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1

Stable signal and image reconstruction from noisy Fourier transform phase  

Microsoft Academic Search

The problem of reconstruction of finite signals and images from the noisy Fourier transform phase is addressed. The problem is pointed out to be ill-posed with respect to distortion in the phase. Regularizing reconstruction algorithms are proposed that significantly improve estimates of signals or images reconstructed from their noisy phases

Igor Lyuboshenko; Alexander Akhmetshin

1999-01-01

2

Optical Fourier techniques for medical image processing and phase contrast imaging  

NASA Astrophysics Data System (ADS)

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.

Yelleswarapu, Chandra S.; Kothapalli, Sri-Rajasekhar; Rao, D. V. G. L. N.

2008-04-01

3

Optical Fourier techniques for medical image processing and phase contrast imaging  

PubMed Central

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.

Yelleswarapu, Chandra S.; Kothapalli, Sri-Rajasekhar; Rao, D.V.G.L.N.

2008-01-01

4

Optical Fourier techniques for medical image processing and phase contrast imaging.  

PubMed

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

Yelleswarapu, Chandra S; Kothapalli, Sri-Rajasekhar; Rao, D V G L N

2008-04-01

5

Color image encoding in dual fractional Fourier-wavelet domain with random phases  

NASA Astrophysics Data System (ADS)

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.

Chen, Linfei; Zhao, Daomu

2009-09-01

6

Hierarchical encrypted image watermarking using fractional Fourier domain random phase encoding  

NASA Astrophysics Data System (ADS)

In this paper, a hierarchical encrypted image watermarking technique based on a fractional domain random phase encoding method is proposed. Multiple watermarks encrypted at multiple levels are multiplexed in the fractional Fourier domain and added into a host image. The watermarks are encrypted by the conventional fractional Fourier domain double random phase encoding scheme. The proposed method offers extra security. The invisible watermark is recovered by applying correct random phase masks along with the correct fractional orders. The metric peak signal-to-noise ratio is used to evaluate the visual quality of the watermarked image. To check the robustness of the proposed technique, the effects of image processing operations, such as cropping, mean filtering, median filtering, and noise, are also studied. For watermark authentication, the correlation value is calculated between the original and retrieved watermarks. Simulation results are presented in support of the proposed idea.

Nishchal, Naveen Kumar

2011-09-01

7

Novel image encryption/decryption based on quantum Fourier transform and double phase encoding  

NASA Astrophysics Data System (ADS)

A novel gray-level image encryption/decryption scheme is proposed, which is based on quantum Fourier transform and double random-phase encoding technique. The biggest contribution of our work lies in that it is the first time that the double random-phase encoding technique is generalized to quantum scenarios. As the encryption keys, two phase coding operations are applied in the quantum image spatial domain and the Fourier transform domain respectively. Only applying the correct keys, the original image can be retrieved successfully. Because all operations in quantum computation must be invertible, decryption is the inverse of the encryption process. A detailed theoretical analysis is given to clarify its robustness, computational complexity and advantages over its classical counterparts. It paves the way for introducing more optical information processing techniques into quantum scenarios.

Yang, Yu-Guang; Xia, Juan; Jia, Xin; Zhang, Hua

2013-07-01

8

Color image encryption based on joint fractional Fourier transform correlator and phase retrieval algorithm  

NASA Astrophysics Data System (ADS)

A novel single-channel color image encryption technique based on joint fractional Fourier transform correlator(JFRTC) and phase retrieval algorithm (PRA) is proposed. The target color image is decomposed into three red, green, blue (RGB) components. A joint image is formed and encoded into two random phase masks (RPM) iteratively. The security of the system is enhanced because of the fractional order as a new added key. The system and the operation procedure are simplified. Simulation experiments show that the algorithm converges rapidly and has great design flexibility. The decryption can be realized by digital or optical methods.

Lu, Ding; Jin, Weimin

2010-11-01

9

Double-image self-encoding and hiding based on phase-truncated Fourier transforms and phase retrieval  

NASA Astrophysics Data System (ADS)

We propose a method to encrypt two covert images into an overt image based on phase-truncated Fourier transforms and phase retrieval. In this method, the two original images are self-encoded in the manner that one of the two images is directly separated into two phase masks (PMs) and used as keys for encryption, and then multiplied by a PM which is generated by using phase retrieval algorithm. At last, the whole encryption process is completed by a Fourier transform operation. In the decryption process, the image without a separation and the two PMs used as keys for encryption are all treated as encoded data. The cryptosystem is asymmetric which means the keys for encryption are different from those for decryption. Numerical simulations are presented to show the viability and good performance of the proposed method.

Wang, Xiaogang; Zhao, Daomu

2011-09-01

10

Symmetric Phase-Only Matched Filtering of Fourier-Mellin Transforms for Image Registration and Recognition  

Microsoft Academic Search

Presents a new method to match a 2D image to a translated, rotated and scaled reference image. The approach consists of two steps: the calculation of a Fourier-Mellin invariant (FMI) descriptor for each image to be matched, and the matching of the FMI descriptors. The FMI descriptor is translation invariant, and represents rotation and scaling as translations in parameter space.

Qin-sheng Chen; Michel Defrise; Frank Deconinck

1994-01-01

11

Simultaneous nonlinear encryption of grayscale and color images based on phase-truncated fractional Fourier transform and optical superposition principle.  

PubMed

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

Wang, Xiaogang; Zhao, Daomu

2013-09-01

12

Double image encryption using phase-shifting interferometry and random mixed encoding method in fractional Fourier transform domain  

NASA Astrophysics Data System (ADS)

Based on the two-step phase-shifting interference (PSI) technique in fractional Fourier transform (FRT) domain and random mixed encoding, we present a new scheme for double image encryption. In the proposed scheme, information of each primitive image is recorded in two intensity interference patterns of FRT spectra by PSI technique, from which an encrypted image for each primitive image can be digitally derived. Random mixed encoding is then employed to divide and recombine both encrypted images into a single synthetic encrypted image. During the mixed encoding process, repositioning operations based on shift-variance of FRT are performed on the encrypted images to realize the spatial separation of decoded results in the output plane. By inverse FRT with correct fractional order, any of the primitive images can be easily retrieved directly from the synthetic encoded image with the corresponding phase encoding key. Crosstalk effect due to the overlapping of decoded images is alleviated for their spatial separation. Computer simulation and experimental results are presented to verify the validity and efficiency of our scheme.

Wang, Qu; Guo, Qing; Lei, Liang; Zhou, Jinyun

2013-08-01

13

Application of Fourier-wavelet regularized deconvolution for improving image quality of free space propagation x-ray phase contrast imaging.  

PubMed

New x-ray phase contrast imaging techniques without using synchrotron radiation confront a common problem from the negative effects of finite source size and limited spatial resolution. These negative effects swamp the fine phase contrast fringes and make them almost undetectable. In order to alleviate this problem, deconvolution procedures should be applied to the blurred x-ray phase contrast images. In this study, three different deconvolution techniques, including Wiener filtering, Tikhonov regularization and Fourier-wavelet regularized deconvolution (ForWaRD), were applied to the simulated and experimental free space propagation x-ray phase contrast images of simple geometric phantoms. These algorithms were evaluated in terms of phase contrast improvement and signal-to-noise ratio. The results demonstrate that the ForWaRD algorithm is most appropriate for phase contrast image restoration among above-mentioned methods; it can effectively restore the lost information of phase contrast fringes while reduce the amplified noise during Fourier regularization. PMID:23093444

Zhou, Zhongxing; Gao, Feng; Zhao, Huijuan; Zhang, Lixin

2012-10-24

14

Fourier phase microscopy with white light  

PubMed Central

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.

Bhaduri, Basanta; Tangella, Krishnarao; Popescu, Gabriel

2013-01-01

15

Laser Field Imaging Through Fourier Transform Heterodyne  

SciTech Connect

The authors present a detection process capable of directly imaging the transverse amplitude, phase, and Doppler shift of coherent electromagnetic fields. Based on coherent detection principles governing conventional heterodyned RADAR/LADAR systems, Fourier Transform Heterodyne incorporates transverse spatial encoding of the reference local oscillator for image capture. Appropriate selection of spatial encoding functions allows image retrieval by way of classic Fourier manipulations. Of practical interest: (1) imaging may be accomplished with a single element detector/sensor requiring no additional scanning or moving components, (2) as detection is governed by heterodyne principles, near quantum limited performance is achievable, (3) a wide variety of appropriate spatial encoding functions exist that may be adaptively configured in real-time for applications requiring optimal detection, and (4) the concept is general with the applicable electromagnetic spectrum encompassing the RF through optical.

Cooke, B.J.; Laubscher, B.E.; Olivas, N.L.; Galbraith, A.E.; Strauss, C.E.; Grubler, A.C.

1999-04-05

16

Ghost imaging in Fourier space  

NASA Astrophysics Data System (ADS)

In experimentation we first find that a ghost diffraction image exists even when the coherent length on the object plane is larger than the character size of the object, and we explain the phenomenon in Fourier space. The analysis indicates that the resolution of the far-field diffraction image is determined by the coherent length on the back-focus plane, and the distribution of the wave vector of the illumination on the object determines the range of information of a pixel detector collecting in the signal arm.

Liu, Honglin; Cheng, Jing; Han, Shensheng

2007-11-01

17

Fourier phase microscopy with white light.  

PubMed

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

Bhaduri, Basanta; Tangella, Krishnarao; Popescu, Gabriel

2013-07-25

18

Medical image processing with optical Fourier techniques  

Microsoft Academic Search

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

Pengfei Wu

2003-01-01

19

Fourier phase microscopy for investigation of biological structures and dynamics  

Microsoft Academic Search

By use of the Fourier decomposition of a low-coherence optical image field into two spatial components that can be controllably shifted in phase with respect to each other, a new high-transverse-resolution quantitative-phase microscope has been developed. The technique transforms a typical optical microscope into a quantitative-phase microscope, with high accuracy and a path-length sensitivity of lambda\\/5500, which is stable over

Gabriel Popescu; Lauren P. Deflores; Joshua C. Vaughan; Kamran Badizadegan; Hidenao Iwai; Ramachandra R. Dasari; Michael S. Feld

2004-01-01

20

Fourier transform infrared imaging of bone.  

PubMed

Fourier transform infrared imaging (FTIRI) is a technique that can be used to analyze the material properties of bone using tissue sections. In this chapter I describe the basic principles of FTIR and the methods for capturing and analyzing FTIR images in bone sections. PMID:22130948

Paschalis, Eleftherios P

2012-01-01

21

Livermore Imaging Fourier Transform Infrared Spectrometer (LIFTIRS)  

SciTech Connect

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.

Carter, M.R.; Bennett, C.L.; Fields, D.J.; Lee, F.D.

1995-05-10

22

Fourier Transform and Reflective Imaging Pyrometry  

SciTech Connect

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.

Stevens, G. D.

2011-07-01

23

Image processing and the Arithmetic Fourier Transform  

SciTech Connect

A new Fourier technique, the Arithmetic Fourier Transform (AFT) was recently developed for signal processing. This approach is based on the number-theoretic method of Mobius inversion. The AFT needs only additions except for a small amount of multiplications by prescribed scale factors. This new algorithm is also well suited to parallel processing. And there is no accumulation of rounding errors in the AFT algorithm. In this reprint, the AFT is used to compute the discrete cosine transform and is also extended to 2-D cases for image processing. A 2-D Mobius inversion formula is proved. It is then applied to the computation of Fourier coefficients of a periodic 2-D function. It is shown that the output of an array of delay-line (or transversal) filters is the Mobius transform of the input harmonic terms. The 2-D Fourier coefficients can therefore be obtained through Mobius inversion of the output of the filter array.

Tufts, D.W.; Fan, Z.; Cao, Z.

1989-01-01

24

Fourier implementation of poisson image editing  

Microsoft Academic Search

Poisson editing, introduced in 2003, is becoming a technique with major applications in many different domains of image processing and computer graphics. This letter presents an exact and fast Fourier implementation of the Poisson editing equation proposed in (Pérez et al., 2003). The proposed algorithm can handle well all Poisson editing methods that are currently implemented with finite differences and

J.-M. Morel; A. B. Petro; C. Sbert

25

Novel fringe scanning/Fourier transform method of synthetic imaging  

SciTech Connect

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.

Crawford, T.M.; Albano, R.K.

1993-08-01

26

Near IR electro-optic imaging Fourier transform spectrometer  

NASA Astrophysics Data System (ADS)

JPL and BNS Inc. are jointly developing a compact, low mass, Electro-Optic Imaging Fourier Transform Spectrometer (E-O IFTS) for hyperspectral imaging applications [6]. The spectral region of this spectrometer is in the near IR spectral band of 1 - 2.5 ?m (1000 - 4000 cm-1) to allow high-resolution, high-speed hyperspectral imaging applications. The specific applications for NASA"s missions will focus on the measurement of a large number of different atmospheric gases simultaneously in the same airmass. Due to the use of a combination of birefringent phase retarders (YVO4) and multiple achromatic phase switches to achieve phase delay, this spectrometer is capable of hyperspectral measurements similar to that of the conventional Fourier transform spectrometer but without any moving parts. In this paper, the principle of operations, system architecture and recent technical progress will be presented.

Chao, Tien-Hsin; Zhou, Hanying; Xia, Xiaowei; Serati, Steven

2005-03-01

27

Hyperspectral imaging using electro-optic Fourier transform spectrometer  

NASA Astrophysics Data System (ADS)

JPL and BNS Inc. are jointly developing a compact, low mass, Electro-Optic Imaging Fourier Transform Spectrometer (E-O IFTS) for hyperspectral imaging applications. The spectral region of this spectrometer will be 1 - 2.5 ?m (1000 - 4000 cm-1) to allow high-resolution, high-speed hyperspectral imaging applications. The specific applications for NASA's missions will focus on the measurement of a large number of different atmospheric gases simultaneously in the same airmass. Due to the use of a combination of birefringent phase retarders and multiple achromatic phase switches to achieve phase delay, this spectrometer is capable of hyperspectral measurements similar to that of the conventional Fourier transform spectrometer but without any moving parts. In this paper, the principle of operations, system architecture and recent experimental progress will be presented.

Chao, Tien-Hsin; Zhou, Hanying; Xia, Xiaowei; Serati, Steven A.

2004-04-01

28

Image registration for Fizeau Fourier transform imaging spectroscopy  

Microsoft Academic Search

Fourier transform imaging spectroscopy (FTIS) can be performed with a Fizeau imaging interferometer by recording a series of images with various optical path differences (OPDs) between subapertures of the optical system and postprocessing. The quality of the spectral data is affected by misregistration of the raw image measurements. A Fizeau FTIS system possesses unique degrees of freedom that can be

Samuel T. Thurman; James R. Fienup

2006-01-01

29

Image registration for Fizeau Fourier transform imaging spectroscopy  

Microsoft Academic Search

Fourier transform imaging spectroscopy (FTIS) can be performed with a Fizeau imaging interferometer by recording a series of images with various optical path differences (OPDs) between subapertures of the optical system and post- processing. The quality of the spectral data is affected by misregistration of the raw image measurements. A Fizeau FTIS system possesses unique degrees of freedom that can

Samuel T. Thurman; James R. Fienup

30

Imaging vibration of the cochlear partition of an excised guinea pig cochlea using phase-sensitive Fourier domain optical coherence tomography  

Microsoft Academic Search

Studying the sound stimulated vibrations of various membranes that form the complex structure of the organ of Corti in the cochlea of the inner ear is essential for understanding how the travelling sound wave of the basilar membrane couples its energy to the organ structures. In this paper we report the feasibility of using phase-sensitive Fourier domain optical coherence tomography

Niloy Choudhury; Yaguang Zeng; Anders Fridberger; Fangyi Chen; Dingjun Zha; Alfred L. Nuttall; Ruikang K. Wang

2011-01-01

31

Mosaic imaging Fourier transform spectrometer applications  

Microsoft Academic Search

A high-speed passive FTIR imaging spectrometer has been developed and tested in airborne flight tests on both fixed wing and helicopter platforms. This sensor was developed and flown from 2000 to 2005 in conjunction with various organizations, and is known as the Turbo FT. The Turbo FT is a laser-less rotary high speed Fourier Transform Infra-Red (FTIR) spectrometer capable of

Winthrop Wadsworth; Jens Peter Dybwad; Drew Stone

2005-01-01

32

Enhanced Optical Image Verification Based on Joint Transform Correlator Adopting Fourier Hologram  

Microsoft Academic Search

In this paper two new architectures for optical image verification are proposed. Both architectures are based on conventional joint transform correlators (JTCs) adopting a Fourier hologram and can significantly improve the recovered image quality. First, an input phase-only function is Fourier transformed and then interferes with a reference wave that is diffracted from a plane wave incident on another random

Hsuan T. CHANGand; Ching T. T. Chen

2004-01-01

33

Fourier transform digital holographic adaptive optics imaging system  

PubMed Central

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.

Liu, Changgeng; Yu, Xiao; Kim, Myung K.

2013-01-01

34

Target Image Enhancement in Radar Imaging Using Fractional Fourier Transform  

NASA Astrophysics Data System (ADS)

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.

El-Mashed, M. G.; Dessouky, M. I.; El-Kordy, M.; Zahran, O.; Abd El-Samie, F. E.

2012-03-01

35

Optical imaging process based on two-dimensional Fourier transform for synthetic aperture imaging ladar  

NASA Astrophysics Data System (ADS)

The synthetic aperture imaging ladar (SAIL) systems typically generate large amounts of data difficult to compress with digital method. This paper presents an optical SAIL processor based on compensation of quadratic phase of echo in azimuth direction and two dimensional Fourier transform. The optical processor mainly consists of one phase-only liquid crystal spatial modulator(LCSLM) to load the phase data of target echo and one cylindrical lens to compensate the quadratic phase and one spherical lens to fulfill the task of two dimensional Fourier transform. We show the imaging processing result of practical target echo obtained by a synthetic aperture imaging ladar demonstrator. The optical processor is compact and lightweight and could provide inherent parallel and the speed-of-light computing capability, it has a promising application future especially in onboard and satellite borne SAIL systems.

Sun, Zhiwei; Zhi, Ya'nan; Liu, Liren; Sun, Jianfeng; Zhou, Yu; Hou, Peipei

2013-09-01

36

Enhanced Optical Image Verification Based on Joint Transform Correlator Adopting Fourier Hologram  

NASA Astrophysics Data System (ADS)

In this paper two new architectures for optical image verification are proposed. Both architectures are based on conventional joint transform correlators (JTCs) adopting a Fourier hologram and can significantly improve the recovered image quality. First, an input phase-only function is Fourier transformed and then interferes with a reference wave that is diffracted from a plane wave incident on another random phase mask. Second, two phase-only functions are placed at the two input sides of a beamsplitter such that the interference pattern of their Fourier transforms can be detected. To obtain a predefined target image in the output plane, one of the input phase functions is iteratively retrieved by the use of the projection onto constraint sets algorithm. Simulation results show that the less mean squared error and better image quality are obtained for both the binary and grayscale images.

Chang, Hsuan T.; Chen, Ching T. T.

2004-05-01

37

Mosaic imaging Fourier transform spectrometer applications  

NASA Astrophysics Data System (ADS)

A high-speed passive FTIR imaging spectrometer has been developed and tested in airborne flight tests on both fixed wing and helicopter platforms. This sensor was developed and flown from 2000 to 2005 in conjunction with various organizations, and is known as the Turbo FT. The Turbo FT is a laser-less rotary high speed Fourier Transform Infra-Red (FTIR) spectrometer capable of very high speed, spectral resolution to 1 cm-1, and operation in rugged environments. For these tests, the sensor was run at 8 cm-1 resolution and 50-100 scans per second with either a single element or a 2x8 element LWIR detector. An on-board auto-calibrating blackbody accessory was developed and automated chemical detection software was developed. These features allow in-flight calibration, facilitated detection of target gas clouds, and reported detections to an on-board targeting computer. This paper will discuss the system specifications, sensor performance, and field results from various experiments. Current work on development of an 8x8 pixel Turbo FT system will also be presented.

Wadsworth, Winthrop; Dybwad, Jens Peter; Stone, Drew

2005-06-01

38

Fourier phase domain steganography: phase bin encoding via interpolation  

NASA Astrophysics Data System (ADS)

In recent years there has been an increased interest in audio steganography and watermarking. This is due primarily to two reasons. First, an acute need to improve our national security capabilities in light of terrorist and criminal activity has driven new ideas and experimentation. Secondly, the explosive proliferation of digital media has forced the music industry to rethink how they will protect their intellectual property. Various techniques have been implemented but the phase domain remains a fertile ground for improvement due to the relative robustness to many types of distortion and immunity to the Human Auditory System. A new method for embedding data in the phase domain of the Discrete Fourier Transform of an audio signal is proposed. Focus is given to robustness and low perceptibility, while maintaining a relatively high capacity rate of up to 172 bits/s.

Rivas, Edward

2007-05-01

39

Dealiased spectral images from aliased Fizeau Fourier transform spectroscopy measurements  

Microsoft Academic Search

Fizeau Fourier transform imaging spectroscopy (FTIS) is a technique for collecting both spatial and spectral information about an object with a Fizeau imaging interferometer and postprocessing. The technique possesses unconventional imaging properties due to the fact that the system transfer functions, including the imaging and spectral postprocessing operations, are given by cross correlations between subapertures of the optical system, in

Samuel T. Thurman; James R. Fienup

2007-01-01

40

Calibration of the Geostationary Imaging Fourier Transform Spectrometer (GIFTS)  

NASA Astrophysics Data System (ADS)

The NASA New Millennium Program's Geostationary Imaging Fourier Transform Spectrometer (GIFTS) requires highly accurate radiometric and spectral calibration in order to carry out its mission to provide water vapor, wind, temperature, and trace gas profiling from geostationary orbit. A calibration concept has bene developed for the GIFTS Phase A instrument design. The in-flight calibration is performed using views of two on-board blackbody sources along with cold space. A radiometric calibration uncertainty analysis has been developed and used to show that the expected performance for GIFTS exceeds its top level requirement to measure brightness temperature to better than 1 K. For the Phase A GIFTS design, the spectral calibration is established by the highly stable diode laser used as the reference for interferogram sampling, and verified with comparisons to atmospheric calculations.

Best, Fred A.; Revercomb, Henry E.; Bingham, Gail E.; Knuteson, Robert O.; Tobin, David C.; LaPorte, Daniel D.; Smith, William L.

2001-02-01

41

FourierTransform Method of Phase-Shift Determination  

Microsoft Academic Search

A new phase-shifting interferometry analysis technique has been developed to overcome the errors introduced by nonlinear, irregular, or unknown phase-step increments. In the presence of a spatial carrier frequency, by observation of the phase of the first-order maximum in the Fourier domain, the global phase-step positions can be measured, phase-shifting elements can be calibrated, and the accuracy of phase-shifting analysis

Kenneth A. Goldberg; Jeffrey Bokor

2001-01-01

42

Fourier-transform ghost imaging with pure far-field correlated thermal light  

NASA Astrophysics Data System (ADS)

Pure far-field correlated thermal light beams are created with phase grating, and Fourier-transform ghost imaging depending only on the far-field correlation is demonstrated experimentally. Theoretical analysis and the results of experimental investigation of this pure far-field correlated thermal light are presented. Applications which may be exploited with this imaging scheme are discussed.

Liu, Honglin; Shen, Xia; Zhu, Da-Ming; Han, Shensheng

2007-11-01

43

Fourier domain OCT imaging of American cockroach nervous system  

NASA Astrophysics Data System (ADS)

In this pilot study we demonstrate results of structural Fourier domain OCT imaging of the nervous system of Periplaneta americana L. (American cockroach). The purpose of this research is to develop an OCT apparatus enabling structural imaging of insect neural system. Secondary purpose of the presented research is to develop methods of the sample preparation and handling during the OCT imaging experiments. We have performed imaging in the abdominal nerve cord excised from the American cockroach. For this purpose we have developed a Fourier domain / spectral OCT system operating at 820 nm wavelength range.

Wyszkowska, Joanna; Gorczynska, Iwona; Ruminski, Daniel; Karnowski, Karol; Kowalczyk, Andrzej; Stankiewicz, Maria; Wojtkowski, Maciej

2012-02-01

44

Fourier transform imaging spectrometry using Sagnac interferometer  

NASA Astrophysics Data System (ADS)

The technology of image plane interferometric imaging spectrometer has been the research hotpot because of its high throughput, which brings the system a high Signal to Noise Ratio (SNR) and higher spectral resolution compared to other kinds of imaging spectrometer. In order to obtain the spectral images of scene at different distance, a system of image plane interferometric imaging spectrometer based on re-imaging is presented, which consists of a front-end objective lens, a collimator, a Sagnac lateral shearing interferometer, a back-end imaging lens and a detector. A separated front-end objective lens with zoom lens or fixed focus lens is adopted to image the scene on the first imaging plane. The light from the points in the first imaging plane is then collimated to parallel light by the collimator. Then the parallel light is sheared into two beams of coherent light by the Sagnac lateral shearing interferometer. The imaging lens converge the two beams on the detector. Intensity of the converged point is detected by the detector. The imaging system and resolution of spectrum are analyzed. Besides, two push broom modes are discussed. Experimental device is set up to detect the targets of near field indoor and far field outdoor. Twenty-six reconstructed spectral images are obtained from 460nm to 620nm. The experimental results show that the proposed imaging method is effectively applied in hyperspectral imaging of targets at different distances.

Li, Jianxin; Zhou, Wei; Meng, Xin; Liu, Defang; Zhu, Rihong

2013-08-01

45

Imaging Fourier transform spectroscopy with multi-aperture telescopes  

Microsoft Academic Search

Fourier spectroscopy can be performed with multi-aperture telescopes by adjusting the optical path difference between apertures. Expressions are given for the measured intensity and the recovered spectrum for a general multi-aperture system. The transfer function of a multi-aperture spectrometer is strikingly different than for a conventional Michelson imaging spectrometer. ©2003 Optical Society of America OCIS codes: (300.6300) Spectroscopy, Fourier transforms;

Samuel T. Thurman; James R. Fienup; R. L. Kendrick

46

Fractional Fourier transform in temporal ghost imaging with classical light  

SciTech Connect

We investigate temporal, second-order classical ghost imaging with long, incoherent, scalar plane-wave pulses. We prove that in rather general conditions, the intensity correlation function at the output of the setup is given by the fractional Fourier transform of the temporal object. In special cases, the correlation function is shown to reduce to the ordinary Fourier transform and the temporal image of the object. Effects influencing the visibility and the resolution are considered. This work extends certain known results on spatial ghost imaging into the time domain and could find applications in temporal tomography of pulses.

Setaelae, Tero [Department of Applied Physics, Aalto University, P.O. Box 13500, FI-00076 Aalto (Finland); Shirai, Tomohiro [Photonics Research Institute, National Institute of Advanced Industrial Science and Technology, 1-2-1 Namiki, Tsukuba 305-8564 (Japan); Friberg, Ari T. [Department of Applied Physics, Aalto University, P.O. Box 13500, FI-00076 Aalto (Finland); Department of Physics and Mathematics, University of Eastern Finland, P.O. Box 111, FI-80101 Joensuu (Finland)

2010-10-15

47

Geometrically robust image watermarking based on Jacobi-Fourier moments  

NASA Astrophysics Data System (ADS)

Rotation, scaling and translation (RST) attacks can desynchronize the watermark detection so that many watermark systems failed. A geometrically robust image watermarking strategy based on Jacobi-Fourier moments (JFMs) is proposed. The Jacobi moments of the original image are first extracted as original moments; then the watermark image is embedded into the global or local area of the original image, and the Jacobi moments of the area are extracted. When the watermarked image is not attacked, the watermark can be retrieved by using the margin of the original moments and the moments of the embedded area. When it is attacked, the watermark can also be got in that way, and the original moments need to be transformed. It can be concluded that Jacobi-Fourier moments perform better than Zernike moments (ZMs) for small images. Meanwhile, the watermark is also robust to scaling and rotation as well as regular attacks such as added noises.

Dong, Jia-Li; Yin, Guo-Rui; Ping, Zi-Liang

2009-09-01

48

Medical Image Provessing using Transient Fourier Holography in Bacteriorhodopsin Films  

NASA Astrophysics Data System (ADS)

A real-time optical Fourier image processing system is demonstrated for early detection of microcalcifications in screen film as well as digital mammograms. The principle is based on recording and reconstructing the transient photoisomerizative grating formed in the bR film. At first Fourier hologram is recorded by spatially overlapping the Fourier transformed object beam with the reference beam in the bR film. Then the object beam is blocked and the reference beam performs the reconstruction of the recorded Fourier hologram. The optimum of diffraction efficiency occurs when object beam intensity is matched to the reference beam intensity. We exploit this technique to process mammograms in real-time for identification of microcalcifications buried in the soft tissue for early detection of breast cancer. A novel feature of the technique is the ability to transient display of selected spatial frequencies in the reconstructing process which enables the radiologists to study the features of interest in time scale.

Kothapalli, Sri-Rajasekhar; Wu, Pengfei; Yelleswarapu, Chandra; Devulapalli, Rao

2005-03-01

49

High Fidelity Magnetic Resonance Imaging by Frequency Sweep Encoding and Fourier Decoding  

PubMed Central

Using a RF pulse with linear frequency sweep and a simultaneous encoding gradient, magnetization is sequentially excited accompanied by a quadratic phase profile. This quadratic dependence of magnetization phase on position dephases magnetization away from its vertices, allowing direct spatial encoding and image formation in the time domain. In this work we extend this spatial encoding scheme to include nonlinear frequency sweep and show that Fourier decoding or least square fitting in combination with frequency sweep spatial encoding schemes can generate high fidelity images. Application to in vivo multiscan susceptibility-weighted imaging is demonstrated. Our results show that Fourier-decoded, spatially encoded images compare favorably with conventional high resolution images while preserving the unique features of sequential excitation.

Shen, Jun; Xiang, Yun

2010-01-01

50

Using UNFOLD to remove artifacts in parallel imaging and in partial-Fourier imaging.  

PubMed

In dynamic MRI, it is often difficult to achieve the acquisition speed required to resolve or freeze the temporal variations of the imaged object. Several MRI methods aim at speeding up the image acquisition process. Through assumptions and/or prior knowledge, these dynamic MRI methods allow part of the needed data to be calculated instead of acquired. For example, partial-Fourier imaging assumes that phase varies smoothly within the object, and parallel imaging (e.g., simultaneous acquisition of spatial harmonics (SMASH) and sensitivity encoding (SENSE)) uses prior knowledge about receiver-coil sensitivity. While these methods accelerate acquisition, they can introduce artifacts or amplify noise in doing so. The present work aims at accelerating image acquisition significantly, while introducing almost no artifacts or noise amplification. It is shown here that new, extra information is gained if dynamic MRI methods are modified so that the sampling function changes in specific ways from time-frame to time-frame. In other words, the set of k-space locations that are acquired (instead of calculated) changes with time. The present temporal strategy, based on the UNaliasing by Fourier-encoding the Overlaps in the temporaL Dimension (UNFOLD) method, can be incorporated into common dynamic MRI methods. Results with partial-Fourier, SMASH, and SENSE imaging are presented here, where UNFOLD's contribution is to very significantly reduce the artifact and/or amplified noise content. Used in this way, UNFOLD contributes indirectly, rather than directly to the improvement in image acquisition speed, as it allows companion methods to operate properly at greater acceleration settings than would otherwise be feasible. PMID:12210914

Madore, Bruno

2002-09-01

51

Color image encryption and decryption for twin images in fractional Fourier domain  

NASA Astrophysics Data System (ADS)

We propose a method for the encryption of twin color images using fractional Fourier transform (FRT). The color images to be encrypted are converted into the indexed image formats before being processed through twin image encryption algorithm based on the FRT. The proposed algorithm uses one random code in the image domain and one random phase code in the FRT domain to perform double image encryption. The conversion of both the input RGB images into their indexed formats facilitates single-channel processing for each image, and is more compact and robust as compared to multichannel techniques. Different fractional orders, the random masks in image- and FRT domain are the keys to enhance the security of the proposed system. The algorithms to implement the proposed encryption and decryption schemes are discussed, and results of digital simulation are presented. We examine sensitivity of the proposed scheme against the use of unauthorized keys (e.g. incorrect fractional orders, incorrect random phase mask etc.). Robustness of the method against occlusion and noise has also been discussed.

Joshi, Madhusudan; Chandrashakher; Singh, Kehar

2008-12-01

52

Nanoscale Fourier-Transform Magnetic Resonance Imaging  

NASA Astrophysics Data System (ADS)

We report a method for nanometer-scale pulsed nuclear magnetic resonance imaging and spectroscopy. Periodic radio-frequency pulses are used to create temporal correlations in the statistical polarization of a solid organic sample. The spin density is spatially encoded by applying a series of intense magnetic field gradient pulses generated by focusing electric current through a nanometer-scale metal constriction. We demonstrate this technique using a silicon nanowire mechanical oscillator as a magnetic resonance sensor to image H1 spins in a polystyrene sample. We obtain a two-dimensional projection of the sample proton density with approximately 10-nm resolution.

