L.; Chang, Meng-Ping; Chervenak, James A.; Eckart, Megan E.; Ewin, Audrey E.; Finkbeiner, Fred M.; Ha, Jong Yoon;

Carotid Stenosis And Ulcer Detectability As A Function Of Pixel Size

NASA Astrophysics Data System (ADS)

Mintz, Leslie J.; Enzmann, Dieter R.; Keyes, Gary S.; Mainiero, Louis M.; Brody, William R.

1981-11-01

Digital radiography, in conjunction with digital subtraction methods can provide high quality images of the vascular system,1-4 Spatial resolution is one important limiting factor of this imaging technique. Since spatial resolution of a digital image is a function of pixel size, it is important to determine the pixel size threshold necessary to provide information comparable to that of conventional angiograms. This study was designed to establish the pixel size necessary to identify accurately stenotic and ulcerative lesions of the carotid artery.

a Spiral-Based Downscaling Method for Generating 30 M Time Series Image Data

NASA Astrophysics Data System (ADS)

Liu, B.; Chen, J.; Xing, H.; Wu, H.; Zhang, J.

2017-09-01

The spatial detail and updating frequency of land cover data are important factors influencing land surface dynamic monitoring applications in high spatial resolution scale. However, the fragmentized patches and seasonal variable of some land cover types (e. g. small crop field, wetland) make it labor-intensive and difficult in the generation of land cover data. Utilizing the high spatial resolution multi-temporal image data is a possible solution. Unfortunately, the spatial and temporal resolution of available remote sensing data like Landsat or MODIS datasets can hardly satisfy the minimum mapping unit and frequency of current land cover mapping / updating at the same time. The generation of high resolution time series may be a compromise to cover the shortage in land cover updating process. One of popular way is to downscale multi-temporal MODIS data with other high spatial resolution auxiliary data like Landsat. But the usual manner of downscaling pixel based on a window may lead to the underdetermined problem in heterogeneous area, result in the uncertainty of some high spatial resolution pixels. Therefore, the downscaled multi-temporal data can hardly reach high spatial resolution as Landsat data. A spiral based method was introduced to downscale low spatial and high temporal resolution image data to high spatial and high temporal resolution image data. By the way of searching the similar pixels around the adjacent region based on the spiral, the pixel set was made up in the adjacent region pixel by pixel. The underdetermined problem is prevented to a large extent from solving the linear system when adopting the pixel set constructed. With the help of ordinary least squares, the method inverted the endmember values of linear system. The high spatial resolution image was reconstructed on the basis of high spatial resolution class map and the endmember values band by band. Then, the high spatial resolution time series was formed with these high spatial resolution images image by image. Simulated experiment and remote sensing image downscaling experiment were conducted. In simulated experiment, the 30 meters class map dataset Globeland30 was adopted to investigate the effect on avoid the underdetermined problem in downscaling procedure and a comparison between spiral and window was conducted. Further, the MODIS NDVI and Landsat image data was adopted to generate the 30m time series NDVI in remote sensing image downscaling experiment. Simulated experiment results showed that the proposed method had a robust performance in downscaling pixel in heterogeneous region and indicated that it was superior to the traditional window-based methods. The high resolution time series generated may be a benefit to the mapping and updating of land cover data.

Tracking performance of a single-crystal and a polycrystalline diamond pixel-detector

DOE Office of Scientific and Technical Information (OSTI.GOV)

Menasce, D.; et al.

2013-06-01

We present a comparative characterization of the performance of a single-crystal and a polycrystalline diamond pixel-detector employing the standard CMS pixel readout chips. Measurements were carried out at the Fermilab Test Beam Facility, FTBF, using protons of momentum 120 GeV/c tracked by a high-resolution pixel telescope. Particular attention was directed to the study of the charge-collection, the charge-sharing among adjacent pixels and the achievable position resolution. The performance of the single-crystal detector was excellent and comparable to the best available silicon pixel-detectors. The measured average detection-efficiency was near unity, ε = 0.99860±0.00006, and the position-resolution for shared hits was aboutmore » 6 μm. On the other hand, the performance of the polycrystalline detector was hampered by its lower charge collection distance and the readout chip threshold. A new readout chip, capable of operating at much lower threshold (around 1 ke $-$), would be required to fully exploit the potential performance of the polycrystalline diamond pixel-detector.« less

Use of high-granularity CdZnTe pixelated detectors to correct response non-uniformities caused by defects in crystals

DOE PAGES

Bolotnikov, A. E.; Camarda, G. S.; Cui, Y.; ...

2015-09-06

Following our successful demonstration of the position-sensitive virtual Frisch-grid detectors, we investigated the feasibility of using high-granularity position sensing to correct response non-uniformities caused by the crystal defects in CdZnTe (CZT) pixelated detectors. The development of high-granularity detectors able to correct response non-uniformities on a scale comparable to the size of electron clouds opens the opportunity of using unselected off-the-shelf CZT material, whilst still assuring high spectral resolution for the majority of the detectors fabricated from an ingot. Here, we present the results from testing 3D position-sensitive 15×15×10 mm 3 pixelated detectors, fabricated with conventional pixel patterns with progressively smallermore » pixel sizes: 1.4, 0.8, and 0.5 mm. We employed the readout system based on the H3D front-end multi-channel ASIC developed by BNL's Instrumentation Division in collaboration with the University of Michigan. We use the sharing of electron clouds among several adjacent pixels to measure locations of interaction points with sub-pixel resolution. By using the detectors with small-pixel sizes and a high probability of the charge-sharing events, we were able to improve their spectral resolutions in comparison to the baseline levels, measured for the 1.4-mm pixel size detectors with small fractions of charge-sharing events. These results demonstrate that further enhancement of the performance of CZT pixelated detectors and reduction of costs are possible by using high spatial-resolution position information of interaction points to correct the small-scale response non-uniformities caused by crystal defects present in most devices.« less

Building Change Detection in Very High Resolution Satellite Stereo Image Time Series

NASA Astrophysics Data System (ADS)

Tian, J.; Qin, R.; Cerra, D.; Reinartz, P.

2016-06-01

There is an increasing demand for robust methods on urban sprawl monitoring. The steadily increasing number of high resolution and multi-view sensors allows producing datasets with high temporal and spatial resolution; however, less effort has been dedicated to employ very high resolution (VHR) satellite image time series (SITS) to monitor the changes in buildings with higher accuracy. In addition, these VHR data are often acquired from different sensors. The objective of this research is to propose a robust time-series data analysis method for VHR stereo imagery. Firstly, the spatial-temporal information of the stereo imagery and the Digital Surface Models (DSMs) generated from them are combined, and building probability maps (BPM) are calculated for all acquisition dates. In the second step, an object-based change analysis is performed based on the derivative features of the BPM sets. The change consistence between object-level and pixel-level are checked to remove any outlier pixels. Results are assessed on six pairs of VHR satellite images acquired within a time span of 7 years. The evaluation results have proved the efficiency of the proposed method.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bolotnikov, A. E.; Camarda, G. S.; Cui, Y.

Following our successful demonstration of the position-sensitive virtual Frisch-grid detectors, we investigated the feasibility of using high-granularity position sensing to correct response non-uniformities caused by the crystal defects in CdZnTe (CZT) pixelated detectors. The development of high-granularity detectors able to correct response non-uniformities on a scale comparable to the size of electron clouds opens the opportunity of using unselected off-the-shelf CZT material, whilst still assuring high spectral resolution for the majority of the detectors fabricated from an ingot. Here, we present the results from testing 3D position-sensitive 15×15×10 mm 3 pixelated detectors, fabricated with conventional pixel patterns with progressively smallermore » pixel sizes: 1.4, 0.8, and 0.5 mm. We employed the readout system based on the H3D front-end multi-channel ASIC developed by BNL's Instrumentation Division in collaboration with the University of Michigan. We use the sharing of electron clouds among several adjacent pixels to measure locations of interaction points with sub-pixel resolution. By using the detectors with small-pixel sizes and a high probability of the charge-sharing events, we were able to improve their spectral resolutions in comparison to the baseline levels, measured for the 1.4-mm pixel size detectors with small fractions of charge-sharing events. These results demonstrate that further enhancement of the performance of CZT pixelated detectors and reduction of costs are possible by using high spatial-resolution position information of interaction points to correct the small-scale response non-uniformities caused by crystal defects present in most devices.« less

The pixel tracking telescope at the Fermilab Test Beam Facility

DOE PAGES

Kwan, Simon; Lei, CM; Menasce, Dario; ...

2016-03-01

An all silicon pixel telescope has been assembled and used at the Fermilab Test Beam Facility (FTBF) since 2009 to provide precise tracking information for different test beam experiments with a wide range of Detectors Under Test (DUTs) requiring high resolution measurement of the track impact point. The telescope is based on CMS pixel modules left over from the CMS forward pixel production. Eight planes are arranged to achieve a resolution of less than 8 μm on the 120 GeV proton beam transverse coordinate at the DUT position. In order to achieve such resolution with 100 × 150 μm 2more » pixel cells, the planes were tilted to 25 degrees to maximize charge sharing between pixels. Crucial for obtaining this performance is the alignment software, called Monicelli, specifically designed and optimized for this system. This paper will describe the telescope hardware, the data acquisition system and the alignment software constituting this particle tracking system for test beam users.« less

First images of a digital autoradiography system based on a Medipix2 hybrid silicon pixel detector.

PubMed

Mettivier, Giovanni; Montesi, Maria Cristina; Russo, Paolo

2003-06-21

We present the first images of beta autoradiography obtained with the high-resolution hybrid pixel detector consisting of the Medipix2 single photon counting read-out chip bump-bonded to a 300 microm thick silicon pixel detector. This room temperature system has 256 x 256 square pixels of 55 microm pitch (total sensitive area of 14 x 14 mm2), with a double threshold discriminator and a 13-bit counter in each pixel. It is read out via a dedicated electronic interface and control software, also developed in the framework of the European Medipix2 Collaboration. Digital beta autoradiograms of 14C microscale standard strips (containing separate bands of increasing specific activity in the range 0.0038-32.9 kBq g(-1)) indicate system linearity down to a total background noise of 1.8 x 10(-3) counts mm(-2) s(-1). The minimum detectable activity is estimated to be 0.012 Bq for 36,000 s exposure and 0.023 Bq for 10,800 s exposure. The measured minimum detection threshold is less than 1600 electrons (equivalent to about 6 keV Si). This real-time system for beta autoradiography offers lower pixel pitch and higher sensitive area than the previous Medipix1-based system. It has a 14C sensitivity better than that of micro channel plate based systems, which, however, shows higher spatial resolution and sensitive area.

Hyperspectral image denoising and anomaly detection based on low-rank and sparse representations

NASA Astrophysics Data System (ADS)

Zhuang, Lina; Gao, Lianru; Zhang, Bing; Bioucas-Dias, José M.

2017-10-01

The very high spectral resolution of Hyperspectral Images (HSIs) enables the identification of materials with subtle differences and the extraction subpixel information. However, the increasing of spectral resolution often implies an increasing in the noise linked with the image formation process. This degradation mechanism limits the quality of extracted information and its potential applications. Since HSIs represent natural scenes and their spectral channels are highly correlated, they are characterized by a high level of self-similarity and are well approximated by low-rank representations. These characteristic underlies the state-of-the-art in HSI denoising. However, in presence of rare pixels, the denoising performance of those methods is not optimal and, in addition, it may compromise the future detection of those pixels. To address these hurdles, we introduce RhyDe (Robust hyperspectral Denoising), a powerful HSI denoiser, which implements explicit low-rank representation, promotes self-similarity, and, by using a form of collaborative sparsity, preserves rare pixels. The denoising and detection effectiveness of the proposed robust HSI denoiser is illustrated using semi-real data.

Pixel-super-resolved lensfree holography using adaptive relaxation factor and positional error correction

NASA Astrophysics Data System (ADS)

Zhang, Jialin; Chen, Qian; Sun, Jiasong; Li, Jiaji; Zuo, Chao

2018-01-01

Lensfree holography provides a new way to effectively bypass the intrinsical trade-off between the spatial resolution and field-of-view (FOV) of conventional lens-based microscopes. Unfortunately, due to the limited sensor pixel-size, unpredictable disturbance during image acquisition, and sub-optimum solution to the phase retrieval problem, typical lensfree microscopes only produce compromised imaging quality in terms of lateral resolution and signal-to-noise ratio (SNR). In this paper, we propose an adaptive pixel-super-resolved lensfree imaging (APLI) method to address the pixel aliasing problem by Z-scanning only, without resorting to subpixel shifting or beam-angle manipulation. Furthermore, an automatic positional error correction algorithm and adaptive relaxation strategy are introduced to enhance the robustness and SNR of reconstruction significantly. Based on APLI, we perform full-FOV reconstruction of a USAF resolution target across a wide imaging area of {29.85 mm2 and achieve half-pitch lateral resolution of 770 nm, surpassing 2.17 times of the theoretical Nyquist-Shannon sampling resolution limit imposed by the sensor pixel-size (1.67 μm). Full-FOV imaging result of a typical dicot root is also provided to demonstrate its promising potential applications in biologic imaging.

Recent advances in time series InSAR

NASA Astrophysics Data System (ADS)

Hooper, Andrew; Bekaert, David; Spaans, Karsten

2010-05-01

Despite the multiple successes of InSAR at measuring surface displacement, in many instances the signal over much of an image either decorrelates too quickly to be useful or is swamped by atmospheric noise. Time series InSAR methods seek to address these issues by essentially increasing the signal-to-noise ratio (SNR) through the use of more data. These techniques are particularly useful for applications where the strain rates detected at the surface are low, such as postseismic/interseismic motion, magma/fluid movement, landslides and reservoir exploitation. Our previous developments in this field have included a persistent scatterer algorithm based on spatial correlation, a full resolution small baseline approach based on the same strategy, and procedure for combining the two [Hooper, GRL, 2008]. This combined method works well on small areas (up to one frame) at ERS or Envisat strip-map resolution. However, in applying it to larger areas, such as the Guerrero region of Mexico and western Anatolia in Turkey, or when processing data at higher resolution, e.g. from TerraSAR-X, computer resource problems can arise. We have therefore altered the processing strategy to involve smarter use of computer memory. Further improvement is achieved by the resampling of the selected pixels (whether persistent scatterers or distributed scatterers) to a coarser resolution - usually we do not require a resolution on the scale of individual resolution cells for geophysical applications. Aliasing is avoided by summing the phase of nearby selected pixels, weighted according to their estimated SNR. This is akin to smart multilooking, but note that better results can be achieved than by starting the analysis with low-resolution (multilooked) data. Another development concerns selecting pixels only in images where they appear reliable. This allows for resolution cells that become correlated/decorrelated either in a temporary fashion, e.g., due to snow cover, or in a permanent way due to the appearance or removal of scatterers. The detection algorithm relies on the degree of spatial correlation for the pixel of interest in each image. We have also modified our 3-D phase-unwrapping algorithms to allow for the resulting differing combinations of coherent pixels in every interferogram. We demonstrate our improved techniques on volcanoes in Iceland and the 2006 slow-slip event in Guerrero, Mexico.

Effect of DEM resolution and comparison between different weighting factors for hydrologic connectivity index

NASA Astrophysics Data System (ADS)

Cantreul, Vincent; Cavalli, Marco; Degré, Aurore

2016-04-01

The emerging concept of hydrological connectivity is difficult to quantify. Some indices have been proposed. The most cited is Borselli's one. It mainly uses the DEM as input. The pixel size may strongly impacts the result of the calculation. It has not been studied yet in silty areas. Another important aspect is the choice of the weighting factor which strongly influences the index value. The objective of this poster is so to compare 8 different DEM's resolutions (12, 24, 48, 72, 96, 204, 504 and 996cm) and 3 different weighting factors (factor C of Wischmeier, Manning's factor and rugosity index) in the Borselli's index calculation. The IC was calculated in a 124ha catchment (Hevillers), in the loess belt, in Belgium. The DEM used is coming from a UAV with a maximum resolution of 12 cm. Permanent covered surfaces are not considered in order to avoid artefact due to the vegetation (2% of the surface). Regarding the DEM pixel size, the IC increases for a given pixel when the pixel size decreases. That confirms some results observed in the Alpine region by Cavalli (2014). The mean difference between 12 cm and 10 m resolution is 35% with higher values up to 100% for higher connectivity zones (flow paths). Another result is the lower impact of connections in the watershed (grass strips…) at lower pixel sizes. This is linked to the small width of some connections which are sometimes comparing to cell size. Furthermore, a great loss of precision is observed from the 500 cm pixel size and upper. That remark is quite intuitive. Finally, some very well disconnected zones appear for the highest resolutions. Regarding the weighting factor, IC values calculated using C factor are lower than with the rugosity index which is only a topographic factor. With very high resolution DEM, it permits to represent the fine topography. For the C factor, the zones up to very well disconnected areas (grass strips, wood…) are well represented with lower index values than downstream zones. On the contrary, areas up to very well connected zones (roads, paths…) are higher and much more connected than downstream areas. For the Manning's factor, the values are very low and not very well contrasted. This factor is not enough discriminant for this study. In conclusion, high resolution DEM (1 meter or higher) is needed for the IC calculation (precison, impact of connections…). Very high resolution permits to identify very well disconnected areas but it multiplies the calculation time. For the weighting factor, rugosity index and C factor have each some advantages. It is planned to test other approaches for the IC calculation. Key-words: hydrological connectivity index, DEM, resolution, weighting factor, comparison

Development and characterization of high-resolution neutron pixel detectors based on Timepix read-out chips

NASA Astrophysics Data System (ADS)

Krejci, F.; Zemlicka, J.; Jakubek, J.; Dudak, J.; Vavrik, D.; Köster, U.; Atkins, D.; Kaestner, A.; Soltes, J.; Viererbl, L.; Vacik, J.; Tomandl, I.

2016-12-01

Using a suitable isotope such as 6Li and 10B semiconductor hybrid pixel detectors can be successfully adapted for position sensitive detection of thermal and cold neutrons via conversion into energetic light ions. The adapted devices then typically provides spatial resolution at the level comparable to the pixel pitch (55 μm) and sensitive area of about few cm2. In this contribution, we describe further progress in neutron imaging performance based on the development of a large-area hybrid pixel detector providing practically continuous neutron sensitive area of 71 × 57 mm2. The measurements characterising the detector performance at the cold neutron imaging instrument ICON at PSI and high-flux imaging beam-line Neutrograph at ILL are presented. At both facilities, high-resolution high-contrast neutron radiography with the newly developed detector has been successfully applied for objects which imaging were previously difficult with hybrid pixel technology (such as various composite materials, objects of cultural heritage etc.). Further, a significant improvement in the spatial resolution of neutron radiography with hybrid semiconductor pixel detector based on the fast read-out Timepix-based detector is presented. The system is equipped with a thin planar 6LiF convertor operated effectively in the event-by-event mode enabling position sensitive detection with spatial resolution better than 10 μm.

Optical frequency comb profilometry using a single-pixel camera composed of digital micromirror devices.

PubMed

Pham, Quang Duc; Hayasaki, Yoshio

2015-01-01

We demonstrate an optical frequency comb profilometer with a single-pixel camera to measure the position and profile of an object's surface that exceeds far beyond light wavelength without 2π phase ambiguity. The present configuration of the single-pixel camera can perform the profilometry with an axial resolution of 3.4 μm at 1 GHz operation corresponding to a wavelength of 30 cm. Therefore, the axial dynamic range was increased to 0.87×10⁵. It was found from the experiments and computer simulations that the improvement was derived from higher modulation contrast of digital micromirror devices. The frame rate was also increased to 20 Hz.

Design and Optimization of Multi-Pixel Transition-Edge Sensors for X-Ray Astronomy Applications

NASA Technical Reports Server (NTRS)

Smith, Stephen J.; Adams, Joseph S.; Bandler, Simon R.; Chervenak, James A.; Datesman, Aaron Michael; Eckart, Megan E.; Ewin, Audrey J.; Finkbeiner, Fred M.; Kelley, Richard L.; Kilbourne, Caroline A.;

Characterization of pixelated TlBr detectors with Tl electrodes

NASA Astrophysics Data System (ADS)

Hitomi, Keitaro; Onodera, Toshiyuki; Kim, Seong-Yun; Shoji, Tadayoshi; Ishii, Keizo

2014-05-01

A 4.36-mm-thick pixelated thallium bromide (TlBr) detector with Tl electrodes was fabricated from a crystal grown by the traveling molten zone method using zone-purified material. The detector had four 1×1 mm2 pixelated anodes. The detector performance was characterized at room temperature. The mobility-lifetime products of electrons for each pixel of the TlBr detector were measured to be >2.8×10-3 cm2/V. The four pixelated anodes of the detector exhibited energy resolutions of 1.5-1.8% full width at half maximum (FWHM) for 662-keV gamma rays for single-pixel events with the depth correction method. An energy resolution of 4.5% FWHM for 662-keV gamma rays was obtained from a reconstructed energy spectrum using two-pixel events from the two pixelated anodes on the detector.

CMOS foveal image sensor chip

NASA Technical Reports Server (NTRS)

Scott, Peter (Inventor); Sridhar, Ramalingam (Inventor); Bandera, Cesar (Inventor); Xia, Shu (Inventor)

2002-01-01

A foveal image sensor integrated circuit comprising a plurality of CMOS active pixel sensors arranged both within and about a central fovea region of the chip. The pixels in the central fovea region have a smaller size than the pixels arranged in peripheral rings about the central region. A new photocharge normalization scheme and associated circuitry normalizes the output signals from the different size pixels in the array. The pixels are assembled into a multi-resolution rectilinear foveal image sensor chip using a novel access scheme to reduce the number of analog RAM cells needed. Localized spatial resolution declines monotonically with offset from the imager's optical axis, analogous to biological foveal vision.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kwan, Simon; Lei, CM; Menasce, Dario

An all silicon pixel telescope has been assembled and used at the Fermilab Test Beam Facility (FTBF) since 2009 to provide precise tracking information for different test beam experiments with a wide range of Detectors Under Test (DUTs) requiring high resolution measurement of the track impact point. The telescope is based on CMS pixel modules left over from the CMS forward pixel production. Eight planes are arranged to achieve a resolution of less than 8 μm on the 120 GeV proton beam transverse coordinate at the DUT position. In order to achieve such resolution with 100 × 150 μm 2more » pixel cells, the planes were tilted to 25 degrees to maximize charge sharing between pixels. Crucial for obtaining this performance is the alignment software, called Monicelli, specifically designed and optimized for this system. This paper will describe the telescope hardware, the data acquisition system and the alignment software constituting this particle tracking system for test beam users.« less

Characterization of a 2-mm thick, 16x16 Cadmium-Zinc-Telluride Pixel Array

NASA Technical Reports Server (NTRS)

Gaskin, Jessica; Richardson, Georgia; Mitchell, Shannon; Ramsey, Brian; Seller, Paul; Sharma, Dharma

2003-01-01

The detector under study is a 2-mm-thick, 16x16 Cadmium-Zinc-Telluride pixel array with a pixel pitch of 300 microns and inter-pixel gap of 50 microns. This detector is a precursor to that which will be used at the focal plane of the High Energy Replicated Optics (HERO) telescope currently being developed at Marshall Space Flight Center. With a telescope focal length of 6 meters, the detector needs to have a spatial resolution of around 200 microns in order to take full advantage of the HERO angular resolution. We discuss to what degree charge sharing will degrade energy resolution but will improve our spatial resolution through position interpolation. In addition, we discuss electric field modeling for this specific detector geometry and the role this mapping will play in terms of charge sharing and charge loss in the detector.

The effect of spatial resolution upon cloud optical property retrievals. I - Optical thickness

NASA Technical Reports Server (NTRS)

Feind, Rand E.; Christopher, Sundar A.; Welch, Ronald M.

1992-01-01

High spectral and spatial resolution Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) imagery is used to study the effects of spatial resolution upon fair weather cumulus cloud optical thickness retrievals. As a preprocessing step, a variation of the Gao and Goetz three-band ratio technique is used to discriminate clouds from the background. The combination of the elimination of cloud shadow pixels and using the first derivative of the histogram allows for accurate cloud edge discrimination. The data are progressively degraded from 20 m to 960 m spatial resolution. The results show that retrieved cloud area increases with decreasing spatial resolution. The results also show that there is a monotonic decrease in retrieved cloud optical thickness with decreasing spatial resolution. It is also demonstrated that the use of a single, monospectral reflectance threshold is inadequate for identifying cloud pixels in fair weather cumulus scenes and presumably in any inhomogeneous cloud field. Cloud edges have a distribution of reflectance thresholds. The incorrect identification of cloud edges significantly impacts the accurate retrieval of cloud optical thickness values.

Multiple Acquisition InSAR Analysis: Persistent Scatterer and Small Baseline Approaches

NASA Astrophysics Data System (ADS)

Hooper, A.

2006-12-01

InSAR techniques that process data from multiple acquisitions enable us to form time series of deformation and also allow us to reduce error terms present in single interferograms. There are currently two broad categories of methods that deal with multiple images: persistent scatterer methods and small baseline methods. The persistent scatterer approach relies on identifying pixels whose scattering properties vary little with time and look angle. Pixels that are dominated by a singular scatterer best meet these criteria; therefore, images are processed at full resolution to both increase the chance of there being only one dominant scatterer present, and to reduce the contribution from other scatterers within each pixel. In images where most pixels contain multiple scatterers of similar strength, even at the highest possible resolution, the persistent scatterer approach is less optimal, as the scattering characteristics of these pixels vary substantially with look angle. In this case, an approach that interferes only pairs of images for which the difference in look angle is small makes better sense, and resolution can be sacrificed to reduce the effects of the look angle difference by band-pass filtering. This is the small baseline approach. Existing small baseline methods depend on forming a series of multilooked interferograms and unwrapping each one individually. This approach fails to take advantage of two of the benefits of processing multiple acquisitions, however, which are usually embodied in persistent scatterer methods: the ability to find and extract the phase for single-look pixels with good signal-to-noise ratio that are surrounded by noisy pixels, and the ability to unwrap more robustly in three dimensions, the third dimension being that of time. We have developed, therefore, a new small baseline method to select individual single-look pixels that behave coherently in time, so that isolated stable pixels may be found. After correction for various error terms, the phase values of the selected pixels are unwrapped using a new three-dimensional algorithm. We apply our small baseline method to an area in southern Iceland that includes Katla and Eyjafjallajökull volcanoes, and retrieve a time series of deformation that shows transient deformation due to intrusion of magma beneath Eyjafjallajökull. We also process the data using the Stanford method for persistent scatterers (StaMPS) for comparison.

Joint denoising, demosaicing, and chromatic aberration correction for UHD video

NASA Astrophysics Data System (ADS)

Jovanov, Ljubomir; Philips, Wilfried; Damstra, Klaas Jan; Ellenbroek, Frank

2017-09-01

High-resolution video capture is crucial for numerous applications such as surveillance, security, industrial inspection, medical imaging and digital entertainment. In the last two decades, we are witnessing a dramatic increase of the spatial resolution and the maximal frame rate of video capturing devices. In order to achieve further resolution increase, numerous challenges will be facing us. Due to the reduced size of the pixel, the amount of light also reduces, leading to the increased noise level. Moreover, the reduced pixel size makes the lens imprecisions more pronounced, which especially applies to chromatic aberrations. Even in the case when high quality lenses are used some chromatic aberration artefacts will remain. Next, noise level additionally increases due to the higher frame rates. To reduce the complexity and the price of the camera, one sensor captures all three colors, by relying on Color Filter Arrays. In order to obtain full resolution color image, missing color components have to be interpolated, i.e. demosaicked, which is more challenging than in the case of lower resolution, due to the increased noise and aberrations. In this paper, we propose a new method, which jointly performs chromatic aberration correction, denoising and demosaicking. By jointly performing the reduction of all artefacts, we are reducing the overall complexity of the system and the introduction of new artefacts. In order to reduce possible flicker we also perform temporal video enhancement. We evaluate the proposed method on a number of publicly available UHD sequences and on sequences recorded in our studio.

Adaptive pixel-super-resolved lensfree in-line digital holography for wide-field on-chip microscopy.

PubMed

Zhang, Jialin; Sun, Jiasong; Chen, Qian; Li, Jiaji; Zuo, Chao

2017-09-18

High-resolution wide field-of-view (FOV) microscopic imaging plays an essential role in various fields of biomedicine, engineering, and physical sciences. As an alternative to conventional lens-based scanning techniques, lensfree holography provides a new way to effectively bypass the intrinsical trade-off between the spatial resolution and FOV of conventional microscopes. Unfortunately, due to the limited sensor pixel-size, unpredictable disturbance during image acquisition, and sub-optimum solution to the phase retrieval problem, typical lensfree microscopes only produce compromised imaging quality in terms of lateral resolution and signal-to-noise ratio (SNR). Here, we propose an adaptive pixel-super-resolved lensfree imaging (APLI) method which can solve, or at least partially alleviate these limitations. Our approach addresses the pixel aliasing problem by Z-scanning only, without resorting to subpixel shifting or beam-angle manipulation. Automatic positional error correction algorithm and adaptive relaxation strategy are introduced to enhance the robustness and SNR of reconstruction significantly. Based on APLI, we perform full-FOV reconstruction of a USAF resolution target (~29.85 mm 2 ) and achieve half-pitch lateral resolution of 770 nm, surpassing 2.17 times of the theoretical Nyquist-Shannon sampling resolution limit imposed by the sensor pixel-size (1.67µm). Full-FOV imaging result of a typical dicot root is also provided to demonstrate its promising potential applications in biologic imaging.

Where can pixel counting area estimates meet user-defined accuracy requirements?

NASA Astrophysics Data System (ADS)

Waldner, François; Defourny, Pierre

2017-08-01

Pixel counting is probably the most popular way to estimate class areas from satellite-derived maps. It involves determining the number of pixels allocated to a specific thematic class and multiplying it by the pixel area. In the presence of asymmetric classification errors, the pixel counting estimator is biased. The overarching objective of this article is to define the applicability conditions of pixel counting so that the estimates are below a user-defined accuracy target. By reasoning in terms of landscape fragmentation and spatial resolution, the proposed framework decouples the resolution bias and the classifier bias from the overall classification bias. The consequence is that prior to any classification, part of the tolerated bias is already committed due to the choice of the spatial resolution of the imagery. How much classification bias is affordable depends on the joint interaction of spatial resolution and fragmentation. The method was implemented over South Africa for cropland mapping, demonstrating its operational applicability. Particular attention was paid to modeling a realistic sensor's spatial response by explicitly accounting for the effect of its point spread function. The diagnostic capabilities offered by this framework have multiple potential domains of application such as guiding users in their choice of imagery and providing guidelines for space agencies to elaborate the design specifications of future instruments.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vedantham, Srinivasan; Shrestha, Suman; Karellas, Andrew, E-mail: andrew.karellas@umassmed.edu

Purpose: High-resolution, photon-counting, energy-resolved detector with fast-framing capability can facilitate simultaneous acquisition of precontrast and postcontrast images for subtraction angiography without pixel registration artifacts and can facilitate high-resolution real-time imaging during image-guided interventions. Hence, this study was conducted to determine the spatial resolution characteristics of a hexagonal pixel array photon-counting cadmium telluride (CdTe) detector. Methods: A 650 μm thick CdTe Schottky photon-counting detector capable of concurrently acquiring up to two energy-windowed images was operated in a single energy-window mode to include photons of 10 keV or higher. The detector had hexagonal pixels with apothem of 30 μm resulting in pixelmore » pitch of 60 and 51.96 μm along the two orthogonal directions. The detector was characterized at IEC-RQA5 spectral conditions. Linear response of the detector was determined over the air kerma rate relevant to image-guided interventional procedures ranging from 1.3 nGy/frame to 91.4 μGy/frame. Presampled modulation transfer was determined using a tungsten edge test device. The edge-spread function and the finely sampled line spread function accounted for hexagonal sampling, from which the presampled modulation transfer function (MTF) was determined. Since detectors with hexagonal pixels require resampling to square pixels for distortion-free display, the optimal square pixel size was determined by minimizing the root-mean-squared-error of the aperture functions for the square and hexagonal pixels up to the Nyquist limit. Results: At Nyquist frequencies of 8.33 and 9.62 cycles/mm along the apothem and orthogonal to the apothem directions, the modulation factors were 0.397 and 0.228, respectively. For the corresponding axis, the limiting resolution defined as 10% MTF occurred at 13.3 and 12 cycles/mm, respectively. Evaluation of the aperture functions yielded an optimal square pixel size of 54 μm. After resampling to 54 μm square pixels using trilinear interpolation, the presampled MTF at Nyquist frequency of 9.26 cycles/mm was 0.29 and 0.24 along the orthogonal directions and the limiting resolution (10% MTF) occurred at approximately 12 cycles/mm. Visual analysis of a bar pattern image showed the ability to resolve close to 12 line-pairs/mm and qualitative evaluation of a neurovascular nitinol-stent showed the ability to visualize its struts at clinically relevant conditions. Conclusions: Hexagonal pixel array photon-counting CdTe detector provides high spatial resolution in single-photon counting mode. After resampling to optimal square pixel size for distortion-free display, the spatial resolution is preserved. The dual-energy capabilities of the detector could allow for artifact-free subtraction angiography and basis material decomposition. The proposed high-resolution photon-counting detector with energy-resolving capability can be of importance for several image-guided interventional procedures as well as for pediatric applications.« less

Extended focal-plane array development for the International X-ray Observatory

NASA Astrophysics Data System (ADS)

Smith, Stephen J.; Bandler, Simon R.; Beyer, Joern; Chervenak, James A.; Drung, Dietmar; Eckart, Megan E.; Finkbeiner, Fred M.; Kelley, Richard L.; Kilbourne, Caroline A.; Scott Porter, F.; Sadleir, John E.

2009-12-01

We are developing arrays of transition-edge sensors (TES's) for the International X-ray observatory (IXO). The IXO microcalorimeter array will consist of a central 40×40 core of 300 μm pitch pixels with a resolution of 2.5 eV from 0.3-10 keV. To maximize the science return from the mission, an outer extended array is also required. This 52×52 array (2304 elements surrounding the core) of 600 μm pitch pixels increases the field-of-view from 2' to 5.4' with a resolution of 10 eV. However, significantly increasing the number of readout channels is unfavorable due to the increase in mass and power of the readout chain as well as adding complexity at the focal plane. Consequently, we are developing position-sensitive devices which maintain the same plate scale but at a reduced number of readout channels. One option is to use multiple absorber elements with different thermal conductances to a single TES. Position discrimination is achieved from differences in the pulse rise-time. Another new option is to inductively couple several TES's to a single SQUID. Position discrimination can be achieved by using different combinations of coupling polarity, inductive couplings and heat sink conductances. We present first results demonstrating <9 eV across four 500 μm pixels coupled to a single SQUID. A further possibility is to increase the number of channels to be time-division multiplexed in a single column at some expense in resolution. In this paper we discuss experimental results and trade-offs for these extended array options.

DOI Determination by Rise Time Discrimination in Single-Ended Readout for TOF PET Imaging

PubMed Central

Wiener, R.I.; Surti, S.; Karp, J.S.

2013-01-01

Clinical TOF PET systems achieve detection efficiency using thick crystals, typically of thickness 2–3cm. The resulting dispersion in interaction depths degrades spatial resolution for increasing radial positions due to parallax error. Furthermore, interaction depth dispersion results in time pickoff dispersion and thus in degraded timing resolution, and is therefore of added concern in TOF scanners. Using fast signal digitization, we characterize the timing performance, pulse shape and light output of LaBr3:Ce, CeBr3 and LYSO. Coincidence timing resolution is shown to degrade by ~50ps/cm for scintillator pixels of constant cross section and increasing length. By controlling irradiation depth in a scintillator pixel, we show that DOI-dependence of time pickoff is a significant factor in the loss of timing performance in thick detectors. Using the correlated DOI-dependence of time pickoff and charge collection, we apply a charge-based correction to the time pickoff, obtaining improved coincidence timing resolution of <200ps for a uniform 4×4×30mm3 LaBr3 pixel. In order to obtain both DOI identification and improved timing resolution, we design a two layer LaBr3[5%Ce]/LaBr3[30%Ce] detector of total size 4×4×30mm3, exploiting the dependence of scintillator rise time on [Ce] in LaBr3:Ce. Using signal rise time to determine interaction layer, excellent interaction layer discrimination is achieved, while maintaining coincidence timing resolution of <250ps and energy resolution <7% using a R4998 PMT. Excellent layer separation and timing performance is measured with several other commercially-available TOF photodetectors, demonstrating the practicality of this design. These results indicate the feasibility of rise time discrimination as a technique for measuring event DOI while maintaining sensitivity, timing and energy performance, in a well-known detector architecture. PMID:24403611

DOI Determination by Rise Time Discrimination in Single-Ended Readout for TOF PET Imaging.

PubMed

Wiener, R I; Surti, S; Karp, J S

2013-06-01

Clinical TOF PET systems achieve detection efficiency using thick crystals, typically of thickness 2-3cm. The resulting dispersion in interaction depths degrades spatial resolution for increasing radial positions due to parallax error. Furthermore, interaction depth dispersion results in time pickoff dispersion and thus in degraded timing resolution, and is therefore of added concern in TOF scanners. Using fast signal digitization, we characterize the timing performance, pulse shape and light output of LaBr 3 :Ce, CeBr 3 and LYSO. Coincidence timing resolution is shown to degrade by ~50ps/cm for scintillator pixels of constant cross section and increasing length. By controlling irradiation depth in a scintillator pixel, we show that DOI-dependence of time pickoff is a significant factor in the loss of timing performance in thick detectors. Using the correlated DOI-dependence of time pickoff and charge collection, we apply a charge-based correction to the time pickoff, obtaining improved coincidence timing resolution of <200ps for a uniform 4×4×30mm 3 LaBr 3 pixel. In order to obtain both DOI identification and improved timing resolution, we design a two layer LaBr 3 [5%Ce]/LaBr 3 [30%Ce] detector of total size 4×4×30mm 3 , exploiting the dependence of scintillator rise time on [Ce] in LaBr 3 :Ce. Using signal rise time to determine interaction layer, excellent interaction layer discrimination is achieved, while maintaining coincidence timing resolution of <250ps and energy resolution <7% using a R4998 PMT. Excellent layer separation and timing performance is measured with several other commercially-available TOF photodetectors, demonstrating the practicality of this design. These results indicate the feasibility of rise time discrimination as a technique for measuring event DOI while maintaining sensitivity, timing and energy performance, in a well-known detector architecture.

A method for generating high resolution satellite image time series

NASA Astrophysics Data System (ADS)

Guo, Tao

2014-10-01

There is an increasing demand for satellite remote sensing data with both high spatial and temporal resolution in many applications. But it still is a challenge to simultaneously improve spatial resolution and temporal frequency due to the technical limits of current satellite observation systems. To this end, much R&D efforts have been ongoing for years and lead to some successes roughly in two aspects, one includes super resolution, pan-sharpen etc. methods which can effectively enhance the spatial resolution and generate good visual effects, but hardly preserve spectral signatures and result in inadequate analytical value, on the other hand, time interpolation is a straight forward method to increase temporal frequency, however it increase little informative contents in fact. In this paper we presented a novel method to simulate high resolution time series data by combing low resolution time series data and a very small number of high resolution data only. Our method starts with a pair of high and low resolution data set, and then a spatial registration is done by introducing LDA model to map high and low resolution pixels correspondingly. Afterwards, temporal change information is captured through a comparison of low resolution time series data, and then projected onto the high resolution data plane and assigned to each high resolution pixel according to the predefined temporal change patterns of each type of ground objects. Finally the simulated high resolution data is generated. A preliminary experiment shows that our method can simulate a high resolution data with a reasonable accuracy. The contribution of our method is to enable timely monitoring of temporal changes through analysis of time sequence of low resolution images only, and usage of costly high resolution data can be reduces as much as possible, and it presents a highly effective way to build up an economically operational monitoring solution for agriculture, forest, land use investigation, environment and etc. applications.

Development of a Cost-Effective Modular Pixelated NaI(Tl) Detector for Clinical SPECT Applications

PubMed Central

Rozler, Mike; Liang, Haoning; Chang, Wei

2013-01-01

A new pixelated detector for high-resolution clinical SPECT applications was designed and tested. The modular detector is based on a scintillator block comprised of 2.75×2.75×10 mm3 NaI(Tl) pixels and decoded by an array of 51 mm diameter single-anode PMTs. Several configurations, utilizing two types of PMTs, were evaluated using a collimated beam source to measure positioning accuracy directly. Good pixel separation was observed, with correct pixel identification ranging from 60 to 72% averaged over the entire area of the modules, depending on the PMT type and configuration. This translates to a significant improvement in positioning accuracy compared to continuous slab detectors of the same thickness, along with effective reduction of “dead” space at the edges. The observed 10% average energy resolution compares well to continuous slab detectors. The combined performance demonstrates the suitability of pixelated detectors decoded with a relatively small number of medium-sized PMTs as a cost-effective approach for high resolution clinical SPECT applications, in particular those involving curved detector geometries. PMID:24146436

Iterative algorithm for reconstructing rotationally asymmetric surface deviation with pixel-level spatial resolution

NASA Astrophysics Data System (ADS)

Quan, Haiyang; Wu, Fan; Hou, Xi

2015-10-01

New method for reconstructing rotationally asymmetric surface deviation with pixel-level spatial resolution is proposed. It is based on basic iterative scheme and accelerates the Gauss-Seidel method by introducing an acceleration parameter. This modified Successive Over-relaxation (SOR) is effective for solving the rotationally asymmetric components with pixel-level spatial resolution, without the usage of a fitting procedure. Compared to the Jacobi and Gauss-Seidel method, the modified SOR method with an optimal relaxation factor converges much faster and saves more computational costs and memory space without reducing accuracy. It has been proved by real experimental results.

The CAOS camera platform: ushering in a paradigm change in extreme dynamic range imager design

NASA Astrophysics Data System (ADS)

Riza, Nabeel A.

2017-02-01

Multi-pixel imaging devices such as CCD, CMOS and Focal Plane Array (FPA) photo-sensors dominate the imaging world. These Photo-Detector Array (PDA) devices certainly have their merits including increasingly high pixel counts and shrinking pixel sizes, nevertheless, they are also being hampered by limitations in instantaneous dynamic range, inter-pixel crosstalk, quantum full well capacity, signal-to-noise ratio, sensitivity, spectral flexibility, and in some cases, imager response time. Recently invented is the Coded Access Optical Sensor (CAOS) Camera platform that works in unison with current Photo-Detector Array (PDA) technology to counter fundamental limitations of PDA-based imagers while providing high enough imaging spatial resolution and pixel counts. Using for example the Texas Instruments (TI) Digital Micromirror Device (DMD) to engineer the CAOS camera platform, ushered in is a paradigm change in advanced imager design, particularly for extreme dynamic range applications.

Nuclear resonant scattering measurements on (57)Fe by multichannel scaling with a 64-pixel silicon avalanche photodiode linear-array detector.

PubMed

Kishimoto, S; Mitsui, T; Haruki, R; Yoda, Y; Taniguchi, T; Shimazaki, S; Ikeno, M; Saito, M; Tanaka, M

2014-11-01

We developed a silicon avalanche photodiode (Si-APD) linear-array detector for use in nuclear resonant scattering experiments using synchrotron X-rays. The Si-APD linear array consists of 64 pixels (pixel size: 100 × 200 μm(2)) with a pixel pitch of 150 μm and depletion depth of 10 μm. An ultrafast frontend circuit allows the X-ray detector to obtain a high output rate of >10(7) cps per pixel. High-performance integrated circuits achieve multichannel scaling over 1024 continuous time bins with a 1 ns resolution for each pixel without dead time. The multichannel scaling method enabled us to record a time spectrum of the 14.4 keV nuclear radiation at each pixel with a time resolution of 1.4 ns (FWHM). This method was successfully applied to nuclear forward scattering and nuclear small-angle scattering on (57)Fe.

Extraction of temporal information in functional MRI

NASA Astrophysics Data System (ADS)

Singh, M.; Sungkarat, W.; Jeong, Jeong-Won; Zhou, Yongxia

2002-10-01

The temporal resolution of functional MRI (fMRI) is limited by the shape of the haemodynamic response function (hrf) and the vascular architecture underlying the activated regions. Typically, the temporal resolution of fMRI is on the order of 1 s. We have developed a new data processing approach to extract temporal information on a pixel-by-pixel basis at the level of 100 ms from fMRI data. Instead of correlating or fitting the time-course of each pixel to a single reference function, which is the common practice in fMRI, we correlate each pixel's time-course to a series of reference functions that are shifted with respect to each other by 100 ms. The reference function yielding the highest correlation coefficient for a pixel is then used as a time marker for that pixel. A Monte Carlo simulation and experimental study of this approach were performed to estimate the temporal resolution as a function of signal-to-noise ratio (SNR) in the time-course of a pixel. Assuming a known and stationary hrf, the simulation and experimental studies suggest a lower limit in the temporal resolution of approximately 100 ms at an SNR of 3. The multireference function approach was also applied to extract timing information from an event-related motor movement study where the subjects flexed a finger on cue. The event was repeated 19 times with the event's presentation staggered to yield an approximately 100-ms temporal sampling of the haemodynamic response over the entire presentation cycle. The timing differences among different regions of the brain activated by the motor task were clearly visualized and quantified by this method. The results suggest that it is possible to achieve a temporal resolution of /spl sim/200 ms in practice with this approach.

Assessing the capability of different satellite observing configurations to resolve the distribution of methane emissions at kilometer scales

NASA Astrophysics Data System (ADS)

Turner, Alexander J.; Jacob, Daniel J.; Benmergui, Joshua; Brandman, Jeremy; White, Laurent; Randles, Cynthia A.

2018-06-01

Anthropogenic methane emissions originate from a large number of fine-scale and often transient point sources. Satellite observations of atmospheric methane columns are an attractive approach for monitoring these emissions but have limitations from instrument precision, pixel resolution, and measurement frequency. Dense observations will soon be available in both low-Earth and geostationary orbits, but the extent to which they can provide fine-scale information on methane sources has yet to be explored. Here we present an observation system simulation experiment (OSSE) to assess the capabilities of different satellite observing system configurations. We conduct a 1-week WRF-STILT simulation to generate methane column footprints at 1.3 × 1.3 km2 spatial resolution and hourly temporal resolution over a 290 × 235 km2 domain in the Barnett Shale, a major oil and gas field in Texas with a large number of point sources. We sub-sample these footprints to match the observing characteristics of the recently launched TROPOMI instrument (7 × 7 km2 pixels, 11 ppb precision, daily frequency), the planned GeoCARB instrument (2.7 × 3.0 km2 pixels, 4 ppb precision, nominal twice-daily frequency), and other proposed observing configurations. The information content of the various observing systems is evaluated using the Fisher information matrix and its eigenvalues. We find that a week of TROPOMI observations should provide information on temporally invariant emissions at ˜ 30 km spatial resolution. GeoCARB should provide information available on temporally invariant emissions ˜ 2-7 km spatial resolution depending on sampling frequency (hourly to daily). Improvements to the instrument precision yield greater increases in information content than improved sampling frequency. A precision better than 6 ppb is critical for GeoCARB to achieve fine resolution of emissions. Transient emissions would be missed with either TROPOMI or GeoCARB. An aspirational high-resolution geostationary instrument with 1.3 × 1.3 km2 pixel resolution, hourly return time, and 1 ppb precision would effectively constrain the temporally invariant emissions in the Barnett Shale at the kilometer scale and provide some information on hourly variability of sources.

Restoring the spatial resolution of refocus images on 4D light field

NASA Astrophysics Data System (ADS)

Lim, JaeGuyn; Park, ByungKwan; Kang, JooYoung; Lee, SeongDeok

2010-01-01

This paper presents the method for generating a refocus image with restored spatial resolution on a plenoptic camera, which functions controlling the depth of field after capturing one image unlike a traditional camera. It is generally known that the camera captures 4D light field (angular and spatial information of light) within a limited 2D sensor and results in reducing 2D spatial resolution due to inevitable 2D angular data. That's the reason why a refocus image is composed of a low spatial resolution compared with 2D sensor. However, it has recently been known that angular data contain sub-pixel spatial information such that the spatial resolution of 4D light field can be increased. We exploit the fact for improving the spatial resolution of a refocus image. We have experimentally scrutinized that the spatial information is different according to the depth of objects from a camera. So, from the selection of refocused regions (corresponding depth), we use corresponding pre-estimated sub-pixel spatial information for reconstructing spatial resolution of the regions. Meanwhile other regions maintain out-of-focus. Our experimental results show the effect of this proposed method compared to existing method.

Mass test of AdvanSiD model ASD-NUV3S-P SiliconPMs for the Pixel Timing Counter of the MEG II experiment

NASA Astrophysics Data System (ADS)

Rossella, M.; Bariani, S.; Barnaba, O.; Cattaneo, P. W.; Cervi, T.; Menegolli, A.; Nardò, R.; Prata, M. C.; Romano, E.; Scagliotti, C.; Simonetta, M.; Vercellati, F.

2017-02-01

The MEG II Timing Counter will measure the positron time of arrival with a resolution of 30 ps relying on two arrays of scintillator pixels read out by 6144 Silicon Photomultipliers (SiPMs) from AdvanSiD. They must be characterized, measuring their breakdown voltage, to assure that the gains of the SiPMs of each pixel are as uniform as possible, to maximize the pixel resolution. To do this an automatic test system that can measure sequentially the parameters of 32 devices has been developed.

Estimating Daily Evapotranspiration Based on A Model of Evapotranspiration Fraction (EF) for Mixed Pixels

NASA Astrophysics Data System (ADS)

Xin, X.; Li, F.; Peng, Z.; Qinhuo, L.

2017-12-01

Land surface heterogeneities significantly affect the reliability and accuracy of remotely sensed evapotranspiration (ET), and it gets worse for lower resolution data. At the same time, temporal scale extrapolation of the instantaneous latent heat flux (LE) at satellite overpass time to daily ET are crucial for applications of such remote sensing product. The purpose of this paper is to propose a simple but efficient model for estimating daytime evapotranspiration considering heterogeneity of mixed pixels. In order to do so, an equation to calculate evapotranspiration fraction (EF) of mixed pixels was derived based on two key assumptions. Assumption 1: the available energy (AE) of each sub-pixel equals approximately to that of any other sub-pixels in the same mixed pixel within acceptable margin of bias, and as same as the AE of the mixed pixel. It's only for a simpification of the equation, and its uncertainties and resulted errors in estimated ET are very small. Assumption 2: EF of each sub-pixel equals to the EF of the nearest pure pixel(s) of same land cover type. This equation is supposed to be capable of correcting the spatial scale error of the mixed pixels EF and can be used to calculated daily ET with daily AE data.The model was applied to an artificial oasis in the midstream of Heihe River. HJ-1B satellite data were used to estimate the lumped fluxes at the scale of 300 m after resampling the 30-m resolution datasets to 300 m resolution, which was used to carry on the key step of the model. The results before and after correction were compare to each other and validated using site data of eddy-correlation systems. Results indicated that the new model is capable of improving accuracy of daily ET estimation relative to the lumped method. Validations at 12 sites of eddy-correlation systems for 9 days of HJ-1B overpass showed that the R² increased to 0.82 from 0.62; the RMSE decreased to 1.60 MJ/m² from 2.47MJ/m²; the MBE decreased from 1.92 MJ/m² to 1.18MJ/m², which is a quite significant enhancement.The model is easy to apply. And the moduler of inhomogeneous surfaces is independent and easy to be embedded in the traditional remote sensing algorithms of heat fluxes to get daily ET, which were mainly designed to calculate LE or ET under unsaturated conditions and did not consider heterogeneities of land surface.

Fires in Philippines

NASA Technical Reports Server (NTRS)

2002-01-01

Roughly a dozen fires (red pixels) dotted the landscape on the main Philippine island of Luzon on April 1, 2002. This true-color image was acquired by the Moderate-resolution Imaging Spectroradiometer (MODIS), flying aboard NASA's Terra spacecraft. Please note that the high-resolution scene provided here is 500 meters per pixel. For a copy of this scene at the sensor's fullest resolution, visit the MODIS Rapidfire site.

Modeling and Measuring Charge-Sharing in Hard X-ray Imagers Using HEXITEC CdTe Detectors

NASA Technical Reports Server (NTRS)

Ryan, Daniel F.; Christe, Steven D.; Shih, Albert Y.; Baumgartner, Wayne H.; Wilson, Matthew D.; Seller, Paul; Gaskin, Jessica A.; Inglis, Andrew

2017-01-01

The Rutherford Appleton Laboratory's HEXITEC ASIC has been designed to provide fine pixelated X-ray spectroscopic imaging in combination with a CdTe or CZT detector layer. Although HEXITEC's small pixels enable higher spatial resolution as well as higher spectral resolution via the small-pixel effect, they also increase the probability of charge sharing, a process which degrades spectral performance by dividing the charge induced by a single photon among multiple pixels. In this paper, we investigate the effect of this process on a continuum X-ray spectrum below the Cd and Te fluorescence energies (23 keV). This is done by comparing laboratory measurements with simulations performed with a custom designed model of the HEXITEC ASIC. We find that the simulations closely match the observations implying that we have an adequate understanding of both charge sharing and the HEXITEC ASIC itself. These results can be used to predict the distortion of a spectrum measured with HEXITEC and will help determine to what extent it can be corrected. They also show that models like this one are important tools in developing and interpreting observations from ASICs like HEXITEC.

Retrieval of Cloud Properties for Partially Cloud-Filled Pixels During CRYSTAL-FACE

NASA Astrophysics Data System (ADS)

Nguyen, L.; Minnis, P.; Smith, W. L.; Khaiyer, M. M.; Heck, P. W.; Sun-Mack, S.; Uttal, T.; Comstock, J.

2003-12-01

Partially cloud-filled pixels can be a significant problem for remote sensing of cloud properties. Generally, the optical depth and effective particle sizes are often too small or too large, respectively, when derived from radiances that are assumed to be overcast but contain radiation from both clear and cloud areas within the satellite imager field of view. This study presents a method for reducing the impact of such partially cloud field pixels by estimating the cloud fraction within each pixel using higher resolution visible (VIS, 0.65mm) imager data. Although the nominal resolution for most channels on the Geostationary Operational Environmental Satellite (GOES) imager and the Moderate Resolution Imaging Spectroradiometer (MODIS) on Terra are 4 and 1 km, respectively, both instruments also take VIS channel data at 1 km and 0.25 km, respectively. Thus, it may be possible to obtain an improved estimate of cloud fraction within the lower resolution pixels by using the information contained in the higher resolution VIS data. GOES and MODIS multi-spectral data, taken during the Cirrus Regional Study of Tropical Anvils and Cirrus Layers - Florida Area Cirrus Experiment (CRYSTAL-FACE), are analyzed with the algorithm used for the Atmospheric Radiation Measurement Program (ARM) and the Clouds and Earth's Radiant Energy System (CERES) to derive cloud amount, temperature, height, phase, effective particle size, optical depth, and water path. Normally, the algorithm assumes that each pixel is either entirely clear or cloudy. In this study, a threshold method is applied to the higher resolution VIS data to estimate the partial cloud fraction within each low-resolution pixel. The cloud properties are then derived from the observed low-resolution radiances using the cloud cover estimate to properly extract the radiances due only to the cloudy part of the scene. This approach is applied to both GOES and MODIS data to estimate the improvement in the retrievals for each resolution. Results are compared with the radar reflectivity techniques employed by the NOAA ETL MMCR and the PARSL 94 GHz radars located at the CRYSTAL-FACE Eastern & Western Ground Sites, respectively. This technique is most likely to yield improvements for low and midlevel layer clouds that have little thermal variability in cloud height.

Efficient conceptual design for LED-based pixel light vehicle headlamps

NASA Astrophysics Data System (ADS)

Held, Marcel Philipp; Lachmayer, Roland

2017-12-01

High-resolution vehicle headlamps represent a future-oriented technology that can be used to increase traffic safety and driving comfort. As a further development to the current Matrix Beam headlamps, LED-based pixel light systems enable ideal lighting functions (e.g. projection of navigation information onto the road) to be activated in any given driving scenario. Moreover, compared to other light-modulating elements such as DMDs and LCDs, instantaneous LED on-off toggling provides a decisive advantage in efficiency. To generate highly individualized light distributions for automotive applications, a number of approaches using an LED array may be pursued. One approach is to vary the LED density in the array so as to output the desired light distribution. Another notable approach makes use of an equidistant arrangement of the individual LEDs together with distortion optics to formulate the desired light distribution. The optical system adjusts the light distribution in a manner that improves resolution and increases luminous intensity of the desired area. An efficient setup for pixel generation calls for one lens per LED. Taking into consideration the limited space requirements of the system, this implies that the luminous flux, efficiency and resolution image parameters are primarily controlled by the lens dimensions. In this paper a concept for an equidistant LED array arrangement utilizing distortion optics is presented. The paper is divided into two parts. The first part discusses the influence of lens geometry on the system efficiency whereas the second part investigates the correlation between resolution and luminous flux based on the lens dimensions.

Sub-pixel Area Calculation Methods for Estimating Irrigated Areas.

PubMed

Thenkabailc, Prasad S; Biradar, Chandrashekar M; Noojipady, Praveen; Cai, Xueliang; Dheeravath, Venkateswarlu; Li, Yuanjie; Velpuri, Manohar; Gumma, Muralikrishna; Pandey, Suraj

2007-10-31

The goal of this paper was to develop and demonstrate practical methods forcomputing sub-pixel areas (SPAs) from coarse-resolution satellite sensor data. Themethods were tested and verified using: (a) global irrigated area map (GIAM) at 10-kmresolution based, primarily, on AVHRR data, and (b) irrigated area map for India at 500-mbased, primarily, on MODIS data. The sub-pixel irrigated areas (SPIAs) from coarse-resolution satellite sensor data were estimated by multiplying the full pixel irrigated areas(FPIAs) with irrigated area fractions (IAFs). Three methods were presented for IAFcomputation: (a) Google Earth Estimate (IAF-GEE); (b) High resolution imagery (IAF-HRI); and (c) Sub-pixel de-composition technique (IAF-SPDT). The IAF-GEE involvedthe use of "zoom-in-views" of sub-meter to 4-meter very high resolution imagery (VHRI)from Google Earth and helped determine total area available for irrigation (TAAI) or netirrigated areas that does not consider intensity or seasonality of irrigation. The IAF-HRI isa well known method that uses finer-resolution data to determine SPAs of the coarser-resolution imagery. The IAF-SPDT is a unique and innovative method wherein SPAs aredetermined based on the precise location of every pixel of a class in 2-dimensionalbrightness-greenness-wetness (BGW) feature-space plot of red band versus near-infraredband spectral reflectivity. The SPIAs computed using IAF-SPDT for the GIAM was within2 % of the SPIA computed using well known IAF-HRI. Further the fractions from the 2 methods were significantly correlated. The IAF-HRI and IAF-SPDT help to determine annualized or gross irrigated areas (AIA) that does consider intensity or seasonality (e.g., sum of areas from season 1, season 2, and continuous year-round crops). The national census based irrigated areas for the top 40 irrigated nations (which covers about 90% of global irrigation) was significantly better related (and had lesser uncertainties and errors) when compared to SPIAs than FPIAs derived using 10-km and 500-m data. The SPIAs were closer to actual areas whereas FPIAs grossly over-estimate areas. The research clearly demonstrated the value and the importance of sub-pixel areas as opposed to full pixel areas and presented 3 innovative methods for computing the same.

High dynamic range bio-molecular ion microscopy with the Timepix detector.

PubMed

Jungmann, Julia H; MacAleese, Luke; Visser, Jan; Vrakking, Marc J J; Heeren, Ron M A

2011-10-15

Highly parallel, active pixel detectors enable novel detection capabilities for large biomolecules in time-of-flight (TOF) based mass spectrometry imaging (MSI). In this work, a 512 × 512 pixel, bare Timepix assembly combined with chevron microchannel plates (MCP) captures time-resolved images of several m/z species in a single measurement. Mass-resolved ion images from Timepix measurements of peptide and protein standards demonstrate the capability to return both mass-spectral and localization information of biologically relevant analytes from matrix-assisted laser desorption ionization (MALDI) on a commercial ion microscope. The use of a MCP-Timepix assembly delivers an increased dynamic range of several orders of magnitude. The Timepix returns defined mass spectra already at subsaturation MCP gains, which prolongs the MCP lifetime and allows the gain to be optimized for image quality. The Timepix peak resolution is only limited by the resolution of the in-pixel measurement clock. Oligomers of the protein ubiquitin were measured up to 78 kDa. © 2011 American Chemical Society

Multiple Sensor Camera for Enhanced Video Capturing

NASA Astrophysics Data System (ADS)

Nagahara, Hajime; Kanki, Yoshinori; Iwai, Yoshio; Yachida, Masahiko

A resolution of camera has been drastically improved under a current request for high-quality digital images. For example, digital still camera has several mega pixels. Although a video camera has the higher frame-rate, the resolution of a video camera is lower than that of still camera. Thus, the high-resolution is incompatible with the high frame rate of ordinary cameras in market. It is difficult to solve this problem by a single sensor, since it comes from physical limitation of the pixel transfer rate. In this paper, we propose a multi-sensor camera for capturing a resolution and frame-rate enhanced video. Common multi-CCDs camera, such as 3CCD color camera, has same CCD for capturing different spectral information. Our approach is to use different spatio-temporal resolution sensors in a single camera cabinet for capturing higher resolution and frame-rate information separately. We build a prototype camera which can capture high-resolution (2588×1958 pixels, 3.75 fps) and high frame-rate (500×500, 90 fps) videos. We also proposed the calibration method for the camera. As one of the application of the camera, we demonstrate an enhanced video (2128×1952 pixels, 90 fps) generated from the captured videos for showing the utility of the camera.

An image quality comparison study between XVI and OBI CBCT systems.

PubMed

Kamath, Srijit; Song, William; Chvetsov, Alexei; Ozawa, Shuichi; Lu, Haibin; Samant, Sanjiv; Liu, Chihray; Li, Jonathan G; Palta, Jatinder R

2011-02-04

The purpose of this study is to evaluate and compare image quality characteristics for two commonly used and commercially available CBCT systems: the X-ray Volumetric Imager and the On-Board Imager. A commonly used CATPHAN image quality phantom was used to measure various image quality parameters, namely, pixel value stability and accuracy, noise, contrast to noise ratio (CNR), high-contrast resolution, low contrast resolution and image uniformity. For the XVI unit, we evaluated the image quality for four manufacturer-supplied protocols as a function of mAs. For the OBI unit, we did the same for the full-fan and half-fan scanning modes, which were respectively used with the full bow-tie and half bow-tie filters. For XVI, the mean pixel values of regions of interest were found to generally decrease with increasing mAs for all protocols, while they were relatively stable with mAs for OBI. Noise was slightly lower on XVI and was seen to decrease with increasing mAs, while CNR increased with mAs for both systems. For XVI and OBI, the high-contrast resolution was approximately limited by the pixel resolution of the reconstructed image. On OBI images, up to 6 and 5 discs of 1% and 0.5% contrast, respectively, were visible for a high mAs setting using the full-fan mode, while none of the discs were clearly visible on the XVI images for various mAs settings when the medium resolution reconstruction was used. In conclusion, image quality parameters for XVI and OBI have been quantified and compared for clinical protocols under various mAs settings. These results need to be viewed in the context of a recent study that reported the dose-mAs relationship for the two systems and found that OBI generally delivered higher imaging doses than XVI.

Mercuric iodide room-temperature array detectors for gamma-ray imaging

DOE Office of Scientific and Technical Information (OSTI.GOV)

Patt, B.

Significant progress has been made recently in the development of mercuric iodide detector arrays for gamma-ray imaging, making real the possibility of constructing high-performance small, light-weight, portable gamma-ray imaging systems. New techniques have been applied in detector fabrication and then low noise electronics which have produced pixel arrays with high-energy resolution, high spatial resolution, high gamma stopping efficiency. Measurements of the energy resolution capability have been made on a 19-element protypical array. Pixel energy resolutions of 2.98% fwhm and 3.88% fwhm were obtained at 59 keV (241-Am) and 140-keV (99m-Tc), respectively. The pixel spectra for a 14-element section of themore » data is shown together with the composition of the overlapped individual pixel spectra. These techniques are now being applied to fabricate much larger arrays with thousands of pixels. Extension of these principles to imaging scenarios involving gamma-ray energies up to several hundred keV is also possible. This would enable imaging of the 208 keV and 375-414 keV 239-Pu and 240-Pu structures, as well as the 186 keV line of 235-U.« less

A comparative analysis of pixel- and object-based detection of landslides from very high-resolution images

NASA Astrophysics Data System (ADS)

Keyport, Ren N.; Oommen, Thomas; Martha, Tapas R.; Sajinkumar, K. S.; Gierke, John S.

2018-02-01

A comparative analysis of landslides detected by pixel-based and object-oriented analysis (OOA) methods was performed using very high-resolution (VHR) remotely sensed aerial images for the San Juan La Laguna, Guatemala, which witnessed widespread devastation during the 2005 Hurricane Stan. A 3-band orthophoto of 0.5 m spatial resolution together with a 115 field-based landslide inventory were used for the analysis. A binary reference was assigned with a zero value for landslide and unity for non-landslide pixels. The pixel-based analysis was performed using unsupervised classification, which resulted in 11 different trial classes. Detection of landslides using OOA includes 2-step K-means clustering to eliminate regions based on brightness; elimination of false positives using object properties such as rectangular fit, compactness, length/width ratio, mean difference of objects, and slope angle. Both overall accuracy and F-score for OOA methods outperformed pixel-based unsupervised classification methods in both landslide and non-landslide classes. The overall accuracy for OOA and pixel-based unsupervised classification was 96.5% and 94.3%, respectively, whereas the best F-score for landslide identification for OOA and pixel-based unsupervised methods: were 84.3% and 77.9%, respectively.Results indicate that the OOA is able to identify the majority of landslides with a few false positive when compared to pixel-based unsupervised classification.

Enhancing spatial resolution of (18)F positron imaging with the Timepix detector by classification of primary fired pixels using support vector machine.

PubMed

Wang, Qian; Liu, Zhen; Ziegler, Sibylle I; Shi, Kuangyu

2015-07-07

Position-sensitive positron cameras using silicon pixel detectors have been applied for some preclinical and intraoperative clinical applications. However, the spatial resolution of a positron camera is limited by positron multiple scattering in the detector. An incident positron may fire a number of successive pixels on the imaging plane. It is still impossible to capture the primary fired pixel along a particle trajectory by hardware or to perceive the pixel firing sequence by direct observation. Here, we propose a novel data-driven method to improve the spatial resolution by classifying the primary pixels within the detector using support vector machine. A classification model is constructed by learning the features of positron trajectories based on Monte-Carlo simulations using Geant4. Topological and energy features of pixels fired by (18)F positrons were considered for the training and classification. After applying the classification model on measurements, the primary fired pixels of the positron tracks in the silicon detector were estimated. The method was tested and assessed for [(18)F]FDG imaging of an absorbing edge protocol and a leaf sample. The proposed method improved the spatial resolution from 154.6   ±   4.2 µm (energy weighted centroid approximation) to 132.3   ±   3.5 µm in the absorbing edge measurements. For the positron imaging of a leaf sample, the proposed method achieved lower root mean square error relative to phosphor plate imaging, and higher similarity with the reference optical image. The improvements of the preliminary results support further investigation of the proposed algorithm for the enhancement of positron imaging in clinical and preclinical applications.

Enhancing spatial resolution of 18F positron imaging with the Timepix detector by classification of primary fired pixels using support vector machine

NASA Astrophysics Data System (ADS)

Wang, Qian; Liu, Zhen; Ziegler, Sibylle I.; Shi, Kuangyu

2015-07-01

Position-sensitive positron cameras using silicon pixel detectors have been applied for some preclinical and intraoperative clinical applications. However, the spatial resolution of a positron camera is limited by positron multiple scattering in the detector. An incident positron may fire a number of successive pixels on the imaging plane. It is still impossible to capture the primary fired pixel along a particle trajectory by hardware or to perceive the pixel firing sequence by direct observation. Here, we propose a novel data-driven method to improve the spatial resolution by classifying the primary pixels within the detector using support vector machine. A classification model is constructed by learning the features of positron trajectories based on Monte-Carlo simulations using Geant4. Topological and energy features of pixels fired by 18F positrons were considered for the training and classification. After applying the classification model on measurements, the primary fired pixels of the positron tracks in the silicon detector were estimated. The method was tested and assessed for [18F]FDG imaging of an absorbing edge protocol and a leaf sample. The proposed method improved the spatial resolution from 154.6   ±   4.2 µm (energy weighted centroid approximation) to 132.3   ±   3.5 µm in the absorbing edge measurements. For the positron imaging of a leaf sample, the proposed method achieved lower root mean square error relative to phosphor plate imaging, and higher similarity with the reference optical image. The improvements of the preliminary results support further investigation of the proposed algorithm for the enhancement of positron imaging in clinical and preclinical applications.

Spatial optical crosstalk in CMOS image sensors integrated with plasmonic color filters.

PubMed

Yu, Yan; Chen, Qin; Wen, Long; Hu, Xin; Zhang, Hui-Fang

2015-08-24

Imaging resolution of complementary metal oxide semiconductor (CMOS) image sensor (CIS) keeps increasing to approximately 7k × 4k. As a result, the pixel size shrinks down to sub-2μm, which greatly increases the spatial optical crosstalk. Recently, plasmonic color filter was proposed as an alternative to conventional colorant pigmented ones. However, there is little work on its size effect and the spatial optical crosstalk in a model of CIS. By numerical simulation, we investigate the size effect of nanocross array plasmonic color filters and analyze the spatial optical crosstalk of each pixel in a Bayer array of a CIS with a pixel size of 1μm. It is found that the small pixel size deteriorates the filtering performance of nanocross color filters and induces substantial spatial color crosstalk. By integrating the plasmonic filters in the low Metal layer in standard CMOS process, the crosstalk reduces significantly, which is compatible to pigmented filters in a state-of-the-art backside illumination CIS.

Ultra-high spatial resolution multi-energy CT using photon counting detector technology

NASA Astrophysics Data System (ADS)

Leng, S.; Gutjahr, R.; Ferrero, A.; Kappler, S.; Henning, A.; Halaweish, A.; Zhou, W.; Montoya, J.; McCollough, C.

2017-03-01

Two ultra-high-resolution (UHR) imaging modes, each with two energy thresholds, were implemented on a research, whole-body photon-counting-detector (PCD) CT scanner, referred to as sharp and UHR, respectively. The UHR mode has a pixel size of 0.25 mm at iso-center for both energy thresholds, with a collimation of 32 × 0.25 mm. The sharp mode has a 0.25 mm pixel for the low-energy threshold and 0.5 mm for the high-energy threshold, with a collimation of 48 × 0.25 mm. Kidney stones with mixed mineral composition and lung nodules with different shapes were scanned using both modes, and with the standard imaging mode, referred to as macro mode (0.5 mm pixel and 32 × 0.5 mm collimation). Evaluation and comparison of the three modes focused on the ability to accurately delineate anatomic structures using the high-spatial resolution capability and the ability to quantify stone composition using the multi-energy capability. The low-energy threshold images of the sharp and UHR modes showed better shape and texture information due to the achieved higher spatial resolution, although noise was also higher. No noticeable benefit was shown in multi-energy analysis using UHR compared to standard resolution (macro mode) when standard doses were used. This was due to excessive noise in the higher resolution images. However, UHR scans at higher dose showed improvement in multi-energy analysis over macro mode with regular dose. To fully take advantage of the higher spatial resolution in multi-energy analysis, either increased radiation dose, or application of noise reduction techniques, is needed.

