Optical Fourier techniques for medical image processing and phase contrast imaging
Yelleswarapu, Chandra S.; Kothapalli, Sri-Rajasekhar; Rao, D.V.G.L.N.
2008-01-01
This paper briefly reviews the basics of optical Fourier techniques (OFT) and applications for medical image processing as well as phase contrast imaging of live biological specimens. Enhancement of microcalcifications in a mammogram for early diagnosis of breast cancer is the main focus. Various spatial filtering techniques such as conventional 4f filtering using a spatial mask, photoinduced polarization rotation in photosensitive materials, Fourier holography, and nonlinear transmission characteristics of optical materials are discussed for processing mammograms. We also reviewed how the intensity dependent refractive index can be exploited as a phase filter for phase contrast imaging with a coherent source. This novel approach represents a significant advance in phase contrast microscopy. PMID:18458764
Ito, Satoshi; Yamada, Yoshifumi
2008-08-01
An image reconstruction technique that reduces aliasing artifacts by scalable image reconstruction in magnetic resonance imaging (MRI) is proposed. The signal obtained by the phase-scrambling Fourier transform (PSFT) imaging technique can be transformed to the signal described in the Fresnel transform equation of the objects. Therefore, image reconstruction can be performed not only by inverse FT but also by inverse Fresnel transform. When a phase-scrambling coefficient is given in a certain range, image reconstruction by inverse Fresnel transform allows shrinking of images over rather wide scales. Thus, reduced aliasing images can be reconstructed even from signals that produce serious aliasing artifacts by standard inverse FT reconstruction. Simulation and experimental studies reveal that the proposed method can be used to produce reduced aliasing images. PMID:18666133
Fourier transform image processing techniques for grid-based phase contrast imaging
NASA Astrophysics Data System (ADS)
Tahir, Sajjad; Bashir, Sajid; Petruccelli, Jonathan C.; MacDonald, C. A.
2014-09-01
A recently developed technique for phase imaging using table top sources is to use multiple fine-pitch gratings. However, the strict manufacturing tolerences and precise alignment required have limited the widespread adoption of grating-based techniques. In this work, we employ a technique recently demonstrated by Bennett et al.1 that ultilizes a single grid of much coarser pitch. Phase is extracted using Fourier processing on a single raw image taken using a focused mammography grid. The effects on the final image of varying grid, object, and detector distances, window widths, and of a variety of windowing functions, used to separate the harmonics, were investigated.
Jie Zhao; Dayong Wang; Yunxin Wang; Changgeng Liu; Yan Li; Huakun Cui; Yuhong Wan
2010-01-01
The lensless Fourier transform digital holography has been widely employed in microscopic imaging. It enables quantitative phase analysis for both reflection and transmission objects. The phase image is obtained in the numerical reconstruction procedure. The in-focus reconstruction distance could be determined according to the extremum of the autofocusing criterion function, which is commonly applied in finding the in-focus amplitude image
Combined Fourier amplitude and phase imaging in patients with coronary artery disease.
Alcan, K E; Robeson, W; Graham, M C; Palestro, C; Oliver, F H; Benua, R S
1984-12-01
Fourier amplitude and phase image analysis were evaluated in 66 patients. Thirty patients served as a control group and 36 had coronary artery disease (CAD). Each patient in our control group had a rest and exercise radionuclide cineangiogram (RNCA) study (60 total). The amplitude and phase images for controls were uniform. No statistically significant difference in the histogram distribution of amplitude or phase occurred between rest and exercise. Twenty-five patients with CAD had a prior myocardial infarction (MI). Fourier analysis, when compared to the left ventricular ejection fraction (LVEF) and visual cine wall motion analysis, improved the sensitivity of the rest RNCA study to detect CAD from 68% to 92%. Regional Fourier amplitude and phase image analysis demonstrated an 85% sensitivity in localizing regions of previous infarction. Thirteen of 25 patients with prior MI and an additional 11 patients with recent onset of angina but no previous infarction, had exercise RNCA studies. When compared to cardiac catheterization data, regional Fourier amplitude and phase image analysis demonstrated sensitivities of 87% and 80%, respectively, in correctly identifying clinically significant major coronary artery involvement in these two subsets of patients. Fourier amplitude and phase image analysis were also able to distinguish normals from patients with previous MI, and patients with CAD but no prior infarction. All comparisons were statistically significant. We conclude that the semiquantitative image analysis of Fourier amplitude and phase data increases the clinical utility of the RNCA study in patients with CAD. PMID:6096069
Multiple-image encryption based on phase mask multiplexing in fractional Fourier transform domain.
Liansheng, Sui; Meiting, Xin; Ailing, Tian
2013-06-01
A multiple-image encryption scheme is proposed based on the phase retrieval process and phase mask multiplexing in the fractional Fourier transform domain. First, each original gray-scale image is encoded into a phase only function by using the proposed phase retrieval process. Second, all the obtained phase functions are modulated into an interim, which is encrypted into the final ciphertext by using the fractional Fourier transform. From a plaintext image, a group of phase masks is generated in the encryption process. The corresponding decrypted image can be recovered from the ciphertext only with the correct phase mask group in the decryption process. Simulation results show that the proposed phase retrieval process has high convergence speed, and the encryption algorithm can avoid cross-talk; in addition, its encrypted capacity is considerably enhanced. PMID:23722815
Color image encoding in dual fractional Fourier-wavelet domain with random phases
NASA Astrophysics Data System (ADS)
Chen, Linfei; Zhao, Daomu
2009-09-01
A new cryptology in dual fractional Fourier-wavelet domain is proposed in this paper, which is calculated by discrete fractional Fourier transform and wavelet decomposition. Different random phases are used in different wavelet subbands in encryption. A new color image encoding method is also presented with basic color decomposition and encryption respectively. All the keys, including random phases and fractional orders in R, G and B three channels, should be correctly used in decryption, otherwise people cannot obtain the totally correct information. Some numerical simulations are presented to demonstrate the possibility of the method. It would have widely potential applications in digital color image processing and protection.
NASA Astrophysics Data System (ADS)
Ito, Satoshi; Yamada, Yoshifumi
2002-09-01
Recently, the use of magnetic-resonance-guided navigation to improve the safety and effectiveness of surgical procedures has shown great promise. The purpose of the present study was to develop and demonstrate an imaging strategy that allows surgeons to continue operating without delays caused by imaging. The phase-scrambling Fourier-imaging technique has two prominent characteristics: localized image reconstruction and holographic image reconstruction. The combination of these characteristics allows images to be observed even during the data-acquisition period, because the acquired signal is converted into a hologram and the image is reconstructed instantly in the coherent optical image-processing system. Experimental studies have shown that the phase-scrambling Fourier-imaging technique enables the motion of objects to be imaged more quickly than the standard fast imaging. The proposed running reconstruction strategy can be easily implemented in the well-established magnetic-resonance imaging equipment that is currently in use.
NASA Astrophysics Data System (ADS)
Zhao, Jie; Wang, Dayong; Wang, Yunxin; Liu, Changgeng; Li, Yan; Cui, Huakun; Wan, Yuhong
2010-08-01
The lensless Fourier transform digital holography has been widely employed in microscopic imaging. It enables quantitative phase analysis for both reflection and transmission objects. The phase image is obtained in the numerical reconstruction procedure. The in-focus reconstruction distance could be determined according to the extremum of the autofocusing criterion function, which is commonly applied in finding the in-focus amplitude image of the object. Then the reconstruction distance for the phase image is considered to be equal to the one for the amplitude image. When the object is a pure phase sample, such as the living cell, the minimum value of the autofocusing criterion function should be found to determine the in-focus reconstruction distance. However, in the experiment, the in-focus amplitude image is often not an ideal uniform bright field, so this method will result in some deviation. In this contribution, two derivatives-based criterion functions are applied to the phase image directly to accomplish the in-focus phase contrast imaging, which is more intuitive and precise. In our experiments, the set-up of the lensless Fourier transform digital holography is established firstly. Then the living cervical carcinoma cells are detected. The phase aberration is corrected by two-step algorithm. The final autofocusing results verify the algorithm proposed in this paper.
Paris-Sud XI, Université de
of the Fourier phase information. Quality indices divide into three categories : full- reference, reduced, concluding (in 2006) that "the design of application-specific no-reference quality assessment sys- temsNo-reference image quality assessment and blind deblurring with sharpness metrics exploiting
NASA Astrophysics Data System (ADS)
Jin, Weimin; Yan, Caijie
2007-01-01
The optical image encryption based on multichannel fractional Fourier transform (FRT) and double random phase encoding technique is proposed. Optical principles of encoding and decoding are analyzed in detail. With this method, one can encrypt different parts of input image, respectively. The system security can be improved to some extent, not only because fractional orders and random phase masks in every channel can be set with freedom, but also because the system parameters among all channels are independent. Numerical simulation results of optical image encryption based on four channel FRT and double random phase encoding are given to verify the feasibility of the method.
Single-channel color image encryption using phase retrieve algorithm in fractional Fourier domain
NASA Astrophysics Data System (ADS)
Sui, Liansheng; Xin, Meiting; Tian, Ailing; Jin, Haiyan
2013-12-01
A single-channel color image encryption is proposed based on a phase retrieve algorithm and a two-coupled logistic map. Firstly, a gray scale image is constituted with three channels of the color image, and then permuted by a sequence of chaotic pairs generated by the two-coupled logistic map. Secondly, the permutation image is decomposed into three new components, where each component is encoded into a phase-only function in the fractional Fourier domain with a phase retrieve algorithm that is proposed based on the iterative fractional Fourier transform. Finally, an interim image is formed by the combination of these phase-only functions and encrypted into the final gray scale ciphertext with stationary white noise distribution by using chaotic diffusion, which has camouflage property to some extent. In the process of encryption and decryption, chaotic permutation and diffusion makes the resultant image nonlinear and disorder both in spatial domain and frequency domain, and the proposed phase iterative algorithm has faster convergent speed. Additionally, the encryption scheme enlarges the key space of the cryptosystem. Simulation results and security analysis verify the feasibility and effectiveness of this method.
Color image encryption using iterative phase retrieve process in quaternion Fourier transform domain
NASA Astrophysics Data System (ADS)
Sui, Liansheng; Duan, Kuaikuai
2015-02-01
A single-channel color image encryption method is proposed based on iterative phase iterative process in quaternion Fourier transform domain. First, three components of the plain color image is confused respectively by using cat map. Second, the confused components are combined into a pure quaternion image, which is encode to the phase only function by using an iterative phase retrieval process. Finally, the phase only function is encrypted into the gray scale ciphertext with stationary white noise distribution based on the chaotic diffusion, which has camouflage property to some extent. The corresponding plain color image can be recovered from the ciphertext only with correct keys in the decryption process. Simulation results verify the feasibility and effectiveness of the proposed method.
NASA Astrophysics Data System (ADS)
Zhang, Hao; Zhao, Yan; Gu, Huarong; Tan, Qiaofeng; Cao, Liangcai; Jin, Guofan
2012-11-01
We propose a holographic 3D display system which can produce images with adjustable viewing parameters and eliminated zero-order interruption. The 3D scene is generated from a 3D CAD tool, and point source algorithm is used to generate the holograms. A two-step model is introduced in the computing to generate precise Fourier holograms. A phase-only spatial light modulator (SLM) is used in the optical reconstruction, which can replay clear images for 3D diffusive objects. During optical reconstructing, the viewing angle and image size of the system can be adjusted by changing the parameters of the replay lens. A filter is introduced in the replay system to eliminate the zero-order interruption and increase the 3D image quality. Optical experiments are performed, and the results show that our proposed holographic display system can produce noiseless 3D image reconstructions.
Superresolution imaging method using phase-shifting digital lensless Fourier holography.
Granero, Luis; Micó, Vicente; Zalevsky, Zeev; García, Javier
2009-08-17
A method which is useful for obtaining superresolved imaging in a digital lensless Fourier holographic configuration is presented. By placing a diffraction grating between the input object and the CCD recording device, additional high-order spatial-frequency content of the object spectrum is directed towards the CCD. Unlike other similar methods, the recovery of the different band pass images is performed by inserting a reference beam in on-axis mode and using phase-shifting method. This strategy provides advantages concerning the usage of the whole frequency plane as imaging plane. Thus, the method is no longer limited by the zero order term and the twin image. Finally, the whole process results in a synthetic aperture generation that expands up the system cutoff frequency and yields a superresolution effect. Experimental results validate our concepts for a resolution improvement factor of 3. PMID:19687979
Probing vacuum birefringence by phase-contrast Fourier imaging under fields of high-intensity lasers
Kensuke Homma; Dieter Habs; Toshiki Tajima
2011-04-06
In vacuum high-intensity lasers can cause photon-photon interaction via the process of virtual vacuum polarization which may be measured by the phase velocity shift of photons across intense fields. In the optical frequency domain, the photon-photon interaction is polarization-mediated described by the Euler-Heisenberg effective action. This theory predicts the vacuum birefringence or polarization dependence of the phase velocity shift arising from nonlinear properties in quantum electrodynamics (QED). We suggest a method to measure the vacuum birefringence under intense optical laser fields based on the absolute phase velocity shift by phase-contrast Fourier imaging. The method may serve for observing effects even beyond the QED vacuum polarization.
Fourier plane imaging microscopy
Dominguez, Daniel, E-mail: daniel.dominguez@ttu.edu; Peralta, Luis Grave de [Department of Physics, Texas Tech University, Lubbock, Texas 79409 (United States); Nano Tech Center, Texas Tech University, Lubbock, Texas 79409 (United States); Alharbi, Nouf; Alhusain, Mdhaoui [Department of Physics, Texas Tech University, Lubbock, Texas 79409 (United States); Bernussi, Ayrton A. [Nano Tech Center, Texas Tech University, Lubbock, Texas 79409 (United States); Department of Electrical and Computer Engineering, Texas Tech University, Lubbock, Texas 79409 (United States)
2014-09-14
We show how the image of an unresolved photonic crystal can be reconstructed using a single Fourier plane (FP) image obtained with a second camera that was added to a traditional compound microscope. We discuss how Fourier plane imaging microscopy is an application of a remarkable property of the obtained FP images: they contain more information about the photonic crystals than the images recorded by the camera commonly placed at the real plane of the microscope. We argue that the experimental results support the hypothesis that surface waves, contributing to enhanced resolution abilities, were optically excited in the studied photonic crystals.
Wang, Xiaogang; Zhao, Daomu
2013-09-01
A nonlinear color and grayscale images cryptosystem based on phase-truncated fractional Fourier transform and optical superposition principle is proposed. In order to realize simultaneous encryption of color and grayscale images, each grayscale image is first converted into two phase masks by using an optical coherent superposition, one of which is treated as a part of input information that will be fractional Fourier transformed while the other in the form of a chaotic random phase mask (CRPM) is used as a decryption key. For the purpose of optical performance, all the processes are performed through three channels, i.e., red, green, and blue. Different from most asymmetric encryption methods, the decryption process is designed to be linear for the sake of effective decryption. The encryption level of a double random phase encryption based on phase-truncated Fourier transform is enhanced by extending it into fractional Fourier domain and the load of the keys management and transmission is lightened by using CRPMs. The security of the proposed cryptosystem is discussed and computer simulation results are presented to verify the validity of the proposed method. PMID:24085074
NASA Astrophysics Data System (ADS)
Jericevic, Zeljko; McGavran, Loris; Smith, Louis C.
1991-05-01
The new methodology of chromosome analysis based on eigenanalysis and iterative Fourier synthesis has been developed. The approach is inspired by the analysis developed in electron microscopy of particles, and has been modified to address particular problems of chromosome analysis. Preliminary results on data sets containing 40-80 images for each of the human chromosomes indicate that this methodology provides an improvement of chromosome band resolution and potentially can provide cytogeneticist with some new insights. The proposed procedure is a novel approach in chromosome analysis and represents a significant contribution to quantitative cytogenetics. It opens the possibility of identifying defects in chromosome banding pattern automatically.
Imaging Fourier Transform Spectrometer
Bennett, C.L.; Carter, M.R.; Fields, D.J.; Hernandez, J.
1993-04-14
The operating principles of an Imaging Fourier Transform Spectrometer (IFTS) are discussed. The advantages and disadvantages of such instruments with respect to alternative imaging spectrometers are discussed. The primary advantages of the IFTS are the capacity to acquire more than an order of magnitude more spectral channels than alternative systems with more than an order of magnitude greater etendue than for alternative systems. The primary disadvantage of IFTS, or FTS in general, is the sensitivity to temporal fluctuations, either random or periodic. Data from the IRIFTS (ir IFTS) prototype instrument, sensitive in the infrared, are presented having a spectral sensitivity of 0.01 absorbance units, a spectral resolution of 6 cm{sup {minus}1} over the range 0 to 7899 cm{sup {minus}1}, and a spatial resolution of 2.5 mr.
Holographic image projection using fractional Fourier transformation
NASA Astrophysics Data System (ADS)
Chang, Chenliang; Xia, Jun; Lei, Wei
2012-01-01
A new method of image projection based on fractional Fourier transformation is presented. This method can project an image at any distance after a lens plane. We use a modified Gerschberg-Saxton (GS) iteration algorithm to compute a phase-only hologram. The amplitude distributions both on the hologram plane and image plane are restricted while allowing their phase distributions to drift into an optimum value. The quality of the image projected by fractional Fourier hologram is close to the image projected by Fourier hologram. The RMS error between the projected image and the constrained image is computed in our experiment. A comparison in flexibility of the two projection methods is also discussed.
Electro-optic imaging Fourier transform spectrometer
NASA Technical Reports Server (NTRS)
Chao, Tien-Hsin (Inventor); Znod, Hanying (Inventor)
2009-01-01
An Electro-Optic Imaging Fourier Transform Spectrometer (EOIFTS) for Hyperspectral Imaging is described. The EOIFTS includes an input polarizer, an output polarizer, and a plurality of birefringent phase elements. The relative orientations of the polarizers and birefringent phase elements can be changed mechanically or via a controller, using ferroelectric liquid crystals, to substantially measure the spectral Fourier components of light propagating through the EIOFTS. When achromatic switches are used as an integral part of the birefringent phase elements, the EIOFTS becomes suitable for broadband applications, with over 1 micron infrared bandwidth.
Tian, Lei; Yeh, Li-Hao; Chen, Michael; Waller, Laura
2015-01-01
For centuries, microscopes have had to trade field of view (FOV) for resolution. Recently, a new computational imaging technique, termed Fourier ptychographic microscopy (FPM), circumvents this limit in order to capture gigapixel-scale images having both wide FOV and high resolution. FPM has enormous potential for revolutionizing biomedical microscopy; however, it has until now been limited to fixed samples, since acquisition time is on the order of minutes. Live biological samples are continuously evolving on multiple spatial and temporal scales, which can cause motion blur. Here, we present a Fast FPM method to achieve sub-second capture times for FPM results with 0.8 NA resolution across a 4x objective's FOV. We demonstrate the first FPM quantitative phase results for both growing and confluent in vitro cell cultures. Experiments capture real-time videos of HeLa and human mammary epithelial (MCF10A) cell division and migration and subcellular dynamical phenomena in adult rat neural stem cells.
Hypercomplex Fourier transforms of color images.
Ell, Todd A; Sangwine, Stephen J
2007-01-01
Fourier transforms are a fundamental tool in signal and image processing, yet, until recently, there was no definition of a Fourier transform applicable to color images in a holistic manner. In this paper, hypercomplex numbers, specifically quaternions, are used to define a Fourier transform applicable to color images. The properties of the transform are developed, and it is shown that the transform may be computed using two standard complex fast Fourier transforms. The resulting spectrum is explained in terms of familiar phase and modulus concepts, and a new concept of hypercomplex axis. A method for visualizing the spectrum using color graphics is also presented. Finally, a convolution operational formula in the spectral domain is discussed. PMID:17283762
Linear and nonlinear problems in Fourier imaging
NASA Astrophysics Data System (ADS)
Lawton, Wayne M.
1989-08-01
Conventional microwave and futuristic optical radar imaging requires estimating a function from limited Fourier information and a priori constraints. Linear problems include estimation from complex Fourier samples that are irregularly spaced on a polar grid (spotlight SAR), on a sinusoidal grid (laser SAR), or on a random grid (anti-aliasing phased array). Nonlinear problems include the famous phase retrieval problem of estimating a two-dimensional band limited function from its approximate Fourier modulus over a spatial region. Several deterministic and iterative methods for linear problems are described and their algorithmic complexity is discussed. A new method for attacking the infamous 'stagnation' problem that characterizes iterative methods for the phase retrieval problem is described. The method, which originated from consideration of spin-glass models of statistical lattice physics, incorporates partial information about the zero-set of the analytic continuation of the squared Fourier transform modulus in order to break the 'twin-object' symmetry responsible for stagnation.
Fourier phase microscopy with white light
Bhaduri, Basanta; Tangella, Krishnarao; Popescu, Gabriel
2013-01-01
Laser-based Fourier phase microscopy (FPM) works on the principle of decomposition of an image field in two spatial components that can be controllably shifted in phase with respect to each other. However, due to the coherent illumination, the contrast in phase images is degraded by speckles. In this paper we present FPM with spatially coherent white light (wFPM), which offers high spatial phase sensitivity due to the low temporal coherence and high temporal phase stability due to common path geometry. Further, by using a fast spatial light modulator (SLM) and a fast scientific-grade complementary metal oxide semiconductor (sCMOS) camera, we report imaging at a maximum rate of 12.5 quantitative phase frames per second with 5.5 mega pixels image size. We illustrate the utility of wFPM as a contrast enhancement as well as dynamic phase measurement method by imaging section of benign colonic glands and red blood cell membrane fluctuation. PMID:24010005
NASA Astrophysics Data System (ADS)
Liu, Zhengjun; Li, She; Liu, Wei; Wang, Yanhua; Liu, Shutian
2013-01-01
To enhance the security of double random phase encoding, a kind of amplitude scrambling operation is designed and introduced into an image encryption process. The random data of the second phase mask in double random phase encoding is also employed for scrambling amplitude distribution in order to save the space of storage and transmission of the key information. The scrambling operator is changeable for generating the key. Some numerical simulations have been provided for testing the validity of the image encryption scheme.
Medical image processing with optical Fourier techniques
Pengfei Wu
2003-01-01
Medical image processing is demonstrated by using Fourier techniques. Two optical Fourier systems are designed: the first one is a real-time optical processor with spatial filters and the second one is a self-adaptive optical processor with nonlinear optical films of the biomaterial Bacteriorhodopsin. Medical images including mammograms and Pap smears are investigated by using our optical systems. The desired components
Lensless imaging by spatial Fourier synthesis holography.
Arons, E; Dilworth, D
1996-02-10
The technique of Fourier synthesis holography is extended to the spatial domain. A spatially extended source is decomposed into its Fourier components, and a hologram of an object distribution is formed at each spatial frequency and stored in a computer. Upon synthesis in the computer a clear image can be formed of the object without the use of lenses. PMID:21069067
Proposal of snapshot line-imaging Fourier spectroscopy for smartphone
NASA Astrophysics Data System (ADS)
Kawashima, Natsumi; Sato, Shun; Ishida, Akane; Inohara, Daichi; Tanaka, Naotaka; Wada, Kenji; Nishiyama, Akira; Fujiwara, Masaru; Ishimaru, Ichiro
2015-03-01
We propose the extremely-compact-size line-imaging Fourier spectroscopy for smartphones. We realize the near common-path interferometer with strong robustness for mechanical vibrations by installing the transmission-type relative-inclined phase-shifter. The interferogram of an imaging line is formed as 2-dimensional fringe pattern on imaging sensor, such as CCD camera. In other words, the horizontal axis on an imaging sensor is assigned to phase-shift value. And the vertical axis is corresponds to image formation coordinate. Thus, by installing a relatively-inclined thin glass into imaging optics, such as smartphone, we will realize the line-imaging Fourier spectroscopy for healthcare sensor in daily-life environments.
Single-pixel imaging by means of Fourier spectrum acquisition
NASA Astrophysics Data System (ADS)
Zhang, Zibang; Ma, Xiao; Zhong, Jingang
2015-02-01
Single-pixel imaging techniques enable to capture a scene without a direct line of sight to the object, but high-quality imaging has been proven challenging especially in the presence of noisy environmental illumination. Here we present a single-pixel imaging technique that can achieve high-quality images by acquiring their Fourier spectrum. We use phase-shifting sinusoid structured illumination for the spectrum acquisition. Applying inverse Fourier transform to the obtained spectrum yields the desired image. The proposed technique is capable of capturing a scene without a direct view of it. Thus, it enables a feasible placement of detectors, only if the detectors can collect the light signals from the scene. The technique is also a compressive sampling like approach, so it can reconstruct an image from sub-Nyquist measurements. We experimentally obtain clear images by utilizing a detector not placed in direct view of the imaged scene even with noise introduced by environmental illuminations.
Single-pixel imaging by means of Fourier spectrum acquisition.
Zhang, Zibang; Ma, Xiao; Zhong, Jingang
2015-01-01
Single-pixel imaging techniques enable to capture a scene without a direct line of sight to the object, but high-quality imaging has been proven challenging especially in the presence of noisy environmental illumination. Here we present a single-pixel imaging technique that can achieve high-quality images by acquiring their Fourier spectrum. We use phase-shifting sinusoid structured illumination for the spectrum acquisition. Applying inverse Fourier transform to the obtained spectrum yields the desired image. The proposed technique is capable of capturing a scene without a direct view of it. Thus, it enables a feasible placement of detectors, only if the detectors can collect the light signals from the scene. The technique is also a compressive sampling like approach, so it can reconstruct an image from sub-Nyquist measurements. We experimentally obtain clear images by utilizing a detector not placed in direct view of the imaged scene even with noise introduced by environmental illuminations. PMID:25649009
Livermore Imaging Fourier Transform Infrared Spectrometer (LIFTIRS)
Carter, M.R.; Bennett, C.L.; Fields, D.J.; Lee, F.D.
1995-05-10
Lawrence Livermore National Laboratory is currently operating a hyperspectral imager, the Livermore Imaging Fourier Transform Infrared Spectrometer (LIFTIRS). This instrument is capable of operating throughout the infrared spectrum from 3 to 12.5 {mu}m with controllable spectral resolution. In this presentation we report on it`s operating characteristics, current capabilities, data throughput and calibration issues.
Imaging Fourier transform spectrometry of chemical plumes
Kenneth C. Bradley; Kevin C. Gross; Glen P. Perram
2009-01-01
A midwave infrared (MWIR) imaging Fourier transform spectrometer (FTS), the Telops FIRST-MWE (Field-portable Imaging Radiometric Spectrometer Technology - Midwave Extended) has been utilized for the standoff detection and characterization of chemical plumes. Successful collection and analysis of MWIR hyperspectral imagery of jet engine exhaust has allowed us to produce spatial profiles of both temperature and chemical constituent concentrations of exhaust
Fourier Transform and Reflective Imaging Pyrometry
Stevens, G. D.
2011-07-01
A stationary Fourier transform pyrometer was used to record mid-wavelength IR spectra in dynamic shock experiments. The gated-IR camera used with this system was also used to record images of light produced and light reflected from shocked metals in order to constrain the dynamic emissivity and provide temperature estimates. This technique will be referred to as reflective imaging pyrometry.
Coherent electromagnetic field imaging through Fourier transform heterodyne
Cooke, B.J.; Laubscher, B.E.; Olivas, N.L.; Goeller, R.M.; Cafferty, M.; Briles, S.D. [Los Alamos National Lab., NM (United States); Galbraith, A.E. [Los Alamos National Lab., NM (United States)]|[Univ. of Arizona, Tucson, AZ (United States). Electrical and Computer Engineering Dept.; Grubler, A.C. [Los Alamos National Lab., NM (United States)]|[Naval Academy, Annapolis, MD (United States)
1998-12-31
The authors present a detection process capable of directly imaging the transverse amplitude, phase, and if desired, Doppler shift of coherent electromagnetic fields. Based on coherent detection principles governing conventional heterodyned RADAR/LIDAR systems, Fourier Transform Heterodyne (FTH) incorporates transverse spatial encoding of the local oscillator for image capture. Appropriate selection of spatial encoding functions, or basis set, allows image retrieval by way of classic Fourier manipulations. Of practical interest: (1) imaging is accomplished on a single element detector requiring no additional scanning or moving components, and (2) a wide variety of appropriate spatial encoding functions exist that may be adaptively configured in real-time for applications requiring optimal detection. In this paper, they introduce the underlying principles governing FTH imaging, followed by demonstration of concept via a simple experimental setup based on a HeNe laser and a 69 element spatial phase modulator.
Fourier analysis of blood plasma laser images phase maps in the diagnosis of cancer in human organs
NASA Astrophysics Data System (ADS)
Angelsky, P. O.; Kushnerick, L. Ya.; Bachinskiy, V. T.; Vanchuliak, O. Ya.; Garazdiuk, M.; Pashkovska, N. V.; Andriychuk, D.
2013-12-01
A method of polarization mapping of the optico-anisotropic polycrystalline networks of the blood plasma albumin and globulin proteins with adjusted spatial-frequency filtering of the coordinate distributions of the azimuth and ellipticity of the polarization of laser radiation in the Fourier plane is proposed and substantiated. Comparative studies of the effectiveness of direct methods of mapping and a spatial-frequency selection in differentiating polarization azimuth and ellipticity maps of the field of laser radiation converted by the networks of albumin - globulin crystals of the blood plasma in healthy people and patients with prostate cancer have been carried out.
Novel fringe scanning/Fourier transform method of synthetic imaging
Crawford, T.M.; Albano, R.K.
1993-08-01
We have developed a one-dimensional theory and a computer model for synthetically imaging scenes using a novel fringe scanning/Fourier transform technique. Our method probes a scene using two interfering beams of slightly different frequency. These beams form a moving fringe pattern which scans the scene and resonates with any spatial frequency components having the same spatial frequency as the scanning fringe pattern. A simple, non-imaging detector above the scene observes any scattered radiation from the scene falling onto it. If a resonance occurs between the scanning fringe pattern and the scene, then the scattered radiation will be modulated at the difference frequency between the two probing beams. By changing the spatial period of the fringe pattern and then measuring the amplitude and phase of the modulated radiation that is scattered from the scene, the Fourier amplitudes and phases of the different spatial frequency components making up the scene can be measured. A synthetic image of the scene being probed can be generated from this Fourier amplitude and phase data by taking the inverse Fourier transform of this information. This technique could be used to image objects using light, ultrasonic, or other electromagnetic or acoustic waves.
ALMA : Fourier phase analysis made possible
F. Levrier; E. Falgarone; F. Viallefond
2007-04-18
Fourier phases contain a vast amount of information about structure in direct space, that most statistical tools never tap into. We address ALMA's ability to detect and recover this information, using the probability distribution function (PDF) of phase increments, and the related concepts of phase entropy and phase structure quantity. We show that ALMA, with its high dynamical range, is definitely needed to achieve significant detection of phase structure, and that it will do so even in the presence of a fair amount of atmospheric phase noise. We also show that ALMA should be able to recover the actual "amount" of phase structure in the noise-free case, if multiple configurations are used.
Multiple imaging by lensless Fourier transform holography
P. C. Mehta; C. Bhan; R. Hradaynath
1979-01-01
A simple method for producing multiple images is reported by recording a lensless Fourier transform hologram of the master object using a holographic grating. Relations for optimizing reference-to-object beam intensity ratio are derived in order to retain linearity and efficiency of the hologram. One of the advantages of the technique is that the same grating can be used for the
Color Image Watermarking Using Multidimensional Fourier Transforms
Tsz Kin Tsui; Xiao-ping Zhang; Dimitrios Androutsos
2008-01-01
Abstract—This paper presents two vector watermarking schemes that are based on the use of complex and quaternion Fourier transforms and demonstrates, for the first time, how to embed watermarks into the frequency domain that is consistent with our human visual system. Watermark casting is performed by estimating the just-noticeable distortion of the images, to ensure watermark invisibility. The first method
Fourier phase analysis in radio-interferometry
Francois Levrier; Edith Falgarone; Francois Viallefond
2006-06-09
Most statistical tools used to characterize the complex structures of the interstellar medium can be related to the power spectrum, and therefore to the Fourier amplitudes of the observed fields. To tap into the vast amount of information contained in the Fourier phases, one may consider the probability distribution function (PDF) of phase increments, and the related concepts of phase entropy and phase structure quantity. We use these ideas here with the purpose of assessing the ability of radio-interferometers to detect and recover this information. By comparing current arrays such as the VLA and Plateau de Bure to the future ALMA instrument, we show that the latter is definitely needed to achieve significant detection of phase structure, and that it will do so even in the presence of a fair amount of atmospheric phase fluctuations. We also show that ALMA will be able to recover the actual "amount'' of phase structure in the noise-free case, if multiple configurations are used.
Fourier Phase Analysis of SDSS Galaxies
Chiaki Hikage; Takahiko Matsubara; Yasushi Suto; Changbom Park; Alexander S. Szalay; Jon Brinkmann
2005-09-13
We present a first analysis of the clustering of SDSS galaxies using the distribution function of the sum of Fourier phases. This statistic was recently proposed by one of authors as a new method to probe phase correlations of cosmological density fields. Since the Fourier phases are statistically independent of Fourier amplitudes, the phase statistic plays a complementary role to the conventional two-point statistics of galaxy clustering. In particular, we focus on the distribution functions of phase sum over three closed wavevectors as a function of the configurations of triangle wavevectors. We find that the observed distribution functions of phase sum are in good agreement with the lowest-order approximation from perturbation theory. For direct comparison with observations, we construct mock catalogs from N-body simulations taking account of several observational effects such as the survey geometry, the redshift distortion, and the discreteness due to the limited number of data. Indeed the observed phase correlations for the galaxies in the range of absolute magnitude -22
Metaphase Selection By Analysis Of The Fourier Transformed Image
NASA Astrophysics Data System (ADS)
Hutzler, P.; Stettmaier, K.; Brettel, H.
1982-11-01
Automatic metaphase finding may be done by analysing the images of the chromosomes in the image plane or by investigation of their Fourier spectrum. We found that both digital Fourier transformation and optical Fourier processing of these objects give results which are in good agreement.
Fourier transform digital holographic adaptive optics imaging system
Liu, Changgeng; Yu, Xiao; Kim, Myung K.
2013-01-01
A Fourier transform digital holographic adaptive optics imaging system and its basic principles are proposed. The CCD is put at the exact Fourier transform plane of the pupil of the eye lens. The spherical curvature introduced by the optics except the eye lens itself is eliminated. The CCD is also at image plane of the target. The point-spread function of the system is directly recorded, making it easier to determine the correct guide-star hologram. Also, the light signal will be stronger at the CCD, especially for phase-aberration sensing. Numerical propagation is avoided. The sensor aperture has nothing to do with the resolution and the possibility of using low coherence or incoherent illumination is opened. The system becomes more efficient and flexible. Although it is intended for ophthalmic use, it also shows potential application in microscopy. The robustness and feasibility of this compact system are demonstrated by simulations and experiments using scattering objects. PMID:23262541
Quantitative phase microscopy through differential interference imaging
Sharon V. King; Ariel Libertun; Rafael Piestun; Carol J. Cogswell; Chrysanthe Preza
2008-01-01
An extension of Nomarski differential interference contrast microscopy enables isotropic linear phase imaging through the combination of phase shifting, two directions of shear and Fourier-space integration using a modified spiral phase transform. We apply this method to simulated and experimentally acquired images of partially absorptive test objects. A direct comparison of the computationally determined phase to the true object phase
WARP: accurate retrieval of shapes using phase of fourier descriptors and time warping distance.
Bartolini, Ilaria; Ciaccia, Paolo; Patella, Marco
2005-01-01
Effective and efficient retrieval of similar shapes from large image databases is still a challenging problem in spite of the high relevance that shape information can have in describing image contents. In this paper, we propose a novel Fourier-based approach, called WARP, for matching and retrieving similar shapes. The unique characteristics of WARP are the exploitation of the phase of Fourier coefficients and the use of the Dynamic Time Warping (DTW) distance to compare shape descriptors. While phase information provides a more accurate description of object boundaries than using only the amplitude of Fourier coefficients, the DTW distance permits us to accurately match images even in the presence of (limited) phase shiftings. In terms of classical precision/recall measures, we experimentally demonstrate that WARP can gain, say, up to 35 percent in precision at a 20 percent recall level with respect to Fourier-based techniques that use neither phase nor DTW distance. PMID:15628276
Effects of Data Density of Echo Fourier Domain on Quality of High Frame Rate Imaging
Lu, Jian-yu
]-[20]. Motion artifacts and phase aberration effects on the HFR imaging have been studied [21) at a high frame rate while dramatically reducing the amount of computations due to the use of Fast Fourier
Phase retrieval with Fourier-weighted projections Manuel Guizar-Sicairos and James R. Fienup*
Fienup, James R.
- pler than other lensless imaging techniques, such as digi- tal holography. It does not require a retroPhase retrieval with Fourier-weighted projections Manuel Guizar-Sicairos and James R. Fienup February 14, 2008 In coherent lensless imaging, the presence of image sidelobes, which arise as a natural
Target Image Enhancement in Radar Imaging Using Fractional Fourier Transform
NASA Astrophysics Data System (ADS)
El-Mashed, M. G.; Dessouky, M. I.; El-Kordy, M.; Zahran, O.; Abd El-Samie, F. E.
2012-03-01
This paper presents a new Range-Doppler Algorithm based on Fractional Fourier Transform (RDA-FrFT) to obtain High-Resolution (HR) images for targets in radar imaging. The performance of the proposed RDA-FrFT is compared with the classical RDA algorithm, which is based on the Fast Fourier Transform (FFT). A closed-form expression for the range and azimuth compression of the proposed RDA-FrFT is mathematically derived and analyzed from the HR Synthetic Aperture Radar (SAR) imaging point of view. The proposed RDA-FrFT takes its advantage of the property of the FrFT to resolve chirp signals with high precision. Results show that the proposed RDA-FrFT gives low Peak Side-Lobe (PSL) and Integrated Side-Lobe (ISL) levels in range and azimuth directions for detected targets. HR images are obtained using the proposed RDA-FrFT algorithm.
Wei Wan; Ruisheng Liang; Zhilie Tang; Zhanxu Chen; Hanchao Zhang; Yongheng He
2007-01-01
The theory of photoacoustic tomography imaging using an acoustic lens imaging system has been investigated, and the photoacoustic (PA) Fourier imaging property of an acoustic lens is presented. The theoretical results show that an acoustic lens is able to realize two-dimensional PA Fourier imaging and the focal depth of the acoustic lens is 20 mm. The PA signals with the
Sun, Zhiwei; Hou, Peipei; Zhi, Ya'nan; Sun, Jianfeng; Zhou, Yu; Xu, Qian; Lu, Zhiyong; Liu, Liren
2014-03-20
A two-dimensional (2D) Fourier transform algorithm for the image reconstruction of synthetic-aperture imaging ladar (SAIL) collected data is suggested. This algorithm consists of quadratic phase compensation in azimuth direction and 2D fast Fourier transform. Based on this algorithm and the parallel 2D Fourier transform capability of spherical lens, an optical principle scheme that processes the SAIL data is proposed. The basic principle, design equations, and necessary analysis are presented. To verify this principle scheme, an experimental optical SAIL processor setup is constructed. The imaging results of SAIL data obtained by our SAIL demonstrator are presented. The optical processor is compact, lightweight, and consumes low power. This optical processor can also provide inherent parallel and speed-of-light computing capability, and thus has potential applications in on-board and satellite-borne SAIL systems. PMID:24663462
Numerical compensation in phase-shifting in-line lensless Fourier digital holographic microscopy
Caojin Yuan; Liyun Zhong; Xiaoxu Lv; Yue Zhu
2005-01-01
A numerical compensation technique is proposed to enhance the quality of reconstruction of phase-shifting lensless Fourier digital holographic microscopy. Introducing phase-shifting technique into the in-line lensless Fourier digital holographic microscopy is widely used, because this system possesses high resolution and is able to suppress the zero-order of diffraction and the twin image in reconstruction. Practically, it is likely to suffer
Phase averaging of image ensembles by using cepstral gradients
Herbert W. Swan
1983-01-01
The direct Fourier phase averaging of an ensemble of randomly blurred images has long been thought to be too difficult a problem to undertake realistically owing to the necessity of proper phase unwrapping. It is shown that it is nevertheless possible to average the Fourier phase information in an image ensemble without calculating phases by using the technique of cepstral
Algorithms for Bayesian background-subtracted Fourier darkfield imaging.
Fraundorf, P; Pollack, K
1991-08-01
Formal consideration of prior information on the Fourier amplitude of background contrast in an image, using the same Bayesian principles of statistical inference which underlie thermodynamics, allows one to subtract background without favoring only selected parts of frequency space. Without the bias in frequency space which causes periodicity bleeding and mars literal interpretation of Fourier-filtered images, the shape transform of aperiodic objects can be left intact. Algorithms for Bayesian background subtraction from one- and two-dimensional images are presented which further consider, in ad hoc fashion, one's uncertainty about background amplitude. The results help explain the reported success of Fourier truncation, and indicate that Bayesian background-subtracted images can minimize root-mean-square image error, as well as periodicity bleeding, in comparison to Fourier-filtered and Fourier-truncated alternatives. PMID:1750150
Imaging Fourier transform spectrometry of chemical plumes
NASA Astrophysics Data System (ADS)
Bradley, Kenneth C.; Gross, Kevin C.; Perram, Glen P.
2009-05-01
A midwave infrared (MWIR) imaging Fourier transform spectrometer (FTS), the Telops FIRST-MWE (Field-portable Imaging Radiometric Spectrometer Technology - Midwave Extended) has been utilized for the standoff detection and characterization of chemical plumes. Successful collection and analysis of MWIR hyperspectral imagery of jet engine exhaust has allowed us to produce spatial profiles of both temperature and chemical constituent concentrations of exhaust plumes. Successful characterization of this high temperature combustion event has led to the collection and analysis of hyperspectral imagery of lower temperature emissions from industrial smokestacks. This paper presents MWIR data from remote collection of hyperspectral imagery of methyl salicilate (MeS), a chemical warfare agent simulant, during the Chemical Biological Distributed Early Warning System (CBDEWS) test at Dugway Proving Grounds, UT in 2008. The data did not contain spectral lines associated with emission of MeS. However, a few broad spectral features were present in the background-subtracted plume spectra. Further analysis will be required to assign these features, and determine the utility of MWIR hyperspectral imagery for analysis of chemical warfare agent plumes.
Operation of a deformable mirror device as a Fourier plane phase modulating filter
NASA Technical Reports Server (NTRS)
Florence, James M.; Giles, Michael K.; Smith, Jeffery Z.
1988-01-01
The operation of a deformable mirror device (DMD) as a Fourier plane phase modulating filter is described. An analysis of the optical characteristics of the DMD elements as phase modulators is summarized. Analytical and experimental results indicating the existence of a quasi-phase-only operational mode are presented. These results are used to specify the mirror deflection required to implement a binary phase-only image correlation operation. An optical correlator system is implemented using the DMD Fourier plane filter and experimental results from this system are compared with computer simulations of the correlator operation.
Reconstruction of images of deep-space objects using Fourier telescopy
Richard B. Holmes; Timothy J. Brinkley
1999-01-01
Fourier Telescopy is an imaging method that can form images of very dim objects with angular resolution of a few nanoradians, attained by means of a synthetic aperture that overcomes the effects of intervening aberrations using mathematical algorithms akin to that of long-baseline radio astronomy. The algorithm makes use of phase closure and advanced wavefront reconstruction techniques from adaptive optics
Fractional Fourier-domain random encoding and pixel scrambling technique for double image encryption
NASA Astrophysics Data System (ADS)
Zhong, Zhi; Chang, Jie; Shan, Mingguang; Hao, Bengong
2012-01-01
A double image encryption method is proposed using fractional Fourier-domain random encoding and pixel scrambling technique. One of the two original images is encoded into the phase function of a synthesized input signal after being scrambled, and the other original image encoded into its amplitude. The phase function serves as phase mask in the input domain, and the synthesized input signal is then encrypted into stationary white noise by utilizing random phase encoding in fractional Fourier domain. The two original images can be retrieved without cross-talk by using the correct keys with fractional orders, the random phase mask and the pixel scrambling operator. Numerical simulations and security analysis have been done to prove the validity and the security of the proposed encryption method.
Direct image reconstruction from a Fourier intensity pattern using HERALDO
Fienup, James R.
in the development of coherent lensless imaging tech- niques. Holography with extended reference by auto- correlationDirect image reconstruction from a Fourier intensity pattern using HERALDO Manuel Guizar believe to be the first experimental demonstration of a novel coherent lensless imaging technique
Radial Hilbert Transform in terms of the Fourier Transform applied to Image Encryption
NASA Astrophysics Data System (ADS)
Morales, Y.; Díaz, L.; Torres, C.
2015-01-01
In the present investigation, a mathematical algorithm under Matlab platform using Radial Hilbert Transform and Random Phase Mask for encrypting digital images is implemented. The algorithm is based on the use of the conventional Fourier transform and two random phase masks, which provide security and robustness to the system implemented. Random phase masks used during encryption and decryption are the keys to improve security and make the system immune to attacks by program generation phase masks.
Exponential sums as discrete Fourier with invariant phase functions
Provence Aix-Marseille I, UniversitÃ© de
discuss the link between exponential sums and bent functions. 1 Introduction Exponential sums play the results on quadratic phases, and in section 9 we connect exponential sums to the theory of bent functionsExponential sums as discrete Fourier transform with invariant phase functions Gilles Lachaud
Dynamic phase measurement in shearography by clustering method and Fourier filtering.
Huang, Yuanhao; Janabi-Sharifi, Farrokh; Liu, Yusheng; Hung, Y Y
2011-01-17
Quantitative phase extraction is a key step in optical measurement. While phase shifting technique is widely employed for static or semi-static phase measurement, it requires several images with known phase shifts at each deformed stage, thus is not suitable for dynamic phase measurement. Fourier transform offer a solution to extract phase information from a single fringe pattern. However, a high frequency spatial carrier which is sometimes not easy to generate is required to solve the phase ambiguity problem. In this paper, we aim to propose an ideal solution for dynamic phase measurement. Four images with known phase shift are captured at the reference stage to analyze the initial phase information. After the object starts continuous deformation, only one image is captured at each deformed stage. A clustering phase extraction method is then applied for deformation phase extraction utilizing the phase clustering effect within a small region. This method works well for speckle image with low and medium fringe density. When the fringe density is high, especially in the case of shearographic fringe, information insufficiency inherent with merely one deformed speckle image often results in poor quality wrapped phase map with plenty of phase residues, which make phase unwrapping a difficult task. In the light of this limitation, a Fourier transform based phase filtering method is proposed for fringe frequency analysis and adaptive filtering, and effectively removes most of the phase residues to reconstruct a high quality wrapped phase map. Several real experiments based on shearography are presented. Comparison between the proposed solution and standard phase evaluation methods is also given. The results demonstrate the effectiveness of the proposed integrated dynamic phase extraction method. PMID:21263600
Asymmetric multiple-image encryption based on the cascaded fractional Fourier transform
NASA Astrophysics Data System (ADS)
Li, Yanbin; Zhang, Feng; Li, Yuanchao; Tao, Ran
2015-09-01
A multiple-image cryptosystem is proposed based on the cascaded fractional Fourier transform. During an encryption procedure, each of the original images is directly separated into two phase masks. A portion of the masks is subsequently modulated into an interim mask, which is encrypted into the ciphertext image; the others are used as the encryption keys. Using phase truncation in the fractional Fourier domain, one can use an asymmetric cryptosystem to produce a real-valued noise-like ciphertext, while a legal user can reconstruct all of the original images using a different group of phase masks. The encryption key is an indivisible part of the corresponding original image and is still useful during decryption. The proposed system has high resistance to various potential attacks, including the chosen-plaintext attack. Numerical simulations also demonstrate the security and feasibility of the proposed scheme.
Invariant quaternion radial harmonic Fourier moments for color image retrieval
NASA Astrophysics Data System (ADS)
Xiang-yang, Wang; Wei-yi, Li; Hong-ying, Yang; Pan-pan, Niu; Yong-wei, Li
2015-03-01
Moments and moment invariants have become a powerful tool in image processing owing to their image description capability and invariance property. But, conventional methods are mainly introduced to deal with the binary or gray-scale images, and the only approaches for color image always have poor color image description capability. Based on radial harmonic Fourier moments (RHFMs) and quaternion, we introduced the quaternion radial harmonic Fourier moments (QRHFMs) for representing color images in this paper, which can be seen as the generalization of RHFMs for gray-level images. It is shown that the QRHFMs can be obtained from the RHFMs of each color channel. We derived and analyzed the rotation, scaling, and translation (RST) invariant property of QRHFMs. We also discussed the problem of color image retrieval using invariant QRHFMs. Experimental results are provided to illustrate the efficiency of the proposed color image representation.
Compression imaging based on Fourier transform optical system
NASA Astrophysics Data System (ADS)
Lv, Jinfeng; Zhao, Huaici; Zhao, Chunyang
2014-11-01
Shannon / Nyquist sampling theorem indicates that during the sampling process the minimum sample rate must be more than the double of the band of the signal so that we can achieve images without distortion. High-frequency sampling leads to mass data and results in high cost of storage and transmission procedure. Compressed sensing indicates that we can sample data at far below the Nyquist frequency when the signals are sparse or can be represented as sparse on some orthogonal basis, and the signals can be recovered without distortion after some certain recovery algorithms. By this means the cost of storage and transmission can be reduced significantly. Unlike conventional optical imaging process, this paper presents a new imaging method using a Fourier transform lens system, which enables single-exposure and single-aperture compressed imaging. First, the Fourier transformation of image signals is accomplished after they pass through a Fourier transform optical system. Second, sparse sample data can be obtained after the spectrum signals pass the sensor array. The process mentioned above can be interpreted as that using a Fourier matrix and a sparse matrix to complete the measurement of the image signals. Third, we make use of fast iterative threshold recovery algorithm to compute the sampling values and obtain the target image signals. Compared with the conventional imaging methods, in the case of ensuring the image quality, our method can significantly reduce the number of samples, thus greatly reduce the data redundancy. Simulation results indicate that the imaging method proposed can be prospective.
Comparative analysis of imaging configurations and objectives for Fourier microscopy
Kurvits, Jonathan A; Zia, Rashid
2015-01-01
Fourier microscopy is becoming an increasingly important tool for the analysis of optical nanostructures and quantum emitters. However, achieving quantitative Fourier space measurements requires a thorough understanding of the impact of aberrations introduced by optical microscopes, which have been optimized for conventional real-space imaging. Here, we present a detailed framework for analyzing the performance of microscope objectives for several common Fourier imaging configurations. To this end, we model objectives from Nikon, Olympus, and Zeiss using parameters that were inferred from patent literature and confirmed, where possible, by physical disassembly. We then examine the aberrations most relevant to Fourier microscopy, including the alignment tolerances of apodization factors for different objective classes, the effect of magnification on the modulation transfer function, and vignetting-induced reductions of the effective numerical aperture for wide-field measurements. Based on this analysis, we ide...
Optical color image hiding scheme by using Gerchberg-Saxton algorithm in fractional Fourier domain
NASA Astrophysics Data System (ADS)
Chen, Hang; Du, Xiaoping; Liu, Zhengjun; Yang, Chengwei
2015-03-01
We proposed an optical color image hiding algorithm based on Gerchberg-Saxton retrieval algorithm in fractional Fourier domain. The RGB components of the color image are converted into a scrambled image by using 3D Arnold transform before the hiding operation simultaneously and these changed images are regarded as the amplitude of fractional Fourier spectrum. Subsequently the unknown phase functions in fractional Fourier domain are calculated by the retrieval algorithm, in which the host RBG components are the part of amplitude of the input functions. The 3D Arnold transform is performed with different parameters to enhance the security of the hiding and extracting algorithm. Some numerical simulations are made to test the validity and capability of the proposed color hiding encryption algorithm.
NASA Astrophysics Data System (ADS)
Chen, Yan; Wang, Xiangzhao; Li, Zhongliang; Nan, Nan; Guo, Xin
2014-09-01
We present a full-range Fourier domain polarization-sensitive optical coherence tomography technique which is able to obtain images of retardance, fast optical axis and intensity of sample. In this technique, the sinusoidal phase modulation is introduced into the spectral interferograms while the probe beam scans over the sample (B-scan). Then the complex horizontal and vertical signals are reconstructed by demodulation. By the Fourier transformation of the two interferograms, the full range images are obtained. Herein, the typical linear phase modulation is modified to sinusoidal phase modulation, which improves the system tolerance of sample movements and avoids sensitivity fall-off along the transverse scan. Furthermore, the images are obtained through the recombination of the horizontal and vertical polarization beam components acquired by a single camera, which avoids the problems of synchronous control and alignments in the situation of two cameras.
Shi, Xiaoyan; Zhao, Daomu
2011-02-10
Based on joint transform correlator (JTC) architecture and holographic techniques, a new method for image hiding is presented. A hidden image encrypted by JTC architecture is embedded in the Fourier hologram of the host image. Inverse Fourier transform can be used to obtain the watermarked image, and JTC architecture is used to decode the hidden image from the watermarked hologram. Unlike other watermarking techniques, by prechoosing information, the noise added to the recovered hidden image by the host can be reduced. Unlike other watermarking systems based on double random-phase encoding, no conjugate key is used to recover the hidden image. Theoretical analyses have shown the system's feasibility. Computer simulations are presented to verify the system's validity and efficiency. Numerical simulations also show that the proposed system is robust enough to resist attacks, such as occlusion, noise, and filtering. PMID:21343999
Improving imaging resolution of shaking targets by Fourier-transform ghost diffraction
Cong Zhang; Wenlin Gong; Shensheng Han
2012-07-26
For conventional imaging, shaking of the imaging system or the target leads to the degradation of imaging resolution. In this work, the influence of the target's shaking to fourier-transform ghost diffraction (FGD) is investigated. The analytical results, which are backed up by numerical simulation and experiments, demonstrate that the quiver of target has no effect on the resolution of FGD, thus the target's imaging with high spatial resolution can be always achieved by phase-retrieval method from the FGD patterns. This approach can be applied in high-precision imaging systems, to overcome the influence of the system's shaking to imaging resolution.
[Research on spatially modulated Fourier transform imaging spectrometer data processing method].