Nichol, John M.; Naibert, Tyler R.; Hemesath, Eric R.; Lauhon, Lincoln J.; Budakian, Raffi

2013-07-01

53

Scanning plasmonic microscopy by image reconstruction from the Fourier space.  

PubMed

We demonstrate a simple scheme for high-resolution imaging of nanoplasmonic structures that basically removes most of the resolution limiting allowed light usually transmitted to the far field. This is achieved by implementing a Fourier lens in a near-field scanning optical microscope (NSOM) operating in the leakage-radiation microscopy (LRM) mode. The method consists of reconstructing optical images solely from the plasmonic 'forbidden' light collected in the Fourier space. It is demonstrated by using a point-like nanodiamond-based tip that illuminates a thin gold film patterned with a sub-wavelength annular slit. The reconstructed image of the slit shows a spatial resolution enhanced by a factor ~/= 4 compared to NSOM images acquired directly in the real space. PMID:23263132

Mollet, Oriane; Huant, Serge; Drezet, Aurélien

2012-12-17

54

Multi-aperture Fourier transform imaging spectroscopy: theory and imaging properties  

Microsoft Academic Search

Fourier transform imaging spectroscopy (FTIS) can be performed with a multi-aperture optical system by making a series of intensity measurements, while introducing optical path differences (OPD's) between various subapertures, and recovering spectral data by the standard Fourier post-processing technique. The imaging properties for multi-aperture FTIS are investigated by examining the imaging transfer functions for the recovered spectral images. For systems

Samuel T. Thurman; James R. Fienup

2005-01-01

55

Astronomical imaging Fourier spectroscopy at far-infrared wavelengths  

NASA Astrophysics Data System (ADS)

The principles and practice of astronomical imaging Fourier transform spectroscopy (FTS) at far-infrared wavelengths are described. The Machâ??Zehnder (MZ) interferometer design has been widely adopted for current and future imaging FTS instruments; we compare this design with two other common interferometer formats. Examples of three instruments based on the MZ design are presented. The techniques for retrieving astrophysical parameters from the measured spectra are discussed using calibration data obtained with the Herschelâ??SPIRE instrument. The paper concludes with an example of imaging spectroscopy obtained with the SPIRE FTS instrument.

Naylor, David A.; Gom, Brad G.; van der Wiel, Matthijs H. D.; Makiwa, Gibion

2013-11-01

56

The Fourier analysis of magnetic force microscopy imaging  

NASA Astrophysics Data System (ADS)

The stray field near the magnetic thin film sample surface has been calculated from the measured signal of the magnetic force microscopy (MFM) image by the method of discrete Fourier transform. It is found that the domain structure of the film cannot uniquely be determined by the MFM image because the MFM image just reflects the magnetic charges distribution at sample surface. In fact, the magnetic charges at sample surface have two sources: magnetic domain or domain wall. For the same MFM image, the different sources of the magnetic charges will result in very different domain structure. A proper way to determine the domain structure is to know the source of the magnetic charges and use the different components of the stray field to redraw the image.

Wu, Dongping; Lou, Yuanfu; Zheng, Fu; Liu, Liwang; Wei, Dan; Wei, Fulin

2012-09-01

57

Binary-phase Fourier gratings for nonuniform array generation  

NASA Astrophysics Data System (ADS)

This effort describes a design method used to develop a binary-phase Fourier grating that generates an incoherent array of output source points with nonuniform user-defined intensities, symmetric about the zeroth order. Like the Dammann fanout grating approach, the binary-phase Fourier grating uses only two phase levels in its grating surface profile to generate the output array. Unlike the Dammann fanout grating approach, this method provides for the generation of nonuniform, user-defined intensities within the final fanout pattern. The process employs both simulated annealing and nonlinear optimization algorithms to locate solutions to the specified grating design problem. Because the desired grating output is incoherent, each source point of the grating response is assessed in terms of intensity, from which an overall efficiency is calculated. Efficiencies are calculated for each solution and are used to evaluate the relative value of each solution. A final design solution that produces an incoherent, symmetric, user-defined nine spot array is presented.

Keys, Andrew S.; Crow, Robert W.; Ashley, Paul R.

2003-11-01

58

Fourier transform infrared phase shift cavity ring down spectrometer  

NASA Astrophysics Data System (ADS)

We report on our current status towards the development of a prototype Fourier transform infrared phase shift cavity ring down spectrometer (FTIR-PS-CRDS) system under a U.S. EPA SBIR contract. Our system uses the inherent wavelength-dependent modulation imposed by the FTIR on a broadband thermal source for the phase shift measurement. This spectrally-dependent phase shift is proportional to the spectrally-dependent ring down time, which is proportional to the losses of the cavity including those due to molecular absorption. Our approach is a broadband and spectral range enhancement to conventional CRDS which is typically done in the near IR at a single wavelength; at the same time our approach is a sensitivity enhancement to traditional FTIR owing to the long effective path of the resonant cavity. In this paper we present a summary of the theory including performance projections and the design details of the prototype FTIR-PS-CRDS system.

Schundler, Elizabeth; Mansur, David J.; Vaillancourt, Robert; Benedict-Gill, Ryan; Newbry, Scott P.; Engel, James R.; Rentz Dupuis, Julia

2013-05-01

59

Fourier domain optical tool normalization for quantitative parametric image reconstruction.  

PubMed

There has been much recent work in developing advanced optical metrology methods that use imaging optics for critical dimension measurements and defect detection. Sensitivity to nanometer-scale changes has been observed when measuring critical dimensions of subwavelength 20 nm features or when imaging defects below 15 nm using angle-resolved and focus-resolved optical data. However, these methods inherently involve complex imaging optics and analysis of complicated three-dimensional electromagnetic fields. This paper develops a new approach to enable the rigorous analysis of three-dimensional, through-focus, or angle-resolved optical images. We use rigorous electromagnetic simulation with enhanced Fourier optical techniques, an approach to optical tool normalization, and statistical methods to evaluate sensitivities and uncertainties in the measurement of subwavelength three-dimensional structures. PMID:24085127

Qin, Jing; Silver, Richard M; Barnes, Bryan M; Zhou, Hui; Goasmat, Francois

2013-09-10

60

An image hiding method based on cascaded iterative Fourier transform and public-key encryption algorithm  

NASA Astrophysics Data System (ADS)

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.

Zhang, B.; Sang, Jun; Alam, Mohammad S.

2013-03-01

61

Fourier transform imaging spectroscopy with a multiple-aperture telescope: band-by-band image reconstruction  

Microsoft Academic Search

Fourier transform imaging spectroscopy can be performed with a segmented-aperture telescope or a multiple-telescope array using the subaperture piston control mechanisms. Spectrum recovery from intensity measurements is analyzed for a general aperture configuration. The spatial transfer functions of the recovered spectral images are shown to vanish necessarily at the DC spatial frequency. This poses an interesting image reconstruction problem as

Samuel T. Thurman; James R. Fienup

2004-01-01

62

Medical image processing using transient Fourier holography in bacteriorhodopsin films  

NASA Astrophysics Data System (ADS)

Real time image processing is demonstrated by recording and reconstructing the transient photoisomerizative grating formed in the bR film using Fourier holography. Desired spatial frequencies including both high and low band in the object beam are reconstructed by controlling the reference beam intensity. The results are in agreement with a theoretical model based on photoisomerization grating. We exploit this technique to process mammograms in real-time for identification of microcalcifications buried in the soft tissue for early detection of breast cancer. A feature of the technique is the ability to transient display of selected spatial frequencies in the reconstructing process which enables the radiologists to study the features of interest.

Kothapalli, Sri-Rajasekhar; Wu, Pengfei; Yelleswarapu, Chandra S.; Rao, D. V. G. L. N.

2004-12-01

63

A Local Algorithm for the Computation of Image Velocity via Constructive Interference of Global Fourier Components  

Microsoft Academic Search

A novel Fourier-based technique for local motion detection from image sequences is proposed. In this method, the instantaneous\\u000a velocities of local image points are inferred directly from the global 3D Fourier components of the image sequence. This is\\u000a done by selecting those velocities for which the superposition of the corresponding Fourier gratings leads to constructive\\u000a interference at the image point.

Babette Dellen; Florentin Wörgötter

2011-01-01

64

Using a piezoelectric fiber stretcher to remove the depth ambiguity in optical Fourier domain imaging  

NASA Astrophysics Data System (ADS)

This paper reports the study of an Optical Fourier Domain Imaging (OFDI) setup for optical coherence tomography. One of the main drawbacks of OFDI is its inability to differentiate positive and negative depths. Some setups have already been proposed to remove this depth ambiguity by introducing a modulation by means of electro-optic or acousto-optic modulators. In our setup, we implement a piezoelectric fiber stretcher to generate a periodic phase shift between successive A-scans, thus introducing a transverse modulation. The depth ambiguity is then resolved by performing a Fourier treatment in the transverse direction before processing the data in the axial direction. It is similar to the B-M mode scanning already proposed for Spectral-Domain OCT1 but with a more efficient experimental setup. We discuss the advantages and the drawbacks of our technique compared to the technique based on acousto-optics modulators by comparing images of an onion obtained with both techniques.

Vergnole, Sébastien; Lamouche, Guy; Dufour, Marc; Gauthier, Bruno

2007-08-01

65

Fractional Fourier transform based image multiplexing and encryption technique for four-color images using input images as keys  

NASA Astrophysics Data System (ADS)

A digital technique for multiplexing and encryption of four RGB images has been proposed using the fractional Fourier transform (FRT). The four input RGB images are first converted into their indexed image formats and subsequently multiplexed into a single image through elementary mathematical steps prior to the encryption. The encryption algorithm uses two random phase masks in the input- and the FRT domain, respectively. These random phase masks are especially designed using the input images. As the encryption is carried out through a single channel, the technique is more compact and faster as compared to the multichannel techniques. Different fractional orders, the random masks in input-, and FRT domain are the keys for decryption as well as de-multiplexing. The algorithms to implement the proposed multiplexing-, and encryption scheme are discussed, and results of digital simulation are presented. Simulation results show that the technique is free from cross-talk. The performance of the proposed technique has also been analyzed against occlusion, noise, and attacks using partial windows of the correct random phase keys. The robustness of the technique against known-, and chosen plain-text attacks has also been explained.

Joshi, Madhusudan; Shakher, Chandra; Singh, Kehar

2010-06-01

66

Universal and efficient compressed sensing by spread spectrum and application to realistic Fourier imaging techniques  

NASA Astrophysics Data System (ADS)

We advocate a compressed sensing strategy that consists of multiplying the signal of interest by a wide bandwidth modulation before projection onto randomly selected vectors of an orthonormal basis. First, in a digital setting with random modulation, considering a whole class of sensing bases including the Fourier basis, we prove that the technique is universal in the sense that the required number of measurements for accurate recovery is optimal and independent of the sparsity basis. This universality stems from a drastic decrease of coherence between the sparsity and the sensing bases, which for a Fourier sensing basis relates to a spread of the original signal spectrum by the modulation (hence the name "spread spectrum"). The approach is also efficient as sensing matrices with fast matrix multiplication algorithms can be used, in particular in the case of Fourier measurements. Second, these results are confirmed by a numerical analysis of the phase transition of the ?1-minimization problem. Finally, we show that the spread spectrum technique remains effective in an analog setting with chirp modulation for application to realistic Fourier imaging. We illustrate these findings in the context of radio interferometry and magnetic resonance imaging.

Puy, Gilles; Vandergheynst, Pierre; Gribonval, Rémi; Wiaux, Yves

2012-12-01

67

Image encryption based on extended fractional Fourier transform and digital holography technique  

NASA Astrophysics Data System (ADS)

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.

Wang, Xiaogang; Zhao, Daomu; Chen, Linfei

2006-04-01

68

Chemical imaging with Fourier transform coherent anti-Stokes Raman scattering microscopy.  

PubMed

We report chemical imaging using Fourier transform coherent anti-Stokes Raman scattering (FTCARS) microscopy. Adding a passively phase-stable local field to amplify the weak FTCARS signal, we also demonstrate interferometric FTCARS microscopy, permitting reduced incident power to be used for imaging. We discuss signal-to-noise considerations and the conditions necessary to effectively suppress background noise, allowing FTCARS microscopy that is limited by the shot noise of the detector. We also discuss differences between the signal-to-noise obtainable by time and frequency domain coherent anti-Stokes Raman scattering (CARS) methods. PMID:19122721

Cui, Meng; Skodack, Joshua; Ogilvie, Jennifer P

2008-11-01

69

Non-iterative determination of pattern phase in structured illumination microscopy using auto-correlations in Fourier space.  

PubMed

The artefact-free reconstruction of structured illumination microscopy images requires precise knowledge of the pattern phases in the raw images. If this parameter cannot be controlled precisely enough in an experimental setup, the phases have to be determined a posteriori from the acquired data. While an iterative optimisation based on cross-correlations between individual Fourier images yields accurate results, it is rather time-consuming. Here I present a fast non-iterative technique which determines each pattern phase from an auto-correlation of the respective Fourier image. In addition to improving the speed of the reconstruction, simulations show that this method is also more robust, yielding errors of typically less than ?/500 under realistic signal-to-noise levels. PMID:24150313

Wicker, Kai

2013-10-21

70

Reconstruction of multispectral image cubes from multiple- telescope array Fourier transform imaging spectrometer  

Microsoft Academic Search

Multiple-telescope arrays can function as Fourier transform imaging spectrometers, using the subaperture path-delay elements. However, the resulting spectral images are missing low spatial-frequency content. Reconstruction results are presented for a cube of simulated data using a nonlinear derivative-based sharpness metric that is designed for specific types of imagery.

Samuel T. Thurman; James R. Fienup

71

Ghost imaging of phase objects with classical incoherent light  

SciTech Connect

We describe an optical setup for performing spatial Fourier filtering in ghost imaging with classical incoherent light. This is achieved by a modification of the conventional geometry for lensless ghost imaging. It is shown on the basis of classical coherence theory that with this technique one can realize what we call phase-contrast ghost imaging to visualize pure phase objects.

Shirai, Tomohiro [Electronics and Photonics Research Institute, National Institute of Advanced Industrial Science and Technology, 1-2-1 Namiki, Tsukuba 305-8564 (Japan); Setaelae, Tero [Department of Applied Physics, Aalto University, P.O. Box 13500, FI-00076 Aalto (Finland); Friberg, Ari T. [Department of Applied Physics, Aalto University, P.O. Box 13500, FI-00076 Aalto (Finland); Department of Physics and Mathematics, University of Eastern Finland, P.O. Box 111, FI-80101 Joensuu (Finland); Department of Microelectronics and Applied Physics, Royal Institute of Technology, Electrum 229, SE-164 40 Kista (Sweden)

2011-10-15

72

IFIRS: an Imaging Fourier Transform Spectrometer for NGST  

NASA Astrophysics Data System (ADS)

To accomplish the scientific objectives of NGST, the observatory must be equipped with instruments suitable for panchromatic observations across the 1-15 mu m spectral region on the faintest detectable objects. A wide-field imaging spectrometer that is efficient in the confusion limit, which may occur in deep field images, will maximize the scientific return and opportunities for serendipity from NGST. An imaging Fourier transform spectrometer (IFTS) supports these requirements in a low-cost, efficient instrument package that functions as an electronically programmable infrared filter with both imaging and spectroscopic capability. The conceptual design of the Integral Field Infrared Spectrograph (IFIRS) is an imaging FTS configured as a 4-port Michelson interferometer. The added ports are obtained by the use of cube-corner retroreflectors. A 4-port design delivers complementary symmetric and antisymmetric interferograms to the primary and secondary focal plane assemblies (FPAs). In this design, the object field of the complementary input is also imaged and superimposed on each image of the primary input. In operation, when observing the sky in the primary input, the secondary input would be fed with a cold blackbody having negligible radiance. The final interferogram is constructed from the difference between the two outputs (which is therefore also immune to common mode noise) while the normalized ratio of the difference to the sum of the two outputs serves to compensate for temporal variations in the object radiance, and may reveal systematic variations due to telescope throughput or detector drifts. The interferometer aperture, field angle, beam waist control, beamsplitter/beamcombiner co-planar alignment, maximum optical frequency and maximum resolution have been traded at a conceptual level of detail. These tradeoffs suggest that a 12 cm beam splitter diameter is sufficient to accept the throughput of an 8 m primary over a 3.'4 x 3.'4 square field of view.

Graham, J. R.; Macoy, N. H.; Wickham, D. R.; Hertel, R. J.; Abrams, M. C.; Bennett, C. L.; Cook, K. H.; Wurtz, R.; Carr, J.; Dey, A.; Najita, J. R.; Morris, S. L.; Villemaire, A.; Wishnow, E.

1998-12-01

73

IFIRS: an Imaging Fourier Transform Spectrometer for NGST  

NASA Astrophysics Data System (ADS)

To accomplish the scientific objectives of NGST, the observatory must be equipped with instruments suitable for panchromatic observations across the 1-15 mu m spectral region on the faintest detectable objects. A wide-field imaging spectrometer that is efficient in the confusion limit, which may occur in deep field images, will maximize the scientific return and opportunities for serendipity from NGST. An imaging Fourier transform spectrometer (IFTS) supports these requirements in a low-cost, efficient instrument package that functions as an electronically programmable infrared filter with both imaging and spectroscopic capability. The conceptual design of the Integral Field Infrared Spectrograph (IFIRS) is an imaging FTS configured as a 4-port Michelson interferometer. The added ports are obtained by the use of cube-corner retroreflectors. A 4-port design delivers complementary symmetric and antisymmetric interferograms to the primary and secondary focal plane assemblies (FPAs). In this design, the object field of the complementary input is also imaged and superimposed on each image of the primary input. In operation, when observing the sky in the primary input, the secondary input would be fed with a cold blackbody having negligible radiance. The final interferogram is constructed from the difference between the two outputs (which is therefore also immune to common mode noise) while the normalized ratio of the difference to the sum of the two outputs serves to compensate for temporal variations in the object radiance, and may reveal systematic variations due to telescope throughput or detector drifts. The interferometer aperture, field angle, beam waist control, beamsplitter/beamcombiner co-planar alignment, maximum optical frequency and maximum resolution have been traded at a conceptual level of detail. These tradeoffs suggest that a 12 cm beam splitter diameter is sufficient to accept the throughput of an 8 m primary over a 5.'3 x 5.'3 square field of view.

Graham, J. R.; Macoy, N. H.; Wickham, D. R.; Hertel, R. J.; Abrams, M. C.; Bennett, C. L.; Cook, K.; Wurtz, R.; Carr, J.; Dey, A.; Najita, J.; Morris, S.; Villemaire, A.; Wishnow, E.

1999-05-01

74

Transformation in mandibular imaging with sweep imaging with fourier transform magnetic resonance imaging  

PubMed Central

Objective Current imaging techniques are often sub-optimal for the detection of mandibular invasion by squamous cell carcinoma. The aim of this study was to determine the feasibility of a magnetic resonance imaging (MRI) based technique known as Sweep Imaging with Fourier Transform (SWIFT) to visualize the structural changes of intra-mandibular anatomy during invasion. Design Descriptive case study Setting Tertiary academic institution Method Two specimens from patients with oral carcinoma who underwent segmental mandibulectomy were imaged using a 9.4 Tesla Varian MRI system. The SWIFT images were correlated with histological sections. Results The SWIFT technique with in vitro specimens produced images with sufficient resolution (156–273) and contrast to allow accurate depiction of tumor invasion of cortical and medullary bone. Both specimens had histopathological evidence of mandibular invasion with tumor. A high degree of correlation was found between MR images and histopathologic findings. Conclusion SWIFT MRI offers three-dimensional assessment of cortical and medullary bone in fine detail with excellent qualitative agreement with histopathology. MR imaging with the SWIFT technique demonstrates great potential to identify mandibular invasion by oral carcinoma.

Kendi, Ayse Tuba Karagulle; Khariwala, Samir S.; Zhang, Jinjin; Idiyatullin, Djaudat S.; Corum, Curtis A.; Michaeli, Shalom; Pambuccian, Stefan E.; Garwood, Michael; Yueh, Bevan

2012-01-01

75

Phase Contrast Imaging  

SciTech Connect

All standard (medical) x-ray imaging technologies, rely primarily on the amplitude properties of the incident radiation, and do not depend on its phase. This is unchanged since the discovery by Roentgen that the intensity of an x-ray beam, as measured by the exposure on a film, was related to the relative transmission properties of an object. However, recently various imaging techniques have emerged which depend on the phase of the x-rays as well as the amplitude. Phase becomes important when the beam is coherent and the imaging system is sensitive to interference phenomena. Significant new advances have been made in coherent optic theory and techniques, which now promise phase information in medical imaging. The development of perfect crystal optics and the increasing availability of synchrotron radiation facilities have contributed to a significant increase in the application of phase based imaging in materials and life sciences. Unique source characteristics such as high intensity, monochromaticity, coherence and high collimating provide an ideal source for advanced imaging. Phase contrast imaging has been applied in both projection and computed tomography modes, and recent applications have been made in the field of medical imaging. Due to the underlying principle of X-ray detection conventional image receptors register only intensities of wave fields and not their phases. During the last decade basically five different methods were developed that translate the phase information into intensity variations. These methods are based on measuring the phase shift {phi} directly (using interference phenomena), the gradient {nabla}{sub {phi}}, or the Laplacian {nabla}{sup 2}{phi}. All three methods can be applied to polychromatic X-ray sources keeping in mind that the native source is synchrotron radiation, featuring monochromatic and reasonable coherent X-ray beams. Due to the vast difference in the coefficients that are driven absorption and phase effects (factor 1,000-10,000 in the energy range suitable for medical imaging) phase based imaging techniques are inherently extremely sensitive.

Menk, Ralf Hendrik [Sincrotrone Trieste and INFN Trieste (Italy)

2008-11-13

76

Development of an Imaging Fourier Transform Spectrometer for Astronomy  

NASA Astrophysics Data System (ADS)

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.

Grandmont, Frederic; Drissen, Laurent; Joncas, Gilles

2003-02-01

77

ULTRASOUND PULSE-ECHO IMAGING USING THE SPLIT-STEP FOURIER PROPAGATOR  

SciTech Connect

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. The inward continuation within each extrapolation interval consists of two steps. In the first step, a phase-shift term is applied to the data in the frequency-wavenumber domain for propagation in a reference medium. The second step consists of applying another phase-shift term to data in the frequency-space domain to approximately compensate for ultrasonic scattering effects of heterogeneities within the breast. We use synthetic ultrasound pulse-echo data recorded around a ring for heterogeneous, computer-generated numerical breast phantoms to study the imaging capability of the method. The phantoms are derived from an experimental breast phantom and a sound-speed tomography image of an in-vivo ultrasound breast data collected usi ng a ring array. The heterogeneous sound-speed models used for pulse-echo imaging are obtained using a computationally efficient, first-arrival-time (time-of-flight) transmission tomography method. Our studies demonstrate that reflection image reconstruction using the split-step Fourier propagator with heterogeneous sound-speed models significantly improves image quality and resolution. We also numerically verify the spatial sampling criterion of wavefields for a ring transducer array.

HUANG, LIANJIE [Los Alamos National Laboratory; QUAN, YOULI [Los Alamos National Laboratory

2007-01-31

78

Optical phase retrieval by phase-space tomography and fractional-order Fourier transforms  

Microsoft Academic Search

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.

D. F. McAlister; M. Beck; L. Clarke; A. Mayer; M. G. Raymer

1995-01-01

79

Amplitude and phase fourier correlation of ``twin'' GC-spectra of fatty acids from sheep dairy  

NASA Astrophysics Data System (ADS)

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.

Teusdea, Alin C.; Gabor, Gianina; Hilma, Elena

2012-08-01

80

Recursive Algorithm for Phase Retrieval in the Fractional Fourier Transform Domain  

Microsoft Academic Search

We first discuss the discrete fractional Fourier transform and present some essential properties. We then propose a recursive algorithm to implement phase retrieval from two intensities in the fractional Fourier transform domain. This approach can significantly simplify computational manipulations and does not need an initial phase estimate compared with conventional iterative algorithms. Simulation results show that this approach can successfully

Wen-Xiang Cong; Nan-Xian Chen; Ben-Yuan Gu

1998-01-01

81

Research on the sequential images registration of the temporally and spatially modulated Fourier transform imaging spectrometer  

NASA Astrophysics Data System (ADS)

Temporally and Spatially Modulated Fourier Transform Imaging Spectrometer (TSMFTIS) is a new imaging spectrometer without moving mirror and slit. Through scanning, it can acquire sequential images superposed with interference fringes. The interferogram can be acquired by orderly arranging the extracted interference information of the same spatial point from the sequential images, and the spectrum can be recovered by using FFT. Therefore, the attitude of the bearing platform will affect the images so as to reduce the accuracy of the recovered spectrums. Since current attitude measurement accuracy can not meet the needs of error correction, in this paper, the image registration method is applied to acquire the accurate translations for the future correction between two sequential images. The single-step DFT registration method is applied to register the selected window areas away from the null optical path difference position in sequential images. That is full utilizing of common information meanwhile reducing impact of interference fringes and improving registration accuracy and efficiency. In the simulation experiment, a common large remote sensing image is used as ground object. The Fourier shift principle is applied to acquire simulation scanning images with sub-pixel displacement. Artificial spectral data cube produced with the RGB values of each image is utilized as the input data of the TSMFTIS, and sequential images superposed with interference fringes are acquired. Registration according to the method mentioned above is performed and the results are compared with the accurate values. It shows that the method is feasible and can achieve sub-pixel level accuracy.

Zhang, Xiubao; Wang, Qian; Zhou, Zhiliang; Sun, Chengming

2010-10-01

82

Comparison of Fourier transform, windowed Fourier transform, and wavelet transform methods for phase calculation at discontinuities in fringe projection pro?lometry  

NASA Astrophysics Data System (ADS)

Phase demodulation techniques from one fringe pattern have been widely studied because it can measure dynamic objects by capturing single image. These techniques mainly include Fourier transform (FT), windowed Fourier transform (WFT), and wavelet transform (WT). FT has been widely used to demodulate phase information from single deformed fringe pattern on smooth objects. However, for objects having discontinuities and/or large slopes, FT cannot obtain correct phase at the edges because of its global processing. WFT and WT have been applied to nonstationary fringe pattern analysis. Since local fringe information used to extract phase information, WFT and WT are better than FT for phase calculation at discontinuities and/or slopes. In this paper, we discuss the pro and con of the three methods on phase calculation at discontinuities and/or slopes. Simulated and experimental data are tested at edges in order to confirm which method is appropriate to measure objects having discontinuities by using one-frame fringe pattern acquisition method.

Zhang, Zonghua; Jing, Zhao; Wang, Zhaohui; Kuang, Dengfeng

2012-08-01

83

Imaging Fourier transform endospectroscopy for in vivo and in situ multispectral imaging.  

PubMed

We report the design and implementation of a multispectral imaging Fourier transform endospectroscopy (IFTES) system. The IFTES system employs a flexible fiber bundle catheter coupled to a home-built imaging Fourier transform spectroscope. The instrument enables the performance of non- or minimally invasive subsurface imaging and multispectral imaging at the cellular level in vivo and in situ. A maximum spectral resolution of 0.2 nm at 632.8 nm and a lateral resolution of 4.4 ?m were proved. Preliminary results of a standard resolution target, ex-vivo small animal tissue, single wavelength laser, fluorescence solution, in-vivo mouse skin, microspheres mixture, and in-vivo transgenic mouse brain were given to demonstrate the potential of the technique. PMID:23188298

Zhang, Hongming; Yuan, Jing; Fu, Ling

2012-10-01

84

Phase retrieval for a complex-valued object by using a low-resolution image  

Microsoft Academic Search

It is difficult to reconstruct an image of a complex-valued object from the modulus of its Fourier transform (i.e., retrieve the Fourier phase) except in some special cases. By using additionally a low-resolution intensity image from a telescope with a small aperture, a fine-resolution image of a general object can be reconstructed in a two-step approach. First the Fourier phase

J. R. Fienup; A. M. Kowalczyk

1990-01-01

85

Parallel two-step spatial carrier phase-shifting common-path interferometer with a Ronchi grating outside the Fourier plane.  

PubMed

A parallel two-step spatial carrier phase-shifting common-path interferometer with a Ronchi grating placed outside the Fourier plane is proposed in this paper for quantitative phase imaging. Two phase-shifted interferograms with spatial carrier can be captured simultaneously using the proposed interferometer. The dc term can be eliminated by subtracting the two phase-shifted interferograms, and the phase of a specimen can be reconstructed through Fourier transform. The validity and stability of the interferometer proposed are experimentally demonstrated via the measurement of a phase plate. PMID:23389193

Shan, Mingguang; Hao, Bengong; Zhong, Zhi; Diao, Ming; Zhang, Yabin

2013-01-28

86

Nonlinear optical Fourier filtering technique for medical image processing.  

PubMed

Real-time nonlinear optical Fourier filtering for medical image processing is demonstrated, exploiting light modulating characteristics of thin films of the biophotonic material bacteriorhodopsin (bR). The nonlinear transmission of bR films for a 442 nm probe beam with a 568 nm control beam and vice versa is experimentally studied in detail. The spatial frequency information carried by the blue probe beam is selectively manipulated in the bR film by changing the position and intensity of the yellow control beam. The feasibility of the technique is first established with different shapes and sizes of phantom objects. The technique is applied to filter out low spatial frequencies corresponding to soft dense breast tissue and displaying only high spatial frequencies corresponding to microcalcifications in clinical screen film mammograms. With the aid of an electrically addressed spatial light modulator (SLM), we successfully adapt the technique for processing digital phantoms and digital mammograms. Unlike conventional optical spatial filtering techniques that use masks, the technique proposed can easily accommodate the changes in size and shape of details in a mammogram. PMID:16178661

Kothapalli, Sri-Rajasekhar; Wu, Pengfei; Yelleswarapu, Chandra S; Rao, D V G L N

87

Arithmetic Fourier Transform (AFT): Iterative Computation and Image Processing Applications.  

National Technical Information Service (NTIS)

A Fourier analysis method using an iterative Arithmetic Fourier Transform (AFT) is presented. It overcomes the difficulty of dense, Farey-fraction sampling which is inherent in the original AFT algorithm. This disadvantage of the AFT is turned into an adv...

D. W. Tufts H. Chen

1992-01-01

88

Phase image encryption of colored images using double random phase encoding technique in HSV color space  

NASA Astrophysics Data System (ADS)

A double random phase encoding based digital phase encryption technique for colored images is proposed in the Fourier domain. The RGB input image is brought to HSV color space and then converted into phase, prior to the encryption. In the decryption process the HSV image is and converted back to the RGB format. The random phase codes used during encryption are prepared by stacking three two-dimensional random phase masks. These random phase codes serve as keys for encryption and decryption. The proposed technique carries all the advantages of phase encryption and is supposedly three-dimensional in nature. Robustness of the technique is analyzed against the variations in random phase codes and shuffling of the random phase masks of a given phase code. Performance of the scheme is also verified against occlusion of Fourier plane random phase code as well as the encrypted image. Effects of noise attacks and attacks using partial windows of correct random phase codes have also been checked. Digital simulations are presented to support the idea.

Joshi, Madhusudan; Shakher, Chandra; Singh, Kehar

2009-09-01

89

SIMULATION OF THE FOURIER PHASE SPECTRUM FOR THE GENERATION OF SYNTHETIC ACCELEROGRAMS  

Microsoft Academic Search

This study presents the application of a new method for generating synthetic accelerograms based on statistical distributions for Fourier phase differences and Fourier amplitudes as functions of earthquake magnitude, hypocentral distance and site geology. Two important characteristics of the methodology are that it requires a small number of input parameters and that ground motion time histories can be simulated without

V. MONTALDO; A. S. KIREMIDJIAN; H. THRÁINSSON; G. ZONNO

2003-01-01

90

Adaptive correction of phase-distorted extended-source images  

NASA Astrophysics Data System (ADS)

An experimental model of an adaptive imaging system for compensation of large-scale phase distortions under conditions of strongly anisoplanatic imaging is studied. We investigate adaptive compensation of phase-distorted extended source images using new types of image quality criteria. These image quality criteria are dependent on the Fourier spectrum of the image, and can be obtained using a coherent optical system. For adaptive control of a ten electrode continuously deformable bimorph mirror, simple gradient algorithms for image quality criteria were applied. We experimentally demonstrate the efficiency of large-scale phase distortion compensation for extended and complex targets.