Image sensor with high dynamic range linear output

NASA Technical Reports Server (NTRS)

Yadid-Pecht, Orly (Inventor); Fossum, Eric R. (Inventor)

2007-01-01

Designs and operational methods to increase the dynamic range of image sensors and APS devices in particular by achieving more than one integration times for each pixel thereof. An APS system with more than one column-parallel signal chains for readout are described for maintaining a high frame rate in readout. Each active pixel is sampled for multiple times during a single frame readout, thus resulting in multiple integration times. The operation methods can also be used to obtain multiple integration times for each pixel with an APS design having a single column-parallel signal chain for readout. Furthermore, analog-to-digital conversion of high speed and high resolution can be implemented.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kishimoto, S., E-mail: syunji.kishimoto@kek.jp; Haruki, R.; Mitsui, T.

We developed a silicon avalanche photodiode (Si-APD) linear-array detector for use in nuclear resonant scattering experiments using synchrotron X-rays. The Si-APD linear array consists of 64 pixels (pixel size: 100 × 200 μm{sup 2}) with a pixel pitch of 150 μm and depletion depth of 10 μm. An ultrafast frontend circuit allows the X-ray detector to obtain a high output rate of >10{sup 7} cps per pixel. High-performance integrated circuits achieve multichannel scaling over 1024 continuous time bins with a 1 ns resolution for each pixel without dead time. The multichannel scaling method enabled us to record a time spectrummore » of the 14.4 keV nuclear radiation at each pixel with a time resolution of 1.4 ns (FWHM). This method was successfully applied to nuclear forward scattering and nuclear small-angle scattering on {sup 57}Fe.« less

A Nipkow disk integrated with Fresnel lenses for terahertz single pixel imaging.

PubMed

Li, Chong; Grant, James; Wang, Jue; Cumming, David R S

2013-10-21

We present a novel Nipkow disk design for terahertz (THz) single pixel imaging applications. A 100 mm high resistivity (ρ≈3k-10k Ω·cm) silicon wafer was used for the disk on which a spiral array of twelve 16-level binary Fresnel lenses were fabricated using photolithography and a dry-etch process. The implementation of Fresnel lenses on the Nipkow disk increases the THz signal transmission compared to the conventional pinhole-based Nipkow disk by more than 12 times thus a THz source with lower power or a THz detector with lower detectivity can be used. Due to the focusing capability of the lenses, a pixel resolution better than 0.5 mm is in principle achievable. To demonstrate the concept, a single pixel imaging system operating at 2.52 THz is described.

Comparison of Sub-pixel Classification Approaches for Crop-specific Mapping

EPA Science Inventory

The Moderate Resolution Imaging Spectroradiometer (MODIS) data has been increasingly used for crop mapping and other agricultural applications. Phenology-based classification approaches using the NDVI (Normalized Difference Vegetation Index) 16-day composite (250 m) data product...

Investigation of several aspects of LANDSAT 4/5 data quality. [California, Texas, Arkansas, Alabama, and Pacific Ocean

NASA Technical Reports Server (NTRS)

Wrigley, R. C. (Principal Investigator)

1984-01-01

A second quadrant from the Sacramento, CA scene 44/33 acquired by LANDSAT-4 was tested for band to band resolution. Results show that all measured misregistrations are within 0.03 pixels for similar band pairs. Two LANDSAT-5 scenes (one from Corpus Christi, TX and the other from Huntsville, AL) were also tested for band to band resolution. All measured misregistrations in the Texas scene are less than 0.03 pixels. The across scan misregistration Alabama scene is -0.66 pixels and thus needs correction. A 512 x 512 pixel area of the Pacific Ocean was corrected for the pixel offsets. Modulation transfer function analysis of the San Mateo Bridge using data from the San Francisco scene was accomplished.

Double Photon Emission Coincidence Imaging using GAGG-SiPM pixel detectors

NASA Astrophysics Data System (ADS)

Shimazoe, K.; Uenomachi, M.; Mizumachi, Y.; Takahashi, H.; Masao, Y.; Shoji, Y.; Kamada, K.; Yoshikawa, A.

2017-12-01

Single photon emission computed tomography(SPECT) is a useful medical imaging modality using single photon detection from radioactive tracers, such as 99Tc and 111In, however further development of increasing the contrast in the image is still under investigation. A novel method (Double Photon Emission CT / DPECT) using a coincidence detection of two cascade gamma-rays from 111In is proposed and characterized in this study. 111In, which is well-known and commonly used as a SPECT tracer, emits two cascade photons of 171 keV and 245 keV with a short delay of approximately 85 ns. The coincidence detection of two gamma-rays theoretically determines the position in a single point compared with a line in single photon detection and increases the signal to noise ratio drastically. A fabricated pixel detector for this purpose consists of 8 × 8 array of high-resolution type 1.5 mm thickness Ce:GAGG (3.9% @ 662 keV, 6.63g/cm3, C&A Co. Ce:Gd3Ga2.7Al2.3O12 2.5 × 2.5 × 1.5 mm3) crystals coupled a 3 mm pixel SiPM array (Hamamatsu MPPC S13361-2050NS-08). The signal from each pixel is processed and readout using time over threshold (TOT) based parallel processing circuit to extract the energy and timing information. The coincidence was detected by FPGA with the frequency of 400 MHz. Two pixel detectors coupled to parallel-hole collimators are located at the degree of 90 to determine the position and coincidence events (time window =1 μs) are detected and used for making back-projection image. The basic principle of DPECT is characterized including the detection efficiency and timing resolution.

The Speedster-EXD- A New Event-Driven Hybrid CMOS X-ray Detector

NASA Astrophysics Data System (ADS)

Griffith, Christopher V.; Falcone, Abraham D.; Prieskorn, Zachary R.; Burrows, David N.

2016-01-01

The Speedster-EXD is a new 64×64 pixel, 40-μm pixel pitch, 100-μm depletion depth hybrid CMOS x-ray detector with the capability of reading out only those pixels containing event charge, thus enabling fast effective frame rates. A global charge threshold can be specified, and pixels containing charge above this threshold are flagged and read out. The Speedster detector has also been designed with other advanced in-pixel features to improve performance, including a low-noise, high-gain capacitive transimpedance amplifier that eliminates interpixel capacitance crosstalk (IPC), and in-pixel correlated double sampling subtraction to reduce reset noise. We measure the best energy resolution on the Speedster-EXD detector to be 206 eV (3.5%) at 5.89 keV and 172 eV (10.0%) at 1.49 keV. The average IPC to the four adjacent pixels is measured to be 0.25%±0.2% (i.e., consistent with zero). The pixel-to-pixel gain variation is measured to be 0.80%±0.03%, and a Monte Carlo simulation is applied to better characterize the contributions to the energy resolution.

Cosmological parameters from a re-analysis of the WMAP 7 year low-resolution maps

NASA Astrophysics Data System (ADS)

Finelli, F.; De Rosa, A.; Gruppuso, A.; Paoletti, D.

2013-06-01

Cosmological parameters from Wilkinson Microwave Anisotropy Probe (WMAP) 7 year data are re-analysed by substituting a pixel-based likelihood estimator to the one delivered publicly by the WMAP team. Our pixel-based estimator handles exactly intensity and polarization in a joint manner, allowing us to use low-resolution maps and noise covariance matrices in T, Q, U at the same resolution, which in this work is 3.6°. We describe the features and the performances of the code implementing our pixel-based likelihood estimator. We perform a battery of tests on the application of our pixel-based likelihood routine to WMAP publicly available low-resolution foreground-cleaned products, in combination with the WMAP high-ℓ likelihood, reporting the differences on cosmological parameters evaluated by the full WMAP likelihood public package. The differences are not only due to the treatment of polarization, but also to the marginalization over monopole and dipole uncertainties present in the WMAP pixel likelihood code for temperature. The credible central value for the cosmological parameters change below the 1σ level with respect to the evaluation by the full WMAP 7 year likelihood code, with the largest difference in a shift to smaller values of the scalar spectral index nS.

Mars Exploration Rover engineering cameras

USGS Publications Warehouse

Maki, J.N.; Bell, J.F.; Herkenhoff, K. E.; Squyres, S. W.; Kiely, A.; Klimesh, M.; Schwochert, M.; Litwin, T.; Willson, R.; Johnson, Aaron H.; Maimone, M.; Baumgartner, E.; Collins, A.; Wadsworth, M.; Elliot, S.T.; Dingizian, A.; Brown, D.; Hagerott, E.C.; Scherr, L.; Deen, R.; Alexander, D.; Lorre, J.

2003-01-01

NASA's Mars Exploration Rover (MER) Mission will place a total of 20 cameras (10 per rover) onto the surface of Mars in early 2004. Fourteen of the 20 cameras are designated as engineering cameras and will support the operation of the vehicles on the Martian surface. Images returned from the engineering cameras will also be of significant importance to the scientific community for investigative studies of rock and soil morphology. The Navigation cameras (Navcams, two per rover) are a mast-mounted stereo pair each with a 45?? square field of view (FOV) and an angular resolution of 0.82 milliradians per pixel (mrad/pixel). The Hazard Avoidance cameras (Hazcams, four per rover) are a body-mounted, front- and rear-facing set of stereo pairs, each with a 124?? square FOV and an angular resolution of 2.1 mrad/pixel. The Descent camera (one per rover), mounted to the lander, has a 45?? square FOV and will return images with spatial resolutions of ???4 m/pixel. All of the engineering cameras utilize broadband visible filters and 1024 x 1024 pixel detectors. Copyright 2003 by the American Geophysical Union.

Camera system resolution and its influence on digital image correlation

DOE PAGES

Reu, Phillip L.; Sweatt, William; Miller, Timothy; ...

2014-09-21

Digital image correlation (DIC) uses images from a camera and lens system to make quantitative measurements of the shape, displacement, and strain of test objects. This increasingly popular method has had little research on the influence of the imaging system resolution on the DIC results. This paper investigates the entire imaging system and studies how both the camera and lens resolution influence the DIC results as a function of the system Modulation Transfer Function (MTF). It will show that when making spatial resolution decisions (including speckle size) the resolution limiting component should be considered. A consequence of the loss ofmore » spatial resolution is that the DIC uncertainties will be increased. This is demonstrated using both synthetic and experimental images with varying resolution. The loss of image resolution and DIC accuracy can be compensated for by increasing the subset size, or better, by increasing the speckle size. The speckle-size and spatial resolution are now a function of the lens resolution rather than the more typical assumption of the pixel size. The study will demonstrate the tradeoffs associated with limited lens resolution.« less

Sub-pixel flood inundation mapping from multispectral remotely sensed images based on discrete particle swarm optimization

NASA Astrophysics Data System (ADS)

Li, Linyi; Chen, Yun; Yu, Xin; Liu, Rui; Huang, Chang

2015-03-01

The study of flood inundation is significant to human life and social economy. Remote sensing technology has provided an effective way to study the spatial and temporal characteristics of inundation. Remotely sensed images with high temporal resolutions are widely used in mapping inundation. However, mixed pixels do exist due to their relatively low spatial resolutions. One of the most popular approaches to resolve this issue is sub-pixel mapping. In this paper, a novel discrete particle swarm optimization (DPSO) based sub-pixel flood inundation mapping (DPSO-SFIM) method is proposed to achieve an improved accuracy in mapping inundation at a sub-pixel scale. The evaluation criterion for sub-pixel inundation mapping is formulated. The DPSO-SFIM algorithm is developed, including particle discrete encoding, fitness function designing and swarm search strategy. The accuracy of DPSO-SFIM in mapping inundation at a sub-pixel scale was evaluated using Landsat ETM + images from study areas in Australia and China. The results show that DPSO-SFIM consistently outperformed the four traditional SFIM methods in these study areas. A sensitivity analysis of DPSO-SFIM was also carried out to evaluate its performances. It is hoped that the results of this study will enhance the application of medium-low spatial resolution images in inundation detection and mapping, and thereby support the ecological and environmental studies of river basins.

Hyperspectral imaging using the single-pixel Fourier transform technique

NASA Astrophysics Data System (ADS)

Jin, Senlin; Hui, Wangwei; Wang, Yunlong; Huang, Kaicheng; Shi, Qiushuai; Ying, Cuifeng; Liu, Dongqi; Ye, Qing; Zhou, Wenyuan; Tian, Jianguo

2017-03-01

Hyperspectral imaging technology is playing an increasingly important role in the fields of food analysis, medicine and biotechnology. To improve the speed of operation and increase the light throughput in a compact equipment structure, a Fourier transform hyperspectral imaging system based on a single-pixel technique is proposed in this study. Compared with current imaging spectrometry approaches, the proposed system has a wider spectral range (400-1100 nm), a better spectral resolution (1 nm) and requires fewer measurement data (a sample rate of 6.25%). The performance of this system was verified by its application to the non-destructive testing of potatoes.

Limits in point to point resolution of MOS based pixels detector arrays

NASA Astrophysics Data System (ADS)

Fourches, N.; Desforge, D.; Kebbiri, M.; Kumar, V.; Serruys, Y.; Gutierrez, G.; Leprêtre, F.; Jomard, F.

2018-01-01

In high energy physics point-to-point resolution is a key prerequisite for particle detector pixel arrays. Current and future experiments require the development of inner-detectors able to resolve the tracks of particles down to the micron range. Present-day technologies, although not fully implemented in actual detectors, can reach a 5-μm limit, this limit being based on statistical measurements, with a pixel-pitch in the 10 μm range. This paper is devoted to the evaluation of the building blocks for use in pixel arrays enabling accurate tracking of charged particles. Basing us on simulations we will make here a quantitative evaluation of the physical and technological limits in pixel size. Attempts to design small pixels based on SOI technology will be briefly recalled here. A design based on CMOS compatible technologies that allow a reduction of the pixel size below the micrometer is introduced here. Its physical principle relies on a buried carrier-localizing collecting gate. The fabrication process needed by this pixel design can be based on existing process steps used in silicon microelectronics. The pixel characteristics will be discussed as well as the design of pixel arrays. The existing bottlenecks and how to overcome them will be discussed in the light of recent ion implantation and material characterization experiments.

Laboratory and testbeam results for thin and epitaxial planar sensors for HL-LHC

DOE PAGES

Bubna, M.; Bolla, G.; Bortoletto, D.; ...

2015-08-03

The High-Luminosity LHC (HL-LHC) upgrade of the CMS pixel detector will require the development of novel pixel sensors which can withstand the increase in instantaneous luminosity to L = 5 × 10 34 cm –2s –1 and collect ~ 3000fb –1 of data. The innermost layer of the pixel detector will be exposed to doses of about 10 16 n eq/ cm 2. Hence, new pixel sensors with improved radiation hardness need to be investigated. A variety of silicon materials (Float-zone, Magnetic Czochralski and Epitaxially grown silicon), with thicknesses from 50 μm to 320 μm in p-type and n-type substrates have beenmore » fabricated using single-sided processing. The effect of reducing the sensor active thickness to improve radiation hardness by using various techniques (deep diffusion, wafer thinning, or growing epitaxial silicon on a handle wafer) has been studied. Furthermore, the results for electrical characterization, charge collection efficiency, and position resolution of various n-on-p pixel sensors with different substrates and different pixel geometries (different bias dot gaps and pixel implant sizes) will be presented.« less

Challenges of small-pixel infrared detectors: a review.

PubMed

Rogalski, A; Martyniuk, P; Kopytko, M

2016-04-01

In the last two decades, several new concepts for improving the performance of infrared detectors have been proposed. These new concepts particularly address the drive towards the so-called high operating temperature focal plane arrays (FPAs), aiming to increase detector operating temperatures, and as a consequence reduce the cost of infrared systems. In imaging systems with the above megapixel formats, pixel dimension plays a crucial role in determining critical system attributes such as system size, weight and power consumption (SWaP). The advent of smaller pixels has also resulted in the superior spatial and temperature resolution of these systems. Optimum pixel dimensions are limited by diffraction effects from the aperture, and are in turn wavelength-dependent. In this paper, the key challenges in realizing optimum pixel dimensions in FPA design including dark current, pixel hybridization, pixel delineation, and unit cell readout capacity are outlined to achieve a sufficiently adequate modulation transfer function for the ultra-small pitches involved. Both photon and thermal detectors have been considered. Concerning infrared photon detectors, the trade-offs between two types of competing technology-HgCdTe material systems and III-V materials (mainly barrier detectors)-have been investigated.

Mapping of the Culann-Tohil Region of Io

NASA Technical Reports Server (NTRS)

Turtle, E. P.; Keszthelyi, L. P.; Jaeger, W. L.; Radebaugh, J.; Milazzo, M. P.; McEwen, A. S.; Moore, J. M.; Schenk, P. M.; Lopes, R. M. C.

2003-01-01

The Galileo spacecraft completed its observations of Jupiter's volcanic moon Io in October 2001 with the orbit I32 flyby, during which new local (13-55 m/pixel) and regional (130-400 m/pixel) resolution images and spectroscopic data were returned of the antijovian hemisphere. We have combined a I32 regional mosaic (330 m/pixel) with lower-resolution C21 color data (1.4 km/pixel, Figure 1) and produced a geomorphologic map of the Culann-Tohil area of this hemisphere. Here we present the geologic features, map units, and structures in this region, and give preliminary conclusions about geologic activity for comparison with other regions to better understand Io's geologic evolution.

Chandra ACIS Sub-pixel Resolution

NASA Astrophysics Data System (ADS)

Kim, Dong-Woo; Anderson, C. S.; Mossman, A. E.; Allen, G. E.; Fabbiano, G.; Glotfelty, K. J.; Karovska, M.; Kashyap, V. L.; McDowell, J. C.

2011-05-01

We investigate how to achieve the best possible ACIS spatial resolution by binning in ACIS sub-pixel and applying an event repositioning algorithm after removing pixel-randomization from the pipeline data. We quantitatively assess the improvement in spatial resolution by (1) measuring point source sizes and (2) detecting faint point sources. The size of a bright (but no pile-up), on-axis point source can be reduced by about 20-30%. With the improve resolution, we detect 20% more faint sources when embedded on the extended, diffuse emission in a crowded field. We further discuss the false source rate of about 10% among the newly detected sources, using a few ultra-deep observations. We also find that the new algorithm does not introduce a grid structure by an aliasing effect for dithered observations and does not worsen the positional accuracy

Organic-on-silicon complementary metal-oxide-semiconductor colour image sensors.

PubMed

Lim, Seon-Jeong; Leem, Dong-Seok; Park, Kyung-Bae; Kim, Kyu-Sik; Sul, Sangchul; Na, Kyoungwon; Lee, Gae Hwang; Heo, Chul-Joon; Lee, Kwang-Hee; Bulliard, Xavier; Satoh, Ryu-Ichi; Yagi, Tadao; Ro, Takkyun; Im, Dongmo; Jung, Jungkyu; Lee, Myungwon; Lee, Tae-Yon; Han, Moon Gyu; Jin, Yong Wan; Lee, Sangyoon

2015-01-12

Complementary metal-oxide-semiconductor (CMOS) colour image sensors are representative examples of light-detection devices. To achieve extremely high resolutions, the pixel sizes of the CMOS image sensors must be reduced to less than a micron, which in turn significantly limits the number of photons that can be captured by each pixel using silicon (Si)-based technology (i.e., this reduction in pixel size results in a loss of sensitivity). Here, we demonstrate a novel and efficient method of increasing the sensitivity and resolution of the CMOS image sensors by superposing an organic photodiode (OPD) onto a CMOS circuit with Si photodiodes, which consequently doubles the light-input surface area of each pixel. To realise this concept, we developed organic semiconductor materials with absorption properties selective to green light and successfully fabricated highly efficient green-light-sensitive OPDs without colour filters. We found that such a top light-receiving OPD, which is selective to specific green wavelengths, demonstrates great potential when combined with a newly designed Si-based CMOS circuit containing only blue and red colour filters. To demonstrate the effectiveness of this state-of-the-art hybrid colour image sensor, we acquired a real full-colour image using a camera that contained the organic-on-Si hybrid CMOS colour image sensor.

Organic-on-silicon complementary metal–oxide–semiconductor colour image sensors

PubMed Central

Lim, Seon-Jeong; Leem, Dong-Seok; Park, Kyung-Bae; Kim, Kyu-Sik; Sul, Sangchul; Na, Kyoungwon; Lee, Gae Hwang; Heo, Chul-Joon; Lee, Kwang-Hee; Bulliard, Xavier; Satoh, Ryu-Ichi; Yagi, Tadao; Ro, Takkyun; Im, Dongmo; Jung, Jungkyu; Lee, Myungwon; Lee, Tae-Yon; Han, Moon Gyu; Jin, Yong Wan; Lee, Sangyoon

2015-01-01

Complementary metal–oxide–semiconductor (CMOS) colour image sensors are representative examples of light-detection devices. To achieve extremely high resolutions, the pixel sizes of the CMOS image sensors must be reduced to less than a micron, which in turn significantly limits the number of photons that can be captured by each pixel using silicon (Si)-based technology (i.e., this reduction in pixel size results in a loss of sensitivity). Here, we demonstrate a novel and efficient method of increasing the sensitivity and resolution of the CMOS image sensors by superposing an organic photodiode (OPD) onto a CMOS circuit with Si photodiodes, which consequently doubles the light-input surface area of each pixel. To realise this concept, we developed organic semiconductor materials with absorption properties selective to green light and successfully fabricated highly efficient green-light-sensitive OPDs without colour filters. We found that such a top light-receiving OPD, which is selective to specific green wavelengths, demonstrates great potential when combined with a newly designed Si-based CMOS circuit containing only blue and red colour filters. To demonstrate the effectiveness of this state-of-the-art hybrid colour image sensor, we acquired a real full-colour image using a camera that contained the organic-on-Si hybrid CMOS colour image sensor. PMID:25578322

Resolution Enhancement of MODIS-derived Water Indices for Studying Persistent Flooding

NASA Astrophysics Data System (ADS)

Underwood, L. W.; Kalcic, M. T.; Fletcher, R. M.

2012-12-01

Monitoring coastal marshes for persistent flooding and salinity stress is a high priority issue in Louisiana. Remote sensing can identify environmental variables that can be indicators of marsh habitat conditions, and offer timely and relatively accurate information for aiding wetland vegetation management. Monitoring activity accuracy is often limited by mixed pixels which occur when areas represented by the pixel encompasses more than one cover type. Mixtures of marsh grasses and open water in 250m Moderate Resolution Imaging Spectroradiometer (MODIS) data can impede flood area estimation. Flood mapping of such mixtures requires finer spatial resolution data to better represent the cover type composition within 250m MODIS pixel. Fusion of MODIS and Landsat can improve both spectral and temporal resolution of time series products to resolve rapid changes from forcing mechanisms like hurricane winds and storm surge. For this study, using a method for estimating sub-pixel values from a MODIS time series of a Normalized Difference Water Index (NDWI), using temporal weighting, was implemented to map persistent flooding in Louisiana coastal marshes. Ordinarily NDWI computed from daily 250m MODIS pixels represents a mixture of fragmented marshes and water. Here, sub-pixel NDWI values were derived for MODIS data using Landsat 30-m data. Each MODIS pixel was disaggregated into a mixture of the eight cover types according to the classified image pixels falling inside the MODIS pixel. The Landsat pixel means for each cover type inside a MODIS pixel were computed for the Landsat data preceding the MODIS image in time and for the Landsat data succeeding the MODIS image. The Landsat data were then weighted exponentially according to closeness in date to the MODIS data. The reconstructed MODIS data were produced by summing the product of fractional cover type with estimated NDWI values within each cover type. A new daily time series was produced using both the reconstructed 250-m MODIS, with enhanced features, and the approximated daily 30-m high-resolution image based on Landsat data. The algorithm was developed and tested over the Calcasieu-Sabine Basin, which was heavily inundated by storm surge from Hurricane Ike to study the extent and duration of flooding following the storm. Time series for 2000-2009, covering flooding events by Hurricane Rita in 2005 and Hurricane Ike in 2008, were derived. High resolution images were formed for all days in 2008 between the first cloud free Landsat scene and the last cloud-free Landsat scene. To refine and validate flooding maps, each time series was compared to Louisiana Coastwide Reference Monitoring System (CRMS) station water levels adjusted to marsh to optimize thresholds for MODIS-derived time series of NDWI. Seasonal fluctuations were adjusted by subtracting ten year average NDWI for marshes, excluding the hurricane events. Results from different NDWI indices and a combination of indices were compared. Flooding persistence that was mapped with higher-resolution data showed some improvement over the original MODIS time series estimates. The advantage of this novel technique is that improved mapping of extent and duration of inundation can be provided.

Resolution Enhancement of MODIS-Derived Water Indices for Studying Persistent Flooding

NASA Technical Reports Server (NTRS)

Underwood, L. W.; Kalcic, Maria; Fletcher, Rose

2012-01-01

Monitoring coastal marshes for persistent flooding and salinity stress is a high priority issue in Louisiana. Remote sensing can identify environmental variables that can be indicators of marsh habitat conditions, and offer timely and relatively accurate information for aiding wetland vegetation management. Monitoring activity accuracy is often limited by mixed pixels which occur when areas represented by the pixel encompasses more than one cover type. Mixtures of marsh grasses and open water in 250m Moderate Resolution Imaging Spectroradiometer (MODIS) data can impede flood area estimation. Flood mapping of such mixtures requires finer spatial resolution data to better represent the cover type composition within 250m MODIS pixel. Fusion of MODIS and Landsat can improve both spectral and temporal resolution of time series products to resolve rapid changes from forcing mechanisms like hurricane winds and storm surge. For this study, using a method for estimating sub-pixel values from a MODIS time series of a Normalized Difference Water Index (NDWI), using temporal weighting, was implemented to map persistent flooding in Louisiana coastal marshes. Ordinarily NDWI computed from daily 250m MODIS pixels represents a mixture of fragmented marshes and water. Here, sub-pixel NDWI values were derived for MODIS data using Landsat 30-m data. Each MODIS pixel was disaggregated into a mixture of the eight cover types according to the classified image pixels falling inside the MODIS pixel. The Landsat pixel means for each cover type inside a MODIS pixel were computed for the Landsat data preceding the MODIS image in time and for the Landsat data succeeding the MODIS image. The Landsat data were then weighted exponentially according to closeness in date to the MODIS data. The reconstructed MODIS data were produced by summing the product of fractional cover type with estimated NDWI values within each cover type. A new daily time series was produced using both the reconstructed 250-m MODIS, with enhanced features, and the approximated daily 30-m high-resolution image based on Landsat data. The algorithm was developed and tested over the Calcasieu-Sabine Basin, which was heavily inundated by storm surge from Hurricane Ike to study the extent and duration of flooding following the storm. Time series for 2000-2009, covering flooding events by Hurricane Rita in 2005 and Hurricane Ike in 2008, were derived. High resolution images were formed for all days in 2008 between the first cloud free Landsat scene and the last cloud-free Landsat scene. To refine and validate flooding maps, each time series was compared to Louisiana Coastwide Reference Monitoring System (CRMS) station water levels adjusted to marsh to optimize thresholds for MODIS-derived time series of NDWI. Seasonal fluctuations were adjusted by subtracting ten year average NDWI for marshes, excluding the hurricane events. Results from different NDWI indices and a combination of indices were compared. Flooding persistence that was mapped with higher-resolution data showed some improvement over the original MODIS time series estimates. The advantage of this novel technique is that improved mapping of extent and duration of inundation can be provided.

LSA SAF Meteosat FRP Products: Part 2 - Evaluation and demonstration of use in the Copernicus Atmosphere Monitoring Service (CAMS)

NASA Astrophysics Data System (ADS)

Roberts, G.; Wooster, M. J.; Xu, W.; Freeborn, P. H.; Morcrette, J.-J.; Jones, L.; Benedetti, A.; Kaiser, J.

2015-06-01

Characterising the dynamics of landscape scale wildfires at very high temporal resolutions is best achieved using observations from Earth Observation (EO) sensors mounted onboard geostationary satellites. As a result, a number of operational active fire products have been developed from the data of such sensors. An example of which are the Fire Radiative Power (FRP) products, the FRP-PIXEL and FRP-GRID products, generated by the Land Surface Analysis Satellite Applications Facility (LSA SAF) from imagery collected by the Spinning Enhanced Visible and Infrared Imager (SEVIRI) on-board the Meteosat Second Generation (MSG) series of geostationary EO satellites. The processing chain developed to deliver these FRP products detects SEVIRI pixels containing actively burning fires and characterises their FRP output across four geographic regions covering Europe, part of South America and northern and southern Africa. The FRP-PIXEL product contains the highest spatial and temporal resolution FRP dataset, whilst the FRP-GRID product contains a spatio-temporal summary that includes bias adjustments for cloud cover and the non-detection of low FRP fire pixels. Here we evaluate these two products against active fire data collected by the Moderate Resolution Imaging Spectroradiometer (MODIS), and compare the results to those for three alternative active fire products derived from SEVIRI imagery. The FRP-PIXEL product is shown to detect a substantially greater number of active fire pixels than do alternative SEVIRI-based products, and comparison to MODIS on a per-fire basis indicates a strong agreement and low bias in terms of FRP values. However, low FRP fire pixels remain undetected by SEVIRI, with errors of active fire pixel detection commission and omission compared to MODIS ranging between 9-13 and 65-77% respectively in Africa. Higher errors of omission result in greater underestimation of regional FRP totals relative to those derived from simultaneously collected MODIS data, ranging from 35% over the Northern Africa region to 89% over the European region. High errors of active fire omission and FRP underestimation are found over Europe and South America, and result from SEVIRI's larger pixel area over these regions. An advantage of using FRP for characterising wildfire emissions is the ability to do so very frequently and in near real time (NRT). To illustrate the potential of this approach, wildfire fuel consumption rates derived from the SEVIRI FRP-PIXEL product are used to characterise smoke emissions of the 2007 Peloponnese wildfires within the European Centre for Medium-Range Weather Forecasting (ECMWF) Integrated Forecasting System (IFS), as a demonstration of what can be achieved when using geostationary active fire data within the Copernicus Atmosphere Monitoring System (CAMS). Qualitative comparison of the modelled smoke plumes with MODIS optical imagery illustrates that the model captures the temporal and spatial dynamics of the plume very well, and that high temporal resolution emissions estimates such as those available from geostationary orbit are important for capturing the sub-daily variability in smoke plume parameters such as aerosol optical depth (AOD), which are increasingly less well resolved using daily or coarser temporal resolution emissions datasets. Quantitative comparison of modelled AOD with coincident MODIS and AERONET AOD indicates that the former is overestimated by ∼ 20-30%, but captures the observed AOD dynamics with a high degree of fidelity. The case study highlights the potential of using geostationary FRP data to drive fire emissions estimates for use within atmospheric transport models such as those currently implemented as part of the Monitoring Atmospheric Composition and Climate (MACC) programme within the CAMS.

Reconstruction of 2D PET data with Monte Carlo generated system matrix for generalized natural pixels

NASA Astrophysics Data System (ADS)

Vandenberghe, Stefaan; Staelens, Steven; Byrne, Charles L.; Soares, Edward J.; Lemahieu, Ignace; Glick, Stephen J.

2006-06-01

In discrete detector PET, natural pixels are image basis functions calculated from the response of detector pairs. By using reconstruction with natural pixel basis functions, the discretization of the object into a predefined grid can be avoided. Here, we propose to use generalized natural pixel reconstruction. Using this approach, the basis functions are not the detector sensitivity functions as in the natural pixel case but uniform parallel strips. The backprojection of the strip coefficients results in the reconstructed image. This paper proposes an easy and efficient way to generate the matrix M directly by Monte Carlo simulation. Elements of the generalized natural pixel system matrix are formed by calculating the intersection of a parallel strip with the detector sensitivity function. These generalized natural pixels are easier to use than conventional natural pixels because the final step from solution to a square pixel representation is done by simple backprojection. Due to rotational symmetry in the PET scanner, the matrix M is block circulant and only the first blockrow needs to be stored. Data were generated using a fast Monte Carlo simulator using ray tracing. The proposed method was compared to a listmode MLEM algorithm, which used ray tracing for doing forward and backprojection. Comparison of the algorithms with different phantoms showed that an improved resolution can be obtained using generalized natural pixel reconstruction with accurate system modelling. In addition, it was noted that for the same resolution a lower noise level is present in this reconstruction. A numerical observer study showed the proposed method exhibited increased performance as compared to a standard listmode EM algorithm. In another study, more realistic data were generated using the GATE Monte Carlo simulator. For these data, a more uniform contrast recovery and a better contrast-to-noise performance were observed. It was observed that major improvements in contrast recovery were obtained with MLEM when the correct system matrix was used instead of simple ray tracing. The correct modelling was the major cause of improved contrast for the same background noise. Less important factors were the choice of the algorithm (MLEM performed better than ART) and the basis functions (generalized natural pixels gave better results than pixels).

Controlled power delivery for super-resolution imaging of biological samples using digital micromirror device

NASA Astrophysics Data System (ADS)

Valiya Peedikakkal, Liyana; Cadby, Ashley

2017-02-01

Localization based super resolution images of a biological sample is generally achieved by using high power laser illumination with long exposure time which unfortunately increases photo-toxicity of a sample, making super resolution microscopy, in general, incompatible with live cell imaging. Furthermore, the limitation of photobleaching reduces the ability to acquire time lapse images of live biological cells using fluorescence microscopy. Digital Light Processing (DLP) technology can deliver light at grey scale levels by flickering digital micromirrors at around 290 Hz enabling highly controlled power delivery to samples. In this work, Digital Micromirror Device (DMD) is implemented in an inverse Schiefspiegler telescope setup to control the power and pattern of illumination for super resolution microscopy. We can achieve spatial and temporal patterning of illumination by controlling the DMD pixel by pixel. The DMD allows us to control the power and spatial extent of the laser illumination. We have used this to show that we can reduce the power delivered to the sample to allow for longer time imaging in one area while achieving sub-diffraction STORM imaging in another using higher power densities.

Applying ECOSTRESS Diurnal Cycle Land Surface Temperature and Evapotranspiration to Agricultural Soil and Water Management

NASA Astrophysics Data System (ADS)

Pestana, S. J.; Halverson, G. H.; Barker, M.; Cooley, S.

2016-12-01

Increased demand for agricultural products and limited water supplies in Guanacaste, Costa Rica have encouraged the improvement of water management practices to increase resource use efficiency. Remotely sensed evapotranspiration (ET) data can contribute by providing insights into variables like crop health and water loss, as well as better inform the use of various irrigation techniques. EARTH University currently collects data in the region that are limited to costly and time-intensive in situ observations and will greatly benefit from the expanded spatial and temporal resolution of remote sensing measurements from the ECOsystem Spaceborne Thermal Radiometer Experiment on Space Station (ECOSTRESS). In this project, Moderate Resolution Imaging Spectroradiometer (MODIS) Priestly-Taylor Jet Propulsion Laboratory (PT-JPL) data, with a resolution of 5 km per pixel, was used to demonstrate to our partners at EARTH University the application of remotely sensed ET measurements. An experimental design was developed to provide a method of applying future ECOSTRESS data, at the higher resolution of 70 m per pixel, to research in managing and implementing sustainable farm practices. Our investigation of the diurnal cycle of land surface temperature, net radiation, and evapotranspiration will advance the model science for ECOSTRESS, which will be launched in 2018 and installed on the International Space Station.

The Advanced ACTPol 27/39 GHz Array

NASA Astrophysics Data System (ADS)

Simon, S. M.; Beall, J. A.; Cothard, N. F.; Duff, S. M.; Gallardo, P. A.; Ho, S. P.; Hubmayr, J.; Koopman, B. J.; McMahon, J. J.; Nati, F.; Niemack, M. D.; Staggs, S. T.; Vavagiakis, E. M.; Wollack, E. J.

2018-05-01

Advanced ACTPol (AdvACT) will observe the temperature and polarization of the cosmic microwave background (CMB) at multiple frequencies and high resolution to place improved constraints on inflation, dark matter, and dark energy. Foregrounds from synchrotron and dust radiation are a source of contamination that must be characterized and removed across a wide range of frequencies. AdvACT will thus observe at five frequency bands from 27 to 230 GHz. We discuss the design of the pixels and feedhorns for the 27/39 GHz multichroic array for AdvACT, which will target the synchrotron radiation that dominates at these frequencies. To gain 35% in mapping speed in the 39 GHz band where the foreground signals are faintest, the pixel number was increased through reducing the pixel diameter to 1.08λ at the lowest frequency, which represents a 22% decrease in size compared to our previously most tightly packed pixels.

Recent X-ray hybrid CMOS detector developments and measurements

NASA Astrophysics Data System (ADS)

Hull, Samuel V.; Falcone, Abraham D.; Burrows, David N.; Wages, Mitchell; Chattopadhyay, Tanmoy; McQuaide, Maria; Bray, Evan; Kern, Matthew

2017-08-01

The Penn State X-ray detector lab, in collaboration with Teledyne Imaging Sensors (TIS), have progressed their efforts to improve soft X-ray Hybrid CMOS detector (HCD) technology on multiple fronts. Having newly acquired a Teledyne cryogenic SIDECARTM ASIC for use with HxRG devices, measurements were performed with an H2RG HCD and the cooled SIDECARTM. We report new energy resolution and read noise measurements, which show a significant improvement over room temperature SIDECARTM operation. Further, in order to meet the demands of future high-throughput and high spatial resolution X-ray observatories, detectors with fast readout and small pixel sizes are being developed. We report on characteristics of new X-ray HCDs with 12.5 micron pitch that include in-pixel CDS circuitry and crosstalk-eliminating CTIA amplifiers. In addition, PSU and TIS are developing a new large-scale array Speedster-EXD device. The original 64 × 64 pixel Speedster-EXD prototype used comparators in each pixel to enable event driven readout with order of magnitude higher effective readout rates, which will now be implemented in a 550 × 550 pixel device. Finally, the detector lab is involved in a sounding rocket mission that is slated to fly in 2018 with an off-plane reflection grating array and an H2RG X-ray HCD. We report on the planned detector configuration for this mission, which will increase the NASA technology readiness level of X-ray HCDs to TRL 9.

Energy-correction photon counting pixel for photon energy extraction under pulse pile-up

NASA Astrophysics Data System (ADS)

Lee, Daehee; Park, Kyungjin; Lim, Kyung Taek; Cho, Gyuseong

2017-06-01

A photon counting detector (PCD) has been proposed as an alternative solution to an energy-integrating detector (EID) in medical imaging field due to its high resolution, high efficiency, and low noise. The PCD has expanded to variety of fields such as spectral CT, k-edge imaging, and material decomposition owing to its capability to count and measure the number and the energy of an incident photon, respectively. Nonetheless, pulse pile-up, which is a superimposition of pulses at the output of a charge sensitive amplifier (CSA) in each PC pixel, occurs frequently as the X-ray flux increases due to the finite pulse processing time (PPT) in CSAs. Pulse pile-up induces not only a count loss but also distortion in the measured X-ray spectrum from each PC pixel and thus it is a main constraint on the use of PCDs in high flux X-ray applications. To minimize these effects, an energy-correction PC (ECPC) pixel is proposed to resolve pulse pile-up without cutting off the PPT by adding an energy correction logic (ECL) via a cross detection method (CDM). The ECPC pixel with a size of 200×200 μm2 was fabricated by using a 6-metal 1-poly 0.18 μm CMOS process with a static power consumption of 7.2 μW/pixel. The maximum count rate of the ECPC pixel was extended by approximately three times higher than that of a conventional PC pixel with a PPT of 500 nsec. The X-ray spectrum of 90 kVp, filtered by 3 mm Al filter, was measured as the X-ray current was increased using the CdTe and the ECPC pixel. As a result, the ECPC pixel dramatically reduced the energy spectrum distortion at 2 Mphotons/pixel/s when compared to that of the ERCP pixel with the same 500 nsec PPT.

A high-resolution and intelligent dead pixel detection scheme for an electrowetting display screen

NASA Astrophysics Data System (ADS)

Luo, ZhiJie; Luo, JianKun; Zhao, WenWen; Cao, Yang; Lin, WeiJie; Zhou, GuoFu

2018-02-01

Electrowetting display technology is realized by tuning the surface energy of a hydrophobic surface by applying a voltage based on electrowetting mechanism. With the rapid development of the electrowetting industry, how to analyze efficiently the quality of an electrowetting display screen has a very important significance. There are two kinds of dead pixels on the electrowetting display screen. One is that the oil of pixel cannot completely cover the display area. The other is that indium tin oxide semiconductor wire connecting pixel and foil was burned. In this paper, we propose a high-resolution and intelligent dead pixel detection scheme for an electrowetting display screen. First, we built an aperture ratio-capacitance model based on the electrical characteristics of electrowetting display. A field-programmable gate array is used as the integrated logic hub of the system for a highly reliable and efficient control of the circuit. Dead pixels can be detected and displayed on a PC-based 2D graphical interface in real time. The proposed dead pixel detection scheme reported in this work has promise in automating electrowetting display experiments.

New Optimizations of Microcalorimeter Arrays for High-Resolution Imaging X-ray Spectroscopy

NASA Astrophysics Data System (ADS)

Kilbourne, Caroline

We propose to continue our successful research program in developing arrays of superconducting transition-edge sensors (TES) for x-ray astrophysics. Our standard 0.3 mm TES pixel achieves better than 2.5-eV resolution, and we now make 32x32 arrays of such pixels. We have also achieved better than 1-eV resolution in smaller pixels, and promising performance in a range of position-sensitive designs. We propose to continue to advance the designs of both the single-pixel and position-sensitive microcalorimeters so that we can produce arrays suitable for several x-ray spectroscopy observatories presently in formulation. We will also investigate various array and pixel optimizations such as would be needed for large arrays for surveys, large- pixel arrays for diffuse soft x-ray measurements, or sub-arrays of fast pixels optimized for neutron-star burst spectroscopy. In addition, we will develop fabrication processes for integrating sub-arrays with very different pixel designs into a monolithic focal-plane array to simplify the design of the focal-plane assembly and make feasible new detector configurations such as the one currently baselined for AXSIO. Through a series of measurements on test devices, we have improved our understanding of the weak-link physics governing the observed resistive transitions in TES detectors. We propose to build on that work and ultimately use the results to improve the immunity of the detector to environmental magnetic fields, as well as its fundamental performance, in each of the targeted optimizations we are developing.

A patch-based convolutional neural network for remote sensing image classification.

PubMed

Sharma, Atharva; Liu, Xiuwen; Yang, Xiaojun; Shi, Di

2017-11-01

Availability of accurate land cover information over large areas is essential to the global environment sustainability; digital classification using medium-resolution remote sensing data would provide an effective method to generate the required land cover information. However, low accuracy of existing per-pixel based classification methods for medium-resolution data is a fundamental limiting factor. While convolutional neural networks (CNNs) with deep layers have achieved unprecedented improvements in object recognition applications that rely on fine image structures, they cannot be applied directly to medium-resolution data due to lack of such fine structures. In this paper, considering the spatial relation of a pixel to its neighborhood, we propose a new deep patch-based CNN system tailored for medium-resolution remote sensing data. The system is designed by incorporating distinctive characteristics of medium-resolution data; in particular, the system computes patch-based samples from multidimensional top of atmosphere reflectance data. With a test site from the Florida Everglades area (with a size of 771 square kilometers), the proposed new system has outperformed pixel-based neural network, pixel-based CNN and patch-based neural network by 24.36%, 24.23% and 11.52%, respectively, in overall classification accuracy. By combining the proposed deep CNN and the huge collection of medium-resolution remote sensing data, we believe that much more accurate land cover datasets can be produced over large areas. Copyright © 2017 Elsevier Ltd. All rights reserved.

Resolution studies with the DATURA beam telescope

NASA Astrophysics Data System (ADS)

Jansen, H.

2016-12-01

Detailed studies of the resolution of a EUDET-type beam telescope are carried out using the DATURA beam telescope as an example. The EUDET-type beam telescopes make use of CMOS MIMOSA 26 pixel detectors for particle tracking allowing for precise characterisation of particle-sensing devices. A profound understanding of the performance of the beam telescope as a whole is obtained by a detailed characterisation of the sensors themselves. The differential intrinsic resolution as measured in a MIMOSA 26 sensor is extracted using an iterative pull method, and various quantities that depend on the size of the cluster produced by a traversing charged particle are discussed: the residual distribution, the intra-pixel residual-width distribution and the intra-pixel density distribution of track incident positions.

Discovery of Finely Structured Dynamic Solar Corona Observed in the Hi-C Telescope

NASA Technical Reports Server (NTRS)

Winebarger, A.; Cirtain, J.; Golub, L.; DeLuca, E.; Savage, S.; Alexander, C.; Schuler, T.

2014-01-01

In the summer of 2012, the High-resolution Coronal Imager (Hi-C) flew aboard a NASA sounding rocket and collected the highest spatial resolution images ever obtained of the solar corona. One of the goals of the Hi-C flight was to characterize the substructure of the solar corona. We therefore examine how the intensity scales from AIA resolution to Hi-C resolution. For each low-resolution pixel, we calculate the standard deviation in the contributing high-resolution pixel intensities and compare that to the expected standard deviation calculated from the noise. If these numbers are approximately equal, the corona can be assumed to be smoothly varying, i.e. have no evidence of substructure in the Hi-C image to within Hi-C's ability to measure it given its throughput and readout noise. A standard deviation much larger than the noise value indicates the presence of substructure. We calculate these values for each low-resolution pixel for each frame of the Hi-C data. On average, 70 percent of the pixels in each Hi-C image show no evidence of substructure. The locations where substructure is prevalent is in the moss regions and in regions of sheared magnetic field. We also find that the level of substructure varies significantly over the roughly 160 s of the Hi-C data analyzed here. This result indicates that the finely structured corona is concentrated in regions of heating and is highly time dependent.

DISCOVERY OF FINELY STRUCTURED DYNAMIC SOLAR CORONA OBSERVED IN THE Hi-C TELESCOPE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Winebarger, Amy R.; Cirtain, Jonathan; Savage, Sabrina

In the Summer of 2012, the High-resolution Coronal Imager (Hi-C) flew on board a NASA sounding rocket and collected the highest spatial resolution images ever obtained of the solar corona. One of the goals of the Hi-C flight was to characterize the substructure of the solar corona. We therefore examine how the intensity scales from AIA resolution to Hi-C resolution. For each low-resolution pixel, we calculate the standard deviation in the contributing high-resolution pixel intensities and compare that to the expected standard deviation calculated from the noise. If these numbers are approximately equal, the corona can be assumed to bemore » smoothly varying, i.e., have no evidence of substructure in the Hi-C image to within Hi-C's ability to measure it given its throughput and readout noise. A standard deviation much larger than the noise value indicates the presence of substructure. We calculate these values for each low-resolution pixel for each frame of the Hi-C data. On average, 70% of the pixels in each Hi-C image show no evidence of substructure. The locations where substructure is prevalent is in the moss regions and in regions of sheared magnetic field. We also find that the level of substructure varies significantly over the roughly 160 s of the Hi-C data analyzed here. This result indicates that the finely structured corona is concentrated in regions of heating and is highly time dependent.« less

Shape and Albedo from Shading (SAfS) for Pixel-Level dem Generation from Monocular Images Constrained by Low-Resolution dem

NASA Astrophysics Data System (ADS)

Wu, Bo; Chung Liu, Wai; Grumpe, Arne; Wöhler, Christian

2016-06-01

Lunar topographic information, e.g., lunar DEM (Digital Elevation Model), is very important for lunar exploration missions and scientific research. Lunar DEMs are typically generated from photogrammetric image processing or laser altimetry, of which photogrammetric methods require multiple stereo images of an area. DEMs generated from these methods are usually achieved by various interpolation techniques, leading to interpolation artifacts in the resulting DEM. On the other hand, photometric shape reconstruction, e.g., SfS (Shape from Shading), extensively studied in the field of Computer Vision has been introduced to pixel-level resolution DEM refinement. SfS methods have the ability to reconstruct pixel-wise terrain details that explain a given image of the terrain. If the terrain and its corresponding pixel-wise albedo were to be estimated simultaneously, this is a SAfS (Shape and Albedo from Shading) problem and it will be under-determined without additional information. Previous works show strong statistical regularities in albedo of natural objects, and this is even more logically valid in the case of lunar surface due to its lower surface albedo complexity than the Earth. In this paper we suggest a method that refines a lower-resolution DEM to pixel-level resolution given a monocular image of the coverage with known light source, at the same time we also estimate the corresponding pixel-wise albedo map. We regulate the behaviour of albedo and shape such that the optimized terrain and albedo are the likely solutions that explain the corresponding image. The parameters in the approach are optimized through a kernel-based relaxation framework to gain computational advantages. In this research we experimentally employ the Lunar-Lambertian model for reflectance modelling; the framework of the algorithm is expected to be independent of a specific reflectance model. Experiments are carried out using the monocular images from Lunar Reconnaissance Orbiter (LRO) Narrow Angle Camera (NAC) (0.5 m spatial resolution), constrained by the SELENE and LRO Elevation Model (SLDEM 2015) of 60 m spatial resolution. The results indicate that local details are largely recovered by the algorithm while low frequency topographic consistency is affected by the low-resolution DEM.

Front-end multiplexing—applied to SQUID multiplexing: Athena X-IFU and QUBIC experiments

NASA Astrophysics Data System (ADS)

Prele, D.

2015-08-01

As we have seen for digital camera market and a sensor resolution increasing to "megapixels", all the scientific and high-tech imagers (whatever the wave length - from radio to X-ray range) tends also to always increases the pixels number. So the constraints on front-end signals transmission increase too. An almost unavoidable solution to simplify integration of large arrays of pixels is front-end multiplexing. Moreover, "simple" and "efficient" techniques allow integration of read-out multiplexers in the focal plane itself. For instance, CCD (Charge Coupled Device) technology has boost number of pixels in digital camera. Indeed, this is exactly a planar technology which integrates both the sensors and a front-end multiplexed readout. In this context, front-end multiplexing techniques will be discussed for a better understanding of their advantages and their limits. Finally, the cases of astronomical instruments in the millimeter and in the X-ray ranges using SQUID (Superconducting QUantum Interference Device) will be described.

Change of spatial information under rescaling: A case study using multi-resolution image series

NASA Astrophysics Data System (ADS)

Chen, Weirong; Henebry, Geoffrey M.

Spatial structure in imagery depends on a complicated interaction between the observational regime and the types and arrangements of entities within the scene that the image portrays. Although block averaging of pixels has commonly been used to simulate coarser resolution imagery, relatively little attention has been focused on the effects of simple rescaling on spatial structure and the explanation and a possible solution to the problem. Yet, if there are significant differences in spatial variance between rescaled and observed images, it may affect the reliability of retrieved biogeophysical quantities. To investigate these issues, a nested series of high spatial resolution digital imagery was collected at a research site in eastern Nebraska in 2001. An airborne Kodak DCS420IR camera acquired imagery at three altitudes, yielding nominal spatial resolutions ranging from 0.187 m to 1 m. The red and near infrared (NIR) bands of the co-registered image series were normalized using pseudo-invariant features, and the normalized difference vegetation index (NDVI) was calculated. Plots of grain sorghum planted in orthogonal crop row orientations were extracted from the image series. The finest spatial resolution data were then rescaled by averaging blocks of pixels to produce a rescaled image series that closely matched the spatial resolution of the observed image series. Spatial structures of the observed and rescaled image series were characterized using semivariogram analysis. Results for NDVI and its component bands show, as expected, that decreasing spatial resolution leads to decreasing spatial variability and increasing spatial dependence. However, compared to the observed data, the rescaled images contain more persistent spatial structure that exhibits limited variation in both spatial dependence and spatial heterogeneity. Rescaling via simple block averaging fails to consider the effect of scene object shape and extent on spatial information. As the features portrayed by pixels are equally weighted regardless of the shape and extent of the underlying scene objects, the rescaled image retains more of the original spatial information than would occur through direct observation at a coarser sensor spatial resolution. In contrast, for the observed images, due to the effect of the modulation transfer function (MTF) of the imaging system, high frequency features like edges are blurred or lost as the pixel size increases, resulting in greater variation in spatial structure. Successive applications of a low-pass spatial convolution filter are shown to mimic a MTF. Accordingly, it is recommended that such a procedure be applied prior to rescaling by simple block averaging, if insufficient image metadata exist to replicate the net MTF of the imaging system, as might be expected in land cover change analysis studies using historical imagery.

WE-G-204-06: Grid-Line Artifact Minimization for High Resolution Detectors Using Iterative Residual Scatter Correction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rana, R; Bednarek, D; Rudin, S

2015-06-15

Purpose: Anti-scatter grid-line artifacts are more prominent for high-resolution x-ray detectors since the fraction of a pixel blocked by the grid septa is large. Direct logarithmic subtraction of the artifact pattern is limited by residual scattered radiation and we investigate an iterative method for scatter correction. Methods: A stationary Smit-Rοntgen anti-scatter grid was used with a high resolution Dexela 1207 CMOS X-ray detector (75 µm pixel size) to image an artery block (Nuclear Associates, Model 76-705) placed within a uniform head equivalent phantom as the scattering source. The image of the phantom was divided by a flat-field image obtained withoutmore » scatter but with the grid to eliminate grid-line artifacts. Constant scatter values were subtracted from the phantom image before dividing by the averaged flat-field-with-grid image. The standard deviation of pixel values for a fixed region of the resultant images with different subtracted scatter values provided a measure of the remaining grid-line artifacts. Results: A plot of the standard deviation of image pixel values versus the subtracted scatter value shows that the image structure noise reaches a minimum before going up again as the scatter value is increased. This minimum corresponds to a minimization of the grid-line artifacts as demonstrated in line profile plots obtained through each of the images perpendicular to the grid lines. Artifact-free images of the artery block were obtained with the optimal scatter value obtained by this iterative approach. Conclusion: Residual scatter subtraction can provide improved grid-line artifact elimination when using the flat-field with grid “subtraction” technique. The standard deviation of image pixel values can be used to determine the optimal scatter value to subtract to obtain a minimization of grid line artifacts with high resolution x-ray imaging detectors. This study was supported by NIH Grant R01EB002873 and an equipment grant from Toshiba Medical Systems Corp.« less

Validation of the USGS Landsat Burned Area Essential Climate Variable (BAECV) across the conterminous United States

USGS Publications Warehouse

Vanderhoof, Melanie; Fairaux, Nicole; Beal, Yen-Ju G.; Hawbaker, Todd J.

2017-01-01

The Landsat Burned Area Essential Climate Variable (BAECV), developed by the U.S. Geological Survey (USGS), capitalizes on the long temporal availability of Landsat imagery to identify burned areas across the conterminous United States (CONUS) (1984–2015). Adequate validation of such products is critical for their proper usage and interpretation. Validation of coarse-resolution products often relies on independent data derived from moderate-resolution sensors (e.g., Landsat). Validation of Landsat products, in turn, is challenging because there is no corresponding source of high-resolution, multispectral imagery that has been systematically collected in space and time over the entire temporal extent of the Landsat archive. Because of this, comparison between high-resolution images and Landsat science products can help increase user's confidence in the Landsat science products, but may not, alone, be adequate. In this paper, we demonstrate an approach to systematically validate the Landsat-derived BAECV product. Burned area extent was mapped for Landsat image pairs using a manually trained semi-automated algorithm that was manually edited across 28 path/rows and five different years (1988, 1993, 1998, 2003, 2008). Three datasets were independently developed by three analysts and the datasets were integrated on a pixel by pixel basis in which at least one to all three analysts were required to agree a pixel was burned. We found that errors within our Landsat reference dataset could be minimized by using the rendition of the dataset in which pixels were mapped as burned if at least two of the three analysts agreed. BAECV errors of omission and commission for the detection of burned pixels averaged 42% and 33%, respectively for CONUS across all five validation years. Errors of omission and commission were lowest across the western CONUS, for example in the shrub and scrublands of the Arid West (31% and 24%, respectively), and highest in the grasslands and agricultural lands of the Great Plains in central CONUS (62% and 57%, respectively). The BAECV product detected most (> 65%) fire events > 10 ha across the western CONUS (Arid and Mountain West ecoregions). Our approach and results demonstrate that a thorough validation of Landsat science products can be completed with independent Landsat-derived reference data, but could be strengthened by the use of complementary sources of high-resolution data.

Preliminary Performance of CdZnTe Imaging Detector Prototypes

NASA Technical Reports Server (NTRS)

Ramsey, B.; Sharma, D. P.; Meisner, J.; Gostilo, V.; Ivanov, V.; Loupilov, A.; Sokolov, A.; Sipila, H.

1999-01-01

The promise of good energy and spatial resolution coupled with high efficiency and near-room-temperature operation has fuelled a large International effort to develop Cadmium-Zinc-Telluride (CdZnTe) for the hard-x-ray region. We present here preliminary results from our development of small-pixel imaging arrays fabricated on 5x5x1-mm and 5x5x2-mm spectroscopy and discriminator-grade material. Each array has 16 (4x4) 0.65-mm gold readout pads on a 0.75-mm pitch, with each pad connected to a discrete preamplifier via a pulse-welded gold wire. Each array is mounted on a 3-stage Peltier cooler and housed in an ion-pump-evacuated housing which also contains a hybrid micro-assembly for the 16 channels of electronics. We have investigated the energy resolution and approximate photopeak efficiency for each pixel at several energies and have used an ultra-fine beam x-ray generator to probe the performance at the pixel boundaries. Both arrays gave similar results, and at an optimum temperature of -20 C we achieved between 2 and 3% FWHM energy resolution at 60 keV and around 15% at 5.9 keV. We found that all the charge was contained within 1 pixel until very close to the pixels edge, where it would start to be shared with its neighbor. Even between pixels, all the charge would be appropriately shared with no apparently loss of efficiency or resolution. Full details of these measurements will be presented, together with their implications for future imaging-spectroscopy applications.

X-ray photon correlation spectroscopy using a fast pixel array detector with a grid mask resolution enhancer.

PubMed

Hoshino, Taiki; Kikuchi, Moriya; Murakami, Daiki; Harada, Yoshiko; Mitamura, Koji; Ito, Kiminori; Tanaka, Yoshihito; Sasaki, Sono; Takata, Masaki; Jinnai, Hiroshi; Takahara, Atsushi

2012-11-01

The performance of a fast pixel array detector with a grid mask resolution enhancer has been demonstrated for X-ray photon correlation spectroscopy (XPCS) measurements to investigate fast dynamics on a microscopic scale. A detecting system, in which each pixel of a single-photon-counting pixel array detector, PILATUS, is covered by grid mask apertures, was constructed for XPCS measurements of silica nanoparticles in polymer melts. The experimental results are confirmed to be consistent by comparison with other independent experiments. By applying this method, XPCS measurements can be carried out by customizing the hole size of the grid mask to suit the experimental conditions, such as beam size, detector size and sample-to-detector distance.

A new generation of small pixel pitch/SWaP cooled infrared detectors

NASA Astrophysics Data System (ADS)

Espuno, L.; Pacaud, O.; Reibel, Y.; Rubaldo, L.; Kerlain, A.; Péré-Laperne, N.; Dariel, A.; Roumegoux, J.; Brunner, A.; Kessler, A.; Gravrand, O.; Castelein, P.

2015-10-01

Following clear technological trends, the cooled IR detectors market is now in demand for smaller, more efficient and higher performance products. This demand pushes products developments towards constant innovations on detectors, read-out circuits, proximity electronics boards, and coolers. Sofradir was first to show a 10μm focal plane array (FPA) at DSS 2012, and announced the DAPHNIS 10μm product line back in 2014. This pixel pitch is a key enabler for infrared detectors with increased resolution. Sofradir recently achieved outstanding products demonstrations at this pixel pitch, which clearly demonstrate the benefits of adopting 10μm pixel pitch focal plane array-based detectors. Both HD and XGA Daphnis 10μm products also benefit from a global video datapath efficiency improvement by transitioning to digital video interfaces. Moreover, innovative smart pixels functionalities drastically increase product versatility. In addition to this strong push towards a higher pixels density, Sofradir acknowledges the need for smaller and lower power cooled infrared detector. Together with straightforward system interfaces and better overall performances, latest technological advances on SWAP-C (Size, Weight, Power and Cost) Sofradir products enable the advent of a new generation of high performance portable and agile systems (handheld thermal imagers, unmanned aerial vehicles, light gimbals etc...). This paper focuses on those features and performances that can make an actual difference in the field.

A digital gigapixel large-format tile-scan camera.

PubMed

Ben-Ezra, M

2011-01-01

Although the resolution of single-lens reflex (SLR) and medium-format digital cameras has increased in recent years, applications for cultural-heritage preservation and computational photography require even higher resolutions. Addressing this issue, a large-format cameras' large image planes can achieve very high resolution without compromising pixel size and thus can provide high-quality, high-resolution images.This digital large-format tile scan camera can acquire high-quality, high-resolution images of static scenes. It employs unique calibration techniques and a simple algorithm for focal-stack processing of very large images with significant magnification variations. The camera automatically collects overlapping focal stacks and processes them into a high-resolution, extended-depth-of-field image.

X-ray analog pixel array detector for single synchrotron bunch time-resolved imaging.

PubMed

Koerner, Lucas J; Gruner, Sol M

2011-03-01

Dynamic X-ray studies can reach temporal resolutions limited by only the X-ray pulse duration if the detector is fast enough to segregate synchrotron pulses. An analog integrating pixel array detector with in-pixel storage and temporal resolution of around 150 ns, sufficient to isolate pulses, is presented. Analog integration minimizes count-rate limitations and in-pixel storage captures successive pulses. Fundamental tests of noise and linearity as well as high-speed laser measurements are shown. The detector resolved individual bunch trains at the Cornell High Energy Synchrotron Source at levels of up to 3.7 × 10(3) X-rays per pixel per train. When applied to turn-by-turn X-ray beam characterization, single-shot intensity measurements were made with a repeatability of 0.4% and horizontal oscillations of the positron cloud were detected.

X-ray analog pixel array detector for single synchrotron bunch time-resolved imaging

PubMed Central

Koerner, Lucas J.; Gruner, Sol M.

2011-01-01

Dynamic X-ray studies can reach temporal resolutions limited by only the X-ray pulse duration if the detector is fast enough to segregate synchrotron pulses. An analog integrating pixel array detector with in-pixel storage and temporal resolution of around 150 ns, sufficient to isolate pulses, is presented. Analog integration minimizes count-rate limitations and in-pixel storage captures successive pulses. Fundamental tests of noise and linearity as well as high-speed laser measurements are shown. The detector resolved individual bunch trains at the Cornell High Energy Synchrotron Source at levels of up to 3.7 × 103 X-rays per pixel per train. When applied to turn-by-turn X-ray beam characterization, single-shot intensity measurements were made with a repeatability of 0.4% and horizontal oscillations of the positron cloud were detected. PMID:21335901

Improved Fast, Deep Record Length, Time-Resolved Visible Spectroscopy of Plasmas Using Fiber Grids

NASA Astrophysics Data System (ADS)

Brockington, S.; Case, A.; Cruz, E.; Williams, A.; Witherspoon, F. D.; Horton, R.; Klauser, R.; Hwang, D.

2017-10-01

HyperV Technologies is developing a fiber-coupled, deep record-length, low-light camera head for performing high time resolution spectroscopy on visible emission from plasma events. By coupling the output of a spectrometer to an imaging fiber bundle connected to a bank of amplified silicon photomultipliers, time-resolved spectroscopic imagers of 100 to 1,000 pixels can be constructed. A second generation prototype 32-pixel spectroscopic imager employing this technique was constructed and successfully tested at the University of California at Davis Compact Toroid Injection Experiment (CTIX). Pixel performance of 10 Megaframes/sec with record lengths of up to 256,000 frames ( 25.6 milliseconds) were achieved. Pixel resolution was 12 bits. Pixel pitch can be refined by using grids of 100 μm to 1000 μm diameter fibers. Experimental results will be discussed, along with future plans for this diagnostic. Work supported by USDOE SBIR Grant DE-SC0013801.

Effect of image resolution manipulation in rearfoot angle measurements obtained with photogrammetry

PubMed Central

Sacco, I.C.N.; Picon, A.P.; Ribeiro, A.P.; Sartor, C.D.; Camargo-Junior, F.; Macedo, D.O.; Mori, E.T.T.; Monte, F.; Yamate, G.Y.; Neves, J.G.; Kondo, V.E.; Aliberti, S.

2012-01-01

The aim of this study was to investigate the influence of image resolution manipulation on the photogrammetric measurement of the rearfoot static angle. The study design was that of a reliability study. We evaluated 19 healthy young adults (11 females and 8 males). The photographs were taken at 1536 pixels in the greatest dimension, resized into four different resolutions (1200, 768, 600, 384 pixels) and analyzed by three equally trained examiners on a 96-pixels per inch (ppi) screen. An experienced physiotherapist marked the anatomic landmarks of rearfoot static angles on two occasions within a 1-week interval. Three different examiners had marked angles on digital pictures. The systematic error and the smallest detectable difference were calculated from the angle values between the image resolutions and times of evaluation. Different resolutions were compared by analysis of variance. Inter- and intra-examiner reliability was calculated by intra-class correlation coefficients (ICC). The rearfoot static angles obtained by the examiners in each resolution were not different (P > 0.05); however, the higher the image resolution the better the inter-examiner reliability. The intra-examiner reliability (within a 1-week interval) was considered to be unacceptable for all image resolutions (ICC range: 0.08-0.52). The whole body image of an adult with a minimum size of 768 pixels analyzed on a 96-ppi screen can provide very good inter-examiner reliability for photogrammetric measurements of rearfoot static angles (ICC range: 0.85-0.92), although the intra-examiner reliability within each resolution was not acceptable. Therefore, this method is not a proper tool for follow-up evaluations of patients within a therapeutic protocol. PMID:22911379

Effect of image resolution manipulation in rearfoot angle measurements obtained with photogrammetry.

PubMed

Sacco, I C N; Picon, A P; Ribeiro, A P; Sartor, C D; Camargo-Junior, F; Macedo, D O; Mori, E T T; Monte, F; Yamate, G Y; Neves, J G; Kondo, V E; Aliberti, S

2012-09-01

The aim of this study was to investigate the influence of image resolution manipulation on the photogrammetric measurement of the rearfoot static angle. The study design was that of a reliability study. We evaluated 19 healthy young adults (11 females and 8 males). The photographs were taken at 1536 pixels in the greatest dimension, resized into four different resolutions (1200, 768, 600, 384 pixels) and analyzed by three equally trained examiners on a 96-pixels per inch (ppi) screen. An experienced physiotherapist marked the anatomic landmarks of rearfoot static angles on two occasions within a 1-week interval. Three different examiners had marked angles on digital pictures. The systematic error and the smallest detectable difference were calculated from the angle values between the image resolutions and times of evaluation. Different resolutions were compared by analysis of variance. Inter- and intra-examiner reliability was calculated by intra-class correlation coefficients (ICC). The rearfoot static angles obtained by the examiners in each resolution were not different (P > 0.05); however, the higher the image resolution the better the inter-examiner reliability. The intra-examiner reliability (within a 1-week interval) was considered to be unacceptable for all image resolutions (ICC range: 0.08-0.52). The whole body image of an adult with a minimum size of 768 pixels analyzed on a 96-ppi screen can provide very good inter-examiner reliability for photogrammetric measurements of rearfoot static angles (ICC range: 0.85-0.92), although the intra-examiner reliability within each resolution was not acceptable. Therefore, this method is not a proper tool for follow-up evaluations of patients within a therapeutic protocol.

Fast, deep record length, time-resolved visible spectroscopy of plasmas using fiber grids

NASA Astrophysics Data System (ADS)

Brockington, Samuel; Case, Andrew; Cruz, Edward; Witherspoon, F. Douglas; Horton, Robert; Klauser, Ruth; Hwang, D. Q.

2016-10-01

HyperV Technologies is developing a fiber-coupled, deep-record-length, low-light camera head for performing high time resolution spectroscopy on visible emission from plasma events. New solid-state Silicon Photo-Multiplier (SiPM) chips are capable of single photon event detection and high speed data acquisition. By coupling the output of a spectrometer to an imaging fiber bundle connected to a bank of amplified SiPMs, time-resolved spectroscopic imagers of 100 to 1,000 pixels can be constructed. Target pixel performance is 10 Megaframes/sec with record lengths of up to 256,000 frames yielding 25.6 milliseconds of record at10 Megasamples/sec resolution. Pixel resolutions of 8 to 12 bits are pos- sible. Pixel pitch can be refined by using grids of 100 μm to 1000 μm diameter fibers. A prototype 32-pixel spectroscopic imager employing this technique was constructed and successfully tested at the University of California at Davis Compact Toroid Injection Experiment (CTIX) as a full demonstration of the concept. Experimental results will be dis-cussed, along with future plans for the Phase 2 project, and potential applications to plasma experiments . Work supported by USDOE SBIR Grant DE-SC0013801.

Towards simultaneous single emission microscopy and magnetic resonance imaging

NASA Astrophysics Data System (ADS)

Cai, Liang

In recent years, the combined nuclear imaging and magnetic resonance imaging (MRI) has drawn extensive research effort. They can provide simultaneously acquired anatomical and functional information inside the human/small animal body in vivo. In this dissertation, the development of an ultrahigh resolution MR-compatible SPECT (Single Photon Emission Computed Tomography) system that can be operated inside a pre-existing clinical MR scanner for simultaneous dual-modality imaging of small animals will be discussed. This system is constructed with 40 small pixel CdTe detector modules assembled in a fully stationary ring SPECT geometry. Series of experiments have demonstrated that this system is capable of providing an imaging resolution of <500?m, when operated inside MR scanners. The ultrahigh resolution MR-compatible SPECT system is built around a small pixel CdTe detector module that we recently developed. Each module consists of CdTe detectors having an overall size of 2.2 cm x 1.1 cm, divided into 64 x 32 pixels of 350 mum in size. A novel hybrid pixel-waveform (HPWF) readout system is also designed to alleviate several challenges for using small-pixel CdTe detectors in ultrahigh-resolution SPECT imaging applications. The HPWF system utilizes a modified version of a 2048-channel 2-D CMOS ASIC to readout the anode pixel, and a digitizing circuitry to sample the signal waveform induced on the cathode. The cathode waveform acquired with the HPWF circuitry offers excellent spatial resolution, energy resolution and depth of interaction (DOI) information, even with the presence of excessive charge-sharing/charge-loss between the small anode pixels. The HPWF CdTe detector is designed and constructed with a minimum amount of ferromagnetic materials, to ensure the MR-compatibility. To achieve sub-500?m imaging resolution, two special designed SPECT apertures have been constructed with different pinhole sizes of 300?m and 500?m respectively. It has 40 pinhole inserts that are made of cast platinum (90%)-iridium (10%) alloy, which provides the maximum stopping power and are compatible with MR scanners. The SPECT system is installed on a non-metal gantry constructed with 3-D printing using nylon powder material. This compact system can work as a "low-cost" desktop ultrahigh resolution SPECT system. It can also be directly operated inside an MR scanner. Accurate system geometrical calibration and corresponding image reconstruction methods for the MRC-SPECT system is developed. In order to account for the magnetic field induced distortion in the SPECT image, a comprehensive charge collection model inside strong magnetic field is adopted to produce high resolution SPECT image inside MR scanner.