Huang, Min; Xiangli, Bin; Lü, Qun-Bo; Zhou, Jin-Song; Jing, Juan-Juan; Cui, Yan
2010-03-01
Fourier transform imaging spectrometer is a new technic, and has been developed very rapidly in nearly ten years. The data catched by Fourier transform imaging spectrometer is indirect data, can not be used by user, and need to be processed by various approaches, including data pretreatment, apodization, phase correction, FFT, and spectral radicalization calibration. No paper so far has been found roundly to introduce this method. In the present paper, the author will give an effective method to process the interfering data to spectral data, and with this method we can obtain good result. PMID:20496726
A comparative image analysis of discrete radial Fourier transforms
Guojun Zhang; Bo Li; Bo Fu; Li Li; Gaoxiang Liu
2010-01-01
Fourier transform is not often applied to pattern and object recognition, because of its inefficiency in image description and calculation. In order to solve this problem, a bi-discrete radial cosine transform is proposed. This new transform has two superior properties. Firstly, by using Mukundan’s square-to-circular transformation, it projects images in square to images in discrete circle girds. Secondly, different from
Phase unwrapping for 2-D blind deconvolution of ultrasound images
Oleg V. Michailovich; Dan Adam
2004-01-01
In most approaches to the problem of two-dimensional homomorphic deconvolution of ultrasound images, the estimation of a corresponding point-spread function (PSF) is necessarily the first stage in the process of image restoration. This estimation is usually performed in the Fourier domain by either successive or simultaneous estimation of the amplitude and phase of the Fourier transform (FT) of the PSF.
Nonuniqueness of phase retrieval for three fractional Fourier transforms
Claudio Carmeli; Teiko Heinosaari; Jussi Schultz; Alessandro Toigo
2014-11-25
We prove that, regardless of the choice of the angles $\\theta_1,\\theta_2,\\theta_3$, three fractional Fourier transforms $F_{\\theta_1}$, $F_{\\theta_2}$ and $F_{\\theta_3}$ do not solve the phase retrieval problem. That is, there do not exist three angles $\\theta_1$, $\\theta_2$, $\\theta_3$ such that any signal $\\psi\\in L^2(R)$ could be determined up to a constant phase by knowing only the three intensities $|F_{\\theta_1}\\psi|^2$, $|F_{\\theta_2}\\psi|^2$ and $|F_{\\theta_3}\\psi|^2$. This provides a negative argument against a recent speculation by P. Jaming, who stated that three suitably chosen fractional Fourier transforms are good candidates for phase retrieval in infinite dimension. We recast the question in the language of quantum mechanics, where our result shows that any fixed triple of rotated quadrature observables $Q_{\\theta_1}$, $Q_{\\theta_2}$ and $Q_{\\theta_3}$ is not enough to determine all unknown pure quantum states. The sufficiency of four rotated quadrature observables, or equivalently fractional Fourier transforms, remains an open question.
Near-infrared Fourier transform imaging spectrometer for remote sensing
NASA Astrophysics Data System (ADS)
Li, Jianxin; Meng, Xin; Xu, Donglei; Song, Huaqing; Wang, Liu; Zhu, Rihong
2014-11-01
Fourier transform spectrometer without input slit is an emerging technology for spectral imaging. It has the advantages of high spatial resolution and high radiation throughput compared to the similar device with input slit. A near-infrared (NIR) Fourier transform spectrometer using Sagnac interferometer is presented and discussed in this paper. This system is composed of a Sagnac interferometer used as a lateral shearing splitter, an objective and a NIR camera. The principle of the system is presented including the discuss of its main characteristics and the optical layout of the Sagnac interferometer. Then the main technical features are discussed, such as the sample of the optical path difference (OPD). A experimental device is set up and presented that is used for two proven experiments. Some spectral images are reconstructed from 1050nm to 1720nm and proves the feasibility of the proposed system for NIR spectral imaging.
Optimal color image restoration: Wiener filter and quaternion Fourier transform
NASA Astrophysics Data System (ADS)
Grigoryan, Artyom M.; Agaian, Sos S.
2015-03-01
In this paper, we consider the model of quaternion signal degradation when the signal is convoluted and an additive noise is added. The classical model of such a model leads to the solution of the optimal Wiener filter, where the optimality with respect to the mean square error. The characteristic of this filter can be found in the frequency domain by using the Fourier transform. For quaternion signals, the inverse problem is complicated by the fact that the quaternion arithmetic is not commutative. The quaternion Fourier transform does not map the convolution to the operation of multiplication. In this paper, we analyze the linear model of the signal and image degradation with an additive independent noise and the optimal filtration of the signal and images in the frequency domain and in the quaternion space.
High-resolution lensless Fourier transform holography for microstructure imaging
Jie Zhao; Dayong Wang; Huaying Wang; Jianjun Xie
2007-01-01
Digital holography combines the advantages of the optical holography and the computers. It can implement an all-digital processing and has the quasi real-time property. With lensless Fourier transform recording architecture, the limited bandwidth of CCD camera can be utilized sufficiently, and the sampling theorem is satisfied easily. Therefore, high-resolution can be achieved. So it is preferred in the microstructure imaging.
Simple and Robust Digital Holography Used for Phase Imaging
Jingbo Liu; Xiufa Song; Min Huang; Huaying Wang
2008-01-01
Digital holography is a digitized holography, which is very suitable for phase imaging of microscopic object. An off-axis lensless Fourier transform digital holographic system is built. The recording and numerical reconstruction of digital hologram is analyzed. The model of phase aberration in numerical reconstruction is presented. Experimental investigations have been performed for a USAF test target. The accurate phase image
Mesh adaptation technique for Fourier-domain fluorescence lifetime imaging
Soloviev, Vadim Y. [Department of Computer Science, University College London, Gower Street, London WC1E 6BT (United Kingdom)
2006-11-15
A novel adaptive mesh technique in the Fourier domain is introduced for problems in fluorescence lifetime imaging. A dynamical adaptation of the three-dimensional scheme based on the finite volume formulation reduces computational time and balances the ill-posed nature of the inverse problem. Light propagation in the medium is modeled by the telegraph equation, while the lifetime reconstruction algorithm is derived from the Fredholm integral equation of the first kind. Stability and computational efficiency of the method are demonstrated by image reconstruction of two spherical fluorescent objects embedded in a tissue phantom.
In vivo blood flow imaging by a swept laser source based Fourier domain optical Doppler tomography
NASA Astrophysics Data System (ADS)
Zhang, Jun; Chen, Zhongping
2005-09-01
A swept source based Fourier domain optical Doppler tomography (FDODT) system was developed. The technique is based on a phase-resolved method where phase information was retrieved from the reconstructed complex fringe signals. The aliasing effects and artifacts caused by lateral scanning and sample movement were removed with a signal processing technique. The standard deviation of the phase shift of the system was reduced from 49 to 1.8 degrees with the signal processing method employed. Structural, Doppler and Doppler variance images of fluid flow through glass channels were quantified, and blood flow through vessels of chick chorioallantoic membrane (CAM) was demonstrated in vivo
NASA Astrophysics Data System (ADS)
Zhang, B.; Sang, Jun; Alam, Mohammad S.
2013-03-01
An image hiding method based on cascaded iterative Fourier transform and public-key encryption algorithm was proposed. Firstly, the original secret image was encrypted into two phase-only masks M1 and M2 via cascaded iterative Fourier transform (CIFT) algorithm. Then, the public-key encryption algorithm RSA was adopted to encrypt M2 into M2' . Finally, a host image was enlarged by extending one pixel into 2×2 pixels and each element in M1 and M2' was multiplied with a superimposition coefficient and added to or subtracted from two different elements in the 2×2 pixels of the enlarged host image. To recover the secret image from the stego-image, the two masks were extracted from the stego-image without the original host image. By applying public-key encryption algorithm, the key distribution was facilitated, and also compared with the image hiding method based on optical interference, the proposed method may reach higher robustness by employing the characteristics of the CIFT algorithm. Computer simulations show that this method has good robustness against image processing.
Fourier-processed images of dynamic lung function from list-mode data
Zubal, I.G.; Rowe, R.W.; Bizais, Y.; Susskind, H.; Bennett, G.W.; Brill, A.B.
1983-01-01
Time and volume correlated amplitude and phase images are computed from nuclear medical ventilation studies and for dynamic transmission scans of the lungs. This is made possible by a hardware interface and data acquisition system, developed in-house, allowing camera events and multiple ancillary physiological signals (including lung volume) to be acquired simultaneously in list mode. The first harmonic amplitude and phase images are constructed on an event by event basis. These are computed for both equal time and equal lung volume increments. Time and volume correlated Fourier images for ventilation studies have shown details and functional structures not usually seen in conventional imaging techniques. Processed transmission scans show similar results compared to ventilation images.
hal-00258693,version1-24Feb2008 Wide-field Fourier transform spectral imaging
source in the object plane. This configuration constitutes a lensless Fourier holographic setup [9hal-00258693,version1-24Feb2008 Wide-field Fourier transform spectral imaging Michael Atlan). A numerical Fourier transform of the time-domain recording enables wide-field coherent spectral imaging
Imaging the sun in hard x rays using Fourier telescopes
NASA Technical Reports Server (NTRS)
Campbell, J. W.
1993-01-01
For several years, solar flares have been observed with a variety of instruments confirming that tremendous amounts of energy are locally stored in the solar magnetic field and then rapidly released during the life of the flare. In concert with observations, theorists have attempted to describe the means by which these energetic events occur and evolve. Two competing theories have emerged and have stood the test of time. One theory describes the flare in terms of nonthermal, electron beam injection into a thick target while the other uses a thermal approach. Both theories provide results which are reasonably consistent with current observations; but to date, none have been able to provide conclusive evidence as to the validity of either model. Imaging on short time scales (1 s) and/or small size scales (1 arc s) should give definitive answers to these questions. In order to test whether a realistic telescope can indeed discriminate between models, we construct model sources based upon the thermal and the nonthermal models and calculate the emission as a function of time and energy in the range from 10 to 100 keV. In addition, we construct model telescopes representing both the spatial modulation collimator (SMC) and the rotating modulation collimator (RMC) techniques of observation using random photon counting statistics. With these two types of telescopes we numerically simulate the instrument response to the above two model flares to see if there are distinct x-ray signatures which may be discernable. We find that theoretical descriptions of the primary models of solar flares do indeed predict different hard x-ray signatures for 1 sec time scales and at 1-5 arc sec spatial resolution. However, these distinguishing signatures can best be observed early in the impulsive phase and from a position perpendicular to the plane of the loop. Furthermore, we find that Fourier telescopes with reasonable and currently attainable design characteristics can image these signatures and that the same sensitive areas and short temporal integration times relative to source evolution (i.e., 1 s), the RMC and the SMC will both provide about the same performance.
NASA Astrophysics Data System (ADS)
Tokii, Maki; Kita, Eiji; Mitsumata, Chiharu; Ono, Kanta; Yanagihara, Hideto; Matsumoto, Makoto
2015-05-01
Visualization of the magnetic domain structure is indispensable to the investigation of magnetization processes and the coercivity mechanism. It is necessary to develop a reconstruction method from the reciprocal-space image to the real-space image. For this purpose, it is necessary to solve the problem of missing phase information in the reciprocal-space image. We propose the method of extend Fourier image with mean-value padding to compensate for the phase information. We visualized the magnetic domain structure using the Reverse Monte Carlo method with simulated annealing to accelerate the calculation. With this technique, we demonstrated the restoration of the magnetic domain structure, obtained magnetization and magnetic domain width, and reproduced the characteristic form that constitutes a magnetic domain.
Image encryption based on double folding operation in fractional Fourier transform domain
NASA Astrophysics Data System (ADS)
Liu, Zhengjun; Wang, Xiuying; Liu, Shutian
2009-11-01
Based on fractional Fourier transform, the double folding operation is studied and introduced into image encryption. This method can implement a kind of the encoding with real number. This characteristic is convenient to the storage and transmission of the encrypted image. The corresponding experimental setup is similar to the scheme of double random phase encoding. With computer, some numerical simulations have been achieved. The analysis on the algorithm from the aspects of validity, security and robustness is made. The calculated results have been demonstrated that the algorithm is effective and has good security.
Image encryption based on extended fractional Fourier transform and digital holography technique
NASA Astrophysics Data System (ADS)
Wang, Xiaogang; Zhao, Daomu; Chen, Linfei
2006-04-01
We present a new optical image encryption algorithm that is based on extended fractional Fourier transform (FRT) and digital holography technique. We can perform the encryption and decryption with more parameters compared with earlier similar methods in FRT domain. In the extended FRT encryption system, the input data to be encrypted is extended fractional Fourier transformed two times and random phase mask is placed at the output plane of the first extended FRT. By use of an interference with a wave from another random phase mask, the encrypted data is stored as a digital hologram. The data retrieval is operated by all-digital means. Computer simulations are presented to verify its validity and efficiency.
Spectroscopy, dynamics, and c aos of the CS, molecule: Fourier transform and phase-space analysis
Spectroscopy, dynamics, and c aos of the CS, molecule: Fourier transform and phase-space analysis J sevenparameters.Analysis of the spectraby the statistical Fourier transform technique. P. Pique@ and M. Joyeux Laboratoire de Spectromktrie Physique, Universitt Joseph Fourier de Grenoble
The use of Fourier reverse transforms in crystallographic phase refinement
Ringrose, S.
1997-10-08
Often a crystallographer obtains an electron density map which shows only part of the structure. In such cases, the phasing of the trial model is poor enough that the electron density map may show peaks in some of the atomic positions, but other atomic positions are not visible. There may also be extraneous peaks present which are not due to atomic positions. A method for determination of crystal structures that have resisted solution through normal crystallographic methods has been developed. PHASER is a series of FORTRAN programs which aids in the structure solution of poorly phased electron density maps by refining the crystallographic phases. It facilitates the refinement of such poorly phased electron density maps for difficult structures which might otherwise not be solvable. The trial model, which serves as the starting point for the phase refinement, may be acquired by several routes such as direct methods or Patterson methods. Modifications are made to the reverse transform process based on several assumptions. First, the starting electron density map is modified based on the fact that physically the electron density map must be non-negative at all points. In practice a small positive cutoff is used. A reverse Fourier transform is computed based on the modified electron density map. Secondly, the authors assume that a better electron density map will result by using the observed magnitudes of the structure factors combined with the phases calculated in the reverse transform. After convergence has been reached, more atomic positions and less extraneous peaks are observed in the refined electron density map. The starting model need not be very large to achieve success with PHASER; successful phase refinement has been achieved with a starting model that consists of only 5% of the total scattering power of the full molecule. The second part of the thesis discusses three crystal structure determinations.
Phase-shifting windowed Fourier ridges for determination of phase derivatives
NASA Astrophysics Data System (ADS)
Qian, Kemao; Soon, Seah Hock; Asundi, Anand
2003-09-01
Determination of the phase or phase derivative from interferometric fringe patterns is an important task in optical interferometry. The use of wavelet ridges was recently shown to be an effective method for phase retrieval from a single fringe pattern. One necessary requirement in this method is the need for carrier frequency. In cases when carrier frequency is not available, the novel phase-shifting windowed Fourier ridges method can be used. Phase derivatives with the proper sign can be directly retrieved even in the presence of noise. An application for curvature determination from speckle shearographic fringes demonstrates the effectiveness of the method.
The data processing pipeline for the Herschel/SPIRE Imaging Fourier Transform Spectrometer
Naylor, David A.
The data processing pipeline for the Herschel/SPIRE Imaging Fourier Transform Spectrometer Trevor R the data processing pipeline to generate calibrated data products from the Spectral and Photometric Imaging Receiver (SPIRE) imaging Fourier Transform Spectrometer. The pipeline processes telemetry from SPIRE point
Efficient Fourier image analysis algorithm for aligned rectangular and trapezoidal wafer structures
Chiao-Fe Shu; Ramesh C. Jain
1992-01-01
We present an efficient algorithm to compute the critical dimensions of aligned rectangular and trapezoidal wafer structures using images generated by a Fourier imaging system. We show that the Fourier images of aligned rectangular and trapezoidal structures are separable functions. This allows us to project them onto x and y coordinates and simplifies the computation process. We compute the critical
A Study of Motion Artifacts of Fourier-Based Image Construction
Lu, Jian-yu
A Study of Motion Artifacts of Fourier-Based Image Construction Jing Wang and Jian-yu Lu resolution, field of view, and to reduce sidelobe, it is important to study the effects of motion is small. Keywords- Motion artifacts; High frame rate imaging; Medical imaging; Fourier; Limited
PITH ESTIMATION ON ROUGH LOG END IMAGES USING LOCAL FOURIER SPECTRUM ANALYSIS
Uhl, Andreas
PITH ESTIMATION ON ROUGH LOG END IMAGES USING LOCAL FOURIER SPECTRUM ANALYSIS Rudolf Schraml. This work evaluates two pith estimation algorithms using four different local Fourier Spectrum analysis and principal component analysis for local Fourier Spectrum analysis achieve the best accu- racy and timing
Electrospray Diagnostics by Fourier Analysis of Current Oscillations and Fast Imaging
Vertes, Akos
Electrospray Diagnostics by Fourier Analysis of Current Oscillations and Fast Imaging Lida Parvin current and its Fourier spectrum were monitored under a wide range of conditions, that is, as a function of the spray voltage, liquid flow rate, and composition. Most Fourier spectra indicated a strong dc component
Multiple-image encryption scheme based on cascaded fractional Fourier transform.
Kong, Dezhao; Shen, Xueju; Xu, Qinzu; Xin, Wang; Guo, Haiqiong
2013-04-20
A multiple-image encryption scheme based on cascaded fractional Fourier transform is proposed. In the scheme, images are successively coded into the amplitude and phase of the input by cascading stages, which ends up with an encrypted image and a series of keys. The scheme takes full advantage of multikeys and the cascaded relationships of all stages, and it not only realizes image encryption but also achieves higher safety and more diverse applications. So multiuser authentication and hierarchical encryption are achieved. Numerical simulation verifies the feasibility of the method and demonstrates the security of the scheme and decryption characteristics. Finally, flexibility and variability of the scheme in application are discussed, and the simple photoelectric mixed devices to realize the scheme are proposed. PMID:23669669
Optical phase retrieval by phase-space tomography and fractional-order Fourier transforms
D. F. McAlister; M. Beck; L. Clarke; A. Mayer; M. G. Raymer
1995-01-01
Phase-space tomography is experimentally demonstrated for the determination of the spatially varying amplitude and phase of a quasi-monochromatic optical f ield by measurements of intensity only. Both fully and partially coherent sources are characterized. The method, which makes use of the fractional-order Fourier transform, also yields the Wigner distribution of the f ield and works in one or two dimensions.
Rossmann, Michael G.
1997-01-01
Images using Fourier Analysis INGO STELLER,af ROBERT BOLOTOVSKY AND MICHAEL G. ROSSMANN* Department-dimensional Fourier analysis. A large Fourier term will be found that has a periodicity corresponding
Amplitude and phase fourier correlation of ``twin'' GC-spectra of fatty acids from sheep dairy
NASA Astrophysics Data System (ADS)
Teusdea, Alin C.; Gabor, Gianina; Hilma, Elena
2012-08-01
Authors present the discrimination performances of amplitude and phase-only Fourier correlation over the "twin" typed GC-spectra of sheep milk and ripened cheese. Therefore, in order to assess the most robust Fourier correlation method for the "twin" GC-spectra discrimination, the correlation matrix is built up over 17 analyzed GC-spectra in both amplitude and phase domains.
Development of an Imaging Fourier Transform Spectrometer for Astronomy
NASA Astrophysics Data System (ADS)
Grandmont, Frederic; Drissen, Laurent; Joncas, Gilles
2003-02-01
We present an overview of the past and current development of the Imaging Fourier Transform Spectrometer (IFTS) concept for ground telescopes produced in collaboration between ABB Bomem and Université Laval. This instrument intends to produce spectra of variable resolutions up to R = ?/?? = 10 000 from the near UV to the near IR (350 nm to 900 nm). It is designed to fit the f/8 focus of the Mont Mégantic 1.6m optical telescope in Québec. The large number of spatial elements (> 1 million pixels) is the novel aspect of this FTS design along with innovative metrology system. Heritage from Next Generation Space Telescope (NGST) IFTS concept, Lawrence Livermore National Laboratory (LLNL)- ABB Bomem instrument and commercial ABB Bomem DA series FTS are reviewed. Techniques for accurately servoing the moving mirror alignment to a value smaller than 0.1 arc second and position to sub nanometer value are discussed. Also presented are results from the assembled interferometer sub-system.
Multiresolution graph Fourier transform for compression of piecewise smooth images.
Hu, Wei; Cheung, Gene; Ortega, Antonio; Au, Oscar C
2015-01-01
Piecewise smooth (PWS) images (e.g., depth maps or animation images) contain unique signal characteristics such as sharp object boundaries and slowly varying interior surfaces. Leveraging on recent advances in graph signal processing, in this paper, we propose to compress the PWS images using suitable graph Fourier transforms (GFTs) to minimize the total signal representation cost of each pixel block, considering both the sparsity of the signal's transform coefficients and the compactness of transform description. Unlike fixed transforms, such as the discrete cosine transform, we can adapt GFT to a particular class of pixel blocks. In particular, we select one among a defined search space of GFTs to minimize total representation cost via our proposed algorithms, leveraging on graph optimization techniques, such as spectral clustering and minimum graph cuts. Furthermore, for practical implementation of GFT, we introduce two techniques to reduce computation complexity. First, at the encoder, we low-pass filter and downsample a high-resolution (HR) pixel block to obtain a low-resolution (LR) one, so that a LR-GFT can be employed. At the decoder, upsampling and interpolation are performed adaptively along HR boundaries coded using arithmetic edge coding, so that sharp object boundaries can be well preserved. Second, instead of computing GFT from a graph in real-time via eigen-decomposition, the most popular LR-GFTs are pre-computed and stored in a table for lookup during encoding and decoding. Using depth maps and computer-graphics images as examples of the PWS images, experimental results show that our proposed multiresolution-GFT scheme outperforms H.264 intra by 6.8 dB on average in peak signal-to-noise ratio at the same bit rate. PMID:25494508
Rosen, Joseph
of synthesizing three types of computer-generated hologram (CGH); Fourier, Fresnel and image CGHs. These holograms is extended in order to create other types of CGHs. There are several types of holograms, among them are the three well-known types; Fourier, Fresnel and image holograms6 . The differences between these holograms
Te Hu; Xiao-Fan Qian
2011-01-01
A signification characteristic is found by analyzing lensless Fourier digital hologram and synthetic aperture holography that is the imaging surface of reconstructed image of lensless Fourier digital hologram just is focus plane of positive lens that is unrelated with wavelength of restruction and recording and their ratio. The nature is propitious to resolve the problem of DMD display caused by
NASA Astrophysics Data System (ADS)
Zhao, Ming; Kemao, Qian
2013-06-01
Windowed Fourier ridges algorithm can provide a quality map to assist the quality-guided phase unwrapping. Its performance for discontinuous phase maps is investigated in this paper, where the influence of window size in the algorithm is examined. Three discontinuous phase boundaries, straight, curved, and fused, are tested for both noiseless and noisy situations. Encouraging results are observed. Small window size can be used for higher boundary detection accuracy and can be enlarged if noise is heavy and/or the discontinuities are not obvious in a small area.
NASA Astrophysics Data System (ADS)
Jericevic, Zeljko; McGavran, Loris; Smith, Louis C.
1990-07-01
Eigenanalysis is a mathematical approach used to obtain characteristic roots and vectors from a matrix and is an important method for extracting information from digital images in microscopy. To use multiple images as input data, the images must be correctly aligned and the pattern common for each input image must not be geometrically distorted. Otherwise, the different geometries produce blurring. Alignment and removal of geometric distortion from digital images of random examples of 20 high resolution preparations of human karyotypes has been achieved by the eigenanalysis performed in the Fourier spectral domain on the phase and the amplitude of the Fourier transform. Our results show that eigenanalysis in the frequency & un provides a better resolution of features than does eigenanalysis in the spatial domain and makes it possible to construct statistically based prototypes.
NASA Astrophysics Data System (ADS)
Kawashima, Natsumi; Suzuki, Yo; Qi, Wei; Hosono, Satsuki; Saito, Tsubasa; Ogawa, Satoshi; Sato, Shun; Fujiwara, Masaru; Nishiyama, Akira; Wada, Kenji; Tanaka, Naotaka; Ishimaru, Ichiro
2015-03-01
We proposed the imaging-type 2-dimensional Fourier spectroscopy that is a near-common-path interferometer with strong robustness against mechanical vibrations. We introduced the miniature uncooled infrared microbolometer arrays for smartphone (e.g. product name: FILR ONE price: around 400USD). And we constructed the phase-shifter with the piezo impact drive mechanism (maker: Technohands.co.Ltd., stroke: 4.5mm, resolution: 0.01?m, size: 20mm, price: around 800USD). Thus, we realized the palm-size mid-infrared spectroscopic imager [size: L56mm×W69mm×H43mm weight: 500g]. And by using wide-angle lens as objective lens, the proposed method can obtain the wide-field 2- dimensional middle-infrared (wavelength: 7.5-13.5[?m]) spectroscopic imaging of radiation lights emitted from human bodies itself
Liquid crystal projection image depixelization by spatial phase scrambling
NASA Astrophysics Data System (ADS)
Yang, Xiangyang; Li, Nan; Jutamulia, Suganda
1996-03-01
A technique to remove the pixel structure by randomly scrambling the relative phase among the multiple spatial spectra is described. Due to the pixel structure of the liquid crystal display panel, multiple spectra are generated at the Fourier spectrum plane (usually at the back focal plane of the imaging lens). A transparent phase mask is placed at the Fourier spectrum plane such that each spectral order is modulated by one of the subareas of the phase mask. The thickness of these phase mask subareas are randomly assigned and the phase delay resulted from each pair of subareas is longer than the coherent length of the light source, which is about one micron for white light. Such a phase scrambling eliminates the coherence between different spectral orders, therefore, the reconstructed images from the multiple spectra will superimpose incoherently and the pixel structure will not be observed in the projection image.
Fourier Based Image Registration for Sub-Pixel Using Pyramid Edge Detection and Line Fitting
Kee Baek Kim; Jong Soo Kim; Jong Soo Choi
2008-01-01
Image registration has been widely used in many works of image processing. But it is difficult to find the accuracy information such as translation, rotation, and scaling between images. This paper proposes an algorithm that Fourier based image registration using the pyramid edge detection and line fitting. It is possible to find the registration information of sub-pixel. So, we can
Fourier-domain digital holographic optical coherence imaging of living tissue
Nolte, David D.
optical coherence imaging is a full-frame coherence-gated imaging approach that uses a CCD cameraFourier-domain digital holographic optical coherence imaging of living tissue Kwan Jeong,1, * John reconstruction. We have applied this technique for the depth-resolved imaging of rat osteogenic tumor
Fourier-domain holographic optical coherence imaging of tumor spheroids and mouse eye
Nolte, David D.
free in practice and opens the full dynamic range of the CCD camera for imaging into tissue. The keyFourier-domain holographic optical coherence imaging of tumor spheroids and mouse eye Kwan Jeong several advantages over image-domain holography for optical coherence imaging of tissue. Writing
Liquid-crystal projection image depixelization by spatial phase scrambling
NASA Astrophysics Data System (ADS)
Yang, Xiangyang; Jutamulia, Suganda; Li, Nan
1996-08-01
A technique that removes the pixel structure by scrambling the relative phases among multiple spatial spectra is described. Because of the pixel structure of the liquid-crystal-display (LCD) panel, multiple spectra are generated at the Fourier-spectrum plane (usually at the back focal plane of the imaging lens). A transparent phase mask is placed at the Fourier-spectrum plane such that each spectral order is modulated by one of the subareas of the phase mask, and the phase delay resulting from each pair of subareas is longer than the coherent length of the light source, which is approximately 1 m for the wideband white light sources used in most of LCD s. Such a phase-scrambling technique eliminates the coherence between different spectral orders; therefore, the reconstructed images from the multiple spectra will superimpose incoherently, and the pixel structure will not be observed in the projection image.
Liquid-crystal projection image depixelization by spatial phase scrambling.
Yang, X; Jutamulia, S; Li, N
1996-08-10
A technique that removes the pixel structure by scrambling the relative phases among multiple spatial spectra is described. Because of the pixel structure of the liquid-crystal-display (LCD) panel, multiple spectra are generated at the Fourier-spectrum plane (usually at the back focal plane of the imaging lens). A transparent phase mask is placed at the Fourier-spectrum plane such that each spectral order is modulated by one of the subareas of the phase mask, and the phase delay resulting from each pair of subareas is longer than the coherent length of the light source, which is approximately 1 ?m for the wideband white light sources used in most of LCD's. Such a phase-scrambling technique eliminates the coherence between different spectral orders; therefore, the reconstructed images from the multiple spectra will superimpose incoherently, and the pixel structure will not be observed in the projection image. PMID:21102876
M. Hayes
1982-01-01
This paper addresses two fundamental issues involved in the reconstruction of a multidimensional sequence from either the phase or magnitude of its Fourier transform. The first issue relates to the uniqueness of a multidimensional sequence in terms of its phase or magnitude. Although phase or magnitude information alone is not sufficient, in general, to uniquely specify a sequence, a large
New 2D discrete Fourier transforms in image processing
NASA Astrophysics Data System (ADS)
Grigoryan, Artyom M.; Agaian, Sos S.
2015-03-01
In this paper, the concept of the two-dimensional discrete Fourier transformation (2-D DFT) is defined in the general case, when the form of relation between the spatial-points (x, y) and frequency-points (?1, ?2) is defined in the exponential kernel of the transformation by a nonlinear form L(x, y; ?1, ?2). The traditional concept of the 2-D DFT uses the Diaphanous form x?1 +y?2 and this 2-D DFT is the particular case of the Fourier transform described by the form L(x, y; ?1, ?2). Properties of the general 2-D discrete Fourier transform are described and examples are given. The special case of the N × N-point 2-D Fourier transforms, when N = 2r, r > 1, is analyzed and effective representation of these transforms is proposed. The proposed concept of nonlinear forms can be also applied for other transformations such as Hartley, Hadamard, and cosine transformations.
Complete fourier direct magnetic resonance imaging (CFD-MRI) for diffusion MRI
Özcan, Alpay
2013-01-01
The foundation for an accurate and unifying Fourier-based theory of diffusion weighted magnetic resonance imaging (DW–MRI) is constructed by carefully re-examining the first principles of DW–MRI signal formation and deriving its mathematical model from scratch. The derivations are specifically obtained for DW–MRI signal by including all of its elements (e.g., imaging gradients) using complex values. Particle methods are utilized in contrast to conventional partial differential equations approach. The signal is shown to be the Fourier transform of the joint distribution of number of the magnetic moments (at a given location at the initial time) and magnetic moment displacement integrals. In effect, the k-space is augmented by three more dimensions, corresponding to the frequency variables dual to displacement integral vectors. The joint distribution function is recovered by applying the Fourier transform to the complete high-dimensional data set. In the process, to obtain a physically meaningful real valued distribution function, phase corrections are applied for the re-establishment of Hermitian symmetry in the signal. Consequently, the method is fully unconstrained and directly presents the distribution of displacement integrals without any assumptions such as symmetry or Markovian property. The joint distribution function is visualized with isosurfaces, which describe the displacement integrals, overlaid on the distribution map of the number of magnetic moments with low mobility. The model provides an accurate description of the molecular motion measurements via DW–MRI. The improvement of the characterization of tissue microstructure leads to a better localization, detection and assessment of biological properties such as white matter integrity. The results are demonstrated on the experimental data obtained from an ex vivo baboon brain. PMID:23596401
Extreme Ultraviolet Phase Contrast Imaging
Denbeaux, Gregory; Garg, Rashi; Aquila, Andy; Barty, Anton; Goldberg, Kenneth; Gullikson, Eric; Liu, Yanwei; Wood, Obert
2005-11-01
The conclusions of this report are: (1) zone plate microscopy provides high resolution imaging of EUV masks; (2) using phase plates in the back focal plane of the objective lens can provide contrast mechanisms for measurement of the phase shift from defects on the mask; (3) the first high resolution EUV Zernike phase contrast images have been acquired; and (4) future work will include phase contrast mode in reflection from an EUV mask to directly measure the reflectivity and phase shift from defects.
NASA Astrophysics Data System (ADS)
Romijn, Elisabeth I.; Lilledahl, Magnus B.
2013-02-01
One of the main advantages of nonlinear microscopy is that it provides 3D imaging capability. Second harmonic generation is widely used to image the 3D structure of collagen fibers, and several works have highlighted the modification of the collagen fiber fabric in important diseases. By using an ellipsoidal specific fitting technique on the Fourier transformed image, we show, using both synthetic images and SHG images from cartilage, that the 3D direction of the collagen fibers can be robustly determined.
Midwave infrared imaging Fourier transform spectrometry of combustion plumes
NASA Astrophysics Data System (ADS)
Bradley, Kenneth C.
A midwave infrared (MWIR) imaging Fourier transform spectrometer (IFTS) was used to successfully capture and analyze hyperspectral imagery of combustion plumes. Jet engine exhaust data from a small turbojet engine burning diesel fuel at a low rate of 300 cm3/min was collected at 1 cm -1 resolution from a side-plume vantage point on a 200x64 pixel window at a range of 11.2 meters. Spectral features of H2O, CO, and CO2 were present, and showed spatial variability within the plume structure. An array of thermocouple probes was positioned within the plume to aid in temperature analysis. A single-temperature plume model was implemented to obtain spatially-varying temperatures and plume concentrations. Model-fitted temperatures of 811 +/- 1.5 K and 543 +/- 1.6 K were obtained from plume regions in close proximity to thermocouple probes measuring temperatures of 719 K and 522 K, respectively. Industrial smokestack plume data from a coal-burning stack collected at 0.25 cm-1 resolution at a range of 600 meters featured strong emission from NO, CO, CO2, SO 2, and HCl in the spectral region 1800-3000 cm-1. A simplified radiative transfer model was employed to derive temperature and concentrations for clustered regions of the 128x64 pixel scene, with corresponding statistical error bounds. The hottest region (closest to stack centerline) was 401 +/- 0.36 K, compared to an in-stack measurement of 406 K, and model-derived concentration values of NO, CO2, and SO2 were 140 +/- 1 ppmV, 110,400 +/- 950 ppmV, and 382 +/- 4 ppmV compared to in-stack measurements of 120 ppmV (NOx), 94,000 ppmV, and 382 ppmV, respectively. In-stack measurements of CO and HCl were not provided by the stack operator, but model-derived values of 19 +/- 0.2 ppmV and 111 +/- 1 ppmV are reported near stack centerline. A deployment to Dugway Proving Grounds, UT to collect hyperspectral imagery of chemical and biological threat agent simulants resulted in weak spectral signatures from several species. Plume detection of methyl salicilate was achieved from both a stack release and explosive detonation, although spectral identification was not accomplished due to weak signal strength.
Simple and robust digital holography for phase imaging of microstructure
Xiufa Song; Zhiwei Tang; Huaying Wang
2009-01-01
Digital holography is particularly well suited for characterization of microstructure such as surface shape, surface nanostructures and surface roughness. The wavefront recording and reconstruction with lensless Fourier transform digital holography is analyzed. By using a special 3-D minute object, the simulation and experimental investigation is performed. The accurate intensity and phase image is obtained with the lateral resolution of 2.76
Crystallographic phase retrieval through image processing under constraints
NASA Astrophysics Data System (ADS)
Zhang, Kam Y.
1993-11-01
The crystallographic image processing techniques of Sayre's equation, molecular averaging, solvent flattening and histogram matching are combined in an integrated procedure for macromolecular phase retrieval. It employs the constraints of the local shape of electron density, equal molecules, solvent flatness and correct electron density distribution. These constraints on electron density image are satisfied simultaneously by solving a system of non- linear equations using fast Fourier transform. The electron density image is further filtered under the constraint of observed diffraction amplitudes. The effect of each constraint on phase retrieval is examined. The constraints are found to work synergistically in phase retrieval. Test results on 2Zn insulin are presented.
NASA Astrophysics Data System (ADS)
Hu, Te; Qian, Xiao-fan
2011-06-01
A signification characteristic is found by analyzing lensless Fourier digital hologram and synthetic aperture holography that is the imaging surface of reconstructed image of lensless Fourier digital hologram just is focus plane of positive lens that is unrelated with wavelength of restruction and recording and their ratio. The nature is propitious to resolve the problem of DMD display caused by unstable holographic imaging surface. Zero order diffraction image is focused on nearby center of focal surface and imaging zone is rapidly contracted that largely improved quality of reconstructed image. Meanwhile, position of holographic reconstructed image is not to be altered when parallel moving lensless Fourier digital holography on the holographic image plane that is easier to improve hologram duty cycle, DMD availability and quality of reconstructed image with theory of synthetic aperture that attained by single illumination. According to this analysis, a new method is proposed that combine lensless Fourier digital holography with synthetic aperture that could improve quality of DMD reconstructed image. We provided laboratory results and verified all theory analysis that totally proved the method is available and feasible.
Iterative reconstruction of speech from short-time Fourier transform phase and magnitude spectra
Iterative reconstruction of speech from short-time Fourier transform phase and magnitude spectra dimensional, signal reconstruction (specifically speech signals) from the magnitude spectrum and the phase magnitude spectrum, and (iii) a signal can be reconstructed to within a scale factor from its magnitude
Nonlinear optical Fourier filtering technique for medical image processing
Rao, D.V.G.L.N.
optical filtering; optical Fourier processing; bacteriorhodopsin film; breast cancer; mammography. Paper. 3, 2005; published online Jul. 15, 2005. 1 Introduction Breast cancer is still one of the leading causes of mortality in women.1 Early detection of the cancer is extremely important for successful
Nabin Ghoshal; J. K. Mandal
2011-01-01
T his paper presents a novel steganographic schemes based on Discrete Fourier Transformation (DFT) and demonstrates the multimedia colour image authentication process in frequency domain for wireless communication(DFTMCIAWC). Authentication is done through embedding secrete message\\/image into the transformed frequency components of the source image at message originating node. The DFT is applied on sub-image block called mask of size 2
Color holographic image by using digital lensless Fourier transform holography with optical fiber
NASA Astrophysics Data System (ADS)
Chen, Li; Ma, Xiao; Wang, Qu
2012-04-01
A new method of lensless Fourier transform holography for color reconstruction image is presented. With this method, the recording distance can be kept invariant in recording process. The resolutions of reconstruction images can be adjusted in the same recording distance. Three lasers with different wavelengths are used in an experimental setup to synthesize a color image in a reconstruction process. An optical fiber is used effectively, and the quality of the reconstruction image is improved after filter operation.
Ultrasound pulse-echo imaging using the split-step Fourier propagator
Lianjie Huang; Youli Quan
2007-01-01
Ultrasonic reflection imaging has the potential to produce higher image resolution than transmission tomography, but imaging resolution and quality still need to be further improved for early cancer detection and diagnosis. We present an ultrasound reflection image reconstruction method using the split-step Fourier propagator. It is based on recursive inward continuation of ultrasonic wavefields in the frequency-space and frequency-wavenumber domains.
Theory of laser array phase locking by Fourier coupling
Vysotskii, D V; Napartovich, A P; Troshchieva, V N [State Research Center of Russian Federation 'Troitsk Institute for Innovation and Fusion Research', Troitsk, Moscow Region (Russian Federation)
2007-04-30
The type of coupling in a fibre laser array phase locked with the help of an external mirror located at the focal distance from the plane of output ends of individual lasers is studied analytically. The explicit expression is derived for the eigenvalue of the resonator and the restriction on the width of the tuning range in which laser array phase locking is preserved is determined. The influence of the spread in the optical lengths of fibres on the phase-locking efficiency is considered. The phase-locking efficiency is analysed for the spread of optical lengths of fibres considerably exceeding the radiation wavelength. (control of laser radiation parameters)
Optical encryption by combining image scrambling techniques in fractional Fourier domains
NASA Astrophysics Data System (ADS)
Liu, Shi; Sheridan, John T.
2013-01-01
In this paper, we propose a novel scheme for optical information hiding (encryption) of two-dimensional images by combining image scrambling techniques in fractional Fourier domains. The image is initially randomly shifted using the jigsaw transform algorithm, and then a pixel scrambling technique based on the Arnold transform (ART) is applied. The scrambled image is then encrypted in a randomly chosen fractional Fourier domain. These processes can then be iteratively repeated. The parameters of the architecture, including the jigsaw permutation indices, Arnold frequencies, and fractional Fourier orders, form a very large key space enhancing the security level of the proposed encryption system. Optical implementations are discussed as numerical implementation algorithms. Numerical simulation results are presented to demonstrate the system's flexibility and robustness.
Iterative Image Reconstruction Using Inverse Fourier Rebinning for Fully 3-D PET
Sanghee Cho; Quanzheng Li; Sangtae Ahn; Bing Bai; Richard M. Leahy
2007-01-01
We describe a fast forward and back projector pair based on inverse Fourier rebinning for use in iterative image reconstruction for fully 3-D positron emission tomography (PET). The projector pair is used as part of a factored system matrix that takes into account detector-pair response by using shift-variant sinogram blur kernels, thereby combining the computational advantages of Fourier rebinning with
IMAGE VOLUME DENOISING USING A FOURIER-WAVELET BASIS Roland G. Wilson Nasir M. Rajpoot
Rajpoot, Nasir
IMAGE VOLUME DENOISING USING A FOURIER-WAVELET BASIS Roland G. Wilson Nasir M. Rajpoot Department. The image sequence is represented using a non-adaptive wavelet basis, carefully chosen for its ability and are quite robust. At its simplest, wavelet `denoising' is partic- ularly attractive, requiring computation
Camilla Ricci; K. L. Andrew Chan; Sergei G. Kazarian
2006-01-01
Conventional FTIR spectroscopy and microscopy has been widely used in forensic science. New opportunities exist to obtain rapid chemical images and to enhance the sensitivity of detection of trace materials using attenuated total reflection (ATR) Fourier transform infrared (FTIR) spectroscopy coupled with a focal-plane array (FPA) detector. In this work, the sensitivity of ATR-FTIR spectroscopic imaging using three different kinds
Tooth-Caries Early Diagnosis and Mapping by Fourier Transform Spectral Imaging Fluorescence
Michal Fisher; Liviu Feller; Israel Schechter
2002-01-01
A new method for fast diagnosis and mapping of tooth caries is suggested. The method is based on autofluorescence and application of Fourier transform imaging microscopy. This device provides simultaneous fluorescence spectra at all pixels of the examined sample. A cooled CCD detector, directly connected to the spectrometer, collects the imaging interferograms and allows for spectral mapping. The feasibility of
Fourier-Mellin registration of line-delineated tabular document images
Luke A. D. Hutchison; William A. Barrett
2006-01-01
Image registration (or alignment) is a useful preprocessing tool for assisting in manual data extraction from handwritten forms, as well as for preparing documents for batch OCR of specific page regions. A new technique is presented for fast registration of lined tabular document images in the presence of a global affine transformation, using the Discrete Fourier--Mellin Transform (DFMT). Each component
Compressed Ultrasound Imaging by Sub-Nyquist Sampling and Fourier Domain Beamforming
Eldar, Yonina
1 Compressed Ultrasound Imaging by Sub-Nyquist Sampling and Fourier Domain Beamforming Alon Eilam the number of samples needed to reconstruct an ultrasound image. We demonstrate our methods on in vivo present an implementation on an ultrasound machine. Utilizing the low data rate, beamforming can be done
Ultrasound imaging of long bone fractures and healing with the split-step fourier imaging method.
Li, Hongjiang; Le, Lawrence H; Sacchi, Mauricio D; Lou, Edmond H M
2013-08-01
We applied the split-step Fourier imaging method to back-propagate the ultrasound zero-offset wavefields acquired on the bone surface to the sources of scatterers, which are the reflecting interfaces. The method required, as an input, an estimated slowness (reciprocal of half the velocity) model to map the time-dependent sonogram to the depth image, which provides the geometric properties of the interfaces. The slowness was approximated by a depth-dependent term and a first-order spatially varying perturbation. Simulated data sets were used to validate the method. The reconstructed images show proper mapping of the interfaces and the fracture, and a reasonable cortical thickness measurement with 8.3% error. The images also illustrate clearly the bone fracture healing process of a 1-mm-wide 45° inclined crack with different in-filled tissue velocities for various healing stages. Reconstruction of a fractured bone plate using data from an in vitro experiment is also presented. This study suggests that the proposed imaging method has good potential in quantification of bone fractures and monitoring of the fracture healing process. PMID:23838363
K. Arai; C. Belthangady; H. Zhang; N. Bar-Gill; S. J. DeVience; P. Cappellaro; A. Yacoby; R. L. Walsworth
2014-09-09
Optically-detected magnetic resonance using Nitrogen Vacancy (NV) color centres in diamond is a leading modality for nanoscale magnetic field imaging, as it provides single electron spin sensitivity, three-dimensional resolution better than 1 nm, and applicability to a wide range of physical and biological samples under ambient conditions. To date, however, NV-diamond magnetic imaging has been performed using real space techniques, which are either limited by optical diffraction to 250 nm resolution or require slow, point-by-point scanning for nanoscale resolution, e.g., using an atomic force microscope, magnetic tip, or super-resolution optical imaging. Here we introduce an alternative technique of Fourier magnetic imaging using NV-diamond. In analogy with conventional magnetic resonance imaging (MRI), we employ pulsed magnetic field gradients to phase-encode spatial information on NV electronic spins in wavenumber or k-space followed by a fast Fourier transform to yield real-space images with nanoscale resolution, wide field-of-view (FOV), and compressed sensing speed-up.
Zhao, Jianlin; Jiang, Hongzhen; Di, Jianglei
2008-02-18
The numerical recording and reconstruction of a color holographic image are achieved by using digital lensless Fourier transform holography. Firstly, for a color object, three monochromatic digital holograms with different wavelengths (red, green, blue) are recorded by a black-white CCD, respectively. Then the reconstructed monochromatic holographic images (red, green, blue) are adjusted to be same in size through padding digital holograms with zeros, and the corresponding digital color holographic image is acquired by accurately syncretizing the resized reconstructed monochromatic images. One of the advantages using lensless Fourier transform holography is that it can well assure the precise superposition of the reconstructed images. By applying median filtering technique and superposing the speckle fields with different distributions, the speckle noises are well suppressed and the quality of the digital color holographic image is greatly improved. This digital color holography with high quality of reconstruction effect would have potential applications on digital holographic display of color objects. PMID:18542331
Terahertz holography for imaging amplitude and phase objects.
Hack, Erwin; Zolliker, Peter
2014-06-30
A non-monochromatic THz Quantum Cascade Laser and an uncooled micro-bolometer array detector with VGA resolution are used in a beam-splitter free holographic set-up to measure amplitude and phase objects in transmission. Phase maps of the diffraction pattern are retrieved using the Fourier transform carrier fringe method; while a Fresnel-Kirchhoff back propagation algorithm is used to reconstruct the complex object image. A lateral resolution of 280 µm and a relative phase sensitivity of about 0.5 rad are estimated from reconstructed images of a metallic Siemens star and a polypropylene test structure, respectively. Simulations corroborate the experimental results. PMID:24977861
Real-time generation of atmospheric turbulence phase screen with non-uniform fast Fourier transform
NASA Astrophysics Data System (ADS)
Jia, Peng; Cai, Dongmei; Wang, Dong; Basden, Alastair
2015-06-01
High-fidelity Monte Carlo simulation of atmospheric turbulence phase screens is important for performance testing of astronomical adaptive optics systems. With a sparse spectrum model and an optimal sampling method, it is possible to generate an atmospheric turbulence phase screen with high fidelity. However, the phase screen generation speed is limited by the algorithm structure of this technique. A non-uniform fast Fourier transform technique is proposed in this paper to accelerate phase screen generation speed. This method is able to generate huge atmospheric turbulence phase screens with high fidelity and an acceptable time-cost enabling practical adaptive optics simulations of forthcoming Extremely Large Telescopes.
NASA Astrophysics Data System (ADS)
Li, Hongyan; Zhong, Liyun; Ma, Zhijian; Lu, Xiaoxu
2011-05-01
In on-axis lensless Fourier phase-shifting synthetic aperture digital holography, to compose all of the phase-shifting sub-holograms to a large synthetic aperture digital hologram effectively, firstly, the cross-correlation algorithm of the object waves is presented to correct the joint misplacement of the sub-holograms. Secondly, to make the phase-shifting synchronization matching of different sequence phase-shifting holograms, the cross-correlation algorithm of the phase-shifting holograms is employed. Compared with the traditional cross-correlation algorithm of the sub-holograms, the proposed approach makes the joint precision of the sub-holograms reach sub-pixel accuracy, and the resolution of the reconstructed image is improved significantly. In general, the proposed approach is effective in restraining the quality degradation of the synthetic reconstructed image that comes from the joint misplacement of the sub-holograms and the phase-shifting non-synchronization of the phase-shifting holograms.
Fabrication and Testing of Binary-Phase Fourier Gratings for Nonuniform Array Generation
NASA Technical Reports Server (NTRS)
Keys, Andrew S.; Crow, Robert W.; Ashley, Paul R.; Nelson, Tom R., Jr.; Parker, Jack H.; Beecher, Elizabeth A.
2004-01-01
This effort describes the fabrication and testing of binary-phase Fourier gratings designed to generate an incoherent array of output source points with nonuniform user-defined intensities, symmetric about the zeroth order. Like Dammann fanout gratings, these binary-phase Fourier gratings employ only two phase levels to generate a defined output array. Unlike Dammann fanout gratings, these gratings generate an array of nonuniform, user-defined intensities when projected into the far-field regime. The paper describes the process of design, fabrication, and testing for two different version of the binary-phase grating; one designed for a 12 micron wavelength, referred to as the Long-Wavelength Infrared (LWIR) grating, and one designed for a 5 micron wavelength, referred to as the Mid-Wavelength Infrared Grating (MWIR).
Estimation of motions in color image sequences using hypercomplex fourier transforms.
Alexiadis, Dimitrios S; Sergiadis, George D
2009-01-01
Although the motion estimation problem has been extensively studied, most of the proposed estimation approaches deal mainly with monochrome videos. The most usual way to apply them also in color image sequences is to process each color channel separately. A different, more sophisticated approach is to process the color channels in a "holistic" manner using quaternions, as proposed by Ell and Sangwine. In this paper, we extend standard spatiotemporal Fourier-based approaches to handle color image sequences, using the hypercomplex Fourier transform. We show that translational motions are manifested as energy concentration along planes in the hypercomplex 3-D Fourier domain and we describe a methodology to estimate the motions, based on this property. Furthermore, we compare the three-channels-separately approach with our approach and we show that the computational effort can be reduced by a factor of 1/3, using the hypercomplex Fourier transform. Also, we propose a simple, accompanying method to extract the moving objects in the hypercomplex Fourier domain. Our experimental results on synthetic and natural images verify our arguments throughout the paper. PMID:19095528
Phase imaging using polycapillary optics
NASA Astrophysics Data System (ADS)
Bashir, Sajid; Tahir, Sajjad; Petruccelli, Jonathan C.; MacDonald, C. A.
2014-09-01
Contrast in conventional imaging of soft tissues is often limited due to the very similar attenuation of tissues to be distinguished. Phase contrast techniques can enable discrimination of tissues with similar attenuation. A major limitation to the widespread adoption of phase-contrast techniques is that for tabletop sources the required degree of coherence generally requires a small (10 to 50 ?m) source. In this work, a polycapillary optic was employed to create a small virtual source from a large spot rotating anode. Phase contrast images obtained with two optics and several pinholes have been analyzed and preliminary results obtained for quantitative phase measurements.
NASA Astrophysics Data System (ADS)
Kulkarni, Rishikesh; Rastogi, Pramod
2015-07-01
This paper proposes a novel method for the simultaneous estimation of multiple interference phases from a single recording of the interference field in a multi-wave digital holographic interferometry set-up. The method involves the separation of signal components from the recorded interference field based on windowed Fourier transform based filtering and amplitude discrimination criteria. The proposed method possesses the advantages offered by windowed Fourier transform based filtering such as noise robustness and a high quality reconstruction of the signal components. The performance of the method is validated with numerical and experimental examples.
Spectral multiplexing and coherent-state decomposition in Fourier ptychographic imaging
Dong, Siyuan; Shiradkar, Radhika; Nanda, Pariksheet; Zheng, Guoan
2014-01-01
Information multiplexing is important for biomedical imaging and chemical sensing. In this paper, we report a microscopy imaging technique, termed state-multiplexed Fourier ptychography (FP), for information multiplexing and coherent-state decomposition. Similar to a typical Fourier ptychographic setting, we use an array of light sources to illuminate the sample from different incident angles and acquire corresponding low-resolution images using a monochromatic camera. In the reported technique, however, multiple light sources are lit up simultaneously for information multiplexing, and the acquired images thus represent incoherent summations of the sample transmission profiles corresponding to different coherent states. We show that, by using the state-multiplexed FP recovery routine, we can decompose the incoherent mixture of the FP acquisitions to recover a high-resolution sample image. We also show that, color-multiplexed imaging can be performed by simultaneously turning on R/G/B LEDs for data acquisition. The reported technique may provide a solution for handling the partially coherent effect of light sources used in Fourier ptychographic imaging platforms. It can also be used to replace spectral filter, gratings or other optical components for spectral multiplexing and demultiplexing. With the availability of cost-effective broadband LEDs, the reported technique may open up exciting opportunities for computational multispectral imaging. PMID:24940538
Gallery of datacubes obtained with the Livermore imaging Fourier transform spectrometer
NASA Astrophysics Data System (ADS)
Wurtz, Ronald E.; Wishnow, Edward H.; Blais-Ouellette, Sebastien; Cook, Kem H.; Holden, Bradford P.; Carr, Dennis J.; Stubbs, Christopher W.
2003-02-01
We have acquired spatial-spectral datacubes of astronomical objects using the Livermore visible-band imaging Fourier transform spectrometer at Apache Point Observatory. Each raw datacube contains hundreds of thousands of spectral interferograms. We present in-progress demonstrations of these observations.