Carhart, Gary W.; Pruidze, Dimitri V.; Ricklin-Vorontsova, Jennifer C.; Voelz, David G.; Vorontsov, Mikhail A.

1996-10-01

91

Spectroscopic-tomography of biological membrane with high-spatial resolution by the imaging-type 2D Fourier spectroscopy  

NASA Astrophysics Data System (ADS)

We proposed the imaging-type 2-dimensional Fourier spectroscopy that is the phase-shift interferometry between the objective lights. The proposed method can measure the 2D spectral image at the limited depth. Because of the imaging optical system, the 2D spectral images can be measured in high spatial resolution. And in the depth direction, we can get the spectral distribution only in the focal plane. In this report, we mention about the principle of the proposed wide field imaging-type 2D Fourier spectroscopy. And, we obtained the spectroscopic tomography of biological tissue of mouse's ear. In the visible region, we confirmed the difference of spectral characteristics between blood vessel region and other region. In the near infrared region (?=900nm~1700nm), we can obtain the high-contrast blood vessel image of mouse's ear in the deeper part by InGaAs camera. Furthermore, in the middle infrared region(?=8?~14?m), we have successfully measured the radiation spectroscopic-imaging with wild field of view by the infrared module, such as the house plants. Additionally, we propose correction geometrical model that can convert the mechanical phase-shift value into the substantial phase difference in each oblique optical axes. We successfully verified the effectiveness of the proposed correction geometrical model and can reduce the spectral error into the error range into +/-3nm using the He-Ne laser whose wavelength 632.8nm.

Inui, Asuka; Tsutsumi, Ryosuke; Qi, Wei; Takuma, Takashi; Ishimaru, Ichiro

2011-06-01

92

High-resolution Fourier-encoded sub-millisecond echo time musculoskeletal imaging at 3 Tesla and 7 Tesla.  

PubMed

PURPOSE: The feasibility of imaging musculoskeletal fibrous tissue components, such as menisci, ligaments, and tendons, with a conventional spoiled gradient echo technique is explored in vivo at 3 T and 7 T. METHODS: To this end, the echo time (TE(1) ) of a conventional Fourier-encoded multicontrast three-dimensional SGPR sequence is minimized by using nonselective excitation pulses, highly asymmetric readouts, and a variable TE(1) along the phase and slice encoding direction. In addition, a fully sampled second echo image (with TE(2) > TE(1) ) can be used to highlight components with short transverse relaxation times in a difference image with positive contrast. RESULTS: Fourier-encoded spoiled gradient echo sequences are able to provide sub-millisecond TE(1) of about 800 ?s for typical in-plane resolutions of about 0.5 x 0.5 mm(2) . As a result, high-resolution positive contrast images of fibrous tissues can be generated within clinically feasible scan-time of about 2-7 minutes. CONCLUSION: After optimization, Fourier-encoded spoiled gradient echo provides a highly robust and flexible imaging technique for high-resolution positive contrast imaging of fibrous tissue that can readily be used in the clinical routine. Magn Reson Med, 2013. © 2012 Wiley Periodicals, Inc. PMID:23233430

Deligianni, X; Bär, P; Scheffler, K; Trattnig, S; Bieri, O

2012-12-11

93

Complex spectral Fourier-domain imaging method for Synthetic Aperture Microwave Radiometer  

Microsoft Academic Search

Conventional microwave radiometer belongs to spatial-domain imaging system to detect area thermal source and it acquires radiometric signal from the object source point and point. Synthetic Aperture Microwave Radiometer belongs to staring imaging system. It applies Fourier-domain technique to obtain source's microwave spectrum called visibility and thus make scanning process not necessary. This novel imaging method can save much consuming

Qiong Wu; Ji Wu

2010-01-01

94

Binary Phase Only Filter as an Image Watermark.  

National Technical Information Service (NTIS)

We describe our new method for watermarking digital images. Our work is motivated by the study of phase only filters in Fourier optics. In this paper we concentrate on grey scale images, even though our method works for color also. We take the discrete Fo...

F. Ahmed I. S. Moskowitz

2004-01-01

95

Fourier-phase method for the location of moving objects  

NASA Astrophysics Data System (ADS)

A novel method is presented that permits one to locate a moving object. According to this method, the change in location of a moving object can be detected from its Fourier spectrum. This method has the advantages of a high-precision locating mechanism and the capacity to permit one to ignore the change in the orientation and the size of the moving object. The principles are introduced, a computer simulation and experimental demonstration are given, and the practicality of this method is discussed.

Chen, Tie-Qi; Zhang, Chun; Xu, Ke-Shu

1995-06-01

96

3D quantitative Fourier analysis of second harmonic generation microscopy images of collagen structure in cartilage  

NASA Astrophysics Data System (ADS)

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.

Romijn, Elisabeth I.; Lilledahl, Magnus B.

2013-02-01

97

Phase retrieval from the magnitude of the Fourier transforms of nonperiodic objects  

Microsoft Academic Search

It is suggested that, given the magnitude of Fourier transforms sampled at the Bragg density, the phase problem is underdetermined by a factor of 2 for 1D, 2D, and 3D objects. It is therefore unnecessary to oversample the magnitude of Fourier transforms by 2Ã in each dimension (i.e., oversampling by 4Ã for 2D and 8Ã for 3D) in retrieving the

J. Miao; D. Sayre; H. N. Chapman

1998-01-01

98

Optical Fourier and Holographic Techniques for Medical Image Processing with Bacteriorhodopsin  

NASA Astrophysics Data System (ADS)

The biological photochrome bacteriorhodopsin (bR) shows many intrinsic optical and physical properties. The active chromophore in bR is a retinal group which absorbs light and goes through a photocycle. The unique feature of the system is its flexibility -- the photocycle can be optically controllable since the process of photoisomerization can go in both directions depending on wavelength, intensity and polarization of the incident light, opening a variety of possibilities for manipulating amplitude, phase, polarization and index of refraction of the incident light. Over the years we studied the basic nonlinear optics and successfully exploited the unique properties for several optical spatial filtering techniques with applications in medical image processing. For nonlinear Fourier filtering, the photo-controlled light modulating characteristics of bR films are exploited. At the Fourier plane, the spatial frequency information carried by a blue probe beam at 442 nm is selectively manipulated in the bR film by changing the position and intensity of a yellow control beam at 568 nm. In transient Fourier holography, photoisomerizative gratings are recorded and reconstructed in bR films. Desired spatial frequencies are obtained by matching the reference beam intensity to that of the particular frequency band in object beam. A novel feature of the technique is the ability to transient display of selected spatial frequencies in the reconstructing process which enables radiologists to study the features of interest in time scale. The results offer useful information to radiologists for early detection of breast cancer. Some of the highlights will be presented.

Yelleswarapu, Chandra

2008-03-01

99

Discovering ordered phases of block copolymers: new results from a generic Fourier-space approach.  

PubMed

A generic Fourier-space approach to solve the self-consistent field theory of block copolymers is developed. This approach is based on the fact that, for any computational box with periodic boundary conditions, all spatially varying functions are spanned by the Fourier series determined by the size and shape of the box. The method reproduces all known diblock copolymer phases. The application of this method to a model "frustrated" triblock copolymer leads to a phase diagram with a number of new phases. Furthermore, the capability of the method to reproduce experimentally observed structures is demonstrated using the knitting pattern of triblock copolymers. PMID:18764231

Guo, Zuojun; Zhang, Guojie; Qiu, Feng; Zhang, Hongdong; Yang, Yuliang; Shi, An-Chang

2008-07-08

100

Effect of motion on two-dimensional Fourier transformation magnetic resonance images. [Dogs, phantoms  

SciTech Connect

The effect of motion on two-dimensional Fourier transformation magnetic resonance (MR) images was investigated using phantoms, animals, and normal volunteers. Respiratory motion was simulated while imaging the phantoms. In addition to image blurring, motion produced ghost images, or image harmonics. Canine images, which were obtained during respiration and after the administration of curare, showed significant improvement after respiratory motion was eliminated. Images of normal volunteers were improved with respiratory and cardiac gating, but data acquisition time was significantly increased. These results indicate that MR image quality could be improved with a system that acquires all necessary data within a single breathhold.

Schultz, C.L.; Alfidi, R.J.; Nelson, A.D.; Kopiwoda, S.Y.; Clampitt, M.E.

1984-07-01

101

Phase Retrieval Between Overlapping Orders in Coherent Fourier Scatterometry Using Scanning  

NASA Astrophysics Data System (ADS)

Non-interferometric phase retrieval from the intensity measurements in Coherent Fourier Scatterometry (CFS) is presented using a scanningfocused spot. Formulae to determine the state of polarization of the scattered light and to retrieve the phase difference between overlappingscattered orders are given. The scattered far field is rigorously computed and the functionality of the method is proved with experimentalresults.

Kumar, N.; El Gawhary, O.; Roy, S.; Pereira, S. E.; Urbach, H. P.

2013-07-01

102

Discrete Fourier Transform based multimedia colour image authentication for wireless communication (DFTMCIAWC)  

Microsoft Academic Search

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

Nabin Ghoshal; J. K. Mandal

2011-01-01

103

SITELLE: a wide-field imaging Fourier transform spectrometer for the Canada-France-Hawaii Telescope  

Microsoft Academic Search

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 -

L. Drissen; A.-P. Bernier; L. Rousseau-Nepton; A. Alarie; C. Robert; G. Joncas; S. Thibault; F. Grandmont

2010-01-01

104

Iterative Image Reconstruction Using Inverse Fourier Rebinning for Fully 3-D PET  

Microsoft Academic Search

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

Sanghee Cho; Quanzheng Li; Sangtae Ahn; Bing Bai; Richard M. Leahy

2007-01-01

105

Translational Diffusion of Fluorescent Proteins by Molecular Fourier Imaging Correlation Spectroscopy  

Microsoft Academic Search

The ability to noninvasively observe translational diffusion of proteins and protein complexes is important to many biophysical problems. We report high signal\\/noise (?250) measurements of the translational diffusion in viscous solution of the fluorescent protein, DsRed. This is carried out using a new technique: molecular Fourier imaging correlation spectroscopy (M-FICS). M-FICS is an interferometric method that detects a collective Fourier

Michael C. Fink; Kenneth V. Adair; Marina G. Guenza; Andrew H. Marcus

2006-01-01

106

Modeling of woven fabric structures based on Fourier image analysis  

NASA Astrophysics Data System (ADS)

The periodic woven structures of fabrics can be defined on the basis of the convolution theorem. Here an elementary unit with the minimum number of thread crossings and a nonrectangular two-dimensional comb function for the pattern of repetition is used to define woven structures. The expression derived is more compact than the conventional diagram for weaving, and the parameters that one needs to determine a given fabric can easily be extracted from its Fourier transform. Several results with real samples of the most common structures-plain, twill, and satin-are presented.

Escofet, Jaume; Millán, Maria S.; Ralló, Miquel

2001-12-01

107

The data processing pipeline for the Herschel\\/SPIRE Imaging Fourier Transform Spectrometer  

Microsoft Academic Search

We present 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 source, jiggle- and raster-map observations, producing calibrated spectra in low-, medium-, high-, and mixed low- and high- resolution modes. The spectrometer pipeline shares some elements with the SPIRE photometer pipeline,

Trevor R. Fultona; David A. Naylorb; Peter Davis-Imhofa; M. Swinyarde; Tanya L. Lime; Nanyao Luh; France Marseille

108

On the Fourier coefficients for the phase-shift keyed phase density function  

Microsoft Academic Search

Prabhu (1969) has reported an approach whereby the density is expanded into a (converging) Fourier series. It is shown that all the Fourier coefficients in Prabhu's series can be placed into a simple closed form, suitable for machine computation. The two sets of Bessel functions involved in the calculation of the Fourier coefficients can be easily and accurately generated on

J. W. Matthews

1975-01-01

109

Implementation and assessment of diffusion-weighted partial Fourier readout-segmented echo-planar imaging.  

PubMed

Single-shot echo-planar imaging has been used widely in diffusion magnetic resonance imaging due to the difficulties in correcting motion-induced phase corruption in multishot data. Readout-segmented EPI has addressed the multishot problem by introducing a two-dimensional nonlinear navigator correction with online reacquisition of uncorrectable data to enable acquisition of high-resolution diffusion data with reduced susceptibility artifact and T*(2) blurring. The primary shortcoming of readout-segmented EPI in its current form is its long acquisition time (longer than similar resolution single-shot echo-planar imaging protocols by approximately the number of readout segments), which limits the number of diffusion directions. By omitting readout segments at one side of k-space and using partial Fourier reconstruction, readout-segmented EPI imaging times could be reduced. In this study, the effects of homodyne and projection onto convex sets reconstructions on estimates of the fractional anisotropy, mean diffusivity, and diffusion orientation in fiber tracts and raw T(2)- and trace-weighted signal are compared, along with signal-to-noise ratio results. It is found that projections onto convex sets reconstruction with 3/5 segments in a 2 mm isotropic diffusion tensor image acquisition and 9/13 segments in a 0.9 × 0.9 × 4.0 mm(3) diffusion-weighted image acquisition provide good fidelity relative to the full k-space parameters. This allows application of readout-segmented EPI to tractography studies, and clinical stroke and oncology protocols. PMID:22535706

Frost, Robert; Porter, David A; Miller, Karla L; Jezzard, Peter

2011-12-28

110

Image-spectroscopy – II. The removal of plural scattering from extended energy-filtered series by Fourier deconvolution  

Microsoft Academic Search

The increased spectral information obtained by acquiring an EFTEM image-series over several hundred eV allows plural scattering to be removed from loss images using standard deconvolution techniques developed for the quantification of EEL spectra. In this work, both Fourier-log and Fourier-ratio deconvolution techniques have been applied successfully to such image-series. Application of the Fourier-log technique over an energy-loss range of

P. J Thomas; P. A Midgley

2001-01-01

111

Global phase and minimum time of quantum Fourier transform for qudits represented by quadrupole nuclei  

NASA Astrophysics Data System (ADS)

We demonstrate the relation between a global phase of the quantum gate and the layout of energy levels of its effective Hamiltonian required for implementing the gate for minimum time. By an example of the quantum Fourier transform gate for a qudit represented by a quadrupole nucleus with the spin I = 1, the effective Hamiltonians and minimum implementation times for different global phases are found. Using numerical optimal control methods, the problem of the global phase in searching for the optimal pulse shape is considered in detail for the quantum Fourier transform gate at I = 1, 3/2, 2, and 5/2. It is shown that at the constrained control time the gradient algorithms can converge to the solutions corresponding to different global phases or the same global phase with different minimum times of the gate implementation.

Shauro, V. P.; Zobov, V. E.

2013-10-01

112

Cardiac motion tracking using CINE harmonic phase (HARP) magnetic resonance imaging  

Microsoft Academic Search

This article introduces a new image processing technique for rapid analysis of tagged cardiac magnetic resonance image sequences. The method uses isolated spectral peaks in SPAMM- tagged magnetic resonance images, which contain information about cardiac motion. The inverse Fourier transform of a spectral peak is a complex image whose calculated angle is called a harmonic phase (HARP) image. It is

Nael F. Osman; William S. Kerwin; Elliot R. McVeigh; Jerry L. Prince

1999-01-01

113

Extreme Ultraviolet Phase Contrast Imaging  

SciTech Connect

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.

Denbeaux, Gregory; Garg, Rashi; Aquila, Andy; Barty, Anton; Goldberg, Kenneth; Gullikson, Eric; Liu, Yanwei; Wood, Obert

2005-11-01

114

The Fourier-spectrum of circular sine and cosine gratings with arbitrary radial phases  

NASA Astrophysics Data System (ADS)

The Fourier spectra of circular gratings having sine or cosine radial profiles are derived, and their particular properties are discussed. These results are then extended to the most general form of circular sinusoidal gratings, namely: circular sine or cosine gratings with any arbitrary radial phase.

Amidror, Isaac

1998-04-01

115

Phase retrieval from series of images obtained by defocus variation  

Microsoft Academic Search

We develop and compare three different methods of phase retrieval from series of image measurements obtained at different defocus values. The first approach is an approximate solution to the transport of intensity equation (TIE) based on Fourier transforms. The second is an exact solution of the TIE, using multigrid methods. Lastly an iterative approach, using the free space propagator between

L. J. Allen; M. P. Oxley

2001-01-01

116

High resolution imaging using phase retrieval, volume 2  

NASA Astrophysics Data System (ADS)

This report describes a technique for obtaining fine-resolution images, suitable for SDI midcourse discrimination, using an inexpensive, lightweight telescope that would ordinarily yield a poor image. If, instead of collecting a blurred image with the telescope, one sends the light through an amplitude interferometer, then the modulus, but not the phase, of the Fourier transform of the object can be measured, despite the aberrations. We have developed and analyzed phase retrieval algorithms that recover the unknown Fourier phase, which allows a fine-resolution image to be reconstructed despite the aberrations of the telescope. It will also correct aberrations due to atmospheric turbulence for a ground-based telescope, and can be used with several other imaging modalities. For the case of interferometry through a partially obscured aperture, an algorithm was developed that combines phase retrieval with interpolation in order to restore the information at the missing spatial frequencies while retrieving the phase at the unobscured spatial frequencies. Another new phase retrieval algorithm, based on the Ayers/Dainty blind deconvolution algorithm, was also developed. A new methodology for exploring the uniqueness of phase retrieval in a practical sense was developed and tested. It involves finding the ambiguous image which is closest to a given image by a reduced-gradient search technique. The computational requirements for the phase retrieval algorithm were quantified. Laboratory experiments to test the technique were initiated.

Fienup, J. R.; Gorman, J. D.; Seldin, J. H.; Cederquist, J. N.

1991-10-01

117

High-resolution magnetic-domain imaging by Fourier transform holography at 21 nm wavelength  

NASA Astrophysics Data System (ADS)

Exploiting x-ray magnetic circular dichroism at the L-edges of 3d transition metals, Fourier transform holography has become a standard technique to investigate magnetic samples with sub-100 nm spatial resolution. Here, magnetic imaging in the 21 nm wavelength regime using M-edge circular dichroism is demonstrated. Ultrafast pulses in this wavelength regime are increasingly available from both laser- and accelerator-driven soft x-ray sources. We explain the adaptations concerning sample preparation and data evaluation compared to conventional holography in the 1 nm wavelength range. We find the correction of the Fourier transform hologram to in-plane Fourier components to be critical for high-quality reconstruction and demonstrate 70 nm spatial resolution in magnetization imaging with this approach.

Schaffert, Stefan; Pfau, Bastian; Geilhufe, Jan; Günther, Christian M.; Schneider, Michael; von Korff Schmising, Clemens; Eisebitt, Stefan

2013-09-01

118

Imaging resolution analysis using Fourier-Slice theorem in reflective tomography laser radar  

NASA Astrophysics Data System (ADS)

Reflective tomography is one of the most promising high-resolution imaging methods for the remote objects. But in practical application, because of the sampling angle error and limited view of projections in signal collecting process, anisotropic resolution is inevitable and the reconstruction image quality of reflective tomography system degrades. In this paper, the theoretical imaging resolution derived from Fourier-Slice theorem is presented, computer simulation and experimental verification are also given. Imaging analysis in this paper will make a complement and perfection of the theory in reflective tomography imaging ladar.

Yan, Yi; Jin, Xiaofeng; Zhou, Shuping; Sun, Jianfeng; Liu, Liren

2013-09-01

119

Phase-shifting algorithm via wavelength tuning based on temporal Fourier transform  

NASA Astrophysics Data System (ADS)

The phase-shifting algorithm via wavelength tuning based on temporal Fourier transform is according to the Fourier transform technique and the difference technique to realize the processing of the interferogram. This algorithm is applied to test some course profiles or the topography with high steps. The paper describes its main idea and presents the shortcoming of the algorithm proposed by Takeda. Then it puts forward the improved algorithml. The pape describes the realization processing and the errors of the new algorithm. Finally, it supplies the measurement result.

Yu, Yingjie; Zhang, Benhao; Jiao, Yunfang

2003-11-01

120

Crystallographic phase retrieval through image processing under constraints  

NASA Astrophysics Data System (ADS)

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.

Zhang, Kam Y.

1993-11-01

121

An Effective Approach for Iris Recognition Using Phase-Based Image Matching  

Microsoft Academic Search

This paper presents an efficient algorithm for iris recognition using phase-based image matching - an image matching technique using phase components in 2D discrete Fourier transforms (DFTs) of given images. Experimental evaluation using the CASIA iris image databases (versions 1.0 and 2.0) and Iris challenge evaluation (ICE) 2005 database clearly demonstrates that the use of phase components of iris images

Kazuyuki Miyazawa; Koichi Ito; Takafumi Aoki; Koji Kobayashi; Hiroshi Nakajima

2008-01-01

122

T2-weighted breathold imaging of the liver: a quantitative and qualitative comparison of fast spin echo and half Fourier single shot fast spin echo imaging  

Microsoft Academic Search

The imaging characteristics of two EPI-hybrid breath-hold sequences, T2-weighted fast spin-echo [FSE, effective echo time\\u000a (TEeff) 138ms] and half Fourier single shot turbo spin-echo (HASTE, TEeff 60 ms), were compared in hepatic imaging.\\u000a \\u000a A total of 111 patients with suspected hepatic disease were studied at 1.5 Tesla using a body phase-array coil. The signal-to-noise\\u000a (S\\/N) and contrast-to-noise (C\\/N) ratios for

Thomas K. Helmberger; Julia Schröder; Nicolaus Holzknecht; Michaela Gregor; Andreas Heuck; Rainer Petsch; Maximilian F. Reiser

1999-01-01

123

Designing Fourier Descriptor-Based Geometric Models for Object Interpretation in Medical Images Using Genetic Algorithms  

Microsoft Academic Search

In previous work we have modeled simple 3D anatomical objects using deformed superquadrics and established their optimal position with the aid of genetic algorithms (GAs). Here we extend the complexity of the search object using 3D Fourier descriptor (FD) representations and allow GAs once again to optimize the object's shape and position. Using magnetic resonance image data, we perform an

Konstantinos K. Delibasis; Peter E. Undrill; George G. Cameron

1997-01-01

124

Lossless compression of the geostationary imaging Fourier transform spectrometer (GIFTS) data via predictive partitioned vector quantization  

Microsoft Academic Search

The Geostationary Imaging Fourier Transform Spectrometer (GIFTS), as part of NASA's New Millennium Program, is an advanced instrument to provide high-temporal-resolution measurements of atmospheric temperature and water vapor, which will greatly facilitate the detection of rapid atmospheric changes associated with destructive weather events, including tornadoes, severe thunderstorms, flash floods, and hurricanes. The Committee on Earth Science and Applications from Space

Bormin Huang; Shih-Chieh Wei; Allen H.-L. Huang; Maciek Smuga-Otto; Robert Knuteson; Henry E. Revercomb; William L. Smith Sr.

2007-01-01

125

Three-dimensional analytical magnetic resonance imaging phantom in the Fourier domain  

Microsoft Academic Search

This work presents a basic framework for constructing a 3D analytical MRI phantom in the Fourier domain. In the image domain the phantom is modeled after the work of Kak and Roberts on a 3D version of the famous Shepp-Logan head phantom. This phantom consists of several ellipsoids of differ- ent sizes, orientations, locations, and signal intensities (or gray levels).

Cheng Guan Koay; Joelle E. Sarlls; Evren Özarslan

2007-01-01

126

Optical and Sonar Image Classification: Wavelet Packet Transform vs Fourier Transform  

Microsoft Academic Search

To develop a noise-insensitive texture classification algorithm for both optical and underwater sidescan sonar images, we study the multichannel texture classifi- cation algorithm that uses the wavelet packet transform and Fourier transform. The approach uses a multilevel dominant eigenvector estimation algorithm and statisti- cal distance measures to combine and select frequency channel features of greater discriminatory power. Consistently better performance

Xiaoou Tang; W. Kenneth Stewart

2000-01-01

127

Optical image encryption based on two-dimensional N-parameter fractional Fourier transform  

NASA Astrophysics Data System (ADS)

In this paper, the weighted fractional Fourier transform with dilation parameter (N-PFRFT) is proposed as the weighted combination of the first four integer-order ordinary Fourier transforms. This N-PFRFT is an extension of four-item weighted fractional Fourier transform (N-PFRFT) defined by Shih[1] and it owns four free parameters in the weight coefficients besides the order of the fractional Fourier transform. A novel image encryption algorithm is presented by the N-PFRFT.The method owns more secret keys than the encryption methods operated by other fractional Fourier transforms without any increase of the computational complexity. On the other hand, the image still can't be decrypted correctly even though the order of FRFT which is treated as a secret key is known. So do the four free parameters. Therefore, both the order parameter and the vector parameter can be chosen in the real domain to improve the security of the encryption method. Digital simulations are presented to verify the more validity and efficiency of the algorithm.

Zhang, Haiying; Ran, Qiwen; Xiao, Yu; Ma, Jing; Tan, Liying; Zhang, Jin; Wei, Deyun

2009-07-01

128

Gaseous effluent monitoring and identification using an imaging Fourier transform spectrometer  

SciTech Connect

We are developing an imaging Fourier transform spectrometer for chemical effluent monitoring. The system consists of a 2-D infrared imaging array in the focal plane of a Michelson interferometer. Individual images are coordinated with the positioning of a moving mirror in the Michelson interferometer. A three dimensional data cube with two spatial dimensions and one interferogram dimension is then Fourier transformed to produce a hyperspectral data cube with one spectral dimension and two spatial dimensions. The spectral range of the instrument is determined by the choice of optical components and the spectral range of the focal plane array. Measurements in the near UV, visible, near IR, and mid-IR ranges are possible with the existing instrument. Gaseous effluent monitoring and identification measurements will be primarily in the ``fingerprint`` region of the spectrum, ({lambda} = 8 to 12 {mu}m). Initial measurements of effluent using this imaging interferometer in the mid-IR will be presented.

Carter, M.R.; Bennett, C.L.; Fields, D.J.; Hernandez, J.

1993-10-01

129

Creating an extended focus image of a tilted object in Fourier digital holography.  

PubMed

We present a new method to numerically reconstruct images on a tilted plane by digital holography in Fourier configuration. The proposed technique is based on a quadratic deformation of spatial coordinates of the digital hologram. By this approach we demonstrate that it is possible to recover the extended focus image (EFI) of a tilted object in a single reconstruction step from the deformed hologram. PMID:19997283

Paturzo, Melania; Ferraro, Pietro

2009-10-26

130

Texture Image Retrieval: A Feature-Based Correspondence Method in Fourier Spectrum  

Microsoft Academic Search

\\u000a This paper presents an effective texture descriptor invariant to translation, scaling, and rotation for texture-based image\\u000a retrieval applications. The proposed texture descriptor is built taking the Fourier space of the image. In order to find the\\u000a best texture descriptor, a quantization scheme based on Lloyd’s technique is proposed. As frequency descriptors are not invariant\\u000a to all geometrical transformations as scaling

Célia A. Zorzo Barcelos; Márcio J. R. Ferreira; Mylene L. Rodrigues

2005-01-01

131

Single-channel color image encryption based on iterative fractional Fourier transform and chaos  

NASA Astrophysics Data System (ADS)

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.

Sui, Liansheng; Gao, Bo

2013-06-01

132

Extracting and compensating dispersion mismatch in ultrahigh-resolution Fourier domain OCT imaging of the retina  

PubMed Central

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.

Choi, WooJhon; Baumann, Bernhard; Swanson, Eric A.; Fujimoto, James G.

2012-01-01

133

Extracting and compensating dispersion mismatch in ultrahigh-resolution Fourier domain OCT imaging of the retina.  

PubMed

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

Choi, WooJhon; Baumann, Bernhard; Swanson, Eric A; Fujimoto, James G

2012-11-01

134

Evaluation of shape variability of stallion sperm heads by means of image analysis and Fourier descriptors.  

PubMed

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

Severa, L; Máchal, L; Svábová, L; Mamica, O

2009-12-16

135

Diffractive imaging analysis of large-aperture segmented telescope based on partial Fourier transform  

NASA Astrophysics Data System (ADS)

Large-aperture segmented primary mirror will be widely used in next-generation space-based and ground-based telescopes. The effects of intersegment gaps, obstructions, position and figure errors of segments, which are all involved in the pupil plane, on the image quality metric should be analyzed using diffractive imaging theory. Traditional Fast Fourier Transform (FFT) method is very time-consuming and costs a lot of memory especially in dealing with large pupil-sampling matrix. A Partial Fourier Transform (PFT) method is first proposed to substantially speed up the computation and reduce memory usage for diffractive imaging analysis. Diffraction effects of a 6-meter segmented mirror including 18 hexagonal segments are simulated and analyzed using PFT method. The influence of intersegment gaps and position errors of segments on Strehl ratio is quantitatively analyzed by computing the Point Spread Function (PSF). By comparing simulation results with theoretical results, the correctness and feasibility of PFT method is confirmed.

Dong, Bing; Qin, Shun; Hu, Xinqi

2013-09-01

136

Novel Algorithm for Polar and Spherical Fourier Analysis on Two and Three Dimensional Images  

NASA Astrophysics Data System (ADS)

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.

Yang, Zhuo; Kamata, Sei-Ichiro

137

[The meteorological satellite spectral image registration based on Fourier-Mellin transform].  

PubMed

The meteorological satellite spectral image is an effective tool for researches on meteorological science and environmental remote sensing science. Image registration is the basis for the application of the meteorological satellite spectral image data. In order to realize the registration of the satellite image and the template image, a new registration method based on the Fourier-Mellin transform is presented in this paper. Firstly, we use the global coastline vector map data to build a landmark template, which is a reference for the meteorological satellite spectral image registration. Secondly, we choose infrared sub-image of no cloud according to the cloud channel data, and extract the edges of the infrared image by Sobel operator. Finally, the affine transform model parameters between the landmark template and the satellite image are determined by the Fourier-Mellin transform, and thus the registration is realized. The proposed method is based on the curve matching in essence. It needs no feature point extraction, and can greatly simplify the process of registration. The experimental results using the infrared spectral data of the FY-2D meteorological satellite show that the method is robust and can reach a high speed and high accuracy. PMID:23705469

Wang, Liang; Liu, Rong; Zhang, Li; Duan, Fu-Qing; Lü, Ke

2013-03-01

138

Subcortical representation of non-Fourier image features.  

PubMed

A fundamental goal of visual neuroscience is to identify the neural pathways representing different image features. It is widely argued that the early stages of these pathways represent linear features of the visual scene and that the nonlinearities necessary to represent complex visual patterns are introduced later in cortex. We tested this by comparing the responses of subcortical and cortical neurons to interference patterns constructed by summing sinusoidal gratings. Although a linear mechanism can detect the component gratings, a nonlinear mechanism is required to detect an interference pattern resulting from their sum. Consistent with in vitro retinal ganglion cell recordings, we found that interference patterns are represented subcortically by cat LGN Y-cells, but not X-cells. Linear and nonlinear tuning properties of LGN Y-cells were then characterized and compared quantitatively with those of cortical area 18 neurons responsive to interference patterns. This comparison revealed a high degree of similarity between the two neural populations, including the following: (1) the representation of similar spatial frequencies in both their linear and nonlinear responses, (2) comparable orientation selectivity for the high spatial frequency carrier of interference patterns, and (3) the same difference in their temporal frequency selectivity for drifting gratings versus the envelope of interference patterns. The present findings demonstrate that the nonlinear subcortical Y-cell pathway represents complex visual patterns and likely underlies cortical responses to interference patterns. We suggest that linear and nonlinear mechanisms important for encoding visual scenes emerge in parallel through distinct pathways originating at the retina. PMID:20147527

Rosenberg, Ari; Husson, T Robert; Issa, Naoum P

2010-02-10

139

Cross-phase modulation imaging  

PubMed Central

We demonstrate a cross-phase modulation measurement technique based on the sensitive detection of modulation transfer in a pump-probe setup. By modulating the amplitude of the pump beam and spectrally analyzing the probe beam, we achieve a rapid, background-free measurement of nonlinear phase modulation using power levels acceptable in biological imaging. This measurement technique would allow the extension of widely employed phase microscopy methods to the nonlinear regime, providing intrinsic and universal nonlinear contrast for biological imaging.

Samineni, Prathyush; Li, Baolei; Wilson, Jesse W.; Warren, Warren S.; Fischer, Martin C.