Monte Carlo Optimization of Crystal Configuration for Pixelated Molecular SPECT Scanners

NASA Astrophysics Data System (ADS)

Mahani, Hojjat; Raisali, Gholamreza; Kamali-Asl, Alireza; Ay, Mohammad Reza

2017-02-01

Resolution-sensitivity-PDA tradeoff is the most challenging problem in design and optimization of pixelated preclinical SPECT scanners. In this work, we addressed such a challenge from a crystal point-of-view by looking for an optimal pixelated scintillator using GATE Monte Carlo simulation. Various crystal configurations have been investigated and the influence of different pixel sizes, pixel gaps, and three scintillators on tomographic resolution, sensitivity, and PDA of the camera were evaluated. The crystal configuration was then optimized using two objective functions: the weighted-sum and the figure-of-merit methods. The CsI(Na) reveals the highest sensitivity of the order of 43.47 cps/MBq in comparison to the NaI(Tl) and the YAP(Ce), for a 1.5×1.5 mm2 pixel size and 0.1 mm gap. The results show that the spatial resolution, in terms of FWHM, improves from 3.38 to 2.21 mm while the sensitivity simultaneously deteriorates from 42.39 cps/MBq to 27.81 cps/MBq when pixel size varies from 2×2 mm2 to 0.5×0.5 mm2 for a 0.2 mm gap, respectively. The PDA worsens from 0.91 to 0.42 when pixel size decreases from 0.5×0.5 mm2 to 1×1 mm2 for a 0.2 mm gap at 15° incident-angle. The two objective functions agree that the 1.5×1.5 mm2 pixel size and 0.1 mm Epoxy gap CsI(Na) configuration provides the best compromise for small-animal imaging, using the HiReSPECT scanner. Our study highlights that crystal configuration can significantly affect the performance of the camera, and thereby Monte Carlo optimization of pixelated detectors is mandatory in order to achieve an optimal quality tomogram.

The Transition-Edge-Sensor Array for the Micro-X Sounding Rocket

NASA Technical Reports Server (NTRS)

Eckart, M. E.; Adams, J. S.; Bailey, C. N.; Bandler, S. R.; Busch, Sarah Elizabeth; Chervenak J. A.; Finkbeiner, F. M.; Kelley, R. L.; Kilbourne, C. A.; Porst, J. P.;

Demosaiced pixel super-resolution for multiplexed holographic color imaging

PubMed Central

Wu, Yichen; Zhang, Yibo; Luo, Wei; Ozcan, Aydogan

2016-01-01

To synthesize a holographic color image, one can sequentially take three holograms at different wavelengths, e.g., at red (R), green (G) and blue (B) parts of the spectrum, and digitally merge them. To speed up the imaging process by a factor of three, a Bayer color sensor-chip can also be used to demultiplex three wavelengths that simultaneously illuminate the sample and digitally retrieve individual set of holograms using the known transmission spectra of the Bayer color filters. However, because the pixels of different channels (R, G, B) on a Bayer color sensor are not at the same physical location, conventional demosaicing techniques generate color artifacts in holographic imaging using simultaneous multi-wavelength illumination. Here we demonstrate that pixel super-resolution can be merged into the color de-multiplexing process to significantly suppress the artifacts in wavelength-multiplexed holographic color imaging. This new approach, termed Demosaiced Pixel Super-Resolution (D-PSR), generates color images that are similar in performance to sequential illumination at three wavelengths, and therefore improves the speed of holographic color imaging by 3-fold. D-PSR method is broadly applicable to holographic microscopy applications, where high-resolution imaging and multi-wavelength illumination are desired. PMID:27353242

A TECHNIQUE FOR ASSESSING THE ACCURACY OF SUB-PIXEL IMPERVIOUS SURFACE ESTIMATES DERIVED FROM LANDSAT TM IMAGERY

EPA Science Inventory

We developed a technique for assessing the accuracy of sub-pixel derived estimates of impervious surface extracted from LANDSAT TM imagery. We utilized spatially coincident
sub-pixel derived impervious surface estimates, high-resolution planimetric GIS data, vector--to-
r...

Limited Area Coverage/High Resolution Picture Transmission (LAC/HRPT) tape IJ grid pixel extraction processor user's manual

NASA Technical Reports Server (NTRS)

Obrien, S. O. (Principal Investigator)

1980-01-01

The program, LACREG, extracted all pixels that are contained in a specific IJ grid section. The pixels, along with a header record are stored in a disk file defined by the user. The program will extract up to 99 IJ grid sections.

High spatiotemporal resolution measurement of regional lung air volumes from 2D phase contrast x-ray images.

PubMed

Leong, Andrew F T; Fouras, Andreas; Islam, M Sirajul; Wallace, Megan J; Hooper, Stuart B; Kitchen, Marcus J

2013-04-01

Described herein is a new technique for measuring regional lung air volumes from two-dimensional propagation-based phase contrast x-ray (PBI) images at very high spatial and temporal resolution. Phase contrast dramatically increases lung visibility and the outlined volumetric reconstruction technique quantifies dynamic changes in respiratory function. These methods can be used for assessing pulmonary disease and injury and for optimizing mechanical ventilation techniques for preterm infants using animal models. The volumetric reconstruction combines the algorithms of temporal subtraction and single image phase retrieval (SIPR) to isolate the image of the lungs from the thoracic cage in order to measure regional lung air volumes. The SIPR algorithm was used to recover the change in projected thickness of the lungs on a pixel-by-pixel basis (pixel dimensions ≈ 16.2 μm). The technique has been validated using numerical simulation and compared results of measuring regional lung air volumes with and without the use of temporal subtraction for removing the thoracic cage. To test this approach, a series of PBI images of newborn rabbit pups mechanically ventilated at different frequencies was employed. Regional lung air volumes measured from PBI images of newborn rabbit pups showed on average an improvement of at least 20% in 16% of pixels within the lungs in comparison to that measured without the use of temporal subtraction. The majority of pixels that showed an improvement was found to be in regions occupied by bone. Applying the volumetric technique to sequences of PBI images of newborn rabbit pups, it is shown that lung aeration at birth can be highly heterogeneous. This paper presents an image segmentation technique based on temporal subtraction that has successfully been used to isolate the lungs from PBI chest images, allowing the change in lung air volume to be measured over regions as small as the pixel size. Using this technique, it is possible to measure changes in regional lung volume at high spatial and temporal resolution during breathing at much lower x-ray dose than would be required using computed tomography.

Pixel decomposition for tracking in low resolution videos

NASA Astrophysics Data System (ADS)

Govinda, Vivekanand; Ralph, Jason F.; Spencer, Joseph W.; Goulermas, John Y.; Yang, Lihua; Abbas, Alaa M.

2008-04-01

This paper describes a novel set of algorithms that allows indoor activity to be monitored using data from very low resolution imagers and other non-intrusive sensors. The objects are not resolved but activity may still be determined. This allows the use of such technology in sensitive environments where privacy must be maintained. Spectral un-mixing algorithms from remote sensing were adapted for this environment. These algorithms allow the fractional contributions from different colours within each pixel to be estimated and this is used to assist in the detection and monitoring of small objects or sub-pixel motion.

Fifty Years of Mars Imaging: from Mariner 4 to HiRISE

NASA Image and Video Library

2017-11-20

This image from NASA's Mars Reconnaissance Orbiter (MRO) shows Mars' surface in detail. Mars has captured the imagination of astronomers for thousands of years, but it wasn't until the last half a century that we were able to capture images of its surface in detail. This particular site on Mars was first imaged in 1965 by the Mariner 4 spacecraft during the first successful fly-by mission to Mars. From an altitude of around 10,000 kilometers, this image (the ninth frame taken) achieved a resolution of approximately 1.25 kilometers per pixel. Since then, this location has been observed by six other visible cameras producing images with varying resolutions and sizes. This includes HiRISE (highlighted in yellow), which is the highest-resolution and has the smallest "footprint." This compilation, spanning Mariner 4 to HiRISE, shows each image at full-resolution. Beginning with Viking 1 and ending with our HiRISE image, this animation documents the historic imaging of a particular site on another world. In 1976, the Viking 1 orbiter began imaging Mars in unprecedented detail, and by 1980 had successfully mosaicked the planet at approximately 230 meters per pixel. In 1999, the Mars Orbiter Camera onboard the Mars Global Surveyor (1996) also imaged this site with its Wide Angle lens, at around 236 meters per pixel. This was followed by the Thermal Emission Imaging System on Mars Odyssey (2001), which also provided a visible camera producing the image we see here at 17 meters per pixel. Later in 2012, the High-Resolution Stereo Camera on the Mars Express orbiter (2003) captured this image of the surface at 25 meters per pixel. In 2010, the Context Camera on the Mars Reconnaissance Orbiter (2005) imaged this site at about 5 meters per pixel. Finally, in 2017, HiRISE acquired the highest resolution image of this location to date at 50 centimeters per pixel. When seen at this unprecedented scale, we can discern a crater floor strewn with small rocky deposits, boulders several meters across, and wind-blown deposits in the floors of small craters and depressions. This compilation of Mars images spanning over 50 years gives us a visual appreciation of the evolution of orbital Mars imaging over a single site. The map is projected here at a scale of 50 centimeters (19.7 inches) per pixel. [The original image scale is 52.2 centimeters (20.6 inches) per pixel (with 2 x 2 binning); objects on the order of 156 centimeters (61.4 inches) across are resolved.] North is up. https://photojournal.jpl.nasa.gov/catalog/PIA22115

Small FDIRC designs

DOE PAGES

Dey, B.; Ratcliff, B.; Va’vra, J.

2017-02-16

In this article, we explore the angular resolution limits attainable in small FDIRC designs taking advantage of the new highly pixelated detectors that are now available. Since the basic FDIRC design concept attains its particle separation performance mostly in the angular domain as measured by two-dimensional pixels, this paper relies primarily on a pixel-based analysis, with additional chromatic corrections using the time domain, requiring single photon timing resolution at a level of 100–200 ps only. This approach differs from other modern DIRC design concepts such as TOP or TORCH detectors, whose separation performances rely more strongly on time-dependent analyses. Inmore » conclusion, we find excellent single photon resolution with a geometry where individual bars are coupled to a single plate, which is coupled in turn to a cylindrical lens focusing camera.« less

Small FDIRC designs

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dey, B.; Ratcliff, B.; Va’vra, J.

In this article, we explore the angular resolution limits attainable in small FDIRC designs taking advantage of the new highly pixelated detectors that are now available. Since the basic FDIRC design concept attains its particle separation performance mostly in the angular domain as measured by two-dimensional pixels, this paper relies primarily on a pixel-based analysis, with additional chromatic corrections using the time domain, requiring single photon timing resolution at a level of 100–200 ps only. This approach differs from other modern DIRC design concepts such as TOP or TORCH detectors, whose separation performances rely more strongly on time-dependent analyses. Inmore » conclusion, we find excellent single photon resolution with a geometry where individual bars are coupled to a single plate, which is coupled in turn to a cylindrical lens focusing camera.« less

The effect of imposing 'fractional abundance constraints' onto the multilayer perceptron for sub-pixel land cover classification

NASA Astrophysics Data System (ADS)

Heremans, Stien; Suykens, Johan A. K.; Van Orshoven, Jos

2016-02-01

To be physically interpretable, sub-pixel land cover fractions or abundances should fulfill two constraints, the Abundance Non-negativity Constraint (ANC) and the Abundance Sum-to-one Constraint (ASC). This paper focuses on the effect of imposing these constraints onto the MultiLayer Perceptron (MLP) for a multi-class sub-pixel land cover classification of a time series of low resolution MODIS-images covering the northern part of Belgium. Two constraining modes were compared, (i) an in-training approach that uses 'softmax' as the transfer function in the MLP's output layer and (ii) a post-training approach that linearly rescales the outputs of the unconstrained MLP. Our results demonstrate that the pixel-level prediction accuracy is markedly increased by the explicit enforcement, both in-training and post-training, of the ANC and the ASC. For aggregations of pixels (municipalities), the constrained perceptrons perform at least as well as their unconstrained counterparts. Although the difference in performance between the in-training and post-training approach is small, we recommend the former for integrating the fractional abundance constraints into MLPs meant for sub-pixel land cover estimation, regardless of the targeted level of spatial aggregation.

Experimental criteria for the determination of fractal parameters of premixed turbulent flames

NASA Astrophysics Data System (ADS)

Shepherd, I. G.; Cheng, Robert K.; Talbot, L.

1992-10-01

The influence of spatial resolution, digitization noise, the number of records used for averaging, and the method of analysis on the determination of the fractal parameters of a high Damköhler number, methane/air, premixed, turbulent stagnation-point flame are investigated in this paper. The flow exit velocity was 5 m/s and the turbulent Reynolds number was 70 based on a integral scale of 3 mm and a turbulent intensity of 7%. The light source was a copper vapor laser which delivered 20 nsecs, 5 mJ pulses at 4 kHz and the tomographic cross-sections of the flame were recorded by a high speed movie camera. The spatial resolution of the images is 155 × 121 μm/pixel with a field of view of 50 × 65 mm. The stepping caliper technique for obtaining the fractal parameters is found to give the clearest indication of the cutoffs and the effects of noise. It is necessary to ensemble average the results from more than 25 statistically independent images to reduce sufficiently the scatter in the fractal parameters. The effects of reduced spatial resolution on fractal plots are estimated by artificial degradation of the resolution of the digitized flame boundaries. The effect of pixel resolution, an apparent increase in flame length below the inner scale rolloff, appears in the fractal plots when the measurent scale is less than approximately twice the pixel resolution. Although a clearer determination of fractal parameters is obtained by local averaging of the flame boundaries which removes digitization noise, at low spatial resolution this technique can reduce the fractal dimension. The degree of fractal isotropy of the flame surface can have a significant effect on the estimation of the flame surface area and hence burning rate from two-dimensional images. To estimate this isotropy a determination of the outer cutoff is required and three-dimensional measurements are probably also necessary.

Laser pixelation of thick scintillators for medical imaging applications: x-ray studies

NASA Astrophysics Data System (ADS)

Sabet, Hamid; Kudrolli, Haris; Marton, Zsolt; Singh, Bipin; Nagarkar, Vivek V.

2013-09-01

To achieve high spatial resolution required in nuclear imaging, scintillation light spread has to be controlled. This has been traditionally achieved by introducing structures in the bulk of scintillation materials; typically by mechanical pixelation of scintillators and fill the resultant inter-pixel gaps by reflecting materials. Mechanical pixelation however, is accompanied by various cost and complexity issues especially for hard, brittle and hygroscopic materials. For example LSO and LYSO, hard and brittle scintillators of interest to medical imaging community, are known to crack under thermal and mechanical stress; the material yield drops quickly with large arrays with high aspect ratio pixels and therefore the pixelation process cost increases. We are utilizing a novel technique named Laser Induced Optical Barriers (LIOB) for pixelation of scintillators that overcomes the issues associated with mechanical pixelation. In this technique, we can introduce optical barriers within the bulk of scintillator crystals to form pixelated arrays with small pixel size and large thickness. We applied LIOB to LYSO using a high-frequency solid-state laser. Arrays with different crystal thickness (5 to 20 mm thick), and pixel size (0.8×0.8 to 1.5×1.5 mm2) were fabricated and tested. The width of the optical barriers were controlled by fine-tuning key parameters such as lens focal spot size and laser energy density. Here we report on LIOB process, its optimization, and the optical crosstalk measurements using X-rays. There are many applications that can potentially benefit from LIOB including but not limited to clinical/pre-clinical PET and SPECT systems, and photon counting CT detectors.

Performance of In-Pixel Circuits for Photon Counting Arrays (PCAs) Based on Polycrystalline Silicon TFTs

PubMed Central

Liang, Albert K.; Koniczek, Martin; Antonuk, Larry E.; El-Mohri, Youcef; Zhao, Qihua; Street, Robert A.; Lu, Jeng Ping

2017-01-01

Photon counting arrays (PCAs), defined as pixelated imagers which measure the absorbed energy of x-ray photons individually and record this information digitally, are of increasing clinical interest. A number of PCA prototypes with a 1 mm pixel-to-pixel pitch have recently been fabricated with polycrystalline silicon (poly-Si) — a thin-film technology capable of creating monolithic imagers of a size commensurate with human anatomy. In this study, analog and digital simulation frameworks were developed to provide insight into the influence of individual poly-Si transistors on pixel circuit performance — information that is not readily available through empirical means. The simulation frameworks were used to characterize the circuit designs employed in the prototypes. The analog framework, which determines the noise produced by individual transistors, was used to estimate energy resolution, as well as to identify which transistors contribute the most noise. The digital framework, which analyzes how well circuits function in the presence of significant variations in transistor properties, was used to estimate how fast a circuit can produce an output (referred to as output count rate). In addition, an algorithm was developed and used to estimate the minimum pixel pitch that could be achieved for the pixel circuits of the current prototypes. The simulation frameworks predict that the analog component of the PCA prototypes could have energy resolution as low as 8.9% FWHM at 70 keV; and the digital components should work well even in the presence of significant TFT variations, with the fastest component having output count rates as high as 3 MHz. Finally, based on conceivable improvements in the underlying fabrication process, the algorithm predicts that the 1 mm pitch of the current PCA prototypes could be reduced significantly, potentially to between ~240 and 290 μm. PMID:26878107

Performance of in-pixel circuits for photon counting arrays (PCAs) based on polycrystalline silicon TFTs.

PubMed

Liang, Albert K; Koniczek, Martin; Antonuk, Larry E; El-Mohri, Youcef; Zhao, Qihua; Street, Robert A; Lu, Jeng Ping

2016-03-07

Photon counting arrays (PCAs), defined as pixelated imagers which measure the absorbed energy of x-ray photons individually and record this information digitally, are of increasing clinical interest. A number of PCA prototypes with a 1 mm pixel-to-pixel pitch have recently been fabricated with polycrystalline silicon (poly-Si)-a thin-film technology capable of creating monolithic imagers of a size commensurate with human anatomy. In this study, analog and digital simulation frameworks were developed to provide insight into the influence of individual poly-Si transistors on pixel circuit performance-information that is not readily available through empirical means. The simulation frameworks were used to characterize the circuit designs employed in the prototypes. The analog framework, which determines the noise produced by individual transistors, was used to estimate energy resolution, as well as to identify which transistors contribute the most noise. The digital framework, which analyzes how well circuits function in the presence of significant variations in transistor properties, was used to estimate how fast a circuit can produce an output (referred to as output count rate). In addition, an algorithm was developed and used to estimate the minimum pixel pitch that could be achieved for the pixel circuits of the current prototypes. The simulation frameworks predict that the analog component of the PCA prototypes could have energy resolution as low as 8.9% full width at half maximum (FWHM) at 70 keV; and the digital components should work well even in the presence of significant thin-film transistor (TFT) variations, with the fastest component having output count rates as high as 3 MHz. Finally, based on conceivable improvements in the underlying fabrication process, the algorithm predicts that the 1 mm pitch of the current PCA prototypes could be reduced significantly, potentially to between ~240 and 290 μm.

SNR improvement for hyperspectral application using frame and pixel binning

NASA Astrophysics Data System (ADS)

Rehman, Sami Ur; Kumar, Ankush; Banerjee, Arup

2016-05-01

Hyperspectral imaging spectrometer systems are increasingly being used in the field of remote sensing for variety of civilian and military applications. The ability of such instruments in discriminating finer spectral features along with improved spatial and radiometric performance have made such instruments a powerful tool in the field of remote sensing. Design and development of spaceborne hyper spectral imaging spectrometers poses lot of technological challenges in terms of optics, dispersion element, detectors, electronics and mechanical systems. The main factors that define the type of detectors are the spectral region, SNR, dynamic range, pixel size, number of pixels, frame rate, operating temperature etc. Detectors with higher quantum efficiency and higher well depth are the preferred choice for such applications. CCD based Si detectors serves the requirement of high well depth for VNIR band spectrometers but suffers from smear. Smear can be controlled by using CMOS detectors. Si CMOS detectors with large format arrays are available. These detectors generally have smaller pitch and low well depth. Binning technique can be used with available CMOS detectors to meet the large swath, higher resolution and high SNR requirements. Availability of larger dwell time of satellite can be used to bin multiple frames to increase the signal collection even with lesser well depth detectors and ultimately increase the SNR. Lab measurements reveal that SNR improvement by frame binning is more in comparison to pixel binning. Effect of pixel binning as compared to the frame binning will be discussed and degradation of SNR as compared to theoretical value for pixel binning will be analyzed.

Maximum likelihood positioning and energy correction for scintillation detectors

NASA Astrophysics Data System (ADS)

Lerche, Christoph W.; Salomon, André; Goldschmidt, Benjamin; Lodomez, Sarah; Weissler, Björn; Solf, Torsten

2016-02-01

An algorithm for determining the crystal pixel and the gamma ray energy with scintillation detectors for PET is presented. The algorithm uses Likelihood Maximisation (ML) and therefore is inherently robust to missing data caused by defect or paralysed photo detector pixels. We tested the algorithm on a highly integrated MRI compatible small animal PET insert. The scintillation detector blocks of the PET gantry were built with the newly developed digital Silicon Photomultiplier (SiPM) technology from Philips Digital Photon Counting and LYSO pixel arrays with a pitch of 1 mm and length of 12 mm. Light sharing was used to readout the scintillation light from the 30× 30 scintillator pixel array with an 8× 8 SiPM array. For the performance evaluation of the proposed algorithm, we measured the scanner’s spatial resolution, energy resolution, singles and prompt count rate performance, and image noise. These values were compared to corresponding values obtained with Center of Gravity (CoG) based positioning methods for different scintillation light trigger thresholds and also for different energy windows. While all positioning algorithms showed similar spatial resolution, a clear advantage for the ML method was observed when comparing the PET scanner’s overall single and prompt detection efficiency, image noise, and energy resolution to the CoG based methods. Further, ML positioning reduces the dependence of image quality on scanner configuration parameters and was the only method that allowed achieving highest energy resolution, count rate performance and spatial resolution at the same time.

The NASA/GEWEX Surface Radiation Budget Release 4 Integrated Product: An Assessment of Improvements in Algorithms and Inputs

NASA Astrophysics Data System (ADS)

Stackhouse, P. W., Jr.; Cox, S. J.; Mikovitz, J. C.; Zhang, T.; Gupta, S. K.

2016-12-01

The NASA/GEWEX Surface Radiation Budget (SRB) project produces, validates and analyzes shortwave and longwave surface and top of atmosphere radiative fluxes for the 1983-near present time period. The current release 3.0/3.1 consists of 1x1 degree radiative fluxes (available at gewex-srb.larc.nasa.gov) and is produced using the International Satellite Cloud Climatology Project (ISCCP) DX product for pixel level radiance and cloud information. This ISCCP DX product is subsampled to 30 km. ISCCP is currently recalibrating and reprocessing their entire data series, to be released as the H product series, with its highest resolution at 10km pixel resolution. The nine-fold increase in number of pixels will allow SRB to produce a higher resolution gridded product (e.g. 0.5 degree or higher), as well as the production of pixel-level fluxes. Other key input improvements include a detailed aerosol history using the Max Planck Institute Aerosol Climatology (MAC), temperature and moisture profiles from HIRS, and new topography, surface type, and snow/ice maps. Here we present results for the improved GEWEX Shortwave and Longwave algorithm (GSW and GLW) with new ISCCP data (for at least 5 years, 2005-2009), various other improved input data sets and incorporation of many additional internal SRB model improvements. We assess the radiative fluxes from new SRB products and contrast these at various resolutions. All these fluxes are compared to both surface measurements and to CERES SYN1Deg and EBAF data products for assessment of the effect of improvements. The SRB data produced will be released as part of the Release 4.0 Integrated Product that shares key input and output quantities with other GEWEX global products providing estimates of the Earth's global water and energy cycle (i.e., ISCCP, SeaFlux, LandFlux, NVAP, etc.).

DOE Office of Scientific and Technical Information (OSTI.GOV)

Giraldo, L. Ocampo; Bolotnikov, A. E.; Camarda, G. S.

For this study, we evaluated the X-Y position resolution achievable in 3D pixelated detectors by processing the signal waveforms readout from neighboring pixels. In these measurements we used a focused light beam, down to 10 μm, generated by a ~1 mW pulsed laser (650 nm) to carry out raster scans over selected 3×3 pixel areas, while recording the charge signals from the 9 pixels and the cathode using two synchronized digital oscilloscopes.

Variable high-resolution color CCD camera system with online capability for professional photo studio application

NASA Astrophysics Data System (ADS)

Breitfelder, Stefan; Reichel, Frank R.; Gaertner, Ernst; Hacker, Erich J.; Cappellaro, Markus; Rudolf, Peter; Voelk, Ute

1998-04-01

Digital cameras are of increasing significance for professional applications in photo studios where fashion, portrait, product and catalog photographs or advertising photos of high quality have to be taken. The eyelike is a digital camera system which has been developed for such applications. It is capable of working online with high frame rates and images of full sensor size and it provides a resolution that can be varied between 2048 by 2048 and 6144 by 6144 pixel at a RGB color depth of 12 Bit per channel with an also variable exposure time of 1/60s to 1s. With an exposure time of 100 ms digitization takes approx. 2 seconds for an image of 2048 by 2048 pixels (12 Mbyte), 8 seconds for the image of 4096 by 4096 pixels (48 Mbyte) and 40 seconds for the image of 6144 by 6144 pixels (108 MByte). The eyelike can be used in various configurations. Used as a camera body most commercial lenses can be connected to the camera via existing lens adaptors. On the other hand the eyelike can be used as a back to most commercial 4' by 5' view cameras. This paper describes the eyelike camera concept with the essential system components. The article finishes with a description of the software, which is needed to bring the high quality of the camera to the user.

Microlens performance limits in sub-2mum pixel CMOS image sensors.

PubMed

Huo, Yijie; Fesenmaier, Christian C; Catrysse, Peter B

2010-03-15

CMOS image sensors with smaller pixels are expected to enable digital imaging systems with better resolution. When pixel size scales below 2 mum, however, diffraction affects the optical performance of the pixel and its microlens, in particular. We present a first-principles electromagnetic analysis of microlens behavior during the lateral scaling of CMOS image sensor pixels. We establish for a three-metal-layer pixel that diffraction prevents the microlens from acting as a focusing element when pixels become smaller than 1.4 microm. This severely degrades performance for on and off-axis pixels in red, green and blue color channels. We predict that one-metal-layer or backside-illuminated pixels are required to extend the functionality of microlenses beyond the 1.4 microm pixel node.

Panchromatic SED modelling of spatially resolved galaxies

NASA Astrophysics Data System (ADS)

Smith, Daniel J. B.; Hayward, Christopher C.

2018-05-01

We test the efficacy of the energy-balance spectral energy distribution (SED) fitting code MAGPHYS for recovering the spatially resolved properties of a simulated isolated disc galaxy, for which it was not designed. We perform 226 950 MAGPHYS SED fits to regions between 0.2 and 25 kpc in size across the galaxy's disc, viewed from three different sight-lines, to probe how well MAGPHYS can recover key galaxy properties based on 21 bands of UV-far-infrared model photometry. MAGPHYS yields statistically acceptable fits to >99 per cent of the pixels within the r-band effective radius and between 59 and 77 percent of pixels within 20 kpc of the nucleus. MAGPHYS is able to recover the distribution of stellar mass, star formation rate (SFR), specific SFR, dust luminosity, dust mass, and V-band attenuation reasonably well, especially when the pixel size is ≳ 1 kpc, whereas non-standard outputs (stellar metallicity and mass-weighted age) are recovered less well. Accurate recovery is more challenging in the smallest sub-regions of the disc (pixel scale ≲ 1 kpc), where the energy balance criterion becomes increasingly incorrect. Estimating integrated galaxy properties by summing the recovered pixel values, the true integrated values of all parameters considered except metallicity and age are well recovered at all spatial resolutions, ranging from 0.2 kpc to integrating across the disc, albeit with some evidence for resolution-dependent biases. These results must be considered when attempting to analyse the structure of real galaxies with actual observational data, for which the `ground truth' is unknown.

High-resolution photon spectroscopy with a microwave-multiplexed 4-pixel transition edge sensor array

NASA Astrophysics Data System (ADS)

Guss, Paul; Rabin, Michael; Croce, Mark; Hoteling, Nathan; Schwellenbach, David; Kruschwitz, Craig; Mocko, Veronika; Mukhopadhyay, Sanjoy

2017-09-01

We demonstrate very high-resolution photon spectroscopy with a microwave-multiplexed 4-pixel transition edge sensor (TES) array. The readout circuit consists of superconducting microwave resonators coupled to radio frequency superconducting-quantum-interference devices (RF-SQUIDs) and transduces changes in input current to changes in phase of a microwave signal. We used a flux-ramp modulation to linearize the response and avoid low-frequency noise. The result is a very high-resolution photon spectroscopy with a microwave-multiplexed 4-pixel transition edge sensor array. We performed and validated a small-scale demonstration and test of all the components of our concept system, which encompassed microcalorimetry, microwave multiplexing, RF-SQUIDs, and software-defined radio (SDR). We shall display data we acquired in the first simultaneous combination of all key innovations in a 4-pixel demonstration, including microcalorimetry, microwave multiplexing, RF-SQUIDs, and SDR. We present the energy spectrum of a gadolinium-153 (153Gd) source we measured using our 4-pixel TES array and the RF-SQUID multiplexer. For each pixel, one can observe the two 97.4 and 103.2 keV photopeaks. We measured the 153Gd photon source with an achieved energy resolution of 70 eV, full width half maximum (FWHM) at 100 keV, and an equivalent readout system noise of 90 pA/pHz at the TES. This demonstration establishes a path for the readout of cryogenic x-ray and gamma ray sensor arrays with more elements and spectral resolving powers. We believe this project has improved capabilities and substantively advanced the science useful for missions such as nuclear forensics, emergency response, and treaty verification through the explored TES developments.

Vertical Isolation for Photodiodes in CMOS Imagers

NASA Technical Reports Server (NTRS)

Pain, Bedabrata

2008-01-01

In a proposed improvement in complementary metal oxide/semi conduct - or (CMOS) image detectors, two additional implants in each pixel would effect vertical isolation between the metal oxide/semiconductor field-effect transistors (MOSFETs) and the photodiode of the pixel. This improvement is expected to enable separate optimization of the designs of the photodiode and the MOSFETs so as to optimize their performances independently of each other. The purpose to be served by enabling this separate optimization is to eliminate or vastly reduce diffusion cross-talk, thereby increasing sensitivity, effective spatial resolution, and color fidelity while reducing noise.

Light-controlled biphasic current stimulator IC using CMOS image sensors for high-resolution retinal prosthesis and in vitro experimental results with rd1 mouse.

PubMed

Oh, Sungjin; Ahn, Jae-Hyun; Lee, Sangmin; Ko, Hyoungho; Seo, Jong Mo; Goo, Yong-Sook; Cho, Dong-il Dan

2015-01-01

Retinal prosthetic devices stimulate retinal nerve cells with electrical signals proportional to the incident light intensities. For a high-resolution retinal prosthesis, it is necessary to reduce the size of the stimulator pixels as much as possible, because the retinal nerve cells are concentrated in a small area of approximately 5 mm × 5 mm. In this paper, a miniaturized biphasic current stimulator integrated circuit is developed for subretinal stimulation and tested in vitro. The stimulator pixel is miniaturized by using a complementary metal-oxide-semiconductor (CMOS) image sensor composed of three transistors. Compared to a pixel that uses a four-transistor CMOS image sensor, this new design reduces the pixel size by 8.3%. The pixel size is further reduced by simplifying the stimulation-current generating circuit, which provides a 43.9% size reduction when compared to the design reported to be the most advanced version to date for subretinal stimulation. The proposed design is fabricated using a 0.35 μm bipolar-CMOS-DMOS process. Each pixel is designed to fit in a 50 μ m × 55 μm area, which theoretically allows implementing more than 5000 pixels in the 5 mm × 5 mm area. Experimental results show that a biphasic current in the range of 0 to 300 μA at 12 V can be generated as a function of incident light intensities. Results from in vitro experiments with rd1 mice indicate that the proposed method can be effectively used for retinal prosthesis with a high resolution.

Preliminary Results from Small-Pixel CdZnTe and CdTe Arrays

NASA Technical Reports Server (NTRS)

Ramsey, B. D.; Sharma, D. P.; Meisner, J.; Austin, R. A.

1999-01-01

We have evaluated 2 small-pixel (0.75 mm) Cadmium-Zinc-Telluride arrays, and one Cadmium-Telluride array, all fabricated for MSFC by Metorex (Finland) and Baltic Science Institute (Riga, Latvia). Each array was optimized for operating temperature and collection bias. It was then exposed to Cadmium-109 and Iron-55 laboratory isotopes, to measure the energy resolution for each pixel and was then scanned with a finely-collimated x-ray beam, of width 50 micron, to examine pixel to pixel and inter-pixel charge collections efficiency. Preliminary results from these array tests will be presented.

All-optical framing photography based on hyperspectral imaging method

NASA Astrophysics Data System (ADS)

Liu, Shouxian; Li, Yu; Li, Zeren; Chen, Guanghua; Peng, Qixian; Lei, Jiangbo; Liu, Jun; Yuan, Shuyun

2017-02-01

We propose and experimentally demonstrate a new all optical-framing photography that uses hyperspectral imaging methods to record a chirped pulse's temporal-spatial information. This proposed method consists of three parts: (1) a chirped laser pulse encodes temporal phenomena onto wavelengths; (2) a lenslet array generates a series of integral pupil images;(3) a dispersive device disperses the integral images at void space of image sensor. Compared with Ultrafast All-Optical Framing Technology(Daniel Frayer,2013,2014) and Sequentially Time All-Optical Mapping Photography( Nakagawa 2014, 2015), our method is convenient to adjust the temporal resolution and to flexibly increase the numbers of frames. Theoretically, the temporal resolution of our scheme is limited by the amount of dispersion that is added to a Fourier transform limited femtosecond laser pulse. Correspondingly, the optimal number of frames is decided by the ratio of the observational time window to the temporal resolution, and the effective pixels of each frame are mostly limited by the dimensions M×N of the lenslet array. For example, if a 40fs Fourier transform limited femtosecond pulse is stretched to 10ps, a CCD camera with 2048×3072 pixels can record 15 framing images with temporal resolution of 650fs and image size of 100×100 pixels. As spectrometer structure, our recording part has another advantage that not only amplitude images but also frequency domain interferograms can be imaged. Therefore, it is comparatively easy to capture fast dynamics in the refractive index change of materials. A further dynamic experiment is being conducted.

Fast generation of computer-generated hologram by graphics processing unit

NASA Astrophysics Data System (ADS)

Matsuda, Sho; Fujii, Tomohiko; Yamaguchi, Takeshi; Yoshikawa, Hiroshi

2009-02-01

A cylindrical hologram is well known to be viewable in 360 deg. This hologram depends high pixel resolution.Therefore, Computer-Generated Cylindrical Hologram (CGCH) requires huge calculation amount.In our previous research, we used look-up table method for fast calculation with Intel Pentium4 2.8 GHz.It took 480 hours to calculate high resolution CGCH (504,000 x 63,000 pixels and the average number of object points are 27,000).To improve quality of CGCH reconstructed image, fringe pattern requires higher spatial frequency and resolution.Therefore, to increase the calculation speed, we have to change the calculation method. In this paper, to reduce the calculation time of CGCH (912,000 x 108,000 pixels), we employ Graphics Processing Unit (GPU).It took 4,406 hours to calculate high resolution CGCH on Xeon 3.4 GHz.Since GPU has many streaming processors and a parallel processing structure, GPU works as the high performance parallel processor.In addition, GPU gives max performance to 2 dimensional data and streaming data.Recently, GPU can be utilized for the general purpose (GPGPU).For example, NVIDIA's GeForce7 series became a programmable processor with Cg programming language.Next GeForce8 series have CUDA as software development kit made by NVIDIA.Theoretically, calculation ability of GPU is announced as 500 GFLOPS. From the experimental result, we have achieved that 47 times faster calculation compared with our previous work which used CPU.Therefore, CGCH can be generated in 95 hours.So, total time is 110 hours to calculate and print the CGCH.

Connotations of pixel-based scale effect in remote sensing and the modified fractal-based analysis method

NASA Astrophysics Data System (ADS)

Feng, Guixiang; Ming, Dongping; Wang, Min; Yang, Jianyu

2017-06-01

Scale problems are a major source of concern in the field of remote sensing. Since the remote sensing is a complex technology system, there is a lack of enough cognition on the connotation of scale and scale effect in remote sensing. Thus, this paper first introduces the connotations of pixel-based scale and summarizes the general understanding of pixel-based scale effect. Pixel-based scale effect analysis is essentially important for choosing the appropriate remote sensing data and the proper processing parameters. Fractal dimension is a useful measurement to analysis pixel-based scale. However in traditional fractal dimension calculation, the impact of spatial resolution is not considered, which leads that the scale effect change with spatial resolution can't be clearly reflected. Therefore, this paper proposes to use spatial resolution as the modified scale parameter of two fractal methods to further analyze the pixel-based scale effect. To verify the results of two modified methods (MFBM (Modified Windowed Fractal Brownian Motion Based on the Surface Area) and MDBM (Modified Windowed Double Blanket Method)); the existing scale effect analysis method (information entropy method) is used to evaluate. And six sub-regions of building areas and farmland areas were cut out from QuickBird images to be used as the experimental data. The results of the experiment show that both the fractal dimension and information entropy present the same trend with the decrease of spatial resolution, and some inflection points appear at the same feature scales. Further analysis shows that these feature scales (corresponding to the inflection points) are related to the actual sizes of the geo-object, which results in fewer mixed pixels in the image, and these inflection points are significantly indicative of the observed features. Therefore, the experiment results indicate that the modified fractal methods are effective to reflect the pixel-based scale effect existing in remote sensing data and it is helpful to analyze the observation scale from different aspects. This research will ultimately benefit for remote sensing data selection and application.

Demosaiced pixel super-resolution in digital holography for multiplexed computational color imaging on-a-chip (Conference Presentation)

NASA Astrophysics Data System (ADS)

Wu, Yichen; Zhang, Yibo; Luo, Wei; Ozcan, Aydogan

2017-03-01

Digital holographic on-chip microscopy achieves large space-bandwidth-products (e.g., >1 billion) by making use of pixel super-resolution techniques. To synthesize a digital holographic color image, one can take three sets of holograms representing the red (R), green (G) and blue (B) parts of the spectrum and digitally combine them to synthesize a color image. The data acquisition efficiency of this sequential illumination process can be improved by 3-fold using wavelength-multiplexed R, G and B illumination that simultaneously illuminates the sample, and using a Bayer color image sensor with known or calibrated transmission spectra to digitally demultiplex these three wavelength channels. This demultiplexing step is conventionally used with interpolation-based Bayer demosaicing methods. However, because the pixels of different color channels on a Bayer image sensor chip are not at the same physical location, conventional interpolation-based demosaicing process generates strong color artifacts, especially at rapidly oscillating hologram fringes, which become even more pronounced through digital wave propagation and phase retrieval processes. Here, we demonstrate that by merging the pixel super-resolution framework into the demultiplexing process, such color artifacts can be greatly suppressed. This novel technique, termed demosaiced pixel super-resolution (D-PSR) for digital holographic imaging, achieves very similar color imaging performance compared to conventional sequential R,G,B illumination, with 3-fold improvement in image acquisition time and data-efficiency. We successfully demonstrated the color imaging performance of this approach by imaging stained Pap smears. The D-PSR technique is broadly applicable to high-throughput, high-resolution digital holographic color microscopy techniques that can be used in resource-limited-settings and point-of-care offices.

A Multi-Resolution Mode CMOS Image Sensor with a Novel Two-Step Single-Slope ADC for Intelligent Surveillance Systems.

PubMed

Kim, Daehyeok; Song, Minkyu; Choe, Byeongseong; Kim, Soo Youn

2017-06-25

In this paper, we present a multi-resolution mode CMOS image sensor (CIS) for intelligent surveillance system (ISS) applications. A low column fixed-pattern noise (CFPN) comparator is proposed in 8-bit two-step single-slope analog-to-digital converter (TSSS ADC) for the CIS that supports normal, 1/2, 1/4, 1/8, 1/16, 1/32, and 1/64 mode of pixel resolution. We show that the scaled-resolution images enable CIS to reduce total power consumption while images hold steady without events. A prototype sensor of 176 × 144 pixels has been fabricated with a 0.18 μm 1-poly 4-metal CMOS process. The area of 4-shared 4T-active pixel sensor (APS) is 4.4 μm × 4.4 μm and the total chip size is 2.35 mm × 2.35 mm. The maximum power consumption is 10 mW (with full resolution) with supply voltages of 3.3 V (analog) and 1.8 V (digital) and 14 frame/s of frame rates.

Application of dot-matrix illumination of liquid crystal phase space light modulator in 3D imaging of APD array

NASA Astrophysics Data System (ADS)

Wang, Shuai; Sun, Huayan; Guo, Huichao

2018-01-01

Aiming at the problem of beam scanning in low-resolution APD array in three-dimensional imaging, a method of beam scanning with liquid crystal phase-space optical modulator is proposed to realize high-resolution imaging by low-resolution APD array. First, a liquid crystal phase spatial light modulator is used to generate a beam array and then a beam array is scanned. Since the sub-beam divergence angle in the beam array is smaller than the field angle of a single pixel in the APD array, the APD's pixels respond only to the three-dimensional information of the beam illumination position. Through the scanning of the beam array, a single pixel is used to collect the target three-dimensional information multiple times, thereby improving the resolution of the APD detector. Finally, MATLAB is used to simulate the algorithm in this paper by using two-dimensional scalar diffraction theory, which realizes the splitting and scanning with a resolution of 5 x 5. The feasibility is verified theoretically.

Evaluation of registration accuracy between Sentinel-2 and Landsat 8

NASA Astrophysics Data System (ADS)

Barazzetti, Luigi; Cuca, Branka; Previtali, Mattia

2016-08-01

Starting from June 2015, Sentinel-2A is delivering high resolution optical images (ground resolution up to 10 meters) to provide a global coverage of the Earth's land surface every 10 days. The planned launch of Sentinel-2B along with the integration of Landsat images will provide time series with an unprecedented revisit time indispensable for numerous monitoring applications, in which high resolution multi-temporal information is required. They include agriculture, water bodies, natural hazards to name a few. However, the combined use of multi-temporal images requires an accurate geometric registration, i.e. pixel-to-pixel correspondence for terrain-corrected products. This paper presents an analysis of spatial co-registration accuracy for several datasets of Sentinel-2 and Landsat 8 images distributed all around the world. Images were compared with digital correlation techniques for image matching, obtaining an evaluation of registration accuracy with an affine transformation as geometrical model. Results demonstrate that sub-pixel accuracy was achieved between 10 m resolution Sentinel-2 bands (band 3) and 15 m resolution panchromatic Landsat images (band 8).

Developing a CCD camera with high spatial resolution for RIXS in the soft X-ray range

NASA Astrophysics Data System (ADS)

Soman, M. R.; Hall, D. J.; Tutt, J. H.; Murray, N. J.; Holland, A. D.; Schmitt, T.; Raabe, J.; Schmitt, B.

2013-12-01

The Super Advanced X-ray Emission Spectrometer (SAXES) at the Swiss Light Source contains a high resolution Charge-Coupled Device (CCD) camera used for Resonant Inelastic X-ray Scattering (RIXS). Using the current CCD-based camera system, the energy-dispersive spectrometer has an energy resolution (E/ΔE) of approximately 12,000 at 930 eV. A recent study predicted that through an upgrade to the grating and camera system, the energy resolution could be improved by a factor of 2. In order to achieve this goal in the spectral domain, the spatial resolution of the CCD must be improved to better than 5 μm from the current 24 μm spatial resolution (FWHM). The 400 eV-1600 eV energy X-rays detected by this spectrometer primarily interact within the field free region of the CCD, producing electron clouds which will diffuse isotropically until they reach the depleted region and buried channel. This diffusion of the charge leads to events which are split across several pixels. Through the analysis of the charge distribution across the pixels, various centroiding techniques can be used to pinpoint the spatial location of the X-ray interaction to the sub-pixel level, greatly improving the spatial resolution achieved. Using the PolLux soft X-ray microspectroscopy endstation at the Swiss Light Source, a beam of X-rays of energies from 200 eV to 1400 eV can be focused down to a spot size of approximately 20 nm. Scanning this spot across the 16 μm square pixels allows the sub-pixel response to be investigated. Previous work has demonstrated the potential improvement in spatial resolution achievable by centroiding events in a standard CCD. An Electron-Multiplying CCD (EM-CCD) has been used to improve the signal to effective readout noise ratio achieved resulting in a worst-case spatial resolution measurement of 4.5±0.2 μm and 3.9±0.1 μm at 530 eV and 680 eV respectively. A method is described that allows the contribution of the X-ray spot size to be deconvolved from these worst-case resolution measurements, estimating the spatial resolution to be approximately 3.5 μm and 3.0 μm at 530 eV and 680 eV, well below the resolution limit of 5 μm required to improve the spectral resolution by a factor of 2.

A High Resolution TDI CCD Camera forMicrosatellite (HRCM)

NASA Astrophysics Data System (ADS)

Hao, Yuncai; Zheng, You; Dong, Ying; Li, Tao; Yu, Shijie

In resent years it is a important development direction in the commercial remote sensing field to obtain (1-5)m high ground resolution from space using microsatellite. Thanks to progress of new technologies, new materials and new detectors it is possible to develop 1m ground resolution space imaging system with weight less than 20kg. Based on many years works on optical system design a project of very high resolution TDI CCD camera using in space was proposed by the authors of this paper. The performance parameters and optical lay-out of the HRCM was presented. A compact optical design and results analysis for the system was given in the paper also. and small fold mirror to take a line field of view usable for TDI CCD and short outer size. The length along the largest size direction is about 1/4 of the focal length. And two 4096X96(grades) line TDI CCD will be used as the focal plane detector. The special optical parts are fixed near before the final image for getting the ground pixel resolution higher than the Nyquist resolution of the detector using the sub-pixel technique which will be explained in the paper. In the system optical SiC will be used as the mirror material, the C-C composite material will be used as the material of the mechanical structure framework. The circle frame of the primary and secondary mirrors will use one time turning on a machine tool in order to assuring concentric request for alignment of the system. In general the HRCM have the performance parameters with 2.5m focal length, 20 FOV, 1/11relative aperture, (0.4-0.8) micrometer spectral range, 10 micron pixel size of TDI CCD, weight less than 20kg, 1m ground pixel resolution at flying orbit 500km high. Design and analysis of the HRCM put up in the paper indicate that HRCM have many advantages to use it in space. Keywords High resolution TDI CCD Sub-pixel imaging Light-weighted optical system SiC mirror

Resolution-independent surface rendering using programmable graphics hardware

DOEpatents

Loop, Charles T.; Blinn, James Frederick

2008-12-16

Surfaces defined by a Bezier tetrahedron, and in particular quadric surfaces, are rendered on programmable graphics hardware. Pixels are rendered through triangular sides of the tetrahedra and locations on the shapes, as well as surface normals for lighting evaluations, are computed using pixel shader computations. Additionally, vertex shaders are used to aid interpolation over a small number of values as input to the pixel shaders. Through this, rendering of the surfaces is performed independently of viewing resolution, allowing for advanced level-of-detail management. By individually rendering tetrahedrally-defined surfaces which together form complex shapes, the complex shapes can be rendered in their entirety.

A single pixel camera video ophthalmoscope

NASA Astrophysics Data System (ADS)

Lochocki, B.; Gambin, A.; Manzanera, S.; Irles, E.; Tajahuerce, E.; Lancis, J.; Artal, P.

2017-02-01

There are several ophthalmic devices to image the retina, from fundus cameras capable to image the whole fundus to scanning ophthalmoscopes with photoreceptor resolution. Unfortunately, these devices are prone to a variety of ocular conditions like defocus and media opacities, which usually degrade the quality of the image. Here, we demonstrate a novel approach to image the retina in real-time using a single pixel camera, which has the potential to circumvent those optical restrictions. The imaging procedure is as follows: a set of spatially coded patterns is projected rapidly onto the retina using a digital micro mirror device. At the same time, the inner product's intensity is measured for each pattern with a photomultiplier module. Subsequently, an image of the retina is reconstructed computationally. Obtained image resolution is up to 128 x 128 px with a varying real-time video framerate up to 11 fps. Experimental results obtained in an artificial eye confirm the tolerance against defocus compared to a conventional multi-pixel array based system. Furthermore, the use of a multiplexed illumination offers a SNR improvement leading to a lower illumination of the eye and hence an increase in patient's comfort. In addition, the proposed system could enable imaging in wavelength ranges where cameras are not available.

Estimation of sub-pixel water area on Tibet plateau using multiple endmembers spectral mixture spectral analysis from MODIS data

NASA Astrophysics Data System (ADS)

Cui, Qian; Shi, Jiancheng; Xu, Yuanliu

2011-12-01

Water is the basic needs for human society, and the determining factor of stability of ecosystem as well. There are lots of lakes on Tibet Plateau, which will lead to flood and mudslide when the water expands sharply. At present, water area is extracted from TM or SPOT data for their high spatial resolution; however, their temporal resolution is insufficient. MODIS data have high temporal resolution and broad coverage. So it is valuable resource for detecting the change of water area. Because of its low spatial resolution, mixed-pixels are common. In this paper, four spectral libraries are built using MOD09A1 product, based on that, water body is extracted in sub-pixels utilizing Multiple Endmembers Spectral Mixture Analysis (MESMA) using MODIS daily reflectance data MOD09GA. The unmixed result is comparing with contemporaneous TM data and it is proved that this method has high accuracy.

Test beam performance measurements for the Phase I upgrade of the CMS pixel detector

NASA Astrophysics Data System (ADS)

Dragicevic, M.; Friedl, M.; Hrubec, J.; Steininger, H.; Gädda, A.; Härkönen, J.; Lampén, T.; Luukka, P.; Peltola, T.; Tuominen, E.; Tuovinen, E.; Winkler, A.; Eerola, P.; Tuuva, T.; Baulieu, G.; Boudoul, G.; Caponetto, L.; Combaret, C.; Contardo, D.; Dupasquier, T.; Gallbit, G.; Lumb, N.; Mirabito, L.; Perries, S.; Vander Donckt, M.; Viret, S.; Bonnin, C.; Charles, L.; Gross, L.; Hosselet, J.; Tromson, D.; Feld, L.; Karpinski, W.; Klein, K.; Lipinski, M.; Pierschel, G.; Preuten, M.; Rauch, M.; Wlochal, M.; Aldaya, M.; Asawatangtrakuldee, C.; Beernaert, K.; Bertsche, D.; Contreras-Campana, C.; Eckerlin, G.; Eckstein, D.; Eichhorn, T.; Gallo, E.; Garay Garcia, J.; Hansen, K.; Haranko, M.; Harb, A.; Hauk, J.; Keaveney, J.; Kalogeropoulos, A.; Kleinwort, C.; Lohmann, W.; Mankel, R.; Maser, H.; Mittag, G.; Muhl, C.; Mussgiller, A.; Pitzl, D.; Reichelt, O.; Savitskyi, M.; Schütze, P.; Sola, V.; Spannagel, S.; Walsh, R.; Zuber, A.; Biskop, H.; Buhmann, P.; Centis-Vignali, M.; Garutti, E.; Haller, J.; Hoffmann, M.; Klanner, R.; Lapsien, T.; Matysek, M.; Perieanu, A.; Scharf, Ch.; Schleper, P.; Schmidt, A.; Schwandt, J.; Sonneveld, J.; Steinbrück, G.; Vormwald, B.; Wellhausen, J.; Abbas, M.; Amstutz, C.; Barvich, T.; Barth, Ch.; Boegelspacher, F.; De Boer, W.; Butz, E.; Casele, M.; Colombo, F.; Dierlamm, A.; Freund, B.; Hartmann, F.; Heindl, S.; Husemann, U.; Kornmeyer, A.; Kudella, S.; Muller, Th.; Simonis, H. J.; Steck, P.; Weber, M.; Weiler, Th.; Kiss, T.; Siklér, F.; Tölyhi, T.; Veszprémi, V.; Cariola, P.; Creanza, D.; De Palma, M.; De Robertis, G.; Fiore, L.; Franco, M.; Loddo, F.; Sala, G.; Silvestris, L.; Maggi, G.; My, S.; Selvaggi, G.; Albergo, S.; Cappello, G.; Costa, S.; Di Mattia, A.; Giordano, F.; Potenza, R.; Saizu, M. A.; Tricomi, A.; Tuve, C.; Focardi, E.; Dinardo, M. E.; Fiorendi, S.; Gennai, S.; Malvezzi, S.; Manzoni, R. A.; Menasce, D.; Moroni, L.; Pedrini, D.; Azzi, P.; Bacchetta, N.; Bisello, D.; Dall'Osso, M.; Pozzobon, N.; Tosi, M.; Alunni Solestizi, L.; Biasini, M.; Bilei, G. M.; Cecchi, C.; Checcucci, B.; Ciangottini, D.; Fanò, L.; Gentsos, C.; Ionica, M.; Leonardi, R.; Manoni, E.; Mantovani, G.; Marconi, S.; Mariani, V.; Menichelli, M.; Modak, A.; Morozzi, A.; Moscatelli, F.; Passeri, D.; Placidi, P.; Postolache, V.; Rossi, A.; Saha, A.; Santocchia, A.; Storchi, L.; Spiga, D.; Androsov, K.; Azzurri, P.; Bagliesi, G.; Basti, A.; Boccali, T.; Borrello, L.; Bosi, F.; Castaldi, R.; Ceccanti, M.; Ciocci, M. A.; Dell'Orso, R.; Donato, S.; Fedi, G.; Giassi, A.; Grippo, M. T.; Ligabue, F.; Magazzu, G.; Mammini, P.; Mariani, F.; Mazzoni, E.; Messineo, A.; Moggi, A.; Morsani, F.; Palla, F.; Palmonari, F.; Profeti, A.; Raffaelli, F.; Ragonesi, A.; Rizzi, A.; Soldani, A.; Spagnolo, P.; Tenchini, R.; Tonelli, G.; Venturi, A.; Verdini, P. G.; Abbaneo, D.; Ahmed, I.; Albert, E.; Auzinger, G.; Berruti, G.; Bonnaud, J.; Daguin, J.; D'Auria, A.; Detraz, S.; Dondelewski, O.; Engegaard, B.; Faccio, F.; Frank, N.; Gill, K.; Honma, A.; Kornmayer, A.; Labaza, A.; Manolescu, F.; McGill, I.; Mersi, S.; Michelis, S.; Onnela, A.; Ostrega, M.; Pavis, S.; Peisert, A.; Pernot, J.-F.; Petagna, P.; Postema, H.; Rapacz, K.; Sigaud, C.; Tropea, P.; Troska, J.; Tsirou, A.; Vasey, F.; Verlaat, B.; Vichoudis, P.; Zwalinski, L.; Bachmair, F.; Becker, R.; di Calafiori, D.; Casal, B.; Berger, P.; Djambazov, L.; Donega, M.; Grab, C.; Hits, D.; Hoss, J.; Kasieczka, G.; Lustermann, W.; Mangano, B.; Marionneau, M.; Martinez Ruiz del Arbol, P.; Masciovecchio, M.; Meinhard, M.; Perozzi, L.; Roeser, U.; Starodumov, A.; Tavolaro, V.; Wallny, R.; Zhu, D.; Amsler, C.; Bösiger, K.; Caminada, L.; Canelli, F.; Chiochia, V.; de Cosa, A.; Galloni, C.; Hreus, T.; Kilminster, B.; Lange, C.; Maier, R.; Ngadiuba, J.; Pinna, D.; Robmann, P.; Taroni, S.; Yang, Y.; Bertl, W.; Deiters, K.; Erdmann, W.; Horisberger, R.; Kaestli, H.-C.; Kotlinski, D.; Langenegger, U.; Meier, B.; Rohe, T.; Streuli, S.; Chen, P.-H.; Dietz, C.; Fiori, F.; Grundler, U.; Hou, W.-S.; Lu, R.-S.; Moya, M.; Tsai, J.-F.; Tzeng, Y. M.; Cussans, D.; Goldstein, J.; Grimes, M.; Newbold, D.; Hobson, P.; Reid, I. D.; Auzinger, G.; Bainbridge, R.; Dauncey, P.; Hall, G.; James, T.; Magnan, A.-M.; Pesaresi, M.; Raymond, D. M.; Uchida, K.; Durkin, T.; Harder, K.; Shepherd-Themistocleous, C.; Chertok, M.; Conway, J.; Conway, R.; Flores, C.; Lander, R.; Pellett, D.; Ricci-Tam, F.; Squires, M.; Thomson, J.; Yohay, R.; Burt, K.; Ellison, J.; Hanson, G.; Olmedo, M.; Si, W.; Yates, B. R.; Dominguez, A.; Bartek, R.; Bentele, B.; Cumalat, J. P.; Ford, W. T.; Jensen, F.; Johnson, A.; Krohn, M.; Leontsinis, S.; Mulholland, T.; Stenson, K.; Wagner, S. R.; Apresyan, A.; Bolla, G.; Burkett, K.; Butler, J. N.; Canepa, A.; Cheung, H. W. K.; Christian, D.; Cooper, W. E.; Deptuch, G.; Derylo, G.; Gingu, C.; Grünendahl, S.; Hasegawa, S.; Hoff, J.; Howell, J.; Hrycyk, M.; Jindariani, S.; Johnson, M.; Kahlid, F.; Kwan, S.; Lei, C. M.; Lipton, R.; Lopes De Sá, R.; Liu, T.; Los, S.; Matulik, M.; Merkel, P.; Nahn, S.; Prosser, A.; Rivera, R.; Schneider, B.; Sellberg, G.; Shenai, A.; Siehl, K.; Spiegel, L.; Tran, N.; Uplegger, L.; Voirin, E.; Berry, D. R.; Chen, X.; Ennesser, L.; Evdokimov, A.; Gerber, C. E.; Makauda, S.; Mills, C.; Sandoval Gonzalez, I. D.; Alimena, J.; Antonelli, L. J.; Francis, B.; Hart, A.; Hill, C. S.; Parashar, N.; Stupak, J.; Bortoletto, D.; Bubna, M.; Hinton, N.; Jones, M.; Miller, D. H.; Shi, X.; Baringer, P.; Bean, A.; Khalil, S.; Kropivnitskaya, A.; Majumder, D.; Schmitz, E.; Wilson, G.; Ivanov, A.; Mendis, R.; Mitchell, T.; Skhirtladze, N.; Taylor, R.; Anderson, I.; Fehling, D.; Gritsan, A.; Maksimovic, P.; Martin, C.; Nash, K.; Osherson, M.; Swartz, M.; Xiao, M.; Acosta, J. G.; Cremaldi, L. M.; Oliveros, S.; Perera, L.; Summers, D.; Bloom, K.; Claes, D. R.; Fangmeier, C.; Gonzalez Suarez, R.; Monroy, J.; Siado, J.; Bartz, E.; Gershtein, Y.; Halkiadakis, E.; Kyriacou, S.; Lath, A.; Nash, K.; Osherson, M.; Schnetzer, S.; Stone, R.; Walker, M.; Malik, S.; Norberg, S.; Ramirez Vargas, J. E.; Alyari, M.; Dolen, J.; Godshalk, A.; Harrington, C.; Iashvili, I.; Kharchilava, A.; Nguyen, D.; Parker, A.; Rappoccio, S.; Roozbahani, B.; Alexander, J.; Chaves, J.; Chu, J.; Dittmer, S.; McDermott, K.; Mirman, N.; Rinkevicius, A.; Ryd, A.; Salvati, E.; Skinnari, L.; Soffi, L.; Tao, Z.; Thom, J.; Tucker, J.; Zientek, M.; Akgün, B.; Ecklund, K. M.; Kilpatrick, M.; Nussbaum, T.; Zabel, J.; D'Angelo, P.; Johns, W.; Rose, K.; Choudhury, S.; Korol, I.; Seitz, C.; Vargas Trevino, A.; Dolinska, G.

2017-05-01

A new pixel detector for the CMS experiment was built in order to cope with the instantaneous luminosities anticipated for the Phase I Upgrade of the LHC . The new CMS pixel detector provides four-hit tracking with a reduced material budget as well as new cooling and powering schemes. A new front-end readout chip mitigates buffering and bandwidth limitations, and allows operation at low comparator thresholds. In this paper, comprehensive test beam studies are presented, which have been conducted to verify the design and to quantify the performance of the new detector assemblies in terms of tracking efficiency and spatial resolution. Under optimal conditions, the tracking efficiency is 99.95 ± 0.05%, while the intrinsic spatial resolutions are 4.80 ± 0.25 μm and 7.99 ± 0.21 μm along the 100 μm and 150 μm pixel pitch, respectively. The findings are compared to a detailed Monte Carlo simulation of the pixel detector and good agreement is found.

Evaluation of a hybrid pixel detector for electron microscopy.

PubMed

Faruqi, A R; Cattermole, D M; Henderson, R; Mikulec, B; Raeburn, C

2003-04-01

We describe the application of a silicon hybrid pixel detector, containing 64 by 64 pixels, each 170 microm(2), in electron microscopy. The device offers improved resolution compared to CCDs along with faster and noiseless readout. Evaluation of the detector, carried out on a 120 kV electron microscope, demonstrates the potential of the device.

Global-scale patterns of forest fragmentation

Treesearch

Kurt H. Riitters; James D. Wickham; R. O' Neill; B. Jones; E. Smith

2000-01-01

We report an analysis of forest fragmentation based on 1-km resolution land-cover maps for the globe. Measurements in analysis windows from 81 km 2 (9 x 9 pixels, "small" scale) to 59,049 km 2 (243 x 243 pixels, "large" scale) were used to characterize the fragmentation around each forested pixel. We identified six categories of fragmentation (...

High-resolution low-dose scanning transmission electron microscopy.

PubMed

Buban, James P; Ramasse, Quentin; Gipson, Bryant; Browning, Nigel D; Stahlberg, Henning

2010-01-01

During the past two decades instrumentation in scanning transmission electron microscopy (STEM) has pushed toward higher intensity electron probes to increase the signal-to-noise ratio of recorded images. While this is suitable for robust specimens, biological specimens require a much reduced electron dose for high-resolution imaging. We describe here protocols for low-dose STEM image recording with a conventional field-emission gun STEM, while maintaining the high-resolution capability of the instrument. Our findings show that a combination of reduced pixel dwell time and reduced gun current can achieve radiation doses comparable to low-dose TEM.

High Spectral Resolution, High Cadence, Imaging X-Ray Microcalorimeters for Solar Physics

NASA Technical Reports Server (NTRS)

Bandler, Simon R.; Bailey, Catherine N.; Bookbinder, Jay A.; DeLuca, Edward E.; Chervenak, Jay A.; Eckart, Megan E.; Finkbeiner, Fred M.; Kelley, Daniel P.; Kelley, Richard L.; Kilbourne, Caroline A.;

Comparative performance evaluation of a new a-Si EPID that exceeds quad high-definition resolution.

PubMed

McConnell, Kristen A; Alexandrian, Ara; Papanikolaou, Niko; Stathakis, Sotiri

2018-01-01

Electronic portal imaging devices (EPIDs) are an integral part of the radiation oncology workflow for treatment setup verification. Several commercial EPID implementations are currently available, each with varying capabilities. To standardize performance evaluation, Task Group Report 58 (TG-58) and TG-142 outline specific image quality metrics to be measured. A LinaTech Image Viewing System (IVS), with the highest commercially available pixel matrix (2688x2688 pixels), was independently evaluated and compared to an Elekta iViewGT (1024x1024 pixels) and a Varian aSi-1000 (1024x768 pixels) using a PTW EPID QC Phantom. The IVS, iViewGT, and aSi-1000 were each used to acquire 20 images of the PTW QC Phantom. The QC phantom was placed on the couch and aligned at isocenter. The images were exported and analyzed using the epidSoft image quality assurance (QA) software. The reported metrics were signal linearity, isotropy of signal linearity, signal-tonoise ratio (SNR), low contrast resolution, and high-contrast resolution. These values were compared between the three EPID solutions. Computed metrics demonstrated comparable results between the EPID solutions with the IVS outperforming the aSi-1000 and iViewGT in the low and high-contrast resolution analysis. The performance of three commercial EPID solutions have been quantified, evaluated, and compared using results from the PTW QC Phantom. The IVS outperformed the other panels in low and high-contrast resolution, but to fully realize the benefits of the IVS, the selection of the monitor on which to view the high-resolution images is important to prevent down sampling and visual of resolution.

Super-resolution for imagery from integrated microgrid polarimeters.

PubMed

Hardie, Russell C; LeMaster, Daniel A; Ratliff, Bradley M

2011-07-04

Imagery from microgrid polarimeters is obtained by using a mosaic of pixel-wise micropolarizers on a focal plane array (FPA). Each distinct polarization image is obtained by subsampling the full FPA image. Thus, the effective pixel pitch for each polarization channel is increased and the sampling frequency is decreased. As a result, aliasing artifacts from such undersampling can corrupt the true polarization content of the scene. Here we present the first multi-channel multi-frame super-resolution (SR) algorithms designed specifically for the problem of image restoration in microgrid polarization imagers. These SR algorithms can be used to address aliasing and other degradations, without sacrificing field of view or compromising optical resolution with an anti-aliasing filter. The new SR methods are designed to exploit correlation between the polarimetric channels. One of the new SR algorithms uses a form of regularized least squares and has an iterative solution. The other is based on the faster adaptive Wiener filter SR method. We demonstrate that the new multi-channel SR algorithms are capable of providing significant enhancement of polarimetric imagery and that they outperform their independent channel counterparts.

Towards a real-time wide area motion imagery system

NASA Astrophysics Data System (ADS)

Young, R. I.; Foulkes, S. B.

2015-10-01

It is becoming increasingly important in both the defence and security domains to conduct persistent wide area surveillance (PWAS) of large populations of targets. Wide Area Motion Imagery (WAMI) is a key technique for achieving this wide area surveillance. The recent development of multi-million pixel sensors has provided sensors with wide field of view replete with sufficient resolution for detection and tracking of objects of interest to be achieved across these extended areas of interest. WAMI sensors simultaneously provide high spatial and temporal resolutions, giving extreme pixel counts over large geographical areas. The high temporal resolution is required to enable effective tracking of targets. The provision of wide area coverage with high frame rates generates data deluge issues; these are especially profound if the sensor is mounted on an airborne platform, with finite data-link bandwidth and processing power that is constrained by size, weight and power (SWAP) limitations. These issues manifest themselves either as bottlenecks in the transmission of the imagery off-board or as latency in the time taken to analyse the data due to limited computational processing power.

Microstructural analysis of aluminum high pressure die castings

NASA Astrophysics Data System (ADS)

David, Maria Diana

Microstructural analysis of aluminum high pressure die castings (HPDC) is challenging and time consuming. Automating the stereology method is an efficient way in obtaining quantitative data; however, validating the accuracy of this technique can also pose some challenges. In this research, a semi-automated algorithm to quantify microstructural features in aluminum HPDC was developed. Analysis was done near the casting surface where it exhibited fine microstructure. Optical and Secondary electron (SE) and backscatter electron (BSE) SEM images were taken to characterize the features in the casting. Image processing steps applied on SEM and optical micrographs included median and range filters, dilation, erosion, and a hole-closing function. Measurements were done on different image pixel resolutions that ranged from 3 to 35 pixel/μm. Pixel resolutions below 6 px/μm were too low for the algorithm to distinguish the phases from each other. At resolutions higher than 6 px/μm, the volume fraction of primary α-Al and the line intercept count curves plateaued. Within this range, comparable results were obtained validating the assumption that there is a range of image pixel resolution relative to the size of the casting features at which stereology measurements become independent of the image resolution. Volume fraction within this curve plateau was consistent with the manual measurements while the line intercept count was significantly higher using the computerized technique for all resolutions. This was attributed to the ragged edges of some primary α-Al; hence, the algorithm still needs some improvements. Further validation of the code using other castings or alloys with known phase amount and size may also be beneficial.

Optimized light sharing for high-resolution TOF PET detector based on digital silicon photomultipliers.

PubMed

Marcinkowski, R; España, S; Van Holen, R; Vandenberghe, S

2014-12-07

The majority of current whole-body PET scanners are based on pixelated scintillator arrays with a transverse pixel size of 4 mm. However, recent studies have shown that decreasing the pixel size to 2 mm can significantly improve image spatial resolution. In this study, the performance of Digital Photon Counter (DPC) from Philips Digital Photon Counting (PDPC) was evaluated to determine their potential for high-resolution whole-body time of flight (TOF) PET scanners. Two detector configurations were evaluated. First, the DPC3200-44-22 DPC array was coupled to a LYSO block of 15 × 15 2 × 2 × 22 mm(3) pixels through a 1 mm thick light guide. Due to light sharing among the dies neighbour logic of the DPC was used. In a second setup the same DPC was coupled directly to a scalable 4 × 4 LYSO matrix of 1.9 × 1.9 × 22 mm(3) crystals with a dedicated reflector arrangement allowing for controlled light sharing patterns inside the matrix. With the first approach an average energy resolution of 14.5% and an average CRT of 376 ps were achieved. For the second configuration an average energy resolution of 11% and an average CRT of 295 ps were achieved. Our studies show that the DPC is a suitable photosensor for a high-resolution TOF-PET detector. The dedicated reflector arrangement allows one to achieve better performances than the light guide approach. The count loss, caused by dark counts, is overcome by fitting the matrix size to the size of DPC single die.

Application of Skylab EREP data for land use management

NASA Technical Reports Server (NTRS)

Simonett, D. S. (Principal Investigator)

1976-01-01

The author has identified the following significant results. The 1.09-1.19 micron band proved to be very valuable for discriminating a variety of land use categories, including agriculture, forest, and urban classes. The 1.55-1.75 micron band proved very useful in combination with the 1.09-1.19 micron band. Misregistration between spectral bands, even by as little as 1/2 pixel, may degrade classification accuracy. Identification accuracy of boundary or border pixels was as much as 13% lower than the accuracy for identifying internal field pixels. The principal conclusion with respect to the S190B camera system is that the higher resolution of the S190B system in comparison to previous space photography (Gemini, Apollo), to the S190A system (Skylab), and to LANDSAT imagery significantly increases the range of additional discrimination achievable.