Compressive Sensing Ensemble Average Propagator Estimation via 1 Spherical Polar Fourier Imaging
Boyer, Edmond
Compressive Sensing Ensemble Average Propagator Estimation via 1 Spherical Polar Fourier Imaging (ODF). They nor- mally need many samples, which limits their applications. Some Compressive Sensing (CS regularization. The weights are designed to enhance the sparsity. 1-SPFI significantly accelerates the ordinary
Study on the depth of focus of lensless Fourier transform digital holographic imaging system
Huaying Wang; Aili Qin; Yi Wang
2009-01-01
Based on the principle of digital holography and the criterion of the depth of focus of coherent lens imaging system, the depth of focus (DOF) of off-axis lensless Fourier transform digital holographic system is analyzed. The DOF expressions of digital holographic systems with symmetrical and unsymmetrical offset of reference point sources are deduced and presented. By using a minute vertical
Un nouvel ensemble de descripteurs de Fourier Clifford pour les images couleur
Paris-Sud XI, Université de
., 2009). Beside this approach, SIFT (Scale-Invariant Feature Transform) descriptors are a popular choice, descripteur couleur, algèbre de Clifford, images couleur, reconnaissance de formes KEYWORDS: Fourier transform are concatenated to form the feature vector. In order to avoid this marginal processing, other approaches consist
Fast Registration of Tabular Document Images Using the Fourier-Mellin Transform
Luke A. D. Hutchison; William A. Barrett
2004-01-01
A new technique is presented for quickly identifying global affine transformations applied to tabular document images, and to correct for those transformations. This technique, based on the Fourier-Mellin transform, is used to register (align) a set of tabular documents to each other. Each component of the affine transform is handled separately, which dramatically reduces the total parameter space of the
Ahmed Mahgoub; Thanh Nguyen; Raphaël Desbiens; André Zaccarin
2009-01-01
This paper presents an algorithm to align the frames obtained with a non-stationary imaging Fourier transform spectrometer (IFTS). These frames contain both relative motion and intensity variation due to the interference pattern of the IFTS called interferogram. Two motion estimation techniques are combined to register the frames with a sub-pixel precision. An approach based on mutual information is first used
Iterative tomographic image reconstruction using Fourier-based forward and back-projectors
Samuel Matej; Jeffrey A. Fessler; Ivan G. Kazantsev
2004-01-01
Iterative image reconstruction algorithms play an increasingly important role in modern tomographic systems, espe- cially in emission tomography. With the fast increase of the sizes of the tomographic data, reduction of the computation demands of the reconstruction algorithms is of great importance. Fourier- based forward and back-projection methods have the potential to considerably reduce the computation time in iterative recon-
Jacob L. Harley; Kevin C. Gross
2011-01-01
A Telops Hyper-Cam midwave infrared (1.5 - 5.5mum) imaging Fourier-transform spectrometer (IFTS) was used to estimate industrial smokestack total effluent mass flow rates by combining spectrally-determined species concentrations with flow rates estimated via analysis of sequential images in the raw interferogram cube. Measurements of the coalburning smokestack were made with the IFTS at a stand-off distance of 350m. 185 hyperspectral
NASA Astrophysics Data System (ADS)
Zhao, Jianlin; Lu, Hongqiang; Song, Xiaoshan; Li, Jifeng; Ma, Yanghua
2005-05-01
A novel encryption for optical image based on multistage fractional Fourier transforms (FRTs) and pixel scrambling technique is presented in this paper. The principle of pixel scrambling is described and an optical approach to realize the pixel scrambling and decoding is also proposed. Numerical simulation results are given to verify the algorithm, and relative error (RE) between the decoded images and the original image versus the deviation of fractional orders is discussed. Comparing with single FRT encryption, the security using this method for optical image encryption is greatly improved due to the introduction of the pixel scrambling technique.
NASA Astrophysics Data System (ADS)
Wang, Yong-Ying; Wang, Yu-Rong; Wang, Yong; Li, Hui-Juan; Sun, Wen-Jia
2007-07-01
A new method of optical image encryption with binary Fourier transform computer-generated hologram (CGH) and pixel-scrambling technology is presented. In this method, the orders of the pixel scrambling, as well as the encrypted image, are used as the keys to decrypt the original image. Therefore, higher security is achieved. Furthermore, the encrypted image is binary, so it is easy to be fabricated and robust against noise and distortion. Computer simulation results are given to verify the feasibility of this method and its robustness against occlusion and additional noise.
Choi, WooJhon; Baumann, Bernhard; Swanson, Eric A; Fujimoto, James G
2012-11-01
We present a numerical approach to extract the dispersion mismatch in ultrahigh-resolution Fourier domain optical coherence tomography (OCT) imaging of the retina. The method draws upon an analogy with a Shack-Hartmann wavefront sensor. By exploiting mathematical similarities between the expressions for aberration in optical imaging and dispersion mismatch in spectral / Fourier domain OCT, Shack-Hartmann principles can be extended from the two-dimensional paraxial wavevector space (or the x-y plane in the spatial domain) to the one-dimensional wavenumber space (or the z-axis in the spatial domain). For OCT imaging of the retina, different retinal layers, such as the retinal nerve fiber layer (RNFL), the photoreceptor inner and outer segment junction (IS/OS), or all the retinal layers near the retinal pigment epithelium (RPE) can be used as point source beacons in the axial direction, analogous to point source beacons used in conventional two-dimensional Shack-Hartman wavefront sensors for aberration characterization. Subtleties regarding speckle phenomena in optical imaging, which affect the Shack-Hartmann wavefront sensor used in adaptive optics, also occur analogously in this application. Using this approach and carefully suppressing speckle, the dispersion mismatch in spectral / Fourier domain OCT retinal imaging can be successfully extracted numerically and used for numerical dispersion compensation to generate sharper, ultrahigh-resolution OCT images. PMID:23187353
Single-channel color image encryption based on iterative fractional Fourier transform and chaos
NASA Astrophysics Data System (ADS)
Sui, Liansheng; Gao, Bo
2013-06-01
A single-channel color image encryption is proposed based on iterative fractional Fourier transform and two-coupled logistic map. Firstly, a gray scale image is constituted with three channels of the color image, and permuted by a sequence of chaotic pairs which is generated by two-coupled logistic map. Firstly, the permutation image is decomposed into three components again. Secondly, the first two components are encrypted into a single one based on iterative fractional Fourier transform. Similarly, the interim image and third component are encrypted into the final gray scale ciphertext with stationary white noise distribution, which has camouflage property to some extent. In the process of encryption and description, chaotic permutation makes the resulting image nonlinear and disorder both in spatial domain and frequency domain, and the proposed iterative fractional Fourier transform algorithm has faster convergent speed. Additionally, the encryption scheme enlarges the key space of the cryptosystem. Simulation results and security analysis verify the feasibility and effectiveness of this method.
Direct image reconstruction from a Fourier intensity pattern using HERALDO.
Guizar-Sicairos, Manuel; Fienup, James R
2008-11-15
We present what we believe to be the first experimental demonstration of a novel coherent lensless imaging technique: holography with extended reference by autocorrelation linear differential operator. Upon taking derivatives of the field autocorrelation this technique allows the direct reconstruction of an object complex-valued transmissivity from a measurement of its Fraunhofer diffraction pattern. We show reconstruction examples using a parallelogram, a thin slit, and a triangle as extended references. PMID:19015703
Fourier spectrum and phases for a signal in a finite interval
NASA Astrophysics Data System (ADS)
Belmont, Gérard; Dorville, Nicolas; Sahraoui, Fouad; Rezeau, Laurence
2015-04-01
When investigating the physics of turbulent media, as the solar wind or the magnetosheath plasmas, obtaining accurate Fourier spectra and phases is a crucial issue. For the different fields, the spectra allow in particular verifying whether one or several power laws can be determined in different frequency ranges. Accurate phases are necessary as well for all the "higher order statistics" studies in Fourier space, the coherence ones and for the polarization studies. Unfortunately, the Fourier analysis is not unique for a finite time interval of duration T: the frequencies lower than 1/T have a large influence on the result, which can hardly be controlled. This unknown "trend" has in particular the effect of introducing jumps at the edges of the interval, for the function under study itself, as well as for all its derivatives. The Fourier transform obtained directly by FFT (Fast Fourier Transform) is generally much influenced by these effects and cannot be used without care for wide band signals. The interference between the jumps and the signal itself provide in particular characteristic "hairs" on the spectrum, which are clearly visible on it with df?1/T. These fluctuations are usually eliminated by smoothing the spectrum, or by averaging several successive spectra. Nevertheless, such treatments introduce uncertainties on the spectral laws (the phases being anyway completely lost). Windowing is also a method currently used to suppress or decrease the jumps, but it modifies the signal (the windowed trend has a spectrum, which is convolved with the searched one) and the phases are generally much altered. Here, we present a new data processing technique to circumvent these difficulties. It takes advantage of the fact that the signal is generally not unknown out of the interval under study: the complete signal is tapered to this interval of interest thanks to a new window function, sharp but not square. This window function is chosen such that the spectrum obtained can be deconvolved almost exactly, through a minimization procedure based on the -weak- hypothesis that it is smooth at the scale of a few successive spectral points. Then, a later step allows reconstructing the phases. Tests with synthetic data and first applications to Cluster data are presented, which demonstrate the capability of the method to better estimate the Fourier spectra.
Novel Algorithm for Polar and Spherical Fourier Analysis on Two and Three Dimensional Images
NASA Astrophysics Data System (ADS)
Yang, Zhuo; Kamata, Sei-Ichiro
Polar and Spherical Fourier analysis can be used to extract rotation invariant features for image retrieval and pattern recognition tasks. They are demonstrated to show superiorities comparing with other methods on describing rotation invariant features of two and three dimensional images. Based on mathematical properties of trigonometric functions and associated Legendre polynomials, fast algorithms are proposed for multimedia applications like real time systems and large multimedia databases in order to increase the computation speed. The symmetric points are computed simultaneously. Inspired by relative prime number theory, systematic analysis are given in this paper. Novel algorithm is deduced that provide even faster speed. Proposed method are 9-15% faster than previous work. The experimental results on two and three dimensional images are given to illustrate the effectiveness of the proposed method. Multimedia signal processing applications that need real time polar and spherical Fourier analysis can be benefit from this work.
Severa, L; Máchal, L; Svábová, L; Mamica, O
2010-05-01
This study quantified and evaluated the variability of sperm head shape for 10 different stallions. Sperm head shape characteristics including sperm head length to width ratio, position of the center of gravity, curvature, and degree of roundness were assessed and analysed from images using elliptic Fourier descriptors and inverse Fourier transformation. The first four principal components accounted for 88.46-92.33% of the total variance and provided a good summary of the overall data. In the case of the ejaculate with defective sperm heads the components accounted for 97.35-98.21% of variation. The study was able to quantitatively confirm that head length to width ratio, which contributed 48.63-53.48% and 71.30-73.34% to the total variance for normal and defective sperm, respectively, was the predominant determining parameter of sperm head shape. There were no statistical significant relationships between Fourier descriptors and values of sperm concentration and/or motility. PMID:20047805
High-definition Fourier transform infrared spectroscopic imaging of breast tissue
NASA Astrophysics Data System (ADS)
Leslie, L. Suzanne; Kadjacsy-Balla, Andre; Bhargava, Rohit
2015-03-01
Breast cancer diagnosis relies on staining serial sections of a biopsy in a process that can be time intensive and costly. Fourier transform infrared imaging (FT-IR) is a non-destructive, label-free chemical imaging technique that uses the vibrational structure of the biological molecules of the sample to provide contrast for images at any absorption peak in the mid-infrared. The full potential of spectroscopic imaging has been limited by the spatial resolution provided by most commercial instruments. By increasing the magnification and numerical aperture of the microscope, image pixel sizes on the order of 1.1 micron can be achieved, allowing HD FT-IR spectroscopic imaging to provide high quality images that could aid in histopathology, diagnosis, and studies of breast cancer progression.
Digital watermarking algorithm research of color images based on quaternion Fourier transform
NASA Astrophysics Data System (ADS)
An, Mali; Wang, Weijiang; Zhao, Zhen
2013-10-01
A watermarking algorithm of color images based on the quaternion Fourier Transform (QFFT) and improved quantization index algorithm (QIM) is proposed in this paper. The original image is transformed by QFFT, the watermark image is processed by compression and quantization coding, and then the processed watermark image is embedded into the components of the transformed original image. It achieves embedding and blind extraction of the watermark image. The experimental results show that the watermarking algorithm based on the improved QIM algorithm with distortion compensation achieves a good tradeoff between invisibility and robustness, and better robustness for the attacks of Gaussian noises, salt and pepper noises, JPEG compression, cropping, filtering and image enhancement than the traditional QIM algorithm.
Underwood, Kenneth J; Jones, Andrew M; Gopinath, Juliet T
2015-06-20
We present a new application of the stochastic parallel gradient descent (SPGD) algorithm to fast active phase control in a Fourier synthesis system. Pulses (4.9 ns) with an 80 MHz repetition rate are generated by feedback from a single phase-sensitive metric. Phase control is applied via fast current modulation of a tapered amplifier using an SPGD algorithm realized on a field-programmable gate array (FPGA). The waveforms are maintained by constant active feedback from the FPGA. We also discuss the extension of this technique to many more semiconductor laser emitters in a diode laser array. PMID:26193004
PHASE CORRELATION METHOD FOR THE ALIGNMENT OF TOTAL SOLAR ECLIPSE IMAGES
Druckmueller, M., E-mail: druckmuller@fme.vutbr.c [Institute of Mathematics, Faculty of Mechanical Engineering, Brno University of Technology, 616 69 Brno (Czech Republic)
2009-12-01
A modified phase correlation method, based on Fourier transform, which enables the alignment of solar coronal images taken during the total solar eclipses, is presented. The method enables the measurement of translation, rotation, and scaling factor between two images. With the application of this technique, pairs of images with different exposure times, different brightness scale, such as linear for CCD and nonlinear for images taken with photographic film, and even images from different emission lines can be aligned with sub-pixel precision.
Roland G. Wilson; Andrew D. Calway; Edward R. S. Pearson
1992-01-01
A wavelet transform specifically designed for Fourier analysis at multiple scales is described and shown to be capable of providing a local representation which is particularly well suited to segmentation problems. It is shown that, by an appropriate choice of analysis window and sampling intervals, it is possible to obtain a Fourier representation which can be computed efficiently and overcomes
Fourier transform holography with high harmonic spectra for attosecond imaging applications.
Williams, Gareth O; Gonzalez, A I; Künzel, S; Li, L; Lozano, M; Oliva, E; Iwan, B; Daboussi, S; Boutu, W; Merdji, H; Fajardo, M; Zeitoun, Ph
2015-07-01
We demonstrate a method of using a Fourier holographic technique to utilize attosecond soft x-ray pulses to image nanometer-scale objects. A discrete frequency comb of laser-generated high-order harmonics, yielding a train of attosecond pulses, has been used to record spatially and spectrally resolved images. The individual wavelengths were also combined to form a single image, albeit with lower spatial resolution, demonstrating the applicability of the method to using isolated attosecond pulses with continuous bandwidths. PMID:26125403
NASA Astrophysics Data System (ADS)
Acosta, R. I.; Gross, K. C.; Perram, G. P.
2012-03-01
New measurement techniques to study continuous wave (CW) laser-material interactions are emerging with the ability to monitor the evolving, spatial distribution of the state of the surface-gas boundary layer. A qualitative analysis of gas phase combustion plumes above the surface of laser irradiated fiberglass composites is developed from fast framing hyperspectral imagery observations. An imaging Fourier Transform Spectrometer (IFTS) operating in the mid-infrared (MWIR) with high framing rate has recently been developed at the Air Force Institute of Technology (AFIT) in collaboration with Telops Inc. A 320 x 256 indium antimonide (InSb) focal plane array with spectral response from 1.5 - 5.5 ?m is mated with a Michelson interferometer to achieve spectral resolutions as high as 0.25 cm-1. The very fast 16- tap InSb array frames at 1.9 kHz for the full 320 x 256 frame size. The single pixel field of view of 0.3 mrad provides a spatial resolution of 1 mm at the minimum focal distance of 3 m. Painted and unpainted fiberglass composites are irradiated with a 1064 nm CW Nd:YAG laser for 60 s at 100 W in air at atmospheric pressure. Selective emission in the region of 2100 - 3200 cm-1 is readily evident and is used to develop a time-dependent spatial map of both temperature and plume constituents. The time evolution of gas phase combustion products such as CO and CO2 molecules are monitored, with a spectral resolution of 2 cm-1. High-speed imagery is obtained using a low-pass filter for the interferograms, illustrating significant turbulent behavior during laser irradiation. Spatial brightness temperature maps exceed 600 K. Spatial variation in the ratio of [CO2]/[CO] indicates an interplay between heterogeneous and homogeneous kinetics.
Fourier-domain mode delay measurement for multimode fibers using phase detection
NASA Astrophysics Data System (ADS)
Kim, Chan-Young; Ahn, Tae-Jung
2015-06-01
We have proposed a powerful method based on a phase detection reflectometric technique to solve the difficulty of the small signal discrimination in the amplitude-detection method for differential modal delay measurement of multimode optical fibers (MMFs). The phase is radically shifted to ? at the time delay positions among the excited modes even when the amplitudes of the peaks cannot be distinguished with the noise level. The modal dispersion of the MMF under test can be simply determined by choosing the time delay in the last phase shift in the Fourier domain. In addition, we confirmed that the phase-sensitive interferometric measurement does not need to scramble the excited modes in the fiber. We subsequently conclude that a portable modal dispersion or mode analysis equipment can be developed by using the phase-detection intermodal interferometric technique proposed here.
High-SNR static Fourier-transform imaging spectrometer based on differential structure
NASA Astrophysics Data System (ADS)
Jin, Peng; Zhu, Shuaishuai; Zhang, Yu; Lin, Jie
2015-03-01
Fourier-transform imaging spectrometers are rapidly developed due to their extensive use in industrial monitoring, target detection, and chemical identification. Static Fourier-transform imaging spectrometer (SFIS) containing a birefringent interferometer is one of the most popular directions due to its inherent robustness. However, the SFIS suffers from its low achievable signal-to-noise ratio (SNR) because of the restriction of incident angle. Meanwhile, in applications, the SNR is perhaps the most important factor to determine the usefulness of an instrument. In this paper, we report here a Static Fourier-transform imaging spectrometer based on differential structure (SFIS-DS) in the 400-800nm wavelength range with a high SNR. As in electronic system, the differential structure can double optical efficiency and strongly restrain common mode error in the SFIS-DS. And the differential structure described here is also available for any instruments containing a birefringent interferometer. However, the drawback of the SFIS-DS is that the two images obtained by the two differential channels need precise registration which can be overcome by a sub-pixel spatial registration algorithm. The experimental results indicate the SFIS-DS can increase the SNR by no less than 40%.
Paris-Sud XI, Université de
approches aux images couleur n'est pas directe car les images ne sont plus définies comme des fonctions de R images couleur : les GCFD3 José Mennesson Christophe Saint-Jean Laurent Mascarilla Laboratoire MIA transformée de Fourier, descripteur, algèbre de Clifford, images couleur, reconnaissance de formes Abstract
W. F. Schlotter; J. Luening; R. Rick; K. Chen; A. Scherz; S. Eisebitt; C. M. Guenther; W. Eberhardt; O. Hellwig; J. Stohr
2009-01-01
Panoramic full-field imaging is demonstrated by applying spatial multiplexing to Fourier transform holography. Multiple object and reference waves extend the effective field of view for lensless imaging without compromising the spatial resolution. In this way, local regions of interest distributed throughout a sample can be simultaneously imaged with high spatial resolution. A method is proposed for capturing multiple ultrafast images
NASA Technical Reports Server (NTRS)
Menenti, M.; Azzali, S.; Verhoef, W.; Van Swol, R.
1993-01-01
Examples are presented of applications of a fast Fourier transform algorithm to analyze time series of images of Normalized Difference Vegetation Index values. The results obtained for a case study on Zambia indicated that differences in vegetation development among map units of an existing agroclimatic map were not significant, while reliable differences were observed among the map units obtained using the Fourier analysis.
Metrology for an imaging Fourier transform spectrometer working in the far-UV (IFTSUV)
NASA Astrophysics Data System (ADS)
Ruiz de Galarreta Fanjul, C.; Philippon, A.; Vial, J.-C.; Maillard, J.-P.; Appourchaux, T.
2011-10-01
Imaging Fourier Transform Spectrometer working in the far UV (IFTSUV) may be the technical solution to answer many unsolved problems concerning the physics of the solar outer atmosphere. The VUV domain highly constrains the instruments design and performances as it demands a high optics surface quality and an accurate metrology to preserve IFTSUV spectral precision and Signal to Noise Ratio (SNR). We present the advancements on the specification of a metrology system, meeting the predicted performance requirements of an IFTSUV.
Scot S. Olivier; John S. Werner; Robert J. Zawadzki; Sophie P. Laut; Steven M. Jones
2010-01-01
This invention permits retinal images to be acquired at high speed and with unprecedented resolution in three dimensions (4.times.4.times.6 .mu.m). The instrument achieves high lateral resolution by using adaptive optics to correct optical aberrations of the human eye in real time. High axial resolution and high speed are made possible by the use of Fourier-domain optical coherence tomography. Using this
Color image encryption based on fractional Fourier transforms and pixel scrambling technique
NASA Astrophysics Data System (ADS)
Zhao, Jianlin; Lu, Hongqiang; Fan, Qi
2007-01-01
Color image encryption based on fractional Fourier transform (FRT) and pixel scrambling technique is presented in this paper. In general, color (RGB) image cannot be directly encrypted using a traditional setup for optical information processing, because which is only adapted to process two-dimensional gray image. In the proposed method, a three-dimensional RGB image is decomposed to three two-dimensional gray images (R, G and B values of the color image), and the encryption operation will be done on each two-dimensional gray image, then the encoded color image is available by composing the three two-dimensional encrypted images. The decryption process is an inverse of the encryption. The optical encrypting systems based on the presented method is proposed and simulated. Some results of computer simulation are presented to verify the flexibility and the reliability of this method. The quality of decrypted images would be debased with the difference of the fractional order. The frustrated decryption of monochromic image will affect the color of decrypted image. At the end of this paper, an all-optical and photoelectric encryption/decryption systems solution are presented, and the principle of selecting optical devices are also given.
Fourier transform-based iterative method for differential phase-contrast computed tomography
Wang, Ge
for soft tissues at hard x-ray energy levels. By contrast, the x-ray phase shift cross section is about one thousand times larger than that of x-ray attenuation for soft tissues over the di- agnostic energy range an x-ray Talbot interferometer for phase imaging, which consisted of a phase transmission grating
Choi, Heejin; Wadduwage, Dushan; Matsudaira, Paul T.; So, Peter T.C.
2014-01-01
A depth resolved hyperspectral imaging spectrometer can provide depth resolved imaging both in the spatial and the spectral domain. Images acquired through a standard imaging Fourier transform spectrometer do not have the depth-resolution. By post processing the spectral cubes (x, y, ?) obtained through a Sagnac interferometer under uniform illumination and structured illumination, spectrally resolved images with depth resolution can be recovered using structured light illumination algorithms such as the HiLo method. The proposed scheme is validated with in vitro specimens including fluorescent solution and fluorescent beads with known spectra. The system is further demonstrated in quantifying spectra from 3D resolved features in biological specimens. The system has demonstrated depth resolution of 1.8 ?m and spectral resolution of 7 nm respectively. PMID:25360367
Perfusion and ventilation filters for Fourier-decomposition MR lung imaging.
Wujcicki, Artur; Corteville, Dominique; Materka, Andrzej; Schad, Lothar R
2015-03-01
MR imaging without the use of contrast agents has recently been used for creating perfusion and ventilation functional lung images. The technique incorporates frequency- or wavelet-domain filters to separate the MR signal components. This paper presents a new, subject-adaptive algorithm for perfusion and ventilation filters design. The proposed algorithm uses a lung signal model for separation of the signal components in the frequency domain. Non-stationary lung signals are handled by a short time Fourier transform. This method was applied to sets of 192 and 90 co-registered non-contrast MR lung images measured for five healthy subjects at the rate of 3,33 images per second, using different slice thicknesses. In each case, the resulted perfusion and ventilation images showed a smaller amount of mutual information, when compared to those obtained using the known lowpass/highpass filter approach. PMID:25466452
High-resolution Fourier-transform infrared chemical imaging with multiple synchrotron beams
Nasse, Michael J; Walsh, Michael J; Mattson, Eric C; Reininger, Ruben; Kajdacsy-Balla, André; Macias, Virgilia; Bhargava, Rohit; Hirschmugl, Carol J
2013-01-01
Conventional Fourier-transform infrared (FTIR) microspectroscopic systems are limited by an inevitable trade-off between spatial resolution, acquisition time, signal-to-noise ratio (SNR) and sample coverage. We present an FTIR imaging approach that substantially extends current capabilities by combining multiple synchrotron beams with wide-field detection. This advance allows truly diffraction-limited high-resolution imaging over the entire mid-infrared spectrum with high chemical sensitivity and fast acquisition speed while maintaining high-quality SNR. PMID:21423192
NASA Astrophysics Data System (ADS)
Zhang, Yizhuo; Situ, Guohai; Pedrini, Giancarlo; Wang, Dayong; Javidi, Bahram; Osten, Wolfgang
2013-01-01
We propose a short-coherence lensless Fourier-transform digital holography for imaging through scattering media. The technique utilizes a low-power cw diode laser with short temporal coherence and enables the selection of the early-arriving photons through a diffusive medium by interfering with a spherical reference beam from the same source. An averaging technique is introduced to extract the weak signal from strong background noise. The proposed technique is verified using both theoretical analysis and experimental demonstration by imaging an object through a 3-mm-thick chicken breast tissue.
Olivier, Scot S. (Livermore, CA); Werner, John S. (Davis, CA); Zawadzki, Robert J. (Sacramento, CA); Laut, Sophie P. (Pasedena, CA); Jones, Steven M. (Livermore, CA)
2010-09-07
This invention permits retinal images to be acquired at high speed and with unprecedented resolution in three dimensions (4.times.4.times.6 .mu.m). The instrument achieves high lateral resolution by using adaptive optics to correct optical aberrations of the human eye in real time. High axial resolution and high speed are made possible by the use of Fourier-domain optical coherence tomography. Using this system, we have demonstrated the ability to image microscopic blood vessels and the cone photoreceptor mosaic.
NASA Astrophysics Data System (ADS)
Acosta, Roberto I.
The high-energy laser (HEL) lethality community needs for enhanced laser weapons systems requires a better understanding of a wide variety of emerging threats. In order to reduce the dimensionality of laser-materials interaction it is necessary to develop novel predictive capabilities of these events. The objective is to better understand the fundamentals of laser lethality testing by developing empirical models from hyperspectral imagery, enabling a robust library of experiments for vulnerability assessments. Emissive plumes from laser irradiated fiberglass reinforced polymers (FRP), poly(methyl methacrylate) (PMMA) and porous graphite targets were investigated primarily using a mid-wave infrared (MWIR) imaging Fourier transform spectrometer (FTS). Polymer and graphite targets were irradiated with a continuous wave (cw) fiber lasers. Data was acquired with a spectral resolution of 2 cm-1 and spatial resolution as high as 0.52 mm2 per pixel. Strong emission from H2O, CO, CO2 and hydrocarbons were observed in the MWIR between 1900-4000 cm-1. A single-layer radiative transfer model was developed to estimate spatial maps of temperature and column densities of CO and CO2 from the hyperspectral imagery of the boundary layer plume. The spectral model was used to compute the absorption cross sections of CO and CO2, using spectral line parameters from the high temperature extension of the HITRAN. Also, spatial maps of gas-phase temperature and methyl methacrylate (MMA) concentration were developed from laser irradiated carbon black-pigmented PMMA at irradiances of 4-22 W/cm2. Global kinetics interplay between heterogeneous and homogeneous combustion kinetics are shown from experimental observations at high spatial resolutions. Overall the boundary layer profile at steady-state is consistent with CO being mainly produced at the surface by heterogeneous reactions followed by a rapid homogeneous combustion in the boundary layer towards buoyancy.
Field experiment performance of the receiver elements for a Fourier telescopy imaging system
NASA Astrophysics Data System (ADS)
Mathis, J.; Stapp, J.; Cuellar, E. L.; Cooper, J.; Morris, A.; Fairchild, P.; Hult, Dane; Koski, Katrina; Ramzel, Lee; Thornton, Marcia A.
2005-08-01
Fourier telescopy (FT) is an active imaging technique that is a candidate for high resolution imaging systems which can be used to obtain satellite images out to geosynchronous target ranges. Fourier telescopy uses multiple beams that illuminate the target with a fringe pattern that sweeps across it due to a set frequency difference between beams. In this way the target spatial frequency components are encoded in the temporal signal that is reflected from the target. The FT receiver can then be composed of a large area "light bucket" collector, since only the integrated temporal signal is necessary to reconstruct the target image. The GEO Light Imaging National Testbed (GLINT) system was previously designed to obtain satellite images at geosynchronous ranges by using this technique. The "light bucket" receiver was designed use forty heliostats, each having a collection area of ten meters square, and composed of a 16 x 16 grid of two foot square mirrors. The heliostats would redirect the return light from the target onto a large spherical concentrator array composed of hexagonal mirror segments. This concentrator would then focus the return light onto a photomultiplier tube (PMT) detector. The FT Field experiment presented in this paper uses one 10-meter square heliostat and a single PMT, plus a scaled down secondary array to provide the optical elements of the receiver for the FT field experiment. In this paper, we will describe the performance characteristics of the heliostat, secondary, and PMT detector. Performance characteristics include optical wavefront, alignment, and alignment stability of the optical elements. Finally, results will be presented after the receiver was integrated with a transmitter system that provided the modulated FT signal from various targets. Image reconstructions will show that even using low quality "Light bucket" receiver optics and a 1.5 km horizontal path through the atmosphere, the modulated signal can still produce good image quality of the targets. Image reconstruction will also be presented for different SNR values in the received signal.
Dynamic range improvement in NMR imaging using phase scrambling
NASA Astrophysics Data System (ADS)
Maudsley, A. A.
Data collection efficiency in NMR imaging is impaired if the dynamic range of the receiver system is limited in comparison with that of the observed signal. This situation may occur in high-resolution proton imaging of large objects at high magnetic field strengths. The efficiency with which information is received can be increased by reducing the peak amplitude of the spin response by varying the phase distribution of the excited spins. This phase scrambling technique may be implemented using tailored RF excitation or by dephasing using nonlinear magnetic field gradients and can be applied in all dimensions of an acquired data set, providing a significant reduction in the dynamic range requirements of the detection electronics. Experimental results using 2D Fourier imaging have obtained up to 25 dB reduction in peak signal intensities. Image signal-to-noise ratios improved up to a factor of 6, with actual values dependent on experimental conditions. Simulation studies show that computational noise introduced during Fourier transformation is significantly reduced when phase scrambling is employed.
Fourier-phase analysis of the orbiting bright-spot model for AGN variability
V. Karas
1997-01-13
Fourier power spectra and phases of a signal from a large number of radiating sources orbiting around a black hole are investigated. It is assumed that the individual sources (bright spots) are located in an accretion disc and their lifetime exceeds the corresponding orbital period. This model is relevant for the short-time X-ray variability of active galactic nuclei. Previous works on this subject were mostly concentrated on temporal characteristics and power spectra of observed light curves. In our present contribution, Fourier phases are brought into consideration and studied systematically for a broad range of input parameters. In particular, conditions for the phase coherence are discussed. It is shown that one can discriminate between the two classes of models which are currently under consideration--orbital motion of a large number of sources versus short-lived independent flares--although parameters of the model are not completely arbitrary. It is also shown that predicted power spectra depend rather strongly on the spot distribution across the disk surface. We conclude that the orbital motion of the spots cannot be the only reason for the source fluctuations, but it certainly influences observational properties of the source intrinsic variability.
Hongyan Li; Liyun Zhong; Zhijian Ma; Xiaoxu Lu
2011-01-01
In on-axis lensless Fourier phase-shifting synthetic aperture digital holography, to compose all of the phase-shifting sub-holograms to a large synthetic aperture digital hologram effectively, firstly, the cross-correlation algorithm of the object waves is presented to correct the joint misplacement of the sub-holograms. Secondly, to make the phase-shifting synchronization matching of different sequence phase-shifting holograms, the cross-correlation algorithm of the phase-shifting
In-vivo human corneal nerve imaging using Fourier-domain OCT
NASA Astrophysics Data System (ADS)
Shin, Jun Geun; Lee, Byeong Ha; Eom, Tae Joong; Hwang, Ho Sik
2015-03-01
We have imaged human corneal nerve bundles by using real-time Fourier-domain OCT (FD-OCT). Corneal nerves contribute to the maintenance of healthy ocular surface owing to their trophic influences on the corneal epithelium. The FD-OCT system was based on a swept laser of a 50 kHz sweeping rate and 1.31 ?m center wavelength. At the area including sclera, limbus, and cornea, we could successfully get the in-vivo tomograms of the corneal nerve bundles. The scan range was 5 x 5mm. In this study, the A-scan images in each B-scan were realigned to have a flat air-surface boundary in the final B-scan image. With this effort, we could align corneal nerve bundle in a same depth and get the 3D image showing the branched and threadlike corneal nerve bundles.
Study on the depth of focus of lensless Fourier transform digital holographic imaging system
NASA Astrophysics Data System (ADS)
Wang, Huaying; Qin, Aili; Wang, Yi
2009-11-01
Based on the principle of digital holography and the criterion of the depth of focus of coherent lens imaging system, the depth of focus (DOF) of off-axis lensless Fourier transform digital holographic system is analyzed. The DOF expressions of digital holographic systems with symmetrical and unsymmetrical offset of reference point sources are deduced and presented. By using a minute vertical bar object the corresponding simulations are performed. The recorded holograms are reconstructed digitally at the focal plane and its vicinity. The results verified the correctness of the analysis and show that the DOF of digital holographic imaging system is not only dependent on the optical wavelength and the recording numerical aperture but also strongly on the optical setup, which indicates that the DOF of digital holographic image system isn't the same as that of the coherent lens imaging system.
MightySat II.1 Fourier-transform hyperspectral imager payload performance
NASA Astrophysics Data System (ADS)
Otten, Leonard J.; Sellar, R. Glenn; Rafert, J. Bruce
1995-12-01
Using a new microsat called MightySat II as a platform, Kestrel Corporation is designing and building the first Fourier transform hyperspectral imager (FTHSI) to be operated from a spacecraft. This payload will also be the first to fly on the Phillips Laboratory MightySat II spacecraft series, a new, innovative approach, to affordable space testing of high risk, high payoff technologies. Performance enhancements offered by the Fourier transform approach have shown it to be one of the more promising spaceborne hyperspectral concepts. Simulations of the payload's performance have shown that the instrument is capable of separating a wide range of subtle spectral differences. Variations in the return from the Georges Bank and shoals are discernible and various types of coastal grasses (sea oats and spartina) can be isolated against a sand background.
NASA Astrophysics Data System (ADS)
Joenathan, Charles; Bernal, Ashley; Sirohi, Rajpal S.
2013-08-01
Previously, we reported a simple method to obtain lateral shear in both the x- and y-directions using a multiplexing technique. The phase data was extracted using the inherent spatial carrier fringes formed due to the tilt in the two sheared beams. In this article, we report that an error in phase map is introduced when the band-pass-filtered Fourier transform (FT) spectrum is not centered prior to performing the inverse FT to obtain the phase. We also found that intentionally introducing aberrations when capturing dynamic fluctuations in the wave front, resulted in controlling the spread of the Fourier spectrum.
SITELLE: a wide-field imaging Fourier transform spectrometer for the Canada-France-Hawaii Telescope
NASA Astrophysics Data System (ADS)
Drissen, L.; Bernier, A.-P.; Rousseau-Nepton, L.; Alarie, A.; Robert, C.; Joncas, G.; Thibault, S.; Grandmont, F.
2010-07-01
We describe the concept of a new instrument for the Canada-France-Hawaii telescope (CFHT), SITELLE (Spectromètre Imageur à Transformée de Fourier pour l'Etude en Long et en Large de raies d'Emission), as well as a science case and a technical study of its preliminary design. SITELLE will be an imaging Fourier transform spectrometer capable of obtaining the visible (350 nm - 950 nm) spectrum of every source of light in a field of view of 15 arcminutes, with 100% spatial coverage and a spectral resolution ranging from R = 1 (deep panchromatic image) to R = 104 (for gas dynamics). SITELLE will cover a field of view 100 to 1000 times larger than traditional integral field spectrographs, such as GMOS-IFU on Gemini or the future MUSE on the VLT. It is a legacy from BEAR, the first imaging FTS installed on the CFHT and the direct successor of SpIOMM, a similar instrument attached to the 1.6-m telescope of the Observatoire du Mont-Mégantic in Québec. SITELLE will be used to study the structure and kinematics of HII regions and ejecta around evolved stars in the Milky Way, emission-line stars in clusters, abundances in nearby gas-rich galaxies, and the star formation rate in distant galaxies.
Tsurui, H; Nishimura, H; Hattori, S; Hirose, S; Okumura, K; Shirai, T
2000-05-01
Seven-color analyses of immunofluorescence-stained tissue samples were accomplished using Fourier spectroscopy-based hyperspectral imaging and singular value decomposition. This system consists of a combination of seven fluorescent dyes, three filtersets, an epifluorescence microscope, a spectral imaging system, a computer for data acquisition, and data analysis software. The spectra of all pixels in a multicolor image were taken simultaneously using a Sagnac type interferometer. The spectra were deconvolved to estimate the contribution of each component dye, and individual dye images were constructed based on the intensities of assigned signals. To obtain mixed spectra, three filter sets, i.e., Bl, Gr, and Rd for Alexa488 and Alexa532, for Alexa546, Alexa568, and Alexa594, and for Cy5 and Cy5.5, respectively, were used for simultaneous excitation of two or three dyes. These fluorophores have considerable spectral overlap which precludes their separation by conventional analysis. We resolved their relative contributions to the fluorescent signal by a method involving linear unmixing based on singular value decomposition of the matrices consisting of dye spectra. Analyses of mouse thymic tissues stained with seven different fluorescent dyes provided clear independent images, and any combination of two or three individual dye images could be used for constructing multicolor images. PMID:10769049
NASA Astrophysics Data System (ADS)
Adler, Desmond C.; Huber, Robert; Fujimoto, James G.
2007-02-01
Phase sensitive optical coherence tomography (OCT) can be used to obtain sub-nanometer displacement measurements of biological and non-biological samples. This technique has many applications, including detection of small amplitude surface motion, and high axial resolution OCT phase microscopy. Doppler OCT is another type of phase sensitive imaging, where differential phase measurements are used to detect fluid flow in biological specimens. For all types of phase sensitive OCT, a light source with low phase noise is required in order to provide good displacement sensitivity. High speed imaging is also necessary in order to minimize motion artifacts and enable the detection of fast transient events. In this manuscript, buffered Fourier Domain Mode Locked (FDML) lasers are demonstrated for ultrahigh-speed phase sensitive OCT detection. The lasers are operated at sweep speeds of 42, 117, and 370 kHz, and displacement sensitivities of 39, 52, and 102 pm are achieved, respectively. These displacement sensitivities are comparable to spectrometer-based phase sensitive OCT systems, but acquisition speeds 1.4 - 13x faster are possible using buffered FDML lasers. An additional factor of ?2 improvement in noise performance is observed for differential phase measurements, which has important implications for Doppler OCT. Dynamic measurements of rapid, small-amplitude piezoelectric transducer motion are demonstrated. In general, buffered FDML lasers provide excellent displacement sensitivities at extremely high sweep speeds for phase sensitive OCT measurements.
LEEM image phase contrast of MnAs stripes.
Pang, A B; Pavlovska, A; Däweritz, L; Locatelli, A; Bauer, E; Altman, M S
2013-07-01
Low energy electron microscopy (LEEM) imaging of strained MnAs layers epitaxially grown on GaAs(001) reveals striped contrast features that become more pronounced and vary systematically in width with increasing defocus, but that are completely absent in focus. Weaker subsidiary fringe-like features are observed along the stripe lengths, while asymmetric contrast reversal occurs between under-focus and over-focus conditions. A Fourier optics calculation is performed that demonstrates that these unusual observations can be attributed to a phase contrast mechanism between the hexagonal ? phase and orthorhombic ? phase regions of the MnAs film, which self-organize into a periodic stripe array with ridge-groove morphology. The unequal widths of the ? and ? phase regions are determined accurately from the through focus series, while the height variation in this system can also be determined in principle from the energy dependence of contrast. PMID:23571091
Schlotter, William F; Lüning, Jan; Rick, Ramon; Chen, Kang; Scherz, Andreas; Eisebitt, Stefan; Günther, Christian M; Eberhardt, Wolfgang; Hellwig, Olav; Stöhr, Joachim
2007-11-01
Panoramic full-field imaging is demonstrated by applying spatial multiplexing to Fourier transform holography. Multiple object and reference waves extend the effective field of view for lensless imaging without compromising the spatial resolution. In this way, local regions of interest distributed throughout a sample can be simultaneously imaged with high spatial resolution. A method is proposed for capturing multiple ultrafast images of a sample with a single x-ray pulse. PMID:17975613
Schlotter, W.F.; /Stanford U., Appl. Phys. Dept. /SLAC, SSRL; Luening, J.; /Paris, Lab Chim. Quantique /SOLEIL, Saint-Aubin /BESSY, Berlin; Rick, R.; Chen, K.; /Stanford U., Appl. Phys. Dept. /SLAC, SSRL; Scherz, A.; /SLAC, SSRL; Eisebitt, S.; Guenther, C.M.; Eberhardt, W.; /BESSY, Berlin; Hellwig, O.; /Hitachi Global Stor. Tech., San Jose; Stohr, J.; /SLAC, SSRL
2009-04-29
Panoramic full-field imaging is demonstrated by applying spatial multiplexing to Fourier transform holography. Multiple object and reference waves extend the effective field of view for lensless imaging without compromising the spatial resolution. In this way, local regions of interest distributed throughout a sample can be simultaneously imaged with high spatial resolution. A method is proposed for capturing multiple ultrafast images of a sample with a single x-ray pulse.
NASA Technical Reports Server (NTRS)
Alfano, Robert R. (Inventor); Cai, Wei (Inventor)
2007-01-01
A reconstruction technique for reducing computation burden in the 3D image processes, wherein the reconstruction procedure comprises an inverse and a forward model. The inverse model uses a hybrid dual Fourier algorithm that combines a 2D Fourier inversion with a 1D matrix inversion to thereby provide high-speed inverse computations. The inverse algorithm uses a hybrid transfer to provide fast Fourier inversion for data of multiple sources and multiple detectors. The forward model is based on an analytical cumulant solution of a radiative transfer equation. The accurate analytical form of the solution to the radiative transfer equation provides an efficient formalism for fast computation of the forward model.
NASA Astrophysics Data System (ADS)
Ricci, Camilla; Chan, K. L. Andrew; Kazarian, Sergei G.
2006-09-01
Conventional FTIR spectroscopy and microscopy has been widely used in forensic science. New opportunities exist to obtain rapid chemical images and to enhance the sensitivity of detection of trace materials using attenuated total reflection (ATR) Fourier transform infrared (FTIR) spectroscopy coupled with a focal-plane array (FPA) detector. In this work, the sensitivity of ATR-FTIR spectroscopic imaging using three different kinds of ATR crystals (Ge coupled with an infrared microscope, ZnSe and diamond) and resulting in three different optical arrangements for the detection of model drug particles is discussed. Model systems of ibuprofen and paracetamol particles having a size below 32 micrometers have been prepared by sieving. The sensitivity level in the three different approaches has been compared and it has been found that both micro and macro-ATR imaging methods have proven to be a promising techniques for the identification of concealed drug particles. To demonstrate the power and applicability of FTIR chemical imaging to forensic research, various examples are discussed. This includes investigation of the changes of chemical nature of latent fingerprint residue under controlled conditions of humidity and temperature studied by ATR-FTIR imaging. This study demonstrates the potential of spectroscopic imaging for visualizing the chemical changes of fingerprints.
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.
Yang, Tiantong; He, Guanglong; Zhang, Xiang; Chang, Lin; Zhang, Haidong; Ripple, Mary G; Fowler, David R; Li, Ling
2014-01-01
The objective of this study was to evaluate the application of Fourier transform infrared (FTIR) spectroscopy for detecting diffuse axonal injury (DAI) in a mouse model. Brain tissues from DAI mouse model were prepared with H&E, silver, and ?-amyloid precursor protein (?-APP) immunohistochemistry stains and were also studied with FTIR. The infrared spectrum images showed high absorption of amide II in the subcortical white matter of the experimental mouse brain, while there was no obvious expression of amide II in the control mouse brain. The areas with high absorption of amide II were in the same distribution as the DAI region confirmed by the silver and ?-APP studies. The result suggests that high absorption of amide II correlates with axonal injury. The use of FTIR imaging allows the biochemical changes associated with DAI pathologies to be detected in the tissues, thus providing an important adjunct method to the current conventional pathological diagnostic techniques. PMID:24147828
Tensor representation of color images and fast 2D quaternion discrete Fourier transform
NASA Astrophysics Data System (ADS)
Grigoryan, Artyom M.; Agaian, Sos S.
2015-03-01
In this paper, a general, efficient, split algorithm to compute the two-dimensional quaternion discrete Fourier transform (2-D QDFT), by using the special partitioning in the frequency domain, is introduced. The partition determines an effective transformation, or color image representation in the form of 1-D quaternion signals which allow for splitting the N × M-point 2-D QDFT into a set of 1-D QDFTs. Comparative estimates revealing the efficiency of the proposed algorithms with respect to the known ones are given. In particular, a proposed method of calculating the 2r × 2r -point 2-D QDFT uses 18N2 less multiplications than the well-known column-row method and method of calculation based on the symplectic decomposition. The proposed algorithm is simple to apply and design, which makes it very practical in color image processing in the frequency domain.
NASA Astrophysics Data System (ADS)
Landry, Jean-Thomas; Grandmont, Frédéric
2006-06-01
This paper presents an overview of a step scanning mechanism employing a flexure stage coupled with a dynamically aligned mirror used in the SpIOMM (Spectrometre Imageur de l'Observatoire du Mont Megantic) instrument, an Imaging Fourier Transform Spectrometer (IFTS) concept for ground based telescopes produced in collaboration with ABB and Universite Laval. This instrument can acquire spectra of variable resolutions up to R = ?/?? = 10 000 from the near UV to the near IR (350 nm to 900 nm). It is designed to fit the f/8 focus of the Mont Megantic (Quebec, Canada) 1.6m optical telescope. The innovative aspect of this instrument compared to other imaging spectrometers is the spatial coverage. The FOV covers spans of 12 arc minutes in diameter with a pixel sampling of 0.55 arc seconds. Hence spectra of more than a million scene elements are acquired at each measurement.
Double image encryption using double pixel scrambling and random phase encoding
NASA Astrophysics Data System (ADS)
Zhong, Zhi; Chang, Jie; Shan, Mingguang; Hao, Bengong
2012-03-01
A novel double image encryption method is proposed by utilizing double pixel scrambling technique and random fractional Fourier domain encoding. One of the two original images is encoded into the phase of a complex signal after being scrambled by one matrix, and the other original image encoded into its amplitude after being scrambled by another matrix. The complex signal is then encrypted into stationary white noise by utilizing double random phase encoding in fractional Fourier domain. By applying the correct keys with fractional orders, the random phase masks and the pixel scrambling operation, the two original images can be retrieved without cross-talk. Numerical simulations have been done to prove the validity and the security of the proposed encryption method.
NASA Astrophysics Data System (ADS)
Hosono, Satsuki; Qi, Wei; Sato, Shun; Suzuki, Yo; Fujiwara, Masaru; Hiramatsu, Hiroyuki; Suzuki, Satoru; Abeygunawardhana, P. K. W.; Wada, Kenji; Nishiyama, Akira; Ishimaru, Ichiro
2015-03-01
For simultaneous measurement of multi-components on-site like factories, the ultra-compact (diameter: 9[mm], length: 45[mm], weight: 200[g]) one-shot ATR (Attenuated Total Reflection) Fourier spectroscopic imager was proposed. Because the proposed one-shot Fourier spectroscopic imaging is based on spatial-phase-shift interferometer, interferograms could be obtained with simple optical configurations. We introduced the transmission-type relativeinclined phase-shifter, that was constructed with a cuboid prism and a wedge prism, onto the optical Fourier transform plane of infinity corrected optical systems. And also, small light-sources and cameras in the mid-infrared light region, whose size are several millimeter on a side, are essential components for the ultra-compact spectroscopic configuration. We selected the Graphite light source (light source area: 1.7×1.7[mm], maker: Hawkeye technologies) whose radiation factor was high. Fortunately, in these days we could apply the cost-effective 2-dimensional light receiving device for smartphone (e.g. product name: LEPTON, maker: FLIR, price: around 400USD). In the case of alcoholic drinks factory, conventionally workers measure glucose and ethanol concentrations by bringing liquid solution back to laboratories every day. The high portable spectroscopy will make it possible to measure multi-components simultaneously on manufacturing scene. But we found experimentally that absorption spectrum of glucose and water and ethanol were overlapped each other in near infrared light region. But for mid-infrared light region, we could distinguish specific absorption peaks of glucose (@10.5[?m]) and ethanol (@11.5[?m]) independently from water absorption. We obtained standard curve between absorption (@9.6[?m]) and ethanol concentration with high correlation coefficient 0.98 successfully by ATR imaging-type 2-dimensional Fourier spectroscopy (wavelength resolution: 0.057[?m]) with the graphite light source (maker: Hawkeye technologies, type: IR-75).
Optical design of a static LWIR Fourier-transform imaging spectrometer with high throughput
NASA Astrophysics Data System (ADS)
Wang, Hai-yang; Fu, Yan-peng; Zheng, Wei-jian; Liao, Ning-fang; Jin, Wei-qi
2013-08-01
A LWIR Fourier-transform imaging spectrometer based on the static Michelson interferometer with high throughput is presented. Advantages and disadvantages of some common structures of imaging spectrometer are analyzed. Some selection of optimum configurations for imaging spectrometer is proceeded. The interferogram is acquired over the whole field of the camera while the scene of interest scans the path difference range, and vignetting should be strongly limited while keeping the size of the interferometer as small as possible for manufacturability and practicability reasons. The key point is to put the entrance pupil of the imaging lens inside the interferometer. The design of optical system is proposed. The field of view(FOV) is 10°.The operating wavelength range is from 8 to 12?m, F number is 2 and the working temperature range is -20°C?40°C. Optical system with 100% cold shield efficiency is good adaptability to wide environment temperature change. The spectrometer system has low utilization of solar energy in the infrared band, so to ensure its transmittance, and it is necessary to use a small amount of lenses as possible, so here the method of the active electromechanical athermalisation just uses four lenses in the system. Modulation transfer function (MTF), aberrant and distortion etc of optical system are analyzed. The results show that an excellent performance and image performance are obtained despite the simple structure.
Kang, Jin U.; Huang, Yong; Zhang, Kang; Ibrahim, Zuhaib; Cha, Jaepyeong; Lee, W. P. Andrew; Brandacher, Gerald; Gehlbach, Peter L.
2012-01-01
Abstract. The authors describe the development of an ultrafast three-dimensional (3D) optical coherence tomography (OCT) imaging system that provides real-time intraoperative video images of the surgical site to assist surgeons during microsurgical procedures. This system is based on a full-range complex conjugate free Fourier-domain OCT (FD-OCT). The system was built in a CPU-GPU heterogeneous computing architecture capable of video OCT image processing. The system displays at a maximum speed of 10??volume/s for an image volume size of 160×80×1024 (X×Y×Z) pixels. We have used this system to visualize and guide two prototypical microsurgical maneuvers: microvascular anastomosis of the rat femoral artery and ultramicrovascular isolation of the retinal arterioles of the bovine retina. Our preliminary experiments using 3D-OCT-guided microvascular anastomosis showed optimal visualization of the rat femoral artery (diameter<0.8??mm), instruments, and suture material. Real-time intraoperative guidance helped facilitate precise suture placement due to optimized views of the vessel wall during anastomosis. Using the bovine retina as a model system, we have performed “ultra microvascular” feasibility studies by guiding handheld surgical micro-instruments to isolate retinal arterioles (diameter?0.1??mm). Isolation of the microvessels was confirmed by successfully passing a suture beneath the vessel in the 3D imaging environment. PMID:23224164
Lebensohn, Ricardo A [Los Alamos National Laboratory; Lee, Sukbin [CMU; Rollett, Anthony D [CMU
2009-01-01
A viscoplastic approach using the Fast Fourier Transform (FFT) method for obtaining local mechanical response is utilized to study microstructure-property relationships in composite materials. Specifically, three-dimensional, two-phase digital materials containing isotropically coarsened particles surrounded by a matrix phase, generated through a Kinetic Monte Carlo Potts model for Ostwald ripening, are used as instantiations in order to calculate the stress and strain rate fields under uniaxial tension. The effects of the morphology of the matrix phase, the volume fraction and the contiguity of particles, and the polycrystallinity of matrix phase, on the stress and strain rate fields under uniaxial tension are examined. It is found that the first moments of the stress and strain rate fields have a different dependence on the particle volume fraction and the particle contiguity from their second moments. The average stresses and average strain rates of both phases and of the overall composite have rather simple relationships with the particle volume fraction whereas their standard deviations vary strongly, especially when the particle volume fraction is high, and the contiguity of particles has a noticeable effect on the mechanical response. It is also found that the shape of stress distribution in the BCC hard particle phase evolves as the volume fraction of particles in the composite varies, such that it agrees with the stress field in the BCC polycrystal as the volume of particles approaches unity. Finally, it is observed that the stress and strain rate fields in the microstructures with a polycrystalline matrix are less sensitive to changes in volume fraction and contiguity of particles.