2012-01-01

140

A Bayesian approach to Fourier Synthesis inverse problem with application in SAR imaging  

NASA Astrophysics Data System (ADS)

In this paper we propose a Bayesian approach to the ill-posed inverse problem of Fourier synthesis (FS) which consists in reconstructing a function from partial knowledge of its Fourier Transform (FT) with application in SAR (Synthetic Aperture Radar) imaging. The function to be estimated represents an image of the observed scene. Considering this observed scene is mainly composed of point sources, we propose to use a Generalized Gaussian (GG) prior model, and then the Maximum A posterior (MAP) estimator as the desired solution. In particular, we are interested in bi-static case of spotlight-mode SAR data. In a first step, we consider real valued reflectivities but we account for the complex value of the measured data. The relation between the Fourier transform of the measured data and the unknown scene reflectivity is modeled by a 2D spatial FT. The inverse problem becomes then a FS and depending on the geometry of the data acquisition, only the set of locations in the Fourier space are different. We give a detailed modeling of the data acquisition process that we simulated, then apply the proposed method on those synthetic data to measure its performances compared to some other classical methods. Finally, we demonstrate the performance of the method on experimental SAR data obtained in a collaborative work by ONERA.

Zhu, Sha; Mohammad-Djafari, Ali

2011-03-01

141

Boundary layer moisture retrieval from Indian Ocean METOC Imaging (IOMI) mission for geostationary imaging Fourier transform spectrometer (GIFTS)  

Microsoft Academic Search

The Navy Indian Ocean METOC Imaging (IOMI) mission for the Geostationary Imaging Fourier Transform Spectrometer (GIFTS) will begin in early 2006 for a period of five years. The IOMI-GIFTS will measure Earth's outgoing infrared radiation with spatial (~4 km), temporal (~half hour), and spectral (~0.625 cm-1) resolutions and spectral coverages from longwave (LW, 685 - 1150 cm-1) for temperature profiles

Jun Li; Hung-Lung Huang

2003-01-01

142

FOURIER TRANSFORM INFRARED VIBRATIONAL SPECTROSCOPIC IMAGING: Integrating Microscopy and Molecular Recognition *  

NASA Astrophysics Data System (ADS)

The recent development of Fourier transform infrared (FTIR) spectroscopic imaging has enhanced our capability to examine, on a microscopic scale, the spatial distribution of vibrational spectroscopic signatures of materials spanning the physical and biomedical disciplines. Recent activity in this emerging area has concentrated on instrumentation development, theoretical analyses to provide guidelines for imaging practice, novel data processing algorithms, and the introduction of the technique to new fields. To illustrate the impact and promise of this spectroscopic imaging methodology, we present fundamental principles of the technique in the context of FTIR spectroscopy and review new applications in various venues ranging from the physical chemistry of macromolecular systems to the detection of human disease.

Levin, Ira W.; Bhargava, Rohit

2005-05-01

143

Instrumental phase-based method for Fourier transform spectrometer measurements processing  

SciTech Connect

Phase correction is a critical procedure for most space-borne Fourier transform spectrometers (FTSs) whose accuracy (owing to often poor signal-to-noise ratio, SNR) can be jeopardized from many uncontrollable environmental conditions. This work considers the phase correction in an FTS working under significant temperature change during the measurement and affected by mechanical disturbances. The implemented method is based on the identification of an instrumental phase that is dependent on the interferometer temperature and on the extraction of a linear phase component through a least-squares approach. The use of an instrumental phase parameterized with the interferometer temperature eases the determination of the linear phase that can be extracted using only a narrow spectral region selected to be immune from disturbances. The procedure, in this way, is made robust against phase errors arising from instrumental effects, a key feature to reduce the disturbances through spectra averaging. The method was specifically developed for the Mars IR Mapper spectrometer, that was designed for operation onboard a rover on the Mars surface; the validation was performed using ground and in-flight measurements of the Fourier transform IR spectrometer planetary Fourier spectrometer, onboard the MarsExpress mission. The symmetrization has been exploited also for the spectra calibration, highlighting the issues deriving from the cases of relevant beamsplitter emission. The applicability of this procedure to other instruments is conditional to the presence in the spectra of at least one spectral region with a large SNR along with a negligible (or known) beamsplitter emission. For the PFS instrument, the processing of data with relevant beamsplitter emission has been performed exploiting the absorption carbon dioxide bands present in Martian spectra.

Saggin, Bortolino; Scaccabarozzi, Diego; Tarabini, Marco

2011-04-20

144

Instrumental phase-based method for Fourier transform spectrometer measurements processing.  

PubMed

Phase correction is a critical procedure for most space-borne Fourier transform spectrometers (FTSs) whose accuracy (owing to often poor signal-to-noise ratio, SNR) can be jeopardized from many uncontrollable environmental conditions. This work considers the phase correction in an FTS working under significant temperature change during the measurement and affected by mechanical disturbances. The implemented method is based on the identification of an instrumental phase that is dependent on the interferometer temperature and on the extraction of a linear phase component through a least-squares approach. The use of an instrumental phase parameterized with the interferometer temperature eases the determination of the linear phase that can be extracted using only a narrow spectral region selected to be immune from disturbances. The procedure, in this way, is made robust against phase errors arising from instrumental effects, a key feature to reduce the disturbances through spectra averaging. The method was specifically developed for the Mars IR Mapper spectrometer, that was designed for operation onboard a rover on the Mars surface; the validation was performed using ground and in-flight measurements of the Fourier transform IR spectrometer planetary Fourier spectrometer, onboard the MarsExpress mission. The symmetrization has been exploited also for the spectra calibration, highlighting the issues deriving from the cases of relevant beamsplitter emission. The applicability of this procedure to other instruments is conditional to the presence in the spectra of at least one spectral region with a large SNR along with a negligible (or known) beamsplitter emission. For the PFS instrument, the processing of data with relevant beamsplitter emission has been performed exploiting the absorption carbon dioxide bands present in Martian spectra. PMID:21509063

Saggin, Bortolino; Scaccabarozzi, Diego; Tarabini, Marco

2011-04-20

145

Identification of Earthquake Induced Damage Areas Using Fourier Transform and SPOT HRVIR Pan Images.  

PubMed

A devastating earthquake with a magnitude of Mw 7.4 occurred on the North Anatolian Fault Zone (NAFZ) of Turkey on August 17, 1999 at 00:01:39 UTC (3:01 a.m. local time). The aim of this study is to propose a new approach to automatically identify earthquake induced damage areas which can provide valuable information to support emergency response and recovery assessment procedures. This research was conducted in the Adapazari inner city, covering a 3 × 3 km area, where 11,373 buildings collapsed as a result of the earthquake. SPOT high resolution visible infrared (HRVIR) Pan images obtained before (25 June 1999) and after (4 October 1999) the earthquake were used in the study. Five steps were employed to conduct the research and these are: (i) geometric and radiometric correction of satellite images, (ii) Fast Fourier Transform (FFT) of pre- and post-earthquake images and filtering the images in frequency domain, (iii) generating difference image using Inverse Fast Fourier Transform (IFFT) pre- and post- earthquake images, (iv) application of level slicing to difference image to identify the earthquake-induced damages, (v) accuracy assessment of the method using ground truth obtained from a 1/5,000 scale damage map. The total accuracy obtained in the research is 80.19 %, illustrating that the proposed method can be successfully used to automatically identify earthquake-induced damage areas. PMID:22573966

Sertel, Elif

2009-03-03

146

Identification of Earthquake Induced Damage Areas Using Fourier Transform and SPOT HRVIR Pan Images  

PubMed Central

A devastating earthquake with a magnitude of Mw 7.4 occurred on the North Anatolian Fault Zone (NAFZ) of Turkey on August 17, 1999 at 00:01:39 UTC (3:01 a.m. local time). The aim of this study is to propose a new approach to automatically identify earthquake induced damage areas which can provide valuable information to support emergency response and recovery assessment procedures. This research was conducted in the Adapazari inner city, covering a 3 × 3 km area, where 11,373 buildings collapsed as a result of the earthquake. SPOT high resolution visible infrared (HRVIR) Pan images obtained before (25 June 1999) and after (4 October 1999) the earthquake were used in the study. Five steps were employed to conduct the research and these are: (i) geometric and radiometric correction of satellite images, (ii) Fast Fourier Transform (FFT) of pre- and post-earthquake images and filtering the images in frequency domain, (iii) generating difference image using Inverse Fast Fourier Transform (IFFT) pre- and post- earthquake images, (iv) application of level slicing to difference image to identify the earthquake-induced damages, (v) accuracy assessment of the method using ground truth obtained from a 1/5,000 scale damage map. The total accuracy obtained in the research is 80.19 %, illustrating that the proposed method can be successfully used to automatically identify earthquake-induced damage areas.

Sertel, Elif

2009-01-01

147

Data reconstructing for windowing broom Fourier transform imaging spectrometers based on multi-core techniques  

NASA Astrophysics Data System (ADS)

The windowing broom Fourier transform imaging spectrometer, based on space-time modulation, has the characteristics of high luminous flux, static interference part etc. However, the large amount of raw data and the data reconstruction increase the difficulty of the whole data processing and extend the computing time. In this paper, a parallel calculation algorithm for reconstruction of raw data is proposed. The proposed algorithm is achieved by using Task Parallel Library (TPL), which is provided by .NET framework, and a visualized processing system is further established. A set of data collected from a windowing broom Fourier transform imaging spectrometer is processed using both the proposed method and the ordinary serial algorithm. The scalability of this presented algorithm is verified by employing it on computers with different number of cores. The experimental results show that, compared to the serial algorithm, the proposed method can greatly speed up the processing with the same hardware condition, and it also has ideal scalability with different hardware.

Dong, Zhi-gang; Liao, Ning-fang; Qu, Liang; Lv, Hang

2013-08-01

148

Effect of the fringe visibility on spectrum SNR of Fourier transform imaging spectrometer  

NASA Astrophysics Data System (ADS)

The principle of Fourier transform spectrometer is based on the relationship of Fourier-Transform between interferogram and spectrum. The spectral information of Fourier transform imaging spectrometer (FTIS) reconstructed from raw interferogram by data processing. So there are two kinds of signal-to-noise ratio (SNR) to evaluate instrument performance, one regarding interferogram and the other regarding reconstructed spectrum. Because the raw interferogram is intuitive, the interferogram SNR is studied usually. On the contrary, the spectrum SNR is studied less because of the complexity of the data processing from interferogram to spectrum. The research about the effect of the interference fringe visibility on the spectrum SNR is especially few. This paper present a research work on the relations between the interference fringe visibility and the spectrum SNR. Firstly, the reduction of fringe visibility caused by imaging lens defocus was analyzed. Secondly, the changes of the average spectrum signal and noise caused by the reduction of fringe visibility were calculated. For average spectrum signal, the math deductions are done base on Fourier transform theory. The average noise with different input signal optic-electrons number are simulated. the results show that the average spectrum signal is directly proportional to the fringe visibility, and the effect of fringe visibility on the noise related to signal can be ignorable. Finally, In order to demonstrate above results, the imaging experiment was done with white-light source, using LASIS (Large aperture static imaging spectrometer) based on Sagnac Interferometer. The average spectrum SNRs under different fringe visibility are calculated and analyzed. The experimental results show that: the average spectrum SNRs increase from 42.7 to 62.4.along with the fringe visibility increasing from 0.5051 to 0.687. the reconstructed spectrum SNR is directly proportional to the fringe visibility. As a result, the interferogram fringe visibility can be used to estimate the reconstructed spectrum SNR, and evaluate the performance of FTIS before data processing.

Wang, Shuang; Bin, Xiangli; Jing, Juanjuan; Pi, Haifeng

2013-08-01

149

Imaging open-path Fourier transform infrared spectrometer for 3D cloud profiling  

Microsoft Academic Search

OPTRA and University of North Carolina are developing an imaging open-path Fourier transform infrared (I-OP-FTIR) spectrometer for 3D profiling of chemical and biological agent simulant plumes released into test ranges and chambers. An array of I-OP-FTIR instruments positioned around the perimeter of the test site, in concert with advanced spectroscopic algorithms, enables real time tomographic reconstruction of the plume. The

Julia Rentz Dupuis; David J. Mansur; Robert Vaillancourt; Thomas Evans; Elizabeth Schundler; Lori Todd; Kathleen Mottus

2008-01-01

150

Imaging Geostationary Fourier Transform Spectrometer-revolutionary tool for tropospheric chemistry  

Microsoft Academic Search

The Geostationary Imaging Fourier Transform Spectrometer (GIFTS) has been selected by the National Aeronautics and Space Administration (NASA) for its 2004 New Millennium Program mission. The GIFTS geophysical data products are derived from measurements of atmospheric thermal emission in 2 spectral bands: 685-1130 cm-1 and 1650-2250 cm-1, at high spectral resolution (up to 0.3 cm-1) on a 4-km spatial grid.

N. S. Pougatchev; W. L. Smith; F. W. Harrison; A. M. Larar; C. P. Rinsland; D. J. Jacob; I. Bey; B. D. Field; R. M. Yantosca; A. Huang; S. R. Nolf; S. V. Kireev

2001-01-01

151

3D spectral imaging with synchrotron Fourier transform infrared spectro-microtomography.  

PubMed

We report Fourier transform infrared spectro-microtomography, a nondestructive three-dimensional imaging approach that reveals the distribution of distinctive chemical compositions throughout an intact biological or materials sample. The method combines mid-infrared absorption contrast with computed tomographic data acquisition and reconstruction to enhance chemical and morphological localization by determining a complete infrared spectrum for every voxel (millions of spectra determined per sample). PMID:23913258

Martin, Michael C; Dabat-Blondeau, Charlotte; Unger, Miriam; Sedlmair, Julia; Parkinson, Dilworth Y; Bechtel, Hans A; Illman, Barbara; Castro, Jonathan M; Keiluweit, Marco; Buschke, David; Ogle, Brenda; Nasse, Michael J; Hirschmugl, Carol J

2013-08-04

152

Quantitative zonal differentiation of articular cartilage by microscopic magnetic resonance imaging, polarized light microscopy, and Fourier-transform infrared imaging.  

PubMed

This study aimed to synchronize the zonal differentiation of the full-thickness articular cartilage by three micro-imaging techniques, namely microscopic magnetic resonance imaging (µMRI), polarized light microscopy (PLM), and Fourier-transform infrared imaging (FTIRI). Eighteen cartilage-bone blocks from three canine humeral joints were imaged by: (a) µMRI T2 relaxation at 0° and 55° orientations in a 7 T magnetic field, (b) PLM optical retardation and azimuthal angle, and (c) FTIRI amide I and amide II anisotropies at 0° and 90° polarizations relative to the articular surface. In addition, µMRI T1 relaxation was imaged before and after the tissue being immersed in gadolinium (contrast agent) solution, to calculate the proteoglycan concentration. A set of previously established criteria in cartilage imaging was revised. The new criteria could simultaneously correlate the thicknesses of the three consecutive subtissue zones in articular cartilage among these imaging techniques. PMID:23533143

Lee, Ji Hyun; Xia, Yang

2013-03-27

153

Evaluation of Fourier transform coefficients for the diagnosis of rheumatoid arthritis from diffuse optical tomography images  

NASA Astrophysics Data System (ADS)

We apply the Fourier Transform to absorption and scattering coefficient images of proximal interphalangeal (PIP) joints and evaluate the performance of these coefficients as classifiers using receiver operator characteristic (ROC) curve analysis. We find 25 features that yield a Youden index over 0.7, 3 features that yield a Youden index over 0.8, and 1 feature that yields a Youden index over 0.9 (90.0% sensitivity and 100% specificity). In general, scattering coefficient images yield better one-dimensional classifiers compared to absorption coefficient images. Using features derived from scattering coefficient images we obtain an average Youden index of 0.58 +/- 0.16, and an average Youden index of 0.45 +/- 0.15 when using features from absorption coefficient images.

Montejo, Ludguier D.; Jia, Jingfei; Kim, Hyun K.; Hielscher, Andreas H.

2013-03-01

154

High-resolution diffusion imaging using phase-corrected segmented echo-planar imaging.  

PubMed

Diffusion magnetic resonance imaging (MRI) was performed with a high-resolution segmented echo-planar imaging technique, which provided images with substantially less susceptibility artifacts than images obtained with single-shot echo-planar imaging (EPI). Diffusion imaging performed with any multishot pulse sequence is inherently sensitive to motion artifacts and in order to reduce motion artifacts, the presented method utilizes navigator echo phase corrections, performed after a one-dimensional Fourier transform along the frequency-encoding direction. Navigator echo phases were fitted to a straight line prior to phase correction to avoid errors from internal motion. In vivo imaging was performed using electro cardiographic (ECG) triggering. Apparent diffusion coefficient (ADC) maps were calculated on a pixel-by-pixel basis using up to seven diffusion sensitivities, ranging from b = 0 to 1129 x 10(6) s/m(2). PMID:10930774

Brockstedt, S; Moore, J R; Thomsen, C; Holtås, S; Ståhlberg, F

2000-07-01

155

High-resolution retinal imaging using adaptive optics and Fourier-domain optical coherence tomography  

SciTech Connect

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.

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

156

Fourier-domain methodology for depth-selective photothermoacoustic imaging of tissue chromophores  

Microsoft Academic Search

.  Development of a novel photothermoacoustic (PTA) imaging \\u000a technique utilizing a frequency-modulated (chirped) optical excitation and \\u000a Fourier-domain methodology for depth-selective imaging of tissue \\u000a chromophores is presented. Use of frequency-domain signal detection rather \\u000a than short-pulse time-resolved measurements of pressure transients give an \\u000a advantage of higher SNR typical to coherent detection techniques. \\u000a Additionally, we introduce chirped optical excitation to generate linear \\u000a frequency modulated

S. A. Telenkov; A. Mandelis

2008-01-01

157

Phase-image-based content-addressable holographic data storage  

NASA Astrophysics Data System (ADS)

We propose and demonstrate the use of phase images for content-addressable holographic data storage. Use of binary phase-based data pages with 0 and ? phase changes, produces uniform spectral distribution at the Fourier plane. The absence of strong DC component at the Fourier plane and more intensity of higher order spatial frequencies facilitate better recording of higher spatial frequencies, and improves the discrimination capability of the content-addressable memory. This improves the results of the associative recall in a holographic memory system, and can give low number of false hits even for small search arguments. The phase-modulated pixels also provide an opportunity of subtraction among data pixels leading to better discrimination between similar data pages.

John, Renu; Joseph, Joby; Singh, Kehar

2004-03-01

158

Fourier Imaging Correlation Spectroscopy for Studies of Sub-Cellular Dynamics and Biomolecular Conformation Transition Pathways  

NASA Astrophysics Data System (ADS)

Novel high signal-to-noise spectroscopic experiments that probe the dynamics of fluorescently labeled macromolecules have the potential to reveal complex intracellular biochemical mechanisms, or the slow relaxations of soft matter systems. Fourier imaging correlation spectroscopy (FICS) is a phase-selective approach to fluorescence fluctuation spectroscopy that employs a unique route to elevate signal levels while acquiring detailed information about microscopic coordinate trajectories. In this talk, I will illustrate the broad applicability of this approach by discussing two recent studies. The anomalous sub-diffusive dynamics of mitochondria in budding yeast are characterized using FICS, and provide detailed, length-scale dependent information about the influence of specific cytoskeletal elements on the movements of this organelle. We find that non-equilibrium forces associated with actin polymerization lead to a 1.5-fold enhancement of the long-time mitochondrial diffusion coefficient, and a transient sub-diffusive temporal scaling of the mean-square displacement. These non-equilibrium dynamics are a predominant factor in driving mitochondrial transport. In another set of experiments, polarization-modulated FICS simultaneously captures information about the internal conformation fluctuations and molecular translational dynamics of the fluorescent protein DsRed. By implementing a four-point correlation analysis, we construct two-dimensional spectral densities and joint distribution functions that determine temporal correlations of center-of-mass and anisotropy coordinates over successive time intervals. These four-point functions reveal statistically meaningful transition pathways between different optical conformations of the DsRed protein. The FICS method is well suited to investigate the dynamics of a broad range of heterogeneous systems, which include the molecular motions of glass forming liquids.

Marcus, Andrew

2010-03-01

159

In vivo imaging of the rodent eye with swept source/Fourier domain OCT  

PubMed Central

Swept source/Fourier domain OCT is demonstrated for in vivo imaging of the rodent eye. Using commercial swept laser technology, we developed a prototype OCT imaging system for small animal ocular imaging operating in the 1050 nm wavelength range at an axial scan rate of 100 kHz with ~6 µm axial resolution. The high imaging speed enables volumetric imaging with high axial scan densities, measuring high flow velocities in vessels, and repeated volumetric imaging over time. The 1050 nm wavelength light provides increased penetration into tissue compared to standard commercial OCT systems at 850 nm. The long imaging range enables multiple operating modes for imaging the retina, posterior eye, as well as anterior eye and full eye length. A registration algorithm using orthogonally scanned OCT volumetric data sets which can correct motion on a per A-scan basis is applied to compensate motion and merge motion corrected volumetric data for enhanced OCT image quality. Ultrahigh speed swept source OCT is a promising technique for imaging the rodent eye, proving comprehensive information on the cornea, anterior segment, lens, vitreous, posterior segment, retina and choroid.

Liu, Jonathan J.; Grulkowski, Ireneusz; Kraus, Martin F.; Potsaid, Benjamin; Lu, Chen D.; Baumann, Bernhard; Duker, Jay S.; Hornegger, Joachim; Fujimoto, James G.

2013-01-01

160

Application of Fourier-space image-restoration techniques to turbulence compensation and sparse-aperture imaging  

NASA Astrophysics Data System (ADS)

Image reconstruction is important in any application in which the sensing apparatus or the intervening medium significantly corrupts the recorded data. Deconvolution processes are the oldest and best understood, and for many practical problems Fourier domain deconvolution is the method of choice because acceptable results can usually be obtained with a minimum of computational effort. This report describes two practical applications of the Fourier deconvolution process in which detailed knowledge of the system's instantaneous optical transfer function is effectively utilized. In the first example, speckle imagery is combined with wavefront-sensor data to produce diffraction-limited images of celestial objects; the results are shown to compare favorably with the output of a fully operational adaptive optics system, the second application involves a sparse-aperture collection system that could be incorporated into a lightweight space telescope; this discussion includes an assessment of the practical utility of sparse-aperture receivers in a realistic signal-to-noise environment.

Parenti, Ronald R.

1994-06-01

161

Automated segmentation of intramacular layers in Fourier domain optical coherence tomography structural images from normal subjects  

PubMed Central

Abstract. Segmentation of optical coherence tomography (OCT) cross-sectional structural images is important for assisting ophthalmologists in clinical decision making in terms of both diagnosis and treatment. We present an automatic approach for segmenting intramacular layers in Fourier domain optical coherence tomography (FD-OCT) images using a searching strategy based on locally weighted gradient extrema, coupled with an error-removing technique based on statistical error estimation. A two-step denoising preprocess in different directions is also employed to suppress random speckle noise while preserving the layer boundary as intact as possible. The algorithms are tested on the FD-OCT volume images obtained from four normal subjects, which successfully identify the boundaries of seven physiological layers, consistent with the results based on manual determination of macular OCT images.

Zhang, Xusheng; Yousefi, Siavash; An, Lin; Wang, Ruikang K.

2012-01-01

162

Rotating point spread function in spiral phase contrast imaging with discrete phase modulation  

NASA Astrophysics Data System (ADS)

Spiral phase contrast imaging is one of the modern methods of optical microscopy applicable to edge contrast enhancement of amplitude and phase samples. The method is based on a spatial spectrum filtering realized by a spiral phase element at the focal plane of the Fourier lens. In this paper, the results of a paraxial wave model of the spiral imaging are presented which allow to calculate the point spread function for real parameters of the spiral filtering and to analyze defocusing effects. A particular attention is given to the analysis of the spiral imaging implemented by a phase mask with a finite number of discrete phase levels. As the main result, a defocusing-induced rotation of the point spread function is discovered and analyzed in detail. Theoretical predictions are verified in experiments using a spatial light modulator for generation of the discrete spiral phase mask.

Baránek, M.; Bouchal, Z.

2012-01-01

163

Fourier analysis of blurred images for the measurement of the in-plane dynamics of MEMS  

NASA Astrophysics Data System (ADS)

The goal of this paper is to use FFT imaging techniques to measure in-plane resonances of MEMS devices from blurred microphotographs where the presence of resonance is not visually discernable. A method is presented for measuring the high-frequency (in the 10s-100s of kHz range) response characteristics of MEMS devices using only standard optical microscope cameras (15-30 Hz frame rate) and applying Fourier analysis of camera images of periodic patterns on the oscillating devices. In the frequency domain, in-plane blurring acts as a low pass filter, attenuating all frequency components, but preferentially attenuating the higher order harmonics. A theoretical formula for the blur-induced attenuation of the harmonics of Fourier series components is derived and it is shown that it follows a Bessel curve. The theoretical predictions were verified experimentally using a series of camera microphotographs of three different variations of an electro-thermally driven pad suspended on springs. The predicted attenuations of harmonics were observed and verified. The analysis of the measured attenuation was able to (1) determine in-plane resonant frequencies, (2) measure submicron motions and (3) characterize the nonlinear dynamics (modeled by the Duffing equation). The amplitude uncertainty of the FFT method for detecting in-plane resonant peaks at 75 kHz and 3.5 V was found to be ±0.027 µm using a single image and ±0.011 µm using an average of 10 images.

Ellerington, Neil; Bschaden, Ben; Hubbard, Ted; Kujath, Marek

2012-03-01

164

LGPS: Phase Based Image Quality Assessment Metric  

Microsoft Academic Search

Phase map of the images captures the most fundamental cognitive features and thus is widely used in various digital image processing tasks. In this paper, we propose the Log Gabor Phase Similarity (LGPS), a novel full reference image quality assessment metrics based on measuring of similarities between phases in log Gabor transform domain. Phase can capture any changes in image

Guangtao Zhai; Wenjun Zhang; Yi Xu; Weisi Lin

2007-01-01

165

Processing of medical images using real-time optical Fourier processing.  

PubMed

Optical image processing techniques are inherently fast in view of parallel processing. A self-adaptive optical Fourier processing system using photoinduced dichroism in a bacteriorhodopsin film was experimentally demonstrated for medical image processing. Application of this powerful analog all-optical interactive technique for cancer diagnostics is illustrated with two mammograms and a Pap smear. Microcalcification clusters buried in surrounding tissue showed up clearly in the processed image. By playing with one knob, which rotates the analyzer in the optical system, either the microcalcification clusters or the surrounding dense tissue can be selectively displayed. Bacteriorhodopsin films are stable up to 140 degrees C and environmentally friendly. As no interference is involved in the experiments, vibration isolation and even a coherent light source are not required. It may be possible to develop a low-cost rugged battery operated portable signal-enhancing magnifier. PMID:11213918

Panchangam, A; Sastry, K V; Rao, D V; DeCristofano, B S; Kimball, B R; Nakashima, M

2001-01-01

166

Fourier domain pump-probe optical coherence tomography imaging of Melanin  

PubMed Central

We report the development of a two-color Fourier domain Pump-Probe Optical Coherence Tomography (PPOCT) system. Tissue phantom experiments to characterize the system performance demonstrated imaging depths in excess of 725 ?m, nearly comparable to the base Optical Coherence Tomography system. PPOCT A-line rates were also demonstrated in excess of 1 kHz. The physical origin of the PPOCT signal was investigated with a series of experiments which revealed that the signal is a mixture of short and long lifetime component signals. The short lifetime component was attributed to transient absorption while the long lifetime component may be due to a mixture of transient absorption and thermal effects. Ex vivo images of porcine iris demonstrated the potential for imaging melanin in the eye, where cancer of the melanocytes is the most common form of eye cancer in adults.

Jacob, Desmond; Shelton, Ryan L.; Applegate, Brian E.

2010-01-01

167

Image reconstruction from nonuniformly spaced samples in Fourier domain optical coherence tomography  

NASA Astrophysics Data System (ADS)

In this work, we use inverse imaging for object reconstruction from nonuniformly-spaced samples in Fourier domain optical coherence tomography (FD-OCT). We first model the FD-OCT system with a linear system of equations, where the source power spectrum and the nonuniformly-spaced sample positions are represented accurately. Then, we reconstruct the object signal directly from the nonuniformly-spaced wavelength measurements. With the inverse imaging method, we directly estimate the 2D cross-sectional object image instead of a set of independent A-line signals. By using the Total Variation (TV) as a constraint in the optimization process, we reduce the noise in the 2D object estimation. Besides TV, object sparsity is also used as a regularization for the signal reconstruction in FD-OCT. Experimental results demonstrate the advantages of our method, as we compare it with other methods.

Ke, Jun; Zhu, Rui; Lam, Edmund Y.

2012-02-01

168

An image reconstruction method from Fourier data with uncertainties on the spatial frequencies  

NASA Astrophysics Data System (ADS)

In this paper the reconstruction of a two-dimensional image from a nonuniform sampling of its Fourier transform is considered, in the presence of uncertainties on the frequencies corresponding to the measured data. The problem therefore becomes a blind deconvolution, in which the unknowns are both the image to be reconstructed and the exact frequencies. The availability of information on the image and the frequencies allows to reformulate the problem as a constrained minimization of the least squares functional. A regularized solution of this optimization problem is achieved by early stopping an alternating minimization scheme. In particular, a gradient projection method is employed at each step to compute an inexact solution of the minimization subproblems. The resulting algorithm is applied on some numerical examples arising in a real-world astronomical application.

Cornelio, Anastasia; Bonettini, Silvia; Prato, Marco

2013-10-01

169

Comparison of phase-shifting techniques for in vivo full-range, high-speed Fourier-domain optical coherence tomography  

NASA Astrophysics Data System (ADS)

Single spectrometer-based complex conjugate artifact removal methods are evaluated for in vivo imaging with complementary metal-oxide semiconductor line scan camera based high-speed Fourier-domain optical coherence tomography (FD-OCT) at 100,000 axial scans per second. Performance of three different phase-shifting methods with the same OCT engine is evaluated using modified data acquisition schemes, depending on the requirements of each phase-shifting technique. The suppression ratio of complex conjugate artifact images using a paperboard is assessed for all tested methods. Several other characteristics, including a list of additional hardware requirements (beyond standard FD-OCT components) and data acquisition schemes for each of the methods is presented. In vivo full-range images of human fingerpad and nail are shown and compared with standard FD-OCT images. Additionally, a complex-conjugate-free human retinal volume acquired at the speed of 100,000 A-scans/s is presented.

Kim, Dae Yu; Werner, John S.; Zawadzki, Robert J.

2010-09-01

170

SITELLE: a wide-field imaging Fourier transform spectrometer for the Canada-France-Hawaii Telescope  

NASA Astrophysics Data System (ADS)

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.

Drissen, L.; Bernier, A.-P.; Rousseau-Nepton, L.; Alarie, A.; Robert, C.; Joncas, G.; Thibault, S.; Grandmont, F.

2010-07-01

171

The New Physical Optics Notebook: Tutorials in Fourier Optics.  

ERIC Educational Resources Information Center

|This is a textbook of Fourier optics for the classroom or self-study. Major topics included in the 38 chapters are: Huygens' principle and Fourier transforms; image formation; optical coherence theory; coherent imaging; image analysis; coherent noise; interferometry; holography; communication theory techniques; analog optical computing; phase

Reynolds, George O.; And Others

172

Assessment of fibre orientation in reinforced concrete using Fourier image transform.  

PubMed

In this study, ribbon-shaped amorphous cast-iron fibres were used to reinforce a concrete matrix. X-ray photographs have been taken to detect fibres in situ. Their orientation has been investigated by automatic image analysis methods. However, this measurement should not be influenced by the digitization on the square frame of the analyser. For that purpose, the Fourier transform was used rather than the rose of direction method. This analysis revealed the transverse isotropic nature of the spatial arrangement of these fibres, whose axis of revolution corresponds to the concrete casting axis. Such a morphological characterization of the fibre-reinforced concrete reveals its mechanical behaviour. PMID:9767490

Redon; Chermant; Chermant; Coster

1998-09-01

173

Comparison of forward models and phase retrieval for image formation from intensity interferometer data  

NASA Astrophysics Data System (ADS)

Many imaging techniques provide measurements proportional to Fourier magnitudes of an object, from which one attempts to form an image. One such technique is intensity interferometry which measures the squared Fourier modulus. Intensity interferometry is a synthetic aperture approach known to obtain high spatial resolution information, and is effectively insensitive to degradations from atmospheric turbulence. These benefits are offset by an intrinsically low signal-to-noise (SNR) ratio. Forward models have been theoretically shown to have best performance for many imaging approaches. On the other hand, phase retrieval is designed to reconstruct an image from Fourier-plane magnitudes and object-plane constraints. So it's natural to ask, "How well does phase retrieval perform compared to forward models in cases of interest?" Image reconstructions are presented for both techniques in the presence of significant noise. Preliminary conclusions are presented for attainable resolution vs. DC SNR.