Strategies for high-throughput focused-beam ptychography

DOE PAGES

Jacobsen, Chris; Deng, Junjing; Nashed, Youssef

2017-08-08

X-ray ptychography is being utilized for a wide range of imaging experiments with a resolution beyond the limit of the X-ray optics used. Introducing a parameter for the ptychographic resolution gainG p(the ratio of the beam size over the achieved pixel size in the reconstructed image), strategies for data sampling and for increasing imaging throughput when the specimen is at the focus of an X-ray beam are considered. As a result, the tradeoffs between large and small illumination spots are examined.

Strategies for high-throughput focused-beam ptychography

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jacobsen, Chris; Deng, Junjing; Nashed, Youssef

X-ray ptychography is being utilized for a wide range of imaging experiments with a resolution beyond the limit of the X-ray optics used. Introducing a parameter for the ptychographic resolution gainG p(the ratio of the beam size over the achieved pixel size in the reconstructed image), strategies for data sampling and for increasing imaging throughput when the specimen is at the focus of an X-ray beam are considered. As a result, the tradeoffs between large and small illumination spots are examined.

Improved accuracy of quantitative parameter estimates in dynamic contrast-enhanced CT study with low temporal resolution

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kim, Sun Mo, E-mail: Sunmo.Kim@rmp.uhn.on.ca; Haider, Masoom A.; Jaffray, David A.

Purpose: A previously proposed method to reduce radiation dose to patient in dynamic contrast-enhanced (DCE) CT is enhanced by principal component analysis (PCA) filtering which improves the signal-to-noise ratio (SNR) of time-concentration curves in the DCE-CT study. The efficacy of the combined method to maintain the accuracy of kinetic parameter estimates at low temporal resolution is investigated with pixel-by-pixel kinetic analysis of DCE-CT data. Methods: The method is based on DCE-CT scanning performed with low temporal resolution to reduce the radiation dose to the patient. The arterial input function (AIF) with high temporal resolution can be generated with a coarselymore » sampled AIF through a previously published method of AIF estimation. To increase the SNR of time-concentration curves (tissue curves), first, a region-of-interest is segmented into squares composed of 3 × 3 pixels in size. Subsequently, the PCA filtering combined with a fraction of residual information criterion is applied to all the segmented squares for further improvement of their SNRs. The proposed method was applied to each DCE-CT data set of a cohort of 14 patients at varying levels of down-sampling. The kinetic analyses using the modified Tofts’ model and singular value decomposition method, then, were carried out for each of the down-sampling schemes between the intervals from 2 to 15 s. The results were compared with analyses done with the measured data in high temporal resolution (i.e., original scanning frequency) as the reference. Results: The patients’ AIFs were estimated to high accuracy based on the 11 orthonormal bases of arterial impulse responses established in the previous paper. In addition, noise in the images was effectively reduced by using five principal components of the tissue curves for filtering. Kinetic analyses using the proposed method showed superior results compared to those with down-sampling alone; they were able to maintain the accuracy in the quantitative histogram parameters of volume transfer constant [standard deviation (SD), 98th percentile, and range], rate constant (SD), blood volume fraction (mean, SD, 98th percentile, and range), and blood flow (mean, SD, median, 98th percentile, and range) for sampling intervals between 10 and 15 s. Conclusions: The proposed method of PCA filtering combined with the AIF estimation technique allows low frequency scanning for DCE-CT study to reduce patient radiation dose. The results indicate that the method is useful in pixel-by-pixel kinetic analysis of DCE-CT data for patients with cervical cancer.« less

LSA SAF Meteosat FRP products - Part 2: Evaluation and demonstration for use in the Copernicus Atmosphere Monitoring Service (CAMS)

NASA Astrophysics Data System (ADS)

Roberts, G.; Wooster, M. J.; Xu, W.; Freeborn, P. H.; Morcrette, J.-J.; Jones, L.; Benedetti, A.; Jiangping, H.; Fisher, D.; Kaiser, J. W.

2015-11-01

Characterising the dynamics of landscape-scale wildfires at very high temporal resolutions is best achieved using observations from Earth Observation (EO) sensors mounted onboard geostationary satellites. As a result, a number of operational active fire products have been developed from the data of such sensors. An example of which are the Fire Radiative Power (FRP) products, the FRP-PIXEL and FRP-GRID products, generated by the Land Surface Analysis Satellite Applications Facility (LSA SAF) from imagery collected by the Spinning Enhanced Visible and Infrared Imager (SEVIRI) onboard the Meteosat Second Generation (MSG) series of geostationary EO satellites. The processing chain developed to deliver these FRP products detects SEVIRI pixels containing actively burning fires and characterises their FRP output across four geographic regions covering Europe, part of South America and Northern and Southern Africa. The FRP-PIXEL product contains the highest spatial and temporal resolution FRP data set, whilst the FRP-GRID product contains a spatio-temporal summary that includes bias adjustments for cloud cover and the non-detection of low FRP fire pixels. Here we evaluate these two products against active fire data collected by the Moderate Resolution Imaging Spectroradiometer (MODIS) and compare the results to those for three alternative active fire products derived from SEVIRI imagery. The FRP-PIXEL product is shown to detect a substantially greater number of active fire pixels than do alternative SEVIRI-based products, and comparison to MODIS on a per-fire basis indicates a strong agreement and low bias in terms of FRP values. However, low FRP fire pixels remain undetected by SEVIRI, with errors of active fire pixel detection commission and omission compared to MODIS ranging between 9-13 % and 65-77 % respectively in Africa. Higher errors of omission result in greater underestimation of regional FRP totals relative to those derived from simultaneously collected MODIS data, ranging from 35 % over the Northern Africa region to 89 % over the European region. High errors of active fire omission and FRP underestimation are found over Europe and South America and result from SEVIRI's larger pixel area over these regions. An advantage of using FRP for characterising wildfire emissions is the ability to do so very frequently and in near-real time (NRT). To illustrate the potential of this approach, wildfire fuel consumption rates derived from the SEVIRI FRP-PIXEL product are used to characterise smoke emissions of the 2007 "mega-fire" event focused on Peloponnese (Greece) and used within the European Centre for Medium-Range Weather Forecasting (ECMWF) Integrated Forecasting System (IFS) as a demonstration of what can be achieved when using geostationary active fire data within the Copernicus Atmosphere Monitoring Service (CAMS). Qualitative comparison of the modelled smoke plumes with MODIS optical imagery illustrates that the model captures the temporal and spatial dynamics of the plume very well, and that high temporal resolution emissions estimates such as those available from a geostationary orbit are important for capturing the sub-daily variability in smoke plume parameters such as aerosol optical depth (AOD), which are increasingly less well resolved using daily or coarser temporal resolution emissions data sets. Quantitative comparison of modelled AOD with coincident MODIS and AERONET (Aerosol Robotic Network) AOD indicates that the former is overestimated by ~ 20-30 %, but captures the observed AOD dynamics with a high degree of fidelity. The case study highlights the potential of using geostationary FRP data to drive fire emissions estimates for use within atmospheric transport models such as those implemented in the Monitoring Atmospheric Composition and Climate (MACC) series of projects for the CAMS.

Amorphous selenium direct detection CMOS digital x-ray imager with 25 micron pixel pitch

NASA Astrophysics Data System (ADS)

Scott, Christopher C.; Abbaszadeh, Shiva; Ghanbarzadeh, Sina; Allan, Gary; Farrier, Michael; Cunningham, Ian A.; Karim, Karim S.

2014-03-01

We have developed a high resolution amorphous selenium (a-Se) direct detection imager using a large-area compatible back-end fabrication process on top of a CMOS active pixel sensor having 25 micron pixel pitch. Integration of a-Se with CMOS technology requires overcoming CMOS/a-Se interfacial strain, which initiates nucleation of crystalline selenium and results in high detector dark currents. A CMOS-compatible polyimide buffer layer was used to planarize the backplane and provide a low stress and thermally stable surface for a-Se. The buffer layer inhibits crystallization and provides detector stability that is not only a performance factor but also critical for favorable long term cost-benefit considerations in the application of CMOS digital x-ray imagers in medical practice. The detector structure is comprised of a polyimide (PI) buffer layer, the a-Se layer, and a gold (Au) top electrode. The PI layer is applied by spin-coating and is patterned using dry etching to open the backplane bond pads for wire bonding. Thermal evaporation is used to deposit the a-Se and Au layers, and the detector is operated in hole collection mode (i.e. a positive bias on the Au top electrode). High resolution a-Se diagnostic systems typically use 70 to 100 μm pixel pitch and have a pre-sampling modulation transfer function (MTF) that is significantly limited by the pixel aperture. Our results confirm that, for a densely integrated 25 μm pixel pitch CMOS array, the MTF approaches the fundamental material limit, i.e. where the MTF begins to be limited by the a-Se material properties and not the pixel aperture. Preliminary images demonstrating high spatial resolution have been obtained from a frst prototype imager.

Charge Loss and Charge Sharing Measurements for Two Different Pixelated Cadmium-Zinc-Telluride Detectors

NASA Technical Reports Server (NTRS)

Gaskin, Jessica; Sharma, Dharma; Ramsey, Brian; Seller, Paul

2003-01-01

As part of ongoing research at Marshall Space Flight Center, Cadmium-Zinc- Telluride (CdZnTe) pixilated detectors are being developed for use at the focal plane of the High Energy Replicated Optics (HERO) telescope. HERO requires a 64x64 pixel array with a spatial resolution of around 200 microns (with a 6m focal length) and high energy resolution (< 2% at 60keV). We are currently testing smaller arrays as a necessary first step towards this goal. In this presentation, we compare charge sharing and charge loss measurements between two devices that differ both electronically and geometrically. The first device consists of a 1-mm-thick piece of CdZnTe that is sputtered with a 4x4 array of pixels with pixel pitch of 750 microns (inter-pixel gap is 100 microns). The signal is read out using discrete ultra-low-noise preamplifiers, one for each of the 16 pixels. The second detector consists of a 2-mm-thick piece of CdZnTe that is sputtered with a 16x16 array of pixels with a pixel pitch of 300 microns (inter-pixel gap is 50 microns). Instead of using discrete preamplifiers, the crystal is bonded to an ASIC that provides all of the front-end electronics to each of the 256 pixels. what degree the bias voltage (i.e. the electric field) and hence the drift and diffusion coefficients affect our measurements. Further, we compare the measured results with simulated results and discuss to

Toward VIP-PIX: A Low Noise Readout ASIC for Pixelated CdTe Gamma-Ray Detectors for Use in the Next Generation of PET Scanners.

PubMed

Macias-Montero, Jose-Gabriel; Sarraj, Maher; Chmeissani, Mokhtar; Puigdengoles, Carles; Lorenzo, Gianluca De; Martínez, Ricardo

2013-08-01

VIP-PIX will be a low noise and low power pixel readout electronics with digital output for pixelated Cadmium Telluride (CdTe) detectors. The proposed pixel will be part of a 2D pixel-array detector for various types of nuclear medicine imaging devices such as positron-emission tomography (PET) scanners, Compton gamma cameras, and positron-emission mammography (PEM) scanners. Each pixel will include a SAR ADC that provides the energy deposited with 10-bit resolution. Simultaneously, the self-triggered pixel which will be connected to a global time-to-digital converter (TDC) with 1 ns resolution will provide the event's time stamp. The analog part of the readout chain and the ADC have been fabricated with TSMC 0.25 μ m mixed-signal CMOS technology and characterized with an external test pulse. The power consumption of these parts is 200 μ W from a 2.5 V supply. It offers 4 switchable gains from ±10 mV/fC to ±40 mV/fC and an input charge dynamic range of up to ±70 fC for the minimum gain for both polarities. Based on noise measurements, the expected equivalent noise charge (ENC) is 65 e - RMS at room temperature.

Simulation study of pixel detector charge digitization

NASA Astrophysics Data System (ADS)

Wang, Fuyue; Nachman, Benjamin; Sciveres, Maurice; Lawrence Berkeley National Laboratory Team

2017-01-01

Reconstruction of tracks from nearly overlapping particles, called Tracking in Dense Environments (TIDE), is an increasingly important component of many physics analyses at the Large Hadron Collider as signatures involving highly boosted jets are investigated. TIDE makes use of the charge distribution inside a pixel cluster to resolve tracks that share one of more of their pixel detector hits. In practice, the pixel charge is discretized using the Time-over-Threshold (ToT) technique. More charge information is better for discrimination, but more challenging for designing and operating the detector. A model of the silicon pixels has been developed in order to study the impact of the precision of the digitized charge distribution on distinguishing multi-particle clusters. The output of the GEANT4-based simulation is used to train neutral networks that predict the multiplicity and location of particles depositing energy inside one cluster of pixels. By studying the multi-particle cluster identification efficiency and position resolution, we quantify the trade-off between the number of ToT bits and low-level tracking inputs. As both ATLAS and CMS are designing upgraded detectors, this work provides guidance for the pixel module designs to meet TIDE needs. Work funded by the China Scholarship Council and the Office of High Energy Physics of the U.S. Department of Energy under contract DE-AC02-05CH11231.

Effects of vegetation heterogeneity and surface topography on spatial scaling of net primary productivity

NASA Astrophysics Data System (ADS)

Chen, J. M.; Chen, X.; Ju, W.

2013-03-01

Due to the heterogeneous nature of the land surface, spatial scaling is an inevitable issue in the development of land models coupled with low-resolution Earth system models (ESMs) for predicting land-atmosphere interactions and carbon-climate feedbacks. In this study, a simple spatial scaling algorithm is developed to correct errors in net primary productivity (NPP) estimates made at a coarse spatial resolution based on sub-pixel information of vegetation heterogeneity and surface topography. An eco-hydrological model BEPS-TerrainLab, which considers both vegetation and topographical effects on the vertical and lateral water flows and the carbon cycle, is used to simulate NPP at 30 m and 1 km resolutions for a 5700 km2 watershed with an elevation range from 518 m to 3767 m in the Qinling Mountain, Shaanxi Province, China. Assuming that the NPP simulated at 30 m resolution represents the reality and that at 1 km resolution is subject to errors due to sub-pixel heterogeneity, a spatial scaling index (SSI) is developed to correct the coarse resolution NPP values pixel by pixel. The agreement between the NPP values at these two resolutions is improved considerably from R2 = 0.782 to R2 = 0.884 after the correction. The mean bias error (MBE) in NPP modeled at the 1 km resolution is reduced from 14.8 g C m-2 yr-1 to 4.8 g C m-2 yr-1 in comparison with NPP modeled at 30 m resolution, where the mean NPP is 668 g C m-2 yr-1. The range of spatial variations of NPP at 30 m resolution is larger than that at 1 km resolution. Land cover fraction is the most important vegetation factor to be considered in NPP spatial scaling, and slope is the most important topographical factor for NPP spatial scaling especially in mountainous areas, because of its influence on the lateral water redistribution, affecting water table, soil moisture and plant growth. Other factors including leaf area index (LAI), elevation and aspect have small and additive effects on improving the spatial scaling between these two resolutions.

Effects of vegetation heterogeneity and surface topography on spatial scaling of net primary productivity

NASA Astrophysics Data System (ADS)

Chen, J. M.; Chen, X.; Ju, W.

2013-07-01

Due to the heterogeneous nature of the land surface, spatial scaling is an inevitable issue in the development of land models coupled with low-resolution Earth system models (ESMs) for predicting land-atmosphere interactions and carbon-climate feedbacks. In this study, a simple spatial scaling algorithm is developed to correct errors in net primary productivity (NPP) estimates made at a coarse spatial resolution based on sub-pixel information of vegetation heterogeneity and surface topography. An eco-hydrological model BEPS-TerrainLab, which considers both vegetation and topographical effects on the vertical and lateral water flows and the carbon cycle, is used to simulate NPP at 30 m and 1 km resolutions for a 5700 km2 watershed with an elevation range from 518 m to 3767 m in the Qinling Mountain, Shanxi Province, China. Assuming that the NPP simulated at 30 m resolution represents the reality and that at 1 km resolution is subject to errors due to sub-pixel heterogeneity, a spatial scaling index (SSI) is developed to correct the coarse resolution NPP values pixel by pixel. The agreement between the NPP values at these two resolutions is improved considerably from R2 = 0.782 to R2 = 0.884 after the correction. The mean bias error (MBE) in NPP modelled at the 1 km resolution is reduced from 14.8 g C m-2 yr-1 to 4.8 g C m-2 yr-1 in comparison with NPP modelled at 30 m resolution, where the mean NPP is 668 g C m-2 yr-1. The range of spatial variations of NPP at 30 m resolution is larger than that at 1 km resolution. Land cover fraction is the most important vegetation factor to be considered in NPP spatial scaling, and slope is the most important topographical factor for NPP spatial scaling especially in mountainous areas, because of its influence on the lateral water redistribution, affecting water table, soil moisture and plant growth. Other factors including leaf area index (LAI) and elevation have small and additive effects on improving the spatial scaling between these two resolutions.

Large scale tracking algorithms

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hansen, Ross L.; Love, Joshua Alan; Melgaard, David Kennett

2015-01-01

Low signal-to-noise data processing algorithms for improved detection, tracking, discrimination and situational threat assessment are a key research challenge. As sensor technologies progress, the number of pixels will increase signi cantly. This will result in increased resolution, which could improve object discrimination, but unfortunately, will also result in a significant increase in the number of potential targets to track. Many tracking techniques, like multi-hypothesis trackers, suffer from a combinatorial explosion as the number of potential targets increase. As the resolution increases, the phenomenology applied towards detection algorithms also changes. For low resolution sensors, "blob" tracking is the norm. For highermore » resolution data, additional information may be employed in the detection and classfication steps. The most challenging scenarios are those where the targets cannot be fully resolved, yet must be tracked and distinguished for neighboring closely spaced objects. Tracking vehicles in an urban environment is an example of such a challenging scenario. This report evaluates several potential tracking algorithms for large-scale tracking in an urban environment.« less

ASIC Readout Circuit Architecture for Large Geiger Photodiode Arrays

NASA Technical Reports Server (NTRS)

Vasile, Stefan; Lipson, Jerold

2012-01-01

The objective of this work was to develop a new class of readout integrated circuit (ROIC) arrays to be operated with Geiger avalanche photodiode (GPD) arrays, by integrating multiple functions at the pixel level (smart-pixel or active pixel technology) in 250-nm CMOS (complementary metal oxide semiconductor) processes. In order to pack a maximum of functions within a minimum pixel size, the ROIC array is a full, custom application-specific integrated circuit (ASIC) design using a mixed-signal CMOS process with compact primitive layout cells. The ROIC array was processed to allow assembly in bump-bonding technology with photon-counting infrared detector arrays into 3-D imaging cameras (LADAR). The ROIC architecture was designed to work with either common- anode Si GPD arrays or common-cathode InGaAs GPD arrays. The current ROIC pixel design is hardwired prior to processing one of the two GPD array configurations, and it has the provision to allow soft reconfiguration to either array (to be implemented into the next ROIC array generation). The ROIC pixel architecture implements the Geiger avalanche quenching, bias, reset, and time to digital conversion (TDC) functions in full-digital design, and uses time domain over-sampling (vernier) to allow high temporal resolution at low clock rates, increased data yield, and improved utilization of the laser beam.

Advances in Small Pixel TES-Based X-Ray Microcalorimeter Arrays for Solar Physics and Astrophysics

NASA Technical Reports Server (NTRS)

Bandler, S. R.; Adams, J. S.; Bailey, C. N.; Busch, S. E.; Chervenak, J. A.; Eckart, M. E.; Ewin, A. E.; Finkbeiner, F. M.; Kelley, R. L.; Kelly, D. P.;

High resolution as a key feature to perform accurate ELISPOT measurements using Zeiss KS ELISPOT readers.

PubMed

Malkusch, Wolf

2005-01-01

The enzyme-linked immunospot (ELISPOT) assay was originally developed for the detection of individual antibody secreting B-cells. Since then, the method has been improved, and ELISPOT is used for the determination of the production of tumor necrosis factor (TNF)-alpha, interferon (IFN)-gamma, or various interleukins (IL)-4, IL-5. ELISPOT measurements are performed in 96-well plates with nitrocellulose membranes either visually or by means of image analysis. Image analysis offers various procedures to overcome variable background intensity problems and separate true from false spots. ELISPOT readers offer a complete solution for precise and automatic evaluation of ELISPOT assays. Number, size, and intensity of each single spot can be determined, printed, or saved for further statistical evaluation. Cytokine spots are always round, but because of floating edges with the background, they have a nonsmooth borderline. Resolution is a key feature for a precise detection of ELISPOT. In standard applications shape and edge steepness are essential parameters in addition to size and color for an accurate spot recognition. These parameters need a minimum spot diameter of 6 pixels. Collecting one single image per well with a standard color camera with 750 x 560 pixels will result in a resolution much too low to get all of the spots in a specimen. IFN-gamma spots may have only 25 microm diameters, and TNF-alpha spots just 15 microm. A 750 x 560 pixel image of a 6-mm well has a pixel size of 12 microm, resulting in only 1 or 2 pixel for a spot. Using a precise microscope optic in combination with a high resolution (1300 x 1030 pixel) integrating digital color camera, and at least 2 x 2 images per well will result in a pixel size of 2.5 microm and, as a minimum, 6 pixel diameter per spot. New approaches try to detect two cytokines per cell at the same time (i.e., IFN-gamma and IL-5). Standard staining procedures produce brownish spots (horseradish peroxidase) and blue spots (alkaline phosphatase). Problems may occur with color overlaps from cells producing both cytokines, resulting in violet spots. The latest experiments therefore try to use fluorescence labels as a marker. Fluorescein isothiocyanate results in green spots and Rhodamine in red spots. Cells producing both cytokines appear yellow. These colors can be separated much easier than the violet, red, and blue, especially using a high resolution.

IXO/XMS Detector Trade-Off Study

NASA Technical Reports Server (NTRS)

Kilbourne, Caroline Anne; deKorte, P.; Smith, S.; Hoevers, H.; vdKuur, J.; Ezoe, Y.; Ullom, J.

2010-01-01

This document presents the outcome of the detector trade-off for the XMS instrument on IXO. This trade-off is part of the Cryogenic instrument Phase-A study as proposed to ESA in the Declaration of Interest SRONXMS-PL-2009-003 dated June 6, 2009. The detector consists of two components: a core array for the highest spectral resolution and an outer array to increase the field of view substantially with modest increase in the number of read-out channels. Degraded resolution of the outer array in comparison with the core array is accepted in order to make this scheme possible. The two detector components may be a single unit or separate units. These arrays comprise pixels and the components that allow them to be arrayed. Each pixel comprises a thermometer, an absorber, and the thermal links between them and to the rest of the array. These links may be interfaces or distinct components. The array infrastructure comprises the mechanical structure of the array, the arrangement of the leads, and features added to improve the integrated thermal properties of the array in the focal-plane assembly.

Sub-pixel spatial resolution wavefront phase imaging

NASA Technical Reports Server (NTRS)

Stahl, H. Philip (Inventor); Mooney, James T. (Inventor)

2012-01-01

A phase imaging method for an optical wavefront acquires a plurality of phase images of the optical wavefront using a phase imager. Each phase image is unique and is shifted with respect to another of the phase images by a known/controlled amount that is less than the size of the phase imager's pixels. The phase images are then combined to generate a single high-spatial resolution phase image of the optical wavefront.

Geology of the Icy Galilean Satellites: Understanding Crustal Processes and Geologic Histories Through the JIMO Mission

NASA Technical Reports Server (NTRS)

Figueredo, P. H.; Tanaka, K.; Senske, D.; Greeley, R.

2003-01-01

Knowledge of the geology, style and time history of crustal processes on the icy Galilean satellites is necessary to understanding how these bodies formed and evolved. Data from the Galileo mission have provided a basis for detailed geologic and geo- physical analysis. Due to constrained downlink, Galileo Solid State Imaging (SSI) data consisted of global coverage at a -1 km/pixel ground sampling and representative, widely spaced regional maps at -200 m/pixel. These two data sets provide a general means to extrapolate units identified at higher resolution to lower resolution data. A sampling of key sites at much higher resolution (10s of m/pixel) allows evaluation of processes on local scales. We are currently producing the first global geological map of Europa using Galileo global and regional-scale data. This work is demonstrating the necessity and utility of planet-wide contiguous image coverage at global, regional, and local scales.

A 780 × 800 μm2 Multichannel Digital Silicon Photomultiplier With Column-Parallel Time-to-Digital Converter and Basic Characterization

NASA Astrophysics Data System (ADS)

Mandai, Shingo; Jain, Vishwas; Charbon, Edoardo

2014-02-01

This paper presents a digital silicon photomultiplier (SiPM) partitioned in columns, whereas each column is connected to a column-parallel time-to-digital converter (TDC), in order to improve the timing resolution of single-photon detection. By reducing the number of pixels per TDC using a sharing scheme with three TDCs per column, the pixel-to-pixel skew is reduced. We report the basic characterization of the SiPM, comprising 416 single-photon avalanche diodes (SPADs); the characterization includes photon detection probability, dark count rate, afterpulsing, and crosstalk. We achieved 264-ps full-width at half maximum timing resolution of single-photon detection using a 48-fold column-parallel TDC with a temporal resolution of 51.8 ps (least significant bit), fully integrated in standard complementary metal-oxide semiconductor technology.

Performance improvements of wavelength-shifting-fiber neutron detectors using high-resolution positioning algorithms

DOE PAGES

Wang, C. L.

2016-05-17

On the basis of FluoroBancroft linear-algebraic method [S.B. Andersson, Opt. Exp. 16, 18714 (2008)] three highly-resolved positioning methods were proposed for wavelength-shifting fiber (WLSF) neutron detectors. Using a Gaussian or exponential-decay light-response function (LRF), the non-linear relation of photon-number profiles vs. x-pixels was linearized and neutron positions were determined. The proposed algorithms give an average 0.03-0.08 pixel position error, much smaller than that (0.29 pixel) from a traditional maximum photon algorithm (MPA). The new algorithms result in better detector uniformity, less position misassignment (ghosting), better spatial resolution, and an equivalent or better instrument resolution in powder diffraction than the MPA.more » Moreover, these characters will facilitate broader applications of WLSF detectors at time-of-flight neutron powder diffraction beamlines, including single-crystal diffraction and texture analysis.« less

Charge Resolution of the Silicon Matrix of the ATIC Experiment

NASA Technical Reports Server (NTRS)

Zatsepin, V. I.; Adams, J. H., Jr.; Ahn, H. S.; Bashindzhagyan, G. L.; Batkov, K. E.; Case, G.; Christl, M.; Ganel, O.; Fazely, A. R.; Ganel, O.;

Comparison of Huanjing and Landsat satellite remote sensing of the spatial heterogeneity of Qinghai-Tibet alpine grassland

NASA Astrophysics Data System (ADS)

Wang, Junbang; Sun, Wenyi

2014-11-01

Remote sensing is widely applied in the study of terrestrial primary production and the global carbon cycle. The researches on the spatial heterogeneity in images with different sensors and resolutions would improve the application of remote sensing. In this study two sites on alpine meadow grassland in Qinghai, China, which have distinct fractal vegetation cover, were used to test and analyze differences between Normalized Difference Vegetation Index (NDVI) and enhanced vegetation index (EVI) derived from the Huanjing (HJ) and Landsat Thematic Mapper (TM) sensors. The results showed that: 1) NDVI estimated from HJ were smaller than the corresponding values from TM at the two sites whereas EVI were almost the same for the two sensors. 2) The overall variance represented by HJ data was consistently about half of that of Landsat TM although their nominal pixel size is approximately 30m for both sensors. The overall variance from EVI is greater than that from NDVI. The difference of the range between the two sensors is about 6 pixels at 30m resolution. The difference of the range in which there is not more corrective between two vegetation indices is about 1 pixel. 3) The sill decreased when pixel size increased from 30m to 1km, and then decreased very quickly when pixel size is changed to 250m from 30m or 90m but slowly when changed from 250m to 500m. HJ can capture this spatial heterogeneity to some extent and this study provides foundations for the use of the sensor for validation of net primary productivity estimates obtained from ecosystem process models.

Automatic determination of the artery vein ratio in retinal images

NASA Astrophysics Data System (ADS)

Niemeijer, Meindert; van Ginneken, Bram; Abràmoff, Michael D.

2010-03-01

A lower ratio between the width of the arteries and veins (Arteriolar-to-Venular diameter Ratio, AVR) on the retina, is well established to be predictive of stroke and other cardiovascular events in adults, as well as an increased risk of retinopathy of prematurity in premature infants. This work presents an automatic method that detects the location of the optic disc, determines the appropriate region of interest (ROI), classifies the vessels in the ROI into arteries and veins, measures their widths and calculates the AVR. After vessel segmentation and vessel width determination the optic disc is located and the system eliminates all vessels outside the AVR measurement ROI. The remaining vessels are thinned, vessel crossing and bifurcation points are removed leaving a set of vessel segments containing centerline pixels. Features are extracted from each centerline pixel that are used to assign them a soft label indicating the likelihood the pixel is part of a vein. As all centerline pixels in a connected segment should be the same type, the median soft label is assigned to each centerline pixel in the segment. Next artery vein pairs are matched using an iterative algorithm and the widths of the vessels is used to calculate the AVR. We train and test the algorithm using a set of 25 high resolution digital color fundus photographs a reference standard that indicates for the major vessels in the images whether they are an artery or a vein. We compared the AVR values produced by our system with those determined using a computer assisted method in 15 high resolution digital color fundus photographs and obtained a correlation coefficient of 0.881.

Three-Dimensional Super-Resolution: Theory, Modeling, and Field Tests Results

NASA Technical Reports Server (NTRS)

Bulyshev, Alexander; Amzajerdian, Farzin; Roback, Vincent E.; Hines, Glenn; Pierrottet, Diego; Reisse, Robert

2014-01-01

Many flash lidar applications continue to demand higher three-dimensional image resolution beyond the current state-of-the-art technology of the detector arrays and their associated readout circuits. Even with the available number of focal plane pixels, the required number of photons for illuminating all the pixels may impose impractical requirements on the laser pulse energy or the receiver aperture size. Therefore, image resolution enhancement by means of a super-resolution algorithm in near real time presents a very attractive solution for a wide range of flash lidar applications. This paper describes a superresolution technique and illustrates its performance and merits for generating three-dimensional image frames at a video rate.

Portable and cost-effective pixel super-resolution on-chip microscope for telemedicine applications.

PubMed

Bishara, Waheb; Sikora, Uzair; Mudanyali, Onur; Su, Ting-Wei; Yaglidere, Oguzhan; Luckhart, Shirley; Ozcan, Aydogan

2011-01-01

We report a field-portable lensless on-chip microscope with a lateral resolution of <1 μm and a large field-of-view of ~24 mm(2). This microscope is based on digital in-line holography and a pixel super-resolution algorithm to process multiple lensfree holograms and obtain a single high-resolution hologram. In its compact and cost-effective design, we utilize 23 light emitting diodes butt-coupled to 23 multi-mode optical fibers, and a simple optical filter, with no moving parts. Weighing only ~95 grams, we demonstrate the performance of this field-portable microscope by imaging various objects including human malaria parasites in thin blood smears.

47 CFR 73.9003 - Compliance requirements for covered demodulator products: Unscreened content.

Code of Federal Regulations, 2010 CFR

2010-10-01

... operating in a mode compatible with the digital visual interface (DVI) rev. 1.0 Specification as an image having the visual equivalent of no more than 350,000 pixels per frame (e.g. an image with resolution of 720×480 pixels for a 4:3 (nonsquare pixel) aspect ratio), and 30 frames per second. Such an image may...

47 CFR 73.9004 - Compliance requirements for covered demodulator products: Marked content.

Code of Federal Regulations, 2010 CFR

2010-10-01

... compatible with the digital visual interface (DVI) Rev. 1.0 Specification as an image having the visual equivalent of no more than 350,000 pixels per frame (e.g., an image with resolution of 720×480 pixels for a 4:3 (nonsquare pixel) aspect ratio), and 30 frames per second. Such an image may be attained by...

High-Resolution Remote Sensing Image Building Extraction Based on Markov Model

NASA Astrophysics Data System (ADS)

Zhao, W.; Yan, L.; Chang, Y.; Gong, L.

2018-04-01

With the increase of resolution, remote sensing images have the characteristics of increased information load, increased noise, more complex feature geometry and texture information, which makes the extraction of building information more difficult. To solve this problem, this paper designs a high resolution remote sensing image building extraction method based on Markov model. This method introduces Contourlet domain map clustering and Markov model, captures and enhances the contour and texture information of high-resolution remote sensing image features in multiple directions, and further designs the spectral feature index that can characterize "pseudo-buildings" in the building area. Through the multi-scale segmentation and extraction of image features, the fine extraction from the building area to the building is realized. Experiments show that this method can restrain the noise of high-resolution remote sensing images, reduce the interference of non-target ground texture information, and remove the shadow, vegetation and other pseudo-building information, compared with the traditional pixel-level image information extraction, better performance in building extraction precision, accuracy and completeness.

Implementation of Complex Signal Processing Algorithms for Position-Sensitive Microcalorimeters

NASA Technical Reports Server (NTRS)

Smith, Stephen J.

2008-01-01

We have recently reported on a theoretical digital signal-processing algorithm for improved energy and position resolution in position-sensitive, transition-edge sensor (POST) X-ray detectors [Smith et al., Nucl, lnstr and Meth. A 556 (2006) 2371. PoST's consists of one or more transition-edge sensors (TES's) on a large continuous or pixellated X-ray absorber and are under development as an alternative to arrays of single pixel TES's. PoST's provide a means to increase the field-of-view for the fewest number of read-out channels. In this contribution we extend the theoretical correlated energy position optimal filter (CEPOF) algorithm (originally developed for 2-TES continuous absorber PoST's) to investigate the practical implementation on multi-pixel single TES PoST's or Hydras. We use numerically simulated data for a nine absorber device, which includes realistic detector noise, to demonstrate an iterative scheme that enables convergence on the correct photon absorption position and energy without any a priori assumptions. The position sensitivity of the CEPOF implemented on simulated data agrees very well with the theoretically predicted resolution. We discuss practical issues such as the impact of random arrival phase of the measured data on the performance of the CEPOF. The CEPOF algorithm demonstrates that full-width-at- half-maximum energy resolution of < 8 eV coupled with position-sensitivity down to a few 100 eV should be achievable for a fully optimized device.

Adaptive single-pixel imaging with aggregated sampling and continuous differential measurements

NASA Astrophysics Data System (ADS)

Huo, Yaoran; He, Hongjie; Chen, Fan; Tai, Heng-Ming

2018-06-01

This paper proposes an adaptive compressive imaging technique with one single-pixel detector and single arm. The aggregated sampling (AS) method enables the reduction of resolutions of the reconstructed images. It aims to reduce the time and space consumption. The target image with a resolution up to 1024 × 1024 can be reconstructed successfully at the 20% sampling rate. The continuous differential measurement (CDM) method combined with a ratio factor of significant coefficient (RFSC) improves the imaging quality. Moreover, RFSC reduces the human intervention in parameter setting. This technique enhances the practicability of single-pixel imaging with the benefits from less time and space consumption, better imaging quality and less human intervention.

Investigating the effect of pixel size of high spatial resolution FTIR imaging for detection of colorectal cancer

NASA Astrophysics Data System (ADS)

Lloyd, G. R.; Nallala, J.; Stone, N.

2016-03-01

FTIR is a well-established technique and there is significant interest in applying this technique to medical diagnostics e.g. to detect cancer. The introduction of focal plane array (FPA) detectors means that FTIR is particularly suited to rapid imaging of biopsy sections as an adjunct to digital pathology. Until recently however each pixel in the image has been limited to a minimum of 5.5 µm which results in a comparatively low magnification image or histology applications and potentially the loss of important diagnostic information. The recent introduction of higher magnification optics gives image pixels that cover approx. 1.1 µm. This reduction in image pixel size gives images of higher magnification and improved spatial detail can be observed. However, the effect of increasing the magnification on spectral quality and the ability to discriminate between disease states is not well studied. In this work we test the discriminatory performance of FTIR imaging using both standard (5.5 µm) and high (1.1 µm) magnification for the detection of colorectal cancer and explore the effect of binning to degrade high resolution images to determine whether similar diagnostic information and performance can be obtained using both magnifications. Results indicate that diagnostic performance using high magnification may be reduced as compared to standard magnification when using existing multivariate approaches. Reduction of the high magnification data to standard magnification via binning can potentially recover some of the lost performance.

Aircraft target detection algorithm based on high resolution spaceborne SAR imagery

NASA Astrophysics Data System (ADS)

Zhang, Hui; Hao, Mengxi; Zhang, Cong; Su, Xiaojing

2018-03-01

In this paper, an image classification algorithm for airport area is proposed, which based on the statistical features of synthetic aperture radar (SAR) images and the spatial information of pixels. The algorithm combines Gamma mixture model and MRF. The algorithm using Gamma mixture model to obtain the initial classification result. Pixel space correlation based on the classification results are optimized by the MRF technique. Additionally, morphology methods are employed to extract airport (ROI) region where the suspected aircraft target samples are clarified to reduce the false alarm and increase the detection performance. Finally, this paper presents the plane target detection, which have been verified by simulation test.

Fabrication of X-ray Microcalorimeter Focal Planes Composed of Two Distinct Pixel Types.

PubMed

Wassell, E J; Adams, J S; Bandler, S R; Betancourt-Martinez, G L; Chiao, M P; Chang, M P; Chervenak, J A; Datesman, A M; Eckart, M E; Ewin, A J; Finkbeiner, F M; Ha, J Y; Kelley, R; Kilbourne, C A; Miniussi, A R; Sakai, K; Porter, F; Sadleir, J E; Smith, S J; Wakeham, N A; Yoon, W

2017-06-01

We are developing superconducting transition-edge sensor (TES) microcalorimeter focal planes for versatility in meeting specifications of X-ray imaging spectrometers including high count-rate, high energy resolution, and large field-of-view. In particular, a focal plane composed of two sub-arrays: one of fine-pitch, high count-rate devices and the other of slower, larger pixels with similar energy resolution, offers promise for the next generation of astrophysics instruments, such as the X-ray Integral Field Unit (X-IFU) instrument on the European Space Agency's Athena mission. We have based the sub-arrays of our current design on successful pixel designs that have been demonstrated separately. Pixels with an all gold X-ray absorber on 50 and 75 micron scales where the Mo/Au TES sits atop a thick metal heatsinking layer have shown high resolution and can accommodate high count-rates. The demonstrated larger pixels use a silicon nitride membrane for thermal isolation, thinner Au and an added bismuth layer in a 250 micron square absorber. To tune the parameters of each sub-array requires merging the fabrication processes of the two detector types. We present the fabrication process for dual production of different X-ray absorbers on the same substrate, thick Au on the small pixels and thinner Au with a Bi capping layer on the larger pixels to tune their heat capacities. The process requires multiple electroplating and etching steps, but the absorbers are defined in a single ion milling step. We demonstrate methods for integrating heatsinking of the two types of pixel into the same focal plane consistent with the requirements for each sub-array, including the limiting of thermal crosstalk. We also discuss fabrication process modifications for tuning the intrinsic transition temperature (T c ) of the bilayers for the different device types through variation of the bilayer thicknesses. The latest results on these "hybrid" arrays will be presented.

Fabrication of X-ray Microcalorimeter Focal Planes Composed of Two Distinct Pixel Types

PubMed Central

Wassell, E. J.; Adams, J. S.; Bandler, S. R.; Betancourt-Martinez, G. L.; Chiao, M. P.; Chang, M. P.; Chervenak, J. A.; Datesman, A. M.; Eckart, M. E.; Ewin, A. J.; Finkbeiner, F. M.; Ha, J. Y.; Kelley, R.; Kilbourne, C. A.; Miniussi, A. R.; Sakai, K.; Porter, F.; Sadleir, J. E.; Smith, S. J.; Wakeham, N. A.; Yoon, W.

2017-01-01

We are developing superconducting transition-edge sensor (TES) microcalorimeter focal planes for versatility in meeting specifications of X-ray imaging spectrometers including high count-rate, high energy resolution, and large field-of-view. In particular, a focal plane composed of two sub-arrays: one of fine-pitch, high count-rate devices and the other of slower, larger pixels with similar energy resolution, offers promise for the next generation of astrophysics instruments, such as the X-ray Integral Field Unit (X-IFU) instrument on the European Space Agency’s Athena mission. We have based the sub-arrays of our current design on successful pixel designs that have been demonstrated separately. Pixels with an all gold X-ray absorber on 50 and 75 micron scales where the Mo/Au TES sits atop a thick metal heatsinking layer have shown high resolution and can accommodate high count-rates. The demonstrated larger pixels use a silicon nitride membrane for thermal isolation, thinner Au and an added bismuth layer in a 250 micron square absorber. To tune the parameters of each sub-array requires merging the fabrication processes of the two detector types. We present the fabrication process for dual production of different X-ray absorbers on the same substrate, thick Au on the small pixels and thinner Au with a Bi capping layer on the larger pixels to tune their heat capacities. The process requires multiple electroplating and etching steps, but the absorbers are defined in a single ion milling step. We demonstrate methods for integrating heatsinking of the two types of pixel into the same focal plane consistent with the requirements for each sub-array, including the limiting of thermal crosstalk. We also discuss fabrication process modifications for tuning the intrinsic transition temperature (Tc) of the bilayers for the different device types through variation of the bilayer thicknesses. The latest results on these “hybrid” arrays will be presented. PMID:28804229

Fabrication of X-ray Microcalorimeter Focal Planes Composed of Two Distinct Pixel Types

NASA Technical Reports Server (NTRS)

Wassell, Edward J.; Adams, Joseph S.; Bandler, Simon R.; Betancour-Martinez, Gabriele L; Chiao, Meng P.; Chang, Meng Ping; Chervenak, James A.; Datesman, Aaron M.; Eckart, Megan E.; Ewin, Audrey J.;

Design and characterization of an ultraresolution seamlessly tiled display for data visualization

NASA Astrophysics Data System (ADS)

Bordes, Nicole; Bleha, William P.; Pailthorpe, Bernard

2003-09-01

The demand for more pixels in digital displays is beginning to be met as manufacturers increase the native resolution of projector chips. Tiling several projectors still offers one solution to augment the pixel capacity of a display. However problems of color and illumination uniformity across projectors need to be addressed as well as the computer software required to drive such devices. In this paper we present the results obtained on a desktop size tiled projector array of three D-ILA projectors sharing a common illumination source. The composite image on a 3 x 1 array, is 3840 by 1024 pixels with a resolution of about 80 dpi. The system preserves desktop resolution, is compact and can fit in a normal room or laboratory. A fiber optic beam splitting system and a single set of red, green and blue dichroic filters are the key to color and illumination uniformity. The D-ILA chips inside each projector can be adjusted individually to set or change characteristics such as contrast, brightness or gamma curves. The projectors were matched carefully and photometric variations were corrected, leading to a seamless tiled image. Photometric measurements were performed to characterize the display and losses through the optical paths, and are reported here. This system is driven by a small PC computer cluster fitted with graphics cards and is running Linux. The Chromium API can be used for tiling graphics tiles across the display and interfacing to users' software applications. There is potential for scaling the design to accommodate larger arrays, up to 4x5 projectors, increasing display system capacity to 50 Megapixels. Further increases, beyond 100 Megapixels can be anticipated with new generation D-ILA chips capable of projecting QXGA (2k x 1.5k), with ongoing evolution as QUXGA (4k x 2k) becomes available.

Depth-of-Interaction Compensation Using a Focused-Cut Scintillator for a Pinhole Gamma Camera.

PubMed

Alhassen, Fares; Kudrolli, Haris; Singh, Bipin; Kim, Sangtaek; Seo, Youngho; Gould, Robert G; Nagarkar, Vivek V

2011-06-01

Preclinical SPECT offers a powerful means to understand the molecular pathways of drug interactions in animal models by discovering and testing new pharmaceuticals and therapies for potential clinical applications. A combination of high spatial resolution and sensitivity are required in order to map radiotracer uptake within small animals. Pinhole collimators have been investigated, as they offer high resolution by means of image magnification. One of the limitations of pinhole geometries is that increased magnification causes some rays to travel through the detection scintillator at steep angles, introducing parallax errors due to variable depth-of-interaction in scintillator material, especially towards the edges of the detector field of view. These parallax errors ultimately limit the resolution of pinhole preclinical SPECT systems, especially for higher energy isotopes that can easily penetrate through millimeters of scintillator material. A pixellated, focused-cut (FC) scintillator, with its pixels laser-cut so that they are collinear with incoming rays, can potentially compensate for these parallax errors and thus improve the system resolution. We performed the first experimental evaluation of a newly developed focused-cut scintillator. We scanned a Tc-99m source across the field of view of pinhole gamma camera with a continuous scintillator, a conventional "straight-cut" (SC) pixellated scintillator, and a focused-cut scintillator, each coupled to an electron-multiplying charge coupled device (EMCCD) detector by a fiber-optic taper, and compared the measured full-width half-maximum (FWHM) values. We show that the FWHMs of the focused-cut scintillator projections are comparable to the FWHMs of the thinner SC scintillator, indicating the effectiveness of the focused-cut scintillator in compensating parallax errors.

Depth-of-Interaction Compensation Using a Focused-Cut Scintillator for a Pinhole Gamma Camera

PubMed Central

Alhassen, Fares; Kudrolli, Haris; Singh, Bipin; Kim, Sangtaek; Seo, Youngho; Gould, Robert G.; Nagarkar, Vivek V.

2011-01-01

Preclinical SPECT offers a powerful means to understand the molecular pathways of drug interactions in animal models by discovering and testing new pharmaceuticals and therapies for potential clinical applications. A combination of high spatial resolution and sensitivity are required in order to map radiotracer uptake within small animals. Pinhole collimators have been investigated, as they offer high resolution by means of image magnification. One of the limitations of pinhole geometries is that increased magnification causes some rays to travel through the detection scintillator at steep angles, introducing parallax errors due to variable depth-of-interaction in scintillator material, especially towards the edges of the detector field of view. These parallax errors ultimately limit the resolution of pinhole preclinical SPECT systems, especially for higher energy isotopes that can easily penetrate through millimeters of scintillator material. A pixellated, focused-cut (FC) scintillator, with its pixels laser-cut so that they are collinear with incoming rays, can potentially compensate for these parallax errors and thus improve the system resolution. We performed the first experimental evaluation of a newly developed focused-cut scintillator. We scanned a Tc-99m source across the field of view of pinhole gamma camera with a continuous scintillator, a conventional “straight-cut” (SC) pixellated scintillator, and a focused-cut scintillator, each coupled to an electron-multiplying charge coupled device (EMCCD) detector by a fiber-optic taper, and compared the measured full-width half-maximum (FWHM) values. We show that the FWHMs of the focused-cut scintillator projections are comparable to the FWHMs of the thinner SC scintillator, indicating the effectiveness of the focused-cut scintillator in compensating parallax errors. PMID:21731108

Depth-of-Interaction Compensation Using a Focused-Cut Scintillator for a Pinhole Gamma Camera

NASA Astrophysics Data System (ADS)

Alhassen, Fares; Kudrolli, Haris; Singh, Bipin; Kim, Sangtaek; Seo, Youngho; Gould, Robert G.; Nagarkar, Vivek V.

2011-06-01

Preclinical SPECT offers a powerful means to understand the molecular pathways of drug interactions in animal models by discovering and testing new pharmaceuticals and therapies for potential clinical applications. A combination of high spatial resolution and sensitivity are required in order to map radiotracer uptake within small animals. Pinhole collimators have been investigated, as they offer high resolution by means of image magnification. One of the limitations of pinhole geometries is that increased magnification causes some rays to travel through the detection scintillator at steep angles, introducing parallax errors due to variable depth-of-interaction in scintillator material, especially towards the edges of the detector field of view. These parallax errors ultimately limit the resolution of pinhole preclinical SPECT systems, especially for higher energy isotopes that can easily penetrate through millimeters of scintillator material. A pixellated, focused-cut (FC) scintillator, with its pixels laser-cut so that they are collinear with incoming rays, can potentially compensate for these parallax errors and thus improve the system resolution. We performed the first experimental evaluation of a newly developed focused-cut scintillator. We scanned a Tc-99 m source across the field of view of pinhole gamma camera with a continuous scintillator, a conventional “straight-cut” (SC) pixellated scintillator, and a focused-cut scintillator, each coupled to an electron-multiplying charge coupled device (EMCCD) detector by a fiber-optic taper, and compared the measured full-width half-maximum (FWHM) values. We show that the FWHMs of the focused-cut scintillator projections are comparable to the FWHMs of the thinner SC scintillator, indicating the effectiveness of the focused-cut scintillator in compensating parallax errors.

Event Centroiding Applied to Energy-Resolved Neutron Imaging at LANSCE

DOE PAGES

Borges, Nicholas; Losko, Adrian; Vogel, Sven

2018-02-13

The energy-dependence of the neutron cross section provides vastly different contrast mechanisms than polychromatic neutron radiography if neutron energies can be selected for imaging applications. In recent years, energy-resolved neutron imaging (ERNI) with epi-thermal neutrons, utilizing neutron absorption resonances for contrast as well as for quantitative density measurements, was pioneered at the Flight Path 5 beam line at LANSCE and continues to be refined. In this work, we present event centroiding, i.e., the determination of the center-of-gravity of a detection event on an imaging detector to allow sub-pixel spatial resolution and apply it to the many frames collected for energy-resolvedmore » neutron imaging at a pulsed neutron source. While event centroiding was demonstrated at thermal neutron sources, it has not been applied to energy-resolved neutron imaging, where the energy resolution requires to be preserved, and we present a quantification of the possible resolution as a function of neutron energy. For the 55 μm pixel size of the detector used for this study, we found a resolution improvement from ~80 μm to ~22 μm using pixel centroiding while fully preserving the energy resolution.« less

Event Centroiding Applied to Energy-Resolved Neutron Imaging at LANSCE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Borges, Nicholas; Losko, Adrian; Vogel, Sven

The energy-dependence of the neutron cross section provides vastly different contrast mechanisms than polychromatic neutron radiography if neutron energies can be selected for imaging applications. In recent years, energy-resolved neutron imaging (ERNI) with epi-thermal neutrons, utilizing neutron absorption resonances for contrast as well as for quantitative density measurements, was pioneered at the Flight Path 5 beam line at LANSCE and continues to be refined. In this work, we present event centroiding, i.e., the determination of the center-of-gravity of a detection event on an imaging detector to allow sub-pixel spatial resolution and apply it to the many frames collected for energy-resolvedmore » neutron imaging at a pulsed neutron source. While event centroiding was demonstrated at thermal neutron sources, it has not been applied to energy-resolved neutron imaging, where the energy resolution requires to be preserved, and we present a quantification of the possible resolution as a function of neutron energy. For the 55 μm pixel size of the detector used for this study, we found a resolution improvement from ~80 μm to ~22 μm using pixel centroiding while fully preserving the energy resolution.« less

Micrometer-resolution imaging using MÖNCH: towards G2-less grating interferometry

PubMed Central

Cartier, Sebastian; Kagias, Matias; Bergamaschi, Anna; Wang, Zhentian; Dinapoli, Roberto; Mozzanica, Aldo; Ramilli, Marco; Schmitt, Bernd; Brückner, Martin; Fröjdh, Erik; Greiffenberg, Dominic; Mayilyan, Davit; Mezza, Davide; Redford, Sophie; Ruder, Christian; Schädler, Lukas; Shi, Xintian; Thattil, Dhanya; Tinti, Gemma; Zhang, Jiaguo; Stampanoni, Marco

2016-01-01

MÖNCH is a 25 µm-pitch charge-integrating detector aimed at exploring the limits of current hybrid silicon detector technology. The small pixel size makes it ideal for high-resolution imaging. With an electronic noise of about 110 eV r.m.s., it opens new perspectives for many synchrotron applications where currently the detector is the limiting factor, e.g. inelastic X-ray scattering, Laue diffraction and soft X-ray or high-resolution color imaging. Due to the small pixel pitch, the charge cloud generated by absorbed X-rays is shared between neighboring pixels for most of the photons. Therefore, at low photon fluxes, interpolation algorithms can be applied to determine the absorption position of each photon with a resolution of the order of 1 µm. In this work, the characterization results of one of the MÖNCH prototypes are presented under low-flux conditions. A custom interpolation algorithm is described and applied to the data to obtain high-resolution images. Images obtained in grating interferometry experiments without the use of the absorption grating G2 are shown and discussed. Perspectives for the future developments of the MÖNCH detector are also presented. PMID:27787252

[The optimizing design and experiment for a MOEMS micro-mirror spectrometer].

PubMed

Mo, Xiang-xia; Wen, Zhi-yu; Zhang, Zhi-hai; Guo, Yuan-jun

2011-12-01

A MOEMS micro-mirror spectrometer, which uses micro-mirror as a light switch so that spectrum can be detected by a single detector, has the advantages of transforming DC into AC, applying Hadamard transform optics without additional template, high pixel resolution and low cost. In this spectrometer, the vital problem is the conflict between the scales of slit and the light intensity. Hence, in order to improve the resolution of this spectrometer, the present paper gives the analysis of the new effects caused by micro structure, and optimal values of the key factors. Firstly, the effects of diffraction limitation, spatial sample rate and curved slit image on the resolution of the spectrum were proposed. Then, the results were simulated; the key values were tested on the micro mirror spectrometer. Finally, taking all these three effects into account, this micro system was optimized. With a scale of 70 mm x 130 mm, decreasing the height of the image at the plane of micro mirror can not diminish the influence of curved slit image in the spectrum; under the demand of spatial sample rate, the resolution must be twice over the pixel resolution; only if the width of the slit is 1.818 microm and the pixel resolution is 2.2786 microm can the spectrometer have the best performance.

Detector Sampling of Optical/IR Spectra: How Many Pixels per FWHM?

NASA Astrophysics Data System (ADS)

Robertson, J. Gordon

2017-08-01

Most optical and IR spectra are now acquired using detectors with finite-width pixels in a square array. Each pixel records the received intensity integrated over its own area, and pixels are separated by the array pitch. This paper examines the effects of such pixellation, using computed simulations to illustrate the effects which most concern the astronomer end-user. It is shown that coarse sampling increases the random noise errors in wavelength by typically 10-20 % at 2 pixels per Full Width at Half Maximum, but with wide variation depending on the functional form of the instrumental Line Spread Function (i.e. the instrumental response to a monochromatic input) and on the pixel phase. If line widths are determined, they are even more strongly affected at low sampling frequencies. However, the noise in fitted peak amplitudes is minimally affected by pixellation, with increases less than about 5%. Pixellation has a substantial but complex effect on the ability to see a relative minimum between two closely spaced peaks (or relative maximum between two absorption lines). The consistent scale of resolving power presented by Robertson to overcome the inadequacy of the Full Width at Half Maximum as a resolution measure is here extended to cover pixellated spectra. The systematic bias errors in wavelength introduced by pixellation, independent of signal/noise ratio, are examined. While they may be negligible for smooth well-sampled symmetric Line Spread Functions, they are very sensitive to asymmetry and high spatial frequency sub-structure. The Modulation Transfer Function for sampled data is shown to give a useful indication of the extent of improperly sampled signal in an Line Spread Function. The common maxim that 2 pixels per Full Width at Half Maximum is the Nyquist limit is incorrect and most Line Spread Functions will exhibit some aliasing at this sample frequency. While 2 pixels per Full Width at Half Maximum is nevertheless often an acceptable minimum for moderate signal/noise work, it is preferable to carry out simulations for any actual or proposed Line Spread Function to find the effects of various sampling frequencies. Where spectrograph end-users have a choice of sampling frequencies, through on-chip binning and/or spectrograph configurations, it is desirable that the instrument user manual should include an examination of the effects of the various choices.

Optimization of an on-board imaging system for extremely rapid radiation therapy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cherry Kemmerling, Erica M.; Wu, Meng, E-mail: mengwu@stanford.edu; Yang, He

2015-11-15

Purpose: Next-generation extremely rapid radiation therapy systems could mitigate the need for motion management, improve patient comfort during the treatment, and increase patient throughput for cost effectiveness. Such systems require an on-board imaging system that is competitively priced, fast, and of sufficiently high quality to allow good registration between the image taken on the day of treatment and the image taken the day of treatment planning. In this study, three different detectors for a custom on-board CT system were investigated to select the best design for integration with an extremely rapid radiation therapy system. Methods: Three different CT detectors aremore » proposed: low-resolution (all 4 × 4 mm pixels), medium-resolution (a combination of 4 × 4 mm pixels and 2 × 2 mm pixels), and high-resolution (all 1 × 1 mm pixels). An in-house program was used to generate projection images of a numerical anthropomorphic phantom and to reconstruct the projections into CT datasets, henceforth called “realistic” images. Scatter was calculated using a separate Monte Carlo simulation, and the model included an antiscatter grid and bowtie filter. Diagnostic-quality images of the phantom were generated to represent the patient scan at the time of treatment planning. Commercial deformable registration software was used to register the diagnostic-quality scan to images produced by the various on-board detector configurations. The deformation fields were compared against a “gold standard” deformation field generated by registering initial and deformed images of the numerical phantoms that were used to make the diagnostic and treatment-day images. Registrations of on-board imaging system data were judged by the amount their deformation fields differed from the corresponding gold standard deformation fields—the smaller the difference, the better the system. To evaluate the registrations, the pointwise distance between gold standard and realistic registration deformation fields was computed. Results: By most global metrics (e.g., mean, median, and maximum pointwise distance), the high-resolution detector had the best performance but the medium-resolution detector was comparable. For all medium- and high-resolution detector registrations, mean error between the realistic and gold standard deformation fields was less than 4 mm. By pointwise metrics (e.g., tracking a small lesion), the high- and medium-resolution detectors performed similarly. For these detectors, the smallest error between the realistic and gold standard registrations was 0.6 mm and the largest error was 3.6 mm. Conclusions: The medium-resolution CT detector was selected as the best for an extremely rapid radiation therapy system. In essentially all test cases, data from this detector produced a significantly better registration than data from the low-resolution detector and a comparable registration to data from the high-resolution detector. The medium-resolution detector provides an appropriate compromise between registration accuracy and system cost.« less

Comparing the imaging performance of computed super resolution and magnification tomosynthesis

NASA Astrophysics Data System (ADS)

Maidment, Tristan D.; Vent, Trevor L.; Ferris, William S.; Wurtele, David E.; Acciavatti, Raymond J.; Maidment, Andrew D. A.

2017-03-01

Computed super-resolution (SR) is a method of reconstructing images with pixels that are smaller than the detector element size; superior spatial resolution is achieved through the elimination of aliasing and alteration of the sampling function imposed by the reconstructed pixel aperture. By comparison, magnification mammography is a method of projection imaging that uses geometric magnification to increase spatial resolution. This study explores the development and application of magnification digital breast tomosynthesis (MDBT). Four different acquisition geometries are compared in terms of various image metrics. High-contrast spatial resolution was measured in various axes using a lead star pattern. A modified Defrise phantom was used to determine the low-frequency spatial resolution. An anthropomorphic phantom was used to simulate clinical imaging. Each experiment was conducted at three different magnifications: contact (1.04x), MAG1 (1.3x), and MAG2 (1.6x). All images were taken on our next generation tomosynthesis system, an in-house solution designed to optimize SR. It is demonstrated that both computed SR and MDBT (MAG1 and MAG2) provide improved spatial resolution over non-SR contact imaging. To achieve the highest resolution, SR and MDBT should be combined. However, MDBT is adversely affected by patient motion at higher magnifications. In addition, MDBT requires more radiation dose and delays diagnosis, since MDBT would be conducted upon recall. By comparison, SR can be conducted with the original screening data. In conclusion, this study demonstrates that computed SR and MDBT are both viable methods of imaging the breast.

Single image super-resolution via regularized extreme learning regression for imagery from microgrid polarimeters

NASA Astrophysics Data System (ADS)

Sargent, Garrett C.; Ratliff, Bradley M.; Asari, Vijayan K.

2017-08-01

The advantage of division of focal plane imaging polarimeters is their ability to obtain temporally synchronized intensity measurements across a scene; however, they sacrifice spatial resolution in doing so due to their spatially modulated arrangement of the pixel-to-pixel polarizers and often result in aliased imagery. Here, we propose a super-resolution method based upon two previously trained extreme learning machines (ELM) that attempt to recover missing high frequency and low frequency content beyond the spatial resolution of the sensor. This method yields a computationally fast and simple way of recovering lost high and low frequency content from demosaicing raw microgrid polarimetric imagery. The proposed method outperforms other state-of-the-art single-image super-resolution algorithms in terms of structural similarity and peak signal-to-noise ratio.

MRO's High Resolution Imaging Science Experiment (HiRISE): Polar Science Expectations

NASA Technical Reports Server (NTRS)

McEwen, A.; Herkenhoff, K.; Hansen, C.; Bridges, N.; Delamere, W. A.; Eliason, E.; Grant, J.; Gulick, V.; Keszthelyi, L.; Kirk, R.

2003-01-01

The Mars Reconnaissance Orbiter (MRO) is expected to launch in August 2005, arrive at Mars in March 2006, and begin the primary science phase in November 2006. MRO will carry a suite of remote-sensing instruments and is designed to routinely point off-nadir to precisely target locations on Mars for high-resolution observations. The mission will have a much higher data return than any previous planetary mission, with 34 Tbits of returned data expected in the first Mars year in the mapping orbit (255 x 320 km). The HiRISE camera features a 0.5 m telescope, 12 m focal length, and 14 CCDs. We expect to acquire approximately 10,000 observations in the primary science phase (approximately 1 Mars year), including approximately 2,000 images for 1,000 stereo targets. Each observation will be accompanied by a approximately 6 m/pixel image over a 30 x 45 km region acquired by MRO s context imager. Many HiRISE images will be full resolution in the center portion of the swath width and binned (typically 4x4) on the sides. This provides two levels of context, so we step out from 0.3 m/pixel to 1.2 m/pixel to 6 m/pixel (at 300 km altitude). We expect to cover approximately 1% of Mars at better than 1.2 m/pixel, approximately 0.1% at 0.3 m/pixel, approximately 0.1% in 3 colors, and approximately 0.05% in stereo. Our major challenge is to find the dey contacts, exposures and type morphologies to observe.

The analysis and rationale behind the upgrading of existing standard definition thermal imagers to high definition

NASA Astrophysics Data System (ADS)

Goss, Tristan M.

2016-05-01

With 640x512 pixel format IR detector arrays having been on the market for the past decade, Standard Definition (SD) thermal imaging sensors have been developed and deployed across the world. Now with 1280x1024 pixel format IR detector arrays becoming readily available designers of thermal imager systems face new challenges as pixel sizes reduce and the demand and applications for High Definition (HD) thermal imaging sensors increases. In many instances the upgrading of existing under-sampled SD thermal imaging sensors into more optimally sampled or oversampled HD thermal imaging sensors provides a more cost effective and reduced time to market option than to design and develop a completely new sensor. This paper presents the analysis and rationale behind the selection of the best suited HD pixel format MWIR detector for the upgrade of an existing SD thermal imaging sensor to a higher performing HD thermal imaging sensor. Several commercially available and "soon to be" commercially available HD small pixel IR detector options are included as part of the analysis and are considered for this upgrade. The impact the proposed detectors have on the sensor's overall sensitivity, noise and resolution is analyzed, and the improved range performance is predicted. Furthermore with reduced dark currents due to the smaller pixel sizes, the candidate HD MWIR detectors are operated at higher temperatures when compared to their SD predecessors. Therefore, as an additional constraint and as a design goal, the feasibility of achieving upgraded performance without any increase in the size, weight and power consumption of the thermal imager is discussed herein.

Spatial resolution and chest nodule detection: an interesting incidental finding

NASA Astrophysics Data System (ADS)

Toomey, R. J.; McEntee, M. F.; Ryan, J. T.; Evanoff, M. G.; Hayes, A.; Brennan, P. C.

2010-02-01

This study reports an incidental finding from a larger work. It examines the relationship between spatial resolution and nodule detection for chest radiographs. Twelve examining radiologists with the American Board of Radiology read thirty chest radiographs in two conditions - full (1500 × 1500 pixel) resolution, and 300 × 300 pixel resolution linearly interpolated to 1500 × 1500 pixels. All images were surrounded by a 10-pixel sharp grey border to aid in focussing the observer's eye when viewing the comparatively unsharp interpolated images. Fifteen of the images contained a single simulated pulmonary nodule. Observers were asked to rate their confidence that a nodule was present on each radiograph on a scale of 1 (least confidence, certain no lesion is present) to 6 (most confidence, certain a lesion was present). All other abnormalities were to be ignored. No windowing, levelling or magnification of the images was permitted and viewing distance was constrained to approximately 70cm. Images were displayed on a 3 megapixel greyscale monitor. Receiver operating characteristic (ROC) analysis was applied to the results of the readings using the Dorfman-Berbaum-Metz multiplereader, multiple-case method. No statistically significant differences were found with either readers and cases treated as random or with cases treated as fixed. Low spatial frequency information appears to be sufficient for the detection of chest lesion of the type used in this study.

Quantifying the Uncertainty in High Spatial and Temporal Resolution Synthetic Land Surface Reflectance at Pixel Level Using Ground-Based Measurements

NASA Astrophysics Data System (ADS)

Kong, J.; Ryu, Y.

2017-12-01

Algorithms for fusing high temporal frequency and high spatial resolution satellite images are widely used to develop dense time-series land surface observations. While many studies have revealed that the synthesized frequent high spatial resolution images could be successfully applied in vegetation mapping and monitoring, validation and correction of fused images have not been focused than its importance. To evaluate the precision of fused image in pixel level, in-situ reflectance measurements which could account for the pixel-level heterogeneity are necessary. In this study, the synthetic images of land surface reflectance were predicted by the coarse high-frequency images acquired from MODIS and high spatial resolution images from Landsat-8 OLI using the Flexible Spatiotemporal Data Fusion (FSDAF). Ground-based reflectance was measured by JAZ Spectrometer (Ocean Optics, Dunedin, FL, USA) on rice paddy during five main growth stages in Cheorwon-gun, Republic of Korea, where the landscape heterogeneity changes through the growing season. After analyzing the spatial heterogeneity and seasonal variation of land surface reflectance based on the ground measurements, the uncertainties of the fused images were quantified at pixel level. Finally, this relationship was applied to correct the fused reflectance images and build the seasonal time series of rice paddy surface reflectance. This dataset could be significant for rice planting area extraction, phenological stages detection, and variables estimation.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lecomte, Roger; Arpin, Louis; Beaudoin, Jean-Franç

Purpose: LabPET II is a new generation APD-based PET scanner designed to achieve sub-mm spatial resolution using truly pixelated detectors and highly integrated parallel front-end processing electronics. Methods: The basic element uses a 4×8 array of 1.12×1.12 mm{sup 2} Lu{sub 1.9}Y{sub 0.1}SiO{sub 5}:Ce (LYSO) scintillator pixels with one-to-one coupling to a 4×8 pixelated monolithic APD array mounted on a ceramic carrier. Four detector arrays are mounted on a daughter board carrying two flip-chip, 64-channel, mixed-signal, application-specific integrated circuits (ASIC) on the backside interfacing to two detector arrays each. Fully parallel signal processing was implemented in silico by encoding time andmore » energy information using a dual-threshold Time-over-Threshold (ToT) scheme. The self-contained 128-channel detector module was designed as a generic component for ultra-high resolution PET imaging of small to medium-size animals. Results: Energy and timing performance were optimized by carefully setting ToT thresholds to minimize the noise/slope ratio. ToT spectra clearly show resolved 511 keV photopeak and Compton edge with ToT resolution well below 10%. After correction for nonlinear ToT response, energy resolution is typically 24±2% FWHM. Coincidence time resolution between opposing 128-channel modules is below 4 ns FWHM. Initial imaging results demonstrate that 0.8 mm hot spots of a Derenzo phantom can be resolved. Conclusion: A new generation PET scanner featuring truly pixelated detectors was developed and shown to achieve a spatial resolution approaching the physical limit of PET. Future plans are to integrate a small-bore dedicated mouse version of the scanner within a PET/CT platform.« less

NDVI, scale invariance and the modifiable areal unit problem: An assessment of vegetation in the Adelaide Parklands

USGS Publications Warehouse

Nouri, Hamideh; Anderson, Sharolyn; Sutton, Paul; Beecham, Simon; Nagler, Pamela L.; Jarchow, Christopher J.; Roberts, Dar A.

2017-01-01

This research addresses the question as to whether or not the Normalised Difference Vegetation Index (NDVI) is scale invariant (i.e. constant over spatial aggregation) for pure pixels of urban vegetation. It has been long recognized that there are issues related to the modifiable areal unit problem (MAUP) pertaining to indices such as NDVI and images at varying spatial resolutions. These issues are relevant to using NDVI values in spatial analyses. We compare two different methods of calculation of a mean NDVI: 1) using pixel values of NDVI within feature/object boundaries and 2) first calculating the mean red and mean near-infrared across all feature pixels and then calculating NDVI. We explore the nature and magnitude of these differences for images taken from two sensors, a 1.24 m resolution WorldView-3 and a 0.1 m resolution digital aerial image. We apply these methods over an urban park located in the Adelaide Parklands of South Australia. We demonstrate that the MAUP is not an issue for calculation of NDVI within a sensor for pure urban vegetation pixels. This may prove useful for future rule-based monitoring of the ecosystem functioning of green infrastructure.

Spatial resolution of a hard x-ray CCD detector.

PubMed

Seely, John F; Pereira, Nino R; Weber, Bruce V; Schumer, Joseph W; Apruzese, John P; Hudson, Lawrence T; Szabo, Csilla I; Boyer, Craig N; Skirlo, Scott

2010-08-10

The spatial resolution of an x-ray CCD detector was determined from the widths of the tungsten x-ray lines in the spectrum formed by a crystal spectrometer in the 58 to 70 keV energy range. The detector had 20 microm pixel, 1700 by 1200 pixel format, and a CsI x-ray conversion scintillator. The spectral lines from a megavolt x-ray generator were focused on the spectrometer's Rowland circle by a curved transmission crystal. The line shapes were Lorentzian with an average width after removal of the natural and instrumental line widths of 95 microm (4.75 pixels). A high spatial frequency background, primarily resulting from scattered gamma rays, was removed from the spectral image by Fourier analysis. The spectral lines, having low spatial frequency in the direction perpendicular to the dispersion, were enhanced by partially removing the Lorentzian line shape and by fitting Lorentzian curves to broad unresolved spectral features. This demonstrates the ability to improve the spectral resolution of hard x-ray spectra that are recorded by a CCD detector with well-characterized intrinsic spatial resolution.

Capturing and displaying microscopic images used in medical diagnostics and forensic science using 4K video resolution - an application in higher education.

PubMed

Maier, Hans; de Heer, Gert; Ortac, Ajda; Kuijten, Jan

2015-11-01

To analyze, interpret and evaluate microscopic images, used in medical diagnostics and forensic science, video images for educational purposes were made with a very high resolution of 4096 × 2160 pixels (4K), which is four times as many pixels as High-Definition Video (1920 × 1080 pixels). The unprecedented high resolution makes it possible to see details that remain invisible to any other video format. The images of the specimens (blood cells, tissue sections, hair, fibre, etc.) are recorded using a 4K video camera which is attached to a light microscope. After processing, this resulted in very sharp and highly detailed images. This material was then used in education for classroom discussion. Spoken explanation by experts in the field of medical diagnostics and forensic science was also added to the high-resolution video images to make it suitable for self-study. © 2015 The Authors. Journal of Microscopy published by John Wiley & Sons Ltd on behalf of Royal Microscopical Society.