Girard, Pascal; Koenig-Robert, Roger
2011-01-01
Background Comparative studies of cognitive processes find similarities between humans and apes but also monkeys. Even high-level processes, like the ability to categorize classes of object from any natural scene under ultra-rapid time constraints, seem to be present in rhesus macaque monkeys (despite a smaller brain and the lack of language and a cultural background). An interesting and still open question concerns the degree to which the same images are treated with the same efficacy by humans and monkeys when a low level cue, the spatial frequency content, is controlled. Methodology/Principal Findings We used a set of natural images equalized in Fourier spectrum and asked whether it is still possible to categorize them as containing an animal and at what speed. One rhesus macaque monkey performed a forced-choice saccadic task with a good accuracy (67.5% and 76% for new and familiar images respectively) although performance was lower than with non-equalized images. Importantly, the minimum reaction time was still very fast (100 ms). We compared the performances of human subjects with the same setup and the same set of (new) images. Overall mean performance of humans was also lower than with original images (64% correct) but the minimum reaction time was still short (140 ms). Conclusion Performances on individual images (% correct but not reaction times) for both humans and the monkey were significantly correlated suggesting that both species use similar features to perform the task. A similar advantage for full-face images was seen for both species. The results also suggest that local low spatial frequency information could be important, a finding that fits the theory that fast categorization relies on a rapid feedforward magnocellular signal. PMID:21326600
Phase Preserving Denoising of Images Peter Kovesi
Kovesi, Peter
the statistics of the wavelet responses to the image. 1. Introduction Denoising of images is typically donePhase Preserving Denoising of Images Peter Kovesi Department of Computer Science The University denoising has become the method of choice for the denoising of images. However, despite much research
NASA Astrophysics Data System (ADS)
Cai, Weixing; Ning, Ruola; Yu, Yang; Liu, Jiangkun; Conover, David
2012-03-01
The phase stepping algorithm is commonly used for phase retrieval in grating-based differential phase-contrast (DPC) imaging, which requires multiple intensity images to compute one DPC image. It is not efficient for data acquisition, especially in the case of dynamic imaging using either DPC imaging or DPC-based come beam CT (DPC-CBCT) imaging. A Fourier transform-based approach has been developed for fringe pattern analysis in optics, and it was recently implemented into a synchrotron-based DPC tomography system. In this research, this approach is further developed for a bench-top DPC-CBCT imaging system with a hospital-grade x-ray tube. The key idea is to separate carrier fringes and object information in Fourier domain of the interferogram and to reconstruct the differentiated phase information using the object information. Only one interferogram is required for phase retrieval at a cost of spatial resolution. The fringes of moiré patterns are used as the carrier fringes, and a phantom is scanned to evaluate the approach. Various interferograms with different carrier fringe frequencies are investigated and the reconstruction image quality is evaluated in terms of contrast, noise and sharpness. The results indicated that the DPC images can be effectively retrieved using the Fourier transform-based approach and the reconstructed phase coefficient showed better contrast compared to that of attenuation-based contrast. The spatial resolution is acceptable in the phantom studies although it is not as good as the results of phase-stepping approach. The Fourier transform-based phase retrieval approach is able to greatly simplify data acquisition, to improve the temporal resolution and to make it possible for dynamic DPC-CBCT imaging. It is promising for perfusion imaging where spatial resolution is not a concern.
Hiroyoshi Iwata; Satoshi Niikura; Seiji Matsuura; Yasushi Takano; Yasuo Ukai
1998-01-01
Variation was of root shape in Japanese radish, due to genotypes, soil types and growth stages, were quantitatively evaluated\\u000a by principal components scores based on elliptic Fourier descriptors. Photographic images of sampled roots on 35mm color reversal\\u000a films were converted into digital images. After image processing, the contour of each root was expressed as chain-code and\\u000a then described by 77
High Throughput Operando Studies using Fourier Transform Infrared Imaging and Raman Spectroscopy
Li, Guosheng; Hu, Dehong; Xia, Guanguang; White, John M.; Zhang, Z. Conrad
2008-07-01
A prototype operando high throughput (OHT) reactor designed and built for catalyst screening and characterization combines Fourier transform infrared (FT-IR) imaging and Raman spectroscopy in operando conditions. Using a focal plane array (FPA) detector (HgCdTe FPA, 128×128 pixels, and 1,610 Hz frame rate) for the FT-IR imaging system, the catalyst activity and selectivity of all parallel reaction channels can be simultaneously followed. Each image dataset possesses16,384 IR spectra with a spectral range of 800 to 4000 cm-1 with an 8 cm-1 resolution. Depending on the signal-to-noise ratio, 2 to 20 seconds are needed to generate a full image of all reaction channels from a dataset. Results on reactant conversion and product selectivity are obtained from FT-IR spectral analysis. Six novel Raman probes, one for each reaction channel, were specially designed and house built at Pacific Northwest National Laboratory (PNNL), to simultaneously collect Raman spectra of the catalysts and possible reaction intermediates on the catalyst surface under operando conditions. As a model system, methanol partial oxidation reaction on silica-supported molybdenum oxide (MoO3/SiO2) catalysts has been studied under different reaction conditions to demonstrate the performance of the OHT reactor.
used transfer function analysis TFA that is based on Fourier decomposition and ii the recently proposed research 1012 , orbit re- search 13 , structural health monitoring 1417 , water wave analysis 18Nonlinear phase interaction between nonstationary signals: A comparison study of methods based
NASA Astrophysics Data System (ADS)
Drissen, L.; Alarie, A.; Martin, T.; Lagrois, D.; Rousseau-Nepton, L.; Bilodeau, A.; Robert, C.; Joncas, G.; Iglesias-Páramo, J.
2012-09-01
We present new data obtained with SpIOMM, the imaging Fourier transform spectrometer attached to the 1.6-m telescope of the Observatoire du Mont-Megantic in Québec. Recent technical and data reduction improvements have significantly increased SpIOMM's capabilities to observe fainter objects or weaker nebular lines, as well as continuum sources and absorption lines, and to increase its modulation efficiency in the near ultraviolet. To illustrate these improvements, we present data on the supernova remnant Cas A, planetary nebulae M27 and M97, the Wolf-Rayet ring nebula M1-67, spiral galaxies M63 and NGC 3344, as well as the interacting pair of galaxies Arp 84.
Science results from the imaging Fourier transform spectrometer SpIOMM
NASA Astrophysics Data System (ADS)
Drissen, L.; Bernier, A.-P.; Charlebois, M.; Brière, É.; Robert, C.; Joncas, G.; Martin, P.; Grandmont, F.
2008-07-01
SpIOMM is an imaging Fourier transform spectrometer designed to obtain the visible range (350 - 850 nm) spectrum of every light source in a circular field of view of 12 arcminutes in diameter. Attached to the 1.6-m telescope of the Observatoire du Mont Megantic in southern Quebec. We present here some results of three successful observing runs in 2007, which highlight SpIOMM's capabilities to map emission line objects over a very wide field of view and a broad spectral range. In particular, we discuss data cubes from the planetary nebula M27, the supernova remnants NGC 6992 and M1, the barred spiral galaxy NGC7479, as well as Stephan's quintet, and interacting group of galaxies.
Petter, C H; Heigl, N; Rainer, M; Bakry, R; Pallua, J; Bonn, G K; Huck, C W
2009-01-01
Fourier-transform infrared (FT-IR) based mapping and imaging is a fast emerging technology which is being increasingly applied to investigate tissues in the high-throughput mode. The high resolution close to the cellular level, the possibility to determine the bio-distribution of molecules of interest (proteins, peptides, lipids, carbohydrates) without any pre-treatment and the offer to yield molecular structure information have brought evidence that this technique allows to gain new insights in cancer pathology. Thus, several individual mainly protein and peptide cancer markers ("biomarkers") can be identified from FT-IR tissue images, enabling accurate discrimination between healthy and tumour areas. Optimal data acquisition (spatial resolution, spectral resolution, signal to noise ratio), classification, and validation are necessary to establish practical protocols that can be translated to the qualitative and quantitative clinical routine analysis. Thereby, the development of modern fast infrared imaging systems has strongly supported its acceptance in clinical histopathology. In this review, the necessity of analysis based on global cancer statistics, instrumental setups and developments, experimental state of the art are summarised and applications to investigate different kinds of cancer (e.g., prostate, breast, cervical, colon, oral cavity) are shown and discussed in detail. PMID:19149580
3D imaging of dental hard tissues with Fourier domain optical coherence tomography
NASA Astrophysics Data System (ADS)
Chen, Yueli L.; Yang, Yi; Ma, Jing; Yan, Jun; Shou, Yuanxin; Wang, Tianheng; Ramesh, Aruna; Zhao, Jing; Zhu, Quing
2011-03-01
A fiber optical coherence tomography (OCT) probe is used for three dimensional dental imaging. The probe has a lightweight miniaturized design with a size of a pen to facilitate clinic in vivo diagnostics. The probe is interfaced with a swept-source / Fourier domain optical coherence tomography at 20K axial scanning rate. The tooth samples were scanned from occlusal, buccal, lingual, mesial, and distal orientations. Three dimensional imaging covers tooth surface area up to 10 mm x 10 mm with a depth about 5 mm, where a majority of caries affection occurs. OCT image provides better resolution and contrast compared to gold standard dental radiography (X-ray). In particular, the technology is well suited for occlusal caries detection. This is complementary to X-ray as occlusal caries affection is difficult to be detected due to the X-ray projectile scan geometry. The 3D topology of occlusal surface as well as the dentin-enamel junction (DEJ) surface inside the tooth can be visualized. The lesion area appears with much stronger back scattering signal intensity.
or Zernike moments. Beside this ap- proach, SIFT (Scale-Invariant Feature Transform) descriptors are a color Fourier transform us- ing geometric algebra [1] and Generalized Fourier descrip- tors defined from-Fourier transform as defined by Batard et al. [1]. This paper is structured as follows : In the section 2
Grandidier, Jonathan
and the propagation constants are evalu- ated by Fourier imaging and analysis. Good agreements are found between of an electromagnetic wave to the free electrons of a metal, open new perspectives in optoelectronics.1,2 In the last and their associated propagation lengths. These two parameters can be optimized by adjusting the thickness
Symmetric Phase-Only Filtering in Particle-Image Velocimetry
NASA Technical Reports Server (NTRS)
Wemet, Mark P.
2008-01-01
Symmetrical phase-only filtering (SPOF) can be exploited to obtain substantial improvements in the results of data processing in particle-image velocimetry (PIV). In comparison with traditional PIV data processing, SPOF PIV data processing yields narrower and larger amplitude correlation peaks, thereby providing more-accurate velocity estimates. The higher signal-to-noise ratios associated with the higher amplitude correlation peaks afford greater robustness and reliability of processing. SPOF also affords superior performance in the presence of surface flare light and/or background light. SPOF algorithms can readily be incorporated into pre-existing algorithms used to process digitized image data in PIV, without significantly increasing processing times. A summary of PIV and traditional PIV data processing is prerequisite to a meaningful description of SPOF PIV processing. In PIV, a pulsed laser is used to illuminate a substantially planar region of a flowing fluid in which particles are entrained. An electronic camera records digital images of the particles at two instants of time. The components of velocity of the fluid in the illuminated plane can be obtained by determining the displacements of particles between the two illumination pulses. The objective in PIV data processing is to compute the particle displacements from the digital image data. In traditional PIV data processing, to which the present innovation applies, the two images are divided into a grid of subregions and the displacements determined from cross-correlations between the corresponding sub-regions in the first and second images. The cross-correlation process begins with the calculation of the Fourier transforms (or fast Fourier transforms) of the subregion portions of the images. The Fourier transforms from the corresponding subregions are multiplied, and this product is inverse Fourier transformed, yielding the cross-correlation intensity distribution. The average displacement of the particles across a subregion results in a displacement of the correlation peak from the center of the correlation plane. The velocity is then computed from the displacement of the correlation peak and the time between the recording of the two images. The process as described thus far is performed for all the subregions. The resulting set of velocities in grid cells amounts to a velocity vector map of the flow field recorded on the image plane. In traditional PIV processing, surface flare light and bright background light give rise to a large, broad correlation peak, at the center of the correlation plane, that can overwhelm the true particle- displacement correlation peak. This has made it necessary to resort to tedious image-masking and background-subtraction procedures to recover the relatively small amplitude particle-displacement correlation peak. SPOF is a variant of phase-only filtering (POF), which, in turn, is a variant of matched spatial filtering (MSF). In MSF, one projects a first image (denoted the input image) onto a second image (denoted the filter) as part of a computation to determine how much and what part of the filter is present in the input image. MSF is equivalent to cross-correlation. In POF, the frequency-domain content of the MSF filter is modified to produce a unitamplitude (phase-only) object. POF is implemented by normalizing the Fourier transform of the filter by its magnitude. The advantage of POFs is that they yield correlation peaks that are sharper and have higher signal-to-noise ratios than those obtained through traditional MSF. In the SPOF, these benefits of POF can be extended to PIV data processing. The SPOF yields even better performance than the POF approach, which is uniquely applicable to PIV type image data. In SPOF as now applied to PIV data processing, a subregion of the first image is treated as the input image and the corresponding subregion of the second image is treated as the filter. The Fourier transforms from both the firs and second- image subregions are normalized by the square roots of their respective magnitudes.
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.
Dynamic holographic method of imaging phase objects
NASA Astrophysics Data System (ADS)
Brody, Philip S.; Leavitt, Richard P.
1987-03-01
The use of real-time dynamic holography to image phase objects is described. This method uses the self-phase-conjugating phenomenon in barium titanate and a technique of incomplete aberration removal. Experiments in which dynamic holography is applied to the imaging of various objects are discussed. The equation for calculating the optical field in the half-space beyond the shifted phase plate is derived.
Potsaid, Benjamin M.
We demonstrate ultrahigh speed swept source/Fourier domain ophthalmic OCT imaging using a short cavity swept laser at 100,000 – 400,000 axial scan rates. Several design configurations illustrate tradeoffs in imaging speed, ...
Dispersion control with a Fourier-domain optical delay line in a fiber-optic imaging interferometer
Kye-Sung Lee; A. Ceyhun Akcay; Tony Delemos; Eric Clarkson; Jannick P. Rolland
2005-01-01
Recently, Fourier-domain (FD) optical delay lines (ODLs) were introduced for high-speed scanning and dispersion compensation in imaging interferometry. We investigate the effect of first- and second-order dispersion on the photocurrent signal associated with an optical coherence imaging system implemented with a single-mode fiber, a superluminescent diode centered at 950 nm +\\/- 35 nm, a FD ODL, a mirror, and a
NASA Astrophysics Data System (ADS)
Zou, Chun-bo; Hu, Bing-Liang; Li, Li-bo; Bai, Qing-Lan; Sun, Xin; Li, Ran; Yang, Jian-Feng
2014-11-01
A novel dual-band static Fourier transform imaging spectrometer was designed, which was the spatio-temporally modulated imaging Fourier transform spectrometer based on Sagnac interferometer. The approach represented a simplification and mass reduction over the traditional approach. It could obtain two-dimensional spatial images and one dimensional spectral image in two bands simultaneously. The two bands was separated through a dichroic prism and imaging in two detectors. one band was the visible and near infrared band, with the spectral range 400nm-1000nm and spectral resolution 187.5 wave numbers; the other was the short wave infrared band, with the spectral range 1000nm- 2500nm and spectral resolution 150 wave numbers. To reduce the size of the Interferometer, a high aperture compression ratio telescope system was designed before. The optical aperture was compressed to 1/10, and the volume of interferometer was reduced to 1/1000. For the convenience of engineering implementation, the telescope was composed of two no-aberration object lens: fore-lens and Collimating lens. The two band imaging spectrometers shared the primary lens and the second lens of the fore-lens and use their own collimating lens, interferometers and Fourier transform lens. The collimating lens and the Fourier transform lens of each spectrometer could be designed to the same structural style and parameters. The both spectrometers had a focal length of 1000mm, F number of 5, FOV(field of view) of 1°. Moreover, both image qualities were close to the diffraction limit, the distortion was less than 2%. The advantage of the instrument was that dual band spectral image could be acquired at the same time and the interferometer was miniaturized extremely in the case of unchanged technical indicators.
NASA Astrophysics Data System (ADS)
Lozano, Gabriel; Barten, Tommy; Grzela, Grzegorz; Gómez Rivas, Jaime
2014-01-01
We demonstrate that an ordered array of aluminum nanopyramids, behaving as a phased array of optical antennae, strongly modifies light absorption in thin layers of dye molecules. Photoluminescence measurements as a function of the illumination angle are performed using a time-reversed Fourier microscope. This technique enables a variable-angle plane-wave illumination of nanostructures in a microscope-based setup. Our measurements reveal an enhancement of the light conversion in certain directions of illumination, which indicate the efficient diffractive coupling between the free space radiation and the surface plasmons. Numerical simulations confirm that surface modes supported by the periodic array enhance the intensity of the pump field in the space between particles, where the dye molecules are located, yielding a directional plasmonic-mediated enhancement of the optical absorption. This combined experimental and numerical characterization of the angular dependence of light absorption in nanostructures can be beneficial for the design and optimization of devices in which the harvesting of light plays a major role.
Defining photon channels in strong-field physics: the photon-phase Fourier representation
NASA Astrophysics Data System (ADS)
Zeng, Shuo; Zohrabi, Mohammad; Berry, Ben; Ablikim, Utuq; Kling, Nora; Severt, Travis; Jochim, Bethany; Carnes, Kevin; Ben-Itzhak, Itzik; Esry, Brett
2014-05-01
In strong-field physics, complex atomic and molecular dynamics can be steered by the carrier-envelope phase (CEP). The general theory formulated in Refs., provides a rigorous foundation upon which this understanding might be built. By recognizing the underlying periodicity of the time-dependent Schrödinger equation--and thus its solutions--in the CEP, all CEP effects can be understood as the interference of different photon channels. We will show that this understanding can be turned around to extract information on the photon channel by examining the CEP dependence. In particular, by taking the Fourier transform with respect to the CEP, photon channel information can be extracted from both theory and experiment. Through several examples, we will also show that this technique can be applied to any system and provides knowledge of the net numbers of photons absorbed--even in few-cycle pulses--that is not available in any other way. This work was supported by the Chemical Sciences, Geosciences, and Biosciences Division, Office of Basic Energy Sciences, Office of Science, U.S. Department of Energy under Grant No. DE-FG02-86ER13491. The PULSAR laser was provided by Grant No. DE-FG02-09.
A. -P. Bernier; M. Charlebois; L. Drissen; F. Grandmont
2008-06-04
We present the most recent technical improvements on SpIOMM, an Imaging Fourier Transform Spectrometer (IFTS) attached to the 1.6 telescope of the Mont M\\'egantic Observatory. The recent development of SpIOMM demonstrates that the concept of IFTS for ground telescopes is a promising astronomical 3D spectroscopy technique for multi-object spectroscopy and multi-band imaging. SpIOMM has been developed through a collaboration between Universit\\'e Laval and the industry (ABB Bomem). It is designed for optical observations from the near UV (350 nm) to the near IR (850 nm) with variable spectral resolution. The circular FOV of the instrument covers 12 arcmin in diameter. We have recently improved the servo system algorithm which now controls the mirror displacement and alignment at a rate of ~7000Hz. Hardware improvements to the servo and the metrology system will be described along with their impacts on performance in the laboratory and in observing conditions. The instrument has successfully been operated at the 1.6 meter telescope this year using the revised control systems and acquired several datacubes. We will discuss some issues regarding the sensitivity to environmental conditions implied by the use of such an instrument. An overview of the datacube reduction procedure will show some solutions proposed for observational problems encountered that affect the quality of the data such as sky transmission variations, wind, changing gravity vector and temperature.
NASA Astrophysics Data System (ADS)
Harley, Jacob L.
Recent advances in computational models to simulate turbulent, reactive flow fields have outpaced the ability to collect highly constraining data---throughout the entire flow field---for validating and improving such models. In particular, the ability to quantify in three dimensions both the mean scalar fields (i.e. temperature & species concentrations) and their respective fluctuation statistics via hyperspectral imaging would be a game-changing advancement in combustion diagnostics, with high impact in both validation and improvement efforts for computational combustion models. This research effort establishes imaging Fourier- transform spectrometry (IFTS) as a valuable tool (which complements laser diagnostics) for the study of turbulent combustion. Specifically, this effort (1) demonstrates that IFTS can be used to quantitatively measure spatially resolved spectra from a canonical turbulent flame; (2) establishes the utility of quantile spectra in first-ever quantitative comparisons between measured and modeled turbulent radiation interaction (TRI); (3) develops a simple onion-peeling-like spectral inversion methodology suitable for estimating radial scalar distributions in axisymmetric, optically-thick flames; (4) builds understanding of quantile spectra and demonstrates proof of concept for their use in estimating scalar fluctuation statistics.
Abbink, R.E.
1997-06-01
This document is the final report on work performed at Sandia National Laboratories during FY 1992 and 1993 for a Laboratory Directed Research and Development (LDRD) program to look at problems associated with the design and long term operation of a short wavelength imaging Fourier Transform (FT) spectrometer for use in space. In attempts to answer two fundamental questions: is a FT spectrometer with a resolution of 1 cm{sup {minus}1} covering the silicon detector wavelength range of 0.4 to 1.1 microns feasible in a long life space instrument and, if so, is it the best method of obtaining the desired information? Emphasis has been on identifying methods which minimize reliance on precision mechanical alignment and precise velocity control. An important consideration has also been to develop methods which will be compatible with a variety of self-scanning solid state imaging devices. A breadboard instrument was constructed using cube corner retroreflectors and a laser diode position reference. Some preliminary results are reported. This work is primarily intended to act as an aid to engineers at Sandia who wish to pursue the fabrication of a flight qualified instrument. The theoretical parts are intended to be somewhat tutorial in nature to aid the engineer who is not familiar with FT spectroscopy.
NASA Astrophysics Data System (ADS)
Bernier, Anne-Pier; Charlebois, Maxime; Drissen, Laurent; Grandmont, Frédéric
2008-07-01
We present the most recent technical improvements on SpIOMM, an Imaging Fourier Transform Spectrometer (IFTS) attached to the 1.6 telescope of the Mont Megantic Observatory. The recent development of SpIOMM demonstrates that the concept of IFTS for ground telescopes is a promising astronomical 3D spectroscopy technique for multi-object spectroscopy and multi-band imaging. SpIOMM has been developed through a collaboration between Universite Laval and the industry (ABB Bomem). It is designed for optical observations from the near UV (350 nm) to the near IR (850 nm) with variable spectral resolution. The circular FOV of the instrument covers 12' in diameter. We have recently improved the servo system algorithm which now controls the mirror displacement and alignment at a rate of ~7kHz. Hardware improvements to the servo and the metrology system will be described along with their impacts on performance in the laboratory and in observing conditions. The instrument has successfully been operated at the 1.6 meter telescope this year using the revised control systems and acquired several datacubes. We will discuss some issues regarding the sensitivity to environmental conditions implied by the use of such an instrument. An overview of the datacube reduction procedure will show some solutions proposed for observational problems encountered that affect the quality of the data such as sky transmission variations, wind, changing gravity vector and temperature.
Robust phase sensitive inversion recovery imaging
Garach, Ravindra Mahendrakumar
2005-11-01
- echo sequence on a 15 Tesla MR scanner (a) Real image; (b) Magnitude reconstruction; (c) PSIR image. : : : : : : : : : : : : : : 60 33 Phase sensitive reconstruction of data acquired using a fast spin- echo sequence on a 15 Tesla MR scanner (a) Real... of data acquired using a fast spin- echo sequence on a 15 Tesla MR scanner (a) Real image; (b) Magnitude reconstruction; (c) PSIR image reconstructed with in- verted polarity. This example demonstrates the problem of global polarity determination...
Genetic Algorithm Phase Retrieval for the Systematic Image-Based Optical Alignment Testbed
NASA Technical Reports Server (NTRS)
Taylor, Jaime; Rakoczy, John; Steincamp, James
2003-01-01
Phase retrieval requires calculation of the real-valued phase of the pupil fimction from the image intensity distribution and characteristics of an optical system. Genetic 'algorithms were used to solve two one-dimensional phase retrieval problem. A GA successfully estimated the coefficients of a polynomial expansion of the phase when the number of coefficients was correctly specified. A GA also successfully estimated the multiple p h e s of a segmented optical system analogous to the seven-mirror Systematic Image-Based Optical Alignment (SIBOA) testbed located at NASA s Marshall Space Flight Center. The SIBOA testbed was developed to investigate phase retrieval techniques. Tiphilt and piston motions of the mirrors accomplish phase corrections. A constant phase over each mirror can be achieved by an independent tip/tilt correction: the phase Conection term can then be factored out of the Discrete Fourier Tranform (DFT), greatly reducing computations.
NASA Astrophysics Data System (ADS)
Popp, Alexander; Wendel, Martina; Knels, Lilla; Koch, T.; Koch, Edmund
2006-01-01
In this feasibility study, Fourier domain optical coherence tomography (FDOCT) is used for visualizing the 3-D structure of fixated lung parenchyma and to capture real-time cross sectional images of the subpleural alveolar mechanics in a ventilated and perfused isolated rabbit lung. The compact and modular setup of the FDOCT system allows us to image the first 500 µm of subpleural lung parenchyma with a 3-D resolution of 16×16×8 µm (in air). During mechanical ventilation, real-time cross sectional FDOCT images visualize the inflation and deflation of alveoli and alveolar sacks (acini) in successive images of end-inspiratory and end-expiratory phase. The FDOCT imaging shows the relation of local alveolar mechanics to the setting of tidal volume (VT), peak airway pressure, and positive end-expiratory pressure (PEEP). Application of PEEP leads to persistent recruitment of alveoli and acini in the end-expiratory phase, compared to ventilation without PEEP where alveolar collapse and reinflation are observed. The imaging of alveolar mechanics by FDOCT will help to determine the amount of mechanical stress put on the alveolar walls during tidal ventilation, which is a key factor in understanding the development of ventilator induced lung injury (VILI).
NASA Astrophysics Data System (ADS)
Varma, Vishal K.; Ohlander, Samuel; Nguyen, Peter; Vendryes, Christopher; Parthiban, Sujeeth; Hamilton, Blake; Wallis, M. Chad; Kajdacsy-Balla, Andre; Hannaford, Blake; Lendvay, Thomas; Hotaling, James M.; Walsh, Michael J.
2014-03-01
Fourier Transform Infrared (FT-IR) spectroscopic imaging can allow for the rapid imaging of tissue biochemistry in a label-free and non-perturbing fashion. With the rapid adoption of new minimally invasive surgery (MIS) technologies over the last 20 years, adequate skill to safely and effectively use these technologies may not be achieved and risk of undue physical pressure being placed on tissues is a concern. Previous work has demonstrated that a number of histological stains can detect tissue damage, however, this process requires the initiation and progression of a signaling cascade that results in the epitope of interest being expressed. We proposed to identify the early biochemical markers associated with physical tissue damage from applied forces, thus not requiring transcriptional and translational protein synthesis as traditional immunohistochemistry does. To demonstrate that FT-IR can measure biochemical changes in tissues that have undergone physical force, we took ex-vivo lamb's liver that had been freshly excised and applied varying levels of physical pressure (0kPa to 30kPa). Tissues were then formalin-fixed, paraffin-embedded, and sectioned on to glass for H and E staining to identify damage and on to an IR slide for FT-IR imaging. Regions of interest containing hepatocytes were identified and average FT-IR spectra were extracted from the damaged and undamaged livers. FT-IR spectra showed clear biochemical changes associated with tissue damage. In addition, chemical changes could be observed proceeding histological changes observed when using conventional staining approaches.
NASA Astrophysics Data System (ADS)
Leihong, Zhang; Dong, Liang; Bei, Li; Zilan, Pan; Dawei, Zhang; Xiuhua, Ma
2015-07-01
In this article, the algorithm of compressing sensing is used to improve the imaging resolution and realize ghost imaging via compressive sensing for a phase object based on the theoretical analysis of the lensless Fourier imaging of the algorithm of ghost imaging based on phase-shifting digital holography. The algorithm of ghost imaging via compressive sensing based on phase-shifting digital holography uses the bucket detector to measure the total light intensity of the interference and the four-step phase-shifting method is used to obtain the total light intensity of differential interference light. The experimental platform is built based on the software simulation, and the experimental results show that the algorithm of ghost imaging via compressive sensing based on phase-shifting digital holography can obtain the high-resolution phase distribution figure of the phase object. With the same sampling times, the phase clarity of the phase distribution figure obtained by the algorithm of ghost imaging via compressive sensing based on phase-shifting digital holography is higher than that obtained by the algorithm of ghost imaging based on phase-shift digital holography. In this article, this study further extends the application range of ghost imaging and obtains the phase distribution of the phase object.
Near Infrared Surface Plasmon Resonance Phase Imaging and Nanoparticle-Enhanced Surface Plasmon: The techniques of surface plasmon resonance-phase imaging (SPR-PI) and nanoparticle-enhanced SPR-PI have been tool for biological researchers throughout the world.1,2 Surface plasmon resonance imaging (SPRI
NASA Astrophysics Data System (ADS)
Lo, Men-Tzung; Novak, Vera; Peng, C.-K.; Liu, Yanhui; Hu, Kun
2009-06-01
Phase interactions among signals of physical and physiological systems can provide useful information about the underlying control mechanisms of the systems. Physical and biological recordings are often noisy and exhibit nonstationarities that can affect the estimation of phase interactions. We systematically studied effects of nonstationarities on two phase analyses including (i) the widely used transfer function analysis (TFA) that is based on Fourier decomposition and (ii) the recently proposed multimodal pressure flow (MMPF) analysis that is based on Hilbert-Huang transform (HHT)—an advanced nonlinear decomposition algorithm. We considered three types of nonstationarities that are often presented in physical and physiological signals: (i) missing segments of data, (ii) linear and step-function trends embedded in data, and (iii) multiple chaotic oscillatory components at different frequencies in data. By generating two coupled oscillatory signals with an assigned phase shift, we quantify the change in the estimated phase shift after imposing artificial nonstationarities into the oscillatory signals. We found that all three types of nonstationarities affect the performances of the Fourier-based and the HHT-based phase analyses, introducing bias and random errors in the estimation of the phase shift between two oscillatory signals. We also provided examples of nonstationarities in real physiological data (cerebral blood flow and blood pressure) and showed how nonstationarities can complicate result interpretation. Furthermore, we propose certain strategies that can be implemented in the TFA and the MMPF methods to reduce the effects of nonstationarities, thus improving the performances of the two methods.
Lo, Men-Tzung; Novak, Vera; Peng, C-K; Liu, Yanhui; Hu, Kun
2009-06-01
Phase interactions among signals of physical and physiological systems can provide useful information about the underlying control mechanisms of the systems. Physical and biological recordings are often noisy and exhibit nonstationarities that can affect the estimation of phase interactions. We systematically studied effects of nonstationarities on two phase analyses including (i) the widely used transfer function analysis (TFA) that is based on Fourier decomposition and (ii) the recently proposed multimodal pressure flow (MMPF) analysis that is based on Hilbert-Huang transform (HHT)-an advanced nonlinear decomposition algorithm. We considered three types of nonstationarities that are often presented in physical and physiological signals: (i) missing segments of data, (ii) linear and step-function trends embedded in data, and (iii) multiple chaotic oscillatory components at different frequencies in data. By generating two coupled oscillatory signals with an assigned phase shift, we quantify the change in the estimated phase shift after imposing artificial nonstationarities into the oscillatory signals. We found that all three types of nonstationarities affect the performances of the Fourier-based and the HHT-based phase analyses, introducing bias and random errors in the estimation of the phase shift between two oscillatory signals. We also provided examples of nonstationarities in real physiological data (cerebral blood flow and blood pressure) and showed how nonstationarities can complicate result interpretation. Furthermore, we propose certain strategies that can be implemented in the TFA and the MMPF methods to reduce the effects of nonstationarities, thus improving the performances of the two methods. PMID:19658541
Neelavalli, Jaladhar; Cheng, Yu-Chung N.; Jiang, Jing; Haacke, E. Mark
2009-01-01
Purpose To estimate magnetic field variations induced from air-tissue interface geometry and remove their effects from susceptibility weighted imaging (SWI) data. Materials and Methods A Fourier-transform-based field estimation method is used to calculate the field deviation arising from air-tissue interface geometry. This is accomplished by, first, manually drawing or automatically detecting the sinuses, the mastoid cavity and the head geometry. The difference in susceptibility, ??, between brain tissue and air-spaces is then calculated using a residual-phase minimization approach. SWI data are corrected by subtracting the predicted phase from the original phase image. Resultant phase images are then used to perform the SWI post-processing. Results Significant improvement in the post-processed SWI data is demonstrated, most notably in the frontal and midbrain regions and to a lesser extent at the boundary of the brain. Specifically, there is much less dropout of signal after phase correction near air-tissue interfaces making it possible to see vessels and structures that were often incorrectly removed by the conventional SWI post-processing. Conclusion The Fourier-transform-based field estimation method is a powerful 3D background phase removal method for improving SW images, providing clearer images of the fore-brain and the mid-brain regions. PMID:19306433
Robust phase sensitive inversion recovery imaging
Garach, Ravindra Mahendrakumar
2005-11-01
pixel can take positive as well as negative values. The corresponding polarity information is contained in the phase of the complex image. Due to numerous factors associated with the Magnetic Resonance (MR) scanner and the associated acquisition system...
NASA Astrophysics Data System (ADS)
Vaziri Z., Zahra; McElroy, Charles T.; Feng, Keh-Harng; Moeini, Omid; Walker, Kaley A.; Martin, Randall; Grandmont, Frederic J.
2015-04-01
Arctic climate is changing more rapidly than expected. Multi-year ice is melting and opening the way for shipping and exploration activity for natural resources which in turn increases air pollution. Observing greenhouse gases on a global scale is essential to monitor climate change, especially in the Arctic. Several space missions monitor trace gasses but are in low-earth, sun synchronous orbits and do not have a 24/7 view of northern latitudes. The Canadian Space Agency (CSA), along with other Canadian government departments, is proposing the Polar Communications and Weather (PCW) satellite to provide weather, communication and atmospheric composition information over the Arctic. The use of two satellites in out-of-phase highly elliptical three-apogee orbits with an apogee at ~40,000 km over the Arctic, will provide continuous quasi-geostationary viewing of the northern latitudes. The planned meteorological instrument for the PCW mission is a 21-channel spectral imager with UV, visible, NIR and MIR channels, similar to MODIS and ABI, capable of measuring several different trace gasses. This paper will focus on the development of an Imaging Fourier Transform Spectrometer (IFTS) to be flown on a high-altitude balloon to demonstrate the capacity to monitor methane and carbon dioxide in the Arctic as part of the PHEOS-WCA (Polar Highly Elliptical Orbit Science - Weather, Climate and Air quality) instrument suit; a science complement to the PCW mission. Funding through the CSA Flights for the Advancement of Science and Technology (FAST) program is in place to develop the demonstrator IFTS to show that measurements of methane and carbon dioxide can be collected from space in the 1.6 µm band. The characteristics of the instrument and plans for the balloon flight will be discussed and details of the PCW mission and PHEOS-WCA component will be presented. The authors acknowledge support of the PHEOS-WCA science team.
Byung Mook Weon; Jung Ho Je; Yeukuang Hwu
2006-01-01
In the last decade X-ray imaging based on phase contrast greatly advanced thanks to the use of unmonochromatic synchrotron hard X-rays. The recent advances are going beyond microradiology and microtomography to reach nanometre scale. This paper reviews basic theory and selected applications to biomedical and materials sciences. The forthcoming improvements in phase contrast X-ray imaging will lead to even better
Cryo-EM Image Alignment Based on Nonuniform Fast Fourier Transform
Yang, Zhengfan; Penczek, Pawel A.
2008-01-01
In single particle analysis, two-dimensional (2-D) alignment is a fundamental step intended to put into register various particle projections of biological macromolecules collected at the electron microscope. The efficiency and quality of three-dimensional (3-D) structure reconstruction largely depends on the computational speed and alignment accuracy of this crucial step. In order to improve the performance of alignment, we introduce a new method that takes advantage of the highly accurate interpolation scheme based on the gridding method, a version of the nonuniform Fast Fourier Transform, and utilizes a multi-dimensional optimization algorithm for the refinement of the orientation parameters. Using simulated data, we demonstrate that by using less than half of the sample points and taking twice the runtime, our new 2-D alignment method achieves dramatically better alignment accuracy than that based on quadratic interpolation. We also apply our method to image to volume registration, the key step in the single particle EM structure refinement protocol. We find that in this case the accuracy of the method not only surpasses the accuracy of the commonly used real-space implementation, but results are achieved in much shorter time, making gridding-based alignment a perfect candidate for efficient structure determination in single particle analysis. PMID:18499351
NASA Astrophysics Data System (ADS)
Cheheltani, Rabee; Rosano, Jenna M.; Wang, Bin; Sabri, Abdel Karim; Pleshko, Nancy; Kiani, Mohammad F.
2012-05-01
Myocardial infarction often leads to an increase in deposition of fibrillar collagen. Detection and characterization of this cardiac fibrosis is of great interest to investigators and clinicians. Motivated by the significant limitations of conventional staining techniques to visualize collagen deposition in cardiac tissue sections, we have developed a Fourier transform infrared imaging spectroscopy (FT-IRIS) methodology for collagen assessment. The infrared absorbance band centered at 1338 cm-1, which arises from collagen amino acid side chain vibrations, was used to map collagen deposition across heart tissue sections of a rat model of myocardial infarction, and was compared to conventional staining techniques. Comparison of the size of the collagen scar in heart tissue sections as measured with this methodology and that of trichrome staining showed a strong correlation (R=0.93). A Pearson correlation model between local intensity values in FT-IRIS and immuno-histochemical staining of collagen type I also showed a strong correlation (R=0.86). We demonstrate that FT-IRIS methodology can be utilized to visualize cardiac collagen deposition. In addition, given that vibrational spectroscopic data on proteins reflect molecular features, it also has the potential to provide additional information about the molecular structure of cardiac extracellular matrix proteins and their alterations.
NASA Astrophysics Data System (ADS)
Bernier, A.-P.; Grandmont, F.; Rochon, J.-F.; Charlebois, M.; Drissen, L.
2006-06-01
We present an overview of SpIOMM, an Imaging Fourier Transform Spectrometer (IFTS) for astronomy developed at University Laval in collaboration with ABB, INO and the Canadian Space Agency. SpIOMM, attached to the 1.6 meter (f/8) telescope at the Observatoire du mont Megantic in Quebec. It is a Michelson-type interferometer capable of obtaining the visible spectrum (from 350 nm to 900 nm) of every light source within its 12 arcminute circular field of view. This design will allow the correction of variable sky transmission. It consists of a dual output port and the total throughput is exploited by two CCDs used as detectors. We present the concept and design of this unique instrument. A metrology system combined with a dynamic alignment assures a good sampling and mirror alignment during the entire acquisition sequence. This particular servo control is explained and demonstrated and its capabilities and performance are discussed. We introduce the use of specific bandpass filters centered on the most important groups of emission lines which, when combined with spectral folding algorithms, allows us to reach high spectral resolution (R = 25 000, or 1 cm -1). Astronomical data collected by SpIOMM in 2004-2005 are also presented.
Philip, J
1979-04-01
We consider the convolution equation f * h + e = d, where f is sought, h is a known ``point spread function,'' e represents random errors, and d is the measured data. All these functions are defined on the integers mod(N). A mathematical-statistical fonnulation of the problem leads to minff * hdA, where the A-norm is derived from the statistical distribution of e. If f is known to be nonnegative, this is a quadratic progamming problem. Using the discrete Fourier transforms (DFT's) F, H, and D of f, h, and d, we arrive at a minimization in another norm: minF F · H-D ¿. A solution would be F = D/H, but H has zeros. We consider the theoretical and practical difficulties that arise from these zeros and describe two methods for calculating F numerically also when H has zeros. Numerical tests of the methods are presented, in particular tests with one of the methods, called ``the derivative method,'' where d is a blurred image. PMID:21868873
Quantitative x-ray phase imaging at the nanoscale by multilayer Laue lenses
Yan, Hanfei; Chu, Yong S.; Maser, Jörg; Nazaretski, Evgeny; Kim, Jungdae; Kang, Hyon Chol; Lombardo, Jeffrey J.; Chiu, Wilson K. S.
2013-01-01
For scanning x-ray microscopy, many attempts have been made to image the phase contrast based on a concept of the beam being deflected by a specimen, the so-called differential phase contrast imaging (DPC). Despite the successful demonstration in a number of representative cases at moderate spatial resolutions, these methods suffer from various limitations that preclude applications of DPC for ultra-high spatial resolution imaging, where the emerging wave field from the focusing optic tends to be significantly more complicated. In this work, we propose a highly robust and generic approach based on a Fourier-shift fitting process and demonstrate quantitative phase imaging of a solid oxide fuel cell (SOFC) anode by multilayer Laue lenses (MLLs). The high sensitivity of the phase to structural and compositional variations makes our technique extremely powerful in correlating the electrode performance with its buried nanoscale interfacial structures that may be invisible to the absorption and fluorescence contrasts. PMID:23419650
Quantitative x-ray phase imaging at the nanoscale by multilayer Laue lenses.
Yan, Hanfei; Chu, Yong S; Maser, Jörg; Nazaretski, Evgeny; Kim, Jungdae; Kang, Hyon Chol; Lombardo, Jeffrey J; Chiu, Wilson K S
2013-01-01
For scanning x-ray microscopy, many attempts have been made to image the phase contrast based on a concept of the beam being deflected by a specimen, the so-called differential phase contrast imaging (DPC). Despite the successful demonstration in a number of representative cases at moderate spatial resolutions, these methods suffer from various limitations that preclude applications of DPC for ultra-high spatial resolution imaging, where the emerging wave field from the focusing optic tends to be significantly more complicated. In this work, we propose a highly robust and generic approach based on a Fourier-shift fitting process and demonstrate quantitative phase imaging of a solid oxide fuel cell (SOFC) anode by multilayer Laue lenses (MLLs). The high sensitivity of the phase to structural and compositional variations makes our technique extremely powerful in correlating the electrode performance with its buried nanoscale interfacial structures that may be invisible to the absorption and fluorescence contrasts. PMID:23419650
Imaging of laser induced ultrasound with a spiral phase contrast method
NASA Astrophysics Data System (ADS)
Bader, Paul; Zangerl, Matthias; Bernet, Stefan; Ritsch-Marte, Monika
2008-08-01
Optical snapshot images of photo-acoustically generated sound waves in a water tank can be obtained by 'spiral phase contrast filtering', a variant of phase contrast imaging. To this end a two-dimensional transmission image of the ultrasonic field is recorded by illuminating the water volume by an expanded nanosecond laser pulse, and guiding the transmitted beam through a spiral phase plate (SPP) placed in a Fourier plane of the optical path. This generates a strong intensity contrast at gradients of the refractive index, corresponding to acoustically induced pressure gradients in the liquid. As an advantage with respect to a standard knife-edge Schlieren method, the spiral phase filter provides an isotropic contrast enhancement of refractive index modulations. Thus the method has the potential to act as a fast imaging method for photo-acoustic tomography.
Phase contrast portal imaging using synchrotron radiation
NASA Astrophysics Data System (ADS)
Umetani, K.; Kondoh, T.
2014-07-01
Microbeam radiation therapy is an experimental form of radiation treatment with great potential to improve the treatment of many types of cancer. We applied a synchrotron radiation phase contrast technique to portal imaging to improve targeting accuracy for microbeam radiation therapy in experiments using small animals. An X-ray imaging detector was installed 6.0 m downstream from an object to produce a high-contrast edge enhancement effect in propagation-based phase contrast imaging. Images of a mouse head sample were obtained using therapeutic white synchrotron radiation with a mean beam energy of 130 keV. Compared to conventional portal images, remarkably clear images of bones surrounding the cerebrum were acquired in an air environment for positioning brain lesions with respect to the skull structure without confusion with overlapping surface structures.
Phase contrast portal imaging using synchrotron radiation
Umetani, K., E-mail: umetani@spring8.or.jp [Japan Synchrotron Radiation Research Institute, SPring-8, Sayo-cho, Sayo-gun, Hyogo 679-5198 (Japan); Kondoh, T. [Kobe University Graduate School of Medicine, Kusunoki-cho, Chuo-ku, Kobe-shi, Hyogo 650-0017 (Japan)
2014-07-15
Microbeam radiation therapy is an experimental form of radiation treatment with great potential to improve the treatment of many types of cancer. We applied a synchrotron radiation phase contrast technique to portal imaging to improve targeting accuracy for microbeam radiation therapy in experiments using small animals. An X-ray imaging detector was installed 6.0 m downstream from an object to produce a high-contrast edge enhancement effect in propagation-based phase contrast imaging. Images of a mouse head sample were obtained using therapeutic white synchrotron radiation with a mean beam energy of 130 keV. Compared to conventional portal images, remarkably clear images of bones surrounding the cerebrum were acquired in an air environment for positioning brain lesions with respect to the skull structure without confusion with overlapping surface structures.
Phase contrast portal imaging using synchrotron radiation.
Umetani, K; Kondoh, T
2014-07-01
Microbeam radiation therapy is an experimental form of radiation treatment with great potential to improve the treatment of many types of cancer. We applied a synchrotron radiation phase contrast technique to portal imaging to improve targeting accuracy for microbeam radiation therapy in experiments using small animals. An X-ray imaging detector was installed 6.0 m downstream from an object to produce a high-contrast edge enhancement effect in propagation-based phase contrast imaging. Images of a mouse head sample were obtained using therapeutic white synchrotron radiation with a mean beam energy of 130 keV. Compared to conventional portal images, remarkably clear images of bones surrounding the cerebrum were acquired in an air environment for positioning brain lesions with respect to the skull structure without confusion with overlapping surface structures. PMID:25085143
Min Cao; Yaowen Fu; Weidong Jiang; Xiang Li; Zhaowen Zhuang
2007-01-01
Due to high speed moving of the target, the wideband radar echoes after dechirping is a multi-component LFM signal. Directly using the fast Fourier transform (FFT) to implement pulse compression, the high resolution range profile (HRRP) will be broadened and distorted. To improve the quality of the HRRP, considering the fractional Fourier transform (FRFT) is the generalization of the FFT
NASA Astrophysics Data System (ADS)
Vasi?, Borislav; Gaji?, Radoš
2011-09-01
Using numerical simulations, we investigate the realization of self-focusing media using two-dimensional graded photonic crystals and their applications for imaging and non-imaging purposes. The two-dimensional graded photonic crystals consist of spatially varying cylindrical holes drilled in a dielectric host. By controlling the gradient of the refractive index and the thickness of the self-focusing medium, it is possible to obtain either a focusing lens with Fourier transforming capabilities or an imaging lens, which produces inverted images. Non-imaging applications include a simple antenna for directive emission obtained from the focusing lens, whereas a directional cloak is obtained by modifying the imaging lens. Graded photonic crystal based devices work well up to the Bragg frequencies. They are compact, made from lossless dielectrics, and compatible with planar lithographic techniques, so they can find applications in a broad frequency range, even at the optical frequencies.
Phase retrieval from single frame projection fringe pattern with variational image decomposition
NASA Astrophysics Data System (ADS)
Zhu, Xinjun; Tang, Chen; Li, Biyuan; Sun, Chen; Wang, Linlin
2014-08-01
Phase retrieval from single frame projection fringe pattern is of fundamental importance, and is also a challenging problem in fringe projection measurement. In this paper, we present a new method for phase retrieval from a single frame projection fringe pattern based on variational image decomposition (VID) methods. We propose a new image decomposition model TV-G-Shearlet in order to effectively split a projection fringe pattern into background part, fringe part and noise part. The performance of the proposed approach is verified by simulated and real projection fringes as well as the comparison with the widely used and well-known Fourier transform method and wavelet transform method.
Timothy R. McJunkin; Paul L. Tremblay; Jill R. Scott
2002-01-01
This paper describes the automation of an imaging internal source laser desorption Fourier transform mass spectrometer (I2LD-FTMS). The I2LD-FTMS consists of a laser-scanning device [Scott and Tremblay, Rev. Sci. Instrum. 2002, 73, 1108–1116] that has been integrated with a laboratory-built FTMS using a commercial data acquisition system (ThermoFinnigan FT\\/MS, Bremen, Germany). A new user interface has been developed in National
NASA Astrophysics Data System (ADS)
Tian, Jialin; Smith, William L.; Gazarik, Michael J.
2008-10-01
The ultimate remote sensing benefits of the high resolution Infrared radiance spectrometers will be realized with their geostationary satellite implementation in the form of imaging spectrometers. This will enable dynamic features of the atmosphere's thermodynamic fields and pollutant and greenhouse gas constituents to be observed for revolutionary improvements in weather forecasts and more accurate air quality and climate predictions. As an important step toward realizing this application objective, the Geostationary Imaging Fourier Transform Spectrometer (GIFTS) Engineering Demonstration Unit (EDU) was successfully developed under the NASA New Millennium Program, 2000-2006. The GIFTS-EDU instrument employs three focal plane arrays (FPAs), which gather measurements across the long-wave IR (LWIR), short/mid-wave IR (SMWIR), and visible spectral bands. The raw GIFTS interferogram measurements are radiometrically and spectrally calibrated to produce radiance spectra, which are further processed to obtain atmospheric profiles via retrieval algorithms. The radiometric calibration is achieved using internal blackbody calibration references at ambient (260 K) and hot (286 K) temperatures. The absolute radiometric performance of the instrument is affected by several factors including the FPA off-axis effect, detector/readout electronics induced nonlinearity distortions, and fore-optics offsets. The GIFTS-EDU, being the very first imaging spectrometer to use ultra-high speed electronics to readout its large area format focal plane array detectors, operating at wavelengths as large as 15 microns, possessed non-linearity's not easily removable in the initial calibration process. In this paper, we introduce a refined calibration technique that utilizes Principle Component (PC) analysis to compensate for instrument distortions and artifacts remaining after the initial radiometric calibration process, thus, further enhance the absolute calibration accuracy. This method is applied to data collected during an atmospheric measurement experiment with the GIFTS, together with simultaneous observations by the accurately calibrated AERI (Atmospheric Emitted Radiance Interferometer), both simultaneously zenith viewing the sky through the same external scene mirror at ten-minute intervals throughout a cloudless day at Logan Utah on September 13, 2006. The PC vectors of the calibrated radiance spectra are defined from the AERI observations and regression matrices relating the initial GIFTS radiance PC scores to the AERI radiance PC scores are calculated using the least squares inverse method. A new set of accurately calibrated GIFTS radiances are produced using the first four PC scores in the regression model. Temperature and moisture profiles retrieved from the PC-calibrated GIFTS radiances are verified against radiosonde measurements collected throughout the GIFTS sky measurement period.
Wang, Xiaogang; Zhao, Daomu
2013-09-15
We propose a simple amplitude-phase retrieval attack free cryptosystem based on direct attack to phase-truncated Fourier-transform-based encryption using a random amplitude mask (RAM). The RAM that is not saved during the encryption provides extremely high security for the two private keys, and no iterative calculations are involved in the nonlinear encryption process. Lack of enough constraints makes the specific attack based on iterative amplitude-phase retrieval algorithms unusable. Numerical simulation results are given for testing the validity and security of the proposed approach. PMID:24104846
Zhao, Ming; Li, Yu; Peng, Leilei
2014-09-22
We report a fast non-iterative lifetime data analysis method for the Fourier multiplexed frequency-sweeping confocal FLIM (Fm-FLIM) system [Opt. Express 22, 10221 (2014)]. The new method, named R-method, allows fast multi-channel lifetime image analysis in the system's FPGA data processing board. Experimental tests proved that the performance of the R-method is equivalent to that of single-exponential iterative fitting, and its sensitivity is well suited for time-lapse FLIM-FRET imaging of live cells, for example cyclic adenosine monophosphate (cAMP) level imaging with GFP-Epac-mCherry sensors. With the R-method and its FPGA implementation, multi-channel lifetime images can now be generated in real time on the multi-channel frequency-sweeping FLIM system, and live readout of FRET sensors can be performed during time-lapse imaging. PMID:25321778
Melmer, Tamara; Amirshahi, Seyed A.; Koch, Michael; Denzler, Joachim; Redies, Christoph
2013-01-01
The spatial characteristics of letters and their influence on readability and letter identification have been intensely studied during the last decades. There have been few studies, however, on statistical image properties that reflect more global aspects of text, for example properties that may relate to its aesthetic appeal. It has been shown that natural scenes and a large variety of visual artworks possess a scale-invariant Fourier power spectrum that falls off linearly with increasing frequency in log-log plots. We asked whether images of text share this property. As expected, the Fourier spectrum of images of regular typed or handwritten text is highly anisotropic, i.e., the spectral image properties in vertical, horizontal, and oblique orientations differ. Moreover, the spatial frequency spectra of text images are not scale-invariant in any direction. The decline is shallower in the low-frequency part of the spectrum for text than for aesthetic artworks, whereas, in the high-frequency part, it is steeper. These results indicate that, in general, images of regular text contain less global structure (low spatial frequencies) relative to fine detail (high spatial frequencies) than images of aesthetics artworks. Moreover, we studied images of text with artistic claim (ornate print and calligraphy) and ornamental art. For some measures, these images assume average values intermediate between regular text and aesthetic artworks. Finally, to answer the question of whether the statistical properties measured by us are universal amongst humans or are subject to intercultural differences, we compared images from three different cultural backgrounds (Western, East Asian, and Arabic). Results for different categories (regular text, aesthetic writing, ornamental art, and fine art) were similar across cultures. PMID:23554592
NASA Astrophysics Data System (ADS)
Barrett, Harrison H.; Denny, J. L.; Wagner, Robert F.; Myers, Kyle J.
1995-05-01
Figures of merit for image quality are derived on the basis of the performance of mathematical observers on specific detection and estimation tasks. The tasks include detection of a known signal superimposed on a known background, detection of a known signal on a random background, estimation of Fourier coefficients of the object, and estimation of the integral of the object over a specified region of interest. The chosen observer for the detection tasks is the ideal linear discriminant, which we call the Hotelling observer. The figures of merit are based on the Fisher information matrix relevant to estimation of the Fourier coefficients and the closely related Fourier crosstalk matrix introduced earlier by Barrett and Gifford [Phys. Med. Biol. 39, 451 (1994)]. A finite submatrix of the infinite Fisher information matrix is used to set Cramer-Rao lower bounds on the variances of the estimates of the first N Fourier coefficients. The figures of merit for detection tasks are shown to be closely related to the concepts of noise-equivalent quanta (NEQ) and
Fast and contrast-enhanced phase-sensitive magnetic resonance imaging
Son, Jong Bum
2009-05-15
pulse sequence .................................................... 43 Fig 4.5 Illustration of phase correction using a ternary adaptive Markov random field model...-space information is acquired at an echo-time (TE), which is 2-D Fourier transform of the image in the field-of-view (FOV), yx j k yj k xxy FOVS ( k , k ) = I ( x , y ) e e d x d y?? [2.5] where xxk = ?Gt . II.2 Chemical-Shift Selective...
Free-viewpoint images captured using phase-shifting synthetic aperture digital holography.