Gerwe, David; Crabtree, Peter; Holmes, Richard; Dolne, Jean

2013-09-01

174

The wide-field Fourier spectroscopic-imaging of the radiation heat from the object itself in the middle infrared region for the health monitoring  

NASA Astrophysics Data System (ADS)

We are aiming at the realization of the wide-field spectroscopic-imaging-sensor that is available for the health monitoring or the plant factory. Conventionally, the body temperature is measured by the thermography as a total intensity of the middle infrared radiation. We are trying to analyze the spectroscopic characteristics of the radiation heat from the human body in detail to measure the blood glucose or the moisture-retaining properties of the human skin. The proposed imaging-type 2-dimensional Fourier spectroscopy can measure the radiation heat from the object itself with the wide field of view and the wide wavelength-band. In this proposed method, we install the phase-shifter on the optical Fourier-transform-plane of the imaging optics to give the arbitrary phase-shift to the half flux of the object beams. Thus, the interferogram can be formed on the imaging plane in each bright point by the phase-shift interference-phenomena between the object beams that are emitted from the each corresponding bright point on the objective surface. In this report, we mention the feasibility results of the wide-field spectroscopic-imaging using the black body for the basic optical evaluation and the house plants for measuring the glucose distribution with the infrared camera(wavelength: 8?m-14?m).

Qi, Wei; Takuma, Takashi; Inui, Asuka; Tsutsumi, Ryosuke; Yuzuriha, Takehiko; Kagiyama, Hiroyasu; Kojima, Daisuke; Nishiyama, Akira; Ishimaru, Ichirou

2012-02-01

175

Fourier transform infared spectroscopic imaging for the identification of concealed drug residue particles and fingerprints  

NASA Astrophysics Data System (ADS)

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.

Ricci, Camilla; Chan, K. L. Andrew; Kazarian, Sergei G.

2006-10-01

176

Functional imaging of hemodynamic stimulus response in the rat retina with ultrahigh-speed spectral / Fourier domain OCT  

NASA Astrophysics Data System (ADS)

Measuring retinal hemodynamics in response to flicker stimulus is important for investigating pathophysiology in small animal models of diabetic retinopathy, because a reduction in the hyperemic response is thought to be one of the earliest changes in diabetic retinopathy. In this study, we investigated functional imaging of retinal hemodynamics in response to flicker stimulus in the rat retina using an ultrahigh speed spectral / Fourier domain OCT system at 840nm with an axial scan rate of 244kHz. At 244kHz the nominal axial velocity range that could be measured without phase wrapping was +/-37.7mm/s. Pulsatile total retinal arterial blood flow as a function of time was measured using an en face Doppler approach where a 200?m × 200?m area centered at the central retinal artery was repeatedly raster scanned at a volume acquisition rate of 55Hz. Three-dimensional capillary imaging was performed using speckle decorrelation which has minimal angle dependency compared to other angiography techniques based on OCT phase information. During OCT imaging, a flicker stimulus could be applied to the retina synchronously by inserting a dichroic mirror in the imaging interface. An acute transient increase in total retinal blood flow could be detected. At the capillary level, an increase in the degree of speckle decorrelation in capillary OCT angiography images could also be observed, which indicates an increase in the velocity of blood at the capillary level. This method promises to be useful for the investigation of small animal models of ocular diseases.

Choi, WooJhon; Baumann, Bernhard; Clermont, Allen C.; Feener, Edward P.; Boas, David A.; Fujimoto, James G.

2013-03-01

177

Calibration and correction of the CCD spectral response nonuniformity for Fourier transform imaging spectrometer  

NASA Astrophysics Data System (ADS)

Due to the manufacturing technique, some kinds of CCD, such as the back illuminated CCD, have the problem of spectral response nonuniformity. The near infrared light passing through the substrate and gates and is reflected back into the substrate for a second pass resulting in increased response. For the Fourier transform imaging spectrometer, it adds stripe pattern error to the interferogram and distorts the reconstructed spectrum. The nonuniform response is wavelength dependent due to changes in reflectivity of metal and the cavity formed by silicon and metal with transparent dielectric, so it adds difficulty to the correction of the error of the reconstructed spectrum. In order to reduce the error of the reconstructed spectrum, in this paper, a calibration method and a correction method to correct the error caused by the CCD spectral response nonuniformity was developed, basing on analysis of the property of the CCD spectral response nonuniformity. Firstly, a calibrated monochromater was used to measure the CCD spectral response nonuniformity and the property and affect of the CCD spectral response nonuniformity were analyzed. Method to correct the error of the reconstructed spectrum caused by the stripe pattern error was developed. Secondly, to calibrate the CCD spectral response nonuniformity, the spectral response coefficient and the spatial response nonuniformity coefficient was measured and computed. Finally, we took data with a Fourier transform imaging spectrometer, and got the correction results of the reconstructed spectrums. The results showed that the distortion of recovered spectrum was evidently reduced and the effect of the calibration and correction method was proved.

Shi, Dalian; Liu, Xuebin; Wang, Shuang; Jing, Juanjuan; Wen, Desheng; Bai, Qinglan

2013-08-01

178

Real-time Fourier transform spectrometry for fluorescence imaging and flow cytometry  

SciTech Connect

We present a Fourier transform (FT) spectrometer that is suitable for real-time spectral analysis in fluorescence imaging and flow cytometry. The instrument consists of a novel type of interferometer that can be modulated at frequencies of up to 100 kHz and has a high light throughput; and a dedicated, parallel array processor for the real-time computation of spectral parameters. The data acquisition array processor can be programmed by a host computer to perform any desired linear transform on the interferogram and can thus separate contributions from multiple fluorescence microscopy. The integration of a flow cytometer and a spectral imaging fluorescence microscope is discussed, and the concepts of direct and reversed virtual sorting'' are introduced. 9 refs., 8 figs.

Buican, T.N.

1990-01-01

179

Application of Fourier transform-second-harmonic generation imaging to the rat cervix.  

PubMed

We present the application of Fourier transform-second-harmonic generation (FT-SHG) imaging to evaluate the arrangement of collagen fibers in five nonpregnant rat cervices. Tissue slices from the mid-cervix and near the external orifice of the cervix were analyzed in both two-dimensions (2D) and three-dimensions (3D). We validate that the cervical microstructure can be quantitatively assessed in three dimensions using FT-SHG imaging and observe collagen fibers oriented both in and out-of-plane in the outermost and the innermost layers, which cannot be observed using 2D FT-SHG analysis alone. This approach has the potential to be a clinically applicable method for measuring progressive changes in collagen organization during cervical remodeling in humans. PMID:23600456

Lau, T Y; Sangha, H K; Chien, E K; McFarlin, B L; Wagoner Johnson, A J; Toussaint, K C

2013-04-19

180

4D imaging of embryonic chick hearts by streak-mode Fourier domain optical coherence tomography  

NASA Astrophysics Data System (ADS)

Recently, we developed the streak-mode Fourier domain optical coherence tomography (OCT) technique in which an area-scan camera is used in a streak-mode to record the OCT spectrum. Here we report the application of this technique to in ovo imaging HH18 embryonic chick hearts with an ultrahigh speed of 1,016,000 axial scans per second. The high-scan rate enables the acquisition of high temporal resolution 2D datasets (1,000 frames per second or 1 ms between frames) and 3D datasets (10 volumes per second), without use of prospective or retrospective gating technique. This marks the first time that the embryonic animal heart has been 4D imaged using a megahertz OCT.

Wang, Rui; Yun, Julie X.; Goodwin, Richard; Markwald, Roger; Borg, Thomas K.; Runyan, Raymond B.; Gao, Bruce

2012-02-01

181

A Novel Gradient Projection Approach for Fourier-Based Image Restoration  

SciTech Connect

This work deals with the ill-posed inverse problem of reconstructing a two-dimensional image of an unknown object starting from sparse and nonuniform measurements of its Fourier Transform. In particular, if we consider a priori information about the target image (e.g., the nonnegativity of the pixels), this inverse problem can be reformulated as a constrained optimization problem, in which the stationary points of the objective function can be viewed as the solutions of a deconvolution problem with a suitable kernel. We propose a fast and effective gradient-projection iterative algorithm to provide regularized solutions of such a deconvolution problem by early stopping the iterations. Preliminary results on a real-world application in astronomy are presented.

Bonettini, S. [Dipartimento di Matematica, Universita di Ferrara, Via Saragat 1, 44122 Ferrara (Italy); Prato, M. [Dipartimento di Matematica, Universita di Modena e Reggio Emilia, Via Campi 213/b, 41125 Modena (Italy); CNR-SPIN, Via Dodecaneso 33, 16146 Genova (Italy)

2010-09-30

182

A dynamically aligned step scanning mechanism for an imaging Fourier transform spectrometer for astronomy  

NASA Astrophysics Data System (ADS)

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.

Landry, Jean-Thomas; Grandmont, Frédéric

2006-07-01

183

Fourier Monte Carlo simulation of crystalline membranes in the flat phase  

NASA Astrophysics Data System (ADS)

Stimulated by the recent interest in graphene, the elastic behavior of crystalline membranes continues to be under debate. In their flat phase, one observes scaling of the correlation functions of in-plane and out-of-plane deformations u(x) and f(x) at long wavelengths with respect to a given reference plane governed by a single universal exponent ?. The purpose of the present article is to explain the ideas and techniques underlying our Fourier Monte Carlo simulation approach to the numerical determination of ? in much greater detail than was possible in a recent letter that is currently under review. Our simulations are based on an effective Hamiltonian first derived by Nelson and Peliti formulated exclusively in terms of the Fourier amplitudes tilde f(q) of the field f(x), and we calculate the out-of-plane correlation function langle|tilde f(q)|2rangle = tilde G(q) and their related mean squared displacement langle(?f)2rangle. The key to the progress reported in this work is the observation that on tuning the Monte Carlo acceptance rates separately for each wave vector, we are able to eliminate critical slowing down and thus achieve unprecedented statistical accuracy. A finite size scaling analysis for langle(?f)2rangle gives ? = 0.795(10). In the alternative approach, where we study the scaling of tilde G(q), we observe an unexpected anisotropic finite size effect at small wave vectors which hampers a similarly accurate numerical analysis.

Tröster, Andreas

2013-08-01

184

Optical image encryption with a bit-plane separation method in phase-shifting digital holography  

Microsoft Academic Search

In this paper, we propose a method for optical image encryption based on fractional Fourier transform (FRFT) and Arnold transform (ART) in phase-shifting digital holography. An input image is first divided into eight bit planes, and each bit plane is encrypted based on double random-phase masks and FRFT. Complex amplitude for the object is retrieved by phase-shifting digital holography in

Wen Chen; Chenggen Quan; Cho Jui Tay

2009-01-01

185

Lossless data compression studies for the geostationary imaging Fourier transform spectrometer (GIFTS) with the bias-adjusted reordering preprocessing  

Microsoft Academic Search

The NASA Geostationary Imaging Fourier Transform Spectrometer (GIFTS) represents a revolutionary step in remote sensing of Earth's atmosphere that will demonstrate the technology and measurement concepts for future NOAA geostationary operational environmental satellites (GOES). GIFTS consists of a 128 x 128 large focal plane array (LFPA) imaging FTS with the spectral coverage from 685 to 1130 cm-1 and 1650 to

Bormin Huang; Shih-Chieh Wei; Allen H.-L. Huang; Maciek Smuga-Otto; Robert Knuteson; Henry E. Revercomb; William L. Smith Sr.

2007-01-01

186

Optical design of a static LWIR Fourier-transform imaging spectrometer with high throughput  

NASA Astrophysics Data System (ADS)

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.

Wang, Hai-yang; Fu, Yan-peng; Zheng, Wei-jian; Liao, Ning-fang; Jin, Wei-qi

2013-08-01

187

Quantitative analysis of biological tissues using Fourier transform-second-harmonic generation imaging  

NASA Astrophysics Data System (ADS)

We demonstrate the use of Fourier transform-second-harmonic generation (FT-SHG) imaging of collagen fibers as a means of performing quantitative analysis of obtained images of selected spatial regions in porcine trachea, ear, and cornea. Two quantitative markers, preferred orientation and maximum spatial frequency are proposed for differentiating structural information between various spatial regions of interest in the specimens. The ear shows consistent maximum spatial frequency and orientation as also observed in its real-space image. However, there are observable changes in the orientation and minimum feature size of fibers in the trachea indicating a more random organization. Finally, the analysis is applied to a 3D image stack of the cornea. It is shown that the standard deviation of the orientation is sensitive to the randomness in fiber orientation. Regions with variations in the maximum spatial frequency, but with relatively constant orientation, suggest that maximum spatial frequency is useful as an independent quantitative marker. We emphasize that FT-SHG is a simple, yet powerful, tool for extracting information from images that is not obvious in real space. This technique can be used as a quantitative biomarker to assess the structure of collagen fibers that may change due to damage from disease or physical injury.

Ambekar Ramachandra Rao, Raghu; Mehta, Monal R.; Toussaint, Kimani C., Jr.

2010-02-01

188

Ultra-Rapid Categorization of Fourier-Spectrum Equalized Natural Images: Macaques and Humans Perform Similarly  

PubMed Central

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.

Girard, Pascal; Koenig-Robert, Roger

2011-01-01

189

Phase Determination for Intra-unit-cell Fourier Transform STM -- Picometer Registration of Zn Impurity States in Bi2Sr2CaCu2O8+?  

NASA Astrophysics Data System (ADS)

By studying the real and imaginary components of the Bragg peaks in Fourier transforms of electronic structure images, distinct types of intra-unit cell (IUC) symmetry breaking can be studied using SI-STM [Lawler et al., Nature 466 347 (2010)]. However, establishing the precise r-space symmetry point of each unit cell is crucial in defining the phase for such analysis. Exemplary of this challenge is the high-Tc superconductor Bi2Sr2CaCu2O8+? for which the Bi atoms in the surface BiO layer are observable, while it is the invisible Cu atoms that define the relevant CuO2 unit-cell symmetry point. We demonstrate, by imaging with pm precision the electronic impurity states at individual Zn atoms substituted at Cu sites, that the phase established using the Bi lattice produces a ˜2%(2?) error relative to the Cu lattice. In this case, IUC C4v symmetry breaking in the CuO2 plane can be determined reliably using the phase assignment from the BiO layer. Moreover, impurity atom substitution at the relevant symmetry site can be of general utility in phase determination for Bragg-peak Fourier analysis of IUC symmetry.

Firmo, Ines; Hamidian, Mohammad; Fujita, Kazuhiro; Mukhopadhyay, Sourin; Orenstein, Joseph; Eisaki, Hiroshi; Uchida, Shin-Ichi; Lawler, Michael; Kim, Eun-Ah; Davis, J. C.

2012-02-01

190

Image reconstruction from partial pseudo polar Fourier sampling based on alternating direction total variation minimization  

NASA Astrophysics Data System (ADS)

Linear scan Computed Tomography (LCT) has emerged as a promising technique in fields like industrial scanning and security inspection due to its straight-line source trajectory and high scanning speed. However, in practical applications of LCT, the ordinary algorithms suffer from serious artifacts owing to the limited-angle and insufficient data. In this paper, a new method which reconstructs image from partial Fourier data sampled in pseudo polar grid based on alternating direction anisometric total variation minimization has been proposed. The main idea is to reform the image reconstruction problem into solving an under-determined linear equation, and then reconstruct image by applying the popular total variation (TV) minimization to reform an unconstraint optimization by means of augmented Lagrange method and using the alternating minimization method of multiplier (ADMM) which contributes to the fast convergence. The proposed method is practical in the large-scale task of reconstruction due to its algorithmic simplicity and computational efficiency and reconstructs better images. The results of the numerical simulations and pseudo real data reconstructions from the linear scan validate that the proposed method is both efficient and accurate.

Liu, Qiu-hong; Shu, Fan; Zhang, Wen-kun; Cai, Ai-long; Li, Lei; Yan, Bin

2013-08-01

191

Combining the tape-lift method and Fourier transform infrared spectroscopic imaging for forensic applications.  

PubMed

Conventional Fourier transform infrared (FT-IR) spectroscopy and microscopy have been widely used in forensic science. New opportunities exist to obtain chemical images and to enhance the spatial resolution using attenuated total reflection (ATR) FT-IR spectroscopy coupled with a focal-plane array (FPA) detector. In this paper, the sensitivity limits of FT-IR imaging using three different ATR crystals (Ge, ZnSe, and diamond) in three different optical arrangements for the detection of model particles is discussed. Model systems of ibuprofen and paracetamol particles having sizes below 32 mum were studied. The collection of drug particles was achieved with the aid of two different tapes: common adhesive tape and a film of polydimethylsiloxane (PDMS). The surface of the film with collected particles was measured directly via ATR-FT-IR imaging. Since the removal of tape from porous surfaces can be difficult, the application of micro ATR-FT-IR imaging directly to the surface of a newspaper contaminated with particles of model drugs is also discussed. In order to assess the feasibility of the chosen method in a forensic case study, the detection of diacetylmorphine hydrochloride traces in PDMS matrix and the finger surface is investigated. The scenarios considered were that of the detection of evidence collected at a crime scene with the tape lift method and the analysis of the finger of an individual after drug handling. The results show broad implications in the detection of drugs of abuse. PMID:17002827

Ricci, Camilla; Chan, K L Andrew; Kazarian, Sergei G

2006-09-01

192

Evaluation of variation of root shape of Japanese radish (Raphanus sativus L.) based on image analysis using elliptic Fourier descriptors  

Microsoft Academic Search

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

Hiroyoshi Iwata; Satoshi Niikura; Seiji Matsuura; Yasushi Takano; Yasuo Ukai

1998-01-01

193

Fast 3D-ISAR Image Simulation of Targets at Arbitrary Aspect Angles Through Nonuniform Fast Fourier Transform (NUFFT)  

Microsoft Academic Search

We present a method to generate three-dimensional (3D) inverse synthetic aperture radar (ISAR) images of a target at arbitrary aspect angles using the shooting and bouncing ray (SBR) method. We have derived a 3D-image-domain ray-tube integration formula based on the SBR technique. The imaging formula is in a form of convolution, then a nonuniform fast Fourier transform (NUFFT) is induced

Xin Yi He; Xiao Yang Zhou; Tie Jun Cui

2012-01-01

194

Higher-dimensional phase imaging  

NASA Astrophysics Data System (ADS)

Traditional full-field interferometric techniques (speckle, moiré, holography etc) provide 2-D phase images, which encode the surface deformation state of the object under test. Over the past 15 years, the use of additional spatial or temporal dimensions has been investigated by a number of research groups. Early examples include the measurement of 3-D surface profiles by temporally-varying projected fringe patterns, and dynamic speckle interferometry. More recently (the past 5 years) a family of related techniques (Wavelength Scanning Interferometry, Phase Contrast Spectral Optical Coherence Tomography (OCT), and Tilt Scanning Interferometry) has emerged that provides the volume deformation state of the object. The techniques can be thought of as a marriage between the phase sensing capabilities of Phase Shifting Interferometry and the depth-sensing capabilities of OCT. Finally, in the past 12 months a technique called Hyperspectral Interferometry has been proposed in which absolute optical path distributions are obtained in a single shot through the spectral decomposition of a white light interferogram, and for which the additional dimension therefore corresponds to the illumination wavenumber. An overview of these developments, and the related issue of robust phase unwrapping of noisy 3-D wrapped phase volumes, is presented in this paper.

Huntley, Jonathan M.

2010-04-01

195

The use of the fractional Fourier transform with coded excitation in ultrasound imaging.  

PubMed

Medical ultrasound systems are limited by a tradeoff between axial resolution and the maximum imaging depth which may be achieved. The technique of coded excitation has been used extensively in the field of RADAR and SONAR for some time, but has only relatively recently been exploited in the area of medical ultrasound. This technique is attractive because allows the relationship between the pulse length and the maximum achievable spatial resolution to be changed. The work presented here explores the possibility of using the fractional Fourier transform as an effective means for the processing of signals received after the transmission of linear frequency modulated chirps. Results are presented which demonstrate that this technique is able to offer spatial resolutions similar to those obtained with a single cycle duration signal. PMID:16602583

Bennett, Michael J; McLaughlin, Steve; Anderson, Tom; McDicken, Norman

2006-04-01

196

Science results from the imaging Fourier transform spectrometer SpIOMM  

NASA Astrophysics Data System (ADS)

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.

Drissen, L.; Bernier, A.-P.; Charlebois, M.; Brière, É.; Robert, C.; Joncas, G.; Martin, P.; Grandmont, F.

2008-08-01

197

New scientific results with SpIOMM: a testbed for CFHT's imaging Fourier transform spectrometer SITELLE  

NASA Astrophysics Data System (ADS)

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.

Drissen, L.; Alarie, A.; Martin, T.; Lagrois, D.; Rousseau-Nepton, L.; Bilodeau, A.; Robert, C.; Joncas, G.; Iglesias-Páramo, J.

2012-09-01

198

Phase contrast radiography: Image modeling and optimization  

SciTech Connect

We consider image formation for the phase-contrast radiography technique where the radiation source is extended and spatially incoherent. A model is developed for this imaging process which allows us to define an objective filtering criterion that can be applied to the recovery of quantitative phase images from data obtained at different propagation distances. We test our image model with experimental x-ray data. We then apply our filter to experimental neutron phase radiography data and demonstrate improved image quality.

Arhatari, Benedicta D.; Mancuso, Adrian P.; Peele, Andrew G.; Nugent, Keith A. [School of Physics, University of Melbourne, Victoria 3010 (Australia)

2004-12-01

199

Image-quality assessment method for digital phase-contrast imaging based on two-dimensional power spectral analysis.  

PubMed

With use of the phase shift of X-rays that occurs when they pass through an object, phase-contrast imaging (herein referred to as "phase imaging") can produce images different from those of conventional contact imaging (herein referred to as "conventional imaging"). For this reason, assessment of the image quality based on noise-equivalent quanta (NEQ) and detective quantum efficiency (DQE) which does not include object-based information may not be appropriate for comparison of image quality between phase and conventional images. As an alternative method, we conceived a new image-quality assessment method with images that contain information about an object. First, we constructed images with an object and without an object under the same imaging parameters; then, we obtained two-dimensional power spectra by Fourier transform of those images. Second, we calculated the radial direction distribution function with the power spectra, and the distribution of signal intensity, which we defined as a signal intensity distribution function (SIDF). In this way, differences in image quality were evaluated relatively based on the SIDF of the imaged object. In our study, we first confirmed that phase-imaging evaluation was not appropriate by comparing NEQ and DQE of conventional, magnification, and phase imaging. Further, comparing the image quality of projected plant seeds by employing conventional, magnification, and phase imaging, we found that the phase-imaging method provided a higher image quality regarding edge sharpness than did conventional and magnification imaging. Therefore, based on these results, our image assessment method is considered useful for evaluation of images which include object-based information. PMID:22071600

Matsuo, Satoru; Morishita, Junji; Katafuchi, Tetsuro; Honda, Chika; Fujita, Hiroshi

2011-11-10

200

Securing information using fractional Fourier transform in digital holography  

NASA Astrophysics Data System (ADS)

In this paper, we demonstrate a fully digital technique using double random Fourier, and fractional plane encryption. The input image to be encrypted is multiplied by a phase mask, and either its Fourier or fractional Fourier transform is obtained. Using interference with a wave from another random phase mask, the encrypted data (Fourier or fractional hologram) is recorded digitally. The decryption key is also recorded as a digital hologram, called the key hologram. An electronic key generated in the PC is multiplied with the encrypted hologram, and a Fourier or fractional Fourier transform (encrypted image) is obtained. This decryption key hologram, the electronically generated key (random phase code), and the encrypted image can be transmitted through communication channels. The retrieval is carried out by all-digital means.

Kumar Nishchal, Naveen; Joseph, Joby; Singh, Kehar

2004-05-01

201

Picometer registration of zinc impurity states in Bi2Sr2CaCu2O8+? for phase determination in intra-unit-cell Fourier transform STM  

NASA Astrophysics Data System (ADS)

Direct visualization of electronic-structure symmetry within each crystalline unit cell is a new technique for complex electronic matter research (Lawler et al 2010 Nature 466 347-51, Schmidt et al 2011 New J. Phys. 13 065014, Fujita K et al 2012 J. Phys. Soc. Japan 81 011005). By studying the Bragg peaks in Fourier transforms of electronic structure images and particularly by resolving both the real and imaginary components of the Bragg amplitudes, distinct types of intra-unit-cell symmetry breaking can be studied. However, establishing the precise symmetry point of each unit cell in real space is crucial in defining the phase for such a Bragg-peak Fourier analysis. Exemplary of this challenge is the high-temperature superconductor Bi2Sr2CaCu2O8+? for which the surface Bi atom locations are observable, while it is the invisible Cu atoms that define the relevant CuO2 unit-cell symmetry point. Here we demonstrate, by imaging with picometer precision the electronic impurity states at individual Zn atoms substituted at Cu sites, that the phase established using the Bi lattice produces a ˜2%(2?) error relative to the actual Cu lattice. Such a phase assignment error would not diminish reliability in the determination of intra-unit-cell rotational symmetry breaking at the CuO2 plane (Lawler et al 2010 Nature 466 347-51, Schmidt et al 2011 New J. Phys. 13 065014, Fujita K et al 2012 J. Phys. Soc. Japan 81 011005). Moreover, this type of impurity atom substitution at the relevant symmetry site can be of general utility in phase determination for the Bragg-peak Fourier analysis of intra-unit-cell symmetry.

Hamidian, M. H.; Firmo, I. A.; Fujita, K.; Mukhopadhyay, S.; Orenstein, J. W.; Eisaki, H.; Uchida, S.; Lawler, M. J.; Kim, E.-A.; Davis, J. C.

2012-05-01

202

Sub-diffraction optical imaging by high-spatial-resolution photodetectors and Fourier signal processing  

NASA Astrophysics Data System (ADS)

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 across the sample. A far-field optical imaging instrument would thus be highly desirable. Optical imaging, however, is subject to the diffraction limit, which limits the size of the smallest resolvable feature to be ~ ?/2, where ? is the wavelength of the imaging light. Recently, negative-index materials and super lens have been proposed to overcome this limit and achieve high-resolution optical imaging [1-4]. In this paper, we propose a different approach to achieve sub-diffraction optical imaging with far-field microscopy. The technology builds on a high-spatial resolution quantum-dot (QD) photodetector with high sensitivity that we have demonstrated [5]. The photodetector consists of several nanocrystal QDs between a pair of electrodes with 50-nm width spaced ~ 25 nm apart. An optically effective area of 13515 nm2 was determined by modeling the electric field distribution in-between and around the electrodes using FEMLab. High-sensitivity photodetection has been demonstrated by measuring the tunneling photocurrent through the QDs, with a detection limit of 62 pW of the input optical power. The proposed sub-diffraction optical imaging system consists of an array of such photodetectors. We performed theoretical simulations assuming a two slit source and then pixilated the far-field diffraction pattern to simulate the photodetector array. A Fourier transform of the detector signal is then performed to determine how much of the original aperture information remains. Using a wavelength of 500 nm and a screen distance of 10 cm, we found that, as expected, the quality of the resultant image generally degraded with larger pixilation size. With 50-nm one-dimensional spatial resolution at the detection plane, it appears that the original slit image with 100-nm width and 300-nm spacing can still be restored.

Hashemi, Milad; Hegg, Michael; Parviz, Babak A.; Lin, Lih Y.

2008-01-01

203

A sapphire fibre thermal probe based on fast Fourier transform and phase-lock loop  

NASA Astrophysics Data System (ADS)

A sapphire fibre thermal probe with Cr3+ ion-doped end is developed by using the laser heated pedestal growth method. The fluorescence thermal probe offers advantages of compact structure, high performance and ability to withstand high temperature in a detection range from room temperature to 450°C. Based on the fast Fourier transform (FFT), the fluorescence lifetime is obtained from the tangent function of phase angle of the non-zeroth terms in the FFT result. This method has advantages such as quick calculation, high accuracy and immunity to the background noise. This FFT method is compared with other traditional fitting methods, indicating that the standard deviation of the FFT method is about half of that of the Prony method and about 1/6 of that of the log-fit method. And the FFT method is immune to the background noise involved in a signal. So, the FFT method is an excellent way of processing signals. In addition, a phase-lock amplifier can effectively suppress the noise.

Wang, Yu-Tian; Wang, Dong-Sheng; Ge, Wen-Qian; Cui, Li-Chao

2006-05-01

204

Effect of transmitting beam position error on the imaging quality of a Fourier telescope  

NASA Astrophysics Data System (ADS)

The effect of beam position error on the imaging quality of a Fourier telescope is analyzed in this paper. First, the origin of the transmitting beam position error and the error types are discussed. Second, a numerical analysis is performed. To focus on the transmitting beam position error, other noise sources exclusive of the reconstruction process are neglected. The Strehl ratio is set to be the objective function and the transfer function of the position error is constructed. Based on the numerical model, the features of Strehl ratio reduction caused by position error are deduced. Third, simulations are performed to study the position error effect on the imaging quality. A plot of the Strehl ratio versus the different levels of position errors is obtained and the simulation results validate the numerical model to a certain extent. According to the simulation results, a high value of the transmitting beam position error obviously degrades the imaging quality of the system; thus, it is essential to contain the position error within a relatively low level.

Zhou, Zhi-sheng; Bin, Xiang-Li; Zhang, Wen-xi; Li, Yang; Kong, Xin-xin; Lv, Xiao-yu

2013-09-01

205

Similarity measurement using polygon curve representation and Fourier descriptors for shape-based vertebral image retrieval  

NASA Astrophysics Data System (ADS)

Shape-based retrieval of vertebral x-ray images is a challenging task because of high similarity among the vertebral shapes. Most techniques, such as global shape properties or scale space filtering, lose or fail to detect local details. As the result of this shortfall, the number of retrieved images is so high that the retrieval result is sometimes meaningless. To retrieve a small number of best matched images, shape representation and similarity measurement techniques must distinguish shapes with minor variations. The main challenge of shape-based retrieval is to define a shape representation method that is invariant with respect to rotation, translation, scaling, and the curve starting point shift. In this research, a polygon curve evolution technique was developed for smoothing polygon curves and reducing the number of data points while preserving the significant pathology of the shape. The x and y coordinates of the simplified boundary points were then converted into a bend angle versus normalized curvature length function to represent the curve. Finally, the Fourier descriptors of the shape representation were calculated for similarity measurement. This approach meets the invariance requirements and has been proved to be efficient and accurate.

Lee, Dah-Jye; Antani, Sameer; Long, L. Rodney

2003-05-01

206

Research on methods of spectral calibration and radiometric calibration of the windowing Fourier transform imaging spectrometer  

NASA Astrophysics Data System (ADS)

Spectral calibration and radiometric calibration is an important part in the data processing of the windowing Fourier transform imaging spectrometer, it can ensure that the spectral curve output from spectrometer are more closely to target spectrum. The main idea of spectral calibration is using a monochromatic source whose wavelength is known, in the same way, radiometric calibration can be achieved by using radiation source whose radiation characteristic is known. In this paper, we propose a set of methods of spectral calibration and radiometric calibration. In order to carry out spectral calibration, we use monocharomator to scan several sample points near the position of every spectral channel of imaging spectrometer, and then we employ Gaussian fitting function to determine the central wavelength and bandwidth of every spectral channel. In order to carry out radiometric calibration, we employ panchromatic light source and integrating sphere, at the position of every spectral channel of imaging spectrometer, we measure the response ability of spectrometer to radiation. The calibration accuracy is carefully analyzed. Experimental results show that calibration accuracy meet the given requirements.

Zhang, Lei; Gao, Jiao Bo; Zhao, Yu Jie; Luo, Yan Ling; Xiao, Xiang Guo; Zhang, Fang

2013-08-01

207

Image-spectroscopy--II. The removal of plural scattering from extended energy-filtered series by Fourier deconvolution.  

PubMed

The increased spectral information obtained by acquiring an EFTEM image-series over several hundred eV allows plural scattering to be removed from loss images using standard deconvolution techniques developed for the quantification of EEL spectra. In this work, both Fourier-log and Fourier-ratio deconvolution techniques have been applied successfully to such image-series. Application of the Fourier-log technique over an energy-loss range of several hundred eV has been achieved by implementation of a novel method that extends the effective dynamic range of EFTEM image-series acquisition by over four orders of magnitude. Experimental results show that the removal of plural scattering from EFTEM image-series gives a significant improvement in quantification for thicker specimen regions. Further, the recovery of the single-scattering distribution using the Fourier-log technique over an extended energy-loss range is shown to result in an increase in both the ionisation-edge jump-ratio and the signal-to-noise ratio. PMID:11463197

Thomas, P J; Midgley, P A

2001-08-01

208

Osteochondral repair: evaluation with sweep imaging with fourier transform in an equine model.  