A high efficiency readout architecture for a large matrix of pixels.

NASA Astrophysics Data System (ADS)

Gabrielli, A.; Giorgi, F.; Villa, M.

2010-07-01

In this work we present a fast readout architecture for silicon pixel matrix sensors that has been designed to sustain very high rates, above 1 MHz/mm2 for matrices greater than 80k pixels. This logic can be implemented within MAPS (Monolithic Active Pixel Sensors), a kind of high resolution sensor that integrates on the same bulk the sensor matrix and the CMOS logic for readout, but it can be exploited also with other technologies. The proposed architecture is based on three main concepts. First of all, the readout of the hits is performed by activating one column at a time; all the fired pixels on the active column are read, sparsified and reset in parallel in one clock cycle. This implies the use of global signals across the sensor matrix. The consequent reduction of metal interconnections improves the active area while maintaining a high granularity (down to a pixel pitch of 40 μm). Secondly, the activation for readout takes place only for those columns overlapping with a certain fired area, thus reducing the sweeping time of the whole matrix and reducing the pixel dead-time. Third, the sparsification (x-y address labeling of the hits) is performed with a lower granularity with respect to single pixels, by addressing vertical zones of 8 pixels each. The fine-grain Y resolution is achieved by appending the zone pattern to the zone address of a hit. We show then the benefits of this technique in presence of clusters. We describe this architecture from a schematic point of view, then presenting the efficiency results obtained by VHDL simulations.

Test beam performance measurements for the Phase I upgrade of the CMS pixel detector

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dragicevic, M.; Friedl, M.; Hrubec, J.

A new pixel detector for the CMS experiment was built in order to cope with the instantaneous luminosities anticipated for the Phase~I Upgrade of the LHC. The new CMS pixel detector provides four-hit tracking with a reduced material budget as well as new cooling and powering schemes. A new front-end readout chip mitigates buffering and bandwidth limitations, and allows operation at low comparator thresholds. Here in this paper, comprehensive test beam studies are presented, which have been conducted to verify the design and to quantify the performance of the new detector assemblies in terms of tracking efficiency and spatial resolution. Under optimal conditions, the tracking efficiency ismore » $$99.95\\pm0.05\\,\\%$$, while the intrinsic spatial resolutions are $$4.80\\pm0.25\\,\\mu \\mathrm{m}$$ and $$7.99\\pm0.21\\,\\mu \\mathrm{m}$$ along the $$100\\,\\mu \\mathrm{m}$$ and $$150\\,\\mu \\mathrm{m}$$ pixel pitch, respectively. The findings are compared to a detailed Monte Carlo simulation of the pixel detector and good agreement is found.« less

In-situ device integration of large-area patterned organic nanowire arrays for high-performance optical sensors

PubMed Central

Wu, Yiming; Zhang, Xiujuan; Pan, Huanhuan; Deng, Wei; Zhang, Xiaohong; Zhang, Xiwei; Jie, Jiansheng

2013-01-01

Single-crystalline organic nanowires (NWs) are important building blocks for future low-cost and efficient nano-optoelectronic devices due to their extraordinary properties. However, it remains a critical challenge to achieve large-scale organic NW array assembly and device integration. Herein, we demonstrate a feasible one-step method for large-area patterned growth of cross-aligned single-crystalline organic NW arrays and their in-situ device integration for optical image sensors. The integrated image sensor circuitry contained a 10 × 10 pixel array in an area of 1.3 × 1.3 mm2, showing high spatial resolution, excellent stability and reproducibility. More importantly, 100% of the pixels successfully operated at a high response speed and relatively small pixel-to-pixel variation. The high yield and high spatial resolution of the operational pixels, along with the high integration level of the device, clearly demonstrate the great potential of the one-step organic NW array growth and device construction approach for large-scale optoelectronic device integration. PMID:24287887

Performance measurements of hybrid PIN diode arrays

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jernigan, J.G.; Arens, J.F.; Kramer, G.

We report on the successful effort to develop hybrid PIN diode arrays and to demonstrate their potential as components of vertex detectors. Hybrid pixel arrays have been fabricated by the Hughes Aircraft Co. by bump bonding readout chips developed by Hughes to an array of PIN diodes manufactured by Micron Semiconductor Inc. These hybrid pixel arrays were constructed in two configurations. One array format having 10 {times} 64 pixels, each 120 {mu}m square, and the other format having 256 {times} 256 pixels, each 30 {mu}m square. In both cases, the thickness of the PIN diode layer is 300 {mu}m. Measurementsmore » of detector performance show that excellent position resolution can be achieved by interpolation. By determining the centroid of the charge cloud which spreads charge into a number of neighboring pixels, a spatial resolution of a few microns has been attained. The noise has been measured to be about 300 electrons (rms) at room temperature, as expected from KTC and dark current considerations, yielding a signal-to-noise ratio of about 100 for minimum ionizing particles. 4 refs., 13 figs.« less

Test beam performance measurements for the Phase I upgrade of the CMS pixel detector

DOE PAGES

Dragicevic, M.; Friedl, M.; Hrubec, J.; ...

2017-05-30

A new pixel detector for the CMS experiment was built in order to cope with the instantaneous luminosities anticipated for the Phase~I Upgrade of the LHC. The new CMS pixel detector provides four-hit tracking with a reduced material budget as well as new cooling and powering schemes. A new front-end readout chip mitigates buffering and bandwidth limitations, and allows operation at low comparator thresholds. Here in this paper, comprehensive test beam studies are presented, which have been conducted to verify the design and to quantify the performance of the new detector assemblies in terms of tracking efficiency and spatial resolution. Under optimal conditions, the tracking efficiency ismore » $$99.95\\pm0.05\\,\\%$$, while the intrinsic spatial resolutions are $$4.80\\pm0.25\\,\\mu \\mathrm{m}$$ and $$7.99\\pm0.21\\,\\mu \\mathrm{m}$$ along the $$100\\,\\mu \\mathrm{m}$$ and $$150\\,\\mu \\mathrm{m}$$ pixel pitch, respectively. The findings are compared to a detailed Monte Carlo simulation of the pixel detector and good agreement is found.« less

Simultaneous fluorescence and quantitative phase microscopy with single-pixel detectors

NASA Astrophysics Data System (ADS)

Liu, Yang; Suo, Jinli; Zhang, Yuanlong; Dai, Qionghai

2018-02-01

Multimodal microscopy offers high flexibilities for biomedical observation and diagnosis. Conventional multimodal approaches either use multiple cameras or a single camera spatially multiplexing different modes. The former needs expertise demanding alignment and the latter suffers from limited spatial resolution. Here, we report an alignment-free full-resolution simultaneous fluorescence and quantitative phase imaging approach using single-pixel detectors. By combining reference-free interferometry with single-pixel detection, we encode the phase and fluorescence of the sample in two detection arms at the same time. Then we employ structured illumination and the correlated measurements between the sample and the illuminations for reconstruction. The recovered fluorescence and phase images are inherently aligned thanks to single-pixel detection. To validate the proposed method, we built a proof-of-concept setup for first imaging the phase of etched glass with the depth of a few hundred nanometers and then imaging the fluorescence and phase of the quantum dot drop. This method holds great potential for multispectral fluorescence microscopy with additional single-pixel detectors or a spectrometer. Besides, this cost-efficient multimodal system might find broad applications in biomedical science and neuroscience.

Meteosat SEVIRI Fire Radiative Power (FRP) products from the Land Surface Analysis Satellite Applications Facility (LSA SAF) - Part 1: Algorithms, product contents and analysis

NASA Astrophysics Data System (ADS)

Wooster, M. J.; Roberts, G.; Freeborn, P. H.; Xu, W.; Govaerts, Y.; Beeby, R.; He, J.; Lattanzio, A.; Mullen, R.

2015-06-01

Characterising changes in landscape scale fire activity at very high temporal resolution is best achieved using thermal observations of actively burning fires made from geostationary Earth observation (EO) satellites. Over the last decade or more, a series of research and/or operational "active fire" products have been developed from these types of geostationary observations, often with the aim of supporting the generation of data related to biomass burning fuel consumption and trace gas and aerosol emission fields. The Fire Radiative Power (FRP) products generated by the Land Surface Analysis Satellite Applications Facility (LSA SAF) from data collected by the Meteosat Second Generation (MSG) Spinning Enhanced Visible and Infrared Imager (SEVIRI) are one such set of products, and are freely available in both near real-time and archived form. Every 15 min, the algorithms used to generate these products identify and map the location of new SEVIRI observations containing actively burning fires, and characterise their individual rates of radiative energy release (fire radiative power; FRP) that is believed proportional to rates of biomass consumption and smoke emission. The FRP-PIXEL product contains the highest spatial resolution FRP dataset, delivered for all of Europe, northern and southern Africa, and part of South America at a spatial resolution of 3 km (decreasing away from the west African sub-satellite point) at the full 15 min temporal resolution. The FRP-GRID product is an hourly summary of the FRP-PIXEL data, produced at a 5° grid cell size and including simple bias adjustments for meteorological cloud cover and for the regional underestimation of FRP caused, primarily, by the non-detection of low FRP fire pixels at SEVIRI's relatively coarse pixel size. Here we describe the enhanced geostationary Fire Thermal Anomaly (FTA) algorithm used to detect the SEVIRI active fire pixels, and detail methods used to deliver atmospherically corrected FRP information together with the per-pixel uncertainty metrics. Using scene simulations and analysis of real SEVIRI data, including from a period of Meteosat-8 "special operations", we describe some of the sensor and data pre-processing characteristics influencing fire detection and FRP uncertainty. We show that the FTA algorithm is able to discriminate actively burning fires covering down to 10-4 of a pixel, and is more sensitive to fire than algorithms used within many other widely exploited active fire products. We also find that artefacts arising from the digital filtering and geometric resampling strategies used to generate level 1.5 SEVIRI data can significantly increase FRP uncertainties in the SEVIRI active fire products, and recommend that the processing chains used for the forthcoming Meteosat Third Generation attempt to minimise the impact of these types of operations. Finally, we illustrate the information contained within the current Meteosat FRP-PIXEL and FRP-GRID products, providing example analyses for both individual fires and multi-year regional-scale fire activity. A companion paper (Roberts et al., 2015) provides a full product performance evaluation for both products, along with examples of their use for prescribing fire smoke emissions within atmospheric modelling components of the Copernicus Atmosphere Monitoring Service (CAMS).

New results on diamond pixel sensors using ATLAS frontend electronics

NASA Astrophysics Data System (ADS)

Keil, M.; Adam, W.; Berdermann, E.; Bergonzo, P.; de Boer, W.; Bogani, F.; Borchi, E.; Brambilla, A.; Bruzzi, M.; Colledani, C.; Conway, J.; D'Angelo, P.; Dabrowski, W.; Delpierre, P.; Dulinski, W.; Doroshenko, J.; Doucet, M.; van Eijk, B.; Fallou, A.; Fischer, P.; Fizzotti, F.; Kania, D.; Gan, K. K.; Grigoriev, E.; Hallewell, G.; Han, S.; Hartjes, F.; Hrubec, J.; Husson, D.; Kagan, H.; Kaplon, J.; Kass, R.; Knöpfle, K. T.; Koeth, T.; Krammer, M.; Logiudice, A.; mac Lynne, L.; Manfredotti, C.; Meier, D.; Menichelli, D.; Meuser, S.; Mishina, M.; Moroni, L.; Noomen, J.; Oh, A.; Pan, L. S.; Pernicka, M.; Perera, L.; Riester, J. L.; Roe, S.; Rudge, A.; Russ, J.; Sala, S.; Sampietro, M.; Schnetzer, S.; Sciortino, S.; Stelzer, H.; Stone, R.; Suter, B.; Trischuk, W.; Tromson, D.; Vittone, E.; Weilhammer, P.; Wermes, N.; Wetstein, M.; Zeuner, W.; Zoeller, M.

2003-03-01

Diamond is a promising sensor material for future collider experiments due to its radiation hardness. Diamond pixel sensors have been bump bonded to an ATLAS pixel readout chip using PbSn solder bumps. Single chip devices have been characterised by lab measurements and in a high-energy pion beam at CERN. Results on charge collection, spatial resolution, efficiency and the charge carrier lifetime are presented.

High-resolution fluence verification for treatment plan specific QA in ion beam radiotherapy

NASA Astrophysics Data System (ADS)

Martišíková, Mária; Brons, Stephan; Hesse, Bernd M.; Jäkel, Oliver

2013-03-01

Ion beam radiotherapy exploits the finite range of ion beams and the increased dose deposition of ions toward the end of their range in material. This results in high dose conformation to the target region, which can be further increased using scanning ion beams. The standard method for patient-plan verification in ion beam therapy is ionization chamber dosimetry. The spatial resolution of this method is given by the distance between the chambers (typically 1 cm). However, steep dose gradients created by scanning ion beams call for more information and improved spatial resolution. Here we propose a clinically applicable method, supplementary to standard patient-plan verification. It is based on ion fluence measurements in the entrance region with high spatial resolution in the plane perpendicular to the beam, separately for each energy slice. In this paper the usability of the RID256 L amorphous silicon flat-panel detector for the measurements proposed is demonstrated for carbon ion beams. The detector provides sufficient spatial resolution for this kind of measurement (pixel pitch 0.8 mm). The experiments were performed at the Heidelberg Ion-Beam Therapy Center in Germany. This facility is equipped with a synchrotron capable of accelerating ions from protons up to oxygen to energies between 48 and 430 MeV u-1. Beam application is based on beam scanning technology. The measured signal corresponding to single energy slices was translated to ion fluence on a pixel-by-pixel basis, using calibration, which is dependent on energy and ion type. To quantify the agreement of the fluence distributions measured with those planned, a gamma-index criterion was used. In the patient field investigated excellent agreement was found between the two distributions. At least 95% of the slices contained more than 96% of points agreeing with our criteria. Due to the high spatial resolution, this method is especially valuable for measurements of strongly inhomogeneous fluence distributions like those in intensity-modulated treatment plans or plans including dose painting. Since no water phantom is needed to perform measurements, the flat-panel detector investigated has high potential for use with gantries. Before the method can be used in the clinical routine, it has to be sufficiently tested for each detector-facility combination.

Towards global Landsat burned area mapping: revisit time and availability of cloud free observations

NASA Astrophysics Data System (ADS)

Melchiorre, A.; Boschetti, L.

2016-12-01

Global, daily coarse resolution satellite data have been extensively used for systematic burned area mapping (Giglio et al. 2013; Mouillot et al. 2014). The adoption of similar approaches for producing moderate resolution (10 - 30 m) global burned area products would lead to very significant improvements for the wide variety of fire information users. It would meet a demand for accurate burned area perimeters needed for fire management, post-fire assessment and environmental restoration, and would lead to more accurate and precise atmospheric emission estimations, especially over heterogeneous areas (Mouillot et al. 2014; Randerson et al. 2012; van der Werf et al. 2010). The increased spatial resolution clearly benefits mapping accuracy: the reduction of mixed pixels directly translates in increased spectral separation compared to coarse resolution data. As a tradeoff, the lower temporal resolution (e.g. 16 days for Landsat), could potentially cause large omission errors in ecosystems with fast post-fire recovery. The spectral signal due to the fire effects is non-permanent, can be detected for a period ranging from a few weeks in savannas and grasslands, to over a year in forest ecosystems (Roy et al. 2010). Additionally, clouds, smoke, and other optically thick aerosols limit the number of available observations (Roy et al. 2008; Smith and Wooster 2005), exacerbating the issues related to mapping burned areas globally with moderate resolution sensors. This study presents a global analysis of the effect of cloud cover on Landsat data availability over burned areas, by analyzing the MODIS data record of burned area (MCD45) and cloud detections (MOD35), and combining it with the Landsat acquisition calendar and viewing geometry. For each pixel classified as burned in the MCD45 product, the MOD35 data are used to determine how many cloud free observations would have been available on Landsat overpass days, within the period of observability of the burned area spectral signal in the specific ecosystem. If a burned area pixel is covered by clouds on all the post-fire Landsat overpass days, we assume that it would not be detected in a hypothetical Landsat global burned area product. The resulting maps of expected omission errors are combined for the full 15-year MODIS dataset, and summarized by ecoregion and landcover class.

Satellite image time series simulation for environmental monitoring

NASA Astrophysics Data System (ADS)

Guo, Tao

2014-11-01

The performance of environmental monitoring heavily depends on the availability of consecutive observation data and it turns out an increasing demand in remote sensing community for satellite image data in the sufficient resolution with respect to both spatial and temporal requirements, which appear to be conflictive and hard to tune tradeoffs. Multiple constellations could be a solution if without concerning cost, and thus it is so far interesting but very challenging to develop a method which can simultaneously improve both spatial and temporal details. There are some research efforts to deal with the problem from various aspects, a type of approaches is to enhance the spatial resolution using techniques of super resolution, pan-sharpen etc. which can produce good visual effects, but mostly cannot preserve spectral signatures and result in losing analytical value. Another type is to fill temporal frequency gaps by adopting time interpolation, which actually doesn't increase informative context at all. In this paper we presented a novel method to generate satellite images in higher spatial and temporal details, which further enables satellite image time series simulation. Our method starts with a pair of high-low resolution data set, and then a spatial registration is done by introducing LDA model to map high and low resolution pixels correspondingly. Afterwards, temporal change information is captured through a comparison of low resolution time series data, and the temporal change is then projected onto high resolution data plane and assigned to each high resolution pixel referring the predefined temporal change patterns of each type of ground objects to generate a simulated high resolution data. A preliminary experiment shows that our method can simulate a high resolution data with a good accuracy. We consider the contribution of our method is to enable timely monitoring of temporal changes through analysis of low resolution images time series only, and usage of costly high resolution data can be reduced as much as possible, and it presents an efficient solution with great cost performance to build up an economically operational monitoring service for environment, agriculture, forest, land use investigation, and other applications.

Detailed Studies of Pixelated CZT Detectors Grown with the Modified Horizontal Bridgman Method

NASA Technical Reports Server (NTRS)

Jung, I.; Krawczynski, H.; Burger, A.; Guo, M.; Groza, M.

2007-01-01

The detector material Cadmium Zinc Telluride (CZT) achieves excellent spatial resolution and good energy resolution over a broad energy range, several keV up to some MeV. Presently, there are two main methods to grow CZT crystals, the Modified High-Pressure Bridgman (MHB) and the High-Pressure Bridgman (HPB) process. The study presented in this paper is based on MHB CZT substrates from the company Orbotech Medical Solutions Ltd. [Orbotech Medical Solutions Ltd., 10 Plaut St., Park Rabin, P.O. Box 2489, Rehovot, Israel, 76124]. Former studies have shown that high-work-function materials on the cathode side reduce the leakage current and, therefore, improve the energy resolution at lower energies. None of the studies have emphasized on the anode contact material. Therefore, we present in this paper the result of a detailed study in which for the first time the cathode material was kept constant and the anode material was varied. We used four different anode materials: Indium, Titanium, Chromium and Gold, metals with work-functions between 4.1 eV and 5.1 eV. The detector size was 2.0 x 2.0 x 0.5 cu cm with 8 x 8 pixels and a pitch of 2.46 mm. The best performance was achieved with the low-work-function materials Indium and Titanium with energy resolutions of 2.0 keV (at 59 keV) and 1.9 keV (at 122 keV) for Titanium and 2.1 keV (at 59 keV) and 2.9 keV (at 122 keV) for Indium. Taking into account the large pixel pitch of 2.46 mm, these resolutions are very competitive in comparison to those achieved with detectors made of material produced with the more expensive conventional HPB method. We present a detailed comparison of our detector response with 3D simulations. The latter comparisons allow us to determine the mobility-lifetime-products (mu tau-products) for electrons and holes. Finally, we evaluated the temperature dependency of the detector performance and ls-products. For many applications temperature dependence is important, therefore, we extended the scope of our study to temperatures as low as -30 C. There are two important results. The breakdown voltage increases with decreasing temperature, and electron mobility-lifetime-product decreases by about 30% over a range from 20 C to -30 C. The latter effect causes the energy resolution to deteriorate, but the concomitantly increasing breakdown voltage makes it possible to increase the applied bias voltage and restore the full performance

High-resolution mapping of Martian water ice clouds using Mars Express OMEGA observations - Derivation of the diurnal cloud life cycle

NASA Astrophysics Data System (ADS)

Szantai, Andre; Audouard, Joachim; Madeleine, Jean-Baptiste; Forget, Francois; Pottier, Alizée; Millour, Ehouarn; Gondet, Brigitte; Langevin, Yves; Bibring, Jean-Pierre

2016-10-01

The mapping in space and time of water ice clouds can help to explain the Martian water cycle and atmospheric circulation. For this purpose, an ice cloud index (ICI) corresponding to the depth of a water ice absorption band at 3.4 microns is derived from a series of OMEGA images (spectels) covering 5 Martian years. The ICI values for the corresponding pixels are then binned on a high-resolution regular grid (1° longitude x 1° latitude x 5° Ls x 1 h local time) and averaged. Inside each bin, the cloud cover is calculated by dividing the number of pixels considered as cloudy (after comparison to a threshold) to the number of all (valid) pixelsWe compare the maps of clouds obtained around local time 14:00 with collocated TES cloud observations (which were only obtained around this time of the day). A good agreement is found.Averaged ICI compared to the water ice column variable from the Martian Climate Database (MCD) show a correct correlation (~0.5) , which increases when values limited to the tropics only are compared.The number of gridpoints containing ICI values is small ( ~1%), but by taking several neighbor gridpoints and over longer periods, we can observe a cloud life cycle during daytime. An example in the the tropics, around the northern summer solstice, shows a decrease of cloudiness in the morning followed by an increase in the afternoon.

Efficient space-time sampling with pixel-wise coded exposure for high-speed imaging.

PubMed

Liu, Dengyu; Gu, Jinwei; Hitomi, Yasunobu; Gupta, Mohit; Mitsunaga, Tomoo; Nayar, Shree K

2014-02-01

Cameras face a fundamental trade-off between spatial and temporal resolution. Digital still cameras can capture images with high spatial resolution, but most high-speed video cameras have relatively low spatial resolution. It is hard to overcome this trade-off without incurring a significant increase in hardware costs. In this paper, we propose techniques for sampling, representing, and reconstructing the space-time volume to overcome this trade-off. Our approach has two important distinctions compared to previous works: 1) We achieve sparse representation of videos by learning an overcomplete dictionary on video patches, and 2) we adhere to practical hardware constraints on sampling schemes imposed by architectures of current image sensors, which means that our sampling function can be implemented on CMOS image sensors with modified control units in the future. We evaluate components of our approach, sampling function and sparse representation, by comparing them to several existing approaches. We also implement a prototype imaging system with pixel-wise coded exposure control using a liquid crystal on silicon device. System characteristics such as field of view and modulation transfer function are evaluated for our imaging system. Both simulations and experiments on a wide range of scenes show that our method can effectively reconstruct a video from a single coded image while maintaining high spatial resolution.

IMPROVING THE ACCURACY OF HISTORIC SATELLITE IMAGE CLASSIFICATION BY COMBINING LOW-RESOLUTION MULTISPECTRAL DATA WITH HIGH-RESOLUTION PANCHROMATIC DATA

DOE Office of Scientific and Technical Information (OSTI.GOV)

Getman, Daniel J

2008-01-01

Many attempts to observe changes in terrestrial systems over time would be significantly enhanced if it were possible to improve the accuracy of classifications of low-resolution historic satellite data. In an effort to examine improving the accuracy of historic satellite image classification by combining satellite and air photo data, two experiments were undertaken in which low-resolution multispectral data and high-resolution panchromatic data were combined and then classified using the ECHO spectral-spatial image classification algorithm and the Maximum Likelihood technique. The multispectral data consisted of 6 multispectral channels (30-meter pixel resolution) from Landsat 7. These data were augmented with panchromatic datamore » (15m pixel resolution) from Landsat 7 in the first experiment, and with a mosaic of digital aerial photography (1m pixel resolution) in the second. The addition of the Landsat 7 panchromatic data provided a significant improvement in the accuracy of classifications made using the ECHO algorithm. Although the inclusion of aerial photography provided an improvement in accuracy, this improvement was only statistically significant at a 40-60% level. These results suggest that once error levels associated with combining aerial photography and multispectral satellite data are reduced, this approach has the potential to significantly enhance the precision and accuracy of classifications made using historic remotely sensed data, as a way to extend the time range of efforts to track temporal changes in terrestrial systems.« less

Preliminary investigations of active pixel sensors in Nuclear Medicine imaging

NASA Astrophysics Data System (ADS)

Ott, Robert; Evans, Noel; Evans, Phil; Osmond, J.; Clark, A.; Turchetta, R.

2009-06-01

Three CMOS active pixel sensors have been investigated for their application to Nuclear Medicine imaging. Startracker with 525×525 25 μm square pixels has been coupled via a fibre optic stud to a 2 mm thick segmented CsI(Tl) crystal. Imaging tests were performed using 99mTc sources, which emit 140 keV gamma rays. The system was interfaced to a PC via FPGA-based DAQ and optical link enabling imaging rates of 10 f/s. System noise was measured to be >100e and it was shown that the majority of this noise was fixed pattern in nature. The intrinsic spatial resolution was measured to be ˜80 μm and the system spatial resolution measured with a slit was ˜450 μm. The second sensor, On Pixel Intelligent CMOS (OPIC), had 64×72 40 μm pixels and was used to evaluate noise characteristics and to develop a method of differentiation between fixed pattern and statistical noise. The third sensor, Vanilla, had 520×520 25 μm pixels and a measured system noise of ˜25e. This sensor was coupled directly to the segmented phosphor. Imaging results show that even at this lower level of noise the signal from 140 keV gamma rays is small as the light from the phosphor is spread over a large number of pixels. Suggestions for the 'ideal' sensor are made.

Bringing the Coastal Zone into Finer Focus

NASA Astrophysics Data System (ADS)

Guild, L. S.; Hooker, S. B.; Kudela, R. M.; Morrow, J. H.; Torres-Perez, J. L.; Palacios, S. L.; Negrey, K.; Dungan, J. L.

2015-12-01

Measurements over extents from submeter to 10s of meters are critical science requirements for the design and integration of remote sensing instruments for coastal zone research. Various coastal ocean phenomena operate at different scales (e.g. meters to kilometers). For example, river plumes and algal blooms have typical extents of 10s of meters and therefore can be resolved with satellite data, however, shallow benthic ecosystem (e.g., coral, seagrass, and kelp) biodiversity and change are best studied at resolutions of submeter to meter, below the pixel size of typical satellite products. The delineation of natural phenomena do not fit nicely into gridded pixels and the coastal zone is complicated by mixed pixels at the land-sea interface with a range of bio-optical signals from terrestrial and water components. In many standard satellite products, these coastal mixed pixels are masked out because they confound algorithms for the ocean color parameter suite. In order to obtain data at the land/sea interface, finer spatial resolution satellite data can be achieved yet spectral resolution is sacrificed. This remote sensing resolution challenge thwarts the advancement of research in the coastal zone. Further, remote sensing of benthic ecosystems and shallow sub-surface phenomena are challenged by the requirements to sense through the sea surface and through a water column with varying light conditions from the open ocean to the water's edge. For coastal waters, >80% of the remote sensing signal is scattered/absorbed due to the atmospheric constituents, sun glint from the sea surface, and water column components. In addition to in-water measurements from various platforms (e.g., ship, glider, mooring, and divers), low altitude aircraft outfitted with high quality bio-optical radiometer sensors and targeted channels matched with in-water sensors and higher altitude platform sensors for ocean color products, bridge the sea-truth measurements to the pixels acquired from satellite and high altitude platforms. We highlight a novel NASA airborne calibration, validation, and research capability for addressing the coastal remote sensing resolution challenge.

The Dram As An X-Ray Sensor

NASA Astrophysics Data System (ADS)

Jacobs, Alan M.; Cox, John D.; Juang, Yi-Shung

1987-01-01

A solid-state digital x-ray detector is described which can replace high resolution film in industrial radiography and has potential for application in some medical imaging. Because of the 10 micron pixel pitch on the sensor, contact magnification radiology is possible and is demonstrated. Methods for frame speed increase and integration of sensor to a large format are discussed.

Evaluation of different shadow detection and restoration methods and their impact on vegetation indices using UAV high-resolution imageries over vineyards

NASA Astrophysics Data System (ADS)

Aboutalebi, M.; Torres-Rua, A. F.; McKee, M.; Kustas, W. P.; Nieto, H.

2017-12-01

Shadows are an unavoidable component of high-resolution imagery. Although shadows can be a useful source of information about terrestrial features, they are a hindrance for image processing and lead to misclassification errors and increased uncertainty in defining surface reflectance properties. In precision agriculture activities, shadows may affect the performance of vegetation indices at pixel and plant scales. Thus, it becomes necessary to evaluate existing shadow detection and restoration methods, especially for applications that makes direct use of pixel information to estimate vegetation biomass, leaf area index (LAI), plant water use and stress, chlorophyll content, just to name a few. In this study, four high-resolution imageries captured by the Utah State University - AggieAir Unmanned Aerial Vehicle (UAV) system flown in 2014, 2015, and 2016 over a commercial vineyard located in the California for the USDA-Agricultural Research Service Grape Remote sensing Atmospheric Profile and Evapotranspiration Experiment (GRAPEX) Program are used for shadow detection and restoration. Four different methods for shadow detection are compared: (1) unsupervised classification, (2) supervised classification, (3) index-based method, and (4) physically-based method. Also, two different shadow restoration methods are evaluated: (1) linear correlation correction, and (2) gamma correction. The models' performance is evaluated over two vegetation indices: normalized difference vegetation index (NDVI) and LAI for both sunlit and shadowed pixels. Histogram and analysis of variance (ANOVA) are used as performance indicators. Results indicated that the performance of the supervised classification and the index-based method are better than other methods. In addition, there is a statistical difference between the average of NDVI and LAI on the sunlit and shadowed pixels. Among the shadow restoration methods, gamma correction visually works better than the linear correlation correction. Moreover, the statistical difference between sunlit and shadowed NDVI and LAI decreases after the application of the gamma restoration method. Potential effects of shadows on modeling surface energy balance and evapotranspiration using very high resolution UAV imagery over the GRAPEX vineyard will be discussed.

Prospects for phenological monitoring in an arid southwestern U.S. rangeland using field observations with hyperspatial and moderate resolution imagery

NASA Astrophysics Data System (ADS)

Browning, D. M.; Laliberte, A. S.; Rango, A.; Herrick, J. E.

2009-12-01

Relating field observations of plant phenological events to remotely sensed depictions of land surface phenology remains a challenge to the vertical integration of data from disparate sources. This research conducted at the Jornada Basin Long-Term Ecological Research site in southern New Mexico capitalizes on legacy datasets pertaining to reproductive phenology and biomass and hyperspatial imagery. Large amounts of exposed bare soil and modest cover from shrubs and grasses in these arid and semi-arid ecosystems challenge the integration of field observations of phenology and remotely sensed data to monitor changes in land surface phenology. Drawing on established field protocols for reproductive phenology, hyperspatial imagery (4 cm), and object-based image analysis, we explore the utility of two approaches to scale detailed observations (i.e., field and 4 cm imagery) to the extent of long-term field plots (50 x 50m) and moderate resolution Landsat Thematic Mapper (TM) imagery (30 x 30m). Very high resolution color-infrared imagery was collected June 2007 across 15 LTER study sites that transect five distinct vegetation communities along a continuum of grass to shrub dominance. We examined two methods for scaling spectral vegetation indices (SVI) at 4 cm resolution: pixel averaging and object-based integration. Pixel averaging yields the mean SVI value for all pixels within the plot or TM pixel. Alternatively, the object-based method is based on a weighted average of SVI values that correspond to discrete image objects (e.g., individual shrubs or grass patches). Object-based image analysis of 4 cm imagery provides a detailed depiction of ground cover and allows us to extract species-specific contributions to upscaled SVI values. The ability to discern species- or functional-group contributions to remotely sensed signals of vegetation greenness can greatly enhance the design of field sampling protocols for phenological research. Furthermore, imagery from unmanned aerial vehicles (UAV) is a cost-effective and increasingly available resource and generation of UAV mosaics has been accomplished so that larger study areas can be addressed. This technology can provide a robust basis for scaling relationships for phenology-based research applications.

Spatially Resolving Ocean Color and Sediment Dispersion in River Plumes, Coastal Systems, and Continental Shelf Waters

NASA Technical Reports Server (NTRS)

Aurin, Dirk Alexander; Mannino, Antonio; Franz, Bryan

2013-01-01

Satellite remote sensing of ocean color in dynamic coastal, inland, and nearshorewaters is impeded by high variability in optical constituents, demands specialized atmospheric correction, and is limited by instrument sensitivity. To accurately detect dispersion of bio-optical properties, remote sensors require ample signal-to-noise ratio (SNR) to sense small variations in ocean color without saturating over bright pixels, an atmospheric correction that can accommodate significantwater-leaving radiance in the near infrared (NIR), and spatial and temporal resolution that coincides with the scales of variability in the environment. Several current and historic space-borne sensors have met these requirements with success in the open ocean, but are not optimized for highly red-reflective and heterogeneous waters such as those found near river outflows or in the presence of sediment resuspension. Here we apply analytical approaches for determining optimal spatial resolution, dominant spatial scales of variability ("patches"), and proportions of patch variability that can be resolved from four river plumes around the world between 2008 and 2011. An offshore region in the Sargasso Sea is analyzed for comparison. A method is presented for processing Moderate Resolution Imaging Spectroradiometer (MODIS) Aqua and Terra imagery including cloud detection, stray lightmasking, faulty detector avoidance, and dynamic aerosol correction using short-wave- and near-infrared wavebands in extremely turbid regions which pose distinct optical and technical challenges. Results showthat a pixel size of approx. 520 mor smaller is generally required to resolve spatial heterogeneity in ocean color and total suspended materials in river plumes. Optimal pixel size increases with distance from shore to approx. 630 m in nearshore regions, approx 750 m on the continental shelf, and approx. 1350 m in the open ocean. Greater than 90% of the optical variability within plume regions is resolvable with 500 m resolution, and small, but significant, differences were found between peak and nadir river flow periods in terms of optimal resolution and resolvable proportion of variability.

a New Object-Based Framework to Detect Shodows in High-Resolution Satellite Imagery Over Urban Areas

NASA Astrophysics Data System (ADS)

Tatar, N.; Saadatseresht, M.; Arefi, H.; Hadavand, A.

2015-12-01

In this paper a new object-based framework to detect shadow areas in high resolution satellite images is proposed. To produce shadow map in pixel level state of the art supervised machine learning algorithms are employed. Automatic ground truth generation based on Otsu thresholding on shadow and non-shadow indices is used to train the classifiers. It is followed by segmenting the image scene and create image objects. To detect shadow objects, a majority voting on pixel-based shadow detection result is designed. GeoEye-1 multi-spectral image over an urban area in Qom city of Iran is used in the experiments. Results shows the superiority of our proposed method over traditional pixel-based, visually and quantitatively.

View of Callisto at Increasing Resolutions

NASA Technical Reports Server (NTRS)

1998-01-01

These four views of Jupiter's second largest moon, Callisto, highlight how increasing resolutions enable interpretation of the surface. In the global view (top left) the surface is seen to have many small bright spots, while the regional view (top right) reveals the spots to be the larger craters. The local view (bottom right) not only brings out smaller craters and detailed structure of larger craters, but also shows a smooth dark layer of material that appears to cover much of the surface. The close-up frame (bottom left) presents a surprising smoothness in this highest resolution (30 meters per picture element) view of Callisto's surface.

North is to the top of these frames which were taken by the Solid State Imaging (SSI) system on NASA's Galileo spacecraft between November 1996 and November 1997. Even higher resolution images (better than 20 meters per picture element) of Callisto will be taken on June 30, 1999 during the 21st orbit of the spacecraft around Jupiter.

The top left frame is scaled to 10 kilometers (km) per picture element (pixel) and covers an area about 4400 by 2500 km. The moon Callisto, which has a diameter of 4806 km, appears to be peppered with many bright spots. Images at this resolution of other cratered moons in the Solar System indicate that the bright spots could be impact craters. The ring structure of Valhalla, the largest impact structure on Callisto, is visible in the center of the frame. This color view combines images obtained in November 1997 taken through the green, violet, and 1 micrometer filters of the SSI system.

The top right frame is ten times higher resolution (about 1 km per pixel) and covers an area approximately 440 by 250 km. Craters, which are clearly recognizable, appear to be the dominant landform on Callisto. The crater rims appear bright, while the adjacent area and the crater interiors are dark. This resolution is comparable to the best data available from the 1979 flyby's of NASA's two Voyager spacecraft; it reflects the understanding of Callisto prior to new data from Galileo. This Galileo image was taken in November 1996.

The resolution of the bottom right image is again ten times better (100 meters per pixel) and covering an area of about 44 by 25 km. This resolution reveals that some crater rims are not complete rings, but are composed of bright isolated segments. Steep slopes near crater rims reveal dark material that appears to have slid down to reveal bright material. The thickness of the dark layer could be tens of meters. The image was taken in June 1997.

The bottom left image at about 29 meters per pixel is the highest resolution available for Callisto. It covers an area about 4.4 by 2.5 km and is somewhat oblique. Craters are visible but no longer dominate the surface. The image was taken in November 1996.

The Jet Propulsion Laboratory, Pasadena, CA manages the Galileo mission for NASA's Office of Space Science, Washington, DC. JPL is an operating division of California Institute of Technology (Caltech).

This image and other images and data received from Galileo are posted on the World Wide Web, on the Galileo mission home page at URL http://galileo.jpl.nasa.gov. Background information and educational context for the images can be found at URL http://www.jpl.nasa.gov/galileo/sepo

DOE Office of Scientific and Technical Information (OSTI.GOV)

Barbosa, F.; Somov, A. S.; Somov, S. V.

Here, silicon photomultipliers (SiPMs) are used in detectors of the GlueX experiment devoted to studying the nature of confinement. These detectors are operable at counting rates as high as 2 MHz with a time resolution (FWHM) of approximately 0.3 ns and a number of excited pixels of up to 10 4. For SiPMs that operate under these conditions, the measured dependences of the recovery time and the time resolution are presented as functions of the number of excited pixels and the excitation frequency. Using a picosecond laser, the time resolution has been measured for an array of 4 × 4more » SiPMs, which was specially developed for the experiment.« less

Operational characteristics of Wedge and Strip image readout systems

NASA Technical Reports Server (NTRS)

Siegmund, O. H. W.; Lampton, M.; Bixler, J.; Bowyer, S.; Malina, R. F.

1986-01-01

Application of the Wedge and Strip readout system in microchannel plate detectors for the Extreme Ultraviolet Explorer and FAUST space astronomy programs is discussed. Anode designs with high resolution (greater than 600 x 600 pixels) in imaging and spectroscopy applications have been developed. Extension of these designs to larger formats (100 mm) with higher resolution (3000 x 3000 pixels) are considered. It is shown that the resolution and imaging are highly stable, and that the flat field performance is essentially limited by photon statistics. Very high speed event response has also been achieved with output pulses having durations of less than 10 nanoseconds.

Dawn Survey Orbit Image 43

NASA Image and Video Library

2015-08-07

This image, taken by NASA's Dawn spacecraft, shows a portion of the southern hemisphere of dwarf planet Ceres from an altitude of 2,700 miles (4,400 kilometers). The image, with a resolution of 1,400 feet (410 meters) per pixel, was taken on June 25, 2015. The image was obtained on June 25, 2015 from an altitude of 2,700 miles (4,400 kilometers) above Ceres and has a resolution of 1,400 feet (410 meters) per pixel. http://photojournal.jpl.nasa.gov/catalog/PIA19616

Automated, per pixel Cloud Detection from High-Resolution VNIR Data

NASA Technical Reports Server (NTRS)

Varlyguin, Dmitry L.

2007-01-01

CASA is a fully automated software program for the per-pixel detection of clouds and cloud shadows from medium- (e.g., Landsat, SPOT, AWiFS) and high- (e.g., IKONOS, QuickBird, OrbView) resolution imagery without the use of thermal data. CASA is an object-based feature extraction program which utilizes a complex combination of spectral, spatial, and contextual information available in the imagery and the hierarchical self-learning logic for accurate detection of clouds and their shadows.

Forest Biomass Mapping from Stereo Imagery and Radar Data

NASA Astrophysics Data System (ADS)

Sun, G.; Ni, W.; Zhang, Z.

2013-12-01

Both InSAR and lidar data provide critical information on forest vertical structure, which are critical for regional mapping of biomass. However, the regional application of these data is limited by the availability and acquisition costs. Some researchers have demonstrated potentials of stereo imagery in the estimation of forest height. Most of these researches were conducted on aerial images or spaceborne images with very high resolutions (~0.5m). Space-born stereo imagers with global coverage such as ALOS/PRISM have coarser spatial resolutions (2-3m) to achieve wider swath. The features of stereo images are directly affected by resolutions and the approaches use by most of researchers need to be adjusted for stereo imagery with lower resolutions. This study concentrated on analyzing the features of point clouds synthesized from multi-view stereo imagery over forested areas. The small footprint lidar and lidar waveform data were used as references. The triplets of ALOS/PRISM data form three pairs (forward/nadir, backward/nadir and forward/backward) of stereo images. Each pair of the stereo images can be used to generate points (pixels) with 3D coordinates. By carefully co-register these points from three pairs of stereo images, a point cloud data was generated. The height of each point above ground surface was then calculated using DEM from National Elevation Dataset, USGS as the ground surface elevation. The height data were gridded into pixel of different sizes and the histograms of the points within a pixel were analyzed. The average height of the points within a pixel was used as the height of the pixel to generate a canopy height map. The results showed that the synergy of point clouds from different views were necessary, which increased the point density so the point cloud could detect the vertical structure of sparse and unclosed forests. The top layer of multi-layered forest could be captured but the dense forest prevented the stereo imagery to see through. The canopy height map exhibited spatial patterns of roads, forest edges and patches. The linear regression showed that the canopy height map had a good correlation with RH50 of LVIS data at 30m pixel size with a gain of 1.04, bias of 4.3m and R2 of 0.74 (Fig. 1). The canopy height map from PRISM and dual-pol PALSAR data were used together to map biomass in our study area near Howland, Maine, and the results were evaluated using biomass map generated from LVIS waveform data independently. The results showed that adding CHM from PRISM significantly improved biomass accuracy and raised the biomass saturation level of L-band SAR data in forest biomass mapping.

Full-Frame Reference for Test Photo of Moon

NASA Technical Reports Server (NTRS)

2005-01-01

This pair of views shows how little of the full image frame was taken up by the Moon in test images taken Sept. 8, 2005, by the High Resolution Imaging Science Experiment (HiRISE) camera on NASA's Mars Reconnaissance Orbiter. The Mars-bound camera imaged Earth's Moon from a distance of about 10 million kilometers (6 million miles) away -- 26 times the distance between Earth and the Moon -- as part of an activity to test and calibrate the camera. The images are very significant because they show that the Mars Reconnaissance Orbiter spacecraft and this camera can properly operate together to collect very high-resolution images of Mars. The target must move through the camera's telescope view in just the right direction and speed to acquire a proper image. The day's test images also demonstrate that the focus mechanism works properly with the telescope to produce sharp images.

Out of the 20,000-pixel-by-6,000-pixel full frame, the Moon's diameter is about 340 pixels, if the full Moon could be seen. The illuminated crescent is about 60 pixels wide, and the resolution is about 10 kilometers (6 miles) per pixel. At Mars, the entire image region will be filled with high-resolution information.

The Mars Reconnaissance Orbiter, launched on Aug. 12, 2005, is on course to reach Mars on March 10, 2006. After gradually adjusting the shape of its orbit for half a year, it will begin its primary science phase in November 2006. From the mission's planned science orbit about 300 kilometers (186 miles) above the surface of Mars, the high resolution camera will be able to discern features as small as one meter or yard across.

The Mars Reconnaissance Orbiter mission is managed by NASA's Jet Propulsion Laboratory, a division of the California Institute of Technology, Pasadena, for the NASA Science Mission Directorate. Lockheed Martin Space Systems, Denver, prime contractor for the project, built the spacecraft. Ball Aerospace & Technologies Corp., Boulder, Colo., built the High Resolution Imaging Science Experiment instrument for the University of Arizona, Tucson, to provide to the mission. The HiRISE Operations Center at the University of Arizona processes images from the camera.

Coregistration of high-resolution Mars orbital images

NASA Astrophysics Data System (ADS)

Sidiropoulos, Panagiotis; Muller, Jan-Peter

2015-04-01

The systematic orbital imaging of the Martian surface started 4 decades ago from NASA's Viking Orbiter 1 & 2 missions, which were launched in August 1975, and acquired orbital images of the planet between 1976 and 1980. The result of this reconnaissance was the first medium-resolution (i.e. ≤ 300m/pixel) global map of Mars, as well as a variety of high-resolution images (reaching up to 8m/pixel) of special regions of interest. Over the last two decades NASA has sent 3 more spacecraft with onboard instruments for high-resolution orbital imaging: Mars Global Surveyor (MGS) having onboard the Mars Orbital Camera - Narrow Angle (MOC-NA), Mars Odyssey having onboard the Thermal Emission Imaging System - Visual (THEMIS-VIS) and the Mars Reconnaissance Orbiter (MRO) having on board two distinct high-resolution cameras, Context Camera (CTX) and High-Resolution Imaging Science Experiment (HiRISE). Moreover, ESA has the multispectral High resolution Stereo Camera (HRSC) onboard ESA's Mars Express with resolution up to 12.5m since 2004. Overall, this set of cameras have acquired more than 400,000 high-resolution images, i.e. with resolution better than 100m and as fine as 25 cm/pixel. Notwithstanding the high spatial resolution of the available NASA orbital products, their accuracy of areo-referencing is often very poor. As a matter of fact, due to pointing inconsistencies, usually form errors in roll attitude, the acquired products may actually image areas tens of kilometers far away from the point that they are supposed to be looking at. On the other hand, since 2004, the ESA Mars Express has been acquiring stereo images through the High Resolution Stereo Camera (HRSC), with resolution that is usually 12.5-25 metres per pixel. The achieved coverage is more than 64% for images with resolution finer than 20 m/pixel, while for ~40% of Mars, Digital Terrain Models (DTMs) have been produced with are co-registered with MOLA [Gwinner et al., 2010]. The HRSC images and DTMs represent the best available 3D reference frame for Mars showing co-registration with MOLA<25m (loc.cit.). In our work, the reference generated by HRSC terrain corrected orthorectified images is used as a common reference frame to co-register all available high-resolution orbital NASA products into a common 3D coordinate system, thus allowing the examination of the changes that happen on the surface of Mars over time (such as seasonal flows [McEwen et al., 2011] or new impact craters [Byrne, et al., 2009]). In order to accomplish such a tedious manual task, we have developed an automatic co-registration pipeline that produces orthorectified versions of the NASA images in realistic time (i.e. from ~15 minutes to 10 hours per image depending on size). In the first step of this pipeline, tie-points are extracted from the target NASA image and the reference HRSC image or image mosaic. Subsequently, the HRSC areo-reference information is used to transform the HRSC tie-points pixel coordinates into 3D "world" coordinates. This way, a correspondence between the pixel coordinates of the target NASA image and the 3D "world" coordinates is established for each tie-point. This set of correspondences is used to estimate a non-rigid, 3D to 2D transformation model, which transforms the target image into the HRSC reference coordinate system. Finally, correlation of the transformed target image and the HRSC image is employed to fine-tune the orthorectification results, thus generating results with sub-pixel accuracy. This method, which has been proven to be accurate, robust to resolution differences and reliable when dealing with partially degraded data and fast, will be presented, along with some example co-registration results that have been achieved by using it. Acknowledgements: The research leading to these results has received partial funding from the STFC "MSSL Consolidated Grant" ST/K000977/1 and partial support from the European Union's Seventh Framework Programme (FP7/2007-2013) under iMars grant agreement n° 607379. References: [1] K. F. Gwinner, et al. (2010) Topography of Mars from global mapping by HRSC high-resolution digital terrain models and orthoimages: characteristics and performance. Earth and Planetary Science Letters 294, 506-519, doi:10.1016/j.epsl.2009.11.007. [2] A. McEwen, et al. (2011) Seasonal flows on warm martian slopes. Science , 333 (6043): 740-743. [3] S. Byrne, et al. (2009) Distribution of mid-latitude ground ice on mars from new impact craters. Science, 325(5948):1674-1676.

High resolution CsI(Tl)/Si-PIN detector development for breast imaging

DOE Office of Scientific and Technical Information (OSTI.GOV)

Patt, B.E.; Iwanczyk, J.S.; Tull, C.R.

High resolution multi-element (8x8) imaging arrays with collimators, size matched to discrete CsI(Tl) scintillator arrays and Si-PIN photodetector arrays (PDA`s) were developed as prototypes for larger arrays for breast imaging. Photodetector pixels were each 1.5 {times} 1.5 mm{sup 2} with 0.25 mm gaps. A 16-element quadrant of the detector was evaluated with a segmented CsI(Tl) scintillator array coupled to the silicon array. The scintillator thickness of 6 mm corresponds to >85% total gamma efficiency at 140 keV. Pixel energy resolution of <8% FWHM was obtained for Tc-99m. Electronic noise was 41 e{sup {minus}} RMS corresponding to a 3% FWHM contributionmore » to the 140 keV photopeak. Detection efficiency uniformity measured with a Tc-99m flood source was 4.3% for an {approximately}10% energy photopeak window. Spatial resolution was 1.53 mm FWHM and pitch was 1.75 mm as measured from the Co-57 (122 keV) line spread function. Signal to background was 34 and contrast was 0.94. The energy resolution and spatial characteristics of the new imaging detector exceed those of other scintillator based imaging detectors. A camera based on this technology will allow: (1) Improved Compton scatter rejection; (2) Detector positioning in close proximity to the breast to increase signal to noise; (3) Improved spatial resolution; and (4) Improved efficiency compared to high resolution collimated gamma cameras for the anticipated compressed breast geometries.« less

Kilopixel X-Ray Microcalorimeter Arrays for Astrophysics: Device Performance and Uniformity

NASA Technical Reports Server (NTRS)

Eckart, M. E.; Adams, J. S.; Bailey, C. N.; Bandler, S. R.; Chervenak, F. M.

2011-01-01

We are developing kilo-pixel arrays of TES microcalorimeters to enable high-resolution X-ray imaging spectrometers for future X-ray observatories and laboratory astrophysics experiments. Our current array design was targeted as a prototype for the X-ray Microcalorimeter Spectrometer proposed for the International X-ray Observatory, which calls for a 40x40-pixel core array of 300 micron devices with 2.5 e V energy resolution (at 6 keV). Here we present device characterization of our 32x32 arrays, including X-ray spectral performance of individual pixels within the array. We present our results in light of the understanding that our Mo/Au TESs act as weak superconducting links, causing the TES critical current (Ic) and transition shape to oscillate with applied magnetic field (B). We show Ic(B) measurements and discuss the uniformity of these measurements across the array, as well as implications regarding the uniformity of device noise and response. In addition, we are working to reduce pixel-to-pixel electrical and thermal crosstalk; we present recent test results from an array that has microstrip wiring and an angle-evaporated Cu backside heatsinking layer, which provides Cu coverage on the four sidewalls of the silicon wells beneath each pixel.

Identification of trace additives in polymer materials by attenuated total reflection Fourier transform infrared mapping coupled with multivariate curve resolution

NASA Astrophysics Data System (ADS)

Li, Qian; Tang, Yongjiao; Yan, Zhiwei; Zhang, Pudun

2017-06-01

Although multivariate curve resolution (MCR) has been applied to the analysis of Fourier transform infrared (FTIR) imaging, it is still problematic to determine the number of components. The reported methods at present tend to cause the components of low concentration missed. In this paper a new idea was proposed to resolve this problem. First, MCR calculation was repeated by increasing the number of components sequentially, then each retrieved pure spectrum of as-resulted MCR component was directly compared with a real-world pixel spectrum of the local high concentration in the corresponding MCR map. One component was affirmed only if the characteristic bands of the MCR component had been included in its pixel spectrum. This idea was applied to attenuated total reflection (ATR)/FTIR mapping for identifying the trace additives in blind polymer materials and satisfactory results were acquired. The successful demonstration of this novel approach opens up new possibilities for analyzing additives in polymer materials.

Simulation study of light transport in laser-processed LYSO:Ce detectors with single-side readout

NASA Astrophysics Data System (ADS)

Bläckberg, L.; El Fakhri, G.; Sabet, H.

2017-11-01

A tightly focused pulsed laser beam can locally modify the crystal structure inside the bulk of a scintillator. The result is incorporation of so-called optical barriers with a refractive index different from that of the crystal bulk, that can be used to redirect the scintillation light and control the light spread in the detector. We here systematically study the scintillation light transport in detectors fabricated using the laser induced optical barrier technique, and objectively compare their potential performance characteristics with those of the two mainstream detector types: monolithic and mechanically pixelated arrays. Among countless optical barrier patterns, we explore barriers arranged in a pixel-like pattern extending all-the-way or half-way through a 20 mm thick LYSO:Ce crystal. We analyze the performance of the detectors coupled to MPPC arrays, in terms of light response functions, flood maps, line profiles, and light collection efficiency. Our results show that laser-processed detectors with both barrier patterns constitute a new detector category with a behavior between that of the two standard detector types. Results show that when the barrier-crystal interface is smooth, no DOI information can be obtained regardless of barrier refractive index (RI). However, with a rough barrier-crystal interface we can extract multiple levels of DOI. Lower barrier RI results in larger light confinement, leading to better transverse resolution. Furthermore we see that the laser-processed crystals have the potential to increase the light collection efficiency, which could lead to improved energy resolution and potentially better timing resolution due to higher signals. For a laser-processed detector with smooth barrier-crystal interfaces the light collection efficiency is simulated to  >42%, and for rough interfaces  >73%. The corresponding numbers for a monolithic crystal is 39% with polished surfaces, and 71% with rough surfaces, and for a mechanically pixelated array 35% with polished pixel surfaces and 59% with rough surfaces.

Simulation study of light transport in laser-processed LYSO:Ce detectors with single-side readout.

PubMed

Bläckberg, L; El Fakhri, G; Sabet, H

2017-10-19

A tightly focused pulsed laser beam can locally modify the crystal structure inside the bulk of a scintillator. The result is incorporation of so-called optical barriers with a refractive index different from that of the crystal bulk, that can be used to redirect the scintillation light and control the light spread in the detector. We here systematically study the scintillation light transport in detectors fabricated using the laser induced optical barrier technique, and objectively compare their potential performance characteristics with those of the two mainstream detector types: monolithic and mechanically pixelated arrays. Among countless optical barrier patterns, we explore barriers arranged in a pixel-like pattern extending all-the-way or half-way through a 20 mm thick LYSO:Ce crystal. We analyze the performance of the detectors coupled to MPPC arrays, in terms of light response functions, flood maps, line profiles, and light collection efficiency. Our results show that laser-processed detectors with both barrier patterns constitute a new detector category with a behavior between that of the two standard detector types. Results show that when the barrier-crystal interface is smooth, no DOI information can be obtained regardless of barrier refractive index (RI). However, with a rough barrier-crystal interface we can extract multiple levels of DOI. Lower barrier RI results in larger light confinement, leading to better transverse resolution. Furthermore we see that the laser-processed crystals have the potential to increase the light collection efficiency, which could lead to improved energy resolution and potentially better timing resolution due to higher signals. For a laser-processed detector with smooth barrier-crystal interfaces the light collection efficiency is simulated to  >42%, and for rough interfaces  >73%. The corresponding numbers for a monolithic crystal is 39% with polished surfaces, and 71% with rough surfaces, and for a mechanically pixelated array 35% with polished pixel surfaces and 59% with rough surfaces.

Multi-Resolution Analysis of LiDAR data for Characterizing a Stabilized Aeolian Landscape in South Texas

NASA Astrophysics Data System (ADS)

Barrineau, C. P.; Dobreva, I. D.; Bishop, M. P.; Houser, C.

2014-12-01

Aeolian systems are ideal natural laboratories for examining self-organization in patterned landscapes, as certain wind regimes generate certain morphologies. Topographic information and scale dependent analysis offer the opportunity to study such systems and characterize process-form relationships. A statistically based methodology for differentiating aeolian features would enable the quantitative association of certain surface characteristics with certain morphodynamic regimes. We conducted a multi-resolution analysis of LiDAR elevation data to assess scale-dependent morphometric variations in an aeolian landscape in South Texas. For each pixel, mean elevation values are calculated along concentric circles moving outward at 100-meter intervals (i.e. 500 m, 600 m, 700 m from pixel). The calculated average elevation values plotted against distance from the pixel of interest as curves are used to differentiate multi-scalar variations in elevation across the landscape. In this case, it is hypothesized these curves may be used to quantitatively differentiate certain morphometries from others like a spectral signature may be used to classify paved surfaces from natural vegetation, for example. After generating multi-resolution curves for all the pixels in a selected area of interest (AOI), a Principal Components Analysis is used to highlight commonalities and singularities between generated curves from pixels across the AOI. Our findings suggest that the resulting components could be used for identification of discrete aeolian features like open sands, trailing ridges and active dune crests, and, in particular, zones of deflation. This new approach to landscape characterization not only works to mitigate bias introduced when researchers must select training pixels for morphometric investigations, but can also reveal patterning in aeolian landscapes that would not be as obvious without quantitative characterization.

Novel laser-processed CsI:Tl detector for SPECT

PubMed Central

Sabet, H.; Bläckberg, L.; Uzun-Ozsahin, D.; El-Fakhri, G.

2016-01-01

Purpose: The aim of this work is to demonstrate the feasibility of a novel technique for fabrication of high spatial resolution CsI:Tl scintillation detectors for single photon emission computed tomography systems. Methods: The scintillators are fabricated using laser-induced optical barriers technique to create optical microstructures (or optical barriers) inside the CsI:Tl crystal bulk. The laser-processed CsI:Tl crystals are 3, 5, and 10 mm in thickness. In this work, the authors focus on the simplest pattern of optical barriers in that the barriers are created in the crystal bulk to form pixel-like patterns resembling mechanically pixelated scintillators. The monolithic CsI:Tl scintillator samples are fabricated with optical barrier patterns with 1.0 × 1.0 mm2 and 0.625 × 0.625 mm2 pixels. Experiments were conducted to characterize the fabricated arrays in terms of pixel separation and energy resolution. A 4 × 4 array of multipixel photon counter was used to collect the scintillation light in all the experiments. Results: The process yield for fabricating the CsI:Tl arrays is 100% with processing time under 50 min. From the flood maps of the fabricated detectors exposed to 122 keV gammas, peak-to-valley (P/V) ratios of greater than 2.3 are calculated. The P/V values suggest that regardless of the crystal thickness, the pixels can be resolved. Conclusions: The results suggest that optical barriers can be considered as a robust alternative to mechanically pixelated arrays and can provide high spatial resolution while maintaining the sensitivity in a high-throughput and cost-effective manner. PMID:27147372

The fundamentals of average local variance--Part II: Sampling simple regular patterns with optical imagery.

PubMed

Bøcher, Peder Klith; McCloy, Keith R

2006-02-01

In this investigation, the characteristics of the average local variance (ALV) function is investigated through the acquisition of images at different spatial resolutions of constructed scenes of regular patterns of black and white squares. It is shown that the ALV plot consistently peaks at a spatial resolution in which the pixels has a size corresponding to half the distance between scene objects, and that, under very specific conditions, it also peaks at a spatial resolution in which the pixel size corresponds to the whole distance between scene objects. It is argued that the peak at object distance when present is an expression of the Nyquist sample rate. The presence of this peak is, hence, shown to be a function of the matching between the phase of the scene pattern and the phase of the sample grid, i.e., the image. When these phases match, a clear and distinct peak is produced on the ALV plot. The fact that the peak at half the distance consistently occurs in the ALV plot is linked to the circumstance that the sampling interval (distance between pixels) and the extent of the sampling unit (size of pixels) are equal. Hence, at twice the Nyquist sampling rate, each fundamental period of the pattern is covered by four pixels; therefore, at least one pixel is always completely embedded within one pattern element, regardless of sample scene phase. If the objects in the scene are scattered with a distance larger than their extent, the peak will be related to the size by a factor larger than 1/2. This is suggested to be the explanation to the results presented by others that the ALV plot is related to scene-object size by a factor of 1/2-3/4.

Indium antimonide large-format detector arrays

NASA Astrophysics Data System (ADS)

Davis, Mike; Greiner, Mark

2011-06-01

Large format infrared imaging sensors are required to achieve simultaneously high resolution and wide field of view image data. Infrared sensors are generally required to be cooled from room temperature to cryogenic temperatures in less than 10 min thousands of times during their lifetime. The challenge is to remove mechanical stress, which is due to different materials with different coefficients of expansion, over a very wide temperature range and at the same time, provide a high sensitivity and high resolution image data. These challenges are met by developing a hybrid where the indium antimonide detector elements (pixels) are unconnected islands that essentially float on a silicon substrate and form a near perfect match to the silicon read-out circuit. Since the pixels are unconnected and isolated from each other, the array is reticulated. This paper shows that the front side illuminated and reticulated element indium antimonide focal plane developed at L-3 Cincinnati Electronics are robust, approach background limited sensitivity limit, and provide the resolution expected of the reticulated pixel array.

Propagation phasor approach for holographic image reconstruction

PubMed Central

Luo, Wei; Zhang, Yibo; Göröcs, Zoltán; Feizi, Alborz; Ozcan, Aydogan

2016-01-01

To achieve high-resolution and wide field-of-view, digital holographic imaging techniques need to tackle two major challenges: phase recovery and spatial undersampling. Previously, these challenges were separately addressed using phase retrieval and pixel super-resolution algorithms, which utilize the diversity of different imaging parameters. Although existing holographic imaging methods can achieve large space-bandwidth-products by performing pixel super-resolution and phase retrieval sequentially, they require large amounts of data, which might be a limitation in high-speed or cost-effective imaging applications. Here we report a propagation phasor approach, which for the first time combines phase retrieval and pixel super-resolution into a unified mathematical framework and enables the synthesis of new holographic image reconstruction methods with significantly improved data efficiency. In this approach, twin image and spatial aliasing signals, along with other digital artifacts, are interpreted as noise terms that are modulated by phasors that analytically depend on the lateral displacement between hologram and sensor planes, sample-to-sensor distance, wavelength, and the illumination angle. Compared to previous holographic reconstruction techniques, this new framework results in five- to seven-fold reduced number of raw measurements, while still achieving a competitive resolution and space-bandwidth-product. We also demonstrated the success of this approach by imaging biological specimens including Papanicolaou and blood smears. PMID:26964671

The HEXITEC Hard X-Ray Pixelated CdTe Imager for Fast Solar Observations

NASA Technical Reports Server (NTRS)

Baumgartner, Wayne H.; Christe, Steven D.; Ryan, Daniel; Inglis, Andrew R.; Shih, Albert Y.; Gregory, Kyle; Wilson, Matt; Seller, Paul; Gaskin, Jessica; Wilson-Hodge, Colleen

2016-01-01

There is an increasing demand in solar and astrophysics for high resolution X-ray spectroscopic imaging. Such observations would present ground breaking opportunities to study the poorly understood high energy processes in our solar system and beyond, such as solar flares, X-ray binaries, and active galactic nuclei. However, such observations require a new breed of solid state detectors sensitive to high energy X-rays with fine independent pixels to sub-sample the point spread function (PSF) of the X-ray optics. For solar observations in particular, they must also be capable of handling very high count rates as photon fluxes from solar flares often cause pile up and saturation in present generation detectors. The Rutherford Appleton Laboratory (RAL) has recently developed a new cadmium telluride (CdTe) detector system, called HEXITEC (High Energy X-ray Imaging Technology). It is an 80 x 80 array of 250 micron independent pixels sensitive in the 2-200 keV band and capable of a high full frame read out rate of 10 kHz. HEXITEC provides the smallest independently read out CdTe pixels currently available, and are well matched to the few arcsecond PSF produced by current and next generation hard X-ray focusing optics. NASA's Goddard and Marshall Space Flight Centers are collaborating with RAL to develop these detectors for use on future space borne hard X-ray focusing telescopes. We show the latest results on HEXITEC's imaging capability, energy resolution, high read out rate, and reveal it to be ideal for such future instruments.

Photon event distribution sampling: an image formation technique for scanning microscopes that permits tracking of sub-diffraction particles with high spatial and temporal resolutions.

PubMed

Larkin, J D; Publicover, N G; Sutko, J L

2011-01-01

In photon event distribution sampling, an image formation technique for scanning microscopes, the maximum likelihood position of origin of each detected photon is acquired as a data set rather than binning photons in pixels. Subsequently, an intensity-related probability density function describing the uncertainty associated with the photon position measurement is applied to each position and individual photon intensity distributions are summed to form an image. Compared to pixel-based images, photon event distribution sampling images exhibit increased signal-to-noise and comparable spatial resolution. Photon event distribution sampling is superior to pixel-based image formation in recognizing the presence of structured (non-random) photon distributions at low photon counts and permits use of non-raster scanning patterns. A photon event distribution sampling based method for localizing single particles derived from a multi-variate normal distribution is more precise than statistical (Gaussian) fitting to pixel-based images. Using the multi-variate normal distribution method, non-raster scanning and a typical confocal microscope, localizations with 8 nm precision were achieved at 10 ms sampling rates with acquisition of ~200 photons per frame. Single nanometre precision was obtained with a greater number of photons per frame. In summary, photon event distribution sampling provides an efficient way to form images when low numbers of photons are involved and permits particle tracking with confocal point-scanning microscopes with nanometre precision deep within specimens. © 2010 The Authors Journal of Microscopy © 2010 The Royal Microscopical Society.

Three-dimensional cascaded system analysis of a 50 µm pixel pitch wafer-scale CMOS active pixel sensor x-ray detector for digital breast tomosynthesis.

PubMed

Zhao, C; Vassiljev, N; Konstantinidis, A C; Speller, R D; Kanicki, J

2017-03-07

High-resolution, low-noise x-ray detectors based on the complementary metal-oxide-semiconductor (CMOS) active pixel sensor (APS) technology have been developed and proposed for digital breast tomosynthesis (DBT). In this study, we evaluated the three-dimensional (3D) imaging performance of a 50 µm pixel pitch CMOS APS x-ray detector named DynAMITe (Dynamic Range Adjustable for Medical Imaging Technology). The two-dimensional (2D) angle-dependent modulation transfer function (MTF), normalized noise power spectrum (NNPS), and detective quantum efficiency (DQE) were experimentally characterized and modeled using the cascaded system analysis at oblique incident angles up to 30°. The cascaded system model was extended to the 3D spatial frequency space in combination with the filtered back-projection (FBP) reconstruction method to calculate the 3D and in-plane MTF, NNPS and DQE parameters. The results demonstrate that the beam obliquity blurs the 2D MTF and DQE in the high spatial frequency range. However, this effect can be eliminated after FBP image reconstruction. In addition, impacts of the image acquisition geometry and detector parameters were evaluated using the 3D cascaded system analysis for DBT. The result shows that a wider projection angle range (e.g.  ±30°) improves the low spatial frequency (below 5 mm -1 ) performance of the CMOS APS detector. In addition, to maintain a high spatial resolution for DBT, a focal spot size of smaller than 0.3 mm should be used. Theoretical analysis suggests that a pixelated scintillator in combination with the 50 µm pixel pitch CMOS APS detector could further improve the 3D image resolution. Finally, the 3D imaging performance of the CMOS APS and an indirect amorphous silicon (a-Si:H) thin-film transistor (TFT) passive pixel sensor (PPS) detector was simulated and compared.

Three-dimensional cascaded system analysis of a 50 µm pixel pitch wafer-scale CMOS active pixel sensor x-ray detector for digital breast tomosynthesis

NASA Astrophysics Data System (ADS)

Zhao, C.; Vassiljev, N.; Konstantinidis, A. C.; Speller, R. D.; Kanicki, J.

2017-03-01

High-resolution, low-noise x-ray detectors based on the complementary metal-oxide-semiconductor (CMOS) active pixel sensor (APS) technology have been developed and proposed for digital breast tomosynthesis (DBT). In this study, we evaluated the three-dimensional (3D) imaging performance of a 50 µm pixel pitch CMOS APS x-ray detector named DynAMITe (Dynamic Range Adjustable for Medical Imaging Technology). The two-dimensional (2D) angle-dependent modulation transfer function (MTF), normalized noise power spectrum (NNPS), and detective quantum efficiency (DQE) were experimentally characterized and modeled using the cascaded system analysis at oblique incident angles up to 30°. The cascaded system model was extended to the 3D spatial frequency space in combination with the filtered back-projection (FBP) reconstruction method to calculate the 3D and in-plane MTF, NNPS and DQE parameters. The results demonstrate that the beam obliquity blurs the 2D MTF and DQE in the high spatial frequency range. However, this effect can be eliminated after FBP image reconstruction. In addition, impacts of the image acquisition geometry and detector parameters were evaluated using the 3D cascaded system analysis for DBT. The result shows that a wider projection angle range (e.g.  ±30°) improves the low spatial frequency (below 5 mm-1) performance of the CMOS APS detector. In addition, to maintain a high spatial resolution for DBT, a focal spot size of smaller than 0.3 mm should be used. Theoretical analysis suggests that a pixelated scintillator in combination with the 50 µm pixel pitch CMOS APS detector could further improve the 3D image resolution. Finally, the 3D imaging performance of the CMOS APS and an indirect amorphous silicon (a-Si:H) thin-film transistor (TFT) passive pixel sensor (PPS) detector was simulated and compared.

Sci-Sat AM(1): Imaging-08: Small animal APD PET detector with submillimetric resolution for molecular imaging.

PubMed

Bérard, P; Bergeron, M; Pepin, C M; Cadorette, J; Tétrault, M-A; Viscogliosi, N; Fontaine, R; Dautet, H; Davies, M; Lecomte, R

2008-07-01

Visualization and quantification of biological processes in mice, the preferred animal model in most preclinical studies, require the best possible spatial resolution in positron emission tomography (PET). A new 64-channel avalanche photodiode (APD) detector module was developed to achieve submillimeter spatial resolution for this purpose. The module consists of dual 4 × 8 APD arrays mounted in a custom ceramic holder. Individual APD pixels having an active area of 1.1 × 1.1 mm2 at a 1.2 mm pitch can be fitted to an 8 × 8 LYSO scintillator block designed to accommodate one-to-one coupling. An analog test board with four 16-channel preamplifier ASICs was designed to be interfaced with the existing LabPET digital processing electronics. At a standard APD operating bias, a mean energy resolution of 27.5 ± 0.6% was typically obtained at 511 keV with a relative standard deviation of 13.8% in signal amplitude for the 64 individual pixels. Crosstalk between pixels was found to be well below the typical lower energy threshold used for PET imaging applications. With two modules in coincidence, a global timing resolution of 5.0 ns FWHM was measured. Finally, an intrinsic spatial resolution of 0.8 mm FWHM was measured by sweeping a 22Na point source between two detector arrays. The proposed detector module demonstrates promising characteristics for dedicated mouse PET imaging at submillimiter resolution. © 2008 American Association of Physicists in Medicine.