Nakatsuji, Tatsuya; Matsushima, Kyoji
2008-07-01
Free-viewpoint images obtained from phase-shifting synthetic aperture digital holography are given for scenes that include multiple objects and a concave object. The synthetic aperture technique is used to enlarge the effective sensor size and to make it possible to widen the range of changing perspective in the numerical reconstruction. The lensless Fourier setup and its aliasing-free zone are used to avoid aliasing errors arising at the sensor edge and to overcome a common problem in digital holography, namely, a narrow field of view. A change of viewpoint is realized by a double numerical propagation and by clipping the wave field by a given pupil. The computational complexity for calculating an image in the given perspective from the base complex-valued image is estimated at a double fast Fourier transform. The experimental results illustrate the natural change of appearance in cases of both multiple objects and a concave object. PMID:18594569
Split-step Fourier shot-record migration with deconvolution imaging
Delman Lee; Iain M. Mason; Geoffrey M. Jackson
1991-01-01
The split-step Fourier method is used here to prestackmigrate two synthetic borehole-to-surfaceshot gathers. Model structures in the zone ofspecular illumination beneath the shot are reconstructedby using the split-step Fourier methodboth to back-propagate the recorded wave-fieldand to forward propagate the source wavelet. Theoverburden is vertically and laterally inhomogeneous.Each depth interval is treated as a homogeneousstrip with the mean velocity plus aninhomogeneity...
Accurate quantitative phase imaging using generalized phase contrast.
Rodrigo, Peter John; Palima, Darwin; Glückstad, Jesper
2008-02-18
The generalized phase contrast (GPC) method is explored for improving the accuracy in quantitative reconstruction of two-dimensional phase distribution from images of semi-transparent objects viewed with a common-path interferometer (CPI). We propose a novel optical scheme for highly accurate determination of the object-dependent complex synthetic reference wave (SRW) in a CPI. Using a simple 4f imaging optical setup, GPC provides an analytic model of the SRW profile that is shown here to increase phase measurement accuracy over the entire output aperture. The improved accuracy due to the GPC model can exceed one order of magnitude compared to that of the conventional plane wave model of the reference beam. Furthermore, we describe a novel method for accurate derivation of the strength of the phase object's zero spatial frequency component based on the intensity of the traditionally ignored halo region encompassing the interferogram. Combining this information with three inteferometric measurements, full-field phase images with unconstrained phase strokes are obtained accurately. PMID:18542358
NASA Astrophysics Data System (ADS)
Giarra, Matthew N.; Charonko, John J.; Vlachos, Pavlos P.
2015-03-01
Traditional particle image velocimetry (PIV) uses discrete Cartesian cross correlations (CCs) to estimate the displacements of groups of tracer particles within small subregions of sequentially captured images. However, these CCs fail in regions with large velocity gradients or high rates of rotation. In this paper, we propose a new PIV correlation method based on the Fourier–Mellin transformation (FMT) that enables direct measurement of the rotation and dilation of particle image patterns. In previously unresolvable regions of large rotation, our algorithm significantly improves the velocity estimates compared to traditional correlations by aligning the rotated and stretched particle patterns prior to performing Cartesian correlations to estimate their displacements. Our algorithm, which we term Fourier–Mellin correlation (FMC), reliably measures particle pattern displacement between pairs of interrogation regions with up to ±180° of angular misalignment, compared to 6–8° for traditional correlations, and dilation/compression factors of 0.5–2.0, compared to 0.9–1.1 for a single iteration of traditional correlations. We apply our FMC algorithm to synthetic computer-generated PIV images with known velocity and vorticity fields, and to an experimentally measured flow field. Our results show that combining FMC with discrete window offset (DWO) or iterative image deformation (IID) algorithms decreases the mean and variance of displacement and vorticity errors compared to traditional correlations, and that FMC accelerates the convergence of IID.
Partial Fourier MRI: AR models with SVD
R. W. McColll; M. A. Scarlata
1999-01-01
The authors investigated several partial Fourier imaging techniques to reconstruct magnetic resonance images from the central fifty percent phase encodings. Parametric models were chosen and compared for accuracy in predicting the full time-domain data, and for final image quality. The auto-regressive model, with parameter estimation from Single Value Decomposition (AR-SVD) was compared against the iterative Levinson-Durbin approach, and against auto-regressive
NASA Technical Reports Server (NTRS)
Cecil, R. W.; White, R. A.; Szczur, M. R.
1972-01-01
The IDAMS Processor is a package of task routines and support software that performs convolution filtering, image expansion, fast Fourier transformation, and other operations on a digital image tape. A unique task control card for that program, together with any necessary parameter cards, selects each processing technique to be applied to the input image. A variable number of tasks can be selected for execution by including the proper task and parameter cards in the input deck. An executive maintains control of the run; it initiates execution of each task in turn and handles any necessary error processing.
Sreedhar, Hari; Varma, Vishal K; Nguyen, Peter L; Davidson, Bennett; Akkina, Sanjeev; Guzman, Grace; Setty, Suman; Kajdacsy-Balla, Andre; Walsh, Michael J
2015-01-01
High-definition Fourier Transform Infrared (FT-IR) spectroscopic imaging is an emerging approach to obtain detailed images that have associated biochemical information. FT-IR imaging of tissue is based on the principle that different regions of the mid-infrared are absorbed by different chemical bonds (e.g., C=O, C-H, N-H) within cells or tissue that can then be related to the presence and composition of biomolecules (e.g., lipids, DNA, glycogen, protein, collagen). In an FT-IR image, every pixel within the image comprises an entire Infrared (IR) spectrum that can give information on the biochemical status of the cells that can then be exploited for cell-type or disease-type classification. In this paper, we show: how to obtain IR images from human tissues using an FT-IR system, how to modify existing instrumentation to allow for high-definition imaging capabilities, and how to visualize FT-IR images. We then present some applications of FT-IR for pathology using the liver and kidney as examples. FT-IR imaging holds exciting applications in providing a novel route to obtain biochemical information from cells and tissue in an entirely label-free non-perturbing route towards giving new insight into biomolecular changes as part of disease processes. Additionally, this biochemical information can potentially allow for objective and automated analysis of certain aspects of disease diagnosis. PMID:25650759
System design of Fourier transform imaging spectrometer using tunable lateral shearing splitter
NASA Astrophysics Data System (ADS)
Meng, Xin; Li, Jianxin; Bai, Caixun; Zhu, Rihong
2015-04-01
The Fourier transform spectrometer without slit has the advantages of high radiation throughput and high spatial resolution. It can be used for detecting more details of the spectral and spatial information. We present the initial structure of the collimator and objective based on the analysis of the principle of the Fourier transform spectrometer. Then the collimator and objective are optimized by Zemax. The MTF of the cut-off frequency is great than 0.7. The tunable lateral shearing splitter is used as the interferometer, which makes the system more compact compared with the system using Sagnac lateral shearing splitter. The method to calculate the geometric dimension of the splitter is presented. Then the complete Fourier transform spectrometer is designed. The MTF of the cut-off frequency is great than 0.6. And the largest RMS of the spot is less than 6?m.
Imaging IR spectrometer, phase 2
NASA Technical Reports Server (NTRS)
Gradie, Jonathan; Lewis, Ralph; Lundeen, Thomas; Wang, Shu-I
1990-01-01
The development is examined of a prototype multi-channel infrared imaging spectrometer. The design, construction and preliminary performance is described. This instrument is intended for use with JPL Table Mountain telescope as well as the 88 inch UH telescope on Mauna Kea. The instrument is capable of sampling simultaneously the spectral region of 0.9 to 2.6 um at an average spectral resolution of 1 percent using a cooled (77 K) optical bench, a concave holographic grating and a special order sorting filter to allow the acquisition of the full spectral range on a 128 x 128 HgCdTe infrared detector array. The field of view of the spectrometer is 0.5 arcsec/pixel in mapping mode and designed to be 5 arcsec/pixel in spot mode. The innovative optical design has resulted in a small, transportable spectrometer, capable of remote operation. Commercial applications of this spectrometer design include remote sensing from both space and aircraft platforms as well as groundbased astronomical observations.
Sarunic, Marinko V.; Asrani, Sanjay; Izatt, Joseph A.
2009-01-01
We have demonstrated a novel Fourier-domain optical coherence tomography system and signal-processing algorithm for full-range, real-time, artifact-free quantitative imaging of the anterior chamber. Cross-sectional full-range images comprising 1024×800 pixels (axial×lateral) were acquired and displayed at 6.7 images/s. Volumetric data comprising 1024×400×60 pixels (axial×lateral×elevation) were acquired in 4.5 seconds with real-time visualization of individual slices and 3-dimensional reconstruction performed in postprocessing. Details of the cornea, limbus, iris, anterior lens capsule, trabecular meshwork, and Schlemm’s canal were visualized. Quantitative surface height maps of the corneal epithelium and endothelium were obtained from the volumetric data and used to generate corneal thickness maps. PMID:18413525
NASA Astrophysics Data System (ADS)
Kleinert, A.; Friedl-Vallon, F.; Guggenmoser, T.; Höpfner, M.; Neubert, T.; Ribalda, R.; Sha, M. K.; Ungermann, J.; Blank, J.; Ebersoldt, A.; Kretschmer, E.; Latzko, T.; Oelhaf, H.; Olschewski, F.; Preusse, P.
2014-12-01
The Gimballed Limb Observer for Radiance Imaging of the Atmosphere (GLORIA) is an imaging Fourier transform spectrometer that is capable of operating on various high-altitude research aircraft. It measures the atmospheric emission in the thermal infrared spectral region in limb and nadir geometry. GLORIA consists of a classical Michelson interferometer combined with an infrared camera. The infrared detector has a usable area of 128 × 128 pixels, measuring up to 16 384 interferograms simultaneously. Imaging Fourier transform spectrometers impose a number of challenges with respect to instrument calibration and algorithm development. The optical setup with extremely high optical throughput requires the development of new methods and algorithms for spectral and radiometric calibration. Due to the vast amount of data there is a high demand for scientifically intelligent optimisation of the data processing. This paper outlines the characterisation and processing steps required for the generation of radiometrically and spectrally calibrated spectra. Methods for performance optimisation of the processing algorithm are presented. The performance of the data processing and the quality of the calibrated spectra are demonstrated for measurements collected during the first deployments of GLORIA on aircraft.
NASA Astrophysics Data System (ADS)
Kleinert, A.; Friedl-Vallon, F.; Guggenmoser, T.; Höpfner, M.; Neubert, T.; Ribalda, R.; Sha, M. K.; Ungermann, J.; Blank, J.; Ebersoldt, A.; Kretschmer, E.; Latzko, T.; Oelhaf, H.; Olschewski, F.; Preusse, P.
2014-03-01
The Gimballed Limb Observer for Radiance Imaging of the Atmosphere (GLORIA) is an imaging Fourier transform spectrometer that is capable of operating on various high altitude research aircraft. It measures the atmospheric emission in the thermal infrared spectral region in limb and nadir geometry. GLORIA consists of a classical Michelson interferometer combined with an infrared camera. The infrared detector has a usable range of 128 × 128 pixels, measuring up to 16 384 interferograms simultaneously. Imaging Fourier transform spectrometers impose a number of challenges with respect to instrument calibration and algorithm development. The innovative optical setup with extremely high optical throughput requires the development of new methods and algorithms for spectral and radiometric calibration. Due to the vast amount of data there is a high demand for scientifically intelligent optimisation of the data processing. This paper outlines the characterisation and processing steps required for the generation of radiometrically and spectrally calibrated spectra. Methods for performance optimisation of the processing algorithm are presented. The performance of the data processing and the quality of the calibrated spectra are demonstrated for measurements collected during the first deployments of GLORIA on aircraft.
Temporal phase unwrapping for CINE velocity imaging.
Xiang, Q S
1995-01-01
A simple algorithm named temporal phase unwrapping (TPU) is introduced to address the phase aliasing problem in time-dependent phase contrast (CINE-PC) velocity imaging. The method exploits the temporal continuity of velocity field and unwraps the phase along time. TPU only involves a one-dimensional (1D) temporal integration; therefore, many complications in 2D or 3D spatial phase unwrapping are avoided. Differential velocity maps (DVM) between adjacent movie frames are first calculated from the complex MR images. The DVMs have no phase aliasing as the differential velocities are much smaller than the absolute velocities. Aliasing-free velocity maps are obtained by integrating the DVMs along the time direction provided an aliasing-free reference velocity map (RVM) is found as a starting point of the integration. Typically, such RVMs are always available within the cardiac cycle, especially in diastole where the blood flow is the lowest. In vivo results from fully automated processing and detailed discussion on noise behavior are presented. PMID:8574036
Bojko, Katherine; Roux, Claude; Reedy, Brian J
2008-11-01
In this study, the potential of attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectral imaging as a technique to determine the sequence of line crossings was examined. The technique was successful in determining the sequence of heterogeneous line intersections produced using ballpoint pens and laser printers. By imaging at characteristic frequencies, it was possible to form spectral images showing the spatial distribution of the materials. By examining the spectral images from the inks, it was possible to determine whether the ink was above or below the toner. In blind testing, ATR-FTIR spectral imaging results were directly compared to those obtained by eight experienced forensic document examiners using methods regularly employed in casework. ATR-FTIR spectral imaging was shown to achieve a 100% success rate in the blind tests, whereas some incorrect sequence determinations were made by the forensic document examiners when using traditional techniques. The technique was unable to image ink-jet printing, gel pens, roller ball pens, and felt-tip pens, and was also unable to determine the sequence of intersecting ballpoint pen lines. PMID:18624894
Combined fluorescence and phase contrast imaging at the Advanced Photon Source.
Hornberger, B.; Feser, M.; Jacobsen, C.; Vogt, S.; Legnini, D.; Paterson, D.; Rehak, P.; DeGeronimo, G.; Palmer, B.M.; Experimental Facilities Division (APS); State Univ. of New York at Stony Brook Univ.; BNL; Univ. of Vermont
2006-01-01
X-ray fluorescence microprobes excel at detecting and quantifying trace metals in biological and environmental science samples, but typically do not detect low Z elements such as carbon and nitrogen. Therefore, it is hard to put the trace metals into context with their natural environment. We are implementing phase contrast capabilities with a segmented detector into several microprobes at the Advanced Photon Source (APS) to address this problem. Qualitative differential phase contrast images from a modified soft x-ray detector already provide very useful information for general users. We are also implementing a quantitative method to recover the absolute phase shift by Fourier filtering detector images. New detectors are under development which are optimized for the signal levels present at the APS. In this paper, we concentrate on fundamental signal to noise considerations comparing absorption and differential phase contrast.
X-ray phase contrast image simulation
NASA Astrophysics Data System (ADS)
Peterzol, A.; Berthier, J.; Duvauchelle, P.; Ferrero, C.; Babot, D.
2007-01-01
A deterministic algorithm is proposed to simulate phase contrast (PC) X-ray images for complex three-dimensional (3D) objects. This algorithm has been implemented in a simulation code named VXI (virtual X-ray imaging). The physical model chosen to account for PC technique is based on the Fresnel-Kirchhoff diffraction theory. The algorithm consists mainly of two parts. The first one exploits the VXI ray-tracing approach to compute the object transmission function. The second part simulates the PC image due to the wave front distortion introduced by the sample. In the first part, the use of computer-aided drawing (CAD) models enables simulations to be carried out with complex 3D objects. Differently from the VXI original version, which makes use of an object description via triangular facets, the new code requires a more "sophisticated" object representation based on non-uniform rational B-splines (NURBS). As a first step we produce a spatial high resolution image by using a point and monochromatic source and an ideal detector. To simulate the polychromatic case, the intensity image is integrated over the considered X-ray energy spectrum. Then, in order to account for the system spatial resolution properties, the high spatial resolution image (mono or polychromatic) is convolved with the total point spread function of the imaging system under consideration. The results supplied by the proposed algorithm are examined with the help of some relevant examples.
Quantitative phase imaging through scattering media
NASA Astrophysics Data System (ADS)
Kollárová, Vera; Colláková, Jana; Dostál, Zbynek; Slabý, Tomas; Veselý, Pavel; Chmelík, Radim
2015-03-01
Coherence-controlled holographic microscope (CCHM) is an off-axis holographic system. It enables observation of a sample and its quantitative phase imaging with coherent as well as with incoherent illumination. The spatial and temporal coherence can be modified and thus also the quality and type of the image information. The coherent illumination provides numerical refocusing in wide depth range similarly to a classic coherent-light digital holographic microscopy (HM). Incoherent-light HM is characterized by a high quality, coherence-noise-free imaging with up to twice higher resolution compared to coherent illumination. Owing to an independent, free of sample reference arm of the CCHM the low spatial light coherence induces coherence-gating effect. This makes possible to observe specimen also through scattering media. We have described theoretically and simulated numerically imaging of a two dimensional object through a scattering layer by CCHM using the linear systems theory. We have investigated both strongly and weakly scattering media characterized by different amount of ballistic and diffuse light. The influence of a scattering layer on the quality of a phase signal is discussed for both types of the scattering media. A strong dependence of the imaging process on the light coherence is demonstrated. The theoretical calculations and numerical simulations are supported by experimental data gained with model samples, as well as real biologic objects particularly then by time-lapse observations of live cells reactions to substances producing optically turbid emulsion.
Lensless Coherent Imaging with Shaped Illumination and Phase-Retrieval Image Reconstruction
Fienup, James R.
Lensless Coherent Imaging with Shaped Illumination and Phase-Retrieval Image Reconstruction James R system or on post-detection computations. A lens-less coherent imaging system employing a shaped.0110) Imaging systems; (100.5070) Phase retrieval; (100.0100) Image processing; (100.3010) Image reconstruction
CONTROL OF LASER RADIATION PARAMETERS: Theory of laser array phase locking by Fourier coupling
NASA Astrophysics Data System (ADS)
Vysotskii, D. V.; Napartovich, A. P.; Troshchieva, V. N.
2007-04-01
The type of coupling in a fibre laser array phase locked with the help of an external mirror located at the focal distance from the plane of output ends of individual lasers is studied analytically. The explicit expression is derived for the eigenvalue of the resonator and the restriction on the width of the tuning range in which laser array phase locking is preserved is determined. The influence of the spread in the optical lengths of fibres on the phase-locking efficiency is considered. The phase-locking efficiency is analysed for the spread of optical lengths of fibres considerably exceeding the radiation wavelength.
Semiclassical TEM image formation in phase space.
Lubk, Axel; Röder, Falk
2015-04-01
Current developments in TEM such as high-resolution imaging at low acceleration voltages and large fields of view, the ever larger capabilities of hardware aberration correction and the systematic shaping of electron beams require accurate descriptions of TEM imaging in terms of wave optics. Since full quantum mechanic solutions have not yet been established for, e.g., the theory of aberrations, we are exploring semiclassical image formation in the TEM from the perspective of quantum mechanical phase space, here. Firstly, we use two well-known semiclassical approximations, Miller's semiclassical algebra and the frozen Gaussian method, for describing the wave optical generalization of arbitrary geometric aberrations, including nonisoplanatic and slope aberrations. Secondly, we demonstrate that the Wigner function representation of phase space is well suited to also describe incoherent aberrations as well as the ramifications of partial coherence due to the emission process at the electron source. We identify a close relationship between classical phase space and Wigner function distortions due to aberrations as well as classical brightness and quantum mechanical purity. PMID:25579179
Phase retrieval in in-line x-ray phase contrast imaging based on total variation
van Vliet, Lucas J.
Phase retrieval in in-line x-ray phase contrast imaging based on total variation minimization X-ray phase-contrast imaging are aiming to solve an underdetermined linear system of equations of America OCIS codes: (110.7440) X-ray imaging; (100.5070) Phase retrieval; (100.3190) Inverse prob- lems
TO BE SUBMITTED TO IEEE TRANSACTIONS ON IMAGE PROCESSING 1 Image Estimation using Interscale Phase
Kingsbury, Nick
complex, wavelet, image modelling, interscale, estimation, denoising, derotated, derotation, I an approach to image modelling using interscale phase relationships of wavelet coefficients for use in image. INTRODUCTION Wavelet transforms have emerged as a popular basis for photographic image modelling
Desmond C. Adler; Robert Huber; James G. Fujimoto
2007-01-01
Buffered Fourier domain mode-locked (FDML) lasers are demonstrated for dynamic phase-sensitive optical coherence tomography (OCT) and 3D OCT phase microscopy. Systems are operated at sweep speeds of 42, 117, and 370 kHz, and displacement sensitivities of 39, 52, and 102 pm are achieved, respectively. Sensitivities are comparable to spectrometer-based OCT phase microscopy systems, but much faster acquisition speeds are possible.
Automated Processing of Shoeprint Images Based on the Fourier Transform for Use in Forensic Science
Philip De Chazal; John Flynn; Richard B. Reilly
2005-01-01
The development of a system for automatically sorting a database of shoeprint images based on the outsole pattern in response to a reference shoeprint image is presented. The database images are sorted so that those from the same pattern group as the reference shoeprint are likely to be at the start of the list. A database of 476 complete shoeprint
Reconstructing MR images from incomplete Fourier data using the maximum entropy method
NASA Astrophysics Data System (ADS)
Fielden, John; Kwong, Henry Y.; Wilbrink, Jacob
1991-06-01
Frequently MRI data does not cover completely the desired region of k space. We have investigated the reconstruction of MR images from incomplete data using the MEMSYS 3 maximum entropy algorithm. We compare conventional modulus images with the maximum entropy images. We show the importance of incorporating spatial correlation into the maximum entropy reconstructions in order to minimize truncation artifacts.
Seet, Katrina Y T; Nieminen, Timo A; Zvyagin, Andrei V
2009-01-01
The cell nucleus is the dominant optical scatterer in the cell. Neoplastic cells are characterized by cell nucleus polymorphism and polychromism-i.e., the nuclei exhibits an increase in the distribution of both size and refractive index. The relative size parameter, and its distribution, is proportional to the product of the nucleus size and its relative refractive index and is a useful discriminant between normal and abnormal (cancerous) cells. We demonstrate a recently introduced holographic technique, digital Fourier microscopy (DFM), to provide a sensitive measure of this relative size parameter. Fourier holograms were recorded and optical scatter of individual scatterers were extracted and modeled with Mie theory to determine the relative size parameter. The relative size parameter of individual melanocyte cell nuclei were found to be 16.5+/-0.2, which gives a cell nucleus refractive index of 1.38+/-0.01 and is in good agreement with previously reported data. The relative size parameters of individual malignant melanocyte cell nuclei are expected to be greater than 16.5. PMID:19725742
Potsaid, Benjamin; Gorczynska, Iwona; Srinivasan, Vivek J.; Chen, Yueli; Jiang, James; Cable, Alex; Fujimoto, James G.
2009-01-01
We demonstrate ultrahigh speed spectral / Fourier domain optical coherence tomography (OCT) using an ultrahigh speed CMOS line scan camera at rates of 70,000 - 312,500 axial scans per second. Several design configurations are characterized to illustrate trade-offs between acquisition speed, resolution, imaging range, sensitivity and sensitivity roll-off performance. Ultrahigh resolution OCT with 2.5 - 3.0 micron axial image resolution is demonstrated at ? 100,000 axial scans per second. A high resolution spectrometer design improves sensitivity roll-off and imaging range performance, trading off imaging speed to 70,000 axial scans per second. Ultrahigh speed imaging at >300,000 axial scans per second with standard image resolution is also demonstrated. Ophthalmic OCT imaging of the normal human retina is investigated. The high acquisition speeds enable dense raster scanning to acquire densely sampled volumetric three dimensional OCT (3D-OCT) data sets of the macula and optic disc with minimal motion artifacts. Imaging with ? 8 - 9 micron axial resolution at 250,000 axial scans per second, a 512 × 512 × 400 voxel volumetric 3D-OCT data set can be acquired in only ? 1.3 seconds. Orthogonal registration scans are used to register OCT raster scans and remove residual axial eye motion, resulting in 3D-OCT data sets which preserve retinal topography. Rapid repetitive imaging over small volumes can visualize small retinal features without motion induced distortions and enables volume registration to remove eye motion. Cone photoreceptors in some regions of the retina can be visualized without adaptive optics or active eye tracking. Rapid repetitive imaging of 3D volumes also provides dynamic volumetric information (4D-OCT) which is shown to enhance visualization of retinal capillaries and should enable functional imaging. Improvements in the speed and performance of 3D-OCT volumetric imaging promise to enable earlier diagnosis and improved monitoring of disease progression and response to therapy in ophthalmology, as well as have a wide range of research and clinical applications in other areas. PMID:18795054
Quantitative phase imaging with programmable illumination
NASA Astrophysics Data System (ADS)
Kim, Taewoo; Edwards, Chris; Goddard, Lynford L.; Popescu, Gabriel
2015-03-01
Even with the recent rapid advances in the field of microscopy, non-laser light sources used for light microscopy have not been developing significantly. Most current optical microscopy systems use halogen bulbs as their light sources to provide a white-light illumination. Due to the confined shapes and finite filament size of the bulbs, little room is available for modification in the light source, which prevents further advances in microscopy. By contrast, commercial projectors provide a high power output that is comparable to the halogen lamps while allowing for great flexibility in patterning the illumination. In addition to their high brightness, the illumination can be patterned to have arbitrary spatial and spectral distributions. Therefore, commercial projectors can be adopted as a flexible light source to an optical microscope by careful alignment to the existing optical path. In this study, we employed a commercial projector source to a quantitative phase imaging system called spatial light interference microscopy (SLIM), which is an outside module for an existing phase contrast (PC) microscope. By replacing the ring illumination of PC with a ring-shaped pattern projected onto the condenser plane, we were able to recover the same result as the original SLIM. Furthermore, the ring illumination is replaced with multiple dots aligned along the same ring to minimize the overlap between the scattered and unscattered fields. This new method minimizes the halo artifact of the imaging system, which allows for a halo-free high-resolution quantitative phase microscopy system.
Double random phase encryption scheme to multiplex and simultaneous encode multiple images.
Alfalou, Ayman; Mansour, Ali
2009-11-01
Here we present a new approach of multiplexing and simultaneous encoding of target images. Our approach can enhance the encryption level of a classical double random phase (DRP) encryption system by adding a supplementary security layer. The new approach can be divided into two security layers. The first layer is called the multiplexing level, which consists in using iterative Fourier transformations along with several encryption key images. These latter can be a set of biometric images. At the second layer, we use a classical DRP system. The two layers enable us to encode several target images (multi-encryption) and to reduce, at the same time, the requested decoded information (transmitted or storage information). PMID:19881661
A simple public-key attack on phase-truncation-based double-images encryption system
NASA Astrophysics Data System (ADS)
Ding, Xiangling; Yang, Gaobo; He, Dajiang
2015-07-01
Phase-truncation based double-images cryptosystem can avoid the iterative Fourier transforms and realize double-images encryption. In this paper, a simple public-key attack is proposed to break this cryptosystem by using arbitrary position parameters and three public keys. The attack process is composed of two steps. Firstly, the decryption keys are simply generated with the help of arbitrary position parameters and the three public keys. Secondly, the two approximate values of the original images are obtained by using the generated decryption keys. Moreover, the proposed public-key attack is different from the existing attacks. It is not sensitive to position parameters of the double-images and the computing efficiency is also much better. Computer simulation results further prove its vulnerability.
Phased Contrast X-Ray Imaging (Image of Erin Miller, Ph.D.)
Transcript Phased Contrast X-Ray Imaging 1 TRANSCRIPT (Image of Erin Miller, Ph.D.) Erin A. Miller Contrast X-Ray Imaging; we're hoping to use it for enhanced explosives detection. (Images of empty airport security checkpoint, screenshot of Phased Contrast X-ray image, cardboard shipping boxes, suitcases, vials
Structure solution by minimal-function phase refinement and Fourier filtering. I. Theoretical basis.
DeTitta, G T; Weeks, C M; Thuman, P; Miller, R; Hauptman, H A
1994-03-01
Eliminating the N atomic position vectors rj, j = 1, 2, ..., N, from the system of equations defining the normalized structure factors EH yields a system of identities that the EH's must satisfy, provided that the set of EH's is sufficiently large. Clearly, for fixed N and specified space group, this system of identities depends only on the set [H], consisting of n reciprocal-lattice vectors H, and is independent of the crystal structure, which is assumed for simplicity to consist of N identical atoms per unit cell. However, for a fixed crystal structure, the magnitudes magnitude of /EH/ are uniquely determined so that a system of identities is obtained among the corresponding phases psi H alone, which depends on the presumed known magnitudes magnitude of /EH/ and which must of necessity be satisfied. The known conditional probability distributions of triplets and quartets, given the values of certain magnitudes magnitude of /E/, lead to a function R(psi) of phases, uniquely determined by magnitudes magnitude of /E/ and having the property that RT < 1/2 < RR, where RT is the value of R(psi) when the phases are equal to their true values, no matter what the choice of origin and enantiomorph, and RR is the value of R(psi) when the phases are chosen at random. The following conjecture is therefore plausible: the global minimum of R(psi), where the phases are constrained to satisfy all identities among them that are known to exist, is attained when the phases are equal to their true values and is thus equal to RT.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:8166951
NASA Astrophysics Data System (ADS)
Tremblay, Pierre; Gross, Kevin C.; Farley, Vincent; Chamberland, Martin; Villemaire, André; Perram, Glen P.
2009-08-01
Jet engine exhaust radiates strongly in the midwave infrared due to line emission from combustion byproducts such as CO2, CO, and H2O. Imaging Fourier-transform spectrometers (IFTS) have the potential to measure spatial variations in plume temperature and density. However, the turbulent flow yields rapid, stochastic fluctuations in radiance during interferometric measurements which corrupt corresponding spectra. A novel, statistics-based method of interpreting a time-sequence of interferograms collected from a stochastic blackbody source is presented which enables good estimation of the underlying temperature distribution. It is shown that the median (and various other quantiles) interferograms afford unbiased spectral estimates of temperature upon Fourier transformation, in contrast to temperature estimates based on spectra obtained from mean interferograms. This method is then applied to IFTS data (200×64 pixels at 1cm-1 resolution) of a turbulent exhaust plume from a small turbojet engine. Spatial maps of brightness temperature and estimates of turbulence-induced temperature distribution are presented.
PHASED ARRAY FEED CALIBRATION, BEAMFORMING, AND IMAGING
Landon, Jonathan; Elmer, Michael; Waldron, Jacob; Jones, David; Stemmons, Alan; Jeffs, Brian D.; Warnick, Karl F. [Department of Electrical and Computer Engineering, Brigham Young University, 459 Clyde Building, Provo, UT 84602 (United States); Richard Fisher, J. [National Radio Astronomy Observatory, Charlottesville, VA (United States); Norrod, Roger D. [National Radio Astronomy Observatory, Green Bank, WV (United States)
2010-03-15
Phased array feeds (PAFs) for reflector antennas offer the potential for increased reflector field of view and faster survey speeds. To address some of the development challenges that remain for scientifically useful PAFs, including calibration and beamforming algorithms, sensitivity optimization, and demonstration of wide field of view imaging, we report experimental results from a 19 element room temperature L-band PAF mounted on the Green Bank 20 Meter Telescope. Formed beams achieved an aperture efficiency of 69% and a system noise temperature of 66 K. Radio camera images of several sky regions are presented. We investigate the noise performance and sensitivity of the system as a function of elevation angle with statistically optimal beamforming and demonstrate cancelation of radio frequency interference sources with adaptive spatial filtering.
Self-starting, self-regulating Fourier domain mode locked fiber laser for OCT imaging.
Murari, Kartikeya; Mavadia, Jessica; Xi, Jiefeng; Li, Xingde
2011-07-01
We present a Fourier domain mode locking (FDML) fiber laser with a feedback loop allowing automatic startup without a priori knowledge of the fundamental drive frequency. The feedback can also regulate the drive frequency making the source robust against environmental variations. A control system samples the energy of the light traversing the FDML cavity and uses a voltage controlled oscillator (VCO) to drive the tunable fiber Fabry-Perot filter in order to maximize that energy. We demonstrate a prototype self-starting, self-regulating FDML operating at 40 kHz with a full width tuning range of 140 nm around 1305 nm and a power output of ~40 mW. The laser starts up with no operator intervention in less than 5 seconds and exhibits improved spectral stability over a conventional FDML source. In OCT applications the source achieved over 120 dB detection sensitivity and an ~8.9-µm axial resolution. PMID:21750775
Self-starting, self-regulating Fourier domain mode locked fiber laser for OCT imaging
Murari, Kartikeya; Mavadia, Jessica; Xi, Jiefeng; Li, Xingde
2011-01-01
We present a Fourier domain mode locking (FDML) fiber laser with a feedback loop allowing automatic startup without a priori knowledge of the fundamental drive frequency. The feedback can also regulate the drive frequency making the source robust against environmental variations. A control system samples the energy of the light traversing the FDML cavity and uses a voltage controlled oscillator (VCO) to drive the tunable fiber Fabry-Perot filter in order to maximize that energy. We demonstrate a prototype self-starting, self-regulating FDML operating at 40 kHz with a full width tuning range of 140 nm around 1305 nm and a power output of ~40 mW. The laser starts up with no operator intervention in less than 5 seconds and exhibits improved spectral stability over a conventional FDML source. In OCT applications the source achieved over 120 dB detection sensitivity and an ~8.9-µm axial resolution. PMID:21750775
2013-01-01
Coupling Fourier transform infrared spectroscopy with focal plane array detectors at synchrotron radiation sources (SR-FTIR-FPA) has provided a rapid method to simultaneously image numerous biochemical markers in situ at diffraction limited resolution. Since cells and nuclei are well resolved at this spatial resolution, a direct comparison can be made between FTIR functional group images and the histology of the same section. To allow histological analysis of the same section analyzed with infrared imaging, unfixed air-dried tissue sections are typically fixed (after infrared spectroscopic analysis is completed) via immersion fixation. This post fixation process is essential to allow histological staining of the tissue section. Although immersion fixation is a common practice in this filed, the initial rehydration of the dehydrated unfixed tissue can result in distortion of subcellular morphology and confound correlation between infrared images and histology. In this study, vapor fixation, a common choice in other research fields where postfixation of unfixed tissue sections is required, was employed in place of immersion fixation post spectroscopic analysis. This method provided more accurate histology with reduced distortions as the dehydrated tissue section is fixed in vapor rather than during rehydration in an aqueous fixation medium. With this approach, accurate correlation between infrared images and histology of the same section revealed that Purkinje neurons in the cerebellum are rich in cytosolic proteins and not depleted as once thought. In addition, we provide the first direct evidence of intracellular lactate within Purkinje neurons. This highlights the significant potential for future applications of SR-FTIR-FPA imaging to investigate cellular lactate under conditions of altered metabolic demand such as increased brain activity and hypoxia or ischemia. PMID:23638613
Hackett, Mark J; Borondics, Ferenc; Brown, Devin; Hirschmugl, Carol; Smith, Shari E; Paterson, Phyllis G; Nichol, Helen; Pickering, Ingrid J; George, Graham N
2013-07-17
Coupling Fourier transform infrared spectroscopy with focal plane array detectors at synchrotron radiation sources (SR-FTIR-FPA) has provided a rapid method to simultaneously image numerous biochemical markers in situ at diffraction limited resolution. Since cells and nuclei are well resolved at this spatial resolution, a direct comparison can be made between FTIR functional group images and the histology of the same section. To allow histological analysis of the same section analyzed with infrared imaging, unfixed air-dried tissue sections are typically fixed (after infrared spectroscopic analysis is completed) via immersion fixation. This post fixation process is essential to allow histological staining of the tissue section. Although immersion fixation is a common practice in this filed, the initial rehydration of the dehydrated unfixed tissue can result in distortion of subcellular morphology and confound correlation between infrared images and histology. In this study, vapor fixation, a common choice in other research fields where postfixation of unfixed tissue sections is required, was employed in place of immersion fixation post spectroscopic analysis. This method provided more accurate histology with reduced distortions as the dehydrated tissue section is fixed in vapor rather than during rehydration in an aqueous fixation medium. With this approach, accurate correlation between infrared images and histology of the same section revealed that Purkinje neurons in the cerebellum are rich in cytosolic proteins and not depleted as once thought. In addition, we provide the first direct evidence of intracellular lactate within Purkinje neurons. This highlights the significant potential for future applications of SR-FTIR-FPA imaging to investigate cellular lactate under conditions of altered metabolic demand such as increased brain activity and hypoxia or ischemia. PMID:23638613
IFTSUV: an imaging Fourier transform spectrometer in UV for the next solar space missions
Anne A. Millard; Philippe Lemaire; Jean-Claude Vial
2006-01-01
The study of the Sun in the UV spectral domain is essential for a better understanding of the physical processes taking place in the solar atmosphere. The main tools for this study are imagers and spectrometers. Nevertheless, the analysis of imagery data is rapidly limited unless spectral information is available, and the association of spectrometers and imagers is limited by
Yin, Jianhua; Xia, Yang
2014-12-10
Fourier transform infrared imaging (FTIRI) combining with principal component regression (PCR) analysis were used to determine the reduction of proteoglycan (PG) in articular cartilage after the transection of the anterior cruciate ligament (ACL). A number of canine knee cartilage sections were harvested from the meniscus-covered and meniscus-uncovered medial tibial locations from the control joints, the ACL joints at three time points after the surgery, and their contralateral joints. The PG loss in the ACL cartilage was related positively to the durations after the surgery. The PG loss in the contralateral knees was less than that of the ACL knees. The PG loss in the meniscus-covered cartilage was less than that of the meniscus-uncovered tissue in both ACL and contralateral knees. The quantitative mapping of PG loss could monitor the disease progression and repair processes in arthritis. PMID:25000570
Fourier Spectral Method for Shape Asymmetry Analysis
Wisconsin at Madison, University of
Fourier Spectral Method for Shape Asymmetry Analysis Moo K. Chung Department of Biostatistics idea and Brechbuler's 3D Fourier descriptor. Surface shape registration,surface data smoothing population asymmetry analysis framework Clinical population Normal controls template image registration image
Adaptive spatial-division split-step fourier migration method
Jingxia Zhao; Shulun Zhang; Changlong Wang; Yi Ni
2005-01-01
This paper presents a new depth migration method, adaptive spatial-division split-step Fourier (ASDSSF) migration. In this\\u000a method we introduce the idea of a stratified phase shift migration into the split-step Fourier (SSF) migration to make an\\u000a accurate and efficient wave field image when sharp discontinuities appear in the velocity field. In principle, the ASDSSF\\u000a migration is a multi-reference slowness (reciprocal
Irvine, S; Mokso, R; Modregger, P; Wang, Z; Marone, F; Stampanoni, M
2014-11-01
For dynamic samples and/or for simple ease-of-use experiments, single-image phase contrast tomography is a very effective method for the 3D visualization of materials which would otherwise be indiscernible in attenuation based x-ray imaging. With binary samples (e.g. air-material) and monochromatic wavefields a transport-of-intensity (TIE)-based phase retrieval algorithm is known to retrieve accurate quantitative maps of the phase distribution. For mixed material samples and/or white beam radiation the algorithm can still produce useful qualitative tomographic reconstructions with significantly improved area contrast. The stability of the algorithm comes with a recognized associated loss of spatial resolution due to its essential behaviour as a low-pass filter. One possible answer to this is an image fusion technique that merges the slices reconstructed from raw phase contrast images and those after phase retrieval, where the improved contrast may be acquired without the associated loss of high-frequency information. We present this technique as a simple few-parameter Fourier method, which is easily tunable and highly compatible with current reconstruction steps. PMID:25401876
NASA Technical Reports Server (NTRS)
Zhou, Daniel K.; Smith, William L.; Bingham, Gail E.; Huppi, Ronald J.; Revercomb, Henry E.; Zollinger, Lori J.; Larar, Allen M.; Liu, Xu; Tansock, Joseph J.; Reisse, Robert A.; Hooker, Ronald
2007-01-01
The geosynchronous-imaging Fourier transform spectrometer (GIFTS) engineering demonstration unit (EDU) is an imaging infrared spectrometer designed for atmospheric soundings. It measures the infrared spectrum in two spectral bands (14.6 to 8.8 microns, 6.0 to 4.4 microns) using two 128 x 128 detector arrays with a spectral resolution of 0.57 cm(exp -1) with a scan duration of approximately 11 seconds. From a geosynchronous orbit, the instrument will have the capability of taking successive measurements of such data to scan desired regions of the globe, from which atmospheric status, cloud parameters, wind field profiles, and other derived products can be retrieved. The GIFTS EDU provides a flexible and accurate testbed for the new challenges of the emerging hyperspectral era. The EDU ground-based measurement experiment, held in Logan, Utah during September 2006, demonstrated its extensive capabilities and potential for geosynchronous and other applications (e.g., Earth observing environmental measurements). This paper addresses the experiment objectives and overall performance of the sensor system with a focus on the GIFTS EDU imaging capability and proof of the GIFTS measurement concept.
Testing results and current status of FTS-2, an imaging Fourier transform spectrometer for SCUBA-2
Naylor, David A.
-Zehnder imaging spectrometer, built for use with the SCUBA-2 camera on the James Clerk Maxwell Telescope (JCMT (FTS) which has been built for use with the SCUBA-2 camera1 on the James Clerk Maxwell Telescope (JCMT
Milad Hashemi; Michael Hegg; Babak A. Parviz; Lih Y. Lin
2008-01-01
With the advance of nano-lithography and nano-fabrication, individual sizes of electronic, photonic, and mechanical components, as well as their integration densities, have progressed steadily towards the sub-100 nm regime. Therefore, being able to image such feature sizes becomes imperative. Many conventional high-resolution imaging tools such as SEM, STM, AFM, and NSOM either require operation under high vacuum or slow scanning
Phase correction of image plane in holographic microscopy with equal-step phase shift
NASA Astrophysics Data System (ADS)
Zhao, Hong-bo; Zhou, Hao; Tai, Fang-fang; Gu, Ji-hua
2014-02-01
A method which can compensate the phase curvature of image plane in equal-step phase-shifting holographic microscopy is presented. Recording two holograms before and after inserting the sample, unwrapping the numerical reconstructed images of the two holograms respectively and subtracting them each other, the corrected phase distribution of the sample is obtained. Firstly, the imaging characteristics of in-line phase-shifting holographic system in the image plane was analyzed. Secondly, onionskin cells and USAF1951 test target were recorded and reconstructed by this method. It is shown that high quality imaging of phase objects can be achieved by proposed method.
Chowdhury, Shwetadwip; Izatt, Joseph
2013-01-01
Structured illumination microscopy (SIM) is an established microscopy technique typically used to image samples at resolutions beyond the diffraction limit. Until now, however, achieving sub-diffraction resolution has predominantly been limited to intensity-based imaging modalities. Here, we introduce an analogue to conventional SIM that allows sub-diffraction resolution, quantitative phase-contrast imaging of optically transparent objects. We demonstrate sub-diffraction resolution amplitude and quantitative-phase imaging of phantom targets and enhanced resolution quantitative-phase imaging of cells. We report a phase accuracy to within 5% and phase noise of 0.06 rad. PMID:24156044
Analysis of hyper-spectral data derived from an imaging Fourier transform: A statistical perspective
Sengupta, S.K.; Clark, G.A.; Fields, D.J.
1996-01-10
Fourier transform spectrometers (FTS) using optical sensors are increasingly being used in various branches of science. Typically, a FTS generates a three-dimensional data cube with two spatial dimensions and one frequency/wavelength dimension. The number of frequency dimensions in such data cubes is generally very large, often in the hundreds, making data analytical procedures extremely complex. In the present report, the problem is viewed from a statistical perspective. A set of procedures based on the high degree of inter-channel correlation structure often present in such hyper-spectral data, has been identified and applied to an example data set of dimension 100 x 128 x 128 comprising 128 spectral bands. It is shown that in this case, the special eigen-structure of the correlation matrix has allowed the authors to extract just a few linear combinations of the channels (the significant principal vectors) that effectively contain almost all of the spectral information contained in the data set analyzed. This in turn, enables them to segment the objects in the given spatial frame using, in a parsimonious yet highly effective way, most of the information contained in the data set.
Weeks, C M; DeTitta, G T; Hauptman, H A; Thuman, P; Miller, R
1994-03-01
The minimal function, R(psi), has been used to provide the basis for a new computer-intensive direct-methods procedure that shows potential for providing fully automatic routine solutions for structures in the 200-400 atom range. This procedure, which has been called shake-and-bake, is an iterative process in which real-space filtering is alternated with phase refinement using a technique that reduces the value of R(psi). It has been successfully tested using experimental data for a dozen known structures ranging in size from 25 to 317 atoms and crystallizing in a variety of space groups. The details of this procedure, the parameters used and the results of these applications are described. PMID:8166952
Real-time measurement of alveolar size and population using phase contrast x-ray imaging
Leong, Andrew F.T.; Buckley, Genevieve A.; Paganin, David M.; Hooper, Stuart B.; Wallace, Megan J.; Kitchen, Marcus J.
2014-01-01
Herein a propagation-based phase contrast x-ray imaging technique for measuring particle size and number is presented. This is achieved with an algorithm that utilizes the Fourier space signature of the speckle pattern associated with the images of particles. We validate this algorithm using soda-lime glass particles, demonstrating its effectiveness on random and non-randomly packed particles. This technique is then applied to characterise lung alveoli, which are difficult to measure dynamically in vivo with current imaging modalities due to inadequate temporal resolution and/or depth of penetration and field-of-view. We obtain an important result in that our algorithm is able to measure changes in alveolar size on the micron scale during ventilation and shows the presence of alveolar recruitment/de-recruitment in newborn rabbit kittens. This technique will be useful for ventilation management and lung diagnostic procedures. PMID:25426328
NASA Technical Reports Server (NTRS)
Dennis, Brian R.; Crannell, Carol JO; Desai, Upendra D.; Orwig, Larry E.; Kiplinger, Alan L.; Schwartz, Richard A.; Hurford, Gordon J.; Emslie, A. Gordon; Machado, Marcos; Wood, Kent
1988-01-01
The Fourier Imaging X-ray Spectrometer (FIXS) is one of four instruments on SAC-1, the Argentinian satellite being proposed for launch by NASA on a Scout rocket in 1992/3. The FIXS is designed to provide solar flare images at X-ray energies between 5 and 35 keV. Observations will be made on arcsecond size scales and subsecond time scales of the processes that modify the electron spectrum and the thermal distribution in flaring magnetic structures.
Ultrahigh Speed Imaging of the Rat Retina Using Ultrahigh Resolution Spectral/Fourier Domain OCT
Liu, Jonathan Jaoshin
We performed OCT imaging of the rat retina at 70,000 axial scans per second with ~3 ?m axial resolution. Three-dimensional OCT (3D-OCT) data sets of the rat retina were acquired. The high speed and high density data sets ...
Jialin Tian; William L. Smith; Michael J. Gazarik
2008-01-01
The ultimate remote sensing benefits of the high resolution Infrared radiance spectrometers will be realized with their geostationary satellite implementation in the form of imaging spectrometers. This will enable dynamic features of the atmosphere's thermodynamic fields and pollutant and greenhouse gas constituents to be observed for revolutionary improvements in weather forecasts and more accurate air quality and climate predictions. As
Multiple moving targets ISAR imaging based on discrete match fourier transformation
Yanan Li; Yuping Jia; Yaowen Fu; Xiang Li
2008-01-01
When multiple moving targets are close to each other, the returned signals from these targets are overlapped in time. Therefore, by applying conventional motion compensation algorithms designed for single target, the multiple targets cannot be resolved, and individual one cannot be clearly imaged. However, each individual target may have its own velocity different from others. The translational motion can be
Aizikov, Konstantin; Lin, Tzu-Yung [Cardiovascular Proteomics Center, Boston University School of Medicine, 670 Albany Street, Room 504 Boston, Massachusetts 02118 (United States); Department of Electrical and Computer Engineering, Boston University, Boston, Massachusetts 02215 (United States); Smith, Donald F.; Heeren, Ron M. A. [FOM Institute for Atomic and Molecular Physics (AMOLF), Science Park 104, 1098 XG Amsterdam (Netherlands); Chargin, David A.; Ivanov, Sergei [Fraunhofer CMI, Boston, Massachusetts 02215 (United States); O'Connor, Peter B. [Cardiovascular Proteomics Center, Boston University School of Medicine, 670 Albany Street, Room 504 Boston, Massachusetts 02118 (United States); Department of Electrical and Computer Engineering, Boston University, Boston, Massachusetts 02215 (United States); Department of Chemistry, University of Warwick, Coventry CV4 7AL (United Kingdom)
2011-05-15
The high mass accuracy and resolving power of Fourier transform ion cyclotron resonance mass spectrometers (FT-ICR MS) make them ideal mass detectors for mass spectrometry imaging (MSI), promising to provide unmatched molecular resolution capabilities. The intrinsic low tolerance of FT-ICR MS to RF interference, however, along with typically vertical positioning of the sample, and MSI acquisition speed requirements present numerous engineering challenges in creating robotics capable of achieving the spatial resolution to match. This work discusses a two-dimensional positioning stage designed to address these issues. The stage is capable of operating in {approx}1 x 10{sup -8} mbar vacuum. The range of motion is set to 100 mm x 100 mm to accommodate large samples, while the positioning accuracy is demonstrated to be less than 0.4 micron in both directions under vertical load over the entire range. This device was integrated into three different matrix assisted laser desorption/ionization (MALDI) FT-ICR instruments and showed no detectable RF noise. The ''oversampling'' MALDI-MSI experiments, under which the sample is completely ablated at each position, followed by the target movement of the distance smaller than the laser beam, conducted on the custom-built 7T FT-ICR MS demonstrate the stability and positional accuracy of the stage robotics which delivers high spatial resolution mass spectral images at a fraction of the laser spot diameter.
NASA Astrophysics Data System (ADS)
Aizikov, Konstantin; Smith, Donald F.; Chargin, David A.; Ivanov, Sergei; Lin, Tzu-Yung; Heeren, Ron M. A.; O'Connor, Peter B.
2011-05-01
The high mass accuracy and resolving power of Fourier transform ion cyclotron resonance mass spectrometers (FT-ICR MS) make them ideal mass detectors for mass spectrometry imaging (MSI), promising to provide unmatched molecular resolution capabilities. The intrinsic low tolerance of FT-ICR MS to RF interference, however, along with typically vertical positioning of the sample, and MSI acquisition speed requirements present numerous engineering challenges in creating robotics capable of achieving the spatial resolution to match. This work discusses a two-dimensional positioning stage designed to address these issues. The stage is capable of operating in ˜1 × 10-8 mbar vacuum. The range of motion is set to 100 mm × 100 mm to accommodate large samples, while the positioning accuracy is demonstrated to be less than 0.4 micron in both directions under vertical load over the entire range. This device was integrated into three different matrix assisted laser desorption/ionization (MALDI) FT-ICR instruments and showed no detectable RF noise. The "oversampling" MALDI-MSI experiments, under which the sample is completely ablated at each position, followed by the target movement of the distance smaller than the laser beam, conducted on the custom-built 7T FT-ICR MS demonstrate the stability and positional accuracy of the stage robotics which delivers high spatial resolution mass spectral images at a fraction of the laser spot diameter.
Dispersion control with a Fourier-domain optical delay line in a fiber-optic imaging interferometer.
Lee, Kye-Sung; Akcay, A Ceyhun; Delemos, Tony; Clarkson, Eric; Rolland, Jannick P
2005-07-01
Recently, Fourier-domain (FD) optical delay lines (ODLs) were introduced for high-speed scanning and dispersion compensation in imaging interferometry. We investigate the effect of first- and second-order dispersion on the photocurrent signal associated with an optical coherence imaging system implemented with a single-mode fiber, a superluminescent diode centered at 950 nm +/- 35 nm, a FD ODL, a mirror, and a layered LiTAO3 that has suitable dispersion characteristics to model a skin specimen. We present a practical and useful method to minimize the effect of dispersion through the interferometer and the specimen combined, as well as to quantify the results using two general metrics for resolution. Theoretical and associated experimental results show that, under the optimum solution, the maximum broadening of the point-spread function through a 1-mm-deep specimen is limited to 57% of its original rms width value (i.e., 8.1 microm optimal, 12.7 microm at maximum broadening) compared with approximately 110% when compensation is performed without the specimen taken into account. PMID:16004048
NASA Astrophysics Data System (ADS)
Sreedhar, Hari; Pant, Mamta; Ronquillo, Nemencio R.; Davidson, Bennett; Nguyen, Peter; Chennuri, Rohini; Choi, Jacqueline; Herrera, Joaquin A.; Hinojosa, Ana C.; Jin, Ming; Kajdacsy-Balla, Andre; Guzman, Grace; Walsh, Michael J.
2014-03-01
Hepatocellular carcinoma (HCC) is the most common form of primary hepatic carcinoma. HCC ranks the fourth most prevalent malignant tumor and the third leading cause of cancer related death in the world. Hepatocellular carcinoma develops in the context of chronic liver disease and its evolution is characterized by progression through intermediate stages to advanced disease and possibly even death. The primary sequence of hepatocarcinogenesis includes the development of cirrhosis, followed by dysplasia, and hepatocellular carcinoma.1 We addressed the utility of Fourier Transform Infrared (FT-IR) spectroscopic imaging, both as a diagnostic tool of the different stages of the disease and to gain insight into the biochemical process associated with disease progression. Tissue microarrays were obtained from the University of Illinois at Chicago tissue bank consisting of liver explants from 12 transplant patients. Tissue core biopsies were obtained from each explant targeting regions of normal, liver cell dysplasia including large cell change and small cell change, and hepatocellular carcinoma. We obtained FT-IR images of these tissues using a modified FT-IR system with high definition capabilities. Firstly, a supervised spectral classifier was built to discriminate between normal and cancerous hepatocytes. Secondly, an expanded classifier was built to discriminate small cell and large cell changes in liver disease. With the emerging advances in FT-IR instrumentation and computation there is a strong drive to develop this technology as a powerful adjunct to current histopathology approaches to improve disease diagnosis and prognosis.
Ultrasonic Backscatter Imaging by Shear-Wave-Induced Echo Phase Encoding of Target Locations
McAleavey, Stephen
2011-01-01
We present a novel method for ultrasound backscatter image formation wherein lateral resolution of the target is obtained by using traveling shear waves to encode the lateral position of targets in the phase of the received echo. We demonstrate that the phase modulation as a function of shear wavenumber can be expressed in terms of a Fourier transform of the lateral component of the target echogenicity. The inverse transform, obtained by measurements of the phase modulation over a range of shear wave spatial frequencies, yields the lateral scatterer distribution. Range data are recovered from time of flight as in conventional ultrasound, yielding a B-mode-like image. In contrast to conventional ultrasound imaging, where mechanical or electronic focusing is used and lateral resolution is determined by aperture size and wavelength, we demonstrate that lateral resolution using the proposed method is independent of the properties of the aperture. Lateral resolution of the target is achieved using a stationary, unfocused, single-element transducer. We present simulated images of targets of uniform and non-uniform shear modulus. Compounding for speckle reduction is demonstrated. Finally, we demonstrate image formation with an unfocused transducer in gelatin phantoms of uniform shear modulus. PMID:21244978
McAleavey, Stephen A.