PubMed

Purpose: To evaluate the status of articular cartilage and bone in an equine model of spontaneous repair by using the sweep imaging with Fourier transform (SWIFT) magnetic resonance (MR) imaging technique. Materials and Methods: Experiments were approved by the Utrecht University Animal Ethics Committee. Six-millimeter-diameter chondral (n = 5) and osteochondral (n = 5, 3-4 mm deep into subchondral bone) defects were created in the intercarpal joints of seven 2-year-old horses and examined with SWIFT at 9.4 T after spontaneous healing for 12 months. Conventional T2 maps and gradient-echo images were obtained for comparison, and histologic assessment of cartilage and micro-computed tomography (CT) of bone were performed for reference. Signal-to-noise ratio (SNR) analysis was performed, and a radiologist evaluated the MR images. Structural bone parameters were derived from SWIFT and micro-CT datasets. Significance of differences was investigated with the Wilcoxon signed rank test and Pearson correlation analysis. Results: SWIFT was able to depict the different outcomes of spontaneous healing of focal chondral versus osteochondral defects. SWIFT produced constant signal intensity throughout cartilage, whereas T2 mapping showed elevated T2 values (P = .06) in repair tissue (mean T2 in superficial region of interest in an osteochondral lesion = 50.0 msec ± 10.2) in comparison to adjacent intact cartilage (mean T2 = 32.7 msec ± 4.2). The relative SNR in the subchondral plate with SWIFT (0.91) was more than four times higher than that with conventional fast spin-echo (0.12) and gradient-echo (0.19) MR imaging. The correlation between bone volume-to-tissue volume fractions determined with SWIFT and micro-CT was significant (r = 0.83, P < .01). Conclusion: SWIFT enabled assessment of spontaneous osteochondral repair in an equine model. © RSNA, 2013. PMID:23674789

Rautiainen, Jari; Lehto, Lauri J; Tiitu, Virpi; Kiekara, Outi; Pulkkinen, Hertta; Brünott, Anne; van Weeren, René; Brommer, Harold; Brama, Pieter A J; Ellermann, Jutta; Kiviranta, Ilkka; Nieminen, Miika T; Nissi, Mikko J

2013-05-14

209

Fourier phase analysis on equilibrium gated radionuclide ventriculography: Range of phase spread and cut-off limits in normal individuals  

PubMed Central

Aim: To define the range of phase spread on equilibrium gated radionuclide ventriculography (ERNV) in normal individuals and derive the cut-off limit for the parameters to detect cardiac dyssynchrony. Materials and Methods: ERNV was carried out in 30 individuals (age 53±23 years, 25 males and 5 females) who had no history of cardiovascular disease. They all had normal left ventricular ejection fraction (LVEF 55–70%) as determined by echocardiography, were in sinus rhythm, with normal QRS duration (?120 msec) and normal coronary angiography. First harmonic phase analysis was performed on scintigraphic data acquired in best septal view. Left and right ventricular standard deviation (LVSD and RVSD, respectively) and interventricular mechanical delay (IVMD), the absolute difference of mean phase angles of right and left ventricle, were computed and expressed in milliseconds. Mean + 3 standard deviation (SD) was used to derive the cut-off limits. Results: Average LVEF and duration of cardiac cycle in the study group were 62.5%±5.44% and 868.9±114.5 msec, respectively. The observations of LVSD, RVSD and right and left ventricular mean phase angles were shown to be normally distributed by Shapiro–Wilk test. Cut-off limits for LVSD, RVSD and IVMD were calculated to be 80 msec, 85 msec and 75 msec, respectively. Conclusion: Fourier phase analysis on ERNV is an effective tool for the evaluation of synchronicity of cardiac contraction. The cut-off limits of parameters of dyssynchrony can be used to separate heart failure patients with cardiac dyssynchrony from those without. ERNV can be used to select patients for cardiac resynchronization therapy.

Ramaiah, Vijayaraghavan L; Harish, B; Sunil, HV; Selvakumar, Job; Ravi, Kishore AG; Nair, Gopinathan

2011-01-01

210

The effect of pressure on the phase transition behavior of tridecane, pentadecane, and heptadecane: A Fourier transform infrared spectroscopy study  

Microsoft Academic Search

The effect of pressure on the phase transition behavior of tridecane (C13), pentadecane (C15), and heptadecane (C17) has been investigated up to 489, 220, and 387 MPa, respectively, using Fourier transform infrared spectroscopy at 25 °C. The transition between the high pressure ordered (HPO) and high pressure rotator (HPR) phases has been observed in the pressure ranges of 270-220, 106-95,

Motoi Yamashita; Atsushi Hirao; Minoru Kato

2011-01-01

211

Algorithm for three dimension reconstruction of magnetic resonance tomographs and X-ray images based on Fast Fourier Transform.  

National Technical Information Service (NTIS)

This work presents an algorithm for three-dimensional digital image reconstruction. Such algorithms based on the combination of both a Fast Fourier Transform method with Hamming Window and the use of a tri-linear interpolation function. The algorithm allo...

J. M. Bueno A. J. M. Traina P. E. Cruvinel

1995-01-01

212

Design and performance of a compact miniature static Fourier transform imaging spectropolarimeter  

NASA Astrophysics Data System (ADS)

We propose a compact, miniature static Fourier transform imaging spectropolarimeter (SFTISP). The spectropolarimeter is formed by cascading two high order crystal retarders and a Wollaston birefringent interferometer. Compared with previous instruments, the most significant advantage of the described model is that without any internal moving parts, electrically controllable or micro-components, the entire wavelength-dependent state of polarization (SOP) is acquired simultaneously along a one-dimensional spatial image by a single snapshot. Also, we show that in this configuration we can benefit from the advantages of the element: compact, robust and high throughput of the Wollaston birefringent interferometer. The theory of the birefringent SFTISP is provided, followed by details of its specific embodiment. A simulation and an experimental demonstration of the sensor are also presented. The core optics of the breadboard sensor is as small as 8×? 3.5 cm3 in size. The operation spectral range is from 450 nm to 850 nm. The experiment results were shown to yield accuracy better than 3% over most of the operation spectral band.

Li, Jie; Zhu, Jing-Ping; Wu, Hai-Ying; Hou, Xun

2011-06-01

213

Design considerations for the development of a space qualification Short Wavelength Imaging Fourier Transform Spectrometer (SWIFTS)  

SciTech Connect

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.

Abbink, R.E.

1997-06-01

214

Imaging open-path Fourier transform infrared spectrometer for 3D cloud profiling  

NASA Astrophysics Data System (ADS)

An imaging open-path Fourier transform infrared (I-OP-FTIR) spectrometer is being developed for real-time three-dimensional cloud profiling. The system employs a single modulator and a novel optical configuration which projects an array of angularly dispersed IR beams, each of which exhibits comparable throughput to a single channel OP-FTIR, to an array of respective retroreflector arrays remotely located at the opposite side of the test grid. The return light from each retroreflector array is imaged onto respective detectors that record the spatially-resolved interferograms which are subsequently transformed and analyzed for molecular content via advanced multicomponent algorithms. The result is a capability to sensitively, quantitatively, and simultaneously measure the molecular absorbance and associated concentration-pathlength of an open release plume over a spatial region. Use of two or more I-OP-FTIR sensors around the perimeter of the release allows for tomographic reconstruction of the concentration map of each molecular species contained in the plume. This approach realizes the high sensitivity of an OP-FTIR spectrometer without adding the expense and logistical difficulties associated with installing a large number of spectrometer units required for the cloud profiling application. In addition, the active spectral measurement supports detection in zero temperature contrast conditions where the plume is the same temperature as the background. A further reduction in cost and weight is achieved through the use of low-cost plastic press molded retroreflector arrays to return the spatially dispersed open path beams.

Dupuis, Julia R.; Mansur, David J.; Engel, James R.; Vaillancourt, Robert; Todd, Lori; Mottus, Kathleen

2007-10-01

215

Technical improvements and performances of SpIOMM: an imaging Fourier transform spectrometer for astronomy  

NASA Astrophysics Data System (ADS)

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.

Bernier, Anne-Pier; Charlebois, Maxime; Drissen, Laurent; Grandmont, Frédéric

2008-08-01

216

The study of a single BGC823 cell using Fourier transform infrared microspectroscopic imaging  

NASA Astrophysics Data System (ADS)

In order to investigate gastric cancer at cellular and sub-cellular level, a single human gastric adenocarcinoma BGC823 cell was studied by an infrared microscope equipped with a focal plane array (FPA) detector. The spectra showed difference between the nucleus and the endoplasmic reticulum (ER) of the BGC823 cell. The peak of v asPO 2- was shifted to a higher wavenumber at the nucleus compared with that at the ER. The height ratios of 2954 cm -1/2922 cm -1 (CH 3/CH 2) and 1088 cm -1/1539 cm -1 (DNA/amide II) of the nucleus were significantly higher than those of the ER. Furthermore, chemical images reveal the intensity distributions of lipids, proteins and DNA of the single BGC823 cell, and the intense absorptions of proteins and DNA were observed in the nuclear region of the cell while the intense absorption of lipids was found in the ER region of the cell. The Fourier transform infrared (FTIR) microspectroscopic imaging result indicates the study of the single gastric cancer cell at sub-cellular level can be beneficial for knowing gastric cancer more which will be of great importance for the study and diagnosis of gastric cancer. The result also suggests that FPA is a useful tool in the study of a single cell and may be a powerful tool for study and diagnosis of gastric cancer.

Wang, Xin; Qi, Zeming; Wang, Shengyi; Liu, Gang; Gao, Helong; Tian, Yangchao

2011-09-01

217

Ternary phase-amplitude modulation with twisted nematic liquid crystal displays for Fourier-plane light homogenization in holographic data storage  

NASA Astrophysics Data System (ADS)

Holographic data storage applications often use liquid crystal displays as spatial light-amplitude modulators for writing data images. The hologram created in the Fourier plane is usually applied to store the information, since this plane supplies optimal data density. A well known technique for homogenizing the light distribution in the Fourier plane is the application of external random phase modulating masks. The requirement for pixel by pixel matched positioning of the phase modulating mask and the pixels of the spatial light-amplitude modulator is hard to solve in the optical systems and any positioning error leads to significant signal degradations. The article analyses the possibilities of realizing the required simultaneous amplitude and phase modulation of light with the application of a single LCD. Twisted nematic LCDs with different maximal birefringence are numerically investigated using the Jones matrix method. Elliptical incident and exit polarizations are proposed, by which ternary phase-amplitude modulation (+1,-1,0) can be realized. Test measurements are also presented that demonstrate the validity of the calculated results.

Domjan, Laszlo; Koppa, Pal; Szarvas, Gabor; Remenyi, Judit

218

T2-weighted breathold imaging of the liver: a quantitative and qualitative comparison of fast spin echo and half Fourier single shot fast spin echo imaging.  

PubMed

The imaging characteristics of two EPI-hybrid breath-hold sequences, T2-weighted fast spin-echo [FSE, effective echo time (TEeff) 138 ms] and half Fourier single shot turbo spin-echo (HASTE, TEeff 60 ms), were compared in hepatic imaging. A total of 111 patients with suspected hepatic disease were studied at 1.5 Tesla using a body phase-array coil. The signal-to-noise (S/N) and contrast-to-noise (C/N) ratios for organs and lesions were calculated and quantitatively compared. Organ delineation, visualization of anatomical structures and pathological lesions, artifacts, and total image quality were qualitatively assessed and statistically compared. The final diagnoses were metastases from colorectal, breast, and pancreatic cancer in 23/111, hepatocellular carcinoma in 15/111, cysts in 19/111, hemangiomas in 9/111, several other lesions in 7/111, and no lesions in 38/111 of the cases. A total of 139 lesion in 73% of the patients were seen while 85% of the lesions were at least 1.5 cm in size. Regarding S/Ns HASTE was significantly (P < 0.03) superior to FSE with only minor (P > 0.05) differences in C/Ns between the two sequences for anatomical and pathological structures. HASTE demonstrated in almost all (97.3%) of the cases no artifacts, while on fast SE imaging moderate to minor artifacts were present in 23.5-51.7% of the cases. The overall image quality and diagnostic confidence was rated significantly higher (good 43.2%, excellent 53.2%) for HASTE than for fast SE imaging (good 44.8%, excellent 17.6%). Providing comparable C/Ns for anatomical and pathological structures, breatheld HASTE imaging proved to be superior to fast SE in T2-weighted imaging of the upper abdomen regarding general image quality, and, with adequate technical prerequisites, may be a suitable substitute of fast T2-imaging techniques. PMID:10555172

Helmberger, T K; Schröder, J; Holzknecht, N; Gregor, M; Heuck, A; Petsch, R; Reiser, M F

1999-10-01

219

Phase retrieval microscopy for quantitative phase-contrast imaging  

NASA Astrophysics Data System (ADS)

We present an approach for quantitative phase contrast imaging and optical metrology. This technique uses a CCD for in-line hologram recording and the phase retrieval algorithm for hologram reconstruction. The obtained phase distribution is equal, module 2[pi], to the phase distribution of the surface of the object. An application to surface profilometry is presented and good measurement result has been achieved.

Zhang, Y. A. N.; Pedrini, Giancarlo; Osten, Wolfgang; Tiziani, Hans J.

220

Phase retrieval microscopy for quantitative phase-contrast imaging  

Microsoft Academic Search

We present an approach for quantitative phase contrast imaging and optical metrology. This technique uses a CCD for in-line hologram recording and the phase retrieval algorithm for hologram reconstruction. The obtained phase distribution is equal, module 2[pi], to the phase distribution of the surface of the object. An application to surface profilometry is presented and good measurement result has been

Y. A. N. Zhang; Giancarlo Pedrini; Wolfgang Osten; Hans J. Tiziani

2004-01-01

221

Cryo-EM Image Alignment Based on Nonuniform Fast Fourier Transform  

PubMed Central

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.

Yang, Zhengfan; Penczek, Pawel A.

2008-01-01

222

Fourier Transform Infrared Spectroscopic Imaging and Multivariate Regression for Prediction of Proteoglycan Content of Articular Cartilage  

PubMed Central

Fourier Transform Infrared (FT-IR) spectroscopic imaging has been earlier applied for the spatial estimation of the collagen and the proteoglycan (PG) contents of articular cartilage (AC). However, earlier studies have been limited to the use of univariate analysis techniques. Current analysis methods lack the needed specificity for collagen and PGs. The aim of the present study was to evaluate the suitability of partial least squares regression (PLSR) and principal component regression (PCR) methods for the analysis of the PG content of AC. Multivariate regression models were compared with earlier used univariate methods and tested with a sample material consisting of healthy and enzymatically degraded steer AC. Chondroitinase ABC enzyme was used to increase the variation in PG content levels as compared to intact AC. Digital densitometric measurements of Safranin O –stained sections provided the reference for PG content. The results showed that multivariate regression models predict PG content of AC significantly better than earlier used absorbance spectrum (i.e. the area of carbohydrate region with or without amide I normalization) or second derivative spectrum univariate parameters. Increased molecular specificity favours the use of multivariate regression models, but they require more knowledge of chemometric analysis and extended laboratory resources for gathering reference data for establishing the models. When true molecular specificity is required, the multivariate models should be used.

Rieppo, Lassi; Rieppo, Jarno; Jurvelin, Jukka S.; Saarakkala, Simo

2012-01-01

223

Fourier Transform Infrared Imaging Analysis of Cancellous Bone in Alendronate- and Raloxifene-Treated Osteopenic Sheep  

PubMed Central

Fourier transform infrared imaging spectroscopy (FTIRI)-assessed bone composition parameters (mineral content, collagen maturity, crystal size and perfection, and carbonate content) describe bone quality and correlate to bone fracture risk. The challenge with studying bone quality in patients treated with antiresorptive drugs such as bisphosphonates (e.g., alendronate) and selective estrogen receptor modulators (SERMs) (e.g. raloxifene) is being able to test bone mechanical performance and material properties pre- and posttreatment. The purpose of this study was to evaluate the FTIRI changes in a large animal model of osteoporosis (female sheep with dietary induced metabolic acidosis; MA). Previous studies have investigated the relationship between bone material properties and bone strength in humans and smaller animals and have shown that changes in compositional properties influence fracture risk. Here we characterize the MA model at 6 and 12 months, demonstrate the loss of bone and changes in compositional properties, and show that 6 months of treatment with both antiresorptives ameliorate the bone loss as assessed by bone mineral density and FTIRI. This preliminary data suggest that the MA sheep model allows investigation of whether drug treatments preserve bone properties that exist at the time of treatment or if they induce further beneficial changes.

Calton, Ericka F.; MacLeay, Jennifer; Boskey, Adele L.

2011-01-01

224

Fourier transform infrared spectroscopic imaging of cardiac tissue to detect collagen deposition after myocardial infarction  

NASA Astrophysics Data System (ADS)

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.

Cheheltani, Rabee; Rosano, Jenna M.; Wang, Bin; Sabri, Abdel Karim; Pleshko, Nancy; Kiani, Mohammad F.

2012-05-01

225

Fourier transform infrared spectroscopic imaging of cardiac tissue to detect collagen deposition after myocardial infarction  

PubMed Central

Abstract. 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.

Cheheltani, Rabee; Rosano, Jenna M.; Wang, Bin; Sabri, Abdel Karim; Pleshko, Nancy; Kiani, Mohammad F.

2012-01-01

226

First results and current development of SpIOMM: an imaging Fourier transform spectrometer for astronomy  

NASA Astrophysics Data System (ADS)

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.

Bernier, A.-P.; Grandmont, F.; Rochon, J.-F.; Charlebois, M.; Drissen, L.

2006-07-01

227

Investigation of Moiré Pattern-based Phase Retrieval Approach for Differential Phase-contrast Cone Beam CT Imaging Using a Hospital-grade Tube.  

PubMed

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. PMID:23378889

Cai, Weixing; Ning, Ruola; Yu, Yang; Liu, Jiangkun; Conover, David

2012-02-23

228

Investigation of Moir? Pattern-based Phase Retrieval Approach for Differential Phase-contrast Cone Beam CT Imaging Using a Hospital-grade Tube  

PubMed Central

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.

Cai, Weixing; Ning, Ruola; Yu, Yang; Liu, Jiangkun; Conover, David

2012-01-01

229

A new anisotropy index on trabecular bone radiographic images using the fast Fourier transform  

PubMed Central

Background The degree of anisotropy (DA) on radiographs is related to bone structure, we present a new index to assess DA. Methods In a region of interest from calcaneus radiographs, we applied a Fast Fourier Transform (FFT). All the FFT spectra involve the horizontal and vertical components corresponding respectively to longitudinal and transversal trabeculae. By visual inspection, we measured the spreading angles: Dispersion Longitudinal Index (DLI) and Dispersion Transverse Index (DTI) and calculated DA = 180/(DLI+DTI). To test the reliability of DA assessment, we synthesized images simulating radiological projections of periodic structures with elements more or less disoriented. Results Firstly, we tested synthetic images which comprised a large variety of structures from highly anisotropic structure to the almost isotropic, DA was ranging from 1.3 to 3.8 respectively. The analysis of the FFT spectra was performed by two observers, the Coefficients of Variation were 1.5% and 3.1 % for intra-and inter-observer reproducibility, respectively. In 22 post-menopausal women with osteoporotic fracture cases and 44 age-matched controls, DA values were respectively 1.87 ± 0.15 versus 1.72 ± 0.18 (p = 0.001). From the ROC analysis, the Area Under Curve (AUC) were respectively 0.65, 0.62, 0.64, 0.77 for lumbar spine, femoral neck, total femoral BMD and DA. Conclusion The highest DA values in fracture cases suggest that the structure is more anisotropic in osteoporosis due to preferential deletion of trabeculae in some directions.

Brunet-Imbault, Barbara; Lemineur, Gerald; Chappard, Christine; Harba, Rachid; Benhamou, Claude-Laurent

2005-01-01

230

Digital holography forquantitative phase-contrast imaging  

Microsoft Academic Search

We present a new application of digital holography for phase-contrast imaging and optical metrology. This holographic imaging technique uses a CCD camera for recording of a digital Fresnel off-axis hologram and a numerical method for hologram reconstruction. The method simultaneously provides an amplitude-contrast image and a quantitative phase-contrast image. An application to surface profilometry is presented and shows excellent agreement

Etienne Cuche; Frédéric Bevilacqua; Christian Depeursinge

1999-01-01

231

Null test fourier domain alignment technique for phase-shifting point diffraction interferometer  

DOEpatents

Alignment technique for calibrating a phase-shifting point diffraction interferometer involves three independent steps where the first two steps independently align the image points and pinholes in rotation and separation to a fixed reference coordinate system, e.g, CCD. Once the two sub-elements have been properly aligned to the reference in two parameters (separation and orientation), the third step is to align the two sub-element coordinate systems to each other in the two remaining parameters (x,y) using standard methods of locating the pinholes relative to some easy to find reference point.

Naulleau, Patrick (5239 Miles Ave., Apt. A, Oakland, CA 94618); Goldberg, Kenneth Alan (1622 Oxford St., #5t, Berkeley, CA 94709)

2000-01-01

232

Phase Retrieval Using an Imaging Sensor.  

National Technical Information Service (NTIS)

This research study is concerned with spatial (relative) phase reconstruction using an imaging sensor. Specifically, work was completed which investigates the retrieval of the spatial phase of the aperture wavefront from sampled intensity data in the foca...

C. V. Scull

1979-01-01

233

Post-circular expansion of eccentric binary inspirals: Fourier-domain waveforms in the stationary phase approximation  

Microsoft Academic Search

We lay the foundations for the construction of analytic expressions for Fourier-domain gravitational waveforms produced by eccentric, inspiraling compact binaries in a post-circular or small-eccentricity approximation. The time-dependent, 'plus' and 'cross' polarizations are expanded in Bessel functions, which are then self-consistently reexpanded in a power series about zero initial eccentricity to eighth order. The stationary-phase approximation is then employed to

Nicolas Yunes; K. G. Arun; Emanuele Berti; Clifford M. Will

2009-01-01

234

Post-circular expansion of eccentric binary inspirals: Fourier-domain waveforms in the stationary phase approximation  

Microsoft Academic Search

We lay the foundations for the construction of analytic expressions for Fourier-domain gravitational waveforms produced by eccentric, inspiraling compact binaries in a post-circular or small-eccentricity approximation. The time-dependent, ``plus'' and ``cross'' polarizations are expanded in Bessel functions, which are then self-consistently reexpanded in a power series about zero initial eccentricity to eighth order. The stationary-phase approximation is then employed to

Nicolas Yunes; K. G. Arun; Emanuele Berti; Clifford M. Will

2009-01-01

235

Nonlinear phase interaction between nonstationary signals: A comparison study of methods based on Hilbert-Huang and Fourier transforms  

PubMed Central

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.

Novak, Vera; Peng, C.-K.; Liu, Yanhui

2009-01-01

236

Self-focusing media using graded photonic crystals: Focusing, Fourier transforming and imaging, directive emission, and directional cloaking  

NASA Astrophysics Data System (ADS)

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.

Vasi?, Borislav; Gaji?, Radoš

2011-09-01

237

Phase contrast neutron imaging of mixed phase-amplitude objects  

Microsoft Academic Search

A neutron imaging facility has been set up at the North Carolina State University (NCSU) PULSTAR reactor. Currently, work has started on tailoring the design of the facility to allow the performance of phase contrast neutron radiography. This is an imaging modality that has been extensively applied in X-ray imaging and was demonstrated using neutrons over the past few years.

Kaushal K. Mishra; Ayman I. Hawari

2007-01-01

238

Radiometric and spectral calibrations of the Geostationary Imaging Fourier Transform Spectrometer (GIFTS) using principle component analysis  

NASA Astrophysics Data System (ADS)

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.

Tian, Jialin; Smith, William L.; Gazarik, Michael J.

2008-10-01

239

Phase Space Imaging of Trapped Atoms Using Magnetic Sublevels Coherence  

NASA Astrophysics Data System (ADS)

We present our latest experimental data and analysis for a phase space imaging technique based on a grating of coherences between magnetic sublevels of an atomic ground state.(E.g. J.E. Thomas and L.J. Wang, Physics Reports 262), 311 (1995). We image a laser trapped atomic cloud which has been split in two with a laser pulse. The ``shearing effect'' of free evolution of such a system results in more complex phase space structures. In our experiment, two optical pulses drive Raman transitions between the sublevels and create a coherence grating in the cloud. Applying a weak readout pulse in the same mode as one of the excitation pulses, one sees a signal coherently radiated into the other mode. This can be done immediately after the excitation, the case of ``Magneto Grating Free Induction Decay'' (MGFID), or some time later, after rephasing the coherences by the second pair of pulses, the case of ``Magneto Grating Echo'' (MGE). In both cases the position-velocity distribution can be encoded in the signal frequency spectrum, if the sublevels are shifted by a position-dependent magnetic field. In the MGFID case the phase space image is then reconstructed from a set of projections. Alternatively, using the MGE technique, the image is obtained by two-dimensional Fourier transformation of the data.

Strekalov, D. V.; Turlapov, A. V.; Kumarakrishnan, A.; Cahn, S. B.; Sleator, Tycho

1998-05-01

240

A Fourier transform infrared study of the phase transition in aqueous solutions of Ethylene oxide–propylene oxide triblock copolymer  

Microsoft Academic Search

The phase transition between unimer and micellar phases of poly(ethylene oxide)–poly(propylene oxide)–poly(ethylene oxide)\\u000a (PEO–PPO–PEO) triblock copolymer Pluronic P105 in aqueous solution has been investigated as a function of temperature using\\u000a Fourier transform infrared spectroscopy. The transition of 8?wt% Pluronic P105 in aqueous solution was found to occur at 25?°C.\\u000a As temperature increases, PO blocks appear to be stretched conformers with

C. Guo; H.-Z. Liu; J.-Y. Chen

1999-01-01

241

Rugged high-speed rotary imaging Fourier transform spectrometer for industrial use  

NASA Astrophysics Data System (ADS)

A new rugged rotary Fourier Transform Spectrometer (FTS) has been developed. It can be used for environmental remote sensing and monitoring of chemical processes. Both single pixel and mosaic imaging configurations have been built and tested. The continuous rotary scan of the 'Turbo FT' allows operation without the laser reference of a conventional FTS, and it has been demonstrated to deliver 30 to 360 spectral scans per second and 1 cm-1 resolution, with excellent lineshape. A new 'space frame' version of the interferometer, with excellent mechanical and thermal stability, was field tested in both airborne and ground systems during the year 2000, with good results. The interferometer for this instrument is palm sized, and weighs 20 oz. It is totally sealed from the environment, and can be mounted, with its drive electronics, into a temperature stabilized enclosure for outside remote sensing applications For industrial applications, it can be used on-line or off-line, in conjunction with fiber optics, to measure and/or control multiple process lines. With the appropriate optics and detector set, the wavelength range can be adjusted from 1.0 to 25.0 micrometers. The resolution is variable from 1 to 8 cm-1. Various processors, data acquisition boards, and software have been used in the development, including the Labview package from National Instruments. Custom software for acquisition, display, and storage is being developed in summer 2001. The data acquisition system can be tailored for the speed and number of pixels required for the application. The current commercially available hardware being used can support up to 16 pixels at up to 100 scans per second.

Wadsworth, Winthrop; Dybwad, Jens-Peter

2002-02-01

242

Bone Quality determined by Fourier Transform Infrared Imaging Analysis in Mild Primary Hyperparathyroidism  

PubMed Central

Context: Mild primary hyperparathyroidism (PHPT) is characterized by asymptomatic hypercalcemia, most commonly in the absence of classical signs and symptoms. Hence, there is need to characterize this disorder with particular attention to the skeleton. Design: We determined the ratio of pyridinium and dehydrodihydroxylysinonorleucine collagen cross-links in 46 iliac crest bone biopsies from patients with PHPT (14 men, aged 28–68 yr; 32 women, aged 26–74 yr) by Fourier transform infrared imaging. The results were compared with previously reported collagen cross-links ratio determined in iliac crest biopsies from normal subjects. Results: PHPT patients exhibited significantly lower pyridinium to dehydrodihydroxylysinonorleucine collagen cross-links ratio, compared with normal controls. Parathyroidectomy restored values to those comparable with normal controls. Moreover, the differences among PHPT subjects were gender dependent, with female PHPT patients having a statistically significant lower ratio, compared with either male PHPT patients or normal controls. Comparison of the obtained outcomes with histomorphometry showed that the collagen cross-link ratio was strongly correlated with rate of bone formation, and mineralizing surface, in individual patients. This ratio was also correlated with bone mineralization density distribution parameters obtained in the same patients. The strongest correlations were with bone mineralization density distribution variables reflecting heterogeneity of mineralization and primary mineralization parameters. Conclusions: The results are consistent with the high turnover state manifested in PHPT patients. Reduced collagen cross-link ratio in patients with PHPT would be expected to reduce the stiffness of bone tissue. These observations provide a more complete assessment of bone material properties in this disorder.

Zoehrer, Ruth; Dempster, David W.; Bilezikian, John P.; Zhou, Hua; Silverberg, Shonni J.; Shane, Elizabeth; Roschger, Paul; Paschalis, Eleftherios P.; Klaushofer, Klaus

2008-01-01

243

Quantitative Phase Imaging Using Hard X Rays  

SciTech Connect

The quantitative imaging of a phase object using 16keV xrays is reported. The theoretical basis of the techniques is presented along with its implementation using a synchrotron x-ray source. We find that our phase image is in quantitative agreement with independent measurements of the object. {copyright} {ital 1996 The American Physical Society.}

Nugent, K.A.; Gureyev, T.E.; Cookson, D.J.; Paganin, D.; Barnea, Z. [School of Physics, The University of Melbourne, Parkville, Vic, 3052 (Australia)]|[Australian Nuclear Science and Technology Organization, Private Mail Bag 1, Menai, NSW, 2234 (Australia)

1996-09-01

244

A Signal Processing Approach to Fourier Analysis of Ranking Data: The Importance of Phase  

Microsoft Academic Search

Ranking data is a type of data obtained in some elections, in customer surveys, as well as from web search results. Such data may be considered as a type of signal defined on the group of permutations of objects, denoted . There exists a Fourier transform for obtained from group representation theory, which is well known in the mathematics literature.

Ramakrishna Kakarala

2011-01-01

245

Terahertz Fourier transform characterization of biological materials in a liquid phase  

Microsoft Academic Search

Significant progress has been achieved during the last several years relating to experimental and theoretical aspects of terahertz (or submillimetre wave) Fourier transform spectroscopy of biological macromolecules. However, previous research in this spectral range has been focused on bio-materials in solid state since it was common opinion that high water absorption will obscure the spectral signatures of the bio-molecules in

Tatiana Globus; Dwight Woolard; Thomas W. Crowe; Tatyana Khromova; Boris Gelmont; Jeffrey Hesler

2006-01-01

246

Phase Tomography Using Diffraction-Enhanced Imaging  

SciTech Connect

Phase tomography using diffraction-enhanced imaging (DEI) is presented with the observation of a phantom consisting of polyvinyl-chloride tubes and water. The boundary between the tube and water was successfully differentiated in a resultant tomographic image obtained with 0.06-nm synchrotron X rays. The sensitivity of this method is discussed in comparison with an image obtained by conventional X-ray tomography. The spatial and density resolutions achieved by the phase tomography are also discussed.

Koyama, I.; Momose, A. [Department of Advanced Materials Science, Graduate School of Frontier Sciences, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan); Hamaishi, Y. [Department of Applied Physics, School of Engineering, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656 (Japan)

2004-05-12

247

Tampering attacks on binary phase only filter-based watermarking schemes for image authentication  

NASA Astrophysics Data System (ADS)

Recently, a category of watermarking techniques based on binary phase-only filter (BPOF) has been proposed for image authentication. In such techniques, the authentication is implemented by evaluating the correlation between Fourier phase information and the hidden watermark bitplane. In this paper, we reveal the security flaws of BPOF-based watermarking algorithms and propose sophisticated tampering attacks against them. We show how the attacker can easily tamper with a watermarked image without being detected. Experimental results demonstrate that our attacks are successful in tampering watermarked images. The watermarking schemes are proven to be fundamentally flawed.

Cao, Gang; Zhao, Yao; Ni, Rongrong

2011-05-01

248

Amplitude-phase retrieval attack free cryptosystem based on direct attack to phase-truncated Fourier-transform-based encryption using a random amplitude mask.  