Characterisation of crystal matrices and single pixels for nuclear medicine applications

NASA Astrophysics Data System (ADS)

Herbert, D. J.; Belcari, N.; Camarda, M.; Guerra, A. Del; Vaiano, A.

2005-01-01

Commercially constructed crystal matrices are characterised for use with PSPMT detectors for PET system developments and other nuclear medicine applications. The matrices of different scintillation materials were specified with pixel dimensions of 1.5×1.5 mm2 in cross-section and a length corresponding to one gamma ray interaction length at 511 keV. The materials used in this study were BGO, LSO, LYSO, YSO and CsI(Na). Each matrix was constructed using a white TiO loaded epoxy that forms a 0.2 mm septa between each pixel. The white epoxy is not the optimum choice in terms of the reflective properties, but represents a good compromise between cost and the need for optical isolation between pixels. We also tested a YAP matrix that consisted of pixels of the same size specification but was manufactured by a different company, who instead of white epoxy, used a thin aluminium reflective layer for optical isolation that resulted in a septal thickness of just 0.01 mm, resulting in a much higher packing fraction. The characteristics of the scintillation materials, such as the light output and energy resolution, were first studied in the form of individual crystal elements by using a single pixel HPD. A comparison of individual pixels with and without the epoxy/dielectric coatings was also performed. Then the matrices themselves were coupled to a PSPMT in order to study the imaging performance. In particular, the system pixel resolution and the peak to valley ratio were measured at 511 and 122 keV.

Characterization of the ePix100 prototype: a front-end ASIC for second-generation LCLS integrating hybrid pixel detectors

NASA Astrophysics Data System (ADS)

Caragiulo, P.; Dragone, A.; Markovic, B.; Herbst, R.; Nishimura, K.; Reese, B.; Herrmann, S.; Hart, P.; Blaj, G.; Segal, J.; Tomada, A.; Hasi, J.; Carini, G.; Kenney, C.; Haller, G.

2014-09-01

ePix100 is the first variant of a novel class of integrating pixel ASICs architectures optimized for the processing of signals in second generation LINAC Coherent Light Source (LCLS) X-Ray cameras. ePix100 is optimized for ultra-low noise application requiring high spatial resolution. ePix ASICs are based on a common platform composed of a random access analog matrix of pixel with global shutter, fast parallel column readout, and dedicated sigma-delta analog to digital converters per column. The ePix100 variant has 50μmx50μm pixels arranged in a 352x384 matrix, a resolution of 50e- r.m.s. and a signal range of 35fC (100 photons at 8keV). In its final version it will be able to sustain a frame rate of 1kHz. A first prototype has been fabricated and characterized and the measurement results are reported here.

Comparison between Pixelated Scintillators: CsI(Tl), LaCl 3(Ce) and LYSO(Ce) when coupled to a Silicon Photomultipliers Array

NASA Astrophysics Data System (ADS)

Jeong, Manhee; Van, Benjamin; Wells, Byron T.; D'Aries, Lawrence J.; Hammig, Mark D.

2018-06-01

A large area SiPM array is individually coupled to five different types of scintillators in and each is evaluated for the development of a coded aperture imaging system. In order to readout signals from the 144 pixel array, a resistor network with symmetric charge division circuitry was developed, which successfully provides a significant reduction in the multiplicity of the analog outputs and reduces the size of the accumulated data. Energy resolutions at 662 keV for pixelated arrays of dimensions and material types as follows: 3 × 3 × 20 mm3 CsI(Tl), 4 × 4 × 20 mm3 CsI(Tl), 4 × 4 × 5 mm3 LYSO(Ce), 4 × 4 × 10 mm3 LYSO(Ce), and 2 × 2 × 5 mm3 LaCl3(Ce) have been determined. In addition, sub-millimeter FWHM pixel-identification resolutions were acquired from all of the scintillators tested.

Unmixing AVHRR Imagery to Assess Clearcuts and Forest Regrowth in Oregon

NASA Technical Reports Server (NTRS)

Hlavka, Christine A.; Spanner, Michael A.

1995-01-01

Advanced Very High Resolution Radiometer imagery provides frequent and low-cost coverage of the earth, but its coarse spatial resolution (approx. 1.1 km by 1.1 km) does not lend itself to standard techniques of automated categorization of land cover classes because the pixels are generally mixed; that is, the extent of the pixel includes several land use/cover classes. Unmixing procedures were developed to extract land use/cover class signatures from mixed pixels, using Landsat Thematic Mapper data as a source for the training set, and to estimate fractions of class coverage within pixels. Application of these unmixing procedures to mapping forest clearcuts and regrowth in Oregon indicated that unmixing is a promising approach for mapping major trends in land cover with AVHRR bands 1 and 2. Including thermal bands by unmixing AVHRR bands 1-4 did not lead to significant improvements in accuracy, but experiments with unmixing these four bands did indicate that use of weighted least squares techniques might lead to improvements in other applications of unmixing.

High resolution phoswich gamma-ray imager utilizing monolithic MPPC arrays with submillimeter pixelized crystals

NASA Astrophysics Data System (ADS)

Kato, T.; Kataoka, J.; Nakamori, T.; Kishimoto, A.; Yamamoto, S.; Sato, K.; Ishikawa, Y.; Yamamura, K.; Kawabata, N.; Ikeda, H.; Kamada, K.

2013-05-01

We report the development of a high spatial resolution tweezers-type coincidence gamma-ray camera for medical imaging. This application consists of large-area monolithic Multi-Pixel Photon Counters (MPPCs) and submillimeter pixelized scintillator matrices. The MPPC array has 4 × 4 channels with a three-side buttable, very compact package. For typical operational gain of 7.5 × 105 at + 20 °C, gain fluctuation over the entire MPPC device is only ± 5.6%, and dark count rates (as measured at the 1 p.e. level) amount to <= 400 kcps per channel. We selected Ce-doped (Lu,Y)2(SiO4)O (Ce:LYSO) and a brand-new scintillator, Ce-doped Gd3Al2Ga3O12 (Ce:GAGG) due to their high light yield and density. To improve the spatial resolution, these scintillators were fabricated into 15 × 15 matrices of 0.5 × 0.5 mm2 pixels. The Ce:LYSO and Ce:GAGG scintillator matrices were assembled into phosphor sandwich (phoswich) detectors, and then coupled to the MPPC array along with an acrylic light guide measuring 1 mm thick, and with summing operational amplifiers that compile the signals into four position-encoded analog outputs being used for signal readout. Spatial resolution of 1.1 mm was achieved with the coincidence imaging system using a 22Na point source. These results suggest that the gamma-ray imagers offer excellent potential for applications in high spatial medical imaging.

Near-infrared fluorescence imaging with a mobile phone (Conference Presentation)

NASA Astrophysics Data System (ADS)

Ghassemi, Pejhman; Wang, Bohan; Wang, Jianting; Wang, Quanzeng; Chen, Yu; Pfefer, T. Joshua

2017-03-01

Mobile phone cameras employ sensors with near-infrared (NIR) sensitivity, yet this capability has not been exploited for biomedical purposes. Removing the IR-blocking filter from a phone-based camera opens the door to a wide range of techniques and applications for inexpensive, point-of-care biophotonic imaging and sensing. This study provides proof of principle for one of these modalities - phone-based NIR fluorescence imaging. An imaging system was assembled using a 780 nm light source along with excitation and emission filters with 800 nm and 825 nm cut-off wavelengths, respectively. Indocyanine green (ICG) was used as an NIR fluorescence contrast agent in an ex vivo rodent model, a resolution test target and a 3D-printed, tissue-simulating vascular phantom. Raw and processed images for red, green and blue pixel channels were analyzed for quantitative evaluation of fundamental performance characteristics including spectral sensitivity, detection linearity and spatial resolution. Mobile phone results were compared with a scientific CCD. The spatial resolution of CCD system was consistently superior to the phone, and green phone camera pixels showed better resolution than blue or green channels. The CCD exhibited similar sensitivity as processed red and blue pixels channels, yet a greater degree of detection linearity. Raw phone pixel data showed lower sensitivity but greater linearity than processed data. Overall, both qualitative and quantitative results provided strong evidence of the potential of phone-based NIR imaging, which may lead to a wide range of applications from cancer detection to glucose sensing.

Study of a high-resolution PET system using a Silicon detector probe

NASA Astrophysics Data System (ADS)

Brzeziński, K.; Oliver, J. F.; Gillam, J.; Rafecas, M.

2014-10-01

A high-resolution silicon detector probe, in coincidence with a conventional PET scanner, is expected to provide images of higher quality than those achievable using the scanner alone. Spatial resolution should improve due to the finer pixelization of the probe detector, while increased sensitivity in the probe vicinity is expected to decrease noise. A PET-probe prototype is being developed utilizing this principle. The system includes a probe consisting of ten layers of silicon detectors, each a 80 × 52 array of 1 × 1 × 1 mm3 pixels, to be operated in coincidence with a modern clinical PET scanner. Detailed simulation studies of this system have been performed to assess the effect of the additional probe information on the quality of the reconstructed images. A grid of point sources was simulated to study the contribution of the probe to the system resolution at different locations over the field of view (FOV). A resolution phantom was used to demonstrate the effect on image resolution for two probe positions. A homogeneous source distribution with hot and cold regions was used to demonstrate that the localized improvement in resolution does not come at the expense of the overall quality of the image. Since the improvement is constrained to an area close to the probe, breast imaging is proposed as a potential application for the novel geometry. In this sense, a simplified breast phantom, adjacent to heart and torso compartments, was simulated and the effect of the probe on lesion detectability, through measurements of the local contrast recovery coefficient-to-noise ratio (CNR), was observed. The list-mode ML-EM algorithm was used for image reconstruction in all cases. As expected, the point spread function of the PET-probe system was found to be non-isotropic and vary with position, offering improvement in specific regions. Increase in resolution, of factors of up to 2, was observed in the region close to the probe. Images of the resolution phantom showed visible improvement in resolution when including the probe in the simulations. The image quality study demonstrated that contrast and spill-over ratio in other areas of the FOV were not sacrificed for this enhancement. The CNR study performed on the breast phantom indicates increased lesion detectability provided by the probe.

Experimental evaluation of the resolution improvement provided by a silicon PET probe.

PubMed

Brzeziński, K; Oliver, J F; Gillam, J; Rafecas, M; Studen, A; Grkovski, M; Kagan, H; Smith, S; Llosá, G; Lacasta, C; Clinthorne, N H

2016-09-01

A high-resolution PET system, which incorporates a silicon detector probe into a conventional PET scanner, has been proposed to obtain increased image quality in a limited region of interest. Detailed simulation studies have previously shown that the additional probe information improves the spatial resolution of the reconstructed image and increases lesion detectability, with no cost to other image quality measures. The current study expands on the previous work by using a laboratory prototype of the silicon PET-probe system to examine the resolution improvement in an experimental setting. Two different versions of the probe prototype were assessed, both consisting of a back-to-back pair of 1-mm thick silicon pad detectors, one arranged in 32 × 16 arrays of 1.4 mm × 1.4 mm pixels and the other in 40 × 26 arrays of 1.0 mm × 1.0 mm pixels. Each detector was read out by a set of VATAGP7 ASICs and a custom-designed data acquisition board which allowed trigger and data interfacing with the PET scanner, itself consisting of BGO block detectors segmented into 8 × 6 arrays of 6 mm × 12 mm × 30 mm crystals. Limited-angle probe data was acquired from a group of Na-22 point-like sources in order to observe the maximum resolution achievable using the probe system. Data from a Derenzo-like resolution phantom was acquired, then scaled to obtain similar statistical quality as that of previous simulation studies. In this case, images were reconstructed using measurements of the PET ring alone and with the inclusion of the probe data. Images of the Na-22 source demonstrated a resolution of 1.5 mm FWHM in the probe data, the PET ring resolution being approximately 6 mm. Profiles taken through the image of the Derenzo-like phantom showed a clear increase in spatial resolution. Improvements in peak-to-valley ratios of 50% and 38%, in the 4.8 mm and 4.0 mm phantom features respectively, were observed, while previously unresolvable 3.2 mm features were brought to light by the addition of the probe. These results support the possibility of improving the image resolution of a clinical PET scanner using the silicon PET-probe.

Impact of sensor's point spread function on land cover characterization: Assessment and deconvolution

USGS Publications Warehouse

Huang, C.; Townshend, J.R.G.; Liang, S.; Kalluri, S.N.V.; DeFries, R.S.

2002-01-01

Measured and modeled point spread functions (PSF) of sensor systems indicate that a significant portion of the recorded signal of each pixel of a satellite image originates from outside the area represented by that pixel. This hinders the ability to derive surface information from satellite images on a per-pixel basis. In this study, the impact of the PSF of the Moderate Resolution Imaging Spectroradiometer (MODIS) 250 m bands was assessed using four images representing different landscapes. Experimental results showed that though differences between pixels derived with and without PSF effects were small on the average, the PSF generally brightened dark objects and darkened bright objects. This impact of the PSF lowered the performance of a support vector machine (SVM) classifier by 5.4% in overall accuracy and increased the overall root mean square error (RMSE) by 2.4% in estimating subpixel percent land cover. An inversion method based on the known PSF model reduced the signals originating from surrounding areas by as much as 53%. This method differs from traditional PSF inversion deconvolution methods in that the PSF was adjusted with lower weighting factors for signals originating from neighboring pixels than those specified by the PSF model. By using this deconvolution method, the lost classification accuracy due to residual impact of PSF effects was reduced to only 1.66% in overall accuracy. The increase in the RMSE of estimated subpixel land cover proportions due to the residual impact of PSF effects was reduced to 0.64%. Spatial aggregation also effectively reduced the errors in estimated land cover proportion images. About 50% of the estimation errors were removed after applying the deconvolution method and aggregating derived proportion images to twice their dimensional pixel size. ?? 2002 Elsevier Science Inc. All rights reserved.

GaAs QWIP Array Containing More Than a Million Pixels

NASA Technical Reports Server (NTRS)

Jhabvala, Murzy; Choi, K. K.; Gunapala, Sarath

2005-01-01

A 1,024 x 1,024-pixel array of quantum-well infrared photodetectors (QWIPs) has been built on a 1.8 x 1.8- cm GaAs chip. In tests, the array was found to perform well in detecting images at wavelengths from 8 to 9 m in operation at temperatures between 60 and 70 K. The largest-format QWIP prior array that performed successfully in tests contained 512 x 640 pixels. There is continuing development effort directed toward satisfying actual and anticipated demands to increase numbers of pixels and pixel sizes in order to increase the imaging resolution of infrared photodetector arrays. A 1,024 x 1,024-pixel and even larger formats have been achieved in the InSb and HgCdTe material systems, but photodetector arrays in these material systems are very expensive and manufactured by fewer than half a dozen large companies. In contrast, GaAs-photodetector-array technology is very mature, and photodetectors in the GaAs material system can be readily manufactured by a wide range of industrial technologists, by universities, and government laboratories. There is much similarity between processing in the GaAs industry and processing in the pervasive silicon industry. With respect to yield and cost, the performance of GaAs technology substantially exceeds that of InSb and HgCdTe technologies. In addition, GaAs detectors can be designed to respond to any portion of the wavelength range from 3 to about 16 micrometers - a feature that is very desirable for infrared imaging. GaAs QWIP arrays, like the present one, have potential for use as imaging sensors in infrared measuring instruments, infrared medical imaging systems, and infrared cameras.

High-resolution confocal Raman microscopy using pixel reassignment.

PubMed

Roider, Clemens; Ritsch-Marte, Monika; Jesacher, Alexander

2016-08-15

We present a practical modification of fiber-coupled confocal Raman scanning microscopes that is able to provide high confocal resolution in conjunction with high light collection efficiency. For this purpose, the single detection fiber is replaced by a hexagonal lenslet array in combination with a hexagonally packed round-to-linear multimode fiber bundle. A multiline detector is used to collect individual Raman spectra for each fiber. Data post-processing based on pixel reassignment allows one to improve the lateral resolution by up to 41% compared to a single fiber of equal light collection efficiency. We present results from an experimental implementation featuring seven collection fibers, yielding a resolution improvement of about 30%. We believe that our implementation represents an attractive upgrade for existing confocal Raman microscopes that employ multi-line detectors.

Cyclops: single-pixel imaging lidar system based on compressive sensing

NASA Astrophysics Data System (ADS)

Magalhães, F.; Correia, M. V.; Farahi, F.; Pereira do Carmo, J.; Araújo, F. M.

2017-11-01

Mars and the Moon are envisaged as major destinations of future space exploration missions in the upcoming decades. Imaging LIDARs are seen as a key enabling technology in the support of autonomous guidance, navigation and control operations, as they can provide very accurate, wide range, high-resolution distance measurements as required for the exploration missions. Imaging LIDARs can be used at critical stages of these exploration missions, such as descent and selection of safe landing sites, rendezvous and docking manoeuvres, or robotic surface navigation and exploration. Despite these devices have been commercially available and used for long in diverse metrology and ranging applications, their size, mass and power consumption are still far from being suitable and attractive for space exploratory missions. Here, we describe a compact Single-Pixel Imaging LIDAR System that is based on a compressive sensing technique. The application of the compressive codes to a DMD array enables compression of the spatial information, while the collection of timing histograms correlated to the pulsed laser source ensures image reconstruction at the ranged distances. Single-pixel cameras have been compared with raster scanning and array based counterparts in terms of noise performance, and proved to be superior. Since a single photodetector is used, a better SNR and higher reliability is expected in contrast with systems using large format photodetector arrays. Furthermore, the event of failure of one or more micromirror elements in the DMD does not prevent full reconstruction of the images. This brings additional robustness to the proposed 3D imaging LIDAR. The prototype that was implemented has three modes of operation. Range Finder: outputs the average distance between the system and the area of the target under illumination; Attitude Meter: provides the slope of the target surface based on distance measurements in three areas of the target; 3D Imager: produces 3D ranged images of the target surface. The implemented prototype demonstrated a frame rate of 30 mHz for 16x16 pixels images, a transversal (xy) resolution of 2 cm at 10 m for images with 64x64 pixels and the range (z) resolution proved to be better than 1 cm. The experimental results obtained for the "3D imaging" mode of operation demonstrated that it was possible to reconstruct spherical smooth surfaces. The proposed solution demonstrates a great potential for: miniaturization; increase spatial resolution without using large format detector arrays; eliminate the need for scanning mechanisms; implementing simple and robust configurations.

Scale Dependence of Cirrus Horizontal Heterogeneity Effects on TOA Measurements. Part I; MODIS Brightness Temperatures in the Thermal Infrared

NASA Technical Reports Server (NTRS)

Fauchez, Thomas; Platnick, Steven; Meyer, Kerry; Cornet, Celine; Szczap, Frederic; Varnai, Tamas

2017-01-01

This paper presents a study on the impact of cirrus cloud heterogeneities on MODIS simulated thermal infrared (TIR) brightness temperatures (BTs) at the top of the atmosphere (TOA) as a function of spatial resolution from 50 meters to 10 kilometers. A realistic 3-D (three-dimensional) cirrus field is generated by the 3DCLOUD model (average optical thickness of 1.4, cloudtop and base altitudes at 10 and 12 kilometers, respectively, consisting of aggregate column crystals of D (sub eff) equals 20 microns), and 3-D thermal infrared radiative transfer (RT) is simulated with the 3DMCPOL (3-D Monte Carlo Polarized) code. According to previous studies, differences between 3-D BT computed from a heterogenous pixel and 1-D (one-dimensional) RT computed from a homogeneous pixel are considered dependent at nadir on two effects: (i) the optical thickness horizontal heterogeneity leading to the plane-parallel homogeneous bias (PPHB); and the (ii) horizontal radiative transport (HRT) leading to the independent pixel approximation error (IPAE). A single but realistic cirrus case is simulated and, as expected, the PPHB mainly impacts the low-spatial resolution results (above approximately 250 meters), with averaged values of up to 5-7 K (thousand), while the IPAE mainly impacts the high-spatial resolution results (below approximately 250 meters) with average values of up to 1-2 K (thousand). A sensitivity study has been performed in order to extend these results to various cirrus optical thicknesses and heterogeneities by sampling the cirrus in several ranges of parameters. For four optical thickness classes and four optical heterogeneity classes, we have found that, for nadir observations, the spatial resolution at which the combination of PPHB and HRT effects is the smallest, falls between 100 and 250 meters. These spatial resolutions thus appear to be the best choice to retrieve cirrus optical properties with the smallest cloud heterogeneity-related total bias in the thermal infrared. For off-nadir observations, the average total effect is increased and the minimum is shifted to coarser spatial resolutions.

A robust object-based shadow detection method for cloud-free high resolution satellite images over urban areas and water bodies

NASA Astrophysics Data System (ADS)

Tatar, Nurollah; Saadatseresht, Mohammad; Arefi, Hossein; Hadavand, Ahmad

2018-06-01

Unwanted contrast in high resolution satellite images such as shadow areas directly affects the result of further processing in urban remote sensing images. Detecting and finding the precise position of shadows is critical in different remote sensing processing chains such as change detection, image classification and digital elevation model generation from stereo images. The spectral similarity between shadow areas, water bodies, and some dark asphalt roads makes the development of robust shadow detection algorithms challenging. In addition, most of the existing methods work on pixel-level and neglect the contextual information contained in neighboring pixels. In this paper, a new object-based shadow detection framework is introduced. In the proposed method a pixel-level shadow mask is built by extending established thresholding methods with a new C4 index which enables to solve the ambiguity of shadow and water bodies. Then the pixel-based results are further processed in an object-based majority analysis to detect the final shadow objects. Four different high resolution satellite images are used to validate this new approach. The result shows the superiority of the proposed method over some state-of-the-art shadow detection method with an average of 96% in F-measure.

NDVI, scale invariance and the modifiable areal unit problem: An assessment of vegetation in the Adelaide Parklands.

PubMed

Nouri, Hamideh; Anderson, Sharolyn; Sutton, Paul; Beecham, Simon; Nagler, Pamela; Jarchow, Christopher J; Roberts, Dar A

2017-04-15

This research addresses the question as to whether or not the Normalised Difference Vegetation Index (NDVI) is scale invariant (i.e. constant over spatial aggregation) for pure pixels of urban vegetation. It has been long recognized that there are issues related to the modifiable areal unit problem (MAUP) pertaining to indices such as NDVI and images at varying spatial resolutions. These issues are relevant to using NDVI values in spatial analyses. We compare two different methods of calculation of a mean NDVI: 1) using pixel values of NDVI within feature/object boundaries and 2) first calculating the mean red and mean near-infrared across all feature pixels and then calculating NDVI. We explore the nature and magnitude of these differences for images taken from two sensors, a 1.24m resolution WorldView-3 and a 0.1m resolution digital aerial image. We apply these methods over an urban park located in the Adelaide Parklands of South Australia. We demonstrate that the MAUP is not an issue for calculation of NDVI within a sensor for pure urban vegetation pixels. This may prove useful for future rule-based monitoring of the ecosystem functioning of green infrastructure. Copyright © 2017 Elsevier B.V. All rights reserved.

A sun-crown-sensor model and adapted C-correction logic for topographic correction of high resolution forest imagery

NASA Astrophysics Data System (ADS)

Fan, Yuanchao; Koukal, Tatjana; Weisberg, Peter J.

2014-10-01

Canopy shadowing mediated by topography is an important source of radiometric distortion on remote sensing images of rugged terrain. Topographic correction based on the sun-canopy-sensor (SCS) model significantly improved over those based on the sun-terrain-sensor (STS) model for surfaces with high forest canopy cover, because the SCS model considers and preserves the geotropic nature of trees. The SCS model accounts for sub-pixel canopy shadowing effects and normalizes the sunlit canopy area within a pixel. However, it does not account for mutual shadowing between neighboring pixels. Pixel-to-pixel shadowing is especially apparent for fine resolution satellite images in which individual tree crowns are resolved. This paper proposes a new topographic correction model: the sun-crown-sensor (SCnS) model based on high-resolution satellite imagery (IKONOS) and high-precision LiDAR digital elevation model. An improvement on the C-correction logic with a radiance partitioning method to address the effects of diffuse irradiance is also introduced (SCnS + C). In addition, we incorporate a weighting variable, based on pixel shadow fraction, on the direct and diffuse radiance portions to enhance the retrieval of at-sensor radiance and reflectance of highly shadowed tree pixels and form another variety of SCnS model (SCnS + W). Model evaluation with IKONOS test data showed that the new SCnS model outperformed the STS and SCS models in quantifying the correlation between terrain-regulated illumination factor and at-sensor radiance. Our adapted C-correction logic based on the sun-crown-sensor geometry and radiance partitioning better represented the general additive effects of diffuse radiation than C parameters derived from the STS or SCS models. The weighting factor Wt also significantly enhanced correction results by reducing within-class standard deviation and balancing the mean pixel radiance between sunlit and shaded slopes. We analyzed these improvements with model comparison on the red and near infrared bands. The advantages of SCnS + C and SCnS + W on both bands are expected to facilitate forest classification and change detection applications.

Study of the Dependency on Magnetic Field and Bias Voltage of an AC-Biased TES Microcalorimeter

NASA Technical Reports Server (NTRS)

Gottardi, L.; Bruijn, M.; denHartog, R.; Hoevers, H.; deKorte, P.; vanderKuur, J.; Linderman, M.; Adams, J.; Bailey, C.; Bandler, S.;

Study of the Dependence on Magnetic Field and Bias Voltage of an AC-Biased TES Microcalorimeter

NASA Technical Reports Server (NTRS)

Bandler, Simon

2011-01-01

At SRON we are studying the performance of a Goddard Space Flight Center single pixel TES microcalorimeter operated in the AC bias configuration. For x-ray photons at 6keV the AC biased pixel shows a best energy resolution of 3.7eV, which is about a factor of 2 worse than the energy resolution observed in identical DC-biased pixels. To better understand the reasons of this discrepancy, we investigated the detector performance as a function of temperature, bias working point and applied magnetic field. A strong periodic dependence of the detector noise on the TES AC bias voltage is measured. We discuss the results in the framework of the recent weak-link behaviour observed inTES microcalorimeters.

Image Simulation and Assessment of the Colour and Spatial Capabilities of the Colour and Stereo Surface Imaging System (CaSSIS) on the ExoMars Trace Gas Orbiter

NASA Astrophysics Data System (ADS)

Tornabene, Livio L.; Seelos, Frank P.; Pommerol, Antoine; Thomas, Nicholas; Caudill, C. M.; Becerra, Patricio; Bridges, John C.; Byrne, Shane; Cardinale, Marco; Chojnacki, Matthew; Conway, Susan J.; Cremonese, Gabriele; Dundas, Colin M.; El-Maarry, M. R.; Fernando, Jennifer; Hansen, Candice J.; Hansen, Kayle; Harrison, Tanya N.; Henson, Rachel; Marinangeli, Lucia; McEwen, Alfred S.; Pajola, Maurizio; Sutton, Sarah S.; Wray, James J.

2018-02-01

This study aims to assess the spatial and visible/near-infrared (VNIR) colour/spectral capabilities of the 4-band Colour and Stereo Surface Imaging System (CaSSIS) aboard the ExoMars 2016 Trace Grace Orbiter (TGO). The instrument response functions for the CaSSIS imager was used to resample spectral libraries, modelled spectra and to construct spectrally ( i.e., in I/F space) and spatially consistent simulated CaSSIS image cubes of various key sites of interest and for ongoing scientific investigations on Mars. Coordinated datasets from Mars Reconnaissance Orbiter (MRO) are ideal, and specifically used for simulating CaSSIS. The Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) provides colour information, while the Context Imager (CTX), and in a few cases the High-Resolution Imaging Science Experiment (HiRISE), provides the complementary spatial information at the resampled CaSSIS unbinned/unsummed pixel resolution (4.6 m/pixel from a 400-km altitude). The methodology used herein employs a Gram-Schmidt spectral sharpening algorithm to combine the ˜18-36 m/pixel CRISM-derived CaSSIS colours with I/F images primarily derived from oversampled CTX images. One hundred and eighty-one simulated CaSSIS 4-colour image cubes (at 18-36 m/pixel) were generated (including one of Phobos) based on CRISM data. From these, thirty-three "fully"-simulated image cubes of thirty unique locations on Mars ( i.e., with 4 colour bands at 4.6 m/pixel) were made. All simulated image cubes were used to test both the colour capabilities of CaSSIS by producing standard colour RGB images, colour band ratio composites (CBRCs) and spectral parameters. Simulated CaSSIS CBRCs demonstrated that CaSSIS will be able to readily isolate signatures related to ferrous (Fe2+) iron- and ferric (Fe3+) iron-bearing deposits on the surface of Mars, ices and atmospheric phenomena. Despite the lower spatial resolution of CaSSIS when compared to HiRISE, the results of this work demonstrate that CaSSIS will not only compliment HiRISE-scale studies of various geological and seasonal phenomena, it will also enhance them by providing additional colour and geologic context through its wider and longer full-colour coverage (˜9.4 × 50 km), and its increased sensitivity to iron-bearing materials from its two IR bands (RED and NIR). In a few examples, subtle surface changes that were not easily detected by HiRISE were identified in the simulated CaSSIS images. This study also demonstrates the utility of the Gram-Schmidt spectral pan-sharpening technique to extend VNIR colour/spectral capabilities from a lower spatial resolution colour/spectral dataset to a single-band or panchromatic image greyscale image with higher resolution. These higher resolution colour products (simulated CaSSIS or otherwise) are useful as means to extend both geologic context and mapping of datasets with coarser spatial resolutions. The results of this study indicate that the TGO mission objectives, as well as the instrument-specific mission objectives, will be achievable with CaSSIS.

Collection of holes in thick TlBr detectors at low temperature

NASA Astrophysics Data System (ADS)

Dönmez, Burçin; He, Zhong; Kim, Hadong; Cirignano, Leonard J.; Shah, Kanai S.

2012-10-01

A 3.5×3.5×4.6 mm3 thick TlBr detector with pixellated Au/Cr anodes made by Radiation Monitoring Devices Inc. was studied. The detector has a planar cathode and nine anode pixels surrounded by a guard ring. The pixel pitch is 1.0 mm. Digital pulse waveforms of preamplifier outputs were recorded using a multi-channel GaGe PCI digitizer board. Several experiments were carried out at -20 °C, with the detector under bias for over a month. An energy resolution of 1.7% FWHM at 662 keV was measured without any correction at -2400 V bias. Holes generated at all depths can be collected by the cathode at -2400 V bias which made depth correction using the cathode-to-anode ratio technique difficult since both charge carriers contribute to the signal. An energy resolution of 5.1% FWHM at 662 keV was obtained from the best pixel electrode without depth correction at +1000 V bias. In this positive bias case, the pixel electrode was actually collecting holes. A hole mobility-lifetime of 0.95×10-4 cm2/V has been estimated from measurement data.

X-ray characterization of a multichannel smart-pixel array detector.

PubMed

Ross, Steve; Haji-Sheikh, Michael; Huntington, Andrew; Kline, David; Lee, Adam; Li, Yuelin; Rhee, Jehyuk; Tarpley, Mary; Walko, Donald A; Westberg, Gregg; Williams, George; Zou, Haifeng; Landahl, Eric

2016-01-01

The Voxtel VX-798 is a prototype X-ray pixel array detector (PAD) featuring a silicon sensor photodiode array of 48 × 48 pixels, each 130 µm × 130 µm × 520 µm thick, coupled to a CMOS readout application specific integrated circuit (ASIC). The first synchrotron X-ray characterization of this detector is presented, and its ability to selectively count individual X-rays within two independent arrival time windows, a programmable energy range, and localized to a single pixel is demonstrated. During our first trial run at Argonne National Laboratory's Advance Photon Source, the detector achieved a 60 ns gating time and 700 eV full width at half-maximum energy resolution in agreement with design parameters. Each pixel of the PAD holds two independent digital counters, and the discriminator for X-ray energy features both an upper and lower threshold to window the energy of interest discarding unwanted background. This smart-pixel technology allows energy and time resolution to be set and optimized in software. It is found that the detector linearity follows an isolated dead-time model, implying that megahertz count rates should be possible in each pixel. Measurement of the line and point spread functions showed negligible spatial blurring. When combined with the timing structure of the synchrotron storage ring, it is demonstrated that the area detector can perform both picosecond time-resolved X-ray diffraction and fluorescence spectroscopy measurements.

Fast Imaging Detector Readout Circuits with In-Pixel ADCs for Fourier Transform Imaging Spectrometers

NASA Technical Reports Server (NTRS)

Rider, D.; Blavier, J-F.; Cunningham, T.; Hancock, B.; Key, R.; Pannell, Z.; Sander, S.; Seshadri, S.; Sun, C.; Wrigley, C.

2011-01-01

Focal plane arrays (FPAs) with high frame rates and many pixels benefit several upcoming Earth science missions including GEO-CAPE, GACM, and ACE by enabling broader spatial coverage and higher spectral resolution. FPAs for the PanFTS, a high spatial resolution Fourier transform spectrometer and a candidate instrument for the GEO-CAPE mission are the focus of the developments reported here, but this FPA technology has the potential to enable a variety of future measurements and instruments. The ESTO ACT Program funded the developed of a fast readout integrated circuit (ROIC) based on an innovative in-pixel analog-to-digital converter (ADC). The 128 X 128 pixel ROIC features 60 ?m pixels, a 14-bit ADC in each pixel and operates at a continuous frame rate of 14 kHz consuming only 1.1 W of power. The ROIC outputs digitized data completely eliminating the bulky, power consuming signal chains needed by conventional FPAs. The 128 X 128 pixel ROIC has been fabricated in CMOS and tested at the Jet Propulsion Laboratory. The current version is designed to be hybridized with PIN photodiode arrays via indium bump bonding for light detection in the visible and ultraviolet spectral regions. However, the ROIC design incorporates a small photodiode in each cell to permit detailed characterization of the ROICperformance without the need for hybridization. We will describe the essential features of the ROIC design and present results of ROIC performance measurements.

Avoiding Stair-Step Artifacts in Image Registration for GOES-R Navigation and Registration Assessment

NASA Technical Reports Server (NTRS)

Grycewicz, Thomas J.; Tan, Bin; Isaacson, Peter J.; De Luccia, Frank J.; Dellomo, John

2016-01-01

In developing software for independent verification and validation (IVV) of the Image Navigation and Registration (INR) capability for the Geostationary Operational Environmental Satellite R Series (GOES-R) Advanced Baseline Imager (ABI), we have encountered an image registration artifact which limits the accuracy of image offset estimation at the subpixel scale using image correlation. Where the two images to be registered have the same pixel size, subpixel image registration preferentially selects registration values where the image pixel boundaries are close to lined up. Because of the shape of a curve plotting input displacement to estimated offset, we call this a stair-step artifact. When one image is at a higher resolution than the other, the stair-step artifact is minimized by correlating at the higher resolution. For validating ABI image navigation, GOES-R images are correlated with Landsat-based ground truth maps. To create the ground truth map, the Landsat image is first transformed to the perspective seen from the GOES-R satellite, and then is scaled to an appropriate pixel size. Minimizing processing time motivates choosing the map pixels to be the same size as the GOES-R pixels. At this pixel size image processing of the shift estimate is efficient, but the stair-step artifact is present. If the map pixel is very small, stair-step is not a problem, but image correlation is computation-intensive. This paper describes simulation-based selection of the scale for truth maps for registering GOES-R ABI images.

The FoCal prototype—an extremely fine-grained electromagnetic calorimeter using CMOS pixel sensors

NASA Astrophysics Data System (ADS)

de Haas, A. P.; Nooren, G.; Peitzmann, T.; Reicher, M.; Rocco, E.; Röhrich, D.; Ullaland, K.; van den Brink, A.; van Leeuwen, M.; Wang, H.; Yang, S.; Zhang, C.

2018-01-01

A prototype of a Si-W EM calorimeter was built with Monolithic Active Pixel Sensors as the active elements. With a pixel size of 30 μm it allows digital calorimetry, i.e. the particle's energy is determined by counting pixels, not by measuring the energy deposited. Although of modest size, with a width of only four Moliere radii, it has 39 million pixels. In this article the construction and tuning of the prototype is described. Results from beam tests are compared with predictions of GEANT-based Monte Carlo simulations. The shape of showers caused by electrons is shown in unprecedented detail. Results for energy and position resolution are also given.

The Atlases of Vesta derived from Dawn Framing Camera images

NASA Astrophysics Data System (ADS)

Roatsch, T.; Kersten, E.; Matz, K.; Preusker, F.; Scholten, F.; Jaumann, R.; Raymond, C. A.; Russell, C. T.

2013-12-01

The Dawn Framing Camera acquired during its two HAMO (High Altitude Mapping Orbit) phases in 2011 and 2012 about 6,000 clear filter images with a resolution of about 60 m/pixel. We combined these images in a global ortho-rectified mosaic of Vesta (60 m/pixel resolution). Only very small areas near the northern pole were still in darkness and are missing in the mosaic. The Dawn Framing Camera also acquired about 10,000 high-resolution clear filter images (about 20 m/pixel) of Vesta during its Low Altitude Mapping Orbit (LAMO). Unfortunately, the northern part of Vesta was still in darkness during this phase, good illumination (incidence angle < 70°) was only available for 66.8 % of the surface [1]. We used the LAMO images to calculate another global mosaic of Vesta, this time with 20 m/pixel resolution. Both global mosaics were used to produce atlases of Vesta: a HAMO atlas with 15 tiles at a scale of 1:500,000 and a LAMO atlas with 30 tiles at a scale between 1:200,000 and 1:225,180. The nomenclature used in these atlases is based on names and places historically associated with the Roman goddess Vesta, and is compliant with the rules of the IAU. 65 names for geological features were already approved by the IAU, 39 additional names are currently under review. Selected examples of both atlases will be shown in this presentation. Reference: [1]Roatsch, Th., etal., High-resolution Vesta Low Altitude Mapping Orbit Atlas derived from Dawn Framing Camera images. Planetary and Space Science (2013), http://dx.doi.org/10.1016/j.pss.2013.06.024i

AM OLED using a-Si TFT backplane on flexible plastic substrate

NASA Astrophysics Data System (ADS)

Sarma, Kalluri R.; Schmidt, John; Roush, Jerry; Chanley, Charles; Dodd, Sonia R.

2004-09-01

Amorphous silicon TFT technology continues to show promise for fabricating large area high resolution flexible AM OLED displays. This paper describes the recent progress in the flexible AM OLED development efforts at Honeywell since our publication in this conference's proceedings in 2003, describing the feasibility of fabricating a 64x64 pixel AM OLED on a flexible plastic substrate. In this paper we describe the design, and fabrication of a 160x160(x3) pixel AM OLED on a flexible plastic substrate with an equivalent 80cgpi resolution. Flexibility characteristics of the fabricated displays are discussed. Further advances and improvements required for extending the size and resolution of flexible AM OLED displays are discussed.

Mars Boulders: On a Hill in Utopia Planitia

NASA Image and Video Library

2000-09-18

The Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) was designed specifically to provide images of Mars that have a resolution comparable to the aerial photographs commonly used by Earth scientists to study geological processes and map landforms on our home planet. When MGS reaches its Mapping Orbit in March 1999, MOC will be able to obtain pictures with spatial resolutions of 1.5 meters (5 feet) per pixel--this good enough to easily see objects the size of an automobile. Boulders are one of the keys to determining which processes have eroded, transported, and deposited material on Mars (e.g.,landslides, mud flows, flood debris). During the first year in orbit,MGS MOC obtained pictures with resolutions between 2 and 30 meters (7to 98 feet) per pixel. It was found that boulders are difficult to identify on Mars in images with resolutions worse than about 2-3 meters per pixel. Although not known when the MOC was designed,"thresholds" like this are found on Earth, too. The MOC's 1.5 m/pixel resolution was a compromise between (1) the anticipation of such resolution-dependent sensitivity based on our experience with Earth and (2)the cost in terms of mass if we had built a larger telescope to get a higher resolution. Some rather larger boulders (i.e., larger than about 10 meters--or yards--in size) have already been seen on Mars by the orbiting camera. This is a feat similar to that which can be obtained by "spy" satellites on Earth. The MOC image 53104 subframe shown above features a low, rounded hill in southeastern Utopia Planitia. Each of the small, lumpy features on the top of this hill is a boulder. In this picture, boulders are not seen on the surrounding plain. These boulders are interpreted to be the remnants of a layer of harder rock that once covered the top of the hill, but was subsequently eroded and broken up by weathering and wind processes. MOC image 53104 was taken on September 2, 1998. The subframe shows an area 2.2 km by 3.3 km (1.4 miles by 2.7 miles). The image has a resolution of about 3.25 meters (10.7 feet) per pixel. The subframe is centered at 41.0°N latitude and 207.3°W longitude. North is approximately up, illumination is from the left. http://photojournal.jpl.nasa.gov/catalog/PIA01500

Frequency-multiplexed bias and readout of a 16-pixel superconducting nanowire single-photon detector array

NASA Astrophysics Data System (ADS)

Doerner, S.; Kuzmin, A.; Wuensch, S.; Charaev, I.; Boes, F.; Zwick, T.; Siegel, M.

2017-07-01

We demonstrate a 16-pixel array of microwave-current driven superconducting nanowire single-photon detectors with an integrated and scalable frequency-division multiplexing architecture, which reduces the required number of bias and readout lines to a single microwave feed line. The electrical behavior of the photon-sensitive nanowires, embedded in a resonant circuit, as well as the optical performance and timing jitter of the single detectors is discussed. Besides the single pixel measurements, we also demonstrate the operation of a 16-pixel array with a temporal, spatial, and photon-number resolution.

Using Satellite Data to Characterize the Temporal Thermal Behavior of an Active Volcano: Mount St. Helens, WA

NASA Technical Reports Server (NTRS)

Vaughan, R. Greg; Hook, Simon J.

2006-01-01

ASTER thermal infrared data over Mt. St Helens were used to characterize its thermal behavior from Jun 2000 to Feb 2006. Prior to the Oct 2004 eruption, the average crater temperature varied seasonally between -12 and 6 C. After the eruption, maximum single-pixel temperature increased from 10 C (Oct 2004) to 96 C (Aug 2005), then showed a decrease to Feb 2006. The initial increase in temperature was correlated with dome morphology and growth rate and the subsequent decrease was interpreted to relate to both seasonal trends and a decreased growth rate/increased cooling rate, possibly suggesting a significant change in the volcanic system. A single-pixel ASTER thermal anomaly first appeared on Oct 1, 2004, eleven hours after the first eruption - 10 days before new lava was exposed at the surface. By contrast, an automated algorithm for detecting thermal anomalies in MODIS data did not trigger an alert until Dec 18. However, a single-pixel thermal anomaly first appeared in MODIS channel 23 (4 um) on Oct 13, 12 days after the first eruption - 2 days after lava was exposed. The earlier thermal anomaly detected with ASTER data is attributed to the higher spatial resolution (90 m) compared with MODIS (1 m) and the earlier visual observation of anomalous pixels compared to the automated detection method suggests that local spatial statistics and background radiance data could improve automated detection methods.

GATE simulation of a new design of pinhole SPECT system for small animal brain imaging

NASA Astrophysics Data System (ADS)

Uzun Ozsahin, D.; Bläckberg, L.; El Fakhri, G.; Sabet, H.

2017-01-01

Small animal SPECT imaging has gained an increased interest over the past decade since it is an excellent tool for developing new drugs and tracers. Therefore, there is a huge effort on the development of cost-effective SPECT detectors with high capabilities. The aim of this study is to simulate the performance characteristics of new designs for a cost effective, stationary SPECT system dedicated to small animal imaging with a focus on mice brain. The conceptual design of this SPECT system platform, Stationary Small Animal SSA-SPECT, is to use many pixelated CsI:TI detector modules with 0.4 mm × 0.4 mm pixels in order to achieve excellent intrinsic detector resolution where each module is backed by a single pinhole collimator with 0.3 mm hole diameter. In this work, we present the simulation results of four variations of the SSA-SPECT platform where the number of detector modules and FOV size is varied while keeping the detector size and collimator hole size constant. Using the NEMA NU-4 protocol, we performed spatial resolution, sensitivity, image quality simulations followed by a Derenzo-like phantom evaluation. The results suggest that all four SSA-SPECT systems can provide better than 0.063% system sensitivity and < 1.5 mm FWHM spatial resolution without resolution recovery or other correction techniques. Specifically, SSA-SPECT-1 showed a system sensitivity of 0.09% in combination with 1.1 mm FWHM spatial resolution.

Self-Powered High-Resolution and Pressure-Sensitive Triboelectric Sensor Matrix for Real-Time Tactile Mapping.

PubMed

Wang, Xiandi; Zhang, Hanlu; Dong, Lin; Han, Xun; Du, Weiming; Zhai, Junyi; Pan, Caofeng; Wang, Zhong Lin

2016-04-20

A triboelectric sensor matrix (TESM) can accurately track and map 2D tactile sensing. A self-powered, high-resolution, pressure-sensitive, flexible and durable TESM with 16 × 16 pixels is fabricated for the fast detection of single-point and multi-point touching. Using cross-locating technology, a cross-type TESM with 32 × 20 pixels is developed for more rapid tactile mapping, which significantly reduces the addressing lines from m × n to m + n. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

A time-resolved image sensor for tubeless streak cameras

NASA Astrophysics Data System (ADS)

Yasutomi, Keita; Han, SangMan; Seo, Min-Woong; Takasawa, Taishi; Kagawa, Keiichiro; Kawahito, Shoji

2014-03-01

This paper presents a time-resolved CMOS image sensor with draining-only modulation (DOM) pixels for tube-less streak cameras. Although the conventional streak camera has high time resolution, the device requires high voltage and bulky system due to the structure with a vacuum tube. The proposed time-resolved imager with a simple optics realize a streak camera without any vacuum tubes. The proposed image sensor has DOM pixels, a delay-based pulse generator, and a readout circuitry. The delay-based pulse generator in combination with an in-pixel logic allows us to create and to provide a short gating clock to the pixel array. A prototype time-resolved CMOS image sensor with the proposed pixel is designed and implemented using 0.11um CMOS image sensor technology. The image array has 30(Vertical) x 128(Memory length) pixels with the pixel pitch of 22.4um. .

Enhanced Deforestation Mapping in North Korea using Spatial-temporal Image Fusion Method and Phenology-based Index

NASA Astrophysics Data System (ADS)

Jin, Y.; Lee, D.

2017-12-01

North Korea (the Democratic People's Republic of Korea, DPRK) is known to have some of the most degraded forest in the world. The characteristics of forest landscape in North Korea is complex and heterogeneous, the major vegetation cover types in the forest are hillside farm, unstocked forest, natural forest, and plateau vegetation. Better classification of types in high spatial resolution of deforested areas could provide essential information for decisions about forest management priorities and restoration of deforested areas. For mapping heterogeneous vegetation covers, the phenology-based indices are helpful to overcome the reflectance value confusion that occurs when using one season images. Coarse spatial resolution images may be acquired with a high repetition rate and it is useful for analyzing phenology characteristics, but may not capture the spatial detail of the land cover mosaic of the region of interest. Previous spatial-temporal fusion methods were only capture the temporal change, or focused on both temporal change and spatial change but with low accuracy in heterogeneous landscapes and small patches. In this study, a new concept for spatial-temporal image fusion method focus on heterogeneous landscape was proposed to produce fine resolution images at both fine spatial and temporal resolution. We classified the three types of pixels between the base image and target image, the first type is only reflectance changed caused by phenology, this type of pixels supply the reflectance, shape and texture information; the second type is both reflectance and spectrum changed in some bands caused by phenology like rice paddy or farmland, this type of pixels only supply shape and texture information; the third type is reflectance and spectrum changed caused by land cover type change, this type of pixels don't provide any information because we can't know how land cover changed in target image; and each type of pixels were applied different prediction methods. Results show that both STARFM and FSDAF predicted in low accuracy in second type pixels and small patches. Classification results used spatial-temporal image fusion method proposed in this study showed overall classification accuracy of 89.38%, with corresponding kappa coefficients of 0.87.

Accounting for sub-pixel variability of clouds and/or unresolved spectral variability, as needed, with generalized radiative transfer theory

DOE PAGES

Davis, Anthony B.; Xu, Feng; Collins, William D.

2015-03-01

Atmospheric hyperspectral VNIR sensing struggles with sub-pixel variability of clouds and limited spectral resolution mixing molecular lines. Our generalized radiative transfer model addresses both issues with new propagation kernels characterized by power-law decay in space.

Sub-Pixel Mapping of Tree Canopy, Impervious Surfaces, and Cropland in the Laurentian Great Lakes Basin Using MODIS Time-Series Data

EPA Science Inventory

This research examined sub-pixel land-cover classification performance for tree canopy, impervious surface, and cropland in the Laurentian Great Lakes Basin (GLB) using both timeseries MODIS (MOderate Resolution Imaging Spectroradiometer) NDVI (Normalized Difference Vegetation In...

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ross, Steve; Haji-Sheikh, Michael; Huntington, Andrew

The Voxtel VX-798 is a prototype X-ray pixel array detector (PAD) featuring a silicon sensor photodiode array of 48 x 48 pixels, each 130 mu m x 130 mu m x 520 mu m thick, coupled to a CMOS readout application specific integrated circuit (ASIC). The first synchrotron X-ray characterization of this detector is presented, and its ability to selectively count individual X-rays within two independent arrival time windows, a programmable energy range, and localized to a single pixel is demonstrated. During our first trial run at Argonne National Laboratory's Advance Photon Source, the detector achieved a 60 ns gatingmore » time and 700 eV full width at half-maximum energy resolution in agreement with design parameters. Each pixel of the PAD holds two independent digital counters, and the discriminator for X-ray energy features both an upper and lower threshold to window the energy of interest discarding unwanted background. This smart-pixel technology allows energy and time resolution to be set and optimized in software. It is found that the detector linearity follows an isolated dead-time model, implying that megahertz count rates should be possible in each pixel. Measurement of the line and point spread functions showed negligible spatial blurring. When combined with the timing structure of the synchrotron storage ring, it is demonstrated that the area detector can perform both picosecond time-resolved X-ray diffraction and fluorescence spectroscopy measurements.« less

Multi-Resolution Analysis of MODIS and ASTER Satellite Data for Water Classification

DTIC Science & Technology

2006-09-01

spectral bands, but also with different pixel resolutions . The overall goal... the total water surface. Due to the constraint that high spatial resolution satellite images are low temporal resolution , one needs a reliable method...at 15 m resolution , were processed. We used MODIS reflectance data from MOD02 Level 1B data. Even the spatial resolution of the 1240 nm

Droplet Image Super Resolution Based on Sparse Representation and Kernel Regression

NASA Astrophysics Data System (ADS)

Zou, Zhenzhen; Luo, Xinghong; Yu, Qiang

2018-02-01

Microgravity and containerless conditions, which are produced via electrostatic levitation combined with a drop tube, are important when studying the intrinsic properties of new metastable materials. Generally, temperature and image sensors can be used to measure the changes of sample temperature, morphology and volume. Then, the specific heat, surface tension, viscosity changes and sample density can be obtained. Considering that the falling speed of the material sample droplet is approximately 31.3 m/s when it reaches the bottom of a 50-meter-high drop tube, a high-speed camera with a collection rate of up to 106 frames/s is required to image the falling droplet. However, at the high-speed mode, very few pixels, approximately 48-120, will be obtained in each exposure time, which results in low image quality. Super-resolution image reconstruction is an algorithm that provides finer details than the sampling grid of a given imaging device by increasing the number of pixels per unit area in the image. In this work, we demonstrate the application of single image-resolution reconstruction in the microgravity and electrostatic levitation for the first time. Here, using the image super-resolution method based on sparse representation, a low-resolution droplet image can be reconstructed. Employed Yang's related dictionary model, high- and low-resolution image patches were combined with dictionary training, and high- and low-resolution-related dictionaries were obtained. The online double-sparse dictionary training algorithm was used in the study of related dictionaries and overcome the shortcomings of the traditional training algorithm with small image patch. During the stage of image reconstruction, the algorithm of kernel regression is added, which effectively overcomes the shortcomings of the Yang image's edge blurs.

Droplet Image Super Resolution Based on Sparse Representation and Kernel Regression

NASA Astrophysics Data System (ADS)

Zou, Zhenzhen; Luo, Xinghong; Yu, Qiang

2018-05-01

Microgravity and containerless conditions, which are produced via electrostatic levitation combined with a drop tube, are important when studying the intrinsic properties of new metastable materials. Generally, temperature and image sensors can be used to measure the changes of sample temperature, morphology and volume. Then, the specific heat, surface tension, viscosity changes and sample density can be obtained. Considering that the falling speed of the material sample droplet is approximately 31.3 m/s when it reaches the bottom of a 50-meter-high drop tube, a high-speed camera with a collection rate of up to 106 frames/s is required to image the falling droplet. However, at the high-speed mode, very few pixels, approximately 48-120, will be obtained in each exposure time, which results in low image quality. Super-resolution image reconstruction is an algorithm that provides finer details than the sampling grid of a given imaging device by increasing the number of pixels per unit area in the image. In this work, we demonstrate the application of single image-resolution reconstruction in the microgravity and electrostatic levitation for the first time. Here, using the image super-resolution method based on sparse representation, a low-resolution droplet image can be reconstructed. Employed Yang's related dictionary model, high- and low-resolution image patches were combined with dictionary training, and high- and low-resolution-related dictionaries were obtained. The online double-sparse dictionary training algorithm was used in the study of related dictionaries and overcome the shortcomings of the traditional training algorithm with small image patch. During the stage of image reconstruction, the algorithm of kernel regression is added, which effectively overcomes the shortcomings of the Yang image's edge blurs.

High-dynamic-range coherent diffractive imaging: ptychography using the mixed-mode pixel array detector.

PubMed

Giewekemeyer, Klaus; Philipp, Hugh T; Wilke, Robin N; Aquila, Andrew; Osterhoff, Markus; Tate, Mark W; Shanks, Katherine S; Zozulya, Alexey V; Salditt, Tim; Gruner, Sol M; Mancuso, Adrian P

2014-09-01

Coherent (X-ray) diffractive imaging (CDI) is an increasingly popular form of X-ray microscopy, mainly due to its potential to produce high-resolution images and the lack of an objective lens between the sample and its corresponding imaging detector. One challenge, however, is that very high dynamic range diffraction data must be collected to produce both quantitative and high-resolution images. In this work, hard X-ray ptychographic coherent diffractive imaging has been performed at the P10 beamline of the PETRA III synchrotron to demonstrate the potential of a very wide dynamic range imaging X-ray detector (the Mixed-Mode Pixel Array Detector, or MM-PAD). The detector is capable of single photon detection, detecting fluxes exceeding 1 × 10(8) 8-keV photons pixel(-1) s(-1), and framing at 1 kHz. A ptychographic reconstruction was performed using a peak focal intensity on the order of 1 × 10(10) photons µm(-2) s(-1) within an area of approximately 325 nm × 603 nm. This was done without need of a beam stop and with a very modest attenuation, while `still' images of the empty beam far-field intensity were recorded without any attenuation. The treatment of the detector frames and CDI methodology for reconstruction of non-sensitive detector regions, partially also extending the active detector area, are described.

High-resolution CCD imaging alternatives

NASA Astrophysics Data System (ADS)

Brown, D. L.; Acker, D. E.

1992-08-01

High resolution CCD color cameras have recently stimulated the interest of a large number of potential end-users for a wide range of practical applications. Real-time High Definition Television (HDTV) systems are now being used or considered for use in applications ranging from entertainment program origination through digital image storage to medical and scientific research. HDTV generation of electronic images offers significant cost and time-saving advantages over the use of film in such applications. Further in still image systems electronic image capture is faster and more efficient than conventional image scanners. The CCD still camera can capture 3-dimensional objects into the computing environment directly without having to shoot a picture on film develop it and then scan the image into a computer. 2. EXTENDING CCD TECHNOLOGY BEYOND BROADCAST Most standard production CCD sensor chips are made for broadcast-compatible systems. One popular CCD and the basis for this discussion offers arrays of roughly 750 x 580 picture elements (pixels) or a total array of approximately 435 pixels (see Fig. 1). FOR. A has developed a technique to increase the number of available pixels for a given image compared to that produced by the standard CCD itself. Using an inter-lined CCD with an overall spatial structure several times larger than the photo-sensitive sensor areas each of the CCD sensors is shifted in two dimensions in order to fill in spatial gaps between adjacent sensors.

Transition-Edge Sensor Pixel Parameter Design of the Microcalorimeter Array for the X-Ray Integral Field Unit on Athena

NASA Technical Reports Server (NTRS)

Smith, S. J.; Adams, J. S.; Bandler, S. R.; Betancourt-Martinez, G. L.; Chervenak, J. A.; Chiao, M. P.; Eckart, M. E.; Finkbeiner, F. M.; Kelley, R. L.; Kilbourne, C. A.;

Transition-edge sensor pixel parameter design of the microcalorimeter array for the x-ray integral field unit on Athena

NASA Astrophysics Data System (ADS)

Smith, S. J.; Adams, J. S.; Bandler, S. R.; Betancourt-Martinez, G. L.; Chervenak, J. A.; Chiao, M. P.; Eckart, M. E.; Finkbeiner, F. M.; Kelley, R. L.; Kilbourne, C. A.; Miniussi, A. R.; Porter, F. S.; Sadleir, J. E.; Sakai, K.; Wakeham, N. A.; Wassell, E. J.; Yoon, W.; Bennett, D. A.; Doriese, W. B.; Fowler, J. W.; Hilton, G. C.; Morgan, K. M.; Pappas, C. G.; Reintsema, C. N.; Swetz, D. S.; Ullom, J. N.; Irwin, K. D.; Akamatsu, H.; Gottardi, L.; den Hartog, R.; Jackson, B. D.; van der Kuur, J.; Barret, D.; Peille, P.

2016-07-01

The focal plane of the X-ray integral field unit (X-IFU) for ESA's Athena X-ray observatory will consist of 4000 transition edge sensor (TES) x-ray microcalorimeters optimized for the energy range of 0.2 to 12 keV. The instrument will provide unprecedented spectral resolution of 2.5 eV at energies of up to 7 keV and will accommodate photon fluxes of 1 mCrab (90 cps) for point source observations. The baseline configuration is a uniform large pixel array (LPA) of 4.28" pixels that is read out using frequency domain multiplexing (FDM). However, an alternative configuration under study incorporates an 18 × 18 small pixel array (SPA) of 2" pixels in the central 36" region. This hybrid array configuration could be designed to accommodate higher fluxes of up to 10 mCrab (900 cps) or alternately for improved spectral performance (< 1.5 eV) at low count-rates. In this paper we report on the TES pixel designs that are being optimized to meet these proposed LPA and SPA configurations. In particular we describe details of how important TES parameters are chosen to meet the specific mission criteria such as energy resolution, count-rate and quantum efficiency, and highlight performance trade-offs between designs. The basis of the pixel parameter selection is discussed in the context of existing TES arrays that are being developed for solar and x-ray astronomy applications. We describe the latest results on DC biased diagnostic arrays as well as large format kilo-pixel arrays and discuss the technical challenges associated with integrating different array types on to a single detector die.

Improving Nocturnal Fire Detection with the VIIRS Day-Night Band

NASA Technical Reports Server (NTRS)

Polivka, Thomas N.; Wang, Jun; Ellison, Luke T.; Hyer, Edward J.; Ichoku, Charles M.

2016-01-01

Building on existing techniques for satellite remote sensing of fires, this paper takes advantage of the day-night band (DNB) aboard the Visible Infrared Imaging Radiometer Suite (VIIRS) to develop the Firelight Detection Algorithm (FILDA), which characterizes fire pixels based on both visible-light and infrared (IR) signatures at night. By adjusting fire pixel selection criteria to include visible-light signatures, FILDA allows for significantly improved detection of pixels with smaller and/or cooler subpixel hotspots than the operational Interface Data Processing System (IDPS) algorithm. VIIRS scenes with near-coincident Advanced Spaceborne Thermal Emission and Reflection (ASTER) overpasses are examined after applying the operational VIIRS fire product algorithm and including a modified "candidate fire pixel selection" approach from FILDA that lowers the 4-µm brightness temperature (BT) threshold but includes a minimum DNB radiance. FILDA is shown to be effective in detecting gas flares and characterizing fire lines during large forest fires (such as the Rim Fire in California and High Park fire in Colorado). Compared with the operational VIIRS fire algorithm for the study period, FILDA shows a large increase (up to 90%) in the number of detected fire pixels that can be verified with the finer resolution ASTER data (90 m). Part (30%) of this increase is likely due to a combined use of DNB and lower 4-µm BT thresholds for fire detection in FILDA. Although further studies are needed, quantitative use of the DNB to improve fire detection could lead to reduced response times to wildfires and better estimate of fire characteristics (smoldering and flaming) at night.

Performance evaluation of a two detector camera for real-time video.

PubMed

Lochocki, Benjamin; Gambín-Regadera, Adrián; Artal, Pablo

2016-12-20

Single pixel imaging can be the preferred method over traditional 2D-array imaging in spectral ranges where conventional cameras are not available. However, when it comes to real-time video imaging, single pixel imaging cannot compete with the framerates of conventional cameras, especially when high-resolution images are desired. Here we evaluate the performance of an imaging approach using two detectors simultaneously. First, we present theoretical results on how low SNR affects final image quality followed by experimentally determined results. Obtained video framerates were doubled compared to state of the art systems, resulting in a framerate from 22 Hz for a 32×32 resolution to 0.75 Hz for a 128×128 resolution image. Additionally, the two detector imaging technique enables the acquisition of images with a resolution of 256×256 in less than 3 s.

Structure-aware depth super-resolution using Gaussian mixture model

NASA Astrophysics Data System (ADS)

Kim, Sunok; Oh, Changjae; Kim, Youngjung; Sohn, Kwanghoon

2015-03-01

This paper presents a probabilistic optimization approach to enhance the resolution of a depth map. Conventionally, a high-resolution color image is considered as a cue for depth super-resolution under the assumption that the pixels with similar color likely belong to similar depth. This assumption might induce a texture transferring from the color image into the depth map and an edge blurring artifact to the depth boundaries. In order to alleviate these problems, we propose an efficient depth prior exploiting a Gaussian mixture model in which an estimated depth map is considered to a feature for computing affinity between two pixels. Furthermore, a fixed-point iteration scheme is adopted to address the non-linearity of a constraint derived from the proposed prior. The experimental results show that the proposed method outperforms state-of-the-art methods both quantitatively and qualitatively.

A new algorithm to reduce noise in microscopy images implemented with a simple program in python.

PubMed

Papini, Alessio

2012-03-01

All microscopical images contain noise, increasing when (e.g., transmission electron microscope or light microscope) approaching the resolution limit. Many methods are available to reduce noise. One of the most commonly used is image averaging. We propose here to use the mode of pixel values. Simple Python programs process a given number of images, recorded consecutively from the same subject. The programs calculate the mode of the pixel values in a given position (a, b). The result is a new image containing in (a, b) the mode of the values. Therefore, the final pixel value corresponds to that read in at least two of the pixels in position (a, b). The application of the program on a set of images obtained by applying salt and pepper noise and GIMP hurl noise with 10-90% standard deviation showed that the mode performs better than averaging with three-eight images. The data suggest that the mode would be more efficient (in the sense of a lower number of recorded images to process to reduce noise below a given limit) for lower number of total noisy pixels and high standard deviation (as impulse noise and salt and pepper noise), while averaging would be more efficient when the number of varying pixels is high, and the standard deviation is low, as in many cases of Gaussian noise affected images. The two methods may be used serially. Copyright © 2011 Wiley Periodicals, Inc.

Assessment of Vegetation Destruction Due to Wenchuan Earthquake and Its Recovery Process Using MODIS Data

NASA Astrophysics Data System (ADS)

Zou, Z.; Xiao, X.

2015-12-01

With a high temporal resolution and a large covering area, MODIS data are particularly useful in assessing vegetation destruction and recovery of a wide range of areas. In this study, MOD13Q1 data of the growing season (Mar. to Nov.) are used to calculate the Maximum NDVI (NDVImax) of each year. This study calculates each pixel's mean and standard deviation of the NDVImaxs in the 8 years before the earthquake. If the pixel's NDVImax of 2008 is two standard deviation smaller than the mean NDVImax, this pixel is detected as a vegetation destructed pixel. For each vegetation destructed pixel, its similar pixels of the same vegetation type are selected within the latitude difference of 0.5 degrees, altitude difference of 100 meters and slope difference of 3 degrees. Then the NDVImax difference of each vegetation destructed pixel and its similar pixels are calculated. The 5 similar pixels with the smallest NDVImax difference in the 8 years before the earthquake are selected as reference pixels. The mean NDVImaxs of these reference pixels after the earthquake are calculated and serve as the criterion to assess the vegetation recovery process.

Study of the Dependency on Magnetic Field and Bias Voltage of an AC-Biased TES Microcalorimeter.

PubMed

Gottardi, L; Adams, J; Bailey, C; Bandler, S; Bruijn, M; Chervenak, J; Eckart, M; Finkbeiner, F; den Hartog, R; Hoevers, H; Kelley, R; Kilbourne, C; de Korte, P; van der Kuur, J; Lindeman, M; Porter, F; Sadlier, J; Smith, S

At SRON we are studying the performance of a Goddard Space Flight Center single pixel TES microcalorimeter operated in an AC bias configuration. For x-ray photons at 6 keV the pixel shows an x-ray energy resolution Δ E FWHM =3.7 eV, which is about a factor 2 worse than the energy resolution observed in an identical DC-biased pixel. In order to better understand the reasons for this discrepancy we characterised the detector as a function of temperature, bias working point and applied perpendicular magnetic field. A strong periodic dependency of the detector noise on the TES AC bias voltage is measured. We discuss the results in the framework of the recently observed weak-link behaviour of a TES microcalorimeter.

Neural Network for Image-to-Image Control of Optical Tweezers

NASA Technical Reports Server (NTRS)

Decker, Arthur J.; Anderson, Robert C.; Weiland, Kenneth E.; Wrbanek, Susan Y.

2004-01-01

A method is discussed for using neural networks to control optical tweezers. Neural-net outputs are combined with scaling and tiling to generate 480 by 480-pixel control patterns for a spatial light modulator (SLM). The SLM can be combined in various ways with a microscope to create movable tweezers traps with controllable profiles. The neural nets are intended to respond to scattered light from carbon and silicon carbide nanotube sensors. The nanotube sensors are to be held by the traps for manipulation and calibration. Scaling and tiling allow the 100 by 100-pixel maximum resolution of the neural-net software to be applied in stages to exploit the full 480 by 480-pixel resolution of the SLM. One of these stages is intended to create sensitive null detectors for detecting variations in the scattered light from the nanotube sensors.

Test beam measurement of the first prototype of the fast silicon pixel monolithic detector for the TT-PET project

NASA Astrophysics Data System (ADS)

Paolozzi, L.; Bandi, Y.; Benoit, M.; Cardarelli, R.; Débieux, S.; Forshaw, D.; Hayakawa, D.; Iacobucci, G.; Kaynak, M.; Miucci, A.; Nessi, M.; Ratib, O.; Ripiccini, E.; Rücker, H.; Valerio, P.; Weber, M.

2018-04-01

The TT-PET collaboration is developing a PET scanner for small animals with 30 ps time-of-flight resolution and sub-millimetre 3D detection granularity. The sensitive element of the scanner is a monolithic silicon pixel detector based on state-of-the-art SiGe BiCMOS technology. The first ASIC prototype for the TT-PET was produced and tested in the laboratory and with minimum ionizing particles. The electronics exhibit an equivalent noise charge below 600 e‑ RMS and a pulse rise time of less than 2 ns , in accordance with the simulations. The pixels with a capacitance of 0.8 pF were measured to have a detection efficiency greater than 99% and, although in the absence of the post-processing, a time resolution of approximately 200 ps .

Study of run time errors of the ATLAS pixel detector in the 2012 data taking period

NASA Astrophysics Data System (ADS)

Gandrajula, Reddy Pratap

The high resolution silicon Pixel detector is critical in event vertex reconstruction and in particle track reconstruction in the ATLAS detector. During the pixel data taking operation, some modules (Silicon Pixel sensor +Front End Chip+ Module Control Chip (MCC)) go to an auto-disable state, where the Modules don't send the data for storage. Modules become operational again after reconfiguration. The source of the problem is not fully understood. One possible source of the problem is traced to the occurrence of single event upset (SEU) in the MCC. Such a module goes to either a Timeout or Busy state. This report is the study of different types and rates of errors occurring in the Pixel data taking operation. Also, the study includes the error rate dependency on Pixel detector geometry.

Small Pixel Hybrid CMOS X-ray Detectors

NASA Astrophysics Data System (ADS)

Hull, Samuel; Bray, Evan; Burrows, David N.; Chattopadhyay, Tanmoy; Falcone, Abraham; Kern, Matthew; McQuaide, Maria; Wages, Mitchell

2018-01-01

Concepts for future space-based X-ray observatories call for a large effective area and high angular resolution instrument to enable precision X-ray astronomy at high redshift and low luminosity. Hybrid CMOS detectors are well suited for such high throughput instruments, and the Penn State X-ray detector lab, in collaboration with Teledyne Imaging Sensors, has recently developed new small pixel hybrid CMOS X-ray detectors. These prototype 128x128 pixel devices have 12.5 micron pixel pitch, 200 micron fully depleted depth, and include crosstalk eliminating CTIA amplifiers and in-pixel correlated double sampling (CDS) capability. We report on characteristics of these new detectors, including the best read noise ever measured for an X-ray hybrid CMOS detector, 5.67 e- (RMS).

Spatially resolved D-T(2) correlation NMR of porous media.

PubMed

Zhang, Yan; Blümich, Bernhard

2014-05-01

Within the past decade, 2D Laplace nuclear magnetic resonance (NMR) has been developed to analyze pore geometry and diffusion of fluids in porous media on the micrometer scale. Many objects like rocks and concrete are heterogeneous on the macroscopic scale, and an integral analysis of microscopic properties provides volume-averaged information. Magnetic resonance imaging (MRI) resolves this spatial average on the contrast scale set by the particular MRI technique. Desirable contrast parameters for studies of fluid transport in porous media derive from the pore-size distribution and the pore connectivity. These microscopic parameters are accessed by 1D and 2D Laplace NMR techniques. It is therefore desirable to combine MRI and 2D Laplace NMR to image functional information on fluid transport in porous media. Because 2D Laplace resolved MRI demands excessive measuring time, this study investigates the possibility to restrict the 2D Laplace analysis to the sum signals from low-resolution pixels, which correspond to pixels of similar amplitude in high-resolution images. In this exploratory study spatially resolved D-T2 correlation maps from glass beads and mortar are analyzed. Regions of similar contrast are first identified in high-resolution images to locate corresponding pixels in low-resolution images generated with D-T2 resolved MRI for subsequent pixel summation to improve the signal-to-noise ratio of contrast-specific D-T2 maps. This method is expected to contribute valuable information on correlated sample heterogeneity from the macroscopic and the microscopic scales in various types of porous materials including building materials and rock. Copyright © 2014 Elsevier Inc. All rights reserved.