2014-01-01
Shear wave induced phase encoding (SWIPE) imaging generates ultrasound backscatter images of tissue-like elastic materials by using traveling shear waves to encode the lateral position of the scatters in the phase of the received echo. In contrast to conventional ultrasound B-scan imaging, SWIPE offers the potential advantages of image formation without beam focusing or steering from a single transducer element, lateral resolution independent of aperture size, and the potential to achieve relatively high lateral resolution with low frequency ultrasound. Here a Fourier series description of the phase modulated echo signal is developed, demonstrating that echo harmonics at multiples of the shear wave frequency reveal target k-space data at identical multiples of the shear wavenumber. Modulation transfer functions of SWIPE imaging systems are calculated for maximum shear wave acceleration and maximum shear constraints, and compared with a conventionally focused aperture. The relative signal-to-noise ratio of the SWIPE method versus a conventionally focused aperture is found through these calculations. Reconstructions of wire targets in a gelatin phantom using 1 and 3.5?MHz ultrasound and a cylindrical shear wave source are presented, generated from the fundamental and second harmonic of the shear wave modulation frequency, demonstrating weak dependence of lateral resolution with ultrasound frequency. PMID:24815265
Compression of periodic images for faster phase retrieval
Ribak, Erez
Compression of periodic images for faster phase retrieval Amos Talmi1 and Erez N. Ribak2, * 1 Timi the requirement to maintain the integrity of the original phase data. © 2010 Optical Society of America OCIS codes
NASA Astrophysics Data System (ADS)
George, K.; Ruthenburg, T. C.; Smith, J.; Anastasio, C.; Dillner, A. M.
2011-12-01
Particles in the atmosphere influence visibility, climate, and human health. Secondary organic aerosols (SOA) formed from chemical reactions in the atmosphere constitute a portion of total organic particle mass. Most research on SOA has focused on gas phase reactions; however, reactions taking place in cloud and fog drops may be significant. One group of water-soluble compounds that participate in these reactions is phenols. Phenols, emitted from biomass burning, react in the aqueous phase to form low-volatility SOA products. The products formed from these reactions are currently poorly characterized. In order to characterize laboratory-generated samples, we are developing an attenuated total reflectance-Fourier transform infrared spectroscopic (ATR-FTIR) technique to identify and quantify organic functional groups in SOA. Aqueous SOA is made in the laboratory by illuminating solutions of phenolic compounds with an oxidant. The illuminated solution is then blown to dryness in order to determine the mass of SOA produced. The dry SOA is reconstituted in water and drops of this solution are placed onto a single-reflection ATR accessory. In order to identify and quantify functional groups in the complex SOA samples, it is necessary to calibrate with compounds and mixtures of compounds containing bond types similar to those found in the laboratory-generated SOA. Initially, focus has been placed on multiple peaks located in the region between 1800 cm-1 and 800 cm-1, including peaks for C=O and C-O. We distinguish between characteristic absorbances to begin determining the organic functional group composition of the SOA samples. This ATR-FTIR technique complements information from mass spectrometry measurements and allows us to quantify organic mass for non-volatile SOA products.
Huakun Cui; Dayong Wang; Yunxin Wang; Changgeng Liu; Jie Zhao; Yan Li
2010-01-01
As the lensless Fourier transform digital holography is applied into the microscopic phase-contrast imaging on the live cells, the motion of the cells will lead to the non-coplanarity phenomena between the object and the reference source. This could result in the imaging aberration. An effective and robust autofocus procedure based on the phase distribution is presented in the paper. With
Computer-generated hologram of asymmetry fractional Fourier transform
NASA Astrophysics Data System (ADS)
Sheng, Zhaoxuan; Wang, Hongxia; He, Junfa; Zhou, Youjie; Wang, Jun; Mao, Cairong
2005-02-01
A new optical encryption technique based on computer-generated hologram (CGH) and fractional Fourier transform (FRT) is presented. And the algorithm of making asymmetry FRT CGH is provided in this paper. In this method, the fractional Fourier transform of the input image is performed by two one-dimensional FRT with different orders in the x and y directions in cascade. With Lohmann III detour phase encoding method and computer plotting program, the transformed image is encoded and fabricated into CGH on the computer. Then a piece of asymmetry fractional Fourier transform CGH (AFRTCGH) of original input image is obtained. In order to reconstruct the encoded image, a special fractional Fourier transform systems with two special cylinder lens" are needed. Namely, only when the transform order in each direction is respectively matched with that of the asymmetry fractional Fourier transform CGH, can the encoded image be reconstructed exactly. Because of its particularity of image reconstruction, it is regarded as a new optical security system and can be used in anti-counterfeiting. When it is used to encrypt image or to anti-Counterfeit, anti-counterfeiting intensity can be improved greatly. So it has very high applying value.
Digital image stabilization with sub-image phase correlation based global motion estimation
S. Erturk
2003-01-01
This paper presents digital image stabilization with sub-image phase correlation based global motion estimation and Kalman filtering based motion correction. Global motion is estimated from the local motions of four sub-images each of which is detected using phase correlation based motion estimation. The global motion vector is decided according to the peak values of sub-image phase correlation surfaces, instead of
Computer generated hologram for phase-only optical encryption
Tien Viet Vu; Nam Kim; Sang-Keun Gil; Jun-Won An; Eun-Kyong Kim
2007-01-01
An improved image encryption\\/decryption approach is proposed. In the encryption system, a binary amplitude image is encoded in the Fourier domain. Then, the encoded image is scrambled with a random binary phase image to produce the encrypted image. Both the encoding and encryption processes are done electronically. The encrypted image is stored in an encrypted phase mask of which the
NASA Astrophysics Data System (ADS)
Kohen, Elli; Hirschberg, Joseph G.; Berry, John P.; Ozkutuk, Nuri; Ornek, Ceren; Monti, Marco; Leblanc, Roger M.; Schachtschabel, Dietrich O.; Haroon, Sumaira
2003-10-01
Dual excitation fluorescence imaging has been used as a first step towards multi-wavelength excitation/emission fluorescence spectral imaging. Target cells are transformed keratinocytes, and other osteosarcoma, human breast and color cancer cells. Mitochondrial membrane potential probes, e.g. TMRM (tetramethylrhodamine methyl ester), Mitotracker Green (Molecular Probes, Inc., Eugene OR,USA; a recently synthesized mitochondrial oxygen probe, [PRE,P1"- pyrene butyl)-2-rhodamine ester] allow dual excitation in the UV plus in teh blue-green spectral regions. Also, using the natural endogenous probe NAD(P)H, preliminary results indicate mitochondrial responses to metabolic challenges (e.g. glucose addition), plus changes in mitochonrial distribution and morphology. In terms of application to biomedicine (for diagnostiscs, prognostsics and drug trials) three parameters have been selected in addition to the natural probe NAD(P)H, i.e. vital fluorescence probing of mitochondria, lysosomes and Golgi apparatus. It is hoped that such a multiparameter approach will allow malignant cell characterization and grading. A new area being introduced is the use of similar methodology for biotechnical applications such as the study of the hydrogen-producing alga Chlamydomonas Reinhardtii, and possible agricultural applications, such as Saccharomyces yeast for oenology. Complementation by Photoacoustic Microscopy is also contemplated, to study the internal conversion component which follows the excitation by photons.
Desmond C. Adler; Robert Huber; James G. Fujimoto
2007-01-01
Phase sensitive optical coherence tomography (OCT) can be used to obtain sub-nanometer displacement measurements of biological and non-biological samples. This technique has many applications, including detection of small amplitude surface motion, and high axial resolution OCT phase microscopy. Doppler OCT is another type of phase sensitive imaging, where differential phase measurements are used to detect fluid flow in biological specimens.
Phase contrast portal imaging for image-guided microbeam radiation therapy
NASA Astrophysics Data System (ADS)
Umetani, Keiji; Kondoh, Takeshi
2014-03-01
High-dose synchrotron microbeam radiation therapy is a unique treatment technique used to destroy tumors without severely affecting circumjacent healthy tissue. We applied a phase contrast technique to portal imaging in preclinical microbeam radiation therapy experiments. Phase contrast portal imaging is expected to enable us to obtain higherresolution X-ray images at therapeutic X-ray energies compared to conventional portal imaging. Frontal view images of a mouse head sample were acquired in propagation-based phase contrast imaging. The phase contrast images depicted edge-enhanced fine structures of the parietal bones surrounding the cerebrum. The phase contrast technique is expected to be effective in bony-landmark-based verification for image-guided radiation therapy.
Sparsity assisted solution to the twin image problem in phase retrieval
Gaur, Charu; Khare, Kedar
2015-01-01
The iterative phase retrieval problem for complex-valued objects from Fourier transform magnitude data is known to suffer from the twin image problem. In particular, when the object support is centro-symmetric, the iterative solution often stagnates such that the resultant complex image contains the features of both the desired solution and its inverted and complex-conjugated replica. The conventional approach to address the twin image problem is to modify the object support during initial iterations which can possibly lead to elimination of one of the twin images. However, at present there seems to be no deterministic procedure to make sure that the twin image will always be very weak or absent. In this work we make an important observation that the ideal solution without the twin image is typically more sparse (in some suitable transform domain) as compared to the stagnated solution containing the twin image. We further show that introducing a sparsity enhancing step in the iterative algorithm can address t...
Fogarty, Simon W; Patel, Imran I; Trevisan, Júlio; Nakamura, Takahiro; Hirschmugl, Carol J; Fullwood, Nigel J; Martin, Francis L
2013-01-01
Understanding stem cell (SC) biology remains challenging and one of the few human tissues within which their in situ location is well characterized is the cornea. Individual human corneal epithelial cells were isolated from biopsies of live tissues using fluorescence-activated cell sorting (FACS); these were divided into putative SCs, transit-amplifying (TA) cells and terminally-differentiated (TD) cells. Employing synchrotron radiation-based Fourier-transform infrared (SR-FTIR) microspectroscopy with a focal plane array (FPA), sub-cellular spatial resolution analysis of unstained isolated cells was achieved as a consequence of the brilliance of a 12 collimated beams arrangement allowing rapid spectral acquisition. Infrared (IR) spectra were extracted and pre-processed. Subsequent categorization with multivariate analysis of IR spectra derived from FPA images was used to investigate biomolecular changes between classes. A progressive segregation in cell-specific spectral categories with differentiation from SC to TA cell to TD cell was noted. Multiple different absorption peaks that discriminated putative SCs, TA cells and TD cells across DNA, protein and lipid spectral regions were identified. DNA regions (1080 and 1225 cm(-1)) and some protein regions (1443 cm(-1)) primarily segregated SCs from TA cells and TD cells, whilst amide regions and lipids (1,550, 1650 and 1740 cm(-1)) segregated TA cells and TD cells. Scanning electron microscopy images verified the external phenotypic characteristics of the different isolated cell types. These findings highlight the applicability of SR-FTIR microspectroscopy towards distinguishing SCs, TA cells and TD cells, and suggest that cellular classification via traditional methods of immunolabelling can be greatly aided by the use of spectral biomarkers. PMID:23152953
Reconstruction of the hologram structure from a digitally recorded Fourier specklegram
NASA Astrophysics Data System (ADS)
Gorbatenko, B. B.; Maksimova, L. A.; Ryabukho, V. P.
2009-02-01
The possibilities of reconstructing the hologram structure and image from a digitally recorded Fourier specklegram without reference beam have been considered. The mechanisms of recording in the hologram structure and reconstructing information about the amplitude and phase spatial distributions in optical fields are discussed. Schemes for recording Fourier specklegrams are considered. The results of reconstruction of the hologram structures and images of flat scattering objects of different shapes are presented.
A tilt-compensated Fourier transform spectrometer with an image rotator
NASA Astrophysics Data System (ADS)
Wei, Ruyi; Yin, Bangsheng
2015-07-01
Due to the moving plane mirror, tilt compensation is crucial and challenging in designing high precision Michelson-type interferometers. In this paper, we propose an optical configuration design using an image rotator and plane mirrors, including a movable double-sided mirror (DSM) to balance out the tilt of the mirror. We analysed the optical path differences (OPD) caused by the tilt of the DSM and their effects on interferogram under different tilt cases. Analyses demonstrate that this design is able to cancel out the offset of the OPD introduced by the tilt pitch angle. For different incident rays in parallel, the position of the tilt centre has no relationship with the change of the OPD, implying that the OPD could be self-compensated, and the modulation of the interferogram will not be degraded due to the tilt. This configuration effectively relaxes the requirements on the control of the precision of the postures of the moving mirror and thus may have broad applications.
Phase tomography from x-ray coherent diffractive imaging projections.
Guizar-Sicairos, Manuel; Diaz, Ana; Holler, Mirko; Lucas, Miriam S; Menzel, Andreas; Wepf, Roger A; Bunk, Oliver
2011-10-24
Coherent diffractive imaging provides accurate phase projections that can be tomographically combined to yield detailed quantitative 3D reconstructions with a resolution that is not limited by imaging optics. We present robust algorithms for post-processing and alignment of these tomographic phase projections. A simple method to remove undesired constant and linear phase terms on the reconstructions is given. Also, we provide an algorithm for automatic alignment of projections that has good performance even for samples with no fiducial markers. Currently applied to phase projections, this alignment algorithm has proven to be robust and should also be useful for lens-based tomography techniques that pursue nanoscale 3D imaging. Lastly, we provide a method for tomographic reconstruction that works on phase projections that are known modulo 2?, such that the phase unwrapping step is avoided. We demonstrate the performance of these algorithms by 3D imaging of bacteria population in legume root-nodule cells. PMID:22108985
Phase correlation using shear average for image registration
John Stowers; Michael Hayes; Andrew Bainbridge-Smith
2010-01-01
Correlation of images is a common step in image registration algorithms. Therefore it is important that the correlation step be efficient and accurate. This paper introduces the ‘shear average’ method for computing the relative translation between two similar images. We demonstrate that the proposed technique performance is comparable to traditional phase-correlation based techniques, while also being more numerically efficient.
NASA Astrophysics Data System (ADS)
Adler, Desmond C.; Huber, Robert; Fujimoto, James G.
2007-03-01
Buffered Fourier domain mode-locked (FDML) lasers are demonstrated for dynamic phase-sensitive optical coherence tomography (OCT) and 3D OCT phase microscopy. Systems are operated at sweep speeds of 42, 117, and 370 kHz, and displacement sensitivities of 39, 52, and 102 pm are achieved, respectively. Sensitivities are comparable to spectrometer-based OCT phase microscopy systems, but much faster acquisition speeds are possible. An additional factor of sqrt 2 improvement in noise performance is observed for differential phase measurements, which is important for Doppler OCT. Dynamic measurements of piezoelectric transducer motion and static 3D OCT phase microscopy are demonstrated. Buffered FDML lasers provide excellent displacement sensitivities at extremely high sweep speeds.
Adler, Desmond C; Huber, Robert; Fujimoto, James G
2007-03-15
Buffered Fourier domain mode-locked (FDML) lasers are demonstrated for dynamic phase-sensitive optical coherence tomography (OCT) and 3D OCT phase microscopy. Systems are operated at sweep speeds of 42, 117, and 370 kHz, and displacement sensitivities of 39, 52, and 102 pm are achieved, respectively. Sensitivities are comparable to spectrometer-based OCT phase microscopy systems, but much faster acquisition speeds are possible. An additional factor of sqrt 2 improvement in noise performance is observed for differential phase measurements, which is important for Doppler OCT. Dynamic measurements of piezoelectric transducer motion and static 3D OCT phase microscopy are demonstrated. Buffered FDML lasers provide excellent displacement sensitivities at extremely high sweep speeds. PMID:17308582
X-ray phase contrast imaging and noise evaluation using a single phase grating interferometer.
Rizzi, J; Mercère, P; Idir, M; Silva, P Da; Vincent, G; Primot, Jérôme
2013-07-15
In this paper we present some quantitative measurements of X-ray phase contrast images and noise evaluation obtained with a recent grating based X-ray phase contrast interferometer. This device is built using a single phase grating and a large broadband X-ray source. It was calibrated using a reference sample and finally used to perform measurements of a biological fossil: a mosquito trapped in amber. As phase images, noise was evaluated from the measured interferograms. PMID:23938580
Effect of coherence loss in differential phase contrast imaging
NASA Astrophysics Data System (ADS)
Cai, Weixing; Ning, Ruola; Liu, Jiangkun
2014-03-01
Coherence property of x-rays is critical in the grating-based differential phase contrast (DPC) imaging because it is the physical foundation that makes any form of phase contrast imaging possible. Loss of coherence is an important experimental issue, which results in increased image noise and reduced object contrast in DPC images and DPC cone beam CT (DPC-CBCT) reconstructions. In this study, experimental results are investigated to characterize the visibility loss (a measurement of coherence loss) in several different applications, including different-sized phantom imaging, specimen imaging and small animal imaging. Key measurements include coherence loss (relative intensity changes in the area of interest in phase-stepping images), contrast and noise level in retrieved DPC images, and contrast and noise level in reconstructed DPC-CBCT images. The influence of size and composition of imaged object (uniform object, bones, skin hairs, tissues, and etc) will be quantified. The same investigation is also applied for moiré pattern-based DPC-CBCT imaging with the same exposure dose. A theoretical model is established to relate coherence loss, noise level in phase stepping images (or moiré images), and the contrast and noise in the retrieved DPC images. Experiment results show that uniform objects lead to a small coherence loss even when the attenuation is higher, while objects with large amount of small structures result in huge coherence loss even when the attenuation is small. The theoretical model predicts the noise level in retrieved DPC images, and it also suggests a minimum dose required for DPC imaging to compensate for coherence loss.
Unsupervised Segmentation of Hyperspectral Images Using Modified Phase Correlation
A. Erturkerturk; S. Erturkerturk
2006-01-01
This letter presents hyperspectral image segmentation based on the phase-correlation measure of subsampled hyperspectral data, which is referred to as modified phase correlation. The hyperspectral spectrum of each pixel is initially subsampled to gain robustness against noise and spatial variability, and phase correlation is applied to determine spectral similarity. Similar and dissimilar pixels are decided according to the peak value
Freiser, B.S.
1993-09-01
This report focuses on progress in seven areas: (1) Gas-Phase Reactions of Fe(Benzyne){sup +} with Simple Alkyl Halides; (2) Photodissociation and Collision-Induced Dissociation of Molecular Ions From Methylphenol and Chloromethylphenol; (3) Isotopomer Differentiation Using Metal Ion Chemical Ionization Reagents; (4) Multiple Excitation Collisional Activation (MECA) in Fourier Transform Mass Spectrometry; (5) Chemistry of Fe{sup +}-Arene Ions with Halobenzenes; (6) Gas-Phase Photodissociaton Study of Ag(Benzene){sup +} and Ag(Toluene){sup +}; and (7) Reactivity of Ti{sup 2+} and V{sup 2+} with Small Alkanes.
Bormin Huang; Shih-Chieh Wei; Hung-Lung Huang; William L. Smith; Hal J. Bloom
2008-01-01
As part of NASA's New Millennium Program, the Geostationary Imaging Fourier Transform Spectrometer (GIFTS) is an advanced ultraspectral sounder with a 128x128 array of interferograms for the retrieval of such geophysical parameters as atmospheric temperature, moisture, and wind. With massive data volume that would be generated by future advanced satellite sensors such as GIFTS, chances are that even the state-of-the-art
Development of neutron tomography and phase contrast imaging technique
Kashyap, Y. S.; Agrawal, Ashish; Sarkar, P. S.; Shukla, Mayank; Sinha, Amar [Neutron and X-ray Physics Facilities, Bhabha Atomic Research Centre, Mumbai-400085 (India)
2013-02-05
This paper presents design and development of a state of art neutron imaging technique at CIRUS reactor with special reference for techniques adopted for tomography and phase contrast imaging applications. Different components of the beamline such as collimator, shielding, sample manipulator, digital imaging system were designed keeping in mind the requirements of data acquisition time and resolution. The collimator was designed in such a way that conventional and phase contrast imaging can be done using same collimator housing. We have done characterization of fuel pins, study of hydride blisters in pressure tubes hydrogen based cells, two phase flow visualization, and online study of locomotive parts etc. using neutron tomography and radiography technique. We have also done some studies using neutron phase contrast imaging technique on this beamline.
NASA Astrophysics Data System (ADS)
Mico, Vicente; Zalevsky, Zeev; García, Javier
2008-09-01
We present an experimental setup useful for complex amplitude evaluation and phase image quantification of three-dimensional (3-D) samples in digital holographic microscopy (DHM). It is based on a common-path interferometric configuration performed by dividing the input plane in two contiguous regions and by placing a translation grating near to the Fourier plane. Then, complex amplitude distribution of the sample under test is recovered with phase-shifting standard method obtained by moving the grating using a linear motion stage. Some experimental results of an USAF resolution test are presented for different numerical aperture (NA) microscope lenses. In a second part, the proposed setup is tested under superresolution purposes. Based on the object's spectrum shift produced by off-axis illumination, we use time multiplexing to generate a synthetic aperture enlargement that improves the final image resolution. Experimental results for the case of a biosample (human red blood cells) and a commercial low NA microscope lens validates the suggested superresolution approach.
Adaptive optics and phase diversity imaging for responsive space applications.
Smith, Mark William; Wick, David Victor
2004-11-01
The combination of phase diversity and adaptive optics offers great flexibility. Phase diverse images can be used to diagnose aberrations and then provide feedback control to the optics to correct the aberrations. Alternatively, phase diversity can be used to partially compensate for aberrations during post-detection image processing. The adaptive optic can produce simple defocus or more complex types of phase diversity. This report presents an analysis, based on numerical simulations, of the efficiency of different modes of phase diversity with respect to compensating for specific aberrations during post-processing. It also comments on the efficiency of post-processing versus direct aberration correction. The construction of a bench top optical system that uses a membrane mirror as an active optic is described. The results of characterization tests performed on the bench top optical system are presented. The work described in this report was conducted to explore the use of adaptive optics and phase diversity imaging for responsive space applications.
Phase contrast imaging of buccal mucosa tissues-Feasibility study
NASA Astrophysics Data System (ADS)
Fatima, A.; Tripathi, S.; Shripathi, T.; Kulkarni, V. K.; Banda, N. R.; Agrawal, A. K.; Sarkar, P. S.; Kashyap, Y.; Sinha, A.
2015-06-01
Phase Contrast Imaging (PCI) technique has been used to interpret physical parameters obtained from the image taken on the normal buccal mucosa tissue extracted from cheek of a patient. The advantages of this method over the conventional imaging techniques are discussed. PCI technique uses the X-ray phase shift at the edges differentiated by very minute density differences and the edge enhanced high contrast images reveal details of soft tissues. The contrast in the images produced is related to changes in the X-ray refractive index of the tissues resulting in higher clarity compared with conventional absorption based X-ray imaging. The results show that this type of imaging has better ability to visualize microstructures of biological soft tissues with good contrast, which can lead to the diagnosis of lesions at an early stage of the diseases.
Additional processing for phase unwrapping of magnetic resonance thermometry imaging
NASA Astrophysics Data System (ADS)
Suprijanto, S.; Vos, Frans M.; Vogel, M. W.; Vossepoel, Albert M.; Vrooman, Henri A.
2002-05-01
Magnetic Resonance Thermometry imaging is a non-invasive method for temperature monitoring in hyperthermia treatment. The temperature can be determined from the phase shift in a gradient-echo sequence. Due to large temperature variations, the phase shift may exceed the (-? ,?) radians interval. The phase value beyond this interval will be wrapped. Unfortunately, the temperature is only proportional to the absolute phase change. Therefore, phase unwrapping (PU) is required to recover the absolute phase from the wrapped representation. While the phase may contain spurious discontinuities, the algorithm must distinguish them from true phase discontinuities. We propose additional processing to support PU in order to improve the algorithm for recovery of the best estimation of absolute phase. The Minimum Weight Discontinuity (MWD) algorithm was used for PU. The steps to be taken on additional processing consist of applying a Gaussian filter to the raw complex MRI images, deriving the weights of a quality map, and segmenting unreliable regions using the magnitude image. The raw wrapped phase images, acquired from a phantom and from a porcine liver (acquired under laser irradiation), were used to test the effect of additional processing. The effect was compared with the conventional approach (i.e. mere unwrapping with the MWD algorithm).
During a field study in the summer of 2000 in the Research Triangle Park (RTP), aerosol samples were collected using a five stage cascade impactor and subsequently analyzed using Fourier Transform Infrared Spectroscopy (FTIR). The impaction surfaces were stainless steel disks....
Analysis of field of view of optical aperture synthesis imaging interferometry
Dayong Wang; Xiyang Fu; Hongfeng Guo; Shiquan Tao; Bo Zhao; Yijia Zhen
2005-01-01
Interferometric imaging systems measure the complex visibility, which is the Fourier transform of the source brightness distribution, according to the van Cittert-Zernike theorem. Both the amplitude and phase of the visibility are needed to produce images of a complex object structure by Fourier inversion. In this paper, by using the generalized imaging theory of a diffraction-limited incoherent imaging system, the
Potsaid, Benjamin; Baumann, Bernhard; Huang, David; Barry, Scott; Cable, Alex E.; Schuman, Joel S.; Duker, Jay S.; Fujimoto, James G.
2011-01-01
We demonstrate ultrahigh speed swept source/Fourier domain ophthalmic OCT imaging using a short cavity swept laser at 100,000–400,000 axial scan rates. Several design configurations illustrate tradeoffs in imaging speed, sensitivity, axial resolution, and imaging depth. Variable rate A/D optical clocking is used to acquire linear-in-k OCT fringe data at 100kHz axial scan rate with 5.3um axial resolution in tissue. Fixed rate sampling at 1 GSPS achieves a 7.5mm imaging range in tissue with 6.0um axial resolution at 100kHz axial scan rate. A 200kHz axial scan rate with 5.3um axial resolution over 4mm imaging range is achieved by buffering the laser sweep. Dual spot OCT using two parallel interferometers achieves 400kHz axial scan rate, almost 2X faster than previous 1050nm ophthalmic results and 20X faster than current commercial instruments. Superior sensitivity roll-off performance is shown. Imaging is demonstrated in the human retina and anterior segment. Wide field 12×12mm data sets include the macula and optic nerve head. Small area, high density imaging shows individual cone photoreceptors. The 7.5mm imaging range configuration can show the cornea, iris, and anterior lens in a single image. These improvements in imaging speed and depth range provide important advantages for ophthalmic imaging. The ability to rapidly acquire 3D-OCT data over a wide field of view promises to simplify examination protocols. The ability to image fine structures can provide detailed information on focal pathologies. The large imaging range and improved image penetration at 1050nm wavelengths promises to improve performance for instrumentation which images both the retina and anterior eye. These advantages suggest that swept source OCT at 1050nm wavelengths will play an important role in future ophthalmic instrumentation. PMID:20940894
Multifocus Image Fusion Using Local Phase Coherence Measurement
Wang, Zhou
, existing methods share a common as- sumption that high local energy or contrast is a direct indication words: image fusion, local phase coherence, local energy, complex wavelet transform 1 Introduction Image, which include the Laplacian pyramid [4], the gradient pyramid [5], the ratio-of-low-pass pyramid [6
Matsuo, M; Kanematsu, M; Murakami, T; Kim, T; Hori, M; Kondo, H; Nakamura, H; Hoshi, H
2000-09-01
The purpose of our study was to evaluate the supplementary value of breath-hold fat-suppressed T2-weighted magnetic resonance (MR) imaging with half-Fourier single-shot fast spin-echo (SE) or multishot SE echoplanar (EP) sequences combined with respiratory-triggered fat-suppressed fast SE T2-weighted MR imaging for detection and characterization of focal hepatic lesions. MR images in 42 patients with 82 solid, malignant and 77 nonsolid, benign lesions were analyzed. Image review was conducted on a segment-by-segment basis; in all, 333 liver segments were reviewed separately for solid and nonsolid lesions by three independent radiologists. For solid lesions, observer performance with receiver-operating-characteristic (ROC) analysis in one radiologist and specificity in another significantly improved after adding single-shot fast SE images. For nonsolid lesions, observer performance with ROC analysis in one radiologist and specificity in another significantly improved after adding single-shot fast SE images. Combining breath-hold half-Fourier single-shot fast SE imaging with respiratory-triggered fast SE imaging may be recommended for improved detection and characterization of focal hepatic lesions. J. Magn. Reson. Imaging 2000;12:444-452. PMID:10992312
Image-inpainting and quality-guided phase unwrapping algorithm.
Meng, Lei; Fang, Suping; Yang, Pengcheng; Wang, Leijie; Komori, Masaharu; Kubo, Aizoh
2012-05-01
For the wrapped phase map with regional abnormal fringes, a new phase unwrapping algorithm that combines the image-inpainting theory and the quality-guided phase unwrapping algorithm is proposed. First, by applying a threshold to the modulation map, the valid region (i.e., the interference region) is divided into the doubtful region (called the target region during the inpainting period) and the reasonable one (the source region). The wrapped phase of the doubtful region is thought to be unreliable, and the data are abandoned temporarily. Using the region-filling image-inpainting method, the blank target region is filled with new data, while nothing is changed in the source region. A new wrapped phase map is generated, and then it is unwrapped with the quality-guided phase unwrapping algorithm. Finally, a postprocessing operation is proposed for the final result. Experimental results have shown that the performance of the proposed algorithm is effective. PMID:22614426
Phase Contrast Neutron Imaging using Single and Multiple Pinhole Apertures
NASA Astrophysics Data System (ADS)
Mishra, Kaushal Kishor
In the present work phase contrast neutron imaging at low/medium intensity neutron sources using single and multiple pinhole apertures has been investigated. Phase contrast techniques utilize the wave nature of neutrons (along with the particle nature used by conventional neutron imaging) to enhance the material edge contrast in the object image. The technique benefits from differences in the coherent scattering length densities of different materials in the sample. The performed investigation included multiple aspects related to the theoretical understanding, simulation techniques, experimental feasibility at the PULSTAR imaging facility, and image processing/reconstruction pertaining to these techniques. The theoretical aspects include the physical understanding of phase contrast as well as multi-pinhole imaging. The theory for the image intensity variation for mixed phase-amplitude objects was developed. Presence of an additional interaction term, quantified by the scalar product of the gradient of real and imaginary parts of the transmission function of the object, was found in the neutron intensity expression. Further, a theoretical understanding of the image formation process using multi-pinhole masks was also developed. It was shown that the formed image of the object from a multiple pinhole aperture can be written as a convolution of the source mask image at the detector with the object image obtained through a single pinhole. The theoretical work performed above was used to develop simulation and design methodologies. An image simulation technique was developed to simulate phase contrast images of specified objects using the phase-amplitude formulation. Demonstration of the technique was performed using various designed phantoms. The simulation technique can act as a tool for assessing the usefulness of phase contrast imaging as an edge enhancement method for a particular sample. Performance of phase contrast neutron imaging requires a spatially coherent beam. Spatial coherence of the beam can be increased by increasing the L d ratio and the average wavelength of the neutron beam. These methods of improving the spatial coherence lead to a significant reduction in the neutron intensity available to image the object, thereby favoring its implementation at high intensity neutron sources. However, in order to harness the potential of this technique, its usability needs to be expanded to low/medium intensity neutron sources that are more common worldwide. In the present work experimental demonstration of the technique was performed at the 1MWth PULSTAR reactor, which represents a medium intensity neutron source. This required meticulous design to maximize the spatial coherence of the beam while maintaining the neutron intensity at the image plane. Twelve inches of single crystal sapphire was used to filter out fast neutrons to lower the average energy of the neutron beam. A 500mum gadolinium foil with a 0.5mm diameter pinhole was used as the aperture following which, a 0.6o beam divergence was provided using borated polyethylene discs with holes of increasing diameter. In order to improve the SNR in the image multiple pinhole apertures were explored. Uncoded masks were considered for this purpose. A collimator with seven pinholes was designed to perform the imaging. Masks with greater number of pinholes were studied using simulations but could not be explored experimentally due to space restrictions at the facility. The image reconstruction of the raw data was performed using a least square de-convolution technique. Tikhonov regularization was investigated in this regard to make the convolution matrices well behaved wherever required. Also, various de-noising techniques like median filtering, Wiener filtering and soft thresholding using Symlets were explored to improve the reconstructed image. It was concluded that the choice of the de-noising techniques depends upon the properties desired in the reconstructed image like smoothness, blockiness etc. Thus, in the present work two of the comparatively new neutron imagin
Bubis, E L [Institute of Applied Physics, Russian Academy of Sciences, Nizhny Novgorod (Russian Federation)
2011-06-30
Self-imaging of transparent objects and structures in focusing of a spatially phase-modulated laser beam into an extended weakly absorbing medium is described. The laser power level that is necessary for effective imaging corresponds to the illuminating beam power when thermal self-defocusing starts evolving in the medium. The effect can be described in terms of the ideology of Zernike's classical phase-contrast method. Edge enhancement in visualised images of transparent objects is experimentally demonstrated. Self-imaging of a microscopic object in the form of transparent letters and long-lived refractive-index fluctuations in liquid glycerol is shown. Due to the adaptivity of the process under consideration, unlike the classical case, self-imaging occurs also in the situations where a beam is displaced (undergoes random walk) as a whole in the Fourier plane, for example, in the presence of thermal flows. (image processing)
NASA Astrophysics Data System (ADS)
Grigoriev, Yurii N.; Meleshko, Sergey V.; Suriyawichitseranee, Amornrat
2015-06-01
Group analysis of the spatially homogeneous and molecular energy dependent Boltzmann equations with source term is carried out. The Fourier transform of the Boltzmann equation with respect to the molecular velocity variable is considered. The correspondent determining equation of the admitted Lie group is reduced to a partial differential equation for the admitted source. The latter equation is analyzed by an algebraic method. A complete group classification of the Fourier transform of the Boltzmann equation with respect to a source function is given. The representation of invariant solutions and corresponding reduced equations for all obtained source functions are also presented.
Introduction of liquid crystal device into THz phase imaging
NASA Astrophysics Data System (ADS)
Ito, Ryota; Takahashi, Takuya; Honma, Michinori; Nose, Toshiaki
2015-03-01
We investigate the terahertz (THz) phase imaging using liquid crystal (LC) device. Recently, there have been extensive efforts to measure the refractive indices and transmission losses of some LC materials in THz region. From these results, LC materials show relatively large refractive index anisotropy and they can have a potential application to some control devices similar to the display application. Furthermore, tunable LC THz phase shifter has been reported. In this study, an attempt was made to introduce the LC device into the THz phase imaging which was based on four-step phase-shifting algorithm. Four-step phase-shifting algorithm is one of the most effective methods of phase imaging and moving mirror is needed to introduce phase shift in standard measurements. In addition, we should prepare the two rays with common source, therefor experimental setup becomes complicated. While on the other hand, it is just needed to insert a LC phase shifter into the light path when we adopt LC device. Furthermore, low-voltage application is enough to introduce the phase-shifting, hence it is not necessary to prepare the moving mirror. In this work, we fabricate the electrically tunable LC phase shifter which has sandwich cell structure. The fundamental phase-shifting properties were measured by using an optically pumped gas laser system which can generate continuous wave (CW) THz waves. In addition, we investigated the phase shifting interferometry which was based on four-step phase-shifting algorithm by using LC phase shifter. We also estimate the birefringence of X-cut crystalline quartz at 2.5 THz.
X-ray phase-contrast imaging: the quantum perspective
NASA Astrophysics Data System (ADS)
Slowik, J. M.; Santra, R.
2013-08-01
Time-resolved phase-contrast imaging using ultrafast x-ray sources is an emerging method to investigate ultrafast dynamical processes in matter. Schemes to generate attosecond x-ray pulses have been proposed, bringing electronic timescales into reach and emphasizing the demand for a quantum description. In this paper, we present a method to describe propagation-based x-ray phase-contrast imaging in nonrelativistic quantum electrodynamics. We explain why the standard scattering treatment via Fermi’s golden rule cannot be applied. Instead, the quantum electrodynamical treatment of phase-contrast imaging must be based on a different approach. It turns out that it is essential to select a suitable observable. Here, we choose the quantum-mechanical Poynting operator. We determine the expectation value of our observable and demonstrate that the leading order term describes phase-contrast imaging. It recovers the classical expression of phase-contrast imaging. Thus, it makes the instantaneous electron density of non-stationary electronic states accessible to time-resolved imaging. Interestingly, inelastic (Compton) scattering does automatically not contribute in leading order, explaining the success of the semiclassical description.
Full-wave approach for x-ray phase imaging.
Sung, Yongjin; Sheppard, Colin J R; Barbastathis, George; Ando, Masami; Gupta, Rajiv
2013-07-29
We present a rigorous forward model for phase imaging of a 3-D object illuminated by a cone-shaped x-ray beam. Our model is based on a full-wave approach valid under the first Rytov approximation, and thus can be used with large and thick objects, e.g., luggage and human patients. We unify light-matter interaction and free-space propagation into an integrated wave optics framework. Therefore, our model can accurately calculate x-ray phase images formed with sources of arbitrary shape, and it can be effectively incorporated into x-ray phase tomography as a forward model. Within the best of our knowledge, this is the first non-paraxial, full-wave model for X-ray phase imaging. PMID:23938626
Real-time quantitative phase imaging for cell studies
NASA Astrophysics Data System (ADS)
Pham, Hoa Vinh
Most biological cells are not clearly visible with a bright field microscope. Several methods have been developed to improve contrast in cell imaging, including use of exogenous contrast agents such as fluorescence microscopy, as well as utilizing properties of light-specimen interaction for optics design, to reveal the endogenous contrast, such as phase contrast microscopy (PCM) and differential interference contrast (DIC) microscopy. Although PCM and DIC methods significantly improve the image contrast without the need for staining agents, they only provide qualitative information about the phase change induced by the cells as light passes through them. Quantitative phase imaging (QPI) has recently emerged as an effective imaging tool which provides not only better image contrast but also cell-induced phase shifts in the optical pathlength, thus allowing nanometer-scale measurements of structures and dynamics of the cells. Other important aspects of an imaging system are its imaging speed and throughput. High-throughput, high-speed, real-time quantitative phase imaging with high spatial and temporal sensitivity is highly desirable in many applications including applied physics and biomedicine. In this dissertation, to address this need, I discuss the development of such an imaging system that includes the white light diffraction phase microscopy (wDPM), a new optical imaging method, and image reconstruction/analysis algorithms using graphics processing units (GPUs). wDPM can measure optical pathlength changes at nanometer scale both spatially and temporally with single-shot image acquisition, enabling very fast imaging. I also exploit the broadband spectrum of white light used as the light source in wDPM to develop a system called spectroscopic diffraction phase microscopy (sDPM). This sDPM system allows QPI measurements at several wavelengths, which solves the problem of thickness and refractive index coupling in the phase shifts induced by the cell, and which also may help visualize more-complex cell structures. Owing to its high spatial and temporal sensitivity and single-shot acquisition, wDPM enables measurement of nanometer-scale dynamic processes of cells at very high rate and measurement of cell growth because of the linear relationship between a cell-induced phase shift and its dry mass. The parallel algorithms and software tools I developed allow real-time QPI imaging and online image analysis at frame rates of up to 40 megapixel-size images per second. This capability allows very high throughput of several thousands of cells in imaging mode and eliminates the need of storing the images since we only need to store processed data, which is much smaller in storage size. Finally, I present the capability of the system by showing an application in red blood cell screening, which can be used as a diagnostic tool in blood testing and may pave the way for digital hematology and remote diagnostics.
Fourier Preprocessing for Hand Print Character Recognition
G. H. Granlund
1972-01-01
A pattern-recognition method, making use of Fourier transformations to extract features which are significant for a pattern, is described. The ordinary Fourier coefficients are difficult to use as input to categorizers because they contain factors dependent upon size and rotation as well as an arbitrary phase angle. From these Fourier coefficients, however, other more useful features can easily be derived.
Extended local Born Fourier migration method
Huang, L.J.; Fehler, M.C.; Wu, R.S.
1999-10-01
A migration approach based on a local application of the Born approximation within each extrapolation interval contains a singularity that can make direct application unstable. Previous authors have suggested adding an imaginary part to the vertical wavenumber to eliminate the singularity. However, their method requires that the reference slowness must be the maximum slowness is selected as a reference slowness. Therefore, its applicability is limited. The authors develop an extended local Born Fourier migration method that circumvents the singularity problem of the local Born solution and makes it possible to choose the average slowness as a reference slowness. It is computationally efficient because of the use of a fast Fourier transform algorithm. It can handle wider angles (or steeper interfaces) and scattering effects of heterogeneities more accurately than the split-step Fourier (SSF) method, which accounts for only the phase change as a result of the slowness perturbations but not amplitude change. To handle large lateral slowness variations, the authors introduce different reference slownesses in different regions of a medium to ensure the condition of small perturbation. The migration result obtained using the extended local Born Fourier method with multiple reference slownesses demonstrates that the method can produce high-quality images of complex structures with large lateral slowness variations.
MR image segmentation of the knee bone using phase information.
Bourgeat, Pierrick; Fripp, Jurgen; Stanwell, Peter; Ramadan, Saadallah; Ourselin, Sébastien
2007-08-01
Magnetic resonance (MR) imaging is a widely available and well accepted non invasive imaging technique. Development of automatic and semi-automatic techniques to analyse MR images has been the focus of much research and numerous publications. However, most of this research only uses the magnitude of the acquired complex MR signal, discarding the phase information. In MR, the phase relates to the magnetic properties of tissues, information which is not found in the magnitude signal. As a result, phase is a complement to the magnitude signal and can improve the segmentation and analysis of MR images. In this paper, we consider the automatic classification of textured tissues in 3D MRI. Specifically, we include features extracted from the phase of the MR signal to improve texture discrimination in the bone segmentation. Our approach does not require phase unwrapping, with the MR signal processed in its complex form. The extra information extracted from the phase provides better segmentation, compared to only using magnitude features. The segmentation approach is integrated within a novel multiscale scheme, designed to improve the speed of pixel based classification algorithms, such as support vector machines. An order of magnitude increase is obtained, by reducing the number of pixels that need to be classified. PMID:17482502
Digital holographic imaging technology
Xiufa Song; Aili Qin; Yi Wang
2009-01-01
The recording and numerical reconstruction of digital lensless Fourier hologram is analyzed. Based on the quadratic phase mask of the reconstructed image field the two common methods for phase reconstruction are discussed and compared by computer simulations. The results show that the automatic phase compensation approach has stronger toleration for noise than that of the digital holography combined with the
Image segmentation of nanoscale Zernike phase contrast X-ray computed tomography images
NASA Astrophysics Data System (ADS)
Kumar, Arjun S.; Mandal, Pratiti; Zhang, Yongjie; Litster, Shawn
2015-05-01
Zernike phase contrast is a useful technique for nanoscale X-ray computed tomography (CT) imaging of materials with a low X-ray absorption coefficient. It enhances the image contrast by phase shifting X-ray waves to create changes in amplitude. However, it creates artifacts that hinder the use of traditional image segmentation techniques. We propose an image restoration method that models the X-ray phase contrast optics and the three-dimensional image reconstruction method. We generate artifact-free images through an optimization problem that inverts this model. Though similar approaches have been used for Zernike phase contrast in visible light microscopy, this optimization employs an effective edge detection method tailored to handle Zernike phase contrast artifacts. We characterize this optics-based restoration method by removing the artifacts in and thresholding multiple Zernike phase contrast X-ray CT images to produce segmented results that are consistent with the physical specimens. We quantitatively evaluate and compare our method to other segmentation techniques to demonstrate its high accuracy.
Techavipoo, Udomchai; Lackey, John; Shi, Jianrong; Guan, Xin; Lai, Song
2009-11-01
Diffusion tensor imaging requires correction of eddy current distortion in diffusion-weighted images. An effective retrospective correction approach is to transform a diffusion-weighted image to maximize the mutual information (MI) between the transformed diffusion-weighted image and the corresponding T2-weighted image. In the literature, either linear interpolation or partial volume interpolation is applied to estimate the MI objective function. However, these interpolation methods induce artifacts to the MI objective function, thus compromising correction results. In this work, the MI objective function is estimated based on interpolation using Fourier shift theorem. This method eliminates the artifacts incurred with the aforementioned interpolation methods. The algorithm is further improved by approximating pixel values using their nearest neighbors in the up-sampled spatial domain, resulting in dramatically increased computational efficiency without compromising the correction results. The effects of varying the number of quantization levels and using Parzen window filtering to smooth the MI objective function are also investigated to obtain optimized algorithm parameters. The diffusion tensor image quality after applying the proposed distortion correction method is significantly improved visually. PMID:19608366
NASA Astrophysics Data System (ADS)
Kang, Jooyoung; Park, Sung-Chan; Kim, Jung-ho; Song, Jongkeun
2014-02-01
In the ultrasound imaging system, blurring which occurs after passing through ultrasound scanner system, represents point spread function (PSF) that describes the response of the ultrasound imaging system to a point source distribution. So, de-blurring can be achieved by de-convolving the ultrasound images with an estimated of corresponding PSF. However, it is hard to attain an accurate estimation of PSF due to the unknown properties of the tissues of the human body through the ultrasound signal propagates. In this paper, we present a new method for PSF estimation in the Fourier domain (FD) based on parametric minimum phase information, and simultaneously, it performs fast 2D de-convolution in the ultrasound imaging system. Although most of complex cepstrum methods [14], are obtained using complex 2D phase unwrapping [18] [19] in order to estimate the FD-phase information of PSF, our algorithm estimates the 2D PSF using 2D FD-phase information with the parametric weighting factor ? and ?. They affect the feature of PSF shapes.This makes the computations much simpler and the estimation more accurate. Our algorithm works on the beam-formed uncompressed radio-frequency data, with pre-measured and estimated 2D PSFs database from actual probe used. We have tested our algorithm with vera-sonic system and commercial ultrasound scanner (Philips C4-2), in known speed of sound phantoms and unknown speeds in vivo scans.
Phase retrieval with transverse translation diversity: a nonlinear
Fienup, James R.
, "Reconstruction of a complex-valued object from the modulus of its Fourier transform using a support constraint," Phys. Rev. B 68, 140101 (2003). 7. J. R. Fienup, "Lensless coherent imaging by phase retrieval. Guizar-Sicairos and J. R. Fienup, "Phase retrieval with Fourier-weighted projections," J. Opt. Soc. Am
Tian, Lei, Ph. D. Massachusetts Institute of Technology
2010-01-01
In this thesis, two computational imaging techniques used for underwater research, in particular, two-phase flows measurements, are presented. The techniques under study, digital holographic imaging and light field imaging, ...
Phase contrast and darkfield imaging in x-ray microscopy
Graeme R. Morrison
1993-01-01
The transmission x-ray microscope has so far been used almost exclusively to form images with absorption contrast. Methods of forming phase contrast and darkfield images are considered, particularly in the scanning transmission x-ray microscope, and the advantages and disadvantages of these methods are reviewed, particularly in the context of the new generation of synchrotron x-ray sources that will be able
Computation of component image velocity from local phase information
David J. Fleet; Allan D. Jepson
1990-01-01
We present a technique for the computation of 2D component velocity from image sequences. Initially, the image sequence is represented by a family of spatiotemporal velocity-tuned linear filters. Component velocity, computed from spatiotemporal responses of identically tuned filters, is expressed in terms of the local first-order behavior of surfaces of constant phase. Justification for this definition is discussed from the
High-resolution quantitative phase microscopic imaging in deep UV with phase retrieval.
Anand, Arun; Faridian, Ahmad; Chhaniwal, Vani; Pedrini, Giancarlo; Osten, Wolfgang; Javidi, Bahram
2011-11-15
High-resolution three-dimensional (3D) microscopic imaging requires the use of short wavelengths. Quantitative 3D imaging techniques, such as digital holographic microscopy, require interference between the object beam and a known reference background for the extraction of phase information. At shorter wavelengths, due to short coherence lengths, it may be difficult to implement a two-beam off-axis setup. Thus, a single-beam technique, which provides complete phase information, may be better suited for short wavelengths. This Letter describes the development of a quantitative microscopy technique at 193 nm using multiple intensity samplings and phase retrieval. PMID:22089564
Dynamic quantitative phase imaging for biological objects using a pixelated phase mask
Creath, Katherine; Goldstein, Goldie
2012-01-01
This paper describes research in developing a dynamic quantitative phase imaging microscope providing instantaneous measurements of dynamic motions within and among live cells without labels or contrast agents. It utilizes a pixelated phase mask enabling simultaneous measurement of multiple interference patterns derived using the polarization properties of light to track dynamic motions and morphological changes. Optical path difference (OPD) and optical thickness (OT) data are obtained from phase images. Two different processing routines are presented to remove background surface shape to enable quantification of changes in cell position and volume over time. Data from a number of different moving biological organisms and cell cultures are presented. PMID:23162725
Hosseinbor, A. Pasha; Chung, Moo K.; Wu, Yu-Chien; Alexander, Andrew L.
2012-01-01
The ensemble average propagator (EAP) describes the 3D average diffusion process of water molecules, capturing both its radial and angular contents. The EAP can thus provide richer information about complex tissue microstructure properties than the orientation distribution function (ODF), an angular feature of the EAP. Recently, several analytical EAP reconstruction schemes for multiple q-shell acquisitions have been proposed, such as diffusion propagator imaging (DPI) and spherical polar Fourier imaging (SPFI). In this study, a new analytical EAP reconstruction method is proposed, called Bessel Fourier orientation reconstruction (BFOR), whose solution is based on heat equation estimation of the diffusion signal for each shell acquisition, and is validated on both synthetic and real datasets. A significant portion of the paper is dedicated to comparing BFOR, SPFI, and DPI using hybrid, non-Cartesian sampling for multiple b-value acquisitions. Ways to mitigate the effects of Gibbs ringing on EAP reconstruction are also explored. In addition to analytical EAP reconstruction, the aforementioned modeling bases can be used to obtain rotationally invariant q-space indices of potential clinical value, an avenue which has not yet been thoroughly explored. Three such measures are computed: zero-displacement probability (Po), mean squared displacement (MSD), and generalized fractional anisotropy (GFA). PMID:22963853
Phase dispersion X-ray imaging of murine soft tissue
NASA Astrophysics Data System (ADS)
Ingal, V. N.; Ingal, E. A.
2013-12-01
The generation of phase-contrast (PC) images in the phase-dispersion introscopy (PDI) technique is the subject of this paper. Conditions for extreme sensitivity to murine soft-tissue anatomy are discussed. The unique information content and good contrast of the minutest details of anatomy, together with the high brilliance of X-ray optics, give the authors confidence that the PDI method can be successfully applied for medical diagnostics.
Phase and sensitivity of receiver coils in magnetic resonance imaging
McVeigh, E. R.; Bronskill, M. J.; Henkelman, R. M.
2007-01-01
Receiver coil response is a major cause of nonuniformities in magnetic resonance images. The spatial dependence of the sensitivity and phase of single-saddle receiver coils has been investigated quantitatively by calculating the H1 field and comparing the results with measurements of a uniform phantom. Agreement between the measurements and calculations is excellent. A method is developed which corrects for both the nonuniform sensitivity and the phase shifts introduced by receiver coils. PMID:3796476
Full-phase image encryption by two-step phase-shifting interferometry
NASA Astrophysics Data System (ADS)
Meng, Xiangfeng; Cai, Luzhong; Xu, Xianfeng; Yang, Xiulun; Shen, Xiaoxia; Dong, Guoyan; Zhang, Hao
2008-07-01
We have proposed a full-phase image encryption method based on double random-phase encoding in Fresnel domain and pixel random permutation (PRP) technique with the use of two-step phase-shifting interferometry (PSI) we reported recently, and verified the effectiveness of this method and its robustness against occlusion and noise attacks by a series of numerical simulations. Comparing with other similar methods, this approach can decrease the number of the interferograms to be delivered from at least three needed in ordinary PSI to only two, give much better performance of image reconstruction than amplitude-based encryption, and provide much higher security level. This method is usable for both the gray-level images and binary images, and usually the latter will lead to better results.
Phase-space formulation for phase-contrast x-ray imaging
Wu Xizeng; Liu Hong
2005-10-01
Phase-space formulation based on the Wigner distribution has been presented for analyzing phase-contrast image formation. Based on the statistical nature and affine canonical covariance of Wigner distributions in the phase space, we show that the partial coherence effects of incident x-ray wave field on image intensity are simply accounted for by a multiplication factor, which is the reduced complex degree of coherence of the incident x-ray wave field. We show especially that with the undulator sources one cannot obtain the phase-contrast intensity by summing over the contributions from all electron positions, since the van Cittert-Zernike theorem fails in general for undulators. We derive a comprehensive formula that quantifies the effects of partial spatial coherence, polychromatic spectrum, body attenuation, imaging-detector resolution, and radiation dose on phase-contrast visibility in clinical imaging. The results of our computer modeling and simulations show how the formula can provide design guidelines and optimal parameters for clinical x-ray phase-contrast imaging systems.
NASA Astrophysics Data System (ADS)
Ruiz de Galarreta Fanjul, C.; Bouzit, M.; Appourchaux, T.; Dassas, K.; Viale, T.; Philippon, A.; Vial, J.-C.; Maillard, J.-P.
2012-09-01
The spectroscopy of the far UV emission lines of the solar spectrum combined with an imaging capability is essential to understand the physics of the outer solar atmosphere. An imaging Fourier transform spectrometer (IFTSUV) is an attractive instrumental solution to perform such far-UV solar observations. Working in the far UV involves high precision metrology to maintain the optical path difference (OPD) during the entire scanning process of the interferogram. It also involves a compact all-reflection design for UV applications. We present the specification of a servo-system that enables dynamic tip/tilt alignment compensation and OPD sampling measurement of the IFTSUV scanning mirror. We also discuss the first experimental results of a breadboard as well as the preliminary design of a space-based device.
OPTI 512R-Linear Systems, Fourier Transforms Course Description
Arizona, University of
, Fresnel zone plates #12;Imaging Systems and Fourier Optics 18. Fresnel diffraction from Lenses and Fourier transforming properties of lenses 19. Diffraction limited imaging systems 20. Performance of optical imaging. Linear Systems, Fourier Transforms, and Optics. Wiley Interscience Goodman, Joseph W. Introduction
MR phase imaging: sensitive and contrast-enhancing visualization in cellular imaging.