PubMed

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

Wang, Xiaogang; Zhao, Daomu

2013-09-15

249

Mitochondrial dynamics and optical conformation changes in DsRed as studied by Fourier imaging correlation spectroscopy  

NASA Astrophysics Data System (ADS)

Novel experiments that probe the dynamics of intracellular species, including the center-of-mass displacements and internal conformational transitions of biological macromolecules, have the potential to reveal the complex biochemical mechanisms operating within the cell. This work presents the implementation and development of Fourier imaging correlation spectroscopy (FICS), a phase-selective approach to fluorescence spectroscopy that measures the collective coordinate fluctuations of fluorescently labeled microscopic particles. In FICS experiments, a spatially modulated optical grating excites a fluorescently labeled sample. Phase-synchronous detection of the fluorescence, with respect to the phase of the exciting optical grating, can be used to monitor the fluctuations of partially averaged spatial coordinates. These data are then analyzed by two-point and four-point time correlation functions to provide a statistically meaningful understanding of the dynamics under observation. FICS represents a unique route to elevate signal levels, while acquiring detailed information about molecular coordinate trajectories. Mitochondria of mammalian cells are known to associate with cytoskeletal proteins, and their motions are affected by the stability of microtubules and microfilaments. Within the cell it is possible to fluorescently label the mitochondria and study its dynamic behavior with FICS. The dynamics of S. cerevisiae yeast mitochondria are characterized at four discrete length scales (ranging from 0.6--1.19 mum) and provide detailed information about the influence of specific cytoskeletal elements. Using the microtubule and microfilament destabilizing agents, Nocodazole and Latrunculin A, it is determined that microfilaments are required for normal yeast mitochondrial motion while microtubules have no effect. Experiments with specific actin mutants revealed that actin is responsible for enhanced mobility on length scales greater than 0.6 mum. The versatility of FICS expands when individual molecules are labeled with fluorescent chromophores. In recent experiments on the tetrameric fluorescent protein DsRed, polarization-modulated FICS (PM-FICS) is demonstrated to separate conformational dynamics from molecular translational dynamics. The optical switching pathways of DsRed, a tetrameric complex of fluorescent protein subunits, are examined. An analysis of PM-FICS coordinate trajectories, in terms of 2D spectra and joint probability distributions, provides detailed information about the transition pathways between distinct dipole-coupled DsRed conformations. This dissertation includes co-authored and previously published material.

Senning, Eric Nicolas

250

A 64-point Fourier transform chip for video motion compensation using phase correlation  

Microsoft Academic Search

Details of a new low power fast Fourier transform (FFT) processor for use in digital television applications are presented. This has been fabricated using a 0.6-?m CMOS technology and can perform a 64 point complex forward or inverse FFT on real-time video at up to 18 Megasamples per second. It comprises 0.5 million transistors in a die area of 7.8×8

Colin Chiu; Wing Hui; Tiong Jiu Ding; J. V. McCanny

1996-01-01

251

Amplified dispersive Fourier-transform imaging for ultrafast displacement sensing and barcode reading  

NASA Astrophysics Data System (ADS)

Dispersive Fourier transformation is a powerful technique in which the spectrum of an optical pulse is mapped into a time-domain waveform using chromatic dispersion. It replaces a diffraction grating and detector array with a dispersive fiber and single photodetector. This simplifies the system and, more importantly, enables fast real-time measurements. Here we describe a novel ultrafast barcode reader and displacement sensor that employs internally amplified dispersive Fourier transformation. This technique amplifies and simultaneously maps the spectrally encoded barcode into a temporal waveform. It achieves a record acquisition speed of 25 MHz-four orders of magnitude faster than the current state of the art.

Goda, Keisuke; Tsia, Kevin K.; Jalali, Bahram

2008-09-01

252

Traitement non linéaire d'images stéréo par corrélation de phase locale  

NASA Astrophysics Data System (ADS)

Dans cet article, nous décrivons une méthode pour reconstruire une carte des profondeurs à partir de deux images stéréoscopiques binoculaires. Cette méthode consiste à corréler successivement des zones extraites d'une des vues avec la seconde vue. Ces corrélations ont lieu dans le plan de Fourier et sont suivies d'un filtre utilisé classiquement pour la reconnaissance des formes: le SPOF (Symmetric Phase Only Filter). Ce filtre nous permet d'obtenir dans le plan de corrélation un pic de un pixel de large auquel s'ajoute un bruit gaussien centré dont la variance est déterminée par le choix des dimensions sur lesquelles nous effectuons les transformées de Fourier discrètes.

Paulin, C.; Taboury, J.; Chavel, P.

253

Cardiac gated equilibrium radionuclide angiography and multiharmonic Fourier phase analysis: Optimal acquisition parameters in arrhythmogenic right ventricular cardiomyopathy  

Microsoft Academic Search

Background  Multiharmonic Fourier phase analysis of radionuclide angiography is a well-established method for the diagnosis of arrhythmogenic\\u000a right ventricular cardiomyopathy. We sought to determine the optimal acquisition parameters: number of frames per cycle and\\u000a number of counts per frame, with all other acquisition and processing parameters being fixed.\\u000a \\u000a \\u000a \\u000a Methods and Results  Radionuclide angiography with list mode acquisition was performed in 10 normal

Doumit Daou; Rachida Lebtahi; Marc Faraggi; Yolande Petegnief; Dominique Le Guludec

1999-01-01

254

Fourier transform infrared measurement of solid-, liquid-, and gas-phase samples with a single photoacoustic cell.  

PubMed

A photoacoustic detector based on the optical cantilever microphone has been built. The detector is capable of measuring solid-, liquid-, and gas-phase samples. Photoacoustic Fourier transform infrared (FT-IR) measurement with three samples in different phases was demonstrated. Example samples were polyethene, sunflower oil, and methane. The sensitivity of the cell was compared to a commercial photoacoustic FT-IR detector. With the standard carbon black sample the cantilever detector gave approximately five times higher signal-to-noise ratio than the reference detector. The sensitivity with methane was also compared to the DTGS detector of the FT-IR instrument corresponding to an absorption path of 6.3 cm. Simulation of the photoacoustic signal showed that a compromise has to be made in the cell design between sensitivity for solid- and gas-phase samples but it is possible to highly enhance the sensitivity for all types of samples by reducing cantilever dimensions. PMID:18559153

Uotila, Juho; Kauppinen, Jyrki

2008-06-01

255

Amplified Dispersive FourierTransform Imaging for Ultrafast Displacement Sensing and Barcode Reading  

Microsoft Academic Search

Dispersive Fourier transformation is a powerful technique in which the spectrum of an optical pulse is mapped into a time-domain waveform using chromatic dispersion. It replaces a diffraction grating and detector array with a dispersive fiber and single photodetector. This simplifies the system and, more importantly, enables fast real-time measurements. Here we describe a novel ultrafast barcode reader and displacement

Keisuke God; Kevin K. Tsi; Bahram Jalali

256

Terahertz imaging with compressed sensing and phase retrieval  

Microsoft Academic Search

We describe a novel, high-speed pulsed terahertz (THz) Fourier imaging system based on compressed sens- ing (CS), a new signal processing theory, which allows image reconstruction with fewer samples than tra- ditionally required. Using CS, we successfully reconstruct a 6464 image of an object with pixel size 1.4 mm using a randomly chosen subset of the 4096 pixels, which defines

Wai Lam Chan; Matthew L. Moravec; Richard G. Baraniuk; Daniel M. Mittleman

2008-01-01

257

Phase contrast X-ray imaging  

Microsoft Academic Search

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

Byung Mook Weon; Jung Ho Je; Yeukuang Hwu

2006-01-01

258

Quantitative Phase Imaging in Scanning Optical Microscopy.  

NASA Astrophysics Data System (ADS)

The use of scanning optical microscopy for the purpose of quantitative phase imaging is theoretically and experimentally explored. In particular, several novel system configurations are presented and analyzed for their phase imaging capabilities. In these systems, absorptive filters are placed in the pupils of the microscope to encode object phase slope information into the image signal. With suitable processing and integration, the object phase profile is reconstructed. The phase imaging properties of the scanning optical microscopes are analyzed using a phase wedge model based on scalar diffraction theory. It is shown that the novel two-filter arrangement introduced in this thesis provides an unambiguous response to object phase slope. This permits a quantitative reconstruction of the object phase profile. In addition, the phase measurement is not affected by reflectance or transmittance variations in the object. Both confocal and conventional scanning microscopes are analyzed as a function of the pupil filter. Continuous absorptive filters and split-pupil filters are considered. It is shown that the absorptive pupil filter images twice the range of slopes of the split-pupil systems. In addition, the square root absorptive filter is shown to produce the most linear response for both the confocal and conventional scanning systems. The design, construction and operation of a reflection surface profiling instrument incorporating these phase imaging techniques are described. Measurements are performed with this instrument that confirm the validity of the phase wedge models used to analyze these systems. In addition, surface profile measurements of several samples are presented which demonstrate the operation of this instrument. Important advantages of these systems include the large range of slopes measured and the superior imaging properties of the confocal microscope. Furthermore, there is no restriction on the total extent of the phase variations present in the object. As long as the phase slope remains within the limit determined by the numerical aperture of the objective, the object phase profile can be accurately determined. Finally, these systems are able to image twice the range of slopes of previously reported coherent optical processing systems.

Kulawiec, Andrew William

259

Quantitative x-ray phase imaging at the nanoscale by multilayer Laue lenses  

PubMed Central

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.

Yan, Hanfei; Chu, Yong S.; Maser, Jorg; Nazaretski, Evgeny; Kim, Jungdae; Kang, Hyon Chol; Lombardo, Jeffrey J.; Chiu, Wilson K. S.

2013-01-01

260

Quantitative phase imaging using grating-based quadrature phase interferometer  

NASA Astrophysics Data System (ADS)

In this paper, we report the use of holographic gratings, which act as the free-space equivalent of the 3x3 fiber-optic coupler, to perform full field phase imaging. By recording two harmonically-related gratings in the same holographic plate, we are able to obtain nontrivial phase shift between different output ports of the gratings-based Mach-Zehnder interferometer. The phase difference can be adjusted by changing the relative phase of the recording beams when recording the hologram. We have built a Mach-Zehnder interferometer using harmonically-related holographic gratings with 600 and 1200 lines/mm spacing. Two CCD cameras at the output ports of the gratings-based Mach-Zehnder interferometer are used to record the full-field quadrature interferograms, which are subsequently processed to reconstruct the phase image. The imaging system has ~12X magnification with ~420µmx315µm field-of-view. To demonstrate the capability of our system, we have successfully performed phase imaging of a pure phase object and a paramecium caudatum.

Wu, Jigang; Yaqoob, Zahid; Heng, Xin; Cui, Xiquan; Yang, Changhuei

2007-03-01

261

Achromatic or quasi-color Fourier transform hologram and optical diffraction images  

NASA Astrophysics Data System (ADS)

A binary computer generated hologram (CGH) and a Fourier Transform hologram (FTH) with gray level/quasi-colors are similar to all appearance in the structure of hologram cell. However, they are wholly different in display techniques by the use of gray level or quasi-colors. It is possible to directly take a picture of reduced FTH, i.e., a kind of positive and negative transparency, displayed on a standard color LCD/CRT using a negative film with high contrast.

Iizuka, Masayuki; Ookuma, Yoshio; Nakashima, Yoshio

2001-06-01

262

Concentration Profiles of Collagen and Proteoglycan in Articular Cartilage by Fourier Transform Infrared Imaging and Principal Component Regression  

PubMed Central

Fourier-transform infrared imaging (FT-IRI) technique with the principal component regression (PCR) method was used to quantitatively determine the 2D images and the depth-dependent concentration profiles of two principal macromolecular components (collagen and proteoglycan) in articular cartilage. Ten 6 ?m thick sections of canine humeral cartilage were imaged at a pixel size of 6.25 ?m in FT-IRI. The infrared spectra extracted from FT-IRI experiments were imported into a PCR program to calculate the quantitative distributions of both collagen and proteoglycan in dry cartilage, which were subsequently converted into the wet-weight based concentration profiles. The proteoglycan profiles by FT-IRI and PCR significantly correlated in linear regression with the proteoglycan profiles by the non-destructive ?MRI (the goodness-of-fit 0.96 and the Pearson coefficient 0.98). Based on these concentration relationships, the concentration images of collagen and proteoglycan in both healthy and lesioned articular cartilage were successfully constructed two dimensionally. The simultaneous construction of both collagen and proteoglycan concentration images demonstrates that this combined imaging and chemometrics approach could be used as a sensitive tool to accurately resolve and visualize the concentration distributions of macromolecules in biological tissues.

Yin, Jianhua; Xia, Yang; Lu, Mei

2011-01-01

263

Concentration profiles of collagen and proteoglycan in articular cartilage by Fourier transform infrared imaging and principal component regression  

NASA Astrophysics Data System (ADS)

Fourier-transform infrared imaging (FT-IRI) technique with the principal component regression (PCR) method was used to quantitatively determine the 2D images and the depth-dependent concentration profiles of two principal macromolecular components (collagen and proteoglycan) in articular cartilage. Ten 6 ?m thick sections of canine humeral cartilage were imaged at a pixel size of 6.25 ?m in FT-IRI. The infrared spectra extracted from FT-IRI experiments were imported into a PCR program to calculate the quantitative distributions of both collagen and proteoglycan in dry cartilage, which were subsequently converted into the wet-weight based concentration profiles. The proteoglycan profiles by FT-IRI and PCR significantly correlated in linear regression with the proteoglycan profiles by the non-destructive ?MRI (the goodness-of-fit 0.96 and the Pearson coefficient 0.98). Based on these concentration relationships, the concentration images of collagen and proteoglycan in both healthy and lesioned articular cartilage were successfully constructed two dimensionally. The simultaneous construction of both collagen and proteoglycan concentration images demonstrates that this combined imaging and chemometrics approach could be used as a sensitive tool to accurately resolve and visualize the concentration distributions of macromolecules in biological tissues.

Yin, Jianhua; Xia, Yang; Lu, Mei

2012-03-01

264

Phase congruency assesses hyperspectral image quality  

NASA Astrophysics Data System (ADS)

Blind image quality assessment (QA) is a tough task especially for hyperspectral imagery which is degraded by noise, distortion, defocus, and other complex factors. Subjective hyperspectral imagery QA methods are basically measured the degradation of image from human perceptual visual quality. As the most important image quality measurement features, noise and blur, determined the image quality greatly, are employed to predict the objective hyperspectral imagery quality of each band. We demonstrate a novel no-reference hyperspectral imagery QA model based on phase congruency (PC), which is a dimensionless quantity and provides an absolute measure of the significance of feature point. First, Log Gabor wavelet is used to calculate the phase congruency of frequencies of each band image. The relationship between noise and PC can be derived from above transformation under the assumption that noise is additive. Second, PC focus measure evaluation model is proposed to evaluate blur caused by different amounts of defocus. The ratio and mean factors of edge blur level and noise is defined to assess the quality of each band image. This image QA method obtains excellent correlation with subjective image quality score without any reference. Finally, the PC information is utilized to improve the quality of some bands images.

Shao, Xiaopeng; Zhong, Cheng

2012-10-01

265

CONTROL OF LASER RADIATION PARAMETERS: Theory of laser array phase locking by Fourier coupling  

NASA Astrophysics Data System (ADS)

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.

Vysotskii, D. V.; Napartovich, A. P.; Troshchieva, V. N.

2007-04-01

266

Single image orthogonal fringe technique for resolution enhancement of the Fourier transform fringe analysis method  

NASA Astrophysics Data System (ADS)

Gradient range and spatial resolution in Fourier Transform Profilometry depend on the size of the filter window in reciprocal space. The proposed methods to date for the elimination of the fundamental frequency and enlargement of the filter window are either too computationally complex or depend on the possibility of using two frames, thus disabling the method's ability to cope with dynamic situations and subjecting the results to possible intensity changes between the two frame acquisitions. This article describes a simple method for using a single crossed fringe pattern to accomplish that objective, greatly improving the previously reported technique, whilst retaining its main advantages.

Tavares, Paulo J.; Vaz, Mário A. P.

2013-03-01

267

Description of the morphology of roots of Chicorium intybus L. partim by means of image analysis: Comparison of elliptic Fourier descriptors and classical parameters  

Microsoft Academic Search

In the framework of DUS testing (distinctness, uniformity and stability) of new varieties of Chicorium intybus L. partim, experts are manually measuring or scoring the shape of the roots. This way of working has several disadvantages in comparison to image analysis techniques. In this study two methods based on image analysis are statistically compared and evaluated: elliptic Fourier descriptors and

P. Lootens; J. Van Waes; L. Carlier

2007-01-01

268

Experimental Study on Gas-Liquid Two-Phase Flows in an Areation Tank by Using Image Treatment Method  

Microsoft Academic Search

Particle Image Velocimetry (PIV) technique was employed to study experimentally gas-liquid two-phase flow in an aeration tank. In terms of the PIV principles, an algorithm of PIV based on the Fast Fourier Transformation (FFT) was worked out. The PIV program was developed and verified, and then was used to measure three kinds of states in the testing device. The program

Wen CHENG; Wen-hong LIU; Bao-wei HU; Tian WAN

2008-01-01

269

Automated Processing of Shoeprint Images Based on the Fourier Transform for Use in Forensic Science  

Microsoft Academic Search

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

Philip De Chazal; John Flynn; Richard B. Reilly

2005-01-01

270

Fourier microfluidics.  

PubMed

We present a new experimental technique for the separation of dynamic chemical signals based on their frequency domain characteristics. Such a technique can be used to create filters that separate slow signals from fast signals from a common input flow stream. The propagation of time-varying chemical waves through networks of microfluidic channels is first examined. Mathematical models and a set of simple experiments are developed that demonstrate that short microfluidic channels behave as linear delay lines. The observed dispersive broadening and delay behavior can be explained in Fourier space in terms of corresponding phase delay, amplitude decay and characteristic transfer functions. Such delay components can be utilized to implement frequency dependent interference filters. An 8th order PDMS bandpass filter chip demonstrating these ideas was constructed. The filter chip has a central frequency of 0.17 Hz and a bandwith of 0.04 Hz at a flow rate of 4 microL h(-1). PMID:18432349

Xie, Y; Wang, Y; Chen, L; Mastrangelo, C H

2008-03-13

271

Ultrahigh speed Spectral / Fourier domain OCT ophthalmic imaging at 70,000 to 312,500 axial scans per second  

PubMed Central

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.

Potsaid, Benjamin; Gorczynska, Iwona; Srinivasan, Vivek J.; Chen, Yueli; Jiang, James; Cable, Alex; Fujimoto, James G.

2009-01-01

272

Optical image compression based on segmentation of the Fourier plane: new approaches and critical analysis  

Microsoft Academic Search

We present a new optical image compression approach based on spectral selection and using a segmented filter. In order to identify the method offering the best quality of reconstruction of the optically compressed images, we investigated several spectral segmentation methods. The compression is carried out in the spectral domain and results in a compound spectrum referred to as the segmented

S. Soualmi; A. Alfalou; H. Hamam

2007-01-01

273

Phased Contrast X-Ray Imaging  

ScienceCinema

The Pacific Northwest National Laboratory is developing a range of technologies to broaden the field of explosives detection. Phased contrast X-ray imaging, which uses silicon gratings to detect distortions in the X-ray wave front, may be applicable to mail or luggage scanning for explosives; it can also be used in detecting other contraband, small-parts inspection, or materials characterization.

274

Subcellular biochemical investigation of purkinje neurons using synchrotron radiation fourier transform infrared spectroscopic imaging with a focal plane array detector.  

PubMed

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

2013-05-20

275

Fast Fourier Transform and Filtered Image Analyses of Fiber Orientation in OSB  

Microsoft Academic Search

The objective of this paper is to investigate the relationship between resolution of images and measurement of fiber orientation\\u000a in oriented strand board with the ultimate aim of optimising the fiber orientation and quality of the manufactured product.\\u000a An important consideration has been the capture of images from a distance of 2 meters corresponding to conditions on an OSB\\u000a production

T. Nishimura; M. P. Ansell

2002-01-01

276

Toward Fourier interferometry fluorescence excitation\\/emission imaging of malignant cells combined with photoacoustic microscopy  

Microsoft Academic Search

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) and a recently synthesized mitochondrial oxygen probe, [PRE,P1\\

Elli Kohen; Joseph G. Hirschberg; John P. Berry; Nuri Ozkutuk; Ceren Ornek; Marco Monti; Roger M. Leblanc; Dietrich O. Schachtschabel; Sumaira Haroon

2003-01-01

277

Dithranol as a MALDI matrix for tissue imaging of lipids by Fourier transform ion cyclotron resonance mass spectrometry.  

PubMed

To fill the unmet need for improved matrixes for matrix-assisted laser desorption ionization (MALDI) tissue imaging of small molecules, dithranol (DT)--a matrix mainly used for the analysis of synthetic polymers--was evaluated for detection of lipids in rat liver and bovine calf lens, using MALDI Fourier transform ion cyclotron resonance mass spectrometry (FTICR MS). The use of DT resulted in better detection of endogenous lipids than did two other commonly used matrixes, ?-cyano-4-hydroxycinnamic acid (CHCA) and 2,5-dihydroxybenzoic acid (DHB), with >70 lipid entities (including phosphatidylcholines, phosphatidylethanolamines, sphingomyelins, phosphatidylserines, phosphatidylglycerol, phosphatidic acids, ceramide phosphates, sterol lipids, acyl carnitines, and glycerides) being detected in rat liver and bovine lens tissue sections, using positive-ion detection. Using saturated DT in chloroform/methanol (2:1, v/v), with 1% formic acid in the final mixture, 57 lipid entities were successfully imaged from bovine calf lens, with clear and distinct distribution patterns. In a section across the lens equatorial plane, all compounds showed concentric distributions around the lens nucleus and most showed specific abundance changes, which correlated with lens fiber cell age. As a novel finding, palmitoylcarnitine and oleoylcarnitine were found uniquely localized to the younger lens fiber cell cortex region. This work demonstrates the potential of DT as a new matrix for tissue imaging by MALDI-FTICR MS. PMID:22931516

Le, Cuong H; Han, Jun; Borchers, Christoph H

2012-09-12

278

Analysis of hyper-spectral data derived from an imaging Fourier transform: A statistical perspective  

SciTech Connect

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.

Sengupta, S.K.; Clark, G.A.; Fields, D.J.

1996-01-10

279

Digital particle image velocimetry (DPIV) robust phase correlation  

NASA Astrophysics Data System (ADS)

A novel correlation technique, the robust phase correlation (RPC), is introduced which amplifies the signal-to-noise ratio of the DPIV cross-correlation to produce velocity estimations that are accurate and robust to a variety of image conditions. Specifically, this estimator shows substantial resilience against additive background noise non-uniform illumination and thermal noise effects. In addition, the RPC is able to substantially reduce bias errors and peak locking in the presence of high shear and rotational motion in comparison with standard cross-correlation algorithms. The success of this technique relies upon an analytical decomposition of the DPIV signal-to-noise ratio, which is then applied as a spectral filter in a novel implementation of the generalized cross-correlation (GCC). The RPC also utilizes advanced windowing techniques to attenuate Fourier-based errors. Because of the GCC filtering, the application of windowing in the RPC is not susceptible to the effects of additive background noise that commonly causes errors for windowed cross-correlation estimation. The RPC estimator is validated using both artificial images and experimental data to demonstrate its enhanced measurement capabilities.

Eckstein, Adric; Vlachos, Pavlos P.

2009-05-01

280

Combined Parallel and Partial Fourier MR Reconstruction for Accelerated 8-Channel Hyperpolarized Carbon-13 In Vivo Magnetic Resonance Spectroscopic Imaging (MRSI)  

PubMed Central

Purpose To implement and evaluate combined parallel magnetic resonance imaging (MRI) and partial Fourier acquisition and reconstruction for rapid hyperpolarized carbon-13 (13C) spectroscopic imaging. Short acquisition times mitigate hyperpolarized signal losses that occur due to T1 decay, metabolism, and radiofrequency (RF) saturation. Human applications additionally require rapid imaging to permit breath-holding and to minimize the effects of physiologic motion. Materials and Methods Numerical simulations were employed to validate and characterize the reconstruction. In vivo MR spectroscopic images were obtained from a rat following injection of hyperpolarized 13C pyruvate using an 8-channel array of carbon-tuned receive elements. Results For small spectroscopic matrix sizes, combined parallel imaging and partial Fourier undersampling resulted primarily in decreased spatial resolution, with relatively less visible spatial aliasing. Parallel reconstruction qualitatively restored lost image detail, although some pixel spectra had persistent numerical error. With this technique, a 30 × 10 × 16 matrix of 4800 3D MR spectroscopy imaging voxels from a whole rat with isotropic 8 mm3 resolution was acquired within 11 seconds. Conclusion Parallel MRI and partial Fourier acquisitions can provide the shorter imaging times and wider spatial coverage that will be necessary as hyperpolarized 13C techniques move toward human clinical applications.

Ohliger, Michael A.; Larson, Peder E.Z.; Bok, Robert A.; Shin, Peter; Hu, Simon; Tropp, James; Robb, Fraser; Carvajal, Lucas; Nelson, Sarah J.; Kurhanewicz, John; Vigneron, Daniel B.

2013-01-01

281

X-ray phase contrast image simulation  

NASA Astrophysics Data System (ADS)

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.

Peterzol, A.; Berthier, J.; Duvauchelle, P.; Ferrero, C.; Babot, D.

2007-01-01

282

Combined fluorescence and phase contrast imaging at the Advanced Photon Source.  

SciTech Connect

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.

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

283

Coherent Ghost Imaging based on sparsity constraint without phase-sensitive detection  

NASA Astrophysics Data System (ADS)

A universal process for coherent Ghost Imaging (GI) without phase-sensitive detection is presented in this paper. The process is based on the sparsity constraint of the target, which helps to accelerate the information extraction. By taking advantage of this process, the coherent GI scheme with a point-like detector in the test path is improved to achieve higher efficiency and higher resolution, even though the phase information of the random field is lost. This process will contribute to the practical applications, such as Fourier-transform diffraction GI of X-ray, and remote sensing.

Wang, Hui; Han, Shensheng

2012-04-01

284

Fourier transform-infrared studies of thin HâSOâ\\/HâO films: Formation, water uptake, and solid-liquid phase changes  

Microsoft Academic Search

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 SOâ with HâO. 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

Ann M. Middlebrook; Laura T. Iraci; Laurie S. Mcneill; Birgit G. Koehler; Margaret A. Wilson; Ole W. Saastad; Margaret A. Tolbert; David R. Hanson

1993-01-01

285

Fourier transform ion cyclotron resonance investigation of the deuterium isotope effect on gas phase ion\\/molecule hydrogen bonding interactions in alcohol--fluoride adduct ions  

Microsoft Academic Search

Fourier transform ion cyclotron resonance measurements of the deuterium isotope effect have been used to probe the nature of the potential describing the motion of the hydrogen in gas phase ion\\/molecule hydrogen bond interactions. The hydrogen bonding system studied is fluoride ion solvated by one molecule of aliphatic alcohol, ROH · F-. No variation of the isotope effect with alcohol

F. E. Wilkinson; J. E. Szulejko; C. E. Allison; T. B. McMahon

1992-01-01

286

Fourier transform infrared investigation of the effects of irradiation on the 19 and 30°C phase transitions in polytetrafluoroethylene. [Gamma rays  

Microsoft Academic Search

Fourier transform infrared spectroscopy has been used in conjunction with differential scanning calorimetric measurements to investigate the nature of molecular degradation and its effect on the phase transition temperatures in irradiated polytetrafluoroethylene (PTFE). Both the 19 and 30°C transitions are observed to exhibit similar shifts to low temperatures upon irradiation. Infrared absorbance subtraction data from irradiated PTFE indicate a continual

H. Vanni; J. F. Rabolt

1980-01-01

287

Polynomial system of equations and its applications to the study of the effect of noise on multidimensional Fourier transform phase retrieval from magnitude  

Microsoft Academic Search

In this paper we deal with the problem of retrieving a finite-extent signal from the magnitude of its Fourier transform. We will present a brief review of the algebraic problem of the uniqueness of the solution for both discrete and continuous phase retrieval models. Several important issues which are yet unresolved will be pointed out and discussed. We will then

J. L. C. Sanz; T. S. Huang

1985-01-01

288

Patient-specific dosimetry using quantitative SPECT imaging and three-dimensional discrete fourier transform convolution  

SciTech Connect

The objective of this study was to develop a three-dimensional discrete Fourier transform (3D-DFT) convolution method to perform the dosimetry for {sup 131}I-labeled antibodies in soft tissues. Mathematical and physical phantoms were used to compare 3D-DFT with Monte Carlo transport (MCT) calculations based on the EGS4 code. The mathematical and physical phantoms consisted of a sphere and cylinder, respectively, containing uniform and nonuniform activity distributions. Quantitative SPECT reconstruction was carried out using the circular harmonic transform (CHT) algorithm. The radial dose profile obtained from MCT calculations and the 3D-DFT convolution method for the mathematical phantom were in close agreement. The root mean square error (RMSE) for the two methods was <0.1%, with a maximum difference <21%. Results obtained for the physical phantom gave a RMSE <0.1% and a maximum difference of <13%; isodose contours were in good agreement. SPECT data for two patients who had undergone {sup 131}I radioimmunotherapy (RIT) were used to compare absorbed-dose rates and isodose rate contours with the two methods of calculations. This yielded a RMSE <0.02% and a maximum difference of <13%. Our results showed that the 3D-DFT convolution method compared well with MCT calculations. The 3D-DFT approach is computationally much more efficient and, hence, the method of choice. This method is patient-specific and applicable to the dosimetry of soft-tissue tumors and normal organs. It can be implemented on personal computers. 22 refs., 6 figs., 2 tabs.

Akabani, G.; Hawkins, W.G.; Eckblade, M.B.; Leichner, P.K. [Univ. of Nebraska Medical Center, Omaha, NE (United States)

1997-02-01

289

Image reconstruction algorithm for recovering high-frequency information in parallel phase-shifting digital holography [Invited].  

PubMed

We propose an image reconstruction algorithm for recovering high-frequency information in parallel phase-shifting digital holography. The proposed algorithm applies three kinds of interpolations and generates three different kinds of object waves. A Fourier transform is applied to each object wave, and the spatial-frequency domain is divided into 3×3 segments for each Fourier-transformed object wave. After that the segment in which interpolation error is the least among the segments having the same address of the segment in the spatial-frequency domain is extracted. The extracted segments are combined to generate an information-enhanced spatial-frequency spectrum of the object wave, and after that the formed spatial-frequency spectrum is inversely Fourier transformed. Then the high-frequency information of the reconstructed image is recovered. The effectiveness of the proposed algorithm was verified by a numerical simulation and an experiment. PMID:23292396

Xia, Peng; Shimozato, Yuki; Tahara, Tatsuki; Kakue, Takashi; Awatsuji, Yasuhiro; Nishio, Kenzo; Ura, Shogo; Kubota, Toshihiro; Matoba, Osamu

2013-01-01

290

Effect of Sucrose on Phase Behavior of Membranes in Intact Pollen of Typha latifolia L., as Measured with Fourier Transform Infrared Spectroscopy 1  

PubMed Central

In previous studies, we have shown that the temperature dependent vibrational frequency of the CH2 stretch in hydrocarbons in intact pollen grains can be recorded with Fourier transform infrared spectroscopy and used to measure phase transition temperatures (Tm) in these hydrocarbons. Circumstantial evidence was provided that the major contribution to the signal seen in these samples was from membrane phospholipids, and that sucrose in the dry pollen grains reduced Tm of those phospholipids. In the current study, we clarify why a major constituent of the pollen grains, neutral lipids contained in discrete lipid droplets, does not contribute significantly to the signal. Further, we have isolated membranes from the pollen and show that Tm in the isolated membranes rises from ?6°C in the hydrated membranes to 58°C when the membranes are dried without the addition of sucrose. However, when the isolated membranes are dried in the presence of increasing amounts of sucrose, Tm fell steadily, reaching a minimal value of 31°C, a figure in good agreement with that seen in the intact pollen grains. The amount of sucrose required to depress Tm maximally in these membranes is also apparently in agreement with that found in the intact pollen, suggesting that sucrose depresses Tm in the pollen. ImagesFigure 5

Hoekstra, Folkert A.; Crowe, John H.; Crowe, Lois M.

1991-01-01

291

Spectral noise due to measurement errors of Mach-Zehnder interferometer optical path phases in a complex Fourier-transform integrated-optic spatial heterodyne spectrometer  

NASA Astrophysics Data System (ADS)

We calculate the root-mean-square (rms) value of the spectral noise caused by optical path phase measurement errors in a spatial heterodyne spectrometer (SHS) featuring a complex Fourier transformation. We show that the rms value is proportional to the rms error of the phase measurement and the proportionality coefficient is given analytically. The relationship enables us to estimate the possible performance of the SHS such as the sidelobe suppression ratio for a given measurement error.

Takada, Kazumasa; Seino, Mitsuyoshi; Chiba, Akito; Okamoto, Katsunari

2013-06-01

292

Vacuum compatible sample positioning device for matrix assisted laser desorption/ionization Fourier transform ion cyclotron resonance mass spectrometry imaging  

SciTech Connect

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.