Background concentrations for high resolution satellite observing systems of methane

NASA Astrophysics Data System (ADS)

Benmergui, J. S.; Propp, A. M.; Turner, A. J.; Wofsy, S. C.

2017-12-01

Emerging satellite technologies promise to measure total column dry-air mole fractions of methane (XCH4) at resolutions on the order of a kilometer. XCH4 is linearly related to regional methane emissions through enhancements in the mixed layer, giving these satellites the ability to constrain emissions at unprecedented resolution. However, XCH4 is also sensitive to variability in transport of upwind concentrations (the "background concentration"). Variations in the background concentration are caused by synoptic scale transport in both the free troposphere and the stratosphere, as well as the rate of methane oxidation. Misspecification of the background concentration is aliased onto retrieved emissions as bias. This work explores several methods of specifying the background concentration for high resolution satellite observations of XCH4. We conduct observing system simulation experiments (OSSEs) that simulate the retrieval of emissions in the Barnett Shale using observations from a 1.33 km resolution XCH4 imaging satellite. We test background concentrations defined (1) from an external continental-scale model, (2) using pixels along the edge of the image as a boundary value, (3) using differences between adjacent pixels, and (4) using differences between the same pixel separated by one hour in time. We measure success using the accuracy of the retrieval, the potential for bias induced by misspecification of the background, and the computational expedience of the method. Pathological scenarios are given to each method.

Recent progress in OLED and flexible displays and their potential for application to aerospace and military display systems

NASA Astrophysics Data System (ADS)

Sarma, Kalluri

2015-05-01

Organic light emitting diode (OLED) display technology has advanced significantly in recent years and it is increasingly being adapted in consumer electronics products with premium performance, such as high resolution smart phones, Tablet PCs and TVs. Even flexible OLED displays are beginning to be commercialized in consumer electronic devices such as smart phones and smart watches. In addition to the advances in OLED emitters, successful development and adoption of OLED displays for premium performance applications relies on the advances in several enabling technologies including TFT backplanes, pixel drive electronics, pixel patterning technologies, encapsulation technologies and system level engineering. In this paper we will discuss the impact of the recent advances in LTPS and AOS TFTs, R, G, B and White OLED with color filter pixel architectures, and encapsulation, on the success of the OLEDs in consumer electronic devices. We will then discuss potential of these advances in addressing the requirements of OLED and flexible displays for the military and avionics applications.

Graphene metamaterial spatial light modulator for infrared single pixel imaging.

PubMed

Fan, Kebin; Suen, Jonathan Y; Padilla, Willie J

2017-10-16

High-resolution and hyperspectral imaging has long been a goal for multi-dimensional data fusion sensing applications - of interest for autonomous vehicles and environmental monitoring. In the long wave infrared regime this quest has been impeded by size, weight, power, and cost issues, especially as focal-plane array detector sizes increase. Here we propose and experimentally demonstrated a new approach based on a metamaterial graphene spatial light modulator (GSLM) for infrared single pixel imaging. A frequency-division multiplexing (FDM) imaging technique is designed and implemented, and relies entirely on the electronic reconfigurability of the GSLM. We compare our approach to the more common raster-scan method and directly show FDM image frame rates can be 64 times faster with no degradation of image quality. Our device and related imaging architecture are not restricted to the infrared regime, and may be scaled to other bands of the electromagnetic spectrum. The study presented here opens a new approach for fast and efficient single pixel imaging utilizing graphene metamaterials with novel acquisition strategies.

Towards Development of Microcalorimeter Arrays of Mo/Au Transition-Edge Sensors with Bismuth Absorbers

NASA Technical Reports Server (NTRS)

Tralshawala, Nilesh; Brekosky, Regis; Figueroa-Feliciano, Enectali; Li, Mary; Stahle, Carl; Stahle, Caroline

2000-01-01

We report on our progress towards the development of arrays of X-ray microcalorimeters as candidates for the high resolution x-ray spectrometer on the Constellation-X mission. The microcalorimeter arrays (30 x 30) with appropriate pixel sizes (0.25 mm. x 0.25 mm) and high packing fractions (greater than 96%) are being developed. Each individual pixel has a 10 micron thick Bi X-ray absorber that is shaped like a mushroom to increase the packing fraction, and a Mo/Au proximity effect superconducting transition edge sensor (TES). These are deposited on a 0.25 or 0.5 micron thick silicon nitride membrane with slits to provide a controllable weak thermal link to the sink temperature. Studies are underway to model, test and optimize the TES pixel uniformity, critical current, heat capacity and the membrane thermal conductance in the array structure. Fabrication issues and procedures, and results of our efforts based on these optimizations will be provided.

Computational imaging with a balanced detector.

PubMed

Soldevila, F; Clemente, P; Tajahuerce, E; Uribe-Patarroyo, N; Andrés, P; Lancis, J

2016-06-29

Single-pixel cameras allow to obtain images in a wide range of challenging scenarios, including broad regions of the electromagnetic spectrum and through scattering media. However, there still exist several drawbacks that single-pixel architectures must address, such as acquisition speed and imaging in the presence of ambient light. In this work we introduce balanced detection in combination with simultaneous complementary illumination in a single-pixel camera. This approach enables to acquire information even when the power of the parasite signal is higher than the signal itself. Furthermore, this novel detection scheme increases both the frame rate and the signal-to-noise ratio of the system. By means of a fast digital micromirror device together with a low numerical aperture collecting system, we are able to produce a live-feed video with a resolution of 64 × 64 pixels at 5 Hz. With advanced undersampling techniques, such as compressive sensing, we can acquire information at rates of 25 Hz. By using this strategy, we foresee real-time biological imaging with large area detectors in conditions where array sensors are unable to operate properly, such as infrared imaging and dealing with objects embedded in turbid media.

Computational imaging with a balanced detector

NASA Astrophysics Data System (ADS)

Soldevila, F.; Clemente, P.; Tajahuerce, E.; Uribe-Patarroyo, N.; Andrés, P.; Lancis, J.

2016-06-01

Single-pixel cameras allow to obtain images in a wide range of challenging scenarios, including broad regions of the electromagnetic spectrum and through scattering media. However, there still exist several drawbacks that single-pixel architectures must address, such as acquisition speed and imaging in the presence of ambient light. In this work we introduce balanced detection in combination with simultaneous complementary illumination in a single-pixel camera. This approach enables to acquire information even when the power of the parasite signal is higher than the signal itself. Furthermore, this novel detection scheme increases both the frame rate and the signal-to-noise ratio of the system. By means of a fast digital micromirror device together with a low numerical aperture collecting system, we are able to produce a live-feed video with a resolution of 64 × 64 pixels at 5 Hz. With advanced undersampling techniques, such as compressive sensing, we can acquire information at rates of 25 Hz. By using this strategy, we foresee real-time biological imaging with large area detectors in conditions where array sensors are unable to operate properly, such as infrared imaging and dealing with objects embedded in turbid media.

Computational imaging with a balanced detector

PubMed Central

Soldevila, F.; Clemente, P.; Tajahuerce, E.; Uribe-Patarroyo, N.; Andrés, P.; Lancis, J.

2016-01-01

Single-pixel cameras allow to obtain images in a wide range of challenging scenarios, including broad regions of the electromagnetic spectrum and through scattering media. However, there still exist several drawbacks that single-pixel architectures must address, such as acquisition speed and imaging in the presence of ambient light. In this work we introduce balanced detection in combination with simultaneous complementary illumination in a single-pixel camera. This approach enables to acquire information even when the power of the parasite signal is higher than the signal itself. Furthermore, this novel detection scheme increases both the frame rate and the signal-to-noise ratio of the system. By means of a fast digital micromirror device together with a low numerical aperture collecting system, we are able to produce a live-feed video with a resolution of 64 × 64 pixels at 5 Hz. With advanced undersampling techniques, such as compressive sensing, we can acquire information at rates of 25 Hz. By using this strategy, we foresee real-time biological imaging with large area detectors in conditions where array sensors are unable to operate properly, such as infrared imaging and dealing with objects embedded in turbid media. PMID:27353733

Results from the NA62 Gigatracker Prototype: A Low-Mass and sub-ns Time Resolution Silicon Pixel Detector

NASA Astrophysics Data System (ADS)

Fiorini, M.; Rinella, G. Aglieri; Carassiti, V.; Ceccucci, A.; Gil, E. Cortina; Ramusino, A. Cotta; Dellacasa, G.; Garbolino, S.; Jarron, P.; Kaplon, J.; Kluge, A.; Marchetto, F.; Mapelli, A.; Martin, E.; Mazza, G.; Morel, M.; Noy, M.; Nuessle, G.; Petagna, P.; Petrucci, F.; Perktold, L.; Riedler, P.; Rivetti, A.; Statera, M.; Velghe, B.

The Gigatracker (GTK) is a hybrid silicon pixel detector developed for NA62, the experiment aimed at studying ultra-rare kaon decays at the CERN SPS. Three GTK stations will provide precise momentum and angular measurements on every track of the high intensity NA62 hadron beam with a time-tagging resolution of 150 ps. Multiple scattering and hadronic interactions of beam particles in the GTK have to be minimized to keep background events at acceptable levels, hence the total material budget is fixed to 0.5% X0 per station. In addition the calculated fluence for 100 days of running is 2×1014 1 MeV neq/cm2, comparable to the one expected for the inner trackers of LHC detectors in 10 years of operation. These requirements pose challenges for the development of an efficient and low-mass cooling system, to be operated in vacuum, and on the thinning of read-out chips to 100 μm or less. The most challenging requirement is represented by the time resolution, which can be achieved by carefully compensating for the discriminator time-walk. For this purpose, two complementary read-out architectures have been designed and produced as small-scale prototypes: the first is based on the use of a Time-over-Threshold circuit followed by a TDC shared by a group of pixels, while the other uses a constant-fraction discriminator followed by an on-pixel TDC. The readout pixel ASICs are produced in 130 nm IBM CMOS technology and bump-bonded to 200 μm thick silicon sensors. The Gigatracker detector system is described with particular emphasis on recent experimental results obtained from laboratory and beam tests of prototype bump-bonded assemblies, which show a time resolution of less than 200 ps for single hits.

High-density arrays of x-ray microcalorimeters for Constellation-X

NASA Astrophysics Data System (ADS)

Kilbourne, Caroline A.; Bandler, Simon R.; Brown, Ari D.; Chervenak, James A.; Figueroa-Feliciano, Enectali; Finkbeiner, Fred M.; Iyomoto, Naoko; Kelley, Richard L.; Porter, F. Scott; Saab, Tarek; Sadleir, John; White, Jennifer

2006-06-01

We have been developing x-ray microcalorimeters for the Constellation-X mission. Devices based on superconducting transition-edge sensors (TES) have demonstrated the potential to meet the Constellation-X requirements for spectral resolution, speed, and array scale (> 1000 pixels) in a close-packed geometry. In our part of the GSFC/NIST collaboration on this technology development, we have been concentrating on the fabrication of arrays of pixels suitable for the Constellation-X reference configuration. We have fabricated 8x8 arrays with 0.25-mm pixels arranged with 92% fill factor. The pixels are based on Mo/Au TES and Bi/Cu or Au/Bi absorbers. We have achieved a resolution of 4.0 eV FWHM at 6 keV in such devices, which meets the Constellation-X resolution requirement at 6 keV. Studies of the thermal transport in our Bi/Cu absorbers have shown that, while there is room for improvement, for 0.25-mm pixels the standard absorber design is adequate to avoid unacceptable line-broadening from position dependence caused by thermal diffusion. In order to improve reproducibility and to push closer to the 2-eV goal at 6 keV, however, we are refining the design of the TES and the interface to the absorber. Recent efforts to introduce a barrier layer between the Bi and the Mo/Au to avoid variable interface chemistry and thus improve the reproducibility of device characteristics have thus far yielded unsatisfactory results. However, we have developed a new set of absorber designs with contacts to the TES engineered to allow contact only in regions that do not serve as the active thermometer. We have further constrained the design so that a low-resistance absorber will not electrically short the TES. It is with such a design that we have achieved 4.0 eV resolution at 6 keV.

SAPHIRE (scintillator avalanche photoconductor with high resolution emitter readout) for low dose x-ray imaging: Spatial resolution

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li Dan; Zhao Wei

2008-07-15

An indirect flat panel imager (FPI) with programmable avalanche gain and field emitter array (FEA) readout is being investigated for low-dose and high resolution x-ray imaging. It is made by optically coupling a structured x-ray scintillator, e.g., thallium (Tl) doped cesium iodide (CsI), to an amorphous selenium (a-Se) avalanche photoconductor called high-gain avalanche rushing amorphous photoconductor (HARP). The charge image created by the scintillator/HARP (SHARP) combination is read out by the electron beams emitted from the FEA. The proposed detector is called scintillator avalanche photoconductor with high resolution emitter readout (SAPHIRE). The programmable avalanche gain of HARP can improve themore » low dose performance of indirect FPI while the FEA can be made with pixel sizes down to 50 {mu}m. Because of the avalanche gain, a high resolution type of CsI (Tl), which has not been widely used in indirect FPI due to its lower light output, can be used to improve the high spatial frequency performance. The purpose of the present article is to investigate the factors affecting the spatial resolution of SAPHIRE. Since the resolution performance of the SHARP combination has been well studied, the focus of the present work is on the inherent resolution of the FEA readout method. The lateral spread of the electron beam emitted from a 50 {mu}mx50 {mu}m pixel FEA was investigated with two different electron-optical designs: mesh-electrode-only and electrostatic focusing. Our results showed that electrostatic focusing can limit the lateral spread of electron beams to within the pixel size of down to 50 {mu}m. Since electrostatic focusing is essentially independent of signal intensity, it will provide excellent spatial uniformity.« less

1024-Pixel CMOS Multimodality Joint Cellular Sensor/Stimulator Array for Real-Time Holistic Cellular Characterization and Cell-Based Drug Screening.

PubMed

Park, Jong Seok; Aziz, Moez Karim; Li, Sensen; Chi, Taiyun; Grijalva, Sandra Ivonne; Sung, Jung Hoon; Cho, Hee Cheol; Wang, Hua

2018-02-01

This paper presents a fully integrated CMOS multimodality joint sensor/stimulator array with 1024 pixels for real-time holistic cellular characterization and drug screening. The proposed system consists of four pixel groups and four parallel signal-conditioning blocks. Every pixel group contains 16 × 16 pixels, and each pixel includes one gold-plated electrode, four photodiodes, and in-pixel circuits, within a pixel footprint. Each pixel supports real-time extracellular potential recording, optical detection, charge-balanced biphasic current stimulation, and cellular impedance measurement for the same cellular sample. The proposed system is fabricated in a standard 130-nm CMOS process. Rat cardiomyocytes are successfully cultured on-chip. Measured high-resolution optical opacity images, extracellular potential recordings, biphasic current stimulations, and cellular impedance images demonstrate the unique advantages of the system for holistic cell characterization and drug screening. Furthermore, this paper demonstrates the use of optical detection on the on-chip cultured cardiomyocytes to real-time track their cyclic beating pattern and beating rate.

Rapid Damage Assessment. Volume II. Development and Testing of Rapid Damage Assessment System.

DTIC Science & Technology

1981-02-01

pixels/s Camera Line Rate 732.4 lines/s Pixels per Line 1728 video 314 blank 4 line number (binary) 2 run number (BCD) 2048 total Pixel Resolution 8 bits...sists of an LSI-ll microprocessor, a VDI -200 video display processor, an FD-2 dual floppy diskette subsystem, an FT-I function key-trackball module...COMPONENT LIST FOR IMAGE PROCESSOR SYSTEM IMAGE PROCESSOR SYSTEM VIEWS I VDI -200 Display Processor Racks, Table FD-2 Dual Floppy Diskette Subsystem FT-l

The progress of sub-pixel imaging methods

NASA Astrophysics Data System (ADS)

Wang, Hu; Wen, Desheng

2014-02-01

This paper reviews the Sub-pixel imaging technology principles, characteristics, the current development status at home and abroad and the latest research developments. As Sub-pixel imaging technology has achieved the advantages of high resolution of optical remote sensor, flexible working ways and being miniaturized with no moving parts. The imaging system is suitable for the application of space remote sensor. Its application prospect is very extensive. It is quite possible to be the research development direction of future space optical remote sensing technology.

Performance comparison of small-pixel CdZnTe radiation detectors with gold contacts formed by sputter and electroless deposition

NASA Astrophysics Data System (ADS)

Bell, S. J.; Baker, M. A.; Duarte, D. D.; Schneider, A.; Seller, P.; Sellin, P. J.; Veale, M. C.; Wilson, M. D.

2017-06-01

Recent improvements in the growth of wide-bandgap semiconductors, such as cadmium zinc telluride (CdZnTe or CZT), has enabled spectroscopic X/γ-ray imaging detectors to be developed. These detectors have applications covering homeland security, industrial analysis, space science and medical imaging. At the Rutherford Appleton Laboratory (RAL) a promising range of spectroscopic, position sensitive, small-pixel Cd(Zn)Te detectors have been developed. The challenge now is to improve the quality of metal contacts on CdZnTe in order to meet the demanding energy and spatial resolution requirements of these applications. The choice of metal deposition method and fabrication process are of fundamental importance. Presented is a comparison of two CdZnTe detectors with contacts formed by sputter and electroless deposition. The detectors were fabricated with a 74 × 74 array of 200 μm pixels on a 250 μm pitch and bump-bonded to the HEXITEC ASIC. The X/γ-ray emissions from an 241Am source were measured to form energy spectra for comparison. It was found that the detector with contacts formed by electroless deposition produced the best uniformity and energy resolution; the best pixel produced a FWHM of 560 eV at 59.54 keV and 50% of pixels produced a FWHM better than 1.7 keV . This compared with a FWHM of 1.5 keV for the best pixel and 50% of pixels better than 4.4 keV for the detector with sputtered contacts.

Noise and spectroscopic performance of DEPMOSFET matrix devices for XEUS

NASA Astrophysics Data System (ADS)

Treis, J.; Fischer, P.; Hälker, O.; Herrmann, S.; Kohrs, R.; Krüger, H.; Lechner, P.; Lutz, G.; Peric, I.; Porro, M.; Richter, R. H.; Strüder, L.; Trimpl, M.; Wermes, N.; Wölfel, S.

2005-08-01

DEPMOSFET based Active Pixel Sensor (APS) matrix devices, originally developed to cope with the challenging requirements of the XEUS Wide Field Imager, have proven to be a promising new imager concept for a variety of future X-ray imaging and spectroscopy missions like Simbol-X. The devices combine excellent energy resolution, high speed readout and low power consumption with the attractive feature of random accessibility of pixels. A production of sensor prototypes with 64 x 64 pixels with a size of 75 μm x 75 μm each has recently been finished at the MPI semiconductor laboratory in Munich. The devices are built for row-wise readout and require dedicated control and signal processing electronics of the CAMEX type, which is integrated together with the sensor onto a readout hybrid. A number of hybrids incorporating the most promising sensor design variants has been built, and their performance has been studied in detail. A spectroscopic resolution of 131 eV has been measured, the readout noise is as low as 3.5 e- ENC. Here, the dependence of readout noise and spectroscopic resolution on the device temperature is presented.

A Method of Spatial Mapping and Reclassification for High-Spatial-Resolution Remote Sensing Image Classification

PubMed Central

Wang, Guizhou; Liu, Jianbo; He, Guojin

2013-01-01

This paper presents a new classification method for high-spatial-resolution remote sensing images based on a strategic mechanism of spatial mapping and reclassification. The proposed method includes four steps. First, the multispectral image is classified by a traditional pixel-based classification method (support vector machine). Second, the panchromatic image is subdivided by watershed segmentation. Third, the pixel-based multispectral image classification result is mapped to the panchromatic segmentation result based on a spatial mapping mechanism and the area dominant principle. During the mapping process, an area proportion threshold is set, and the regional property is defined as unclassified if the maximum area proportion does not surpass the threshold. Finally, unclassified regions are reclassified based on spectral information using the minimum distance to mean algorithm. Experimental results show that the classification method for high-spatial-resolution remote sensing images based on the spatial mapping mechanism and reclassification strategy can make use of both panchromatic and multispectral information, integrate the pixel- and object-based classification methods, and improve classification accuracy. PMID:24453808

Coded aperture detector: an image sensor with sub 20-nm pixel resolution.

PubMed

Miyakawa, Ryan; Mayer, Rafael; Wojdyla, Antoine; Vannier, Nicolas; Lesser, Ian; Aron-Dine, Shifrah; Naulleau, Patrick

2014-08-11

We describe the coded aperture detector, a novel image sensor based on uniformly redundant arrays (URAs) with customizable pixel size, resolution, and operating photon energy regime. In this sensor, a coded aperture is scanned laterally at the image plane of an optical system, and the transmitted intensity is measured by a photodiode. The image intensity is then digitally reconstructed using a simple convolution. We present results from a proof-of-principle optical prototype, demonstrating high-fidelity image sensing comparable to a CCD. A 20-nm half-pitch URA fabricated by the Center for X-ray Optics (CXRO) nano-fabrication laboratory is presented that is suitable for high-resolution image sensing at EUV and soft X-ray wavelengths.

Solar XUV Imaging and Non-dispersive Spectroscopy for Solar-C Enabled by Scientific CMOS APS Arrays

NASA Astrophysics Data System (ADS)

Stern, Robert A.; Lemen, J. R.; Shing, L.; Janesick, J.; Tower, J.

2009-05-01

Monolithic CMOS Advanced Pixel Sensor (APS) arrays are showing great promise as eventual replacements for the current workhorse of solar physics focal planes, the scientific CCD. CMOS APS devices have individually addressable pixels, increased radiation tolerance compared to CCDs, and require lower clock voltages, and thus lower power. However, commercially available CMOS chips, while suitable for use with intensifiers or fluorescent coatings, are generally not optimized for direct detection of EUV and X-ray photons. A high performance scientific CMOS array designed for these wavelengths will have significant new capabilities compared to CCDs, including the ability to read out small regions of the solar disk at high (sub sec) cadence, count single X-ray photons with Fano-limited energy resolution, and even operate at room temperature with good noise performance. Such capabilities will be crucial for future solar X-ray and EUV missions such as Solar-C. Sarnoff Corporation has developed scientific grade, monolithic CMOS arrays for X-ray imaging and photon counting. One prototype device, the "minimal" array, has 8 um pixels, is 15 to 25 um thick, is fabricated on high-resistivity ( 10 to 20 kohm-cm) Si wafers, and can be back-illuminated. These characteristics yield high quantum efficiency and high spatial resolution with minimal charge sharing among pixels, making it ideal for the detection of keV X-rays. When used with digital correlated double sampling, the array has demonstrated noise performance as low as 2 e, allowing single photon counting of X-rays over a range of temperatures. We report test results for this device in X-rays, and discuss the implications for future solar space missions.

Rapid Disaster Damage Estimation

NASA Astrophysics Data System (ADS)

Vu, T. T.

2012-07-01

The experiences from recent disaster events showed that detailed information derived from high-resolution satellite images could accommodate the requirements from damage analysts and disaster management practitioners. Richer information contained in such high-resolution images, however, increases the complexity of image analysis. As a result, few image analysis solutions can be practically used under time pressure in the context of post-disaster and emergency responses. To fill the gap in employment of remote sensing in disaster response, this research develops a rapid high-resolution satellite mapping solution built upon a dual-scale contextual framework to support damage estimation after a catastrophe. The target objects are building (or building blocks) and their condition. On the coarse processing level, statistical region merging deployed to group pixels into a number of coarse clusters. Based on majority rule of vegetation index, water and shadow index, it is possible to eliminate the irrelevant clusters. The remaining clusters likely consist of building structures and others. On the fine processing level details, within each considering clusters, smaller objects are formed using morphological analysis. Numerous indicators including spectral, textural and shape indices are computed to be used in a rule-based object classification. Computation time of raster-based analysis highly depends on the image size or number of processed pixels in order words. Breaking into 2 level processing helps to reduce the processed number of pixels and the redundancy of processing irrelevant information. In addition, it allows a data- and tasks- based parallel implementation. The performance is demonstrated with QuickBird images captured a disaster-affected area of Phanga, Thailand by the 2004 Indian Ocean tsunami are used for demonstration of the performance. The developed solution will be implemented in different platforms as well as a web processing service for operational uses.

Determination of target detection limits in hyperspectral data using band selection and dimensionality reduction

NASA Astrophysics Data System (ADS)

Gross, W.; Boehler, J.; Twizer, K.; Kedem, B.; Lenz, A.; Kneubuehler, M.; Wellig, P.; Oechslin, R.; Schilling, H.; Rotman, S.; Middelmann, W.

2016-10-01

Hyperspectral remote sensing data can be used for civil and military applications to robustly detect and classify target objects. High spectral resolution of hyperspectral data can compensate for the comparatively low spatial resolution, which allows for detection and classification of small targets, even below image resolution. Hyperspectral data sets are prone to considerable spectral redundancy, affecting and limiting data processing and algorithm performance. As a consequence, data reduction strategies become increasingly important, especially in view of near-real-time data analysis. The goal of this paper is to analyze different strategies for hyperspectral band selection algorithms and their effect on subpixel classification for different target and background materials. Airborne hyperspectral data is used in combination with linear target simulation procedures to create a representative amount of target-to-background ratios for evaluation of detection limits. Data from two different airborne hyperspectral sensors, AISA Eagle and Hawk, are used to evaluate transferability of band selection when using different sensors. The same target objects were recorded to compare the calculated detection limits. To determine subpixel classification results, pure pixels from the target materials are extracted and used to simulate mixed pixels with selected background materials. Target signatures are linearly combined with different background materials in varying ratios. The commonly used classification algorithms Adaptive Coherence Estimator (ACE) is used to compare the detection limit for the original data with several band selection and data reduction strategies. The evaluation of the classification results is done by assuming a fixed false alarm ratio and calculating the mean target-to-background ratio of correctly detected pixels. The results allow drawing conclusions about specific band combinations for certain target and background combinations. Additionally, generally useful wavelength ranges are determined and the optimal amount of principal components is analyzed.

The NASA/GEWEX Surface Radiation Budget: Integrated Data Product With Reprocessed Radiance, Cloud, and Meteorology Inputs

NASA Astrophysics Data System (ADS)

Stackhouse, P. W.; Gupta, S. K.; Cox, S. J.; Mikovitz, J. C.; Zhang, T.

2015-12-01

The NASA/GEWEX Surface Radiation Budget (SRB) project produces shortwave and longwave surface and top of atmosphere radiative fluxes for the 1983-near present time period. Spatial resolution is 1 degree. The current release 3.0 (available at gewex-srb.larc.nasa.gov) uses the International Satellite Cloud Climatology Project (ISCCP) DX product for pixel level radiance and cloud information. This product is subsampled to 30 km. ISCCP is currently recalibrating and recomputing their entire data series, to be released as the H product, at 10km resolution. The ninefold increase in pixel number will allow SRB a higher resolution gridded product (e.g. 0.5 degree), as well as the production of pixel-level fluxes. Other key input improvements include a detailed aerosol history using the Max Planck Institut Aerosol Climatology (MAC), temperature and moisture profiles from HIRS, and new topography, surface type, and snow/ice. At the time of abstract submission, results from the year 2007 have been produced. More years will be added as ISCCP reprocessing occurs. Here we present results for the improved GEWEX Shortwave and Longwave algorithm (GSW and GLW) with new ISCCP data, the various other improved input data sets and the incorporation of many additional internal SRB model improvements. Improvements in GSW include an expansion of the number of wavelength bands from five to eighteen, and the inclusion of ice cloud vs. water cloud radiative transfer. The SRB data produced will be released as part of the Release 4.0 Integrated Product, recognizing the interdependence of the radiative fluxes with other GEWEX products providing estimates of the Earth's global water and energy cycle (I.e., ISCCP, SeaFlux, LandFlux, NVAP, etc.).

Assessing land cover performance in Senegal, West Africa using 1-km integrated NDVI and local variance analysis

USGS Publications Warehouse

Budde, M.E.; Tappan, G.; Rowland, James; Lewis, J.; Tieszen, L.L.

2004-01-01

The researchers calculated seasonal integrated normalized difference vegetation index (NDVI) for each of 7 years using a time-series of 1-km data from the Advanced Very High Resolution Radiometer (AVHRR) (1992-93, 1995) and SPOT Vegetation (1998-2001) sensors. We used a local variance technique to identify each pixel as normal or either positively or negatively anomalous when compared to its surroundings. We then summarized the number of years that a given pixel was identified as an anomaly. The resulting anomaly maps were analysed using Landsat TM imagery and extensive ground knowledge to assess the results. This technique identified anomalies that can be linked to numerous anthropogenic impacts including agricultural and urban expansion, maintenance of protected areas and increased fallow. Local variance analysis is a reliable method for assessing vegetation degradation resulting from human pressures or increased land productivity from natural resource management practices. ?? 2004 Published by Elsevier Ltd.

Modeling and evaluation of a high-resolution CMOS detector for cone-beam CT of the extremities.

PubMed

Cao, Qian; Sisniega, Alejandro; Brehler, Michael; Stayman, J Webster; Yorkston, John; Siewerdsen, Jeffrey H; Zbijewski, Wojciech

2018-01-01

Quantitative assessment of trabecular bone microarchitecture in extremity cone-beam CT (CBCT) would benefit from the high spatial resolution, low electronic noise, and fast scan time provided by complementary metal-oxide semiconductor (CMOS) x-ray detectors. We investigate the performance of CMOS sensors in extremity CBCT, in particular with respect to potential advantages of thin (<0.7 mm) scintillators offering higher spatial resolution. A cascaded systems model of a CMOS x-ray detector incorporating the effects of CsI:Tl scintillator thickness was developed. Simulation studies were performed using nominal extremity CBCT acquisition protocols (90 kVp, 0.126 mAs/projection). A range of scintillator thickness (0.35-0.75 mm), pixel size (0.05-0.4 mm), focal spot size (0.05-0.7 mm), magnification (1.1-2.1), and dose (15-40 mGy) was considered. The detectability index was evaluated for both CMOS and a-Si:H flat-panel detector (FPD) configurations for a range of imaging tasks emphasizing spatial frequencies associated with feature size aobj. Experimental validation was performed on a CBCT test bench in the geometry of a compact orthopedic CBCT system (SAD = 43.1 cm, SDD = 56.0 cm, matching that of the Carestream OnSight 3D system). The test-bench studies involved a 0.3 mm focal spot x-ray source and two CMOS detectors (Dalsa Xineos-3030HR, 0.099 mm pixel pitch) - one with the standard CsI:Tl thickness of 0.7 mm (C700) and one with a custom 0.4 mm thick scintillator (C400). Measurements of modulation transfer function (MTF), detective quantum efficiency (DQE), and CBCT scans of a cadaveric knee (15 mGy) were obtained for each detector. Optimal detectability for high-frequency tasks (feature size of ~0.06 mm, consistent with the size of trabeculae) was ~4× for the C700 CMOS detector compared to the a-Si:H FPD at nominal system geometry of extremity CBCT. This is due to ~5× lower electronic noise of a CMOS sensor, which enables input quantum-limited imaging at smaller pixel size. Optimal pixel size for high-frequency tasks was <0.1 mm for a CMOS, compared to ~0.14 mm for an a-Si:H FPD. For this fine pixel pitch, detectability of fine features could be improved by using a thinner scintillator to reduce light spread blur. A 22% increase in detectability of 0.06 mm features was found for the C400 configuration compared to C700. An improvement in the frequency at 50% modulation (f 50 ) of MTF was measured, increasing from 1.8 lp/mm for C700 to 2.5 lp/mm for C400. The C400 configuration also achieved equivalent or better DQE as C700 for frequencies above ~2 mm -1 . Images of cadaver specimens confirmed improved visualization of trabeculae with the C400 sensor. The small pixel size of CMOS detectors yields improved performance in high-resolution extremity CBCT compared to a-Si:H FPDs, particularly when coupled with a custom 0.4 mm thick scintillator. The results indicate that adoption of a CMOS detector in extremity CBCT can benefit applications in quantitative imaging of trabecular microstructure in humans. © 2017 American Association of Physicists in Medicine.

Super-resolved refocusing with a plenoptic camera

NASA Astrophysics Data System (ADS)

Zhou, Zhiliang; Yuan, Yan; Bin, Xiangli; Qian, Lulu

2011-03-01

This paper presents an approach to enhance the resolution of refocused images by super resolution methods. In plenoptic imaging, we demonstrate that the raw sensor image can be divided to a number of low-resolution angular images with sub-pixel shifts between each other. The sub-pixel shift, which defines the super-resolving ability, is mathematically derived by considering the plenoptic camera as equivalent camera arrays. We implement simulation to demonstrate the imaging process of a plenoptic camera. A high-resolution image is then reconstructed using maximum a posteriori (MAP) super resolution algorithms. Without other degradation effects in simulation, the super resolved image achieves a resolution as high as predicted by the proposed model. We also build an experimental setup to acquire light fields. With traditional refocusing methods, the image is rendered at a rather low resolution. In contrast, we implement the super-resolved refocusing methods and recover an image with more spatial details. To evaluate the performance of the proposed method, we finally compare the reconstructed images using image quality metrics like peak signal to noise ratio (PSNR).

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dragone, A; /SLAC; Pratte, J.F.

An ASIC for the readout of signals from X-ray Active Matrix Pixel Sensor (XAMPS) detectors to be used at the Linac Coherent Light Source (LCLS) is presented. The X-ray Pump Probe (XPP) instrument, for which the ASIC has been designed, requires a large input dynamic range on the order of 104 photons at 8 keV with a resolution of half a photon FWHM. Due to the size of the pixel and the length of the readout line, large input capacitance is expected, leading to stringent requirement on the noise optimization. Furthermore, the large number of pixels needed for a goodmore » position resolution and the fixed LCLS beam period impose limitations on the time available for the single pixel readout. Considering the periodic nature of the LCLS beam, the ASIC developed for this application is a time-variant system providing low-noise charge integration, filtering and correlated double sampling. In order to cope with the large input dynamic range a charge pump scheme implementing a zero-balance measurement method has been introduced. It provides an on chip 3-bit coarse digital conversion of the integrated charge. The residual charge is sampled using correlated double sampling into analog memory and measured with the required resolution. The first 64 channel prototype of the ASIC has been fabricated in TSMC CMOS 0.25 {micro}m technology. In this paper, the ASIC architecture and performances are presented.« less

Satellite monitoring of cyanobacterial harmful algal bloom ...

EPA Pesticide Factsheets

Cyanobacterial harmful algal blooms (cyanoHABs) cause extensive problems in lakes worldwide, including human and ecological health risks, anoxia and fish kills, and taste and odor problems. CyanoHABs are a particular concern because of their dense biomass and the risk of exposure to toxins in both recreational waters and drinking source waters. Successful cyanoHAB assessment by satellites may provide a first-line of defense indicator for human and ecological health protection. In this study, assessment methods were developed to determine the utility of satellite technology for detecting cyanoHAB occurrence frequency at locations of potential management interest. The European Space Agency's MEdium Resolution Imaging Spectrometer (MERIS) was evaluated to prepare for the equivalent Sentinel-3 Ocean and Land Colour Imager (OLCI) launched in 2016. Based on the 2012 National Lakes Assessment site evaluation guidelines and National Hydrography Dataset, there were 275,897 lakes and reservoirs greater than 1 hectare in the 48 U.S. states. Results from this evaluation show that 5.6 % of waterbodies were resolvable by satellites with 300 m single pixel resolution and 0.7 % of waterbodies were resolvable when a 3x3 pixel array was applied based on minimum Euclidian distance from shore. Satellite data was also spatially joined to US public water surface intake (PWSI) locations, where single pixel resolution resolved 57% of PWSI and a 3x3 pixel array resolved 33% of

On the performance of large monolithic LaCl3(Ce) crystals coupled to pixelated silicon photosensors

NASA Astrophysics Data System (ADS)

Olleros, P.; Caballero, L.; Domingo-Pardo, C.; Babiano, V.; Ladarescu, I.; Calvo, D.; Gramage, P.; Nacher, E.; Tain, J. L.; Tolosa, A.

2018-03-01

We investigate the performance of large area radiation detectors, with high energy- and spatial-resolution, intended for the development of a Total Energy Detector with gamma-ray imaging capability, so-called i-TED. This new development aims for an enhancement in detection sensitivity in time-of-flight neutron capture measurements, versus the commonly used C6D6 liquid scintillation total-energy detectors. In this work, we study in detail the impact of the readout photosensor on the energy response of large area (50×50 mm2) monolithic LaCl3(Ce) crystals, in particular when replacing a conventional mono-cathode photomultiplier tube by an 8×8 pixelated silicon photomultiplier. Using the largest commercially available monolithic SiPM array (25 cm2), with a pixel size of 6×6 mm2, we have measured an average energy resolution of 3.92% FWHM at 662 keV for crystal thicknesses of 10, 20 and 30 mm. The results are confronted with detailed Monte Carlo (MC) calculations, where optical processes and properties have been included for the reliable tracking of the scintillation photons. After the experimental validation of the MC model, we use our MC code to explore the impact of a smaller photosensor segmentation on the energy resolution. Our optical MC simulations predict only a marginal deterioration of the spectroscopic performance for pixels of 3×3 mm2.

Pixel-level tunable liquid crystal lenses for auto-stereoscopic display

NASA Astrophysics Data System (ADS)

Li, Kun; Robertson, Brian; Pivnenko, Mike; Chu, Daping; Zhou, Jiong; Yao, Jun

2014-02-01

Mobile video and gaming are now widely used, and delivery of a glass-free 3D experience is of both research and development interest. The key drawbacks of a conventional 3D display based on a static lenticular lenslet array and parallax barriers are low resolution, limited viewing angle and reduced brightness, mainly because of the need of multiple-pixels for each object point. This study describes the concept and performance of pixel-level cylindrical liquid crystal (LC) lenses, which are designed to steer light to the left and right eye sequentially to form stereo parallax. The width of the LC lenses can be as small as 20-30 μm, so that the associated auto-stereoscopic display will have the same resolution as the 2D display panel in use. Such a thin sheet of tunable LC lens array can be applied directly on existing mobile displays, and can deliver 3D viewing experience while maintaining 2D viewing capability. Transparent electrodes were laser patterned to achieve the single pixel lens resolution, and a high birefringent LC material was used to realise a large diffraction angle for a wide field of view. Simulation was carried out to model the intensity profile at the viewing plane and optimise the lens array based on the measured LC phase profile. The measured viewing angle and intensity profile were compared with the simulation results.

In-depth study of single photon time resolution for the Philips digital silicon photomultiplier

NASA Astrophysics Data System (ADS)

Liu, Z.; Gundacker, S.; Pizzichemi, M.; Ghezzi, A.; Auffray, E.; Lecoq, P.; Paganoni, M.

2016-06-01

The digital silicon photomultiplier (SiPM) has been commercialised by Philips as an innovative technology compared to analog silicon photomultiplier devices. The Philips digital SiPM, has a pair of time to digital converters (TDCs) connected to 12800 single photon avalanche diodes (SPADs). Detailed measurements were performed to understand the low photon time response of the Philips digital SiPM. The single photon time resolution (SPTR) of every single SPAD in a pixel consisting of 3200 SPADs was measured and an average value of 85 ps full width at half maximum (FWHM) was observed. Each SPAD sends the signal to the TDC with different signal propagation time, resulting in a so called trigger network skew. This distribution of the trigger network skew for a pixel (3200 SPADs) has been measured and a variation of 50 ps FWHM was extracted. The SPTR of the whole pixel is the combination of SPAD jitter, trigger network skew, and the SPAD non-uniformity. The SPTR of a complete pixel was 103 ps FWHM at 3.3 V above breakdown voltage. Further, the effect of the crosstalk at a low photon level has been studied, with the two photon time resolution degrading if the events are a combination of detected (true) photons and crosstalk events. Finally, the time response to multiple photons was investigated.

Pixel Paradise

NASA Technical Reports Server (NTRS)

1998-01-01

PixelVision, Inc., has developed a series of integrated imaging engines capable of high-resolution image capture at dynamic speeds. This technology was used originally at Jet Propulsion Laboratory in a series of imaging engines for a NASA mission to Pluto. By producing this integrated package, Charge-Coupled Device (CCD) technology has been made accessible to a wide range of users.

DOE Office of Scientific and Technical Information (OSTI.GOV)

DE GERONIMO,G.; CHEN, W.; FRIED, J.

We present an application specific integrated circuit (ASIC) for high-resolution x-ray spectrometers. The ASIC is designed to read out signals from a pixelated silicon drift detector (SDD). Each hexagonal pixel has an area of 15 mmz and an anode capacitance of less than 100 fF. There is no integrated Field Effect transistor (FET) in the pixel, rather, the readout is done by wirebonding the anodes to the inputs of the ASIC. The ASIC provides 14 channels of low-noise charge amplification, high-order shaping with baseline stabilization, and peak detection with analog memory. The readout is sparse and based on low voltagemore » differential signaling. An interposer provides all the interconnections required to bias and operate the system. The channel dissipates 1.6 mW. The complete 14-pixel unit covers an area of 210 mm{sup 2}, dissipates 12 mW cm{sup -2}, and can be tiled to cover an arbitrarily large detection area. We measured a preliminary resolution of 172 eV at -35 C on the 6 keV peak of a {sup 55}Fe source.« less

Efficient phase contrast imaging in STEM using a pixelated detector. Part 1: Experimental demonstration at atomic resolution

DOE PAGES

Pennycook, Timothy J.; Lupini, Andrew R.; Yang, Hao; ...

2014-10-15

In this paper, we demonstrate a method to achieve high efficiency phase contrast imaging in aberration corrected scanning transmission electron microscopy (STEM) with a pixelated detector. The pixelated detector is used to record the Ronchigram as a function of probe position which is then analyzed with ptychography. Ptychography has previously been used to provide super-resolution beyond the diffraction limit of the optics, alongside numerically correcting for spherical aberration. Here we rely on a hardware aberration corrector to eliminate aberrations, but use the pixelated detector data set to utilize the largest possible volume of Fourier space to create high efficiency phasemore » contrast images. The use of ptychography to diagnose the effects of chromatic aberration is also demonstrated. In conclusion, the four dimensional dataset is used to compare different bright field detector configurations from the same scan for a sample of bilayer graphene. Our method of high efficiency ptychography produces the clearest images, while annular bright field produces almost no contrast for an in-focus aberration-corrected probe.« less

Design and characterization of the ePix10k: a high dynamic range integrating pixel ASIC for LCLS detectors

NASA Astrophysics Data System (ADS)

Caragiulo, P.; Dragone, A.; Markovic, B.; Herbst, R.; Nishimura, K.; Reese, B.; Herrmann, S.; Hart, P.; Blaj, G.; Segal, J.; Tomada, A.; Hasi, J.; Carini, G.; Kenney, C.; Haller, G.

2015-05-01

ePix10k is a variant of a novel class of integrating pixel ASICs architectures optimized for the processing of signals in second generation LINAC Coherent Light Source (LCLS) X-Ray cameras. The ASIC is optimized for high dynamic range application requiring high spatial resolution and fast frame rates. ePix ASICs are based on a common platform composed of a random access analog matrix of pixel with global shutter, fast parallel column readout, and dedicated sigma-delta analog to digital converters per column. The ePix10k variant has 100um×100um pixels arranged in a 176×192 matrix, a resolution of 140e- r.m.s. and a signal range of 3.5pC (10k photons at 8keV). In its final version it will be able to sustain a frame rate of 2kHz. A first prototype has been fabricated and characterized. Performance in terms of noise, linearity, uniformity, cross-talk, together with preliminary measurements with bump bonded sensors are reported here.

Quantification of the Conditioning Phase in Cooled Pixelated TlBr Detectors

NASA Astrophysics Data System (ADS)

Koehler, Will; He, Zhong; O'Neal, Sean; Yang, Hao; Kim, Hadong; Cirignano, Leonard; Shah, Kanai

2015-08-01

Thallium-bromide (TlBr) is currently under investigation as an alternative room-temperature semiconductor gamma-ray spectrometer due to its favorable material properties (large bandgap, high atomic numbers, and high density). Previous work has shown that 5 mm thick pixelated TlBr detectors can achieve sub-1% FWHM energy resolution at 662 keV for single-pixel events. These results are limited to - 20° C operation where detector performance is stable. During the first one to five days of applied bias at - 20° C, many TlBr detectors undergo a conditioning phase, where the energy resolution improves and the depth-dependent electron drift velocity stabilizes. In this work, the spectroscopic performance, drift velocity, and freed electron concentrations of multiple 5 mm thick pixelated TlBr detectors are monitored throughout the conditioning phase. Additionally, conditioning is performed twice on the same detector at different times to show that improvement mechanisms relax when the detector is stored without bias. We conclude that the improved spectroscopy results from internal electric field stabilization and uniformity caused by fewer trapped electrons.

Investigation of CMOS pixel sensor with 0.18 μm CMOS technology for high-precision tracking detector

NASA Astrophysics Data System (ADS)

Zhang, L.; Fu, M.; Zhang, Y.; Yan, W.; Wang, M.

2017-01-01

The Circular Electron Positron Collider (CEPC) proposed by the Chinese high energy physics community is aiming to measure Higgs particles and their interactions precisely. The tracking detector including Silicon Inner Tracker (SIT) and Forward Tracking Disks (FTD) has driven stringent requirements on sensor technologies in term of spatial resolution, power consumption and readout speed. CMOS Pixel Sensor (CPS) is a promising candidate to approach these requirements. This paper presents the preliminary studies on the sensor optimization for tracking detector to achieve high collection efficiency while keeping necessary spatial resolution. Detailed studies have been performed on the charge collection using a 0.18 μm CMOS image sensor process. This process allows high resistivity epitaxial layer, leading to a significant improvement on the charge collection and therefore improving the radiation tolerance. Together with the simulation results, the first exploratory prototype has bee designed and fabricated. The prototype includes 9 different pixel arrays, which vary in terms of pixel pitch, diode size and geometry. The total area of the prototype amounts to 2 × 7.88 mm2.

The Belle-II Depfet Pixel Detector at the Superkekb Flavour Factory

NASA Astrophysics Data System (ADS)

Heindl, Stefan

2012-08-01

The ongoing upgrade of the asymmetric electron positron collider KEKB also requires extensive detector upgrades to cope with the new design luminosity of 8 · 1035 cm-2 · s-1 · Of critical importance is the new silicon pixel vertex tracker, which will significantly improve the decay vertex resolution, crucial for time dependent CP violation measurements. This new detector will consist of two layers of DEPFET pixel seii8ors very close to the interaction point. These sensors combine both particle detection and amplification of the signal by embedding a field effect transistor into a 75 μm thick fully depleted silicon substrate, providing very high signal to noise ratios and excellent spatial resolution. Using this technology satisfies the given requirements of extremely low material and high radiation tolerance at the new Belle II experiment. The power dissipation due to continuous readout at high rate and spatial constraints also give strict requirements for the mechanical support and cooling of the new detector. We will discuss the overall concept of the pixel vertex tracker, its expected performance and the challenging mechanical integration.

A detailed comparison of single-camera light-field PIV and tomographic PIV

NASA Astrophysics Data System (ADS)

Shi, Shengxian; Ding, Junfei; Atkinson, Callum; Soria, Julio; New, T. H.

2018-03-01

This paper conducts a comprehensive study between the single-camera light-field particle image velocimetry (LF-PIV) and the multi-camera tomographic particle image velocimetry (Tomo-PIV). Simulation studies were first performed using synthetic light-field and tomographic particle images, which extensively examine the difference between these two techniques by varying key parameters such as pixel to microlens ratio (PMR), light-field camera Tomo-camera pixel ratio (LTPR), particle seeding density and tomographic camera number. Simulation results indicate that the single LF-PIV can achieve accuracy consistent with that of multi-camera Tomo-PIV, but requires the use of overall greater number of pixels. Experimental studies were then conducted by simultaneously measuring low-speed jet flow with single-camera LF-PIV and four-camera Tomo-PIV systems. Experiments confirm that given a sufficiently high pixel resolution, a single-camera LF-PIV system can indeed deliver volumetric velocity field measurements for an equivalent field of view with a spatial resolution commensurate with those of multi-camera Tomo-PIV system, enabling accurate 3D measurements in applications where optical access is limited.

Effects of Cloud Horizontal Inhomogeneity and Drizzle on Remote Sensing of Cloud Droplet Effective Radius: Case Studies Based on Large-eddy Simulations

NASA Technical Reports Server (NTRS)

Zhang, Zhibo; Ackerman, Andrew S.; Feingold, Graham; Platnick, Steven; Pincus, Robert; Xue, Huiwen

2012-01-01

This study investigates effects of drizzle and cloud horizontal inhomogeneity on cloud effective radius (re) retrievals from the Moderate Resolution Imaging Spectroradiometer (MODIS). In order to identify the relative importance of various factors, we developed a MODIS cloud property retrieval simulator based on the combination of large-eddy simulations (LES) and radiative transfer computations. The case studies based on synthetic LES cloud fields indicate that at high spatial resolution (100 m) 3-D radiative transfer effects, such as illumination and shadowing, can induce significant differences between retrievals ofre based on reflectance at 2.1 m (re,2.1) and 3.7 m (re,3.7). It is also found that 3-D effects tend to have stronger impact onre,2.1 than re,3.7, leading to positive difference between the two (re,3.72.1) from illumination and negative re,3.72.1from shadowing. The cancellation of opposing 3-D effects leads to overall reasonable agreement betweenre,2.1 and re,3.7 at high spatial resolution as far as domain averages are concerned. At resolutions similar to MODIS, however, re,2.1 is systematically larger than re,3.7when averaged over the LES domain, with the difference exhibiting a threshold-like dependence on bothre,2.1and an index of the sub-pixel variability in reflectance (H), consistent with MODIS observations. In the LES cases studied, drizzle does not strongly impact reretrievals at either wavelength. It is also found that opposing 3-D radiative transfer effects partly cancel each other when cloud reflectance is aggregated from high spatial resolution to MODIS resolution, resulting in a weaker net impact of 3-D radiative effects onre retrievals. The large difference at MODIS resolution between re,3.7 and re,2.1 for highly inhomogeneous pixels with H 0.4 can be largely attributed to what we refer to as the plane-parallelrebias, which is attributable to the impact of sub-pixel level horizontal variability of cloud optical thickness onre retrievals and is greater for re,2.1 than re,3.7. These results suggest that there are substantial uncertainties attributable to 3-D radiative effects and plane-parallelre bias in the MODIS re,2.1retrievals for pixels with strong sub-pixel scale variability, and theH index can be used to identify these uncertainties.

A MAP-based image interpolation method via Viterbi decoding of Markov chains of interpolation functions.

PubMed

Vedadi, Farhang; Shirani, Shahram

2014-01-01

A new method of image resolution up-conversion (image interpolation) based on maximum a posteriori sequence estimation is proposed. Instead of making a hard decision about the value of each missing pixel, we estimate the missing pixels in groups. At each missing pixel of the high resolution (HR) image, we consider an ensemble of candidate interpolation methods (interpolation functions). The interpolation functions are interpreted as states of a Markov model. In other words, the proposed method undergoes state transitions from one missing pixel position to the next. Accordingly, the interpolation problem is translated to the problem of estimating the optimal sequence of interpolation functions corresponding to the sequence of missing HR pixel positions. We derive a parameter-free probabilistic model for this to-be-estimated sequence of interpolation functions. Then, we solve the estimation problem using a trellis representation and the Viterbi algorithm. Using directional interpolation functions and sequence estimation techniques, we classify the new algorithm as an adaptive directional interpolation using soft-decision estimation techniques. Experimental results show that the proposed algorithm yields images with higher or comparable peak signal-to-noise ratios compared with some benchmark interpolation methods in the literature while being efficient in terms of implementation and complexity considerations.

Kilopixel X-Ray Microcalorimeter Arrays for Astrophysics: Device Performance and Uniformity

NASA Technical Reports Server (NTRS)

Eckart, M. E.; Adams, J. S.; Bailey, C. N.; Bandler, S. R.; Busch, S. E.; Chervenak, J. A.; Finkbeiner, F. M.; Kelley, R. L.; Kilbourne, C. A.; Porter, F. S.;

Development of depth encoding small animal PET detectors using dual-ended readout of pixelated scintillator arrays with SiPMs.

PubMed

Kuang, Zhonghua; Sang, Ziru; Wang, Xiaohui; Fu, Xin; Ren, Ning; Zhang, Xianming; Zheng, Yunfei; Yang, Qian; Hu, Zhanli; Du, Junwei; Liang, Dong; Liu, Xin; Zheng, Hairong; Yang, Yongfeng

2018-02-01

The performance of current small animal PET scanners is mainly limited by the detector performance and depth encoding detectors are required to develop PET scanner to simultaneously achieve high spatial resolution and high sensitivity. Among all depth encoding PET detector approaches, dual-ended readout detector has the advantage to achieve the highest depth of interaction (DOI) resolution and spatial resolution. Silicon photomultiplier (SiPM) is believed to be the photodetector of the future for PET detector due to its excellent properties as compared to the traditional photodetectors such as photomultiplier tube (PMT) and avalanche photodiode (APD). The purpose of this work is to develop high resolution depth encoding small animal PET detector using dual-ended readout of finely pixelated scintillator arrays with SiPMs. Four lutetium-yttrium oxyorthosilicate (LYSO) arrays with 11 × 11 crystals and 11.6 × 11.6 × 20 mm 3 outside dimension were made using ESR, Toray and BaSO 4 reflectors. The LYSO arrays were read out with Hamamatsu 4 × 4 SiPM arrays from both ends. The SiPM array has a pixel size of 3 × 3 mm 2 , 0.2 mm gap in between the pixels and a total active area of 12.6 × 12.6 mm 2 . The flood histograms, DOI resolution, energy resolution and timing resolution of the four detector modules were measured and compared. All crystals can be clearly resolved from the measured flood histograms of all four arrays. The BaSO 4 arrays provide the best and the ESR array provides the worst flood histograms. The DOI resolution obtained from the DOI profiles of the individual crystals of the four array is from 2.1 to 2.35 mm for events with E > 350 keV. The DOI ratio variation among crystals is bigger for the BaSO 4 arrays as compared to both the ESR and Toray arrays. The BaSO 4 arrays provide worse detector based DOI resolution. The photopeak amplitude of the Toray array had the maximum change with depth, it provides the worst energy resolution of 21.3%. The photopeak amplitude of the BaSO 4 array with 80 μm reflector almost doesn't change with depth, it provides the best energy resolution of 12.9%. A maximum timing shift of 1.37 ns to 1.61 ns among the corner and the center crystals in the four arrays was obtained due to the use of resistor network readout. A crystal based timing resolution of 0.68 ns to 0.83 ns and a detector based timing resolution of 1.26 ns to 1.45 ns were obtained for the four detector modules. Four high resolution depth encoding small animal PET detectors were developed using dual-ended readout of pixelated scintillator arrays with SiPMs. The performance results show that those detectors can be used to build a small animal PET scanner to simultaneously achieve uniform high spatial resolution and high sensitivity. © 2017 American Association of Physicists in Medicine.

Investigation of skin structures based on infrared wave parameter indirect microscopic imaging

NASA Astrophysics Data System (ADS)

Zhao, Jun; Liu, Xuefeng; Xiong, Jichuan; Zhou, Lijuan

2017-02-01

Detailed imaging and analysis of skin structures are becoming increasingly important in modern healthcare and clinic diagnosis. Nanometer resolution imaging techniques such as SEM and AFM can cause harmful damage to the sample and cannot measure the whole skin structure from the very surface through epidermis, dermis to subcutaneous. Conventional optical microscopy has the highest imaging efficiency, flexibility in onsite applications and lowest cost in manufacturing and usage, but its image resolution is too low to be accepted for biomedical analysis. Infrared parameter indirect microscopic imaging (PIMI) uses an infrared laser as the light source due to its high transmission in skins. The polarization of optical wave through the skin sample was modulated while the variation of the optical field was observed at the imaging plane. The intensity variation curve of each pixel was fitted to extract the near field polarization parameters to form indirect images. During the through-skin light modulation and image retrieving process, the curve fitting removes the blurring scattering from neighboring pixels and keeps only the field variations related to local skin structures. By using the infrared PIMI, we can break the diffraction limit, bring the wide field optical image resolution to sub-200nm, in the meantime of taking advantage of high transmission of infrared waves in skin structures.

Video-rate or high-precision: a flexible range imaging camera

NASA Astrophysics Data System (ADS)

Dorrington, Adrian A.; Cree, Michael J.; Carnegie, Dale A.; Payne, Andrew D.; Conroy, Richard M.; Godbaz, John P.; Jongenelen, Adrian P. P.

2008-02-01

A range imaging camera produces an output similar to a digital photograph, but every pixel in the image contains distance information as well as intensity. This is useful for measuring the shape, size and location of objects in a scene, hence is well suited to certain machine vision applications. Previously we demonstrated a heterodyne range imaging system operating in a relatively high resolution (512-by-512) pixels and high precision (0.4 mm best case) configuration, but with a slow measurement rate (one every 10 s). Although this high precision range imaging is useful for some applications, the low acquisition speed is limiting in many situations. The system's frame rate and length of acquisition is fully configurable in software, which means the measurement rate can be increased by compromising precision and image resolution. In this paper we demonstrate the flexibility of our range imaging system by showing examples of high precision ranging at slow acquisition speeds and video-rate ranging with reduced ranging precision and image resolution. We also show that the heterodyne approach and the use of more than four samples per beat cycle provides better linearity than the traditional homodyne quadrature detection approach. Finally, we comment on practical issues of frame rate and beat signal frequency selection.

Challenges, constraints, and results of lens design for 17 micron-bolometer focal plane arrays in 8-12 micron waveband

NASA Astrophysics Data System (ADS)

Schuster, Norbert; Franks, John

2011-06-01

In the 8-12 micron waveband Focal Plane Arrays (FPA) are available with a 17 micron pixel pitch in different arrays sizes (e.g. 512 x 480 pixels and 320 x 240 pixels) and with excellent electrical properties. Many applications become possible using this new type of IR-detector which will become the future standard in uncooled technology. Lenses with an f-number faster than f/1.5 minimize the diffraction impact on the spatial resolution and guarantee a high thermal resolution for uncooled cameras. Both effects will be quantified. The distinction between Traditional f-number (TF) and Radiometric f-number (RF) is discussed. Lenses with different focal lengths are required for applications in a variety of markets. They are classified by their Horizontal field of view (HFOV). Respecting the requirements for high volume markets, several two lens solutions will be discussed. A commonly accepted parameter of spatial resolution is the Modulation Transfer Function (MTF)-value at the Nyquist frequency of the detector (here 30cy/mm). This parameter of resolution will be presented versus field of view. Wide Angle and Super Wide Angle lenses are susceptible to low relative illumination in the corner of the detector. Measures to reduce this drop to an acceptable value are presented.

Magnetically-coupled microcalorimeter arrays for x-ray astrophysics

NASA Astrophysics Data System (ADS)

Bandler, Simon

The "X-ray Surveyor" has been listed by NASA as one of the four major large mission concepts to be studied in the next Astrophysics Decadal Review in its preliminary list of large concepts. One of the key instruments on such a mission would be a very large format X-ray microcalorimeter array, with an array size of greater than 100 thousand pixels. Magnetically-coupled microcalorimeters (MCC) are one of the technologies with the greatest potential to meet the requirements of this mission, and this proposal is one to carry out research specifically to reach the goals of this vision. The "X-ray Surveyor" is a concept for a future mission that will make X-ray observations that are instrumental to understanding the quickly emerging population of galaxies and supermassive black holes at z ~10. The observations will trace the formation of galaxies and their assembly into large-scale structures starting from the earliest possible epochs. This mission would be observing baryons and large-scale physical processes outside of the very densest regions in the local Universe. This can be achieved with an X-ray observatory with similar angular resolution as Chandra but with significantly improved optic area and detector sensitivity. Chandra-scale angular resolution (1" or better) is essential in building more powerful, higher throughput observatories to avoid source confusion and remain photon-limited rather than background-limited. A prime consideration for the microcalorimeter camera on this type of mission is maintaining ~ 1 arcsec spatial resolution over the largest possible field of view, even if this means a slight trade-off against the spectral resolution. A uniform array of 1" pixels covering at least 5'x5' field of view is desired. To reduce the number of sensors read out, in geometries where extremely fine pitch (~50 microns) is desired, the most promising technologies are those in which a thermal sensor such an MCC can read out a sub-array of 20-25 individual 1'• pixels. Projections based on the current state of this technology indicate that less than 5 eV energy resolution can be achieved with this sort of geometry. Theoretically, magnetically-coupled microcalorimeters are well-equipped to achieve the very highest energy resolutions, especially when several absorbers are attached to each sensor, increasing the heat capacity. This program will build upon the work carried out by our group on metallic magnetic calorimeters (MMC) and Magnetic penetration thermometers (MPT) in the antecedent program. In this program we will carry out development in three main areas. First, we will develop sensor geometries that are optimized for reading out sub-arrays of pixels with a single sensor of the type that is likely desired by the "X-ray Surveyor". Second, we will further develop large-format arraying prototypes with the engineering of wiring-pixel approaches that are scalable to the large-format arrays that are needed. Third, we will develop the read-out technology that will be necessary, which utilizes the next generation of X-ray microcalorimeter read-out approach, a microwave multiplexing readout.

Comparison of fractal dimensions based on segmented NDVI fields obtained from different remote sensors.

NASA Astrophysics Data System (ADS)

Alonso, C.; Benito, R. M.; Tarquis, A. M.

2012-04-01

Satellite image data have become an important source of information for monitoring vegetation and mapping land cover at several scales. Beside this, the distribution and phenology of vegetation is largely associated with climate, terrain characteristics and human activity. Various vegetation indices have been developed for qualitative and quantitative assessment of vegetation using remote spectral measurements. In particular, sensors with spectral bands in the red (RED) and near-infrared (NIR) lend themselves well to vegetation monitoring and based on them [(NIR - RED) / (NIR + RED)] Normalized Difference Vegetation Index (NDVI) has been widespread used. Given that the characteristics of spectral bands in RED and NIR vary distinctly from sensor to sensor, NDVI values based on data from different instruments will not be directly comparable. The spatial resolution also varies significantly between sensors, as well as within a given scene in the case of wide-angle and oblique sensors. As a result, NDVI values will vary according to combinations of the heterogeneity and scale of terrestrial surfaces and pixel footprint sizes. Therefore, the question arises as to the impact of differences in spectral and spatial resolutions on vegetation indices like the NDVI. The aim of this study is to establish a comparison between two different sensors in their NDVI values at different spatial resolutions. Scaling analysis and modeling techniques are increasingly understood to be the result of nonlinear dynamic mechanisms repeating scale after scale from large to small scales leading to non-classical resolution dependencies. In the remote sensing framework the main characteristic of sensors images is the high local variability in their values. This variability is a consequence of the increase in spatial and radiometric resolution that implies an increase in complexity that it is necessary to characterize. Fractal and multifractal techniques has been proven to be useful to extract such complexities from remote sensing images and will applied in this study to see the scaling behavior for each sensor in generalized fractal dimensions. The studied area is located in the provinces of Caceres and Salamanca (east of Iberia Peninsula) with an extension of 32 x 32 km2. The altitude in the area varies from 1,560 to 320 m, comprising natural vegetation in the mountain area (forest and bushes) and agricultural crops in the valleys. Scaling analysis were applied to Landsat-5 and MODIS TERRA to the normalized derived vegetation index (NDVI) on the same region with one day of difference, 13 and 12 of July 2003 respectively. From these images the area of interest was selected obtaining 1024 x 1024 pixels for Landsat image and 128 x 128 pixels for MODIS image. This implies that the resolution for MODIS is 250x250 m. and for Landsat is 30x30 m. From the reflectance data obtained from NIR and RED bands, NDVI was calculated for each image focusing this study on 0.2 to 0.5 ranges of values. Once that both NDVI fields were obtained several fractal dimensions were estimated in each one segmenting the values in 0.20-0.25, 0.25-0.30 and so on to rich 0.45-0.50. In all the scaling analysis the scale size length was expressed in meters, and not in pixels, to make the comparison between both sensors possible. Results are discussed. Acknowledgements This work has been supported by the Spanish MEC under Projects No. AGL2010-21501/AGR, MTM2009-14621 and i-MATH No. CSD2006-00032

Cryogenic Detectors (Narrow Field Instruments)

NASA Astrophysics Data System (ADS)

Hoevers, H.; Verhoeve, P.

Two cryogenic imaging spectrometer arrays are currently considered as focal plane instruments for XEUS. The narrow field imager 1 (NFI 1) will cover the energy range from 0.05 to 3 keV with an energy resolution of 2 eV, or better, at 500 eV. A second narrow field imager (NFI 2) covers the energy range from 1 to 15 keV with an energy resolution of 2 eV (at 1 keV) and 5 eV (at 7 keV), creating some overlap with part of the NFI 1 energy window. Both narrow field imagers have a 0.5 arcmin field of view. Their imaging capabilities are matched to the XEUS optics of 2 to 5 arcsec leading to 1 arcsec pixels. The detector arrays will be cooled by a closed cycle system comprising a mechanical cooler with a base temperature of 2.5 K and either a low temperature 3He sorption pump providing the very low temperature stage and/or an Adiabatic Demagnetization Refrigerator (ADR). The ADR cooler is explicitly needed to cool the NFI 2 array. The narrow field imager 1} Currently a 48 times 48 element array of superconducting tunnel junctions (STJ) is envisaged. Its operating temperature is in the range between 30 and 350 mK. Small, single Ta STJs (20-50 mum on a side) have shown 3.5 eV (FWHM) resolution at E = 525 eV and small arrays have been successfully demonstrated (6 times 6 pixels), or are currently tested (10 times 12 pixels). Alternatively, a prototype Distributed Read-Out Imaging Device (DROID), consisting of a linear superconducting Ta absorber of 20 times 100 mum2, including a 20 times 20 mum STJ for readout at either end, has shown a measured energy resolution of 2.4 eV (FWHM) at E = 500 eV. Simulations involving the diffusion properties as well as loss and tunnel rates have shown that the performance can be further improved by slight modifications in the geometry, and that the size of the DROIDS can be increased to 0.5-1.0 mm without loss in energy resolution. The relatively large areas and good energy resolution compared to single STJs make DROIDS good candidates for the basic elements of the NFI 1 detector array. With a DROID-based array of 48 times 10 elements covering the NFI 1 field of view of 0.5 arcmin, the number of signal wires would already be reduced by a factor 2.4 compared to a 48 times 48 array of single pixels. While the present prototype DROIDS are still covered with a 480 nm thick SiOx insulation layer, this layer could easily be reduced in thickness or omitted. The detection efficiency of such a device with a 500 nm thick Ta absorber would be >80% in the energy range of 100-3000eV, without any disturbing contributions from other layers as in single STJs. Further developments involve devices of lower Tc-superconductors for better energy resolution and faster diffusion (e.g. Mo). The narrow field imager 2 The NFI 2 will consist of an array of 32 times 32 detector pixels. Each detector is a microcalorimeter which consists of a a superconducting to normal phase transition edge thermometer (transition edge sensor, TES) with an operating temperature of 100 mK, and an absorber which allows a detection efficiency of >90% and a filling factor of the focal plane in excess of 90%. Single pixel microcalorimeters with a Ti/Au TES have already shown an energy resolution of 3.9 eV at 5.89 keV in combination with a thermal response time of 100 mus. These results imply that they the high-energy requirement for XEUS can be met, in terms of energy resolution and response time. It has been demonstrated that bismuth can be applied as absorber material without impeding on the detector performance. Bi increases the stopping power in excess of 90 % and allows for a high filling factor since the absorber is can be modeled in the shape of a mushroom, allowing that the wiring to the detector and the thermal support structure are placed under the hat of the mushroom. In order to realize the NFI 2 detector array, there are two major development areas. Firstly, there is the development of micromachined Si and SiN structures that will provide proper cooling for each of the pixels and the production of small membranes to support the detector pixels. Micromechanical prototypes of this cooling and support structure have been made and are currently characterized. Secondly, the read-out of the array has to be developed. The current baseline for research is frequency division multiplexing (FDM) which will allow that a large detector can be read-out with a minimum of low-temperature electronics (Superconducting Quantum Interference Devices) and with a minimum of wires to the detector, thus reducing the thermal load on the detector cooling. Significant progress has been achieved since a microcalorimeter has been successfully biased at a frequency of 46 kHz, showing a performance which is very similar to that under conventional dc-bias conditions, proving the FDM concept.

High resolution 1280×1024, 15 μm pitch compact InSb IR detector with on-chip ADC

NASA Astrophysics Data System (ADS)

Nesher, O.; Pivnik, I.; Ilan, E.; Calalhorra, Z.; Koifman, A.; Vaserman, I.; Oiknine Schlesinger, J.; Gazit, R.; Hirsh, I.

2009-05-01

Over the last decade, SCD has developed and manufactured high quality InSb Focal Plane Arrays (FPAs), which are currently used in many applications worldwide. SCD's production line includes many different types of InSb FPA with formats of 320x256, 480x384 and 640x512 elements and with pitch sizes in the range of 15 to 30 μm. All these FPAs are available in various packaging configurations, including fully integrated Detector-Dewar-Cooler Assemblies (DDCA) with either closed-cycle Sterling or open-loop Joule-Thomson coolers. With an increasing need for higher resolution, SCD has recently developed a new large format 2-D InSb detector with 1280x1024 elements and a pixel size of 15μm. The InSb 15μm pixel technology has already been proven at SCD with the "Pelican" detector (640x512 elements), which was introduced at the Orlando conference in 2006. A new signal processor was developed at SCD for use in this mega-pixel detector. This Readout Integrated Circuit (ROIC) is designed for, and manufactured with, 0.18 μm CMOS technology. The migration from 0.5 to 0.18 μm CMOS technology supports SCD's roadmap for the reduction of pixel size and power consumption and is in line with the increasing demand for improved performance and on-chip functionality. Consequently, the new ROIC maintains the same level of performance and functionality with a 15 μm pitch, as exists in our 20 μm-pitch ROICs based on 0.5μm CMOS technology. Similar to Sebastian (SCD ROIC with A/D on chip), this signal processor also includes A/D converters on the chip and demonstrates the same level of performance, but with reduced power consumption. The pixel readout rate has been increased up to 160 MHz in order to support a high frame rate, resulting in 120 Hz operation with a window of 1024×1024 elements at ~130 mW. These A/D converters on chip save the need for using 16 A/D channels on board (in the case of an analog ROIC) which would operate at 10 MHz and consume about 8Watts A Dewar has been designed with a stiffened detector support to withstand harsh environmental conditions with a minimal contribution to the heat load of the detector. The combination of the 0.18μm-based low power CMOS technology for the ROIC and the stiffening of the detector support within the Dewar has enabled the use of the Ricor K508 cryo-cooler (0.5 W). This has created a high-resolution detector in a very compact package. In this paper we present the basic concept of the new detector. We will describe its construction and will present electrical and radiometric characterization results.