Siow, Tiing Yee; Chen, Chiao-Chi V; Lin, Chien-Yuan; Chen, Jeou-Yuan; Chang, Chen
2012-02-01
The successful translation of stem-cell therapies requires a detailed understanding of the fate of transplanted cells. Magnetic resonance imaging (MRI) has provided a noninvasive means of imaging cell dynamics in vivo by prelabeling cell with T(2) shortening iron oxide particles. However, this approach suffers from a gradual loss of sensitivity since active cell mitosis could decrease the cellular contrast agent (CA) concentration below detection level. In addition, the interpretation of images may be confounded by hypointensities induced by factors other than this CA susceptibility effect (CASE). We therefore examined the feasibility of exploiting the phase information in MRI to increase the sensitivity of cellular imaging and to differentiate the CASE from endogenous image hypointensity. Phase aliasing and the B(0) field inhomogeneity effect were removed by applying a reliable unwrapping algorithm and a high-pass filter, respectively, thus delineating phase variations originating from high spatial frequencies due to the CASE. We found that the filtered phase map detects labeled cells with high sensitivity and can readily differentiate the cell migration track from the white matter, both of which are hypointense in T(2)-weighted magnitude images. Furthermore, an approximate fivefold contrast-to-noise ratio enhancement can be achieved with an MRI phase map over conventional T(2)-weighted magnitude images. PMID:22133285
Jones, Michael W. M.; van Riessen, Grant A.; Abbey, Brian; Putkunz, Corey T.; Junker, Mark D.; Balaur, Eugeniu; Vine, David J.; McNulty, Ian; Chen, Bo; Arhatari, Benedicta D.; Frankland, Sarah; Nugent, Keith A.; Tilley, Leann; Peele, Andrew G.
2013-01-01
X-ray tomography can provide structural information of whole cells in close to their native state. Radiation-induced damage, however, imposes a practical limit to image resolution, and as such, a choice between damage, image contrast, and image resolution must be made. New coherent diffractive imaging techniques, such Fresnel Coherent Diffractive Imaging (FCDI), allows quantitative phase information with exceptional dose efficiency, high contrast, and nano-scale resolution. Here we present three-dimensional quantitative images of a whole eukaryotic cell by FCDI at a spatial resolution below 70?nm with sufficient phase contrast to distinguish major cellular components. From our data, we estimate that the minimum dose required for a similar resolution is close to that predicted by the Rose criterion, considerably below accepted estimates of the maximum dose a frozen-hydrated cell can tolerate. Based on the dose efficiency, contrast, and resolution achieved, we expect this technique will find immediate applications in tomographic cellular characterisation. PMID:23887204
Beyond the lateral resolution limit by phase imaging
NASA Astrophysics Data System (ADS)
Cotte, Y.; Toy, M. Fatih; Depeursinge, C.
2011-03-01
We present a theory stating how to overcome the classical Rayleigh-resolution limit. It is based upon a new resolution criterion in phase of coherent imaging process and its spatial resolution is thought to be only SNR limited. Recently, the experimental observation of systematically occurring phase singularities in coherent imaging of sub-Rayleigh distanced objects has been reported.1 The phase resolution criterion relies on the unique occurrence of phase singularities. A priori, coherent imaging system's resolution can be extended to Abbe's limit.2 However, by introducing a known phase difference, the lateral as well as the longitudinal resolution can be tremendously enlarged. The experimental setup is based on Digital Holographic Microscopy (DHM), an interferometric method providing access to the complex wave front. In off-axis transmission configuration, sub-wavelength nano-metric holes on a metallic film acts as the customized high-resolution test target. The nano-metric apertures are drilled with focused ion beam (FIB) and controlled by scanning electron microscopy (SEM). In this manner, Rayleighs classical two-point resolution condition can be rebuilt by interfering complex fields emanated from multiple single circular apertures on an opaque metallic film. By introducing different offset phases, enhanced resolution is demonstrated. Furthermore, the measurements can be exploited analytically or within the post processing of sampling a synthetic complex transfer function (CTF).
Single-image phase retrieval using an edge illumination X-ray phase-contrast imaging setup.
Diemoz, Paul C; Vittoria, Fabio A; Hagen, Charlotte K; Endrizzi, Marco; Coan, Paola; Brun, Emmanuel; Wagner, Ulrich H; Rau, Christoph; Robinson, Ian K; Bravin, Alberto; Olivo, Alessandro
2015-07-01
A method is proposed which enables the retrieval of the thickness or of the projected electron density of a sample from a single input image acquired with an edge illumination phase-contrast imaging setup. The method assumes the case of a quasi-homogeneous sample, i.e. a sample with a constant ratio between the real and imaginary parts of its complex refractive index. Compared with current methods based on combining two edge illumination images acquired in different configurations of the setup, this new approach presents advantages in terms of simplicity of acquisition procedure and shorter data collection time, which are very important especially for applications such as computed tomography and dynamical imaging. Furthermore, the fact that phase information is directly extracted, instead of its derivative, can enable a simpler image interpretation and be beneficial for subsequent processing such as segmentation. The method is first theoretically derived and its conditions of applicability defined. Quantitative accuracy in the case of homogeneous objects as well as enhanced image quality for the imaging of complex biological samples are demonstrated through experiments at two synchrotron radiation facilities. The large range of applicability, the robustness against noise and the need for only one input image suggest a high potential for investigations in various research subjects. PMID:26134813
Single-image phase retrieval using an edge illumination X-ray phase-contrast imaging setup
Diemoz, Paul C.; Vittoria, Fabio A.; Hagen, Charlotte K.; Endrizzi, Marco; Coan, Paola; Brun, Emmanuel; Wagner, Ulrich H.; Rau, Christoph; Robinson, Ian K.; Bravin, Alberto; Olivo, Alessandro
2015-01-01
A method is proposed which enables the retrieval of the thickness or of the projected electron density of a sample from a single input image acquired with an edge illumination phase-contrast imaging setup. The method assumes the case of a quasi-homogeneous sample, i.e. a sample with a constant ratio between the real and imaginary parts of its complex refractive index. Compared with current methods based on combining two edge illumination images acquired in different configurations of the setup, this new approach presents advantages in terms of simplicity of acquisition procedure and shorter data collection time, which are very important especially for applications such as computed tomography and dynamical imaging. Furthermore, the fact that phase information is directly extracted, instead of its derivative, can enable a simpler image interpretation and be beneficial for subsequent processing such as segmentation. The method is first theoretically derived and its conditions of applicability defined. Quantitative accuracy in the case of homogeneous objects as well as enhanced image quality for the imaging of complex biological samples are demonstrated through experiments at two synchrotron radiation facilities. The large range of applicability, the robustness against noise and the need for only one input image suggest a high potential for investigations in various research subjects. PMID:26134813
Bawolin, Nahshon K; Dolovich, Allan T; Chen, Daniel X B; Zhang, Chris W J
2015-08-01
In tissue engineering, the cell and scaffold approach has shown promise as a treatment to regenerate diseased and/or damaged tissue. In this treatment, an artificial construct (scaffold) is seeded with cells, which organize and proliferate into new tissue. The scaffold itself biodegrades with time, leaving behind only newly formed tissue. The degradation qualities of the scaffold are critical during the treatment period, since the change in the mechanical properties of the scaffold with time can influence cell behavior. To observe in time the scaffold's mechanical properties, a straightforward method is to deform the scaffold and then characterize scaffold deflection accordingly. However, experimentally observing the scaffold deflection is challenging. This paper presents a novel study on characterization of mechanical properties of scaffolds by phase contrast imaging and finite element modeling, which specifically includes scaffold fabrication, scaffold imaging, image analysis, and finite elements (FEs) modeling of the scaffold mechanical properties. The innovation of the work rests on the use of in-line phase contrast X-ray imaging at 20 KeV to characterize tissue scaffold deformation caused by ultrasound radiation forces and the use of the Fourier transform to identify movement. Once deformation has been determined experimentally, it is then compared with the predictions given by the forward solution of a finite element model. A consideration of the number of separate loading conditions necessary to uniquely identify the material properties of transversely isotropic and fully orthotropic scaffolds is also presented, along with the use of an FE as a form of regularization. PMID:25902011
NASA Astrophysics Data System (ADS)
Cui, Huakun; Wang, Dayong; Wang, Yunxin; Liu, Changgeng; Zhao, Jie; Li, Yan
2010-10-01
As the lensless Fourier transform digital holography is applied into the microscopic phase-contrast imaging on the live cells, the motion of the cells will lead to the non-coplanarity phenomena between the object and the reference source. This could result in the imaging aberration. An effective and robust autofocus procedure based on the phase distribution is presented in the paper. With the initial measurement of the distance between the reference source and the hologram, the optimum parameters corresponding to the phase-contrast image can be achieved by a single hologram, combined with the linearity fitting. The lensless Fourier transform digital holographic system is built and the experiments on the phase-contrast imaging of the live cervical carcinoma cells are performed. Finally, the good experiment results are demonstrated. Both the theoretical analysis and the experimental investigation verify the feasibility and validity of the automatic procedure for the non-coplanar aberration compensation.
Low-dose phase contrast x-ray medical imaging.
Arfelli, F; Assante, M; Bonvicini, V; Bravin, A; Cantatore, G; Castelli, E; Dalla Palma, L; Di Michiel, M; Longo, R; Olivo, A; Pani, S; Pontoni, D; Poropat, P; Prest, M; Rashevsky, A; Tromba, G; Vacchi, A; Vallazza, E; Zanconati, F
1998-10-01
Phase contrast x-ray imaging is a powerful technique for the detection of low-contrast details in weakly absorbing objects. This method is of possible relevance in the field of diagnostic radiology. In fact, imaging low-contrast details within soft tissue does not give satisfactory results in conventional x-ray absorption radiology, mammography being a typical example. Nevertheless, up to now all applications of the phase contrast technique, carried out on thin samples, have required radiation doses substantially higher than those delivered in conventional radiological examinations. To demonstrate the applicability of the method to mammography we produced phase contrast images of objects a few centimetres thick while delivering radiation doses lower than or comparable to doses needed in standard mammographic examinations (typically approximately 1 mGy mean glandular dose (MGD)). We show images of a custom mammographic phantom and of two specimens of human breast tissue obtained at the SYRMEP bending magnet beamline at Elettra, the Trieste synchrotron radiation facility. The introduction of an intensifier screen enabled us to obtain phase contrast images of these thick samples with radiation doses comparable to those used in mammography. Low absorbing details such as 50 microm thick nylon wires or thin calcium deposits (approximately 50 microm) within breast tissue, invisible with conventional techniques, are detected by means of the proposed method. We also find that the use of a bending magnet radiation source relaxes the previously reported requirements on source size for phase contrast imaging. Finally, the consistency of the results has been checked by theoretical simulations carried out for the purposes of this experiment. PMID:9814522
Differential phase contrast X-ray imaging system and components
Stutman, Daniel; Finkenthal, Michael
2014-07-01
A differential phase contrast X-ray imaging system includes an X-ray illumination system, a beam splitter arranged in an optical path of the X-ray illumination system, and a detection system arranged in an optical path to detect X-rays after passing through the beam splitter.
White Light Phase-conjugate Lensless Image Projection
P. Hribek; M. C. Gower
1989-01-01
The lensless projection in white light of images with ? 30 µ;m resolution has been demonstrated using phase-conjugate reflections from a self-pumped BaTiO3 crystal which was simultaneously illuminated with red, green and blue laser light. The relative beam incident intensities were crucial in reducing holographic photoerasure and cross-talk effects.
Geometrically Decoupled Phased Array Coils for Mouse Imaging
Bhatia, Sahil
2010-07-14
. In this work five different coils for mouse imaging at 200MHz are presented: a 16 leg trombone design quadrature birdcage coil and four geometrically decoupled volume phased array coils. The first mouse array coil is a two saddle quadrature coil with a...
Real time phase diversity advanced image processing and wavefront sensing
NASA Astrophysics Data System (ADS)
Dolne, Jean J.; Menicucci, Paul; Miccolis, David; Widen, Ken; Seiden, Harold; Vachss, Frederick; Schall, Harold
2007-09-01
This paper will describe a state-of-the-art approach to real time wavefront sensing and image enhancement. It will explore Boeing existing technology that realizes a 50 Hz frame rate (with a path to 1 KHz and higher). At this higher rate, Phase diversity will be readily applicable to compensate for distortions of large dynamic bandwidth such as those of the atmosphere. We will describe various challenges in aligning a two-camera phase diversity system. Such configurations make it almost impossible to process the captured images without additional upgrade in the algorithm to account for alignment errors. An example of an error is the relative misalignment of the two images, the "best-focus" and the diversity image where it is extremely hard to maintain alignment to less than a fraction of one pixel. We will show that the algorithm performance increases dramatically when we account for these errors in the phase diversity estimation process. Preliminary evaluation has assessed a NIIRS increase of ~ 3 from the "best-focus" to the enhanced image. Such a performance improvement would greatly increase the operating range (or, equivalently, decrease the weight) of many optical systems.
Para-Hydrogen-Enhanced Gas-Phase Magnetic Resonance Imaging
Bouchard, Louis-S.; Kovtunov, Kirill V.; Burt, Scott R.; Anwar,M. Sabieh; Koptyug, Igor V.; Sagdeev, Renad Z.; Pines, Alexander
2007-02-23
Herein, we demonstrate magnetic resonance imaging (MRI) inthe gas phase using para-hydrogen (p-H2)-induced polarization. A reactantmixture of H2 enriched in the paraspin state and propylene gas is flowedthrough a reactor cell containing a heterogenized catalyst, Wilkinson'scatalyst immobilized on modified silica gel. The hydrogenation product,propane gas, is transferred to the NMR magnet and is spin-polarized as aresult of the ALTADENA (adiabatic longitudinal transport and dissociationengenders net alignment) effect. A polarization enhancement factor of 300relative to thermally polarized gas was observed in 1D1H NMR spectra.Enhancement was also evident in the magnetic resonance images. This isthe first demonstration of imaging a hyperpolarized gaseous productformed in a hydrogenation reaction catalyzed by a supported catalyst.This result may lead to several important applications, includingflow-through porous materials, gas-phase reaction kinetics and adsorptionstudies, and MRI in low fields, all using catalyst-free polarizedfluids.
Partially coherent phase imaging with simultaneous source recovery
Jingshan, Zhong; Tian, Lei; Dauwels, Justin; Waller, Laura
2014-01-01
We propose a new method for phase retrieval that uses partially coherent illumination created by any arbitrary source shape in Köhler geometry. Using a stack of defocused intensity images, we recover not only the phase and amplitude of the sample, but also an estimate of the unknown source shape, which describes the spatial coherence of the illumination. Our algorithm uses a Kalman filtering approach which is fast, accurate and robust to noise. The method is experimentally simple and flexible, so should find use in optical, electron, X-ray and other phase imaging systems which employ partially coherent light. We provide an experimental demonstration in an optical microscope with various condenser apertures. PMID:25657890
Implications of a new phase function for autonomous underwater imaging
NASA Astrophysics Data System (ADS)
Fournier, G. R.; Sanjuan-Calzado, V.; Trees, C.
2014-05-01
Autonomous underwater vehicles do not have sufficient communications bandwidth over long ranges to send back real time images even for monitoring purposes. Autonomous imaging from underwater vehicles will therefore, require realtime imaging system performance prediction in order to ensure that the vehicle can position itself at a range that will allow it to take an image of the scene or target of interest at the required resolution and contrast level. Ideally the inherent optical properties of the surrounding waters should be measured onboard. This may not be feasible or only a restricted set may be measurable. In order to improve the prediction of the imaging performance, a physics-based analytic phase function that could effectively exploit any a priori or in-situ measured parameters would be extremely helpful. Such a new physics-based analytic phase function has been derived and tested against exact scattering codes. Among other features it is sufficiently precise to allow an accurate determination of the backscatter ratio based on an estimate of the mean index of refraction. The new formulation shows clearly why the backscatter ratio, which is the dominant factor in determining imaging range, is insensitive to the inverse power of the size distribution and almost entirely controlled by the mean index of refraction. This new formulation also has a direct application to improve inverse radiative transfer equation (RTE) modeling for estimating inherent optical properties (total absorption and total backscattering) from measured apparent optical properties (ocean color).
3D quantitative phase imaging of neural networks using WDT
NASA Astrophysics Data System (ADS)
Kim, Taewoo; Liu, S. C.; Iyer, Raj; Gillette, Martha U.; Popescu, Gabriel
2015-03-01
White-light diffraction tomography (WDT) is a recently developed 3D imaging technique based on a quantitative phase imaging system called spatial light interference microscopy (SLIM). The technique has achieved a sub-micron resolution in all three directions with high sensitivity granted by the low-coherence of a white-light source. Demonstrations of the technique on single cell imaging have been presented previously; however, imaging on any larger sample, including a cluster of cells, has not been demonstrated using the technique. Neurons in an animal body form a highly complex and spatially organized 3D structure, which can be characterized by neuronal networks or circuits. Currently, the most common method of studying the 3D structure of neuron networks is by using a confocal fluorescence microscope, which requires fluorescence tagging with either transient membrane dyes or after fixation of the cells. Therefore, studies on neurons are often limited to samples that are chemically treated and/or dead. WDT presents a solution for imaging live neuron networks with a high spatial and temporal resolution, because it is a 3D imaging method that is label-free and non-invasive. Using this method, a mouse or rat hippocampal neuron culture and a mouse dorsal root ganglion (DRG) neuron culture have been imaged in order to see the extension of processes between the cells in 3D. Furthermore, the tomogram is compared with a confocal fluorescence image in order to investigate the 3D structure at synapses.
Fortes, J P
1997-01-01
For pt.I see ibid., vol.44, pp.259-70 (1997). The performance of the maximum likelihood closed loop circuits, proposed in part I for phase aberration correction in phased array imaging systems, is analysed. This analysis is helpful in designing and also in determining the tracking mode phase error variance performance of both closed loop circuits (1-D and 2-D). It is an approximate analysis, suitable under small errors conditions, and considered accurate for high values of the signal to noise ratio. PMID:18244125
Diagnosis of breast cancer biopsies using quantitative phase imaging
NASA Astrophysics Data System (ADS)
Majeed, Hassaan; Kandel, Mikhail E.; Han, Kevin; Luo, Zelun; Macias, Virgilia; Tangella, Krishnarao; Balla, Andre; Popescu, Gabriel
2015-03-01
The standard practice in the histopathology of breast cancers is to examine a hematoxylin and eosin (H&E) stained tissue biopsy under a microscope. The pathologist looks at certain morphological features, visible under the stain, to diagnose whether a tumor is benign or malignant. This determination is made based on qualitative inspection making it subject to investigator bias. Furthermore, since this method requires a microscopic examination by the pathologist it suffers from low throughput. A quantitative, label-free and high throughput method for detection of these morphological features from images of tissue biopsies is, hence, highly desirable as it would assist the pathologist in making a quicker and more accurate diagnosis of cancers. We present here preliminary results showing the potential of using quantitative phase imaging for breast cancer screening and help with differential diagnosis. We generated optical path length maps of unstained breast tissue biopsies using Spatial Light Interference Microscopy (SLIM). As a first step towards diagnosis based on quantitative phase imaging, we carried out a qualitative evaluation of the imaging resolution and contrast of our label-free phase images. These images were shown to two pathologists who marked the tumors present in tissue as either benign or malignant. This diagnosis was then compared against the diagnosis of the two pathologists on H&E stained tissue images and the number of agreements were counted. In our experiment, the agreement between SLIM and H&E based diagnosis was measured to be 88%. Our preliminary results demonstrate the potential and promise of SLIM for a push in the future towards quantitative, label-free and high throughput diagnosis.
NASA Astrophysics Data System (ADS)
Jenkins, Micah; Gaylord, Thomas K.
2015-03-01
Most quantitative phase microscopy methods require the use of custom-built or modified microscopic configurations which are not typically available to most bio/pathologists. There are, however, phase retrieval algorithms which utilize defocused bright-field images as input data and are therefore implementable in existing laboratory environments. Among these, deterministic methods such as those based on inverting the transport-of-intensity equation (TIE) or a phase contrast transfer function (PCTF) are particularly attractive due to their compatibility with Köhler illuminated systems and numerical simplicity. Recently, a new method has been proposed, called multi-filter phase imaging with partially coherent light (MFPI-PC), which alleviates the inherent noise/resolution trade-off in solving the TIE by utilizing a large number of defocused bright-field images spaced equally about the focal plane. Despite greatly improving the state-ofthe- art, the method has many shortcomings including the impracticality of high-speed acquisition, inefficient sampling, and attenuated response at high frequencies due to aperture effects. In this report, we present a new method, called bright-field quantitative phase microscopy (BFQPM), which efficiently utilizes a small number of defocused bright-field images and recovers frequencies out to the partially coherent diffraction limit. The method is based on a noiseminimized inversion of a PCTF derived for each finite defocus distance. We present simulation results which indicate nanoscale optical path length sensitivity and improved performance over MFPI-PC. We also provide experimental results imaging live bovine mesenchymal stem cells at sub-second temporal resolution. In all, BFQPM enables fast and accurate phase imaging with unprecedented spatial resolution using widely available bright-field microscopy hardware.
Split-step complex Padé-Fourier depth migration
Linbin Zhang; James W. Rector; G. Michael Hoversten; Sergey Fomel
2007-01-01
We present a split-step complex Padé-Fourier migration method based on the one-way wave equation. The downward-continuation operator is split into two downward-continuation operators: one operator is a phase-shift operator and the other operator is a finite-difference operator. A complex treatment of the propagation operator is applied to mitigate inaccuracies and instabilities due to evanescent waves. It produces high-quality images of
A grating-based single-shot x-ray phase contrast and diffraction method for in vivo imaging
Bennett, Eric E.; Kopace, Rael; Stein, Ashley F.; Wen Han [National Heart, Lung, and Blood Institute, National Institutes of Health, Imaging Physics Section, Translational Medicine Branch, 10 Center Drive, MSC 1061, Bethesda, Maryland 20892 (United States)
2010-11-15
Purpose: The purpose of this study is to develop a single-shot version of the grating-based phase contrast x-ray imaging method and demonstrate its capability of in vivo animal imaging. Here, the authors describe the principle and experimental results. They show the source of artifacts in the phase contrast signal and optimal designs that minimize them. They also discuss its current limitations and ways to overcome them. Methods: A single lead grid was inserted midway between an x-ray tube and an x-ray camera in the planar radiography setting. The grid acted as a transmission grating and cast periodic dark fringes on the camera. The camera had sufficient spatial resolution to resolve the fringes. Refraction and diffraction in the imaged object manifested as position shifts and amplitude attenuation of the fringes, respectively. In order to quantify these changes precisely without imposing a fixed geometric relationship between the camera pixel array and the fringes, a spatial harmonic method in the Fourier domain was developed. The level of the differential phase (refraction) contrast as a function of hardware specifications and device geometry was derived and used to guide the optimal placement of the grid and object. Both ex vivo and in vivo images of rodent extremities were collected to demonstrate the capability of the method. The exposure time using a 50 W tube was 28 s. Results: Differential phase contrast images of glass beads acquired at various grid and object positions confirmed theoretical predictions of how phase contrast and extraneous artifacts vary with the device geometry. In anesthetized rats, a single exposure yielded artifact-free images of absorption, differential phase contrast, and diffraction. Differential phase contrast was strongest at bone-soft tissue interfaces, while diffraction was strongest in bone. Conclusions: The spatial harmonic method allowed us to obtain absorption, differential phase contrast, and diffraction images, all from a single raw image and is feasible in live animals. Because the sensitivity of the method scales with the density of the gratings, custom microfabricated gratings should be superior to off-the-shelf lead grids.
Harmon, Katherine J; Miao, Houxun; Gomella, Andrew A; Bennett, Eric E; Foster, Barbara A; Bhandarkar, Priya; Wen, Han
2015-04-21
X-ray phase contrast imaging based on grating interferometers detects the refractive index distribution of an object without relying on radiation attenuation, thereby having the potential for reduced radiation absorption. These techniques belong to the broader category of optical wavefront measurement, which requires stepping the phase of the interference pattern to obtain a pixel-wise map of the phase distortion of the wavefront. While phase stepping traditionally involves mechanical scanning of a grating or mirror, we developed electromagnetic phase stepping (EPS) for imaging with compact sources to obviate the need for mechanical movement. In EPS a solenoid coil is placed outside the x-ray tube to shift its focal spot with a magnetic field, causing a relative movement between the projection of the sample and the interference pattern in the image. Here we present two embodiments of this method. We verified experimentally that electromagnetic and mechanical phase stepping give the same results and attain the same signal-to-noise ratios under the same radiation dose. We found that the relative changes of interference fringe visibility were within 3.0% when the x-ray focal spot was shifted by up to 1.0 mm in either direction. We conclude that when using x-ray tube sources, EPS is an effective means of phase stepping without the need for mechanical movement. PMID:25803511
IMAGING RED BLOOD CELL DYNAMICS BY QUANTITATIVE PHASE MICROSCOPY
Popescu, Gabriel; Park, YoungKeun; Choi, Wonshik; Dasari, Ramachandra R.; Feld, Michael S.; Badizadegan, Kamran
2008-01-01
Red blood cells (RBCs) play a crucial role in health and disease, and structural and mechanical abnormalities of these cells have been associated with important disorders such as Sickle cell disease and hereditary cytoskeletal abnormalities. Although several experimental methods exist for analysis of RBC mechanical properties, optical methods stand out as they enable collecting mechanical and dynamic data from live cells without physical contact and without the need for exogenous contrast agents. In this report, we present quantitative phase microscopy techniques that enable imaging RBC membrane fluctuations with nanometer sensitivity at arbitrary time scales from milliseconds to hours. We further provide a theoretical framework for extraction of membrane mechanical and dynamical properties using time series of quantitative phase images. Finally, we present an experimental approach to extend quantitative phase imaging to 3-dimensional space using tomographic methods. By providing non-invasive methods for imaging mechanics of live cells, these novel techniques provide an opportunity for high-throughput analysis and study of RBC mechanical properties in health and disease. PMID:18387320
Dynamic phase imaging and processing of moving biological organisms
NASA Astrophysics Data System (ADS)
Creath, Katherine; Goldstein, Goldie
2012-03-01
This paper describes recent advances in developing a new, novel interference Linnik microscope system and presents images and data of live biological samples. The specially designed optical system enables instantaneous 4-dimensional video measurements of dynamic motions within and among live cells without the need for contrast agents. "Label-free" measurements of biological objects in reflection using harmless light levels are possible without the need for scanning and vibration isolation. This instrument utilizes a pixelated phase mask enabling simultaneous measurement of multiple interference patterns taking advantage of the polarization properties of light enabling phase image movies in real time at video rates to track dynamic motions and volumetric changes. Optical thickness data are derived from phase images after processing to remove the background surface shape to quantify changes in cell position and volume. Data from a number of different pond organisms will be presented, as will measurements of human breast cancer cells with the addition of various agents that break down the cells. These data highlight examples of the image processing involved and the monitoring of different biological processes.
Das, Mini; Liang, Zhihua
2014-11-01
In this Letter, we propose the first single-shot, noninterferometric x-ray imaging method for simultaneous retrieval of absorption, phase, and differential-phase imagery with quantitative accuracy. Our method utilizes a photon-counting spectral x-ray detector in conjunction with a simplified transport-of-intensity equation for coded-aperture phase-contrast imaging to efficiently solve the retrieval problem. This method can utilize an incoherent and polychromatic (clinical or laboratory) x-ray tube and can enable retrieval for a wide range and composition of material properties. The proposed method has been validated via computer simulations and is expected to significantly benefit applications that are sensitive to complexity of measurement, radiation dose and imaging time. PMID:25361350
Dynamic phase imaging utilizing a 4-dimensional microscope system
NASA Astrophysics Data System (ADS)
Creath, Katherine
2011-03-01
This paper describes a new, novel interference Linnik microscope system and presents images and data of live biological samples. The specially designed optical system enables instantaneous 4-dimensional video measurements of dynamic motions within and among live cells without the need for contrast agents. This "label-free", vibration insensitive imaging system enables measurement of biological objects in reflection using harmless light levels with a variety of magnifications and wavelengths with fields of view from several hundred microns up to a millimeter. At the core of the instrument is a phase measurement camera (PMC) enabling simultaneous measurement of multiple interference patterns utilizing a pixelated phase mask taking advantage of the polarization properties of light. Utilizing this technology enables the creation of phase image movies in real time at video rates so that dynamic motions and volumetric changes can be tracked. Objects are placed on a reflective surface in liquid under a coverslip. Phase values are converted to optical thickness data enabling volumetric, motion and morphological studies. Data from a number of different organisms such as flagellates and rotifers will be presented, as will measurements of human breast cancer cells with the addition of various agents that break down the cells. These data highlight examples of monitoring different biological processes and motions.
Dynamic phase imaging utilizing a 4-dimensional microscope system.
Creath, Katherine
2011-02-21
This paper describes a new, novel interference Linnik microscope system and presents images and data of live biological samples. The specially designed optical system enables instantaneous 4-dimensional video measurements of dynamic motions within and among live cells without the need for contrast agents. This "label-free", vibration insensitive imaging system enables measurement of biological objects in reflection using harmless light levels with a variety of magnifications and wavelengths with fields of view from several hundred microns up to a millimeter. At the core of the instrument is a phase measurement camera (PMC) enabling simultaneous measurement of multiple interference patterns utilizing a pixelated phase mask taking advantage of the polarization properties of light. Utilizing this technology enables the creation of phase image movies in real time at video rates so that dynamic motions and volumetric changes can be tracked. Objects are placed on a reflective surface in liquid under a coverslip. Phase values are converted to optical thickness data enabling volumetric, motion and morphological studies. Data from a number of different organisms such as flagellates and rotifers will be presented, as will measurements of human breast cancer cells with the addition of various agents that break down the cells. These data highlight examples of monitoring different biological processes and motions. PMID:24357901
Phase Closure Image Reconstruction for Future VLTI Instrumentation
Mercedes E. Filho; Stephanie Renard; Paulo Garcia; Gilles Duvert; Gaspard Duchene; Eric Thiebaut; John Young; Olivier Absil; Jean-Phillipe Berger; Thomas Beckert; Sebastian Hoenig; Dieter Schertl; Gerd Weigelt; Leonardo Testi; Eric Tatuli; Virginie Borkowski; Michael de Becker; Jean Surdej; Bernard Aringer; Joseph Hron; Thomas Lebzelter; Andrea Chiavassa; Romano Corradi; Tim Harries
2008-10-02
Classically, optical and near-infrared interferometry have relied on closure phase techniques to produce images. Such techniques allow us to achieve modest dynamic ranges. In order to test the feasibility of next generation optical interferometers in the context of the VLTI-spectro-imager (VSI), we have embarked on a study of image reconstruction and analysis. Our main aim was to test the influence of the number of telescopes, observing nights and distribution of the visibility points on the quality of the reconstructed images. Our results show that observations using six Auxiliary Telescopes (ATs) during one complete night yield the best results in general and is critical in most science cases; the number of telescopes is the determining factor in the image reconstruction outcome. In terms of imaging capabilities, an optical, six telescope VLTI-type configuration and ~200 meter baseline will achieve 4 mas spatial resolution, which is comparable to ALMA and almost 50 times better than JWST will achieve at 2.2 microns. Our results show that such an instrument will be capable of imaging, with unprecedented detail, a plethora of sources, ranging from complex stellar surfaces to microlensing events.
Quantitative investigation of phase retrieval from x-ray phase-contrast tomographic images
H. O. Moser; K. Banas; A. Chen; T. Vo Nghia; L. K. Jian; S. M. P. Kalaiselvi; G. Liu; S. M. Maniam; P. D. Gu; S. W. Wilkins; T. E. Gureyev; S. C. Mayo; M. Cholewa; Z. J. Li
2008-01-01
X-ray phase-contrast tomographic microimaging is a powerful tool to reveal the internal structure of opaque soft-matter objects that are not easily seen in standard absorption contrast. In such low Z materials, the phase shift of X-rays transmitted can be important as compared to the absorption. An easy experimental set up that exploits refractive contrast formation can deliver images that are
A kind of phase-based image matching technique
NASA Astrophysics Data System (ADS)
Xiao, Zhitao; Wu, Jun; Geng, Lei; Wang, Jianming; Xu, Nini
2009-07-01
Image matching is one of the most important techniques in intelligent systems and is widely applied in many fields. Firstly, based on integrated feature congruency, interesting target detection algorithm in complex natural backgrounds images is studied in this paper. By detecting the abrupt changes, we can detect interesting target areas. In this paper, the local image information is obtained by logGabor filter banks, and is represented by a collection of separate features. The integrated features consist of some separable significant features. The integrated feature congruency model is presented based on the integrated feature. We gain improved integrated feature congruency model by compensating noise. Then, we get a new kind of phase-based image matching method (PIM) by combining this model and Rotation Invariant Phase Only Correlation (RIPOC) algorithm. Experimental results show that the PIM algorithm is effective in detecting interesting targets and locating the matching targets exactly. This algorithm is invariant to image illumination, contrast, rotation and scaling. And this model is robust, general and accords with the human vision system (HVS) characteristics.
Extreme-ultraviolet lensless Fourier-transform holography.
Lee, S H; Naulleau, P; Goldberg, K A; Cho, C H; Jeong, S; Bokor, J
2001-06-01
We demonstrate 100-nm-resolution holographic aerial image monitoring based on lensless Fourier-transform holography at extreme-UV (EUV) wavelengths, using synchrotron-based illumination. This method can be used to monitor the coherent imaging performance of EUV lithographic optical systems. The system has been implemented in the EUV phase-shifting point-diffraction interferometer recently developed at Lawrence Berkeley National Laboratory. Here we introduce the idea of the holographic aerial image-recording technique and present imaging performance characterization results for a 10x Schwarzschild objective, a prototype EUV lithographic optic. The results are compared with simulations, and good agreement is obtained. Various object patterns, including phase-shift-enhanced patterns, have been studied. Finally, the application of the holographic aerial image-recording technique to EUV multilayer mask-blank defect characterization is discussed. PMID:18357280
Wavelet digital filter method for image processing of 3D measurement profilometry
NASA Astrophysics Data System (ADS)
Wang, Y. S.; Fu, S.; Xu, J. Q.; Zhou, C. I.; Si, S. C.; Gao, C. Y.
2006-02-01
Fourier Transform Profilometry and Phase Shifting are two important methods in 3-D measurement of body. Phase-shifting requires exact Phase-shifting sets, and more than an image collected, therefore its application is limited. Fourier Transform Profilometry required only an image, and calculated phase value of each point, measurement is higher degree of precision and wide range, its application is not limited. Wavelet Digital Filter and Fourier Transform Profilometry are combined, higher spectrum and direction components removed, kept useful components, raised dividing phase degree of precision, phase information of measured body resolved. This paper presents the analysis above the calculus and the results of simulated experiment.
Optimization of grating-based phase-contrast imaging setup
NASA Astrophysics Data System (ADS)
Baturin, Pavlo; Shafer, Mark
2014-03-01
Phase contrast imaging (PCI) technology has emerged over the last decade as a novel imaging technique capable of probing phase characteristics of an object as complimentary information to conventional absorption properties. In this work, we identified and provided a rationale for optimization of key parameters that determine the performance of a Talbot-Lau PCI system. The study used the Fresnel wave propagation theory and system geometry to predict optimal grating alignment conditions necessary for producing maximum-phase contrast. The moiré fringe pattern frequency and angular orientation produced in the X-ray detector plane were studied as functions of the gratings' axial rotation. The effect of axial displacement between source-to-phase (L) and phase-to-absorption (d) gratings, on system contrast, was discussed in detail. The L-d regions of highest contrast were identified, and the dependence of contrast on the energy of the X-ray spectrum was also studied. The predictions made in this study were tested experimentally and showed excellent agreement. The results indicated that the PCI system performance is highly sensitive to alignment. The rationale and recommendations made should serve as guidance in design, development, and optimization of Talbot-Lau PCI systems.
Fourier Analysis Jan Wiegerinck
Wiegerinck, Jan
Fourier Analysis Jan Wiegerinck version March 12, 2010 Korteweg Â de Vries Instituut, Universiteit Index 57 iii #12;iv CONTENTS Fourier Analysis can indicate the study of Fourier transformations, Fourier of elementary Fourier Analysis, Functional Analysis and Integration theory. At the UvA the courses Integration
Simple phase-only optical decryption with misalignment-free input.
Vu, Tien Viet; Kim, Nam; Nam, Chang-Seup
2007-02-01
An improved optical decryption system based on kinogram encoding is proposed. The decrypted phase image is obtained by optically descrambling the encrypted image with the decrypting phase key. Only a single Fourier lens is needed to generate intensity patterns from the decrypted phase image. The design and simulation results have confirmed the proposed technique as a novel, simple, and robust decryption architecture. PMID:17215926
Simple phase-only optical decryption with misalignment-free input
Tien Viet Vu; Nam Kim; Chang-Seup Nam
2007-01-01
An improved optical decryption system based on kinogram encoding is proposed. The decrypted phase image is obtained by optically descrambling the encrypted image with the decrypting phase key. Only a single Fourier lens is needed to generate intensity patterns from the decrypted phase image. The design and simulation results have confirmed the proposed technique as a novel, simple, and robust
Boundary value problem for phase retrieval from unidirectional X-ray differential phase images.
Gasilov, Sergei; Mittone, Alberto; Horng, Annie; Bravin, Alberto; Baumbach, Tilo; Geith, Tobias; Reiser, Maximilian; Coan, Paola
2015-05-18
The phase retrieval problem can be reduced to the second order partial differential equation. In order to retrieve the absolute values of the X-ray phase and to minimize the reconstruction artifacts we defined the mixed inhomogeneous boundary condition using available a priori information about the sample. Finite element technique was used to solve the boundary value problem. The approach is validated on numerical and experimental phantoms. In order to demonstrate a possible application of the method, we have processed an entire tomographic set of differential phase images and estimated the magnitude of the refractive index decrement for some tissues inside complex biomedical samples. PMID:26074580
Subnanosecond time-resolved imaging using a rf phase-sensitive image converter camera
Klaus W. Berndt; Joseph R. Lakowicz
1993-01-01
Common high-speed gated proximity focused multichannel plate image intensifiers allow for a typical gate width of 3 to 5 ns. We have studied an alternative way to accomplish sub- nanosecond time-resolved imaging by operating a gatable proximity focused intensifier as a radio-frequency phase-sensitive camera. In this operating mode, we apply a dc bias voltage between the photocathode and the microchannel
NASA Astrophysics Data System (ADS)
Zuo, Chao; Chen, Qian; Tian, Lei; Waller, Laura; Asundi, Anand
2015-08-01
The well-known transport of intensity equation (TIE) allows the phase of a coherent field to be retrieved non-interferometrically given positive defined intensity measurements and appropriate boundary conditions. However, in many cases like the optical microscopy, the imaging systems often involve extended and polychromatic sources for which the effect of the partial coherence is not negligible. In this work, we present a phase-space formulation for the TIE for analyzing phase retrieval under partially coherent illumination. The conventional TIE is reformulated in the joint space-spatial frequency domain using Wigner distribution functions. The phase-space formulation clarifies the physical meaning of the phase of partially coherent fields, and enables explicit account of partial coherence effects on phase retrieval. The correspondence between the Wigner distribution function and the light field in geometric optics limit further enables TIE to become a simple yet effective approach to realize high-resolution light field imaging for slowly varying phase specimens, in a purely computational way.
Vining, B A; Bossio, R E; Marshall, A G
1999-01-15
Phase correction of FT-ICR data yields an absorption spectrum that offers a gain by up to a factor of 2 in mass resolving power (at half-maximum peak height), compared to conventional magnitude-mode display. That improvement is equivalent to doubling the applied magnetic field strength, without loss in signal-to-noise (S/N) ratio, provided that the time-domain data are padded with an equal number of zeroes before FFT. Our simple, visual, user-interactive algorithm quickly corrects for zero-order and first-order variation of phase with frequency. We find that the theoretical mass resolving power enhancement for pressure-limited absorption-mode over magnitude-mode line shape depends on the collision mechanism: factor of 1.40 for hard sphere vs 3(1/2) for Langevin (ion: induced dipole). Thus, the experimental enhancement in mass resolving power (factor of 1.43 +/- 0.09) for isotopically resolved peaks in the FT-ICR mass spectra of electrosprayed bovine carbonic anhydrase (approximately 29 kDa) directly supports the hard-sphere collision model. Optimal implementation of phasing requires the following: (a) a delay between excitation and detection of less than half of one sampling interval to avoid baseline "roll" and Gibb's oscillations; (b) accurate analog-to-digital conversion; (c) a sufficiently long acquisition period to yield several data points per absorption-mode peak width at half-maximum peak height; and (d) avoidance of FT-ICR apodization functions (e.g., Hamming and Hanning) that suppress the initial time-domain data. Pulsed single-frequency excitation (duration much less than the reciprocal of the Nyquist bandwidth) can eliminate higher than first-order variation of phase with frequency. Phased FT-ICR spectra should prove especially desirable for analysis of complex mixtures, for resolving isotopic distributions in electrosprayed multiply charged macromolecules and for characterizing ion collisions (and thus ion size and shape). PMID:9949733
Choi, Woo Jhon
2014-01-01
Optical coherence tomography (OCT) is a non-invasive optical imaging technique that allows the three-dimensional structure of biological tissue to be visualized with micrometer resolution. In ophthalmology OCT has the ...
Wood, Bayden R; Bambery, Keith R; Dixon, Matthew W A; Tilley, Leann; Nasse, Michael J; Mattson, Eric; Hirschmugl, Carol J
2014-10-01
New methods are needed to rapidly identify malaria parasites in blood smears. The coupling of a Focal Plane Array (FPA) infrared microscope system to a synchrotron light source at IRENI enables rapid molecular imaging at high spatial resolution. The technique, in combination with hyper-spectral processing, enables imaging and diagnosis of early stage malaria parasites at the single cell level in a blood smear. The method relies on the detection of distinct lipid signatures associated with the different stages of the malaria parasite and utilises resonant Mie extended multiplicative scatter correction to pre-process the spectra followed by full bandwidth image deconvolution to resolve the single cells. This work demonstrates the potential of focal plane technology to diagnose single cells in a blood smear. Brighter laboratory based infrared sources, optical refinements and higher sensitive detectors will soon see the emergence of focal plane array imaging in the clinical environment. PMID:25055796
Automated Galaxy Morphology: A Fourier Approach
S. C. Odewahn; S. H. Cohen; R. A. Windhorst; N. S. Philip
2001-10-11
We use automated surface photometry and pattern classification techniques to morphologically classify galaxies. The two-dimensional light distribution of a galaxy is reconstructed using Fourier series fits to azimuthal profiles computed in concentric elliptical annuli centered on the galaxy. Both the phase and amplitude of each Fourier component have been studied as a function of radial bin number for a large collection of galaxy images using principal component analysis. We find that up to 90 percent of the variance in many of these Fourier profiles may be characterized in as few as 3 principal components and their use substantially reduces the dimensionality of the classification problem. We use supervised learning methods in the form of artificial neural networks to train galaxy classifiers that detect morphological bars at the 85-90 percent confidence level and can identify the Hubble type with a 1-sigma scatter of 1.5 steps on the 16-step stage axis of the revised Hubble system. Finally, we systematically characterize the adverse effects of decreasing resolution and S/N on the quality of morphological information predicted by these classifiers.
Borislav Vasic
2011-01-01
Using numerical simulations, we investigate the realization of self-focusing media using two-dimensional graded photonic crystals and their applications for imaging and non-imaging purposes. The two-dimensional graded photonic crystals consist of spatially varying cylindrical holes drilled in a dielectric host. By controlling the gradient of the refractive index and the thickness of the self-focusing medium, it is possible to obtain either
Water-fat imaging with direct phase encoding.
Xiang, Q S; An, L
1997-01-01
A new method is introduced for water-fat imaging. With three acquisitions, a general direct phase encoding (DPE) of the chemical shift information is achieved. Pixels containing both water and fat are solved directly. Pixels with only a single component are resolved with local and global orientation filters, which use phase information from neighboring pixels. The fact that a single component is more likely to be water than fat in living tissues is also useful. A second pass solution yields water and fat images with superior signal-to-noise ratio. Unlike other methods, DPE does not rely on the error-prone phase unwrapping; also, it easily handles disconnected tissues. Because the magnetization vectors of water and fat are sampled not only at parallel or antiparallel, they can be not only separated but also identified respectively, which is desirable for routine clinical work. DPE has been implemented on several imagers at various field strengths and has been demonstrated in a large number of clinical cases to be useful and robust in various parts of the body. PMID:9400843
Improved Phased Array Imaging of a Model Jet
NASA Technical Reports Server (NTRS)
Dougherty, Robert P.; Podboy, Gary G.
2010-01-01
An advanced phased array system, OptiNav Array 48, and a new deconvolution algorithm, TIDY, have been used to make octave band images of supersonic and subsonic jet noise produced by the NASA Glenn Small Hot Jet Acoustic Rig (SHJAR). The results are much more detailed than previous jet noise images. Shock cell structures and the production of screech in an underexpanded supersonic jet are observed directly. Some trends are similar to observations using spherical and elliptic mirrors that partially informed the two-source model of jet noise, but the radial distribution of high frequency noise near the nozzle appears to differ from expectations of this model. The beamforming approach has been validated by agreement between the integrated image results and the conventional microphone data.
STATISTICAL IMAGE MODELLING USING INTERSCALE PHASE RELATIONSHIPS OF COMPLEX WAVELET COEFFICIENTS
Kingsbury, Nick
property of complex wavelet co- efficients for image denoising: 3. Interscale phase consistency: The phasesSTATISTICAL IMAGE MODELLING USING INTERSCALE PHASE RELATIONSHIPS OF COMPLEX WAVELET COEFFICIENTS of wavelet coefficients and ten- dency of wavelets bases to diagonalise images allows us to break the problem
Imaging voltage-dependent cell motions with heterodyne MachZehnder phase microscopy
Seung, Sebastian
Imaging voltage-dependent cell motions with heterodyne MachZehnder phase microscopy Christopher microscope capable of quantitative phase imaging of biological samples with subnanometer sensitivity wavelengths and can be imaged in their natural states only via the phase shifts they induce in transmitted
Fingler, Jeff; Zawadzki, Robert J.; Park, Susanna S.; Morse, Lawrence S.; Schwartz, Daniel M.; Fraser, Scott E.; Werner, John S.
2012-01-01
Purpose. To demonstrate the application of phase-variance optical coherence tomography (pvOCT) for contrast agent–free in vivo imaging of volumetric retinal microcirculation in the human foveal region and for extraction of foveal avascular zone dimensions. Methods. A custom-built, high-speed Fourier-domain OCT retinal imaging system was used to image retinas of two healthy subjects and eight diabetic patients. Through the acquisition of multiple B-scans for each scan location, phase differences between consecutive scans were extracted and used for phase-variance contrast, identifying motion signals from within blood vessels and capillaries. The en face projection view of the inner retinal layers segmented out from volumetric pvOCT data sets allowed visualization of a perfusion network with the foveal avascular zone (FAZ). In addition, the authors presented 2D retinal perfusion maps with pseudo color-coded depth positions of capillaries. Results. Retinal vascular imaging with pvOCT provides accurate measurements of the FAZ area and its morphology and a volumetric perfusion map of microcapillaries. In this study using two images from each fundus fluorescein angiography (FA) and pvOCT, the measured average areas of the FAZ from two healthy subjects were below 0.22 mm2, and each of eight diabetic patients had an enlarged FAZ area, larger than 0.22 mm2. Moreover, the FAZ areas demonstrated a significant correlation (r = 0.91) between measurements from FA and pvOCT. Conclusions. The high-speed pvOCT allows contrast agent–free visualization of capillary networks in the human foveal region that is analogous to fundus FA imaging. This could allow for noninvasive diagnosis and progression monitoring of diabetic retinopathy in clinical settings. PMID:22125275
Automatic Selection of Mask and Arterial Phase Images for Temporally Resolved MR Digital
Zabih, Ramin
X-ray angiography, where image postprocessing has been used frequently to improve vasculatureAutomatic Selection of Mask and Arterial Phase Images for Temporally Resolved MR Digital for selecting arterial phase images and mask images to generate an optimal sum- mary arteriogram. A paired
Bahram Javidi; Guanshen Zhang; Jian Li
1996-01-01
Optical image encryption and security using random phase encoding techniques have been proposed recently. We present optical experimental results for image encryption and security. The results show that for the image encryption, the image can be well encrypted using random phase masks with a limited number of pixels. We also tested the performance of the optical system for security verification
Experience with 800 x 800 virtual phase and 500 x 500 three-phase CCD imagers
NASA Technical Reports Server (NTRS)
Hlivak, R. J.; Henry, J. P.; Pilcher, C. B.
1984-01-01
A description of the Galileo/Institute for Astronomy charge-coupled device (CCD) imaging system and its initial operation has been presented previously. Originally designed to operate a 500 x 500 backside illuminated three-phase CCD, the system has been modified to allow use of either the 500 x 500 sensor or the TI 800 x 800 virtual phase CCD. The modifications for the operation of the virtual phase CCD and current system performance with each type of sensor are discussed. A description is given of the implementation of various techniques discovered at the Jet Propulsion Laboratory that improve imager performance. These techniques include tri-level clocking of the virtual phase CCD to eliminate spurious charge generation in the serial register, the use of ultraviolet light flood with the backside thinned 500 x 500 three-phase device to dramatically improve the quantum efficiency in the blue, and the practical elimination of deferred charge in the three-phase device. Results of astronomical observations with each sensor are presented.
Optimized phase encoding for optical compressive sensing imaging
NASA Astrophysics Data System (ADS)
Sun, Jianchao; Xu, Feng
2013-12-01
Compressive Sensing (CS) indicates that when the signal of interest is sparse or compressible (i.e., sparse after mathematical transformation), one can take a small number of linear projection measurements from the signal, and reconstruct the signal almost perfectly through proper algorithm. The feature of the CS has great potential applications in that high-resolution imaging is highly desirable while large size detector array is unavailable, such as those in ultraviolet or infrared wavelength region or that in aircrafts and satellites working condition when the data transmission is a key issue. However, CS technique still faces challenges in the signal sampling and reconstruction. Firstly, detector measurements must be nonnegative in linear optical system which is different from digital image processing. Secondly, blurring caused by practical optical system should be considered, which will destroy the effect of reconstruction. In this paper, we discuss some kinds of phase encoding which could be used in practice imaging system. We make a compensation to solve the non-negative problem when CS applied in the practical optical system, use a small size detector to receive a general image degrading model, and reconstructed image from the single, low-solution and noisy observation through a fast and feasible non-linear algorithm, the result proves our system is robust and feasible.
Dunin-Borkowski, Rafal E.
-axis electron hologram and b) a defocused bright-field image of the end of a bundle of single-walled carbon or magnetic induction. Although it is tempting to interpret such phase contours directly in terms lines recorded using off-axis electron holography from a wire comprising a bundle of single-walled
Fourier-domain multichannel autofocus for synthetic aperture radar.
Liu, Kuang-Hung; Munson, David C
2011-12-01
Synthetic aperture radar (SAR) imaging suffers from image focus degradation in the presence of phase errors in the received signal due to unknown platform motion or signal propagation delays. We present a new autofocus algorithm, termed Fourier-domain multichannel autofocus (FMCA), that is derived under a linear algebraic framework, allowing the SAR image to be focused in a noniterative fashion. Motivated by the mutichannel autofocus (MCA) approach, the proposed autofocus algorithm invokes the assumption of a low-return region, which generally is provided within the antenna sidelobes. Unlike MCA, FMCA works with the collected polar Fourier data directly and is capable of accommodating wide-angle monostatic SAR and bistatic SAR scenarios. Most previous SAR autofocus algorithms rely on the prior assumption that radar's range of look angles is small so that the phase errors can be modeled as varying along only one dimension in the collected Fourier data. And, in some cases, implicit assumptions are made regarding the SAR scene. Performance of such autofocus algorithms degrades if the assumptions are not satisfied. The proposed algorithm has the advantage that it does not require prior assumptions about the range of look angles, nor characteristics of the scene. PMID:21606028
Banas, A; Banas, K; Breese, M B H; Loke, J; Heng Teo, B; Lim, S K
2012-08-01
Synchrotron radiation-based Fourier transform infra-red (SR-FTIR) micro-imaging has been developed as a rapid, direct and non-destructive technique. This method, taking advantage of the high brightness and small effective source size of synchrotron light, is capable of exploring the molecular chemistry within the microstructures of microscopic particles without their destruction at high spatial resolutions. This is in contrast to traditional "wet" chemical methods, which, during processing for analysis, often caused destruction of the original samples. In the present study, we demonstrate the potential of SR-FTIR micro-imaging as an effective way to accurately identify microscopic particles deposited within latent fingerprints. These particles are present from residual amounts of materials left on a person's fingers after handling such materials. Fingerprints contaminated with various types of powders, creams, medications and high explosive materials (3-nitrooxy-2,2-bis(nitrooxymethyl)propyl nitrate (PETN), 1,3,5-trinitro-1,3,5-triazinane (RDX), 2-methyl-1,3,5-trinitrobenzene (TNT)) deposited on various - daily used - substrates have been analysed herein without any further sample preparation. A non-destructive method for the transfer of contaminated fingerprints from hard-to-reach areas of the substrates to the place of analysis is also presented. This method could have a significant impact on forensic science and could dramatically enhance the amount of information that can be obtained from the study of fingerprints. PMID:22693711
Downing, Kenneth H.; Glaeser, Robert M.
2008-03-28
Relatively large values of objective-lens defocus must normally be used to produce detectable levels of image contrast for unstained biological specimens, which are generally weak phase objects. As a result, a subsequent restoration operation must be used to correct for oscillations in the contrast transfer function (CTF) at higher resolution. Currently used methods of CTF-correction assume the ideal case in which Friedel mates in the scattered wave have contributed pairs of Fourier components that overlap with one another in the image plane. This"ideal" situation may be only poorly satisfied, or not satisfied at all, as the particle size gets smaller, the defocus value gets larger, and the resolution gets higher. We have therefore investigated whether currently used methods of CTF correction are also effective in restoring the single-sideband image information that becomes displaced (delocalized) by half (or more) the diameter of a particle of finite size. Computer simulations are used to show that restoration either by"phase flipping" or by multiplying by the CTF recovers only about half of the delocalized information. The other half of the delocalized information goes into a doubly defocused"twin" image of the type produced during optical reconstruction of an in-line hologram. Restoration with a Wiener filter is effective in recovering the delocalized information only when the signal-to-noise ratio (S/N) is orders of magnitude higher than that which exists in low-dose images of biological specimens, in which case the Wiener filter approaches division by the CTF (i.e. the formal inverse). For realistic values of the S/N, however, the"twin image" problem seenwith a Wiener filter is very similar to that seen when either phase flipping or multiplying by the CTF are used for restoration. The results of these simulations suggest that CTF correction is a poor alternative to using a Zernike-type phase plate when imaging biological specimens, in which case the images can be recorded in a close-to-focus condition, and delocalization of high-resolution information is thus minimized.