Segmentation of arterial vessel wall motion to sub-pixel resolution using M-mode ultrasound.

PubMed

Fancourt, Craig; Azer, Karim; Ramcharan, Sharmilee L; Bunzel, Michelle; Cambell, Barry R; Sachs, Jeffrey R; Walker, Matthew

2008-01-01

We describe a method for segmenting arterial vessel wall motion to sub-pixel resolution, using the returns from M-mode ultrasound. The technique involves measuring the spatial offset between all pairs of scans from their cross-correlation, converting the spatial offsets to relative wall motion through a global optimization, and finally translating from relative to absolute wall motion by interpolation over the M-mode image. The resulting detailed wall distension waveform has the potential to enhance existing vascular biomarkers, such as strain and compliance, as well as enable new ones.

X-ray Hybrid CMOS Detectors : Recent progress in development and characterization

NASA Astrophysics Data System (ADS)

Chattopadhyay, Tanmoy; Falcone, Abraham; Burrows, David N.

2017-08-01

PennState high energy astronomy laboratory has been working on the development and characterization of Hybrid CMOS Detectors (HCDs) for last few years in collaboration with Teledyne Imaging Sensors (TIS). HCDs are preferred over X-ray CCDs due to their higher and flexible read out rate, radiation hardness and low power which make them more suitable for next generation large area X-ray telescopic missions. An H2RG detector with 36 micron pixel pitch and 18 micron ROIC, has been selected for a sounding rocket flight in 2018. The H2RG detector provides ~2.5 % energy resolution at 5.9 keV and ~7 e- read noise when coupled to a cryo-SIDECAR. We could also detect a clear Oxygen line (~0.5 keV) from the detector implying a lower energy threshold of ~0.3 keV. Further improvement in the energy resolution and read noise is currently under progress. We have been working on the characterization of small pixel HCDs (12.5 micron pixel; smallest pixel HCDs developed so far) which is important for the development of next generation high resolution X-ray spectroscopic instrument based on HCDs. Event recognition in HCDs is another exciting prospect which have been successfully shown to work with a 64 X 64 pixel prototype SPEEDSTAR-EXD which use comparators at each pixel to read out only those pixels having detectable signal, thereby providing an order of magnitude improvement in the read out rate. Currently, we are working on the development of a large area SPEEDSTAR-EXD array for the development of a full fledged instrument. HCDs due to their fast read out, can also be explored as a large FOV instrument to study GRB afterglows and variability and spectroscopic study of other astrophysical transients. In this context, we are characterizing a Lobster-HCD system at multiple energies and multiple off-axis angles for future rocket or CubeSate experiments. In this presentation, I will briefly present these new developments and experiments with HCDs and the analysis techniques.

Enhancing the image resolution in a single-pixel sub-THz imaging system based on compressed sensing

NASA Astrophysics Data System (ADS)

Alkus, Umit; Ermeydan, Esra Sengun; Sahin, Asaf Behzat; Cankaya, Ilyas; Altan, Hakan

2018-04-01

Compressed sensing (CS) techniques allow for faster imaging when combined with scan architectures, which typically suffer from speed. This technique when implemented with a subterahertz (sub-THz) single detector scan imaging system provides images whose resolution is only limited by the pixel size of the pattern used to scan the image plane. To overcome this limitation, the image of the target can be oversampled; however, this results in slower imaging rates especially if this is done in two-dimensional across the image plane. We show that by implementing a one-dimensional (1-D) scan of the image plane, a modified approach to CS theory applied with an appropriate reconstruction algorithm allows for successful reconstruction of the reflected oversampled image of a target placed in standoff configuration from the source. The experiments are done in reflection mode configuration where the operating frequency is 93 GHz and the corresponding wavelength is λ = 3.2 mm. To reconstruct the image with fewer samples, CS theory is applied using masks where the pixel size is 5 mm × 5 mm, and each mask covers an image area of 5 cm × 5 cm, meaning that the basic image is resolved as 10 × 10 pixels. To enhance the resolution, the information between two consecutive pixels is used, and oversampling along 1-D coupled with a modification of the masks in CS theory allowed for oversampled images to be reconstructed rapidly in 20 × 20 and 40 × 40 pixel formats. These are then compared using two different reconstruction algorithms, TVAL3 and ℓ1-MAGIC. The performance of these methods is compared for both simulated signals and real signals. It is found that the modified CS theory approach coupled with the TVAL3 reconstruction process, even when scanning along only 1-D, allows for rapid precise reconstruction of the oversampled target.

Optimal configuration of a low-dose breast-specific gamma camera based on semiconductor CdZnTe pixelated detectors

NASA Astrophysics Data System (ADS)

Genocchi, B.; Pickford Scienti, O.; Darambara, DG

2017-05-01

Breast cancer is one of the most frequent tumours in women. During the ‘90s, the introduction of screening programmes allowed the detection of cancer before the palpable stage, reducing its mortality up to 50%. About 50% of the women aged between 30 and 50 years present dense breast parenchyma. This percentage decreases to 30% for women between 50 to 80 years. In these women, mammography has a sensitivity of around 30%, and small tumours are covered by the dense parenchyma and missed in the mammogram. Interestingly, breast-specific gamma-cameras based on semiconductor CdZnTe detectors have shown to be of great interest to early diagnosis. Infact, due to the high energy, spatial resolution, and high sensitivity of CdZnTe, molecular breast imaging has been shown to have a sensitivity of about 90% independently of the breast parenchyma. The aim of this work is to determine the optimal combination of the detector pixel size, hole shape, and collimator material in a low dose dual head breast specific gamma camera based on a CdZnTe pixelated detector at 140 keV, in order to achieve high count rate, and the best possible image spatial resolution. The optimal combination has been studied by modeling the system using the Monte Carlo code GATE. Six different pixel sizes from 0.85 mm to 1.6 mm, two hole shapes, hexagonal and square, and two different collimator materials, lead and tungsten were considered. It was demonstrated that the camera achieved higher count rates, and better signal-to-noise ratio when equipped with square hole, and large pixels (> 1.3 mm). In these configurations, the spatial resolution was worse than using small pixel sizes (< 1.3 mm), but remained under 3.6 mm in all cases.

Geologic map of Io

USGS Publications Warehouse

Williams, David A.; Keszthelyi, Laszlo P.; Crown, David A.; Yff, Jessica A.; Jaeger, Windy L.; Schenk, Paul M.; Geissler, Paul E.; Becker, Tammy L.

2011-01-01

Io, discovered by Galileo Galilei on January 7–13, 1610, is the innermost of the four Galilean satellites of the planet Jupiter (Galilei, 1610). It is the most volcanically active object in the Solar System, as recognized by observations from six National Aeronautics and Space Administration (NASA) spacecraft: Voyager 1 (March 1979), Voyager 2 (July 1979), Hubble Space Telescope (1990–present), Galileo (1996–2001), Cassini (December 2000), and New Horizons (February 2007). The lack of impact craters on Io in any spacecraft images at any resolution attests to the high resurfacing rate (1 cm/yr) and the dominant role of active volcanism in shaping its surface. High-temperature hot spots detected by the Galileo Solid-State Imager (SSI), Near-Infrared Mapping Spectrometer (NIMS), and Photopolarimeter-Radiometer (PPR) usually correlate with darkest materials on the surface, suggesting active volcanism. The Voyager flybys obtained complete coverage of Io's subjovian hemisphere at 500 m/pixel to 2 km/pixel, and most of the rest of the satellite at 5–20 km/pixel. Repeated Galileo flybys obtained complementary coverage of Io's antijovian hemisphere at 5 m/pixel to 1.4 km/pixel. Thus, the Voyager and Galileo data sets were merged to enable the characterization of the whole surface of the satellite at a consistent resolution. The United States Geological Survey (USGS) produced a set of four global mosaics of Io in visible wavelengths at a spatial resolution of 1 km/pixel, released in February 2006, which we have used as base maps for this new global geologic map. Much has been learned about Io's volcanism, tectonics, degradation, and interior since the Voyager flybys, primarily during and following the Galileo Mission at Jupiter (December 1995–September 2003), and the results have been summarized in books published after the end of the Galileo Mission. Our mapping incorporates this new understanding to assist in map unit definition and to provide a global synthesis of Io's geology.

Sensing, Spectra and Scaling: What's in Store for Land Observations

NASA Technical Reports Server (NTRS)

Goetz, Alexander F. H.

2001-01-01

Bill Pecora's 1960's vision of the future, using spacecraft-based sensors for mapping the environment and exploring for resources, is being implemented today. New technology has produced better sensors in space such as the Landsat Thematic Mapper (TM) and SPOT, and creative researchers are continuing to find new applications. However, with existing sensors, and those intended for launch in this century, the potential for extracting information from the land surface is far from being exploited. The most recent technology development is imaging spectrometry, the acquisition of images in hundreds of contiguous spectral bands, such that for any pixel a complete reflectance spectrum can be acquired. Experience with Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) has shown that, with proper attention paid to absolute calibration, it is possible to acquire apparent surface reflectance to 5% accuracy without any ground-based measurement. The data reduction incorporates in educated guess of the aerosol scattering, development of a precipitable water vapor map from the data and mapping of cirrus clouds in the 1.38 micrometer band. This is not possible with TM. The pixel size in images of the earth plays and important role in the type and quality of information that can be derived. Less understood is the coupling between spatial and spectral resolution in a sensor. Recent work has shown that in processing the data to derive the relative abundance of materials in a pixel, also known is unmixing, the pixel size is an important parameter. A variance in the relative abundance of materials among the pixels is necessary to be able to derive the endmembers or pure material constituent spectra. In most cases, the 1 km pixel size for the Earth Observing System Moderate Resolution Imaging Spectroradiometer (MODIS) instrument is too large to meet the variance criterion. A pointable high spatial and spectral resolution imaging spectrometer in orbit will be necessary to make the major next step in our understanding of the solid earth surface and its changing face.

The Si/CdTe semiconductor Compton camera of the ASTRO-H Soft Gamma-ray Detector (SGD)

NASA Astrophysics Data System (ADS)

Watanabe, Shin; Tajima, Hiroyasu; Fukazawa, Yasushi; Ichinohe, Yuto; Takeda, Shin`ichiro; Enoto, Teruaki; Fukuyama, Taro; Furui, Shunya; Genba, Kei; Hagino, Kouichi; Harayama, Atsushi; Kuroda, Yoshikatsu; Matsuura, Daisuke; Nakamura, Ryo; Nakazawa, Kazuhiro; Noda, Hirofumi; Odaka, Hirokazu; Ohta, Masayuki; Onishi, Mitsunobu; Saito, Shinya; Sato, Goro; Sato, Tamotsu; Takahashi, Tadayuki; Tanaka, Takaaki; Togo, Atsushi; Tomizuka, Shinji

2014-11-01

The Soft Gamma-ray Detector (SGD) is one of the instrument payloads onboard ASTRO-H, and will cover a wide energy band (60-600 keV) at a background level 10 times better than instruments currently in orbit. The SGD achieves low background by combining a Compton camera scheme with a narrow field-of-view active shield. The Compton camera in the SGD is realized as a hybrid semiconductor detector system which consists of silicon and cadmium telluride (CdTe) sensors. The design of the SGD Compton camera has been finalized and the final prototype, which has the same configuration as the flight model, has been fabricated for performance evaluation. The Compton camera has overall dimensions of 12 cm×12 cm×12 cm, consisting of 32 layers of Si pixel sensors and 8 layers of CdTe pixel sensors surrounded by 2 layers of CdTe pixel sensors. The detection efficiency of the Compton camera reaches about 15% and 3% for 100 keV and 511 keV gamma rays, respectively. The pixel pitch of the Si and CdTe sensors is 3.2 mm, and the signals from all 13,312 pixels are processed by 208 ASICs developed for the SGD. Good energy resolution is afforded by semiconductor sensors and low noise ASICs, and the obtained energy resolutions with the prototype Si and CdTe pixel sensors are 1.0-2.0 keV (FWHM) at 60 keV and 1.6-2.5 keV (FWHM) at 122 keV, respectively. This results in good background rejection capability due to better constraints on Compton kinematics. Compton camera energy resolutions achieved with the final prototype are 6.3 keV (FWHM) at 356 keV and 10.5 keV (FWHM) at 662 keV, which satisfy the instrument requirements for the SGD Compton camera (better than 2%). Moreover, a low intrinsic background has been confirmed by the background measurement with the final prototype.

The Detector Subsystem for the SXS Instrument on the Astro-H Observatory

NASA Technical Reports Server (NTRS)

Porter, Frederick; Adams, J. S.; Brown, G. V.; Chervenak, J. A.; Chiao, M. P.; Fujimoto, R.; Ishisaki, Y.; Kelley, R. L.; Kilbourne, C. A.; McCammon, D.;

Image simulation and assessment of the colour and spatial capabilities of the Colour and Stereo Surface Imaging System (CaSSIS) on the ExoMars Trace Gas Orbiter

USGS Publications Warehouse

Tornabene, Livio L.; Seelos, Frank P.; Pommerol, Antoine; Thomas, Nicolas; Caudill, Christy M.; Becerra, Patricio; Bridges, John C.; Byrne, Shane; Cardinale, Marco; Chojnacki, Matthew; Conway, Susan J.; Cremonese, Gabriele; Dundas, Colin M.; El-Maarry, M. R.; Fernando, Jennifer; Hansen, Candice J.; Hansen, Kayle; Harrison, Tanya N.; Henson, Rachel; Marinangeli, Lucia; McEwen, Alfred S.; Pajola, Maurizio; Sutton, Sarah S.; Wray, James J.

2018-01-01

This study aims to assess the spatial and visible/near-infrared (VNIR) colour/spectral capabilities of the 4-band Colour and Stereo Surface Imaging System (CaSSIS) aboard the ExoMars 2016 Trace Grace Orbiter (TGO). The instrument response functions for the CaSSIS imager was used to resample spectral libraries, modelled spectra and to construct spectrally (i.e., in I/F space) and spatially consistent simulated CaSSIS image cubes of various key sites of interest and for ongoing scientific investigations on Mars. Coordinated datasets from Mars Reconnaissance Orbiter (MRO) are ideal, and specifically used for simulating CaSSIS. The Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) provides colour information, while the Context Imager (CTX), and in a few cases the High-Resolution Imaging Science Experiment (HiRISE), provides the complementary spatial information at the resampled CaSSIS unbinned/unsummed pixel resolution (4.6 m/pixel from a 400-km altitude). The methodology used herein employs a Gram-Schmidt spectral sharpening algorithm to combine the ∼18–36 m/pixel CRISM-derived CaSSIS colours with I/F images primarily derived from oversampled CTX images. One hundred and eighty-one simulated CaSSIS 4-colour image cubes (at 18–36 m/pixel) were generated (including one of Phobos) based on CRISM data. From these, thirty-three “fully”-simulated image cubes of thirty unique locations on Mars (i.e., with 4 colour bands at 4.6 m/pixel) were made. All simulated image cubes were used to test both the colour capabilities of CaSSIS by producing standard colour RGB images, colour band ratio composites (CBRCs) and spectral parameters. Simulated CaSSIS CBRCs demonstrated that CaSSIS will be able to readily isolate signatures related to ferrous (Fe2+) iron- and ferric (Fe3+) iron-bearing deposits on the surface of Mars, ices and atmospheric phenomena. Despite the lower spatial resolution of CaSSIS when compared to HiRISE, the results of this work demonstrate that CaSSIS will not only compliment HiRISE-scale studies of various geological and seasonal phenomena, it will also enhance them by providing additional colour and geologic context through its wider and longer full-colour coverage (∼9.4×50">∼9.4×50∼9.4×50 km), and its increased sensitivity to iron-bearing materials from its two IR bands (RED and NIR). In a few examples, subtle surface changes that were not easily detected by HiRISE were identified in the simulated CaSSIS images. This study also demonstrates the utility of the Gram-Schmidt spectral pan-sharpening technique to extend VNIR colour/spectral capabilities from a lower spatial resolution colour/spectral dataset to a single-band or panchromatic image greyscale image with higher resolution. These higher resolution colour products (simulated CaSSIS or otherwise) are useful as means to extend both geologic context and mapping of datasets with coarser spatial resolutions. The results of this study indicate that the TGO mission objectives, as well as the instrument-specific mission objectives, will be achievable with CaSSIS.

Evaluation of Satellite Remote Sensing Albedo Retrievals over the Ablation Area of the Southwestern Greenland Ice Sheet

NASA Technical Reports Server (NTRS)

Moustafa, Samiah E.; Rennermalm, Asa K.; Roman, Miguel O.; Wang, Zhuosen; Schaaf, Crystal B.; Smith, Laurence C.; Koenig, Lora S.; Erb, Angela

2017-01-01

MODerate resolution Imaging Spectroradiometer (MODIS) albedo products have been validated over spatially uniform, snow-covered areas of the Greenland ice sheet (GrIS) using the so-called single 'point-to-pixel' method. This study expands on this methodology by applying a 'multiple-point-to-pixel' method and examination of spatial autocorrelation (here using semivariogram analysis) by using in situ observations, high-resolution World- View-2 (WV-2) surface reflectances, and MODIS Collection V006 daily blue-sky albedo over a spatially heterogeneous surfaces in the lower ablation zone in southwest Greenland. Our results using 232 ground-based samples within two MODIS pixels, one being more spatial heterogeneous than the other, show little difference in accuracy among narrow and broad band albedos (except for Band 2). Within the more homogenous pixel area, in situ and MODIS albedos were very close (error varied from -4% to +7%) and within the range of ASD standard errors. The semivariogram analysis revealed that the minimum observational footprint needed for a spatially representative sample is 30 m. In contrast, over the more spatially heterogeneous surface pixel, a minimum footprint size was not quantifiable due to spatial autocorrelation, and far exceeds the effective resolution of the MODIS retrievals. Over the high spatial heterogeneity surface pixel, MODIS is lower than ground measurements by 4-7%, partly due to a known in situ undersampling of darker surfaces that often are impassable by foot (e.g., meltwater features and shadowing effects over crevasses). Despite the sampling issue, our analysis errors are very close to the stated general accuracy of the MODIS product of 5%. Thus, our study suggests that the MODIS albedo product performs well in a very heterogeneous, low-albedo, area of the ice sheet ablation zone. Furthermore, we demonstrate that single 'point-to-pixel' methods alone are insufficient in characterizing and validating the variation of surface albedo displayed in the lower ablation area. This is true because the distribution of in situ data deviations from MODIS albedo show a substantial range, with the average values for the 10th and 90th percentiles being -0.30 and 0.43 across all bands. Thus, if only single point is taken for ground validation, and is randomly selected from either distribution tails, the error would appear to be considerable. Given the need for multiple in-situ points, concurrent albedo measurements derived from existing AWSs, (low-flying vehicles (airborne or unmanned) and high-resolution imagery (WV-2)) are needed to resolve high sub-pixel variability in the ablation zone, and thus, further improve our characterization of Greenland's surface albedo.

High Speed Computational Ghost Imaging via Spatial Sweeping

NASA Astrophysics Data System (ADS)

Wang, Yuwang; Liu, Yang; Suo, Jinli; Situ, Guohai; Qiao, Chang; Dai, Qionghai

2017-03-01

Computational ghost imaging (CGI) achieves single-pixel imaging by using a Spatial Light Modulator (SLM) to generate structured illuminations for spatially resolved information encoding. The imaging speed of CGI is limited by the modulation frequency of available SLMs, and sets back its practical applications. This paper proposes to bypass this limitation by trading off SLM’s redundant spatial resolution for multiplication of the modulation frequency. Specifically, a pair of galvanic mirrors sweeping across the high resolution SLM multiply the modulation frequency within the spatial resolution gap between SLM and the final reconstruction. A proof-of-principle setup with two middle end galvanic mirrors achieves ghost imaging as fast as 42 Hz at 80 × 80-pixel resolution, 5 times faster than state-of-the-arts, and holds potential for one magnitude further multiplication by hardware upgrading. Our approach brings a significant improvement in the imaging speed of ghost imaging and pushes ghost imaging towards practical applications.

Computational wavelength resolution for in-line lensless holography: phase-coded diffraction patterns and wavefront group-sparsity

NASA Astrophysics Data System (ADS)

Katkovnik, Vladimir; Shevkunov, Igor; Petrov, Nikolay V.; Egiazarian, Karen

2017-06-01

In-line lensless holography is considered with a random phase modulation at the object plane. The forward wavefront propagation is modelled using the Fourier transform with the angular spectrum transfer function. The multiple intensities (holograms) recorded by the sensor are random due to the random phase modulation and noisy with Poissonian noise distribution. It is shown by computational experiments that high-accuracy reconstructions can be achieved with resolution going up to the two thirds of the wavelength. With respect to the sensor pixel size it is a super-resolution with a factor of 32. The algorithm designed for optimal superresolution phase/amplitude reconstruction from Poissonian data is based on the general methodology developed for phase retrieval with a pixel-wise resolution in V. Katkovnik, "Phase retrieval from noisy data based on sparse approximation of object phase and amplitude", http://www.cs.tut.fi/ lasip/DDT/index3.html.

Towards high-resolution neutron imaging on IMAT

NASA Astrophysics Data System (ADS)

Minniti, T.; Tremsin, A. S.; Vitucci, G.; Kockelmann, W.

2018-01-01

IMAT is a new cold-neutron imaging facility at the neutron spallation source ISIS at the Rutherford Appleton Laboratory, U.K.. The ISIS pulsed source enables energy-selective and energy-resolved neutron imaging via time-of-flight (TOF) techniques, which are available in addition to the white-beam neutron radiography and tomography options. A spatial resolution of about 50 μm for white-beam neutron radiography was achieved early in the IMAT commissioning phase. In this work we have made the first steps towards achieving higher spatial resolution. A white-beam radiography with 18 μm spatial resolution was achieved in this experiment. This result was possible by using the event counting neutron pixel detector based on micro-channel plates (MCP) coupled with a Timepix readout chip with 55 μm sized pixels, and by employing an event centroiding technique. The prospects for energy-selective neutron radiography for this centroiding mode are discussed.

Alternative Optimizations of X-ray TES Arrays: Soft X-rays, High Count Rates, and Mixed-Pixel Arrays

NASA Technical Reports Server (NTRS)

Kilbourne, C. A.; Bandler, S. R.; Brown, A.-D.; Chervenak, J. A.; Figueroa-Feliciano, E.; Finkbeiner, F. M.; Iyomoto, N.; Kelley, R. L.; Porter, F. S.; Smith, S. J.

2007-01-01

We are developing arrays of superconducting transition-edge sensors (TES) for imaging spectroscopy telescopes such as the XMS on Constellation-X. While our primary focus has been on arrays that meet the XMS requirements (of which, foremost, is an energy resolution of 2.5 eV at 6 keV and a bandpass from approx. 0.3 keV to 12 keV), we have also investigated other optimizations that might be used to extend the XMS capabilities. In one of these optimizations, improved resolution below 1 keV is achieved by reducing the heat capacity. Such pixels can be based on our XMS-style TES's with the separate absorbers omitted. These pixels can added to an array with broadband response either as a separate array or interspersed, depending on other factors that include telescope design and science requirements. In one version of this approach, we have designed and fabricated a composite array of low-energy and broad-band pixels to provide high spectral resolving power over a broader energy bandpass than could be obtained with a single TES design. The array consists of alternating pixels with and without overhanging absorbers. To explore optimizations for higher count rates, we are also optimizing the design and operating temperature of pixels that are coupled to a solid substrate. We will present the performance of these variations and discuss other optimizations that could be used to enhance the XMS or enable other astrophysics experiments.

Development of a spatio-temporal disaggregation method (DisNDVI) for generating a time series of fine resolution NDVI images

NASA Astrophysics Data System (ADS)

Bindhu, V. M.; Narasimhan, B.

2015-03-01

Normalized Difference Vegetation Index (NDVI), a key parameter in understanding the vegetation dynamics, has high spatial and temporal variability. However, continuous monitoring of NDVI is not feasible at fine spatial resolution (<60 m) owing to the long revisit time needed by the satellites to acquire the fine spatial resolution data. Further, the study attains significance in the case of humid tropical regions of the earth, where the prevailing atmospheric conditions restrict availability of fine resolution cloud free images at a high temporal frequency. As an alternative to the lack of high resolution images, the current study demonstrates a novel disaggregation method (DisNDVI) which integrates the spatial information from a single fine resolution image and temporal information in terms of crop phenology from time series of coarse resolution images to generate estimates of NDVI at fine spatial and temporal resolution. The phenological variation of the pixels captured at the coarser scale provides the basis for relating the temporal variability of the pixel with the NDVI available at fine resolution. The proposed methodology was tested over a 30 km × 25 km spatially heterogeneous study area located in the south of Tamil Nadu, India. The robustness of the algorithm was assessed by an independent comparison of the disaggregated NDVI and observed NDVI obtained from concurrent Landsat ETM+ imagery. The results showed good spatial agreement across the study area dominated with agriculture and forest pixels, with a root mean square error of 0.05. The validation done at the coarser scale showed that disaggregated NDVI spatially averaged to 240 m compared well with concurrent MODIS NDVI at 240 m (R2 > 0.8). The validation results demonstrate the effectiveness of DisNDVI in improving the spatial and temporal resolution of NDVI images for utility in fine scale hydrological applications such as crop growth monitoring and estimation of evapotranspiration.

Charge Sharing and Charge Loss in a Cadmium-Zinc-Telluride Fine-Pixel Detector Array

NASA Technical Reports Server (NTRS)

Gaskin, J. A.; Sharma, D. P.; Ramsey, B. D.; Six, N. Frank (Technical Monitor)

2002-01-01

Because of its high atomic number, room temperature operation, low noise, and high spatial resolution a Cadmium-Zinc-Telluride (CZT) multi-pixel detector is ideal for hard x-ray astrophysical observation. As part of on-going research at MSFC (Marshall Space Flight Center) to develop multi-pixel CdZnTe detectors for this purpose, we have measured charge sharing and charge loss for a 4x4 (750micron pitch), lmm thick pixel array and modeled these results using a Monte-Carlo simulation. This model was then used to predict the amount of charge sharing for a much finer pixel array (with a 300micron pitch). Future work will enable us to compare the simulated results for the finer array to measured values.

An EUDET/AIDA Pixel Beam Telescope for Detector Development

NASA Astrophysics Data System (ADS)

Rubinskiy, I.; EUDET Consortium; AIDA Consortium

Ahigh resolution(σ< 2 μm) beam telescope based on monolithic active pixel sensors (MAPS) was developed within the EUDET collaboration. EUDET was a coordinated detector R&D programme for the future International Linear Collider providing test beam infrastructure to detector R&D groups. The telescope consists of six sensor planes with a pixel pitch of either 18.4 μm or 10 μmand canbe operated insidea solenoidal magnetic fieldofupto1.2T.Ageneral purpose cooling, positioning, data acquisition (DAQ) and offine data analysis tools are available for the users. The excellent resolution, readout rate andDAQintegration capabilities made the telescopea primary beam tests tool also for several CERN based experiments. In this report the performance of the final telescope is presented. The plans for an even more flexible telescope with three differentpixel technologies(ATLASPixel, Mimosa,Timepix) withinthenew European detector infrastructure project AIDA are presented.

Resolving the percentage of component terrains within single resolution elements

NASA Technical Reports Server (NTRS)

Marsh, S. E.; Switzer, P.; Kowalik, W. S.; Lyon, R. J. P.

1980-01-01

An approximate maximum likelihood technique employing a widely available discriminant analysis program is discussed that has been developed for resolving the percentage of component terrains within single resolution elements. The method uses all four channels of Landsat data simultaneously and does not require prior knowledge of the percentage of components in mixed pixels. It was tested in five cases that were chosen to represent mixtures of outcrop, soil and vegetation which would typically be encountered in geologic studies with Landsat data. For all five cases, the method proved to be superior to single band weighted average and linear regression techniques and permitted an estimate of the total area occupied by component terrains to within plus or minus 6% of the true area covered. Its major drawback is a consistent overestimation of the pixel component percent of the darker materials (vegetation) and an underestimation of the pixel component percent of the brighter materials (sand).

Photon Counting Imaging with an Electron-Bombarded Pixel Image Sensor

PubMed Central

Hirvonen, Liisa M.; Suhling, Klaus

2016-01-01

Electron-bombarded pixel image sensors, where a single photoelectron is accelerated directly into a CCD or CMOS sensor, allow wide-field imaging at extremely low light levels as they are sensitive enough to detect single photons. This technology allows the detection of up to hundreds or thousands of photon events per frame, depending on the sensor size, and photon event centroiding can be employed to recover resolution lost in the detection process. Unlike photon events from electron-multiplying sensors, the photon events from electron-bombarded sensors have a narrow, acceleration-voltage-dependent pulse height distribution. Thus a gain voltage sweep during exposure in an electron-bombarded sensor could allow photon arrival time determination from the pulse height with sub-frame exposure time resolution. We give a brief overview of our work with electron-bombarded pixel image sensor technology and recent developments in this field for single photon counting imaging, and examples of some applications. PMID:27136556

CMEIAS color segmentation: an improved computing technology to process color images for quantitative microbial ecology studies at single-cell resolution.

PubMed

Gross, Colin A; Reddy, Chandan K; Dazzo, Frank B

2010-02-01

Quantitative microscopy and digital image analysis are underutilized in microbial ecology largely because of the laborious task to segment foreground object pixels from background, especially in complex color micrographs of environmental samples. In this paper, we describe an improved computing technology developed to alleviate this limitation. The system's uniqueness is its ability to edit digital images accurately when presented with the difficult yet commonplace challenge of removing background pixels whose three-dimensional color space overlaps the range that defines foreground objects. Image segmentation is accomplished by utilizing algorithms that address color and spatial relationships of user-selected foreground object pixels. Performance of the color segmentation algorithm evaluated on 26 complex micrographs at single pixel resolution had an overall pixel classification accuracy of 99+%. Several applications illustrate how this improved computing technology can successfully resolve numerous challenges of complex color segmentation in order to produce images from which quantitative information can be accurately extracted, thereby gain new perspectives on the in situ ecology of microorganisms. Examples include improvements in the quantitative analysis of (1) microbial abundance and phylotype diversity of single cells classified by their discriminating color within heterogeneous communities, (2) cell viability, (3) spatial relationships and intensity of bacterial gene expression involved in cellular communication between individual cells within rhizoplane biofilms, and (4) biofilm ecophysiology based on ribotype-differentiated radioactive substrate utilization. The stand-alone executable file plus user manual and tutorial images for this color segmentation computing application are freely available at http://cme.msu.edu/cmeias/ . This improved computing technology opens new opportunities of imaging applications where discriminating colors really matter most, thereby strengthening quantitative microscopy-based approaches to advance microbial ecology in situ at individual single-cell resolution.

Commercial CMOS image sensors as X-ray imagers and particle beam monitors

NASA Astrophysics Data System (ADS)

Castoldi, A.; Guazzoni, C.; Maffessanti, S.; Montemurro, G. V.; Carraresi, L.

2015-01-01

CMOS image sensors are widely used in several applications such as mobile handsets webcams and digital cameras among others. Furthermore they are available across a wide range of resolutions with excellent spectral and chromatic responses. In order to fulfill the need of cheap systems as beam monitors and high resolution image sensors for scientific applications we exploited the possibility of using commercial CMOS image sensors as X-rays and proton detectors. Two different sensors have been mounted and tested. An Aptina MT9v034, featuring 752 × 480 pixels, 6μm × 6μm pixel size has been mounted and successfully tested as bi-dimensional beam profile monitor, able to take pictures of the incoming proton bunches at the DeFEL beamline (1-6 MeV pulsed proton beam) of the LaBeC of INFN in Florence. The naked sensor is able to successfully detect the interactions of the single protons. The sensor point-spread-function (PSF) has been qualified with 1MeV protons and is equal to one pixel (6 mm) r.m.s. in both directions. A second sensor MT9M032, featuring 1472 × 1096 pixels, 2.2 × 2.2 μm pixel size has been mounted on a dedicated board as high-resolution imager to be used in X-ray imaging experiments with table-top generators. In order to ease and simplify the data transfer and the image acquisition the system is controlled by a dedicated micro-processor board (DM3730 1GHz SoC ARM Cortex-A8) on which a modified LINUX kernel has been implemented. The paper presents the architecture of the sensor systems and the results of the experimental measurements.

Effects of frame rate and image resolution on pulse rate measured using multiple camera imaging photoplethysmography

NASA Astrophysics Data System (ADS)

Blackford, Ethan B.; Estepp, Justin R.

2015-03-01

Non-contact, imaging photoplethysmography uses cameras to facilitate measurements including pulse rate, pulse rate variability, respiration rate, and blood perfusion by measuring characteristic changes in light absorption at the skin's surface resulting from changes in blood volume in the superficial microvasculature. Several factors may affect the accuracy of the physiological measurement including imager frame rate, resolution, compression, lighting conditions, image background, participant skin tone, and participant motion. Before this method can gain wider use outside basic research settings, its constraints and capabilities must be well understood. Recently, we presented a novel approach utilizing a synchronized, nine-camera, semicircular array backed by measurement of an electrocardiogram and fingertip reflectance photoplethysmogram. Twenty-five individuals participated in six, five-minute, controlled head motion artifact trials in front of a black and dynamic color backdrop. Increasing the input channel space for blind source separation using the camera array was effective in mitigating error from head motion artifact. Herein we present the effects of lower frame rates at 60 and 30 (reduced from 120) frames per second and reduced image resolution at 329x246 pixels (one-quarter of the original 658x492 pixel resolution) using bilinear and zero-order downsampling. This is the first time these factors have been examined for a multiple imager array and align well with previous findings utilizing a single imager. Examining windowed pulse rates, there is little observable difference in mean absolute error or error distributions resulting from reduced frame rates or image resolution, thus lowering requirements for systems measuring pulse rate over sufficient length time windows.

High signal-to-noise-ratio electro-optical terahertz imaging system based on an optical demodulating detector array.

PubMed

Spickermann, Gunnar; Friederich, Fabian; Roskos, Hartmut G; Bolívar, Peter Haring

2009-11-01

We present a 64x48 pixel 2D electro-optical terahertz (THz) imaging system using a photonic mixing device time-of-flight camera as an optical demodulating detector array. The combination of electro-optic detection with a time-of-flight camera increases sensitivity drastically, enabling the use of a nonamplified laser source for high-resolution real-time THz electro-optic imaging.

Accuracy assessment of biomass and forested area classification from modis, landstat-tm satellite imagery and forest inventory plot data

Treesearch

Dumitru Salajanu; Dennis M. Jacobs

2007-01-01

The objective of this study was to determine how well forestfnon-forest and biomass classifications obtained from Landsat-TM and MODIS satellite data modeled with FIA plots, compare to each other and with forested area and biomass estimates from the national inventory data, as well as whether there is an increase in overall accuracy when pixel size (spatial resolution...

Change detection from remotely sensed images: From pixel-based to object-based approaches

NASA Astrophysics Data System (ADS)

Hussain, Masroor; Chen, Dongmei; Cheng, Angela; Wei, Hui; Stanley, David

2013-06-01

The appetite for up-to-date information about earth's surface is ever increasing, as such information provides a base for a large number of applications, including local, regional and global resources monitoring, land-cover and land-use change monitoring, and environmental studies. The data from remote sensing satellites provide opportunities to acquire information about land at varying resolutions and has been widely used for change detection studies. A large number of change detection methodologies and techniques, utilizing remotely sensed data, have been developed, and newer techniques are still emerging. This paper begins with a discussion of the traditionally pixel-based and (mostly) statistics-oriented change detection techniques which focus mainly on the spectral values and mostly ignore the spatial context. This is succeeded by a review of object-based change detection techniques. Finally there is a brief discussion of spatial data mining techniques in image processing and change detection from remote sensing data. The merits and issues of different techniques are compared. The importance of the exponential increase in the image data volume and multiple sensors and associated challenges on the development of change detection techniques are highlighted. With the wide use of very-high-resolution (VHR) remotely sensed images, object-based methods and data mining techniques may have more potential in change detection.

How colorful! A feature it is, isn't it?

NASA Astrophysics Data System (ADS)

Lebowsky, Fritz

2015-01-01

A display's color subpixel geometry provides an intriguing opportunity for improving readability of text. True type fonts can be positioned at the precision of subpixel resolution. With such a constraint in mind, how does one need to design font characteristics? On the other hand, display manufactures try hard in addressing the color display's dilemma: smaller pixel pitch and larger display diagonals strongly increase the total number of pixels. Consequently, cost of column and row drivers as well as power consumption increase. Perceptual color subpixel rendering using color component subsampling may save about 1/3 of color subpixels (and reduce power dissipation). This talk will try to elaborate the following questions, based on simulation of several different layouts of subpixel matrices: Up to what level are display device constraints compatible with software specific ideas of rendering text? How much of color contrast will remain? How to best consider preferred viewing distance for readability of text? How much does visual acuity vary at 20/20 vision? Can simplified models of human visual color perception be easily applied to text rendering on displays? How linear is human visual contrast perception around band limit of a display's spatial resolution? How colorful does the rendered text appear on the screen? How much does viewing angle influence the performance of subpixel layouts and color subpixel rendering?

The High Resolution Stereo Camera (HRSC) of Mars Express and its approach to science analysis and mapping for Mars and its satellites

NASA Astrophysics Data System (ADS)

Gwinner, K.; Jaumann, R.; Hauber, E.; Hoffmann, H.; Heipke, C.; Oberst, J.; Neukum, G.; Ansan, V.; Bostelmann, J.; Dumke, A.; Elgner, S.; Erkeling, G.; Fueten, F.; Hiesinger, H.; Hoekzema, N. M.; Kersten, E.; Loizeau, D.; Matz, K.-D.; McGuire, P. C.; Mertens, V.; Michael, G.; Pasewaldt, A.; Pinet, P.; Preusker, F.; Reiss, D.; Roatsch, T.; Schmidt, R.; Scholten, F.; Spiegel, M.; Stesky, R.; Tirsch, D.; van Gasselt, S.; Walter, S.; Wählisch, M.; Willner, K.

2016-07-01

The High Resolution Stereo Camera (HRSC) of ESA's Mars Express is designed to map and investigate the topography of Mars. The camera, in particular its Super Resolution Channel (SRC), also obtains images of Phobos and Deimos on a regular basis. As HRSC is a push broom scanning instrument with nine CCD line detectors mounted in parallel, its unique feature is the ability to obtain along-track stereo images and four colors during a single orbital pass. The sub-pixel accuracy of 3D points derived from stereo analysis allows producing DTMs with grid size of up to 50 m and height accuracy on the order of one image ground pixel and better, as well as corresponding orthoimages. Such data products have been produced systematically for approximately 40% of the surface of Mars so far, while global shape models and a near-global orthoimage mosaic could be produced for Phobos. HRSC is also unique because it bridges between laser altimetry and topography data derived from other stereo imaging instruments, and provides geodetic reference data and geological context to a variety of non-stereo datasets. This paper, in addition to an overview of the status and evolution of the experiment, provides a review of relevant methods applied for 3D reconstruction and mapping, and respective achievements. We will also review the methodology of specific approaches to science analysis based on joint analysis of DTM and orthoimage information, or benefitting from high accuracy of co-registration between multiple datasets, such as studies using multi-temporal or multi-angular observations, from the fields of geomorphology, structural geology, compositional mapping, and atmospheric science. Related exemplary results from analysis of HRSC data will be discussed. After 10 years of operation, HRSC covered about 70% of the surface by panchromatic images at 10-20 m/pixel, and about 97% at better than 100 m/pixel. As the areas with contiguous coverage by stereo data are increasingly abundant, we also present original data related to the analysis of image blocks and address methodology aspects of newly established procedures for the generation of multi-orbit DTMs and image mosaics. The current results suggest that multi-orbit DTMs with grid spacing of 50 m can be feasible for large parts of the surface, as well as brightness-adjusted image mosaics with co-registration accuracy of adjacent strips on the order of one pixel, and at the highest image resolution available. These characteristics are demonstrated by regional multi-orbit data products covering the MC-11 (East) quadrangle of Mars, representing the first prototype of a new HRSC data product level.

High-Resolution Topography and its Implications for the Formation of Europa's Ridged Plains

NASA Astrophysics Data System (ADS)

Leonard, E. J.; Pappalardo, R. T.; Yin, A.; Patthoff, D. A.; Schenk, P.

2015-12-01

The Galileo Solid State Imager (SSI) recorded nine very high-resolution frames—eight at 12 m/pixel and one at 6 m/pixel—during the E12 flyby of Europa in Dec. 1997. To understand the implications for the small-scale structure and evolution of Europa, we mosaicked these frames (observations 12ESMOTTLE01 and 02, incidence ≈18°, emission ≈77°) into their regional context (part of observation 11ESREGMAP01, 220 m/pixel, incidence ≈74°, emission ≈23°). The topography data, which was created from the image mosaic overlaps, is sparse and segmented over the high-resolution images but connected by the underlying regional resolution topography. The high-resolution topography (24 m/pixel) is among the best for the current Europan dataset. From this dataset we ascertain the root mean square, or RMS, slope for some of the most common Europan surface features in a new region. We also employ a Fourier Transform method previously used on Ganymede and on other areas of Europa (Patel et al., 1999 JGR), to derive common wavelengths for the subunits of the ubiquitous ridged plains terrain. These results have important implications for differentiating between possible formation mechanisms—extensional tilt blocks (Pappalardo et al., 1995 JGR) or folds (Leonard et al., 2015 LPSC Abstract)—and for potential future missions. We continue this method for another high-resolution region taken in the E12 orbit, WEDGES01 and 02, with the specific goal of investigating how the variations in ridged plains morphologies relate across the surface of Europa.

Development of High Resolution Mirrors and Cd-Zn-Te Detectors for Hard X-ray Astronomy

NASA Technical Reports Server (NTRS)

Ramsey, Brian D.; Speegle, Chet O.; Gaskin, Jessica; Sharma, Dharma; Engelhaupt, Darell; Six, N. Frank (Technical Monitor)

2002-01-01

We describe the fabrication and implementation of a high-resolution conical, grazing- incidence, hard X-ray (20-70 keV) telescope. When flown aboard stratospheric balloons, these mirrors are used to image cosmic sources such as supernovae, neutron stars, and quasars. The fabrication process involves generating super-polished mandrels, mirror shell electroforming, and mirror testing. The cylindrical mandrels consist of two conical segments; each segment is approximately 305 mm long. These mandrels are first, precision ground to within approx. 1.0 micron straightness along each conical segment and then lapped and polished to less than 0.5 micron straightness. Each mandrel segment is the super-polished to an average surface roughness of approx. 3.25 angstrom rms. By mirror shell replication, this combination of good figure and low surface roughness has enabled us to achieve 15 arcsec, confirmed by X-ray measurements in the Marshall Space Flight Center 102 meter test facility. To image the focused X-rays requires a focal plane detector with appropriate spatial resolution. For 15 arcsec optics of 6 meter focal length, this resolution must be around 200 microns. In addition, the detector must have a high efficiency, relatively high energy resolution, and low background. We are currently developing Cadmium-Zinc-Telluride fine-pixel detectors for this purpose. The detectors under study consist of a 16x16 pixel array with a pixel pitch of 300 microns and are 1 mm and 2 mm thick. At 60 keV, the measured energy resolution is around 2%.

Design, optimization and evaluation of a "smart" pixel sensor array for low-dose digital radiography

NASA Astrophysics Data System (ADS)

Wang, Kai; Liu, Xinghui; Ou, Hai; Chen, Jun

2016-04-01

Amorphous silicon (a-Si:H) thin-film transistors (TFTs) have been widely used to build flat-panel X-ray detectors for digital radiography (DR). As the demand for low-dose X-ray imaging grows, a detector with high signal-to-noise-ratio (SNR) pixel architecture emerges. "Smart" pixel is intended to use a dual-gate photosensitive TFT for sensing, storage, and switch. It differs from a conventional passive pixel sensor (PPS) and active pixel sensor (APS) in that all these three functions are combined into one device instead of three separate units in a pixel. Thus, it is expected to have high fill factor and high spatial resolution. In addition, it utilizes the amplification effect of the dual-gate photosensitive TFT to form a one-transistor APS that leads to a potentially high SNR. This paper addresses the design, optimization and evaluation of the smart pixel sensor and array for low-dose DR. We will design and optimize the smart pixel from the scintillator to TFT levels and validate it through optical and electrical simulation and experiments of a 4x4 sensor array.

High-resolution photography of clouds from the surface: Retrieval of optical depth of thin clouds down to centimeter scales: High-Resolution Photography of Clouds

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schwartz, Stephen E.; Huang, Dong; Vladutescu, Daniela Viviana

This article describes the approach and presents initial results, for a period of several minutes in north central Oklahoma, of an examination of clouds by high resolution digital photography from the surface looking vertically upward. A commercially available camera having 35-mm equivalent focal length up to 1200 mm (nominal resolution as fine as 6 µrad, which corresponds to 9 mm for cloud height 1.5 km) is used to obtain a measure of zenith radiance of a 30 m × 30 m domain as a two-dimensional image consisting of 3456 × 3456 pixels (12 million pixels). Downwelling zenith radiance varies substantiallymore » within single images and between successive images obtained at 4-s intervals. Variation in zenith radiance found on scales down to about 10 cm is attributed to variation in cloud optical depth (COD). Attention here is directed primarily to optically thin clouds, COD less than about 2. A radiation transfer model used to relate downwelling zenith radiance to COD and to relate the counts in the camera image to zenith radiance, permits determination of COD on a pixel-by-pixel basis. COD for thin clouds determined in this way exhibits considerable variation, for example, an order of magnitude within 15 m, a factor of 2 within 4 m, and 25% (0.12 to 0.15) over 14 cm. In conclusion, this approach, which examines cloud structure on scales 3 to 5 orders of magnitude finer than satellite products, opens new avenues for examination of cloud structure and evolution.« less

Results from a 64-pixel PIN-diode detector system for low-energy beta-electrons

NASA Astrophysics Data System (ADS)

Wuestling, Sascha; Fraenkle, F.; Habermehl, F.; Renschler, P.; Steidl, M.

2010-12-01

The KATRIN neutrino mass experiment is based on a precise energy measurement (Δ E/ E=5×10 -5) of electrons emerging from tritium beta decay ( Emax=18.6 keV). This is done by a large electrostatic retarding spectrometer (MAC-E Filter), which is followed by an electron detector. Key requirements for this detector are a large sensitive area (˜80 cm 2), a certain energy resolution (Δ E=600 eV @ 18.6 keV) but also a certain spatial resolution (˜3 mm), which leads to a multi-pixel design. As a tentative design on the way to the final detector, but also for operational service on the so-called pre-spectrometer experiment, a detector system with a reduced size (16 cm 2) and a reduced pixel number (64), making use of a monolithic segmented silicon PIN diode, was designed and built. While the design and very first measurements have been presented in Wuestling et al. [6], this publication shows the operational performance of the detector system. The robust concept of the electronics allowed adaptation to mechanically different experimental setups. The spacial resolution of the detector system proved to be essential in examining Penning trap induced background and other effects in the pre-spectrometer experiment. The detector performance test runs include energy resolution and calibration, background rates, correlation between pixels (crosstalk), spatially resolved rate analysis, and a dead-layer measurement [7]. The detector allows for background searches with a sensitivity as low as 1.3×10 -3 cps/cm 2 in the energy range of 20 keV. This allows the pre-spectrometer to be characterized with e-gun illumination with a signal to background ratio of better than 10 5 and the search for ultra low Penning discharge emissions.

Characterization of the energy resolution and the tracking capabilities of a hybrid pixel detector with CdTe-sensor layer for a possible use in a neutrinoless double beta decay experiment

NASA Astrophysics Data System (ADS)

Filipenko, Mykhaylo; Gleixner, Thomas; Anton, Gisela; Durst, Jürgen; Michel, Thilo

2013-04-01

Many different experiments are being developed to explore the existence of the neutrinoless double beta decay (0 νββ) since it would imply fundamental consequences for particle physics. In this work we present results on the evaluation of Timepix detectors with cadmium-telluride sensor material to search for 0 νββ in 116Cd. This work was carried out with the COBRA collaboration and the Medipix collaboration. Due to the relatively small pixel dimension of 110×110×1000 μm3 the energy deposited by particles typically extends over several detector pixels leading to a track in the pixel matrix. We investigated the separation power regarding different event-types like α-particles, atmospheric muons, single electrons and electron-positron pairs produced at a single vertex. We achieved excellent classification power for α-particles and muons. In addition, we achieved good separation power between single electron and electron-positron pair production events. These separation abilities indicate a very good background reduction for the 0 νββ search. Further, in order to distinguish between 2 νββ and 0 νββ, the energy resolution is of particular importance. We carried out simulations which demonstrate that an energy resolution of 0.43 % is achievable at the Q-value for 0 νββ of 116Cd at 2.814 MeV. We measured an energy resolution of 1.6 % at a nominal energy of 1589 keV for electron-positron tracks which is about two times worse that predicted by our simulations. This deviation is probably due to the problem of detector calibration at energies above 122 keV which is discussed in this paper as well.

High-resolution photography of clouds from the surface: Retrieval of optical depth of thin clouds down to centimeter scales: High-Resolution Photography of Clouds

DOE PAGES

Schwartz, Stephen E.; Huang, Dong; Vladutescu, Daniela Viviana

2017-03-08

This article describes the approach and presents initial results, for a period of several minutes in north central Oklahoma, of an examination of clouds by high resolution digital photography from the surface looking vertically upward. A commercially available camera having 35-mm equivalent focal length up to 1200 mm (nominal resolution as fine as 6 µrad, which corresponds to 9 mm for cloud height 1.5 km) is used to obtain a measure of zenith radiance of a 30 m × 30 m domain as a two-dimensional image consisting of 3456 × 3456 pixels (12 million pixels). Downwelling zenith radiance varies substantiallymore » within single images and between successive images obtained at 4-s intervals. Variation in zenith radiance found on scales down to about 10 cm is attributed to variation in cloud optical depth (COD). Attention here is directed primarily to optically thin clouds, COD less than about 2. A radiation transfer model used to relate downwelling zenith radiance to COD and to relate the counts in the camera image to zenith radiance, permits determination of COD on a pixel-by-pixel basis. COD for thin clouds determined in this way exhibits considerable variation, for example, an order of magnitude within 15 m, a factor of 2 within 4 m, and 25% (0.12 to 0.15) over 14 cm. In conclusion, this approach, which examines cloud structure on scales 3 to 5 orders of magnitude finer than satellite products, opens new avenues for examination of cloud structure and evolution.« less

Generation of the global cloud free data set of MODIS

NASA Astrophysics Data System (ADS)

Oguro, Y.; Tsuchiya, K.

To extract temporal change of the land cover from remotely sensed data from space the generation of the reliable cloud free data set is the first priority item With the objectives of generating accurate global basic data and to find the effects of spectral and spatial resolution differences and observation time an attempt is made to generate reliable global cloud free data set of Terra and Aqua MODIS utilizing personal computers Out of 36 bands seven bands with similar spectral features to those of Landsat TM i e Band 1 through 7 are selected These bands cover the most important spectra to derive landcover features The procedure of the data set generation is as follows 1 Download the global Terra and Aqua MODIS day time data MOD02 Level-1B Calibrated Geolocation Data Set of 250 meter Band 1 and 2 and 500 meter Band 3 through 7 resolution from NASA web site 2 Separate the data into several BSQ Band SeQuential image and several text geolocation information of pixels files 3 The geolocation information is given to the pixels of several kms interval Based on the information resampling of the data are made at 1 2 and 1 4 degrees intervals of latitude and longitude thus the resampled pixels are distributed in the latitude and longitudinal axis plane at 1 4 degrees high resolution and 1 2 degrees low resolution intervals 4 A global data for one day is composed 5 Compute NDVI for each pixel 6 Compare the value of NDVI of successive days and keep the larger NDVI At the same time keep the values of each band of the day of the larger

Update on High-Resolution Geodetically Controlled LROC Polar Mosaics

NASA Astrophysics Data System (ADS)

Archinal, B.; Lee, E.; Weller, L.; Richie, J.; Edmundson, K.; Laura, J.; Robinson, M.; Speyerer, E.; Boyd, A.; Bowman-Cisneros, E.; Wagner, R.; Nefian, A.

2015-10-01

We describe progress on high-resolution (1 m/pixel) geodetically controlled LROC mosaics of the lunar poles, which can be used for locating illumination resources (for solar power or cold traps) or landing site and surface operations planning.

Remote sensing of Alaskan boreal forest fires at the pixel and sub-pixel level: multi-sensor approaches and sensitivity analysis

NASA Astrophysics Data System (ADS)

Waigl, C.; Stuefer, M.; Prakash, A.

2013-12-01

Wildfire is the main disturbance regime of the boreal forest ecosystem, a region acutely sensitive to climate change. Large fires impact the carbon cycle, permafrost, and air quality on a regional and even hemispheric scale. Because of their significance as a hazard to human health and economic activity, monitoring wildfires is relevant not only to science but also to government agencies. The goal of this study is to develop pathways towards a near real-time assessment of fire characteristics in the boreal zones of Alaska based on satellite remote sensing data. We map the location of active burn areas and derive fire parameters such as fire temperature, intensity, stage (smoldering or flaming), emission injection points, carbon consumed, and energy released. For monitoring wildfires in the sub-arctic region, we benefit from the high temporal resolution of data (as high as 8 images a day) from MODIS on the Aqua and Terra platforms and VIIRS on NPP/Suomi, downlinked and processed to level 1 by the Geographic Information Network of Alaska at the University of Alaska Fairbanks. To transcend the low spatial resolution of these sensors, a sub-pixel analysis is carried out. By applying techniques from Bayesian inverse modeling to Dozier's two-component approach, uncertainties and sensitivity of the retrieved fire temperatures and fractional pixel areas to background temperature and atmospheric factors are assessed. A set of test cases - large fires from the 2004 to 2013 fire seasons complemented by a selection of smaller burns at the lower end of the MODIS detection threshold - is used to evaluate the methodology. While the VIIRS principal fire detection band M13 (centered at 4.05 μm, similar to MODIS bands 21 and 22 at 3.959 μm) does not usually saturate for Alaskan wildfire areas, the thermal IR band M15 (10.763 μm, comparable to MODIS band 31 at 11.03 μm) indeed saturates for a percentage, though not all, of the fire pixels of intense burns. As this limits the application of the classical version of Dozier's model for this particular combination to lower intensity and smaller fires, or smaller fractional fire areas, other VIIRS band combinations are evaluated as well. Furthermore, the higher spatial resolution of the VIIRS sensor compared to MODIS and its constant along-scan resolution DNB (day/night band) dataset provide additional options for fire mapping, detection and quantification. Higher spatial resolution satellite-borne remote sensing data is used to validate the pixel and sub-pixel level analysis and to assess lower detection thresholds. For each sample fire, moderate-resolution imagery is paired with data from the ASTER instrument (simultaneous with MODIS data on the Terra platform) and/or Landsat scenes acquired in close temporal proximity. To complement the satellite-borne imagery, aerial surveys using a FLIR thermal imaging camera with a broadband TIR sensor provide additional ground truthing and a validation of fire location and background temperature.

Structural colour printing from a reusable generic nanosubstrate masked for the target image

NASA Astrophysics Data System (ADS)

Rezaei, M.; Jiang, H.; Kaminska, B.

2016-02-01

Structural colour printing has advantages over traditional pigment-based colour printing. However, the high fabrication cost has hindered its applications in printing large-area images because each image requires patterning structural pixels in nanoscale resolution. In this work, we present a novel strategy to print structural colour images from a pixelated substrate which is called a nanosubstrate. The nanosubstrate is fabricated only once using nanofabrication tools and can be reused for printing a large quantity of structural colour images. It contains closely packed arrays of nanostructures from which red, green, blue and infrared structural pixels can be imprinted. To print a target colour image, the nanosubstrate is first covered with a mask layer to block all the structural pixels. The mask layer is subsequently patterned according to the target colour image to make apertures of controllable sizes on top of the wanted primary colour pixels. The masked nanosubstrate is then used as a stamp to imprint the colour image onto a separate substrate surface using nanoimprint lithography. Different visual colours are achieved by properly mixing the red, green and blue primary colours into appropriate ratios controlled by the aperture sizes on the patterned mask layer. Such a strategy significantly reduces the cost and complexity of printing a structural colour image from lengthy nanoscale patterning into high throughput micro-patterning and makes it possible to apply structural colour printing in personalized security features and data storage. In this paper, nanocone array grating pixels were used as the structural pixels and the nanosubstrate contains structures to imprint the nanocone arrays. Laser lithography was implemented to pattern the mask layer with submicron resolution. The optical properties of the nanocone array gratings are studied in detail. Multiple printed structural colour images with embedded covert information are demonstrated.

Glacier Melt Detection in Complex Terrain Using New AMSR-E Calibrated Enhanced Daily EASE-Grid 2.0 Brightness Temperature (CETB) Earth System Data Record

NASA Astrophysics Data System (ADS)

Ramage, J. M.; Brodzik, M. J.; Hardman, M.

2016-12-01

Passive microwave (PM) 18 GHz and 36 GHz horizontally- and vertically-polarized brightness temperatures (Tb) channels from the Advanced Microwave Scanning Radiometer for EOS (AMSR-E) have been important sources of information about snow melt status in glacial environments, particularly at high latitudes. PM data are sensitive to the changes in near-surface liquid water that accompany melt onset, melt intensification, and refreezing. Overpasses are frequent enough that in most areas multiple (2-8) observations per day are possible, yielding the potential for determining the dynamic state of the snow pack during transition seasons. AMSR-E Tb data have been used effectively to determine melt onset and melt intensification using daily Tb and diurnal amplitude variation (DAV) thresholds. Due to mixed pixels in historically coarse spatial resolution Tb data, melt analysis has been impractical in ice-marginal zones where pixels may be only fractionally snow/ice covered, and in areas where the glacier is near large bodies of water: even small regions of open water in a pixel severely impact the microwave signal. We use the new enhanced-resolution Calibrated Passive Microwave Daily EASE-Grid 2.0 Brightness Temperature (CETB) Earth System Data Record product's twice daily obserations to test and update existing snow melt algorithms by determining appropriate melt thresholds for both Tb and DAV for the CETB 18 and 36 GHz channels. We use the enhanced resolution data to evaluate melt characteristics along glacier margins and melt transition zones during the melt seasons in locations spanning a wide range of melt scenarios, including the Patagonian Andes, the Alaskan Coast Range, and the Russian High Arctic icecaps. We quantify how improvement of spatial resolution from the original 12.5 - 25 km-scale pixels to the enhanced resolution of 3.125 - 6.25 km improves the ability to evaluate melt timing across boundaries and transition zones in diverse glacial environments.

Chromatic Modulator for a High-Resolution CCD or APS

NASA Technical Reports Server (NTRS)

Hartley, Frank; Hull, Anthony

2008-01-01

A chromatic modulator has been proposed to enable the separate detection of the red, green, and blue (RGB) color components of the same scene by a single charge-coupled device (CCD), active-pixel sensor (APS), or similar electronic image detector. Traditionally, the RGB color-separation problem in an electronic camera has been solved by use of either (1) fixed color filters over three separate image detectors; (2) a filter wheel that repeatedly imposes a red, then a green, then a blue filter over a single image detector; or (3) different fixed color filters over adjacent pixels. The use of separate image detectors necessitates precise registration of the detectors and the use of complicated optics; filter wheels are expensive and add considerably to the bulk of the camera; and fixed pixelated color filters reduce spatial resolution and introduce color-aliasing effects. The proposed chromatic modulator would not exhibit any of these shortcomings. The proposed chromatic modulator would be an electromechanical device fabricated by micromachining. It would include a filter having a spatially periodic pattern of RGB strips at a pitch equal to that of the pixels of the image detector. The filter would be placed in front of the image detector, supported at its periphery by a spring suspension and electrostatic comb drive. The spring suspension would bias the filter toward a middle position in which each filter strip would be registered with a row of pixels of the image detector. Hard stops would limit the excursion of the spring suspension to precisely one pixel row above and one pixel row below the middle position. In operation, the electrostatic comb drive would be actuated to repeatedly snap the filter to the upper extreme, middle, and lower extreme positions. This action would repeatedly place a succession of the differently colored filter strips in front of each pixel of the image detector. To simplify the processing, it would be desirable to encode information on the color of the filter strip over each row (or at least over some representative rows) of pixels at a given instant of time in synchronism with the pixel output at that instant.

Development of Position-Sensitive Magnetic Calorimeters for X-Ray Astronomy

NASA Technical Reports Server (NTRS)

Bandler, SImon; Stevenson, Thomas; Hsieh, Wen-Ting

2011-01-01

Metallic magnetic calorimeters (MMC) are one of the most promising devices to provide very high energy resolution needed for future astronomical x-ray spectroscopy. MMC detectors can be built to large detector arrays having thousands of pixels. Position-sensitive magnetic (PoSM) microcalorimeters consist of multiple absorbers thermally coupled to one magnetic micro calorimeter. Each absorber element has a different thermal coupling to the MMC, resulting in a distribution of different pulse shapes and enabling position discrimination between the absorber elements. PoSMs therefore achieve the large focal plane area with fewer number of readout channels without compromising spatial sampling. Excellent performance of PoSMs was achieved by optimizing the designs of key parameters such as the thermal conductance among the absorbers, magnetic sensor, and heat sink, as well as the absorber heat capacities. Micro fab ri - cation techniques were developed to construct four-absorber PoSMs, in which each absorber consists of a two-layer composite of bismuth and gold. The energy resolution (FWHM full width at half maximum) was measured to be better than 5 eV at 6 keV x-rays for all four absorbers. Position determination was demonstrated with pulse-shape discrimination, as well as with pulse rise time. X-ray microcalorimeters are usually designed to thermalize as quickly as possible to avoid degradation in energy resolution from position dependence to the pulse shapes. Each pixel consists of an absorber and a temperature sensor, both decoupled from the cold bath through a weak thermal link. Each pixel requires a separate readout channel; for instance, with a SQUID (superconducting quantum interference device). For future astronomy missions where thousands to millions of resolution elements are required, having an individual SQUID readout channel for each pixel becomes difficult. One route to attaining these goals is a position-sensitive detector in which a large continuous or pixilated array of x-ray absorbers shares fewer numbers of temperature sensors. A means of discriminating the signals from different absorber positions, however, needs to be built into the device for each sensor. The design concept for the device is such that the shape of the temperature pulse with time depends on the location of the absorber. This inherent position sensitivity of the signal is then analyzed to determine the location of the event precisely, effectively yielding one device with many sub-pixels. With such devices, the total number of electronic channels required to read out a given number of pixels is significantly reduced. PoSMs were developed that consist of four discrete absorbers connected to a single magnetic sensor. The design concept can be extended to more than four absorbers per sensor. The thermal conductance between the sensor and each absorber is different by design and consequently, the pulse shapes are different depending upon which absorber the xrays are received, allowing position discrimination. A magnetic sensor was used in which a paramagnetic Au:Er temperature-sensitive material is located in a weak magnetic field. Deposition of energy from an x-ray photon causes an increase in temperature, which leads to a change of magnetization of the paramagnetic sensor, which is subsequently read out using a low noise dc-SQUID. The PoSM microcalorimeters are fully microfabricated: the Au:Er sensor is located above the meander, with a thin insulation gap in between. For this position-sensitive device, four electroplated absorbers are thermally linked to the sensor via heat links of different thermal conductance. One pixel is identical to that of a single-pixel design, consisting of an overhanging absorber fabricated directly on top of the sensor. It is therefore very strongly thermally coupled to it. The three other absorbers are supported directly on a silicon-nitride membrane. These absorbers are thermally coupled to the sensor via Ti (5 nm)/Au250 nm) metal links. The strength of the links is parameterized by the number of gold squares making up the link. For detector performance, experimentally different pulse-shapes were demonstrated with 6 keV x-rays, which clearly show different rise times for different absorber positions. For energy resolution measurement, the PoSM was operated at 32 mK with an applied field that was generated using a persistent current of 50 mA. Over the four pixels, energy resolution ranges from 4.4 to 4.7 eV were demonstrated.

Pixel structures to compensate nonuniform threshold voltage and mobility of polycrystalline silicon thin-film transistors using subthreshold current for large-size active matrix organic light-emitting diode displays

NASA Astrophysics Data System (ADS)

Na, Jun-Seok; Kwon, Oh-Kyong

2014-01-01

We propose pixel structures for large-size and high-resolution active matrix organic light-emitting diode (AMOLED) displays using a polycrystalline silicon (poly-Si) thin-film transistor (TFT) backplane. The proposed pixel structures compensate the variations of the threshold voltage and mobility of the driving TFT using the subthreshold current. The simulated results show that the emission current error of the proposed pixel structure B ranges from -2.25 to 2.02 least significant bit (LSB) when the variations of the threshold voltage and mobility of the driving TFT are ±0.5 V and ±10%, respectively.

A Topographic Image Map of The Mc-18 Quadrangle "coprates" At 1: 2,000,000 Using Data Obtained From The Mars Orbiter Camera and The Mars Orbiter Laser Altimeter of Mars Global Surveyor

NASA Astrophysics Data System (ADS)

Niedermaier, G.; Wählisch, M.; van Gasselt, S.; Scholten, F.; Wewel, F.; Roatsch, T.; Matz, K.-D.; Jaumann, R.

We present a new topographic image map of Mars using 8 bit data obtained from the Mars Orbiter Camera (MOC) of the Mars Global Surveyor (MGS) [1]. The new map covers the Mars surface from 270 E (90 W) to 315 E (45 W) and from 0 North to 30 South with a resolution of 231.529 m/pixel (256 pixel/degree). For map creation, digital image processing methods have been applied. Furthermore, we managed to de- velop a general processing method for creating image mosaics based on MOC data. From a total amount of 66,081 images, 4,835 images (4,339 Context and 496 Geodesy images [3]) were finally used for the creation of the mosaic. After radiometric and brightness corrections, the images were Mars referenced [5], geometrically [6] cor- rected and sinusoidal map projected [4] using a global Martian Digital Terrain Model (DTM), developed by the DLR and based on MGS Mars Orbiter Laser Altimeter (MOLA) topographic datasets [2]. Three layers of MOC mosaics were created, which were stacked afterwards. The upper layer contains the context images with a resolution < 250 m/pixel. The middle layer contains the images of the Geodesy Campaign with a resolution < 250 m/pixel. The bottom layer consists of the Geodesy Campaign im- ages with a resolution > 250 m/pixel and < 435 m/pixel. The contour lines have been extracted from the global Martian DTM, developed at DLR. The contour data were imported as vector data into Macromedia Freehand as separate layer and corrected interactively. The map format of 1,15 m × 1,39 m represents the western part of the MDIM2 j quadrangle. The map is used for geological and morphological interpreta- tions in order to review and improve our current Viking-based knowledge about the Martian surface. References: [1] www.msss.com [2] wufs.wustl.edu [3] Caplinger, M. and M. Malin, The Mars Orbiter Camera Geodesy Campaign, JGR, in press. [4] Scholten, F., Vol XXXI, Part B2, Wien, 1996, p.351-356 [5] naif.jpl.nasa.gov [6] Kirk, R.L. et al., Geometric Calibration of the Mars Orbiter Cameras and Coalignment with Mars Orbiter Laser Altimeter, (abstract #1863), LPSC XXXII, 2001

Pixel super resolution using wavelength scanning

DTIC Science & Technology

2016-04-08

the light source is adjusted to ~20 μW. The image sensor chip is a color CMOS sensor chip with a pixel size of 1.12 μm manufactured for cellphone...pitch (that is, ~ 1 μm in Figure 3a, using a CMOS sensor that has a 1.12-μm pixel pitch). For the same configuration depicted in Figure 3, utilizing...section). The a Lens-free raw holograms captured by 1.12 μm CMOS image sensor Field of view ≈ 20.5 mm2 Angle change directions for synthetic aperture

Microradiography with Semiconductor Pixel Detectors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jakubek, Jan; Cejnarova, Andrea; Dammer, Jiri

High resolution radiography (with X-rays, neutrons, heavy charged particles, ...) often exploited also in tomographic mode to provide 3D images stands as a powerful imaging technique for instant and nondestructive visualization of fine internal structure of objects. Novel types of semiconductor single particle counting pixel detectors offer many advantages for radiation imaging: high detection efficiency, energy discrimination or direct energy measurement, noiseless digital integration (counting), high frame rate and virtually unlimited dynamic range. This article shows the application and potential of pixel detectors (such as Medipix2 or TimePix) in different fields of radiation imaging.

Chip-scale fluorescence microscope based on a silo-filter complementary metal-oxide semiconductor image sensor.

PubMed

Ah Lee, Seung; Ou, Xiaoze; Lee, J Eugene; Yang, Changhuei

2013-06-01

We demonstrate a silo-filter (SF) complementary metal-oxide semiconductor (CMOS) image sensor for a chip-scale fluorescence microscope. The extruded pixel design with metal walls between neighboring pixels guides fluorescence emission through the thick absorptive filter to the photodiode of a pixel. Our prototype device achieves 13 μm resolution over a wide field of view (4.8 mm × 4.4 mm). We demonstrate bright-field and fluorescence longitudinal imaging of living cells in a compact, low-cost configuration.

Note: Operation of gamma-ray microcalorimeters at elevated count rates using filters with constraints

DOE Office of Scientific and Technical Information (OSTI.GOV)

Alpert, B. K.; Horansky, R. D.; Bennett, D. A.

Microcalorimeter sensors operated near 0.1 K can measure the energy of individual x- and gamma-ray photons with significantly more precision than conventional semiconductor technologies. Both microcalorimeter arrays and higher per pixel count rates are desirable to increase the total throughput of spectrometers based on these devices. The millisecond recovery time of gamma-ray microcalorimeters and the resulting pulse pileup are significant obstacles to high per pixel count rates. Here, we demonstrate operation of a microcalorimeter detector at elevated count rates by use of convolution filters designed to be orthogonal to the exponential tail of a preceding pulse. These filters allow operationmore » at 50% higher count rates than conventional filters while largely preserving sensor energy resolution.« less

A phase-based stereo vision system-on-a-chip.

PubMed

Díaz, Javier; Ros, Eduardo; Sabatini, Silvio P; Solari, Fabio; Mota, Sonia

2007-02-01

A simple and fast technique for depth estimation based on phase measurement has been adopted for the implementation of a real-time stereo system with sub-pixel resolution on an FPGA device. The technique avoids the attendant problem of phase warping. The designed system takes full advantage of the inherent processing parallelism and segmentation capabilities of FPGA devices to achieve a computation speed of 65megapixels/s, which can be arranged with a customized frame-grabber module to process 211frames/s at a size of 640x480 pixels. The processing speed achieved is higher than conventional camera frame rates, thus allowing the system to extract multiple estimations and be used as a platform to evaluate integration schemes of a population of neurons without increasing hardware resource demands.