Signal Processing:Fourier Signal Processing:Fourier
Rimon, Elon
Signal Processing:Fourier #12;Signal Processing:Fourier Fourier methods · Continous signals FS) signals DFS Discrete Fourier Series DFT Discrete Fourier Transform #12;Signal Processing:Fourier #12;Signal Processing:Fourier #12;Signal Processing:Fourier Example: The square wave For this case ao = 0
Fourier–Bessel rotational invariant eigenimages
Zhao, Zhizhen; Singer, Amit
2013-01-01
We present an efficient and accurate algorithm for principal component analysis (PCA) of a large set of two-dimensional images and, for each image, the set of its uniform rotations in the plane and its reflection. The algorithm starts by expanding each image, originally given on a Cartesian grid, in the Fourier–Bessel basis for the disk. Because the images are essentially band limited in the Fourier domain, we use a sampling criterion to truncate the Fourier–Bessel expansion such that the maximum amount of information is preserved without the effect of aliasing. The constructed covariance matrix is invariant to rotation and reflection and has a special block diagonal structure. PCA is efficiently done for each block separately. This Fourier–Bessel-based PCA detects more meaningful eigenimages and has improved denoising capability compared to traditional PCA for a finite number of noisy images. PMID:23695317
NASA Technical Reports Server (NTRS)
Middlebrook, Ann M.; Iraci, Laura T.; Mcneill, Laurie S.; Koehler, Birgit G.; Wilson, Margaret A.; Saastad, Ole W.; Tolbert, Margaret A.; Hanson, David R.
1993-01-01
Fourier transform-infrared (FTIR) spectroscopy was used to examine films representative of stratospheric sulfuric acid aerosols. Thin films of sulfuric acid were formed in situ by the condensed phase reaction of SO3 with H2O. FTIR spectra show that the sulfuric acid films absorb water while cooling in the presence of water vapor. Using stratospheric water pressures, the most dilute solutions observed were greater than 40 wt % before simultaneous ice formation and sulfuric acid freezing occurred. FTIR spectra also revealed that the sulfuric acid films crystallized mainly as sulfuric acid tetrahydrate (SAT). Crystallization occurred either when the composition was about 60 wt% H2SO4 or after ice formed on the films at temperatures 1-4 K below the ice frost point. Finally, we determined that the melting point for SAT depended on the background water pressure and was 216-219 K in the presence of 4 x 10(exp -4) Torr H2O. Our results suggest that once frozen, sulfuric acid aerosols in the stratosphere are likely to melt at these temperatures, 30 K colder than previously thought.
Sadeghi, Mahdi; Zeeb, Mohsen; Kalaee, Mohammad R
2010-01-01
The combination of vapor-phase generation (VPG) and Fourier-transform infrared (FTIR) spectrometry was performed as an alternative analytical technique for the determination of water-soluble penicillin G (PENG). Samples were transferred into a heated reactor, and a potassium iodate solution was injected into the reactor. Carbon monoxide (CO) generated under these conditions was carried via a N(2) gas carrier stream inside the IR gas cell, and the corresponding FTIR spectra were continuously recorded as a function of time. Analytical measurements were made using the maximum absorbance of the CO band at 2170 +/- 4 cm(-1). Various factors influencing the analytical signals were evaluated and selected. The figures of merit of the proposed method involve a linear calibration curve over the range of 3 to 320 mg L(-1), a limit of detection of 0.5 mg L(-1) and a precision of 2.6%. The method was successfully applied to PENG determination in pharmaceutical preparations. PMID:20467133
STATISTICAL IMAGE MODELING USING DISTRIBUTION OF RELATIVE PHASE IN THE COMPLEX WAVELET DOMAIN
Oraintara, Soontorn
STATISTICAL IMAGE MODELING USING DISTRIBUTION OF RELATIVE PHASE IN THE COMPLEX WAVELET DOMAIN An Vo wavelet subband from different natural images. Moreover, a new image feature based on the fRP is proposed the performance. 1. INTRODUCTION Many applications in image processing such as image compression, denoising
Patel, Imran I; Harrison, Wesley J; Kerns, Jemma G; Filik, Jacob; Wehbe, Katia; Carmichael, Paul L; Scott, Andrew D; Philpott, Mike P; Frogley, Mark D; Cinque, Gianfelice; Martin, Francis L
2012-10-01
Normal function and physiology of the epidermis is maintained by the regenerative capacity of this tissue via adult stem cells (SCs). However, definitive identifying markers for SCs remain elusive. Infrared (IR) spectroscopy exploits the ability of cellular biomolecules to absorb in the mid-IR region (? = 2.5-25 ?m), detecting vibrational transitions of chemical bonds. In this study, we exploited the cell's inherent biochemical composition to discriminate SCs of the inter-follicular skin epidermis based on IR-derived markers. Paraffin-embedded samples of human scalp skin (n = 4) were obtained, and 10-?m thick sections were mounted for IR spectroscopy. Samples were interrogated in transmission mode using synchrotron radiation-based Fourier-transform IR (FTIR) microspectroscopy (15 × 15 ?m) and also imaged employing globar-source FTIR focal plane array (FPA) imaging (5.4 × 5.4 ?m). Dependent on the location of derived spectra, wavenumber-absorbance/intensity relationships were examined using unsupervised principal component analysis. This approach showed clear separation and spectral differences dependent on cell type. Spectral biomarkers concurrently associated with segregation of SCs, transit-amplifying cells and terminally-differentiated cells of epidermis were primarily PO(2)(-) vibrational modes (1,225 and 1,080 cm(-1)), related to DNA conformational alterations. FPA imaging coupled with hierarchical cluster analysis also indicated the presence of specific basal layer cells potentially originating from the follicular bulge, suggested by co-clustering of spectra. This study highlights PO (2) (-) vibrational modes as potential putative SC markers. PMID:22945554
SAR image quality effects of damped phase and amplitude errors
NASA Astrophysics Data System (ADS)
Zelenka, Jerry S.; Falk, Thomas
The effects of damped multiplicative, amplitude, or phase errors on the image quality of synthetic-aperture radar systems are considered. These types of errors can result from aircraft maneuvers or the mechanical steering of an antenna. The proper treatment of damped multiplicative errors can lead to related design specifications and possibly an enhanced collection capability. Only small, high-frequency errors are considered. Expressions for the average intensity and energy associated with a damped multiplicative error are presented and used to derive graphic results. A typical example is used to show how to apply the results of this effort.
Spatiotemporal Characterization of a Fibrin Clot Using Quantitative Phase Imaging
Gannavarpu, Rajshekhar; Bhaduri, Basanta; Tangella, Krishnarao; Popescu, Gabriel
2014-01-01
Studying the dynamics of fibrin clot formation and its morphology is an important problem in biology and has significant impact for several scientific and clinical applications. We present a label-free technique based on quantitative phase imaging to address this problem. Using quantitative phase information, we characterized fibrin polymerization in real-time and present a mathematical model describing the transition from liquid to gel state. By exploiting the inherent optical sectioning capability of our instrument, we measured the three-dimensional structure of the fibrin clot. From this data, we evaluated the fractal nature of the fibrin network and extracted the fractal dimension. Our non-invasive and speckle-free approach analyzes the clotting process without the need for external contrast agents. PMID:25386701
Computational methods for microfluidic microscopy and phase-space imaging
NASA Astrophysics Data System (ADS)
Pegard, Nicolas Christian Richard
Modern optical devices are made by assembling separate components such as lenses, objectives, and cameras. Traditionally, each part is optimized separately, even though the trade-offs typically limit the performance of the system overall. This component-based approach is particularly unfit to solve the new challenges brought by modern biology: 3D imaging, in vivo environments, and high sample throughput. In the first part of this thesis, we introduce a general method to design integrated optical systems. The laws of wave propagation, the performance of available technology, as well as other design parameters are combined as constraints into a single optimization problem. The solution provides qualitative design rules to improve optical systems as well as quantitative task-specific methods to minimize loss of information. Our results have applications in optical data storage, holography, and microscopy. The second part of this dissertation presents a direct application. We propose a more efficient design for wide-field microscopy with coherent light, based on double transmission through the sample. Historically, speckle noise and aberrations caused by undesired interferences have made coherent illumination unpopular for imaging. We were able to dramatically reduce speckle noise and unwanted interferences using optimized holographic wavefront reconstruction. The resulting microscope not only yields clear coherent images with low aberration---even in thick samples---but also increases contrast and enables optical filtering and in-depth sectioning. In the third part, we develop new imaging techniques that better respond to the needs of modern biology research through implementing optical design optimization. Using a 4D phase-space distribution, we first represent the state and propagation of incoherent light. We then introduce an additional degree of freedom by putting samples in motion in a microfluidic channel, increasing image diversity. From there, we develop a design that is minimally invasive yet optimizes the transfer of information from sample to detector. This optimization best responds to the desired imaging application. We present three microfluidic devices which can all be implemented as a compact add-on device for commercial microscopes. The first is a flow-scanning structured illumination microfluidic microscopy device demonstrating enhanced resolution in 2D. The second is a method for 3D deconvolution microscopy with a tilted channel to acquire and deconvolve gradually defocused images. Finally, we demonstrate optical projection microscopic tomography with simultaneous phase and intensity imaging capabilities in 3D by combining flow-scanning and optical acquisition in phase space. Experimental results utilize yeast cells as well as live C.elegans.. In the fourth part, we show that optical system optimization also has non-imaging applications such as solar cell engineering. Instead of looking for an optical setup that maximizes the transfer of information, we implement inexpensive surface wrinkles and folds in the layered structure of organic solar cells and optimize their surface density. This strategy enhances light trapping and further improves the electric conversion of solar energy.
High-sensitive full-range optical vibrometry based on Fourier-domain optical coherence tomography
NASA Astrophysics Data System (ADS)
Subhash, Hrebesh M.; Leahy, Martin
2014-03-01
Optical vibrometery based on low coherence Fourier-domain optical coherence tomography (FD-OCT) technique are well capable for providing depth resolved vibration information in comparison with conventional laser based vibrometery. Recently, there has been growing interest in developing coherence-domain vibrometry for various clinical and pre-clinical applications. However, a major drawback of the conventional vibrometer based on Fourier-domain low coherence interferometry is the complex-conjugate ambiguity. This is because in FD-OCT, the detected real valued spectral interferogram is Fourier transformed to localize the scatter within the sample. The Fourier transform of a real valued function is Hermitian, so the reconstructed image is symmetric with respect to the zero-phase delay of the interferometer, leading to ambiguity in interpretation of the resulted OCT images. In this paper, we introduce a full range optical coherence vibrometry to utilize the whole imaging range of the spectrometer. The mirror image elimination is based on the linear phase modulation of the interferometer's reference arm mirror and with an algorithm that exploits Hilbert transform to obtain full range complex imaging.
Computational techniques in propagation-based x-ray phase imaging
NASA Astrophysics Data System (ADS)
Petruccelli, Jonathan C.; Tahir, Sajjad; Bashir, Sajid; Pan, Adam; Tian, Lei; Xu, Ling; MacDonald, C. A.; Barbastathis, George
2014-09-01
X-ray phase imaging utilizes a variety of techniques to render phase information as intensity contrast and these intensity images can in some cases be processed to retrieve quantitative phase. A subset of these techniques use free space propagation to generate phase contrast and phase can be recovered by inverting differential equations governing propagation. Two techniques to generate quantitative phase reconstructions from a single phase contrast image are described in detail, along with regularization techniques to reduce the influence of noise. Lastly, a recently developed technique utilizing a binary-amplitude grid to enhance signal strength in propagation-based techniques is described.
Quantification of dispersed phase concentration using light sheet imaging methods
NASA Astrophysics Data System (ADS)
Knowles, Philip L.; Kiger, Ken T.
2012-03-01
With the prevalence of particle image velocimetry (PIV) as a quantitative tool for fluid mechanics diagnostics, its application for analyzing complicated multiphase flows has been steadily increasing over the last several decades. While the primary issue in using PIV for multiphase flows is in separating the information of the phases for independent analysis with a minimum of spurious "cross-talk," an equally crucial but often overlooked point is in the accurate quantitative measurement of the dispersed phase concentration. Accurate concentration measurement is important due to the fact that the dispersed phase is often heterogeneously distributed in both space and time, either due to a non-uniformity of the source of particulates (such as a spray nozzle or sediment boundary) or due to inertial migration of the particles even from originally homogeneous spatial distributions. In the current work, we examine the effects of light sheet profile distortion and attenuation by tracer seeding particles, as well as reflected light from local wall boundaries on the effective light sheet thickness. The effective thickness is critical for concentration measurements, as it dictates the dispersed phase detection volume. A direct calibration method is demonstrated to measure the effective light sheet thickness in a water/glass bead system, which shows that systematic bias errors on the order of 30% can result if the reflective bed condition is not accounted for, and the errors can be as high as 50% or more if a single-point measure of the sheet width is used.
NASA Astrophysics Data System (ADS)
Yadav, A. K.; Vashisth, Sunanda; Singh, Hukum; Singh, Kehar
2015-06-01
We propose a watermarking scheme for phase images, based on the use of devil's vortex Fresnel lens (DVFL) as a phase mask. The DVFL provides much-desired parameter-rich phase masks which contribute to the enhanced security of the scheme in addition to overcoming the problem of axis alignment in the optical setup. The scheme uses gyrator transform (GT) in the input and the frequency domains to encrypt the input phase image before combining it with a host image. The scheme is validated for its efficacy, and analyzed for its sensitivity to various encryption parameters. Finally, it is examined for its robustness against occlusion and noise attacks.
Quantization noise and its reduction in lensless Fourier digital holography.
Pandey, Nitesh; Hennelly, Bryan
2011-03-01
Digital holography is an imaging technique that enables recovery of topographic 3D information about an object under investigation. In digital holography, an interference pattern is recorded on a digital camera. Therefore, quantization of the recorded hologram is an integral part of the imaging process. We study the influence of quantization error in the recorded holograms on the fidelity of both the intensity and phase of the reconstructed image. We limit our analysis to the case of lensless Fourier off-axis digital holograms. We derive a theoretical model to predict the effect of quantization noise and we validate this model using experimental results. Based on this, we also show how the resultant noise in the reconstructed image, as well as the speckle that is inherent in digital holography, can be conveniently suppressed by standard speckle reduction techniques. We show that high-quality images can be obtained from binary holograms when speckle reduction is performed. PMID:21364713
Evaluation of edge effect due to phase contrast imaging for mammography
Matsuo, Satoru; Katafuchi, Tetsuro; Tohyama, Keiko; Morishita, Junji; Yamada, Katsuhiko; Fujita, Hiroshi [Department of Radiology, Shiga University of Medical Science, Shiga (Japan); Department of Radiology, National Cardiovascular Center, Suita, Osaka (Japan); Kyoto College of Medical Technology, Kyoto, (Japan); Department of Health Sciences, School of Medicine, Kyushu University (Japan); Kyoto College of Medical Technology, Kyoto (Japan); Department of Intelligent Image Information, Graduate School of Medicine, Gifu University (Japan)
2005-08-15
It is well-known that the edge effect produced by phase contrast imaging results in the edge enhancement of x-ray images and thereby sharpens those images. It has recently been reported that phase contrast imaging using practical x-ray tubes with small focal spots has improved image sharpness as observed in the phase contrast imaging with x-ray from synchrotron radiation or micro-focus x-ray tubes. In this study, we conducted the phase contrast imaging of a plastic fiber and plant seeds using a customized mammography equipment with a 0.1 mm focal spot, and the improvement of image sharpness was evaluated in terms of spatial frequency response of the images. We observed that the image contrast of the plastic fiber was increased by edge enhancement, and, as predicted elsewhere, spectral analysis revealed that as the spatial frequencies of the x-ray images increased, so did the sharpness gained through phase contrast imaging. Thus, phase contrast imaging using a practical molybdenum anode tube with a 0.1 mm-focal spot would benefit mammography, in which the morphological detectability of small species such as micro-calcifications is of great concern. And detectability of tumor-surrounded glandular tissues in dense breast would be also improved by the phase contrast imaging.
Hybrid optonumerical quasi Fourier transform digital holographic camera
NASA Astrophysics Data System (ADS)
Doval, Ángel F.; Trillo, Cristina
2006-08-01
We present a novel hybrid digital holographic camera which shares most of the advantages of image-plane Fourier transform TV holography (TVH) and quasi-Fourier transform digital holography (QFTDH), whilst avoiding many of the drawbacks of both of them. As in TVH, it has a compact head where an objective lens is attached to accommodate objects of different sizes or placed at different distances; it is also free from aliasing artifacts produced by objects out of the field of view. As in QFTDH, the reconstruction of the object field (amplitude and phase) is accomplished by calculating just one fast Fourier transform (FFT) per hologram; light is spread over the sensor rather than being focused to produce an image, thus enabling the measurement in objects with very large radiance ranges. An optical imaging system (typically a zoom lens) selects the field of view and the working distance by projecting a reduced image of the object on the plane of a rectangular aperture. This image becomes the object for a lensless quasi-Fourier transform digital hologram, which is formed by making the light passing through the aperture to interfere with a reference beam diverging from its edge. This hologram is recorded with a video camera, digitized and numerically reconstructed by means of a single FFT. The function of the aperture is to crop the field of view to make the effective object size suitable to be recorded without aliasing on a sensor with a given pixel spacing; therefore, its size is determined by this spacing, the distance between the aperture and the sensor as well as by the wavelength of light.
Off-axis quantitative phase imaging processing using CUDA: toward real-time applications.
Pham, Hoa; Ding, Huafeng; Sobh, Nahil; Do, Minh; Patel, Sanjay; Popescu, Gabriel
2011-07-01
We demonstrate real time off-axis Quantitative Phase Imaging (QPI) using a phase reconstruction algorithm based on NVIDIA's CUDA programming model. The phase unwrapping component is based on Goldstein's algorithm. By mapping the process of extracting phase information and unwrapping to GPU, we are able to speed up the whole procedure by more than 18.8× with respect to CPU processing and ultimately achieve video rate for mega-pixel images. Our CUDA implementation also supports processing of multiple images simultaneously. This enables our imaging system to support high speed, high throughput, and real-time image acquisition and visualization. PMID:21750757
Fourier Transforms, Fourier Series and the FFT
NSDL National Science Digital Library
Lisette de Pillis
The goal of this module is to give students an understanding of the one-dimensional Fourier Transform, both mathematically and computationally, with a focus on finding periodicity in data. To motivate the study of the Fourier Transform, the students will be presented with certain application areas, such as searching for periodic patterns in CO2 data and differentiating between two sound signals using their power spectra. Students will explore some computational issues and challenges of the Discrete and Fast Fourier Transforms.
Zumbühl, Stefan; Scherrer, Nadim C; Eggenberger, Urs
2014-01-01
The interpretation of standard Fourier transform infrared spectra (FT-IR) on oil-based paint samples often suffers from interfering bands of the different compounds, namely, binder, oxidative aging products, carboxylates formed during aging, and several pigments and fillers. The distinction of the aging products such as ketone and carboxylic acid functional groups pose the next problem, as these interfere with the triglyceride esters of the oil. A sample preparation and derivatization technique using gaseous sulfur tetrafluoride (SF4), was thus developed with the aim to discriminate overlapping signals and achieve a signal enhancement on superposed compounds. Of particular interest in this context is the signal elimination of the broad carboxylate bands of the typical reaction products developing during the aging processes in oil-based paints, as well as signal interference originating from several typical pigments in this spectral range. Furthermore, it is possible to distinguish the different carbonyl-containing functional groups upon selective alteration. The derivatization treatment can be applied to both microsamples and polished cross sections. It increases the selectivity of the infrared spectroscopy technique in a fundamental manner and permits the identification and two-dimensional (2D) localization of binder components in aged paint samples at the micrometer scale. The combination of SF4 derivatization with high-resolution 2D FT-IR focal plane array (FPA) imaging delivers considerable advances to the study of micro-morphological processes involving organic compounds. PMID:24694702
Phase-shift estimation in sinusoidally illuminated images for lateral superresolution
Fienup, James R.
Phase-shift estimation in sinusoidally illuminated images for lateral superresolution Sapna A illumination has been used to obtain lateral superresolution and axial sectioning in images. In both of these techniques multiple images are taken with the object illuminated by a sinusoidal pat- tern, the phase
Matrix phased array (MPA) imaging technology for resistance spot welds
NASA Astrophysics Data System (ADS)
Na, Jeong K.; Gleeson, Sean T.
2014-02-01
A three-dimensional MPA probe has been incorporated with a high speed phased array electronic board to visualize nugget images of resistance spot welds. The primary application area of this battery operated portable MPA ultrasonic imaging system is in the automotive industry which a conventional destructive testing process is commonly adopted to check the quality of resistance spot welds in auto bodies. Considering an average of five-thousand spot welds in a medium size passenger vehicle, the amount of time and effort given to popping the welds and measuring nugget size are immeasurable in addition to the millions of dollars' worth of scrap metals recycled per plant per year. This wasteful labor intensive destructive testing process has become less reliable as auto body sheet metal has transitioned from thick and heavy mild steels to thin and light high strength steels. Consequently, the necessity of developing a non-destructive inspection methodology has become inevitable. In this paper, the fundamental aspects of the current 3-D probe design, data acquisition algorithms, and weld nugget imaging process are discussed.
Matrix phased array (MPA) imaging technology for resistance spot welds
Na, Jeong K.; Gleeson, Sean T. [Edison Welding Institute, 1250 Arthur E. Adams Drive, Columbus, OH 43221 (United States)
2014-02-18
A three-dimensional MPA probe has been incorporated with a high speed phased array electronic board to visualize nugget images of resistance spot welds. The primary application area of this battery operated portable MPA ultrasonic imaging system is in the automotive industry which a conventional destructive testing process is commonly adopted to check the quality of resistance spot welds in auto bodies. Considering an average of five-thousand spot welds in a medium size passenger vehicle, the amount of time and effort given to popping the welds and measuring nugget size are immeasurable in addition to the millions of dollars' worth of scrap metals recycled per plant per year. This wasteful labor intensive destructive testing process has become less reliable as auto body sheet metal has transitioned from thick and heavy mild steels to thin and light high strength steels. Consequently, the necessity of developing a non-destructive inspection methodology has become inevitable. In this paper, the fundamental aspects of the current 3-D probe design, data acquisition algorithms, and weld nugget imaging process are discussed.
Dual-Phase Cardiac Diffusion Tensor Imaging with Strain Correction
Stoeck, Christian T.; Kalinowska, Aleksandra; von Deuster, Constantin; Harmer, Jack; Chan, Rachel W.; Niemann, Markus; Manka, Robert; Atkinson, David; Sosnovik, David E.; Mekkaoui, Choukri; Kozerke, Sebastian
2014-01-01
Purpose In this work we present a dual-phase diffusion tensor imaging (DTI) technique that incorporates a correction scheme for the cardiac material strain, based on 3D myocardial tagging. Methods In vivo dual-phase cardiac DTI with a stimulated echo approach and 3D tagging was performed in 10 healthy volunteers. The time course of material strain was estimated from the tagging data and used to correct for strain effects in the diffusion weighted acquisition. Mean diffusivity, fractional anisotropy, helix, transverse and sheet angles were calculated and compared between systole and diastole, with and without strain correction. Data acquired at the systolic sweet spot, where the effects of strain are eliminated, served as a reference. Results The impact of strain correction on helix angle was small. However, large differences were observed in the transverse and sheet angle values, with and without strain correction. The standard deviation of systolic transverse angles was significantly reduced from 35.9±3.9° to 27.8°±3.5° (p<0.001) upon strain-correction indicating more coherent fiber tracks after correction. Myocyte aggregate structure was aligned more longitudinally in systole compared to diastole as reflected by an increased transmural range of helix angles (71.8°±3.9° systole vs. 55.6°±5.6°, p<0.001 diastole). While diastolic sheet angle histograms had dominant counts at high sheet angle values, systolic histograms showed lower sheet angle values indicating a reorientation of myocyte sheets during contraction. Conclusion An approach for dual-phase cardiac DTI with correction for material strain has been successfully implemented. This technique allows assessing dynamic changes in myofiber architecture between systole and diastole, and emphasizes the need for strain correction when sheet architecture in the heart is imaged with a stimulated echo approach. PMID:25191900
Fluorescence lifetime imaging of aerosol viscosity and phase
NASA Astrophysics Data System (ADS)
Pope, F. D.; Hosny, N. A.; Fitzgerald, C.; Kalberer, M.; Kuimova, M. K.
2012-04-01
The viscosity and phase of atmospheric aerosols are key properties that help define aerosol reactivity and hence aerosol aging. The viscosity and phase are strongly linked to the water content of aerosols and hence the aerosol hygroscopicity. The ability of chemical species to diffuse into the aerosol core, or be limited to surface reactions, is closely linked to the aerosol viscosity. In particular, the bulk reactivity of fast lived species with a limited lifetime is often diffusion limited. At present, there is a paucity of analytical techniques that can directly measure the viscosity and phase of atmospheric aerosol. This limits the physical chemical understanding of these important aerosol properties. We are developing the use of Fluorescence Lifetime Imaging (FLIM) techniques, which have previously been used for investigating cell viscosity, to probe the viscosity of atmospheric aerosol. The FLIM technique works by the insertion of novel fluorescent probes (molecular rotors) into the aerosol systems of interest (Kuimova et al.). The fluorescent lifetimes of these probes are dependent on the viscosity of the surrounding environment because the fluorescence competes with intramolecular rotation. In a highly viscous environment the rotation of the rotors is significantly hindered and hence the fluorescence is strongly perturbed. This technique allows the viscosity of model aerosols to be measured whilst varying the environmental conditions such as relative humidity and temperature. Initial results on both inorganic and organic aerosol systems will be presented and the effect of relative humidity on aerosol viscosity will be shown. The applicability and future extensions of the FLIM technique for probing aerosol viscosity will be discussed. Reference M.K. Kuimova, S.W. Botchway, A.W. Parker, M. Balaz, H.A. Collins, H.L. Anderson, K. Suhling, P.R. Ogilby. (2009) Imaging intracellular viscosity of a single cell during photoinduced cell death. Nature Chemistry 1, 69-73.
Paris-Sud XI, Université de
- nike [16, 17, 10]. D'autre part, des points d'intérêts comme ceux donnés par la méthode SIFT (Scale-Invariant Feature Transform) sont actuellement très utilisés car très efficaces [11]. A côté de ces approches methods : A color Fourier transform using geometric algebra [1]. Generalized Fourier descriptors
NASA Astrophysics Data System (ADS)
Ungermann, J.; Blank, J.; Dick, M.; Ebersoldt, A.; Friedl-Vallon, F.; Giez, A.; Guggenmoser, T.; Höpfner, M.; Jurkat, T.; Kaufmann, M.; Kaufmann, S.; Kleinert, A.; Krämer, M.; Latzko, T.; Oelhaf, H.; Olchewski, F.; Preusse, P.; Rolf, C.; Schillings, J.; Suminska-Ebersoldt, O.; Tan, V.; Thomas, N.; Voigt, C.; Zahn, A.; Zöger, M.; Riese, M.
2015-06-01
The Gimballed Limb Observer for Radiance Imaging of the Atmosphere (GLORIA) is an airborne infrared limb imager combining a two-dimensional infrared detector with a Fourier transform spectrometer. It was operated aboard the new German Gulfstream G550 High Altitude LOng Range (HALO) research aircraft during the Transport And Composition in the upper Troposphere/lowermost Stratosphere (TACTS) and Earth System Model Validation (ESMVAL) campaigns in summer 2012. This paper describes the retrieval of temperature and trace gas (H2O, O3, HNO3) volume mixing ratios from GLORIA dynamics mode spectra that are spectrally sampled every 0.625 cm-1. A total of 26 integrated spectral windows are employed in a joint fit to retrieve seven targets using consecutively a fast and an accurate tabulated radiative transfer model. Typical diagnostic quantities are provided including effects of uncertainties in the calibration and horizontal resolution along the line of sight. Simultaneous in situ observations by the Basic Halo Measurement and Sensor System (BAHAMAS), the Fast In-situ Stratospheric Hygrometer (FISH), an ozone detector named Fairo, and the Atmospheric chemical Ionization Mass Spectrometer (AIMS) allow a validation of retrieved values for three flights in the upper troposphere/lowermost stratosphere region spanning polar and sub-tropical latitudes. A high correlation is achieved between the remote sensing and the in situ trace gas data, and discrepancies can to a large extent be attributed to differences in the probed air masses caused by different sampling characteristics of the instruments. This 1-D processing of GLORIA dynamics mode spectra provides the basis for future tomographic inversions from circular and linear flight paths to better understand selected dynamical processes of the upper troposphere and lowermost stratosphere.
Oraintara, Soontorn
USING PHASE AND MAGNITUDE INFORMATION OF THE COMPLEX DIRECTIONAL FILTER BANK FOR TEXTURE IMAGE, Fontainebleau, 77305 France ABSTRACT This paper discusses how to utilize both magnitude and phase in- formation images. This paper discusses how magnitude and phase information of the complex directional lter bank
Handling Phase in Sparse Reconstruction for SAR: Imaging, Autofocusing, and Moving Targets
Ã?etin, MÃ¼jdat
Handling Phase in Sparse Reconstruction for SAR: Imaging, Autofocusing, and Moving Targets MÃ¼jdat, Shiraz, Iran Abstract We consider sparse image reconstruction methods for synthetic aperture radar (SAR) and discuss how issues related to the phase of the complex-valued SAR reflectivities and the phase
A new two-dimensional phase unwrapping algorithm for MRI images.
Hedley, M; Rosenfeld, D
1992-03-01
The phase of an image obtained with many magnetic resonance imaging techniques is related to some physical variable of interest. This phase needs to be unwrapped, which is complicated by the presence of noise and multiple objects of irregular shape. A new two-dimensional phase unwrapping algorithm is presented, along with simulation results. PMID:1556925
Phase-aware projection model for steganalysis of JPEG images
NASA Astrophysics Data System (ADS)
Holub, Vojt?ch; Fridrich, Jessica
2015-03-01
State-of-the-art JPEG steganographic algorithms, such as J-UNIWARD, are currently better detected in the spatial domain rather than the JPEG domain. Rich models built from pixel residuals seem to better capture the impact of embedding than features constructed as co-occurrences of quantized JPEG coefficients. However, when steganalyzing JPEG steganographic algorithms in the spatial domain, the pixels' statistical properties vary because of the underlying 8 × 8 pixel grid imposed by the compression. In order to detect JPEG steganography more accurately, we split the statistics of noise residuals based on their phase w.r.t. the 8 × 8 grid. Because of the heterogeneity of pixels in a decompressed image, it also makes sense to keep the kernel size of pixel predictors small as larger kernels mix up qualitatively different statistics more, losing thus on the detection power. Based on these observations, we propose a novel feature set called PHase Aware pRojection Model (PHARM) in which residuals obtained using a small number of small-support kernels are represented using first-order statistics of their random projections as in the projection spatial rich model PSRM. The benefit of making the features "phase-aware" is shown experimentally on selected modern JPEG steganographic algorithms with the biggest improvement seen for J-UNIWARD. Additionally, the PHARM feature vector can be computed at a fraction of computational costs of existing projection rich models.
NASA Astrophysics Data System (ADS)
Jeong, Min-Ok; Kim, Nam; Park, Jae-Hyeung; Jeon, Seok-Hee; Gil, Sang-Keun
2009-02-01
We propose a method generating elemental images for the auto-stereoscopic three-dimensional display technique, integral imaging, using phase-shifting digital holography. Phase shifting digital holography is a way recording the digital hologram by changing phase of the reference beam and extracting the complex field of the object beam. Since all 3D information is captured by the phase-shifting digital holography, the elemental images for any specifications of the lens array can be generated from single phase-shifting digital holography. We expanded the viewing angle of the generated elemental image by using the synthetic aperture phase-shifting digital hologram. The principle of the proposed method is verified experimentally.
Wide-field, high-resolution Fourier ptychographic microscopy
Yang, Changhuei
Wide-field, high-resolution Fourier ptychographic microscopy Guoan Zheng*, Roarke Horstmeyer, termed Fourier ptychographic microscopy (FPM), which iteratively stitches together a number of variably illuminated, low-resolution intensity images in Fourier space to produce a wide-field, high-resolution complex
Behne, Martin J; Sanchez, Susana; Barry, Nicholas P; Kirschner, Nina; Meyer, Wilfried; Mauro, Theodora M; Moll, Ingrid; Gratton, Enrico
2011-03-01
Calcium controls an array of key events in keratinocytes and epidermis: localized changes in Ca(2+) concentrations and their regulation are therefore especially important to assess when observing epidermal barrier homeostasis and repair, neonatal barrier establishment, in differentiation, signaling, cell adhesion, and in various pathological states. Yet, tissue- and cellular Ca(2+) concentrations in physiologic and diseased states are only partially known, and difficult to measure. Prior observations on the Ca(2+) distribution in skin were based on Ca(2+) precipitation followed by electron microscopy, or proton-induced X-ray emission. Neither cellular and/or subcellular localization could be determined through these approaches. In cells in vitro, fluorescent dyes have been used extensively for ratiometric measurements of static and dynamic Ca(2+) concentrations, also assessing organelle Ca(2+) concentrations. For lack of better methods, these findings together build the basis for the current view of the role of Ca(2+) in epidermis, their limitations notwithstanding. Here we report a method using Calcium Green 5N as the calcium sensor and the phasor-plot approach to separate raw lifetime components. Thus, fluorescence lifetime imaging (FLIM) enables us to quantitatively assess and visualize dynamic changes of Ca(2+) at light-microscopic resolution in ex vivo biopsies of unfixed epidermis, in close to in vivo conditions. Comparing undisturbed epidermis with epidermis following a barrier insult revealed major shifts, and more importantly, a mobilization of high amounts of Ca(2+) shortly following barrier disruption, from intracellular stores. These results partially contradict the conventional view, where barrier insults abrogate a Ca(2+) gradient towards the stratum granulosum. Ca(2+) FLIM overcomes prior limitations in the observation of epidermal Ca(2+) dynamics, and will allow further insights into basic epidermal physiology. PMID:21193994
Phase compensation of SAL imaging combining Rayleigh LGS with PGA in strong turbulence
NASA Astrophysics Data System (ADS)
Han, Yan-yan; Lu, Fang; Han, Xiang'e.; Liu, Chun-bo
2013-09-01
High imaging resolution can be achieved by using synthetic aperture ladar (SAL) with laser radiation source. The destruction of the signal phase information caused by atmospheric turbulence makes the optical heterodyne detection efficiency reduce. Therefore the imaging performance of SAL degraded seriously. The study on the influence of atmospheric turbulence on SAL imaging is of great significance and an effective compensation method of image is necessary to be found. Research shows that conventional phase gradient autofocus (PGA) algorithm has some improvement on SAL imaging only in weak turbulence. The mixed phase compensation method combining Rayleigh laser guide star (LGS) with PGA algorithm is presented based on the real-time detection of optical wavefront phase distortion with Rayleigh LGS and the phase compensation method of the SAL images. The phase distortion caused by different turbulence intensities with von Karman spectrum is estimated with Rayleigh LGS. SAL echo signals are compensated with the estimated phase and the PGA algorithm is implemented in the final imaging data. The results show that significant improvements of the SAL images in moderate turbulence are obtained and the images can be identified basically by using the mixed phase compensation method in strong turbulence. The focusing effect of the SAL images is improved effectively, and a higher SAL resolution is gained in azimuth. In addition, the research of SAL imaging compensation in atmospheric turbulence in a slant path is carried out for the first time, which is of great significance to the practical application of SAL.
NASA Astrophysics Data System (ADS)
Wong, Molly; Wu, Xizeng; Liu, Hong
2010-02-01
A significant challenge in the field of mammography that has yet to be overcome involves providing adequate image quality for detection and diagnosis, while minimizing the radiation dose to the patient. An emerging x-ray technology, high energy phase contrast imaging holds the potential to reduce the patient dose without compromising the image quality, which would benefit the early detection of breast cancer. The purpose of this preliminary study was to compare the image quality of high energy phase contrast images to conventional x-ray images at typical mammography energies. The experimental settings were selected to provide similar entrance exposures for the high and low energy images. Several phantoms were utilized in this study to provide a comprehensive image quality comparison, in an effort to investigate the clinical potential of high energy phase contrast imaging. An ACR phantom was utilized for quantitative comparison through an observer study, while a new tissue-equivalent phantom was utilized for a qualitative investigation. Finally, an acrylic-edge phantom was employed to provide an illustration of the edge enhancement in the phase contrast images as compared to the conventional images. The results from the multi-faceted comparison indicate the potential of high energy phase contrast imaging to provide comparable image quality at a similar or decreased patient dose.
Hierarchical security system using real-valued data and orthogonal code in Fourier domain
NASA Astrophysics Data System (ADS)
Kim, Hyun-Jun; Seo, Dong-Hoan; Hwang, Kwang-Il; Lim, Tae-Woo
2014-02-01
We propose a novel hierarchical encryption scheme using orthogonal code in Fourier domain and decryption based on interferometer system. The proposed system is composed of hierarchical ciphertexts with positive real values which can be applied for practical transmission such as Internet, and decryption keys with real valued function which has orthogonal characteristic in the decryption system. Since the original information is encrypted on the Fourier plane, the proposed encryption is more tolerant to loss of key information by scratching or cutting than encryption in a spatial domain. The resulting image using Fourier transform and an interferometer system with constant phase retarder is then decrypted by use of a ciphertext with different security level and each of decryption keys made from the multiplication of orthogonal code and random phase code in order to enhance the level of security. We demonstrate the efficiency of the proposed method and the fault-tolerance properties of data loss through several simulations.
Optical encryption for large-sized images using random phase-free method
Shimobaba, Tomoyoshi; Endo, Yutaka; Hirayama, Ryuji; Hiyama, Daisuke; Hasegawa, Satoki; Nagahama, Yuki; Sano, Marie; Sugie, Takashige; Ito, Tomoyoshi
2015-01-01
We propose an optical encryption framework that can encrypt and decrypt large-sized images beyond the size of the encrypted image using our two methods: random phase-free method and scaled diffraction. In order to record the entire image information on the encrypted image, the large-sized images require the random phase to widely diffuse the object light over the encrypted image; however, the random phase gives rise to the speckle noise on the decrypted images, and it may be difficult to recognize the decrypted images. In order to reduce the speckle noise, we apply our random phase-free method to the framework. In addition, we employ scaled diffraction that calculates light propagation between planes with different sizes by changing the sampling rates.
Fabrication of diffraction gratings for hard X-ray phase contrast imaging
C. David; J. Bruder; T. Rohbeck; C. Grünzweig; C. Kottler; A. Diaz; O. Bunk; F. Pfeiffer
2007-01-01
We have developed a method for X-ray phase contrast imaging, which is based on a grating interferometer. The technique is capable of recording the phase shift of hard X-rays travelling through a sample, which greatly enhances the contrast of low absorbing specimen compared to conventional amplitude contrast images. Unlike other existing X-ray phase contrast imaging methods, the grating interferometer also
Three-dimensional phase retrieval in propagation-based phase-contrast imaging
NASA Astrophysics Data System (ADS)
Ruhlandt, A.; Krenkel, M.; Bartels, M.; Salditt, T.
2014-03-01
We present a solution to the phase problem in near-field x-ray (propagation) imaging. The three-dimensional complex-valued index of refraction is reconstructed from a set of projections recorded in the near-field (Fresnel) setting at a single detector distance. The solution is found by an iterative algorithm based only on the measured data and the three-dimensional tomographic (Helgason-Ludwig) consistency constraint without the need for further a priori knowledge or other restrictive assumptions.
NASA Astrophysics Data System (ADS)
Jacobson, David L.; Arif, Muhammad; Bergmann, Luke; Ioffe, Alexander
1999-11-01
The neutron interferometry technique provides direct access to phase of the neutron wave. If properly applied, the use of phase information in imaging materials can provide an advantage over normal intensity techniques, which use absorption to provide image contrast. The National Institute of Standards and Technology Neutron Interferometry and Optics Facility has been working on new methods and devices to exploit the neutron phase information to image materials. We will present here the latest results of this effort and an overview of the instruments available at NIST for Neutron Phase Contrast Imaging.
Grating-based x-ray phase-contrast imaging at PETRA III
NASA Astrophysics Data System (ADS)
Hipp, A.; Beckmann, F.; Lytaev, P.; Greving, I.; Lottermoser, L.; Dose, T.; Kirchhof, R.; Burmester, H.; Schreyer, A.; Herzen, J.
2014-09-01
Conventional absorption-based imaging often lacks in good contrast at special applications like visualization of soft tissue or weak absorbing material in general. To overcome this limitation, several new X-ray phase-contrast imaging methods have been developed at synchrotron radiation facilities. Our aim was to establish the possibility of different phase-contrast imaging modalities at the Imaging Beamline (IBL, P05) and the High Energy Material Science beamline (HEMS, P07) at Petra III (DESY, Germany). Here we present the instrumentation and the status of the currently successfully established phase-contrast imaging techniques. First results from measurements of biomedical samples will be presented as demonstration.
Phase imaging by atomic force microscopy: analysis of living homoiothermic vertebrate cells.
Nagao, E; Dvorak, J A
1999-01-01
Atomic force microscope-based phase imaging in air is capable of elucidating variations in material properties such as adhesion, friction, and viscoelasticity. However, the interpretation of phase images of specimens in a fluid environment requires clarification. In this report, we systematically analyzed atomic force microscope-derived phase images of mica, glass, and collagen under the same conditions as used for living cells at various tapping forces; the resulting data provide critical information for the interpretation of phase images of living cells. The peripheral regions of COS-1 cells consistently show a more negative phase shift than the glass substrate in phase images at set-point amplitude: free amplitude (Asp/A0) = 0.6-0.8. In addition, at all Asp/A0 values suitable for phase imaging, tapping frequency appears to be high enough to ensure that phase shifts are governed primarily by stiffness. Consequently, phase imaging is capable of high resolution studies of the cellular surface by detecting localized variations in stiffness. We demonstrate that phase imaging of a bifurcating fiber in COS-1 cell cytoplasm is readily capable of a lateral resolution of approximately 30 nm. PMID:10354454
Phase Contrast X-ray Imaging of Shuttle Insulating Foam
NASA Technical Reports Server (NTRS)
Hu, Zhengwei
2005-01-01
X-ray radiation has been widely used for imaging applications since Rontgen first discovered X-rays over a century ago. Its large penetration depth makes it ideal for the nondestructive visualization of internal structure of materials or objects unobtainable otherwise. Currently widely used nondestructive evaluation (NDE) tools-X-ray radiography and tomography are absorption-based, and work well in highly absorbing materials where density or composition variations due to internal structure or defects are high enough to be spatially distinguished in terms of absorption contrast. However, in many cases where materials such as insulating foam are light-weight, the conventional absorption-based X-ray methods for NDE become less effective. Indeed, the low-density shuttle insulating foam used for flight mission poses a great challenge to the standard NDE tools in that the absorption contrast arising from internal defects of such a low- density material is either weak or indistinguishable. In this presentation, the latest progress in phase contrast X-ray imaging of internal defects of insulating foam will be presented and discussed, demonstrating new opportunities to solve challenging issues involved in advanced materials development and processing for space exploration.
Phase imaging and stiffness in tapping-mode atomic force microscopy
S. N. Magonov; V. Elings; M.-H. Whangbo
1997-01-01
The dependence of phase angles in tapping-mode atomic force microscopy on the magnitude of tip-sample repulsive interactions was investigated, and phase images of several hard and soft samples were recorded as a function of the free amplitude A0 and the set-point tapping amplitude Asp. The phase angle of probe oscillation increases with decreasing the set-point amplitude ratio AspA0. Phase imaging
Unsupervised malaria parasite detection based on phase spectrum.
Fang, Yuming; Xiong, Wei; Lin, Weisi; Chen, Zhenzhong
2011-01-01
In this paper, we propose a novel method for malaria parasite detection based on phase spectrum. The method first obtains the amplitude spectrum and phase spectrum for blood smear images through Quaternion Fourier Transform (QFT). Then it gets the reconstructed image based on Inverse Quaternion Fourier transform (IQFT) on a constant amplitude spectrum and the original phase spectrum. The malaria parasite areas can be detected easily from the reconstructed blood smear images. Extensive experiments have demonstrated the effectiveness of this novel method. PMID:22256196
Fourier analysis of active-region plage
A. G. de Wijn; B. De Pontieu; R. J. Rutten
2007-06-13
We study the dynamical interaction of the solar chromosphere with the transition region in mossy and non-mossy active-region plage. We carefully align image sequences taken with the Transition Region And Coronal Explorer (TRACE) in the ultraviolet passbands around 1550, 1600, and 1700 A and the extreme ultraviolet passbands at 171 and 195 A. We compute Fourier phase-difference spectra that are spatially averaged separately over mossy and non-mossy plage to study temporal modulations as a function of temporal frequency. The 1550 versus 171 A comparison shows zero phase difference in non-mossy plage. In mossy plage, the phase differences between all UV and EUV passbands show pronounced upward trends with increasing frequency, which abruptly changes into zero phase difference beyond 4-6 mHz. The phase difference between the 171 and 195 A sequences exhibits a shallow dip below 3 mHz and then also turns to zero phase difference beyond this value. We attribute the various similarities between the UV and EUV diagnostics that are evident in the phase-difference diagrams to the contribution of the C IV resonance lines in the 1550 and 1600 A passbands. The strong upward trend at the lower frequencies indicates the presence of upward-traveling disturbances. It points to correspondence between the lower chromosphere and the upper transition region, perhaps by slow-mode magnetosonic disturbances, or by a connection between chromospheric and coronal heating mechanisms. The transition from this upward trend to zero phase difference at higher frequencies is due to the intermittent obscuration by fibrils that occult the foot points of hot loops, which are bright in the EUV and C IV lines, in oscillatory manner.
Vasudevan, Srivathsan; Chen, George C K; Lin, Zhiping; Ng, Beng Koon
2015-05-10
Photothermal microscopy (PTM), a noninvasive pump-probe high-resolution microscopy, has been applied as a bioimaging tool in many biomedical studies. PTM utilizes a conventional phase contrast microscope to obtain highly resolved photothermal images. However, phase information cannot be extracted from these photothermal images, as they are not quantitative. Moreover, the problem of halos inherent in conventional phase contrast microscopy needs to be tackled. Hence, a digital holographic photothermal microscopy technique is proposed as a solution to obtain quantitative phase images. The proposed technique is demonstrated by extracting phase values of red blood cells from their photothermal images. These phase values can potentially be used to determine the temperature distribution of the photothermal images, which is an important study in live cell monitoring applications. PMID:25967505
Dynamic measures of regional lung air volume using phase contrast x-ray imaging
NASA Astrophysics Data System (ADS)
Kitchen, M. J.; Lewis, R. A.; Morgan, M. J.; Wallace, M. J.; Siew, M. L.; Siu, K. K. W.; Habib, A.; Fouras, A.; Yagi, N.; Uesugi, K.; Hooper, S. B.
2008-11-01
Phase contrast x-ray imaging can provide detailed images of lung morphology with sufficient spatial resolution to observe the terminal airways (alveoli). We demonstrate that quantitative functional and anatomical imaging of lung ventilation can be achieved in vivo using two-dimensional phase contrast x-ray images with high contrast and spatial resolution (<100 µm) in near real time. Changes in lung air volume as small as 25 µL were calculated from the images of term and preterm rabbit pup lungs (n = 28) using a single-image phase retrieval algorithm. Comparisons with plethysmography and computed tomography showed that the technique provided an accurate and robust method of measuring total lung air volumes. Furthermore, regional ventilation was measured by partitioning the phase contrast images, which revealed differences in aeration for different ventilation strategies.
A Method for Unwrapping Highly Wrapped Multi-echo Phase Images at Very High Field: UMPIRE
Robinson, Simon; Schödl, Horst; Trattnig, Siegfried
2014-01-01
Purpose To develop a method of unwrapping phase images from multi-echo scans that works even where there are several wraps between echoes, and which generates unwrapped phase images in addition to phase difference (PD) images. Theory The difference between the echo spacings in an acquisition with three unevenly spaced echoes (an imposed delay) can be selected such that the phase evolution in that time is in the range ?? to +? in all voxels of interest. Under this condition, an image of the difference between the phase evolutions in the two inter-echo periods, an estimate of ?B0, is free of wraps. This ?B0 estimate can be used to identify and remove receiver phase offsets and wraps in phase images. Methods The approach was tested on simulated data and high-resolution in vivo brain data acquired from six subjects at 7 Tesla. Results The method generated wrap-free phase images. It was able to remove more wraps than is possible with PD imaging and was faster and more reliable than spatial unwrapping. Conclusion Unwrapping Multi-echo Phase Images with iRregular Echo spacings (UMPIRE) is conceptually simple, fast, reliable, and requires no fitting, thresholds, or operator intervention. PMID:23901001
Lab 7: Fourier analysis and synthesis Fourier series (periodic phenomena)
Glashausser, Charles
Lab 7: Fourier analysis and synthesis · Fourier series (periodic phenomena) · Fourier transform A powerful analytic tool that has many applications.... #12;Applications of Fourier analysis Periodic t n t dt = #12;By Lucas V. Barbosa Fourier series (animation) #12;Fourier analysis and synthesis
The fractional Fourier transform and applications
NASA Technical Reports Server (NTRS)
Bailey, David H.; Swarztrauber, Paul N.
1991-01-01
This paper describes the 'fractional Fourier transform', which admits computation by an algorithm that has complexity proportional to the fast Fourier transform algorithm. Whereas the discrete Fourier transform (DFT) is based on integral roots of unity e exp -2(pi)i/n, the fractional Fourier transform is based on fractional roots of unity e exp -2(pi)i(alpha), where alpha is arbitrary. The fractional Fourier transform and the corresponding fast algorithm are useful for such applications as computing DFTs of sequences with prime lengths, computing DFTs of sparse sequences, analyzing sequences with noninteger periodicities, performing high-resolution trigonometric interpolation, detecting lines in noisy images, and detecting signals with linearly drifting frequencies. In many cases, the resulting algorithms are faster by arbitrarily large factors than conventional techniques.
Securing color image by using phase-only encoding in Fresnel domains
NASA Astrophysics Data System (ADS)
Liu, Zhengjun; Guo, Cheng; Tan, Jiubin; Liu, Wei; Wu, Jingjing; Wu, Qun; Pan, Liqiang; Liu, Shutian
2015-05-01
We propose a novel color image hiding scheme with three channels of cascaded Fresnel domain phase-only filtering. The original color image is encoded into three phase masks by using the Gerchberg-Saxton iterative phase retrieval algorithm with another predefined phase key. The individual phase masks are placed in the inputs of the Fresnel domains of the red-green-blue channels and the phase key in the public channel, during the optical retrieval. The physical parameters in the optical system will be regarded as the additional keys for security enhancement. Numerical simulation is performed to test the validity of our scheme.
A new technique for noise filtering of SAR interferometric phase images
Jong-Sen Lee; Konstantinos P. Papathanassiou; Thomas L. Ainsworth; Mitchell R. Grunes; Andreas Reigber
1998-01-01
This paper addresses the noise filtering problem for synthetic aperture radar (SAR) interferometric phase images. The phase noise is characterized by an additive noise model. The model is verified with an L-band shuttle imaging radar (SIR)-C interferogram. An adaptive filtering algorithm based on this noise model is developed. It emphasizes filtering noise adaptively according to the local noise level and
Overview of the image science objectives and mission phases
S. A. Fuselier; J. L Burch; W. S. Lewis; P. H. Reiff
2000-01-01
The Imager for Magnetopause-to-Aurora Global Exploration (IMAGE) mission uses a suite of imaging instruments to investigate the global response of the magnetosphere to changing solar wind conditions. Detailed science questions that fall under this broad objective include plasma processes that occur on the dayside, flanks, and nightside of the magnetosphere. The IMAGE orbit has been carefully designed to optimize the
Application of Bi Absorption Gratings in Grating-Based X-ray Phase Contrast Imaging
NASA Astrophysics Data System (ADS)
Lei, Yaohu; Du, Yang; Li, Ji; Huang, Jianheng; Zhao, Zhigang; Liu, Xin; Guo, Jinchuan; Niu, Hanben
2013-11-01
Among X-ray phase-contrast techniques, grating-based X-ray differential phase contrast (DPC) imaging using conventional X-ray tube sources is the most prominent one for widespread applications in the case of acquisition of high-quality absorption gratings in mass production. In this letter, we report on a new type of absorption grating made from Bi and manufactured by a micro-casting process. We tested Bi absorption gratings with our X-ray DPC imaging system and obtained high-quality phase-contrast images. Our efforts towards the practical application of X-ray DPC imaging are briefly outlined.
Image watermarking by using phase retrieval algorithm in gyrator transform domain
NASA Astrophysics Data System (ADS)
Liu, Zhengjun; Xu, Lie; Guo, Qing; Lin, Chuang; Liu, Shutian
2010-12-01
We propose an image watermarking scheme based on the phase retrieval algorithm in gyrator domain. The watermark is converted into a noise-like image by Arnold transform. The scrambled image is regarded as the amplitude of gyrator spectrum. The Gerchberg-Saxton algorithm is employed to obtain the unknown phase function in gyrator pair, in which the host image is the amplitude of input function. The phase information and the parameters of the two transforms serve as the key of watermarking algorithm. The numerical simulation has demonstrated the performance of the proposed algorithm.
A dual detector approach for X-ray differential phase contrast imaging
NASA Astrophysics Data System (ADS)
Wang, Dajiang; Wang, Zhili; Gao, Kun; Ge, Xin; Wu, Zhao; Zhu, Peiping; Wu, Ziyu
2014-02-01
Phase sensitive X-ray imaging methods can provide substantially improved contrast over conventional absorption-based techniques, and therefore new and inaccessible information. Here we propose a dual detector approach for X-ray differential phase contrast imaging, which allows a quantitative retrieval of the object's phase information by a single exposure. The analysis performed in our research shows that compared with the phase-stepping method, the dual detector approach is advantageous in fast imaging speed, reduced radiation dose and alignment errors, and avoiding any problems resulting from motion artifacts and X-ray exposure reproducibility. The approach has a direct extension to single exposure two-dimensional differential phase contrast imaging, as well as the possibility to perform three-dimensional reconstruction of the refractive index and its gradient field. We believe that this approach can find its potential in clinical applications, where imaging speed and radiation dose are critical issues.