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

293

Fourier Transform Infrared Imaging Shows Reduced Unsaturated Lipid Content in the Hippocampus of a Mouse Model of Alzheimer's Disease  

PubMed Central

Polyunsaturated fatty acids are essential to brain functions such as membrane fluidity, signal transduction, and cell survival. It is also thought that low levels of unsaturated lipid in the brain may contribute to Alzheimer’s disease (AD) risk or severity. However, it is not known how accumulation of unsaturated lipids is affected in different regions of the hippocampus, which is a central target of AD plaque pathology, during aging. In this study, we used Fourier Transform Infrared Imaging (FTIRI) to visualize the unsaturated lipid content in specific regions of the hippocampus in the PSAPP mouse model of AD as a function of plaque formation. Specifically, the unsaturated lipid content was imaged using the olefinic =CH stretching mode at 3012 cm?1. The axonal, dendritic, and somatic layers of the hippocampus were examined in the mice at 13 weeks, 24 weeks, 40 weeks and 56 weeks old. Results showed that lipid unsaturation in the axonal layer is significantly increased with normal aging in control (CNT) mice (p < 0.01), but remained low and relatively constant in PSAPP mice. Thus, these findings indicate that unsaturated lipid content is reduced in hippocampal white matter during amyloid pathogenesis and that maintaining unsaturated lipid content early in the disease may be critical in avoiding progression of the disease.

Leskovjan, Andreana C.; Kretlow, Ariane; Miller, Lisa M.

2010-01-01

294

Fourier transform ion cyclotron resonance mass spectrometric study of gas-phase ion-molecule reactions  

SciTech Connect

Gas-phase ion-molecule reactions of rare earth (include Sc, Y, and all the lanthanide series) metal ion (except Pm[sup +]) reactions with benzene and alkyl benzene ligands were systematically studied by FT/ICR mass spectrometry. An electronic configuration d[sup 1]s[sup 1] was found to be necessary for the ions to insert into C-C and/or C-H bonds of alkyl groups of the ligands. When the promotion energy for the transition groups of the ligands. When the promotion energy for the transition f[sup n]s[sup 1] [yields] f[sup n[minus]1]d[sup 1]s[sup 1] was large, no reaction resulting from activation was observed. Some of the rare earth metal ions do not activate C-C or C-H bond of saturated hydrocarbons, but are rather reactive with alkyl groups of aromatic ligands. Most of the rare earth ions only from intact complex ions with benzene, while Sc[sup +], Y[sup +], La[sup +] and Ce[sup +] form metal-benzyne ions. Rare earth metal ions are quite oxophilic and readily react with background oxygen containing species when the reactions with organic ligand(s). A hyperbolic ion trap for ET/ICR mass spectrometry was evaluated experimentally and compared with the most commonly used cubic ion trap. The hyperbolic trap offers several advantages over the cubic ion trap. The hyperbolic trap offers several advantages over the cubic trap: improved mass resolving power, improved mass accuracy for wide-range mass spectra, and elimination of frequency shift due to different ion cyclotron radius. But z-ejection is more pronounced in the hyperbolic than in the cubic trap.

Yin, Winnie Weixin.

1993-01-01

295

The Fourier Imaging X-ray Spectrometer (FIXS) for the Argentinian, Scout-launched satelite de Aplicaciones Cienficas-1 (SAC-1)  

NASA Astrophysics Data System (ADS)

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.

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

1988-11-01

296

Generalized fiber Fourier optics.  

PubMed

A twofold generalization of the optical schemes that perform the discrete Fourier transform (DFT) is given: new passive planar architectures are presented where the 2 × 2 3 dB couplers are replaced by M × M hybrids, reducing the number of required connections and phase shifters. Furthermore, the planar implementation of the discrete fractional Fourier transform (DFrFT) is also described, with a waveguide grating router (WGR) configuration and a properly modified slab coupler. PMID:21686007

Cincotti, Gabriella

2011-06-15

297

Fourier Transform Infrared Spectroscopy for Identification and Quantification of Organic Functional Groups in Aqueous Phase Secondary Organic Aerosol  

NASA Astrophysics Data System (ADS)

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.

George, K.; Ruthenburg, T. C.; Smith, J.; Anastasio, C.; Dillner, A. M.

2011-12-01

298

Optical image encryption with a bit-plane separation method in phase-shifting digital holography  

NASA Astrophysics Data System (ADS)

In this paper, we propose a method for optical image encryption based on fractional Fourier transform (FRFT) and Arnold transform (ART) in phase-shifting digital holography. An input image is first divided into eight bit planes, and each bit plane is encrypted based on double random-phase masks and FRFT. Complex amplitude for the object is retrieved by phase-shifting digital holography in the hologram plane. The real and imaginary parts of the retrieved complex amplitudes for the 0th-7th bit planes are further encrypted using ART algorithm. Numerical results are shown to demonstrate the feasibility and effectiveness of the proposed technique. The sensitivity of security parameters, such as function orders in FRFT and iteration number in ART method, is also analyzed.

Chen, Wen; Quan, Chenggen; Tay, Cho Jui

2009-12-01

299

Multicontrast x-ray computed tomography imaging using Talbot-Lau interferometry without phase stepping  

SciTech Connect

Purpose: The purpose of this work is to demonstrate that multicontrast computed tomography (CT) imaging can be performed using a Talbot-Lau interferometer without phase stepping, thus allowing for an acquisition scheme like that used for standard absorption CT. Methods: Rather than using phase stepping to extract refraction, small-angle scattering (SAS), and absorption signals, the two gratings of a Talbot-Lau interferometer were rotated slightly to generate a moire pattern on the detector. A Fourier analysis of the moire pattern was performed to obtain separate projection images of each of the three contrast signals, all from the same single-shot of x-ray exposure. After the signals were extracted from the detector data for all view angles, image reconstruction was performed to obtain absorption, refraction, and SAS CT images. A physical phantom was scanned to validate the proposed data acquisition method. The results were compared with a phantom scan using the standard phase stepping approach. Results: The reconstruction of each contrast mechanism produced the expected results. Signal levels and contrasts match those obtained using the phase stepping technique. Conclusions: Absorption, refraction, and SAS CT imaging can be achieved using the Talbot-Lau interferometer without the additional overhead of long scan time and phase stepping.

Bevins, Nicholas; Zambelli, Joseph; Li Ke; Qi Zhihua; Chen Guanghong [Department of Medical Physics, University of Wisconsin-Madison, 1111 Highland Avenue, Madison, Wisconsin 53705 (United States); Department of Medical Physics, University of Wisconsin-Madison, 1111 Highland Avenue, Madison, Wisconsin 53705 (United States) and Department of Radiology, University of Wisconsin-Madison, 600 Highland Avenue, Madison, Wisconsin 53792 (United States)

2012-01-15

300

Double random phase encryption scheme to multiplex and simultaneous encode multiple images.  

PubMed

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

Alfalou, Ayman; Mansour, Ali

2009-11-01

301

Monitoring of biochemical changes through the c6 gliomas progression and invasion by fourier transform infrared (FTIR) imaging.  

PubMed

We have investigated the spatial distribution of molecular changes associated with C6 glioma progression using Fourier transform infrared (FT-IR) microspectro-imaging in order to determine spectroscopic markers for early diagnosis of tumor growth. Our results showed that at day 7 after tumor implantation, FTIR investigations displayed a very small abnormal zone associated with the proliferation of C6 cells in the caudate putamen. From this day, rats developed solid and well-circumscribed tumors and invasive areas. The volume of peritumoral areas increased rapidly until day 19. The maturation of the tumor was accompanied by a diminution in its proliferative and invasive area. The presence of necrotic areas was visible from day 15. A non-negative least-squares algorithm was used to quantify spatial distribution of molecular changes in tissues (lipids, nucleic acids, and proteins) associated with glioma progression. Compared to those in normal brain, statistical tests on fit coefficients showed that the concentrations of sphingomyelin (SMY), nucleic acids, phosphatidylserine (PS), and galactocerebroside (GalC) were significantly affected during C6 glioma development. These constituents can be used as spectroscopic markers for C6 glioma progression. Indeed, the concentration of DNA decreased significantly from tumor to invasion, to normal brain tissues, the necrotic area has higher concentrations of the Galc than other areas. The PS content was significantly higher in the peritumoral zone and decreased in the tumor zones matter. PMID:19824663

Beljebbar, Abdelilah; Dukic, Sylvain; Amharref, Nadia; Bellefqih, Salima; Manfait, Michel

2009-11-15

302

Automation and Control of an Imaging Internal Laser Desorption Fourier Transform Mass Spectrometer (I2LD-FTMS)  

SciTech Connect

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 Instrument's (Austin, Texas) graphical programming language LabVIEW to control the motors of the laser positioning system and the commercial FTMS data acquisition system. A feature of the FTMS software that allows the user to write macros in a scripting language is used creatively to our advantage in creating a mechanism to control the FTMS from outside its graphical user interface. The new user interface also allows the user to configure target locations. Automation of the data analysis along with data display using commercial graphing software is also described.

McJunkin, Timothy R; Tranter, Troy Joseph; Scott, Jill Rennee

2002-06-01

303

Feasibility of differential phase contrast CT for whole body imaging  

NASA Astrophysics Data System (ADS)

Phase contrast based imaging techniques have shown improved contrast in certain biological materials. This has led to an increased interest for the potential of preclinical and clinical imaging systems that incorporate phase sensitive imaging techniques. However, the interplay between the phase contrast mechanism and the so-called small-angle scattering or dark-field mechanism is often not considered. In this work we explore the potential for phase-sensitive whole body imaging by imaging a freshly euthanized specimen. The results suggest that when extrapolating phantom and ex vivo results to whole body imaging, one must consider the complex anatomy of the entire body and its effect on each contrast mechanism.

Li, Ke; Bevins, Nicholas B.; Zambelli, Joseph N.; Chen, Guang-Hong

2012-07-01

304

Sub-cellular spectrochemical imaging of isolated human corneal cells employing synchrotron radiation-based Fourier-transform infrared microspectroscopy.  

PubMed

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

Fogarty, Simon W; Patel, Imran I; Trevisan, Júlio; Nakamura, Takahiro; Hirschmugl, Carol J; Fullwood, Nigel J; Martin, Francis L

2012-11-15

305

Fourier Theory  

NSDL National Science Digital Library

This module, developed by the Maricopa Advanced Technology Education Center (MATEC) project called Work-Ready Electronics, presents the basis and applications of Fourier theory. On this site, visitors will find five sections: Frequency Domain View of Electronic Signals, the Frequency Domain, The Fourier Theory: A Technician Level Explanation, Bandwidth, and Applications of Fourier Theory. Each section is followed by a Knowledge Probe assessment which asks questions about the material that was just covered. The Learning Resource section of the site contains laboratory activities and questions for practice and research as well as links to further information on Fourier theory. There is also a glossary of terms from all aspects of electronics, and a handy notebook tool with allows visitors to jot down notes and thoughts as they work through the activities.

2008-08-15

306

Fourier analysis of a gated blood-pool study during atrial flutter  

SciTech Connect

First-harmonic Fourier analysis of a gated blood-pool study is based on the assumption that the cardiac chambers contract once per cardiac cycle. In atrial arrhythmias this condition may not exist for the atria. We recently studied a patient with atrial flutter and 2:1 artioventricular conduction. There were predictable alterations in the first-harmonic Fourier phase and amplitude images. The observed changes from first-harmonic Fourier analysis were: (a) very low atrial amplitude values, and (b) absence of identifiable atrial regions on the phase image.

Makler, P.T. Jr.; McCarthy, D.M.; London, J.W.; Sandler, M.S.; Alavi, A.

1983-08-01

307

Fourier transform-infrared studies of thin H2SO4\\/H2O films: Formation, water uptake, and solid-liquid phase changes  

Microsoft Academic Search

Fourier transform-infrared (FTIR) spectroscopy was use 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

Ann M. Middlebrook; Laura T. Iraci; Laurie S. McNeill; Birgit G. Koehler; Margaret A. Wilson; Ole W. Saastad; Margaret A. Tolbert; David R. Hanson

1993-01-01

308

Pseudorandom phase masks for superresolution imaging from subpixel shifting.  

PubMed

We present a method for overcoming the pixel-limited resolution of digital imagers. Our method combines optical point-spread function engineering with subpixel image shifting. We place an optimized pseudorandom phase mask in the aperture stop of a conventional imager and demonstrate the improved performance that can be achieved by combining multiple subpixel shifted images. Simulation results show that the pseudorandom phase-enhanced lens (PRPEL) imager achieves as much as 50% resolution improvement over a conventional multiframe imager. The PRPEL imager also enhances reconstruction root-mean-squared error by as much as 20%. We present experimental results that validate the predicted PRPEL imager performance. PMID:17415395

Ashok, Amit; Neifeld, Mark A

2007-04-20

309

MR image segmentation of the knee bone using phase information  

Microsoft Academic Search

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

Pierrick Bourgeat; Jurgen Fripp; Peter Stanwell; Saadallah Ramadan; Sébastien Ourselin

2007-01-01

310

Phase contrast imaging: a new tool for biomedical investigations  

Microsoft Academic Search

Imaging biological tissue usually needs very sensitive instruments that allow high contrast while keeping the dose deposition to a minimum. With the advent of third generation synchrotron radiation sources new, phase contrast-based imaging techniques have become available. In this work, we present two recently developed phase imaging methods: the first is based on a full 3D approach and is suitable

Marco Stampanoni; Amela Groso; Franz Pfeiffer; Oliver Bunk; Timm Weitkamp; Ana Diaz; Christian David

2006-01-01

311

Comparison of retinal thickness by Fourier-domain optical coherence tomography and OCT retinal image analysis software segmentation analysis derived from Stratus optical coherence tomography images  

NASA Astrophysics Data System (ADS)

Purpose: To compare thickness measurements between Fourier-domain optical coherence tomography (FD-OCT) and time-domain OCT images analyzed with a custom-built OCT retinal image analysis software (OCTRIMA). Methods: Macular mapping (MM) by StratusOCT and MM5 and MM6 scanning protocols by an RTVue-100 FD-OCT device are performed on 11 subjects with no retinal pathology. Retinal thickness (RT) and the thickness of the ganglion cell complex (GCC) obtained with the MM6 protocol are compared for each early treatment diabetic retinopathy study (ETDRS)-like region with corresponding results obtained with OCTRIMA. RT results are compared by analysis of variance with Dunnett post hoc test, while GCC results are compared by paired t-test. Results: A high correlation is obtained for the RT between OCTRIMA and MM5 and MM6 protocols. In all regions, the StratusOCT provide the lowest RT values (mean difference 43 +/- 8 ?m compared to OCTRIMA, and 42 +/- 14 ?m compared to RTVue MM6). All RTVue GCC measurements were significantly thicker (mean difference between 6 and 12 ?m) than the GCC measurements of OCTRIMA. Conclusion: High correspondence of RT measurements is obtained not only for RT but also for the segmentation of intraretinal layers between FD-OCT and StratusOCT-derived OCTRIMA analysis. However, a correction factor is required to compensate for OCT-specific differences to make measurements more comparable to any available OCT device.

Tátrai, Erika; Ranganathan, Sudarshan; Ferencz, Mária; Debuc, Delia Cabrera; Somfai, Gábor Márk

2011-05-01

312

Comparison of retinal thickness by Fourier-domain optical coherence tomography and OCT retinal image analysis software segmentation analysis derived from Stratus optical coherence tomography images  

PubMed Central

Purpose: To compare thickness measurements between Fourier-domain optical coherence tomography (FD-OCT) and time-domain OCT images analyzed with a custom-built OCT retinal image analysis software (OCTRIMA). Methods: Macular mapping (MM) by StratusOCT and MM5 and MM6 scanning protocols by an RTVue-100 FD-OCT device are performed on 11 subjects with no retinal pathology. Retinal thickness (RT) and the thickness of the ganglion cell complex (GCC) obtained with the MM6 protocol are compared for each early treatment diabetic retinopathy study (ETDRS)-like region with corresponding results obtained with OCTRIMA. RT results are compared by analysis of variance with Dunnett post hoc test, while GCC results are compared by paired t-test. Results: A high correlation is obtained for the RT between OCTRIMA and MM5 and MM6 protocols. In all regions, the StratusOCT provide the lowest RT values (mean difference 43 ± 8 ?m compared to OCTRIMA, and 42 ± 14 ?m compared to RTVue MM6). All RTVue GCC measurements were significantly thicker (mean difference between 6 and 12 ?m) than the GCC measurements of OCTRIMA. Conclusion: High correspondence of RT measurements is obtained not only for RT but also for the segmentation of intraretinal layers between FD-OCT and StratusOCT-derived OCTRIMA analysis. However, a correction factor is required to compensate for OCT-specific differences to make measurements more comparable to any available OCT device.

Tatrai, Erika; Ranganathan, Sudarshan; Ferencz, Maria; DeBuc, Delia Cabrera; Somfai, Gabor Mark

2011-01-01

313

X-Ray Phase Imaging For Breast Cancer Detection.  

National Technical Information Service (NTIS)

The long term objective of the project is to develop a low-dose and quantitative phase x-ray imaging technique for facilitating breast cancer detection. Phase retrieval from a single phase contrast image is the key strategy for this project. In this perio...

X. Wu

2009-01-01

314

Phase Sensitive X-Ray Imaging: Towards its Interdisciplinary Applications  

Microsoft Academic Search

X-ray phase imaging including phase tomography has been attracting increasing attention during the past few decades. The advantage of X-ray phase imaging is that an extremely high sensitivity is achieved for weakly absorbing materials, such as biological soft tissues, which generate a poor contrast by conventional schemes. Especially for such living samples, where the reduction of the applied dose is

C. Kottler; V. Revol; R. Kaufmann; C. Urban; K. Knop; U. Sennhauser; I. Jerjen; T. Lüthi; F. Cardot; P. Niedermann; J.-P. Morel; C. Maake; H. Walt; E. Knop; N. Blanc

2010-01-01

315

Reactions of metal ions and their clusters in the gas phase using laser ionization: Fourier transform mass spectrometry. Progress report, February 1, 1993--January 31, 1994  

SciTech Connect

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.

Freiser, B.S.

1993-09-01

316

Structured illumination quantitative phase microscopy for enhanced resolution amplitude and phase imaging  

PubMed Central

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.

Chowdhury, Shwetadwip; Izatt, Joseph

2013-01-01

317

Clinical application of high-contrast three-dimensional imaging of the retina, choroid, and optic nerve with three-dimensional Fourier domain optical coherence tomography  

NASA Astrophysics Data System (ADS)

We present three dimensional (3D) imaging of macular diseases and glaucoma with high speed, Fourier domain optical coherence tomography (FD-OCT). Our FD-OCT system allows video rate cross-sectional imaging with 98 dB sensitivity and 4.3 ?m depth-resolution in tissue. This performance results in high contrast sectional images that enhance visualization of fine retinal layers including external limiting membrane and of deep structure such as the choroid and optic nerve. Volume rendering of 3D OCT data set taken for 3.5 seconds provides realistic 3D images of macular, optic disc and their pathologic changes. This manuscript will show the methods for three dimensional FD-OCT including a raster scanning protocol for volume rendering and cancellation of the motion artifact of eye balls, and the application of the high contrast three dimensional OCT imaging to macular diseases and glaucoma in clinical examination.

Hangai, Masanori; Yoshimura, Nagahisa; Yasuno, Yoshiaki; Makita, Shuichi; Aoki, Gouki; Nakamura, Yoshifumi; Yamanari, Masahiro; Ohtsuka, Hiroyuki; Fukuma, Yasufumi; Itoh, Masahide; Yatagai, Toyohiko

2006-03-01

318

X-ray phase imaging with a paper analyzer  

SciTech Connect

We present a simple x-ray phase imaging method that utilizes the sample-induced distortion of a high contrast random intensity pattern to quantitatively retrieve the two-dimensional phase map at the exit surface of a coherently illuminated sample. This reference pattern is created by placing a sheet of sandpaper in the x-ray beam, with the sample-induced distortion observed after propagation to the detector, a meter downstream. Correlation analysis comparing a single ''sample and sandpaper'' image to a reference ''sandpaper only'' image produces two sensitive differential phase contrast images, giving the sample phase gradient in vertical and horizontal directions. These images are then integrated to recover the projected phase depth of the sample. The simple experimental set-up, retention of flux, and the need for only a single sample image per reconstruction suggest that this method is of value in imaging a range of dynamic processes at both synchrotron and laboratory x-ray sources.

Morgan, Kaye S.; Paganin, David M. [School of Physics, Monash University, Victoria 3800 (Australia); Siu, Karen K. W. [Monash Biomedical Imaging, Monash University, Victoria 3800 (Australia); Australian Synchrotron, Victoria 3168 (Australia)

2012-03-19

319

Post-circular expansion of eccentric binary inspirals: Fourier-domain waveforms in the stationary phase approximation  

Microsoft Academic Search

We lay the foundations for the construction of analytic expressions for\\u000aFourier-domain gravitational waveforms produced by eccentric, inspiraling\\u000acompact binaries in a post-circular or small-eccentricity approximation. The\\u000atime-dependent, \\

Nicolas Yunes; K. G. Arun; Emanuele Berti; Clifford M. Will

2009-01-01

320

Dispersive Fourier transform spectroscopy  

Microsoft Academic Search

Dispersive Fourier transform spectroscopy (DFTS) is a technique for determining the optical constants of solids, liquids and gases from direct measurements of both the amplitude and phase of either their reyection or transmission coeficients. Measurements are usually made at normal incidence with the specimen in one arm of a Michelson interferometer. The technique has been widely used for measurements in

T. J. Parker

1990-01-01

321

Synthetic Aperture Fourier Holographic Optical Microscopy  

NASA Astrophysics Data System (ADS)

We report a new synthetic aperture optical microscopy in which high-resolution, wide-field amplitude and phase images are synthesized from a set of Fourier holograms. Each hologram records a region of the complex two-dimensional spatial frequency spectrum of an object, determined by the illumination field’s spatial and spectral properties and the collection angle and solid angle. We demonstrate synthetic microscopic imaging in which spatial frequencies that are well outside the modulation transfer function of the collection optical system are recorded while maintaining the long working distance and wide field of view.

Alexandrov, Sergey A.; Hillman, Timothy R.; Gutzler, Thomas; Sampson, David D.

2006-10-01

322

Quantitative evaluation of phase processing approaches in susceptibility weighted imaging  

NASA Astrophysics Data System (ADS)

Susceptibility weighted imaging (SWI) takes advantage of the local variation in susceptibility between different tissues to enable highly detailed visualization of the cerebral venous system and sensitive detection of intracranial hemorrhages. Thus, it has been increasingly used in magnetic resonance imaging studies of traumatic brain injury as well as other intracranial pathologies. In SWI, magnitude information is combined with phase information to enhance the susceptibility induced image contrast. Because of global susceptibility variations across the image, the rate of phase accumulation varies widely across the image resulting in phase wrapping artifacts that interfere with the local assessment of phase variation. Homodyne filtering is a common approach to eliminate this global phase variation. However, filter size requires careful selection in order to preserve image contrast and avoid errors resulting from residual phase wraps. An alternative approach is to apply phase unwrapping prior to high pass filtering. A suitable phase unwrapping algorithm guarantees no residual phase wraps but additional computational steps are required. In this work, we quantitatively evaluate these two phase processing approaches on both simulated and real data using different filters and cutoff frequencies. Our analysis leads to an improved understanding of the relationship between phase wraps, susceptibility effects, and acquisition parameters. Although homodyne filtering approaches are faster and more straightforward, phase unwrapping approaches perform more accurately in a wider variety of acquisition scenarios.

Li, Ningzhi; Wang, Wen-Tung; Sati, Pascal; Pham, Dzung L.; Butman, John A.

2012-02-01

323

Fourier transform infrared imaging as a method for detection of HLA class I expression in melanoma without the use of antibody.  

PubMed

Human leukocyte antigen (HLA) class I expression in melanoma is usually assessed using immunohistochemical staining. Here we report on the use of Fourier transform infrared (FTIR) hyperspectral imaging, a method widely used in two-dimensional analysis of chemical components, to study HLA class I expression in tissue. Two-dimensional cluster colour images derived from unsupervised hierarchical cluster analysis of FTIR hyperspectral data on melanoma sections were compared with consecutive sections that were immunohistochemically stained for class I expression. HLA-class-I-positive and -negative areas were differentiated by FTIR cluster images in all eight melanoma sections investigated without the need for antibody attachment. FTIR imaging enables the distinction of HLA-class-I-positive from class-I-negative areas in melanoma. This method is accurate, rapid and cost-effective. PMID:17445214

Chew, S F; Wood, B R; Kanaan, C; Browning, J; MacGregor, D; Davis, I D; Cebon, J; Tait, B D; McNaughton, D

2007-04-01

324

Ultrahigh speed 1050nm swept source/Fourier domain OCT retinal and anterior segment imaging at 100,000 to 400,000 axial scans per second.  

PubMed

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 100 kHz axial scan rate with 5.3 um axial resolution in tissue. Fixed rate sampling at 1 GSPS achieves a 7.5mm imaging range in tissue with 6.0 um axial resolution at 100 kHz axial scan rate. A 200 kHz axial scan rate with 5.3 um axial resolution over 4mm imaging range is achieved by buffering the laser sweep. Dual spot OCT using two parallel interferometers achieves 400 kHz axial scan rate, almost 2X faster than previous 1050 nm 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 12x12 mm data sets include the macula and optic nerve head. Small area, high density imaging shows individual cone photoreceptors. The 7.5 mm 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 1050 m wavelengths promises to improve performance for instrumentation which images both the retina and anterior eye. These advantages suggest that swept source OCT at 1050 nm wavelengths will play an important role in future ophthalmic instrumentation. PMID:20940894

Potsaid, Benjamin; Baumann, Bernhard; Huang, David; Barry, Scott; Cable, Alex E; Schuman, Joel S; Duker, Jay S; Fujimoto, James G

2010-09-13

325

Ultrahigh speed 1050nm swept source / Fourier domain OCT retinal and anterior segment imaging at 100,000 to 400,000 axial scans per second  

PubMed Central

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.

Potsaid, Benjamin; Baumann, Bernhard; Huang, David; Barry, Scott; Cable, Alex E.; Schuman, Joel S.; Duker, Jay S.; Fujimoto, James G.

2011-01-01

326

Characterization of skin abnormalities in a mouse model of osteogenesis imperfecta using high resolution magnetic resonance imaging and Fourier transform infrared imaging spectroscopy.  

PubMed

Evaluation of the skin phenotype in osteogenesis imperfecta (OI) typically involves biochemical measurements, such as histologic or biochemical assessment of the collagen produced from biopsy-derived dermal fibroblasts. As an alternative, the current study utilized non-invasive magnetic resonance imaging (MRI) microscopy and optical spectroscopy to define biophysical characteristics of skin in an animal model of OI. MRI of skin harvested from control, homozygous oim/oim and heterozygous oim/+ mice demonstrated several differences in anatomic and biophysical properties. Fourier transform infrared imaging spectroscopy (FT-IRIS) was used to interpret observed MRI signal characteristics in terms of chemical composition. Differences between wild-type and OI mouse skin included the appearance of a collagen-depleted lower dermal layer containing prominent hair follicles in the oim/oim mice, accounting for 55% of skin thickness in these. The MRI magnetization transfer rate was lower by 50% in this layer as compared to the upper dermis, consistent with lower collagen content. The MRI transverse relaxation time, T2, was greater by 30% in the dermis of the oim/oim mice compared to controls, consistent with a more highly hydrated collagen network. Similarly, an FT-IRIS-defined measure of collagen integrity was 30% lower in the oim/oim mice. We conclude that characterization of phenotypic differences between the skin of OI and wild-type mice by MRI and FT-IRIS is feasible, and that these techniques provide powerful complementary approaches for the analysis of the skin phenotype in animal models of disease. PMID:21845737

Canuto, H C; Fishbein, K W; Huang, A; Doty, S B; Herbert, R A; Peckham, J; Pleshko, N; Spencer, R G

2011-08-15

327

The gas phase characterization of perfluorobutyryl chloride, C 3F 7COCl, using chirped pulse Fourier transform microwave spectroscopy  

NASA Astrophysics Data System (ADS)

A chirped pulse Fourier transform microwave spectrometer has been used to record the pure rotational spectrum of perfluorobutyryl chloride seeded in a pulsed supersonic expansion of argon gas. Only one conformer of the title molecule was observed. For the 35Cl species a total of 236 spectral transitions were recorded. Quantum chemical calculations together with the spectral constants obtained indicate that the observed conformer has the CCCCOCl centers contained within the ab plane with a dihedral angle ?CCCO = 0°.

Grubbs, G. S., II; Cooke, S. A.

2009-11-01

328

Fourier transform infrared spectroscopy of electronic excitations to probe magnetic order and phase transitions in solid oxygen  

Microsoft Academic Search

Systematic Fourier transform infrared (FTIR) spectroscopic investigations of interaction-induced electronic transitions 3Sigma-g- 1Deltag (v=0,...,3) of solid and liquid oxygen were carried out in the temperature range 10-90 K at ambient pressure. We interpret these absorption bands as phonon sidebands to an electronic (or an electronic-vibrational) excitations plus (in alpha-O2) exciton (-vibron)-magnon bound states. A consistent description of electronic spectra in

S. A. Medvedev; A. P. Brodyanski; H. J. Jodl

2001-01-01

329

Measurements of imaging parameters of a phase contrast x-ray imaging prototype  

NASA Astrophysics Data System (ADS)

A high spatial resolution computed radiography (CR) detector was used to develop a phase contrast x-ray imaging prototype with a microfocus x-ray source. The phase contrast imaging was realized with appropriate magnifications. Meanwhile, the basic system parameters, such as the modulation transfer function (MTF) and detective quantum efficiency (DQE) were measured with and without phase contrast effect. The experimental results indicated that the phase contrast can enhance the detectability of the imaging system.

Li, Yuhua; Rong, John; Chu, Robert Y. L.; Zhang, Da; Archer, Ann; Fajardo, Laurie; Chen, Wei R.; Wu, Xizeng; Liu, Hong

2008-03-01

330

Thermal wave imaging with phase sensitive modulated thermography  

Microsoft Academic Search

A technique of thermal wave imaging with phase-sensitive modulated thermography ('thermal wave thermography') is described that combines the advantages of both the low-frequency CW modulation (providing phase angle information and a maximum depth range) and rapid scanning as it is used in the conventional thermographic imaging technique. Compared with the usual thermal wave techniques, the new technique provides an increased

G. Busse; D. Wu; W. Karpen

1992-01-01

331

Improving the resolution of three-dimensional acoustic imaging with planar phased arrays  

NASA Astrophysics Data System (ADS)

This paper examines and compares two methods of improving the quality of three-dimensional beamforming with phased microphone arrays. The intended application is the detection of aerodynamic noise sources on wind turbines. Both methods employ Fourier based deconvolution. The first method involves a transformation of coordinates that tends to make the response to a point source, the point spread function, more shift invariant. The result is a significant improvement in sound source imaging in the transformed coordinate system. However, the inverse transformation to Cartesian coordinates introduces range dependent resolution limitations because of the irregular distribution of the focal points. The second method combines the transformation of coordinates with an alternative scanning technique. This method can be used in near field three-dimensional acoustic imaging to produce maps free of sidelobes and with constant resolution. The robustness of the proposed methods is validated both with computer simulations and experimentally.

Xenaki, Angeliki; Jacobsen, Finn; Fernandez-Grande, Efren

2012-04-01

332

Cloaking of a phase object in ghost imaging  

NASA Astrophysics Data System (ADS)

Ghost imaging is a nonlocal imaging technique in which the image or diffraction pattern of an object can be observed through the intensity correlation measurement other than the intensity itself. Here, we report the experimental observation of invisibility cloaking in ghost imaging with thermal light. We show that when two identical phase-modulated objects are placed at equal distances from the thermal light source, they are offset completely in ghost imaging. The experimental results can be understood through the phase conjugation established by the intensity correlation of thermal light.

Gan, Shu; Zhang, Su-Heng; Zhao, Ting; Xiong, Jun; Zhang, Xiangdong; Wang, Kaige

2011-03-01

333

Phase tomography from x-ray coherent diffractive imaging projections.  

PubMed

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

Guizar-Sicairos, Manuel; Diaz, Ana; Holler, Mirko; Lucas, Miriam S; Menzel, Andreas; Wepf, Roger A; Bunk, Oliver

2011-10-24

334

Quantitative phase from defocused intensity by image deconvolution  

NASA Astrophysics Data System (ADS)

We present a method for quantitative phase recovery using the axially defocused intensity information based on the phase optical transfer function in defocused situation. The image formation process is linearized by subtraction of two intensity images with equal and opposite defocus distances and quantitative phase information is separated and extracted by solving an inverse problem with Wiener filtering. Experiments confirm the accuracy and stability of the proposed method outperforms the transport-of-intensity reconstruction method.

Zuo, Chao; Chen, Qian; Asundi, Anand

2013-06-01

335

Motion-compensated hand-held common-path Fourier-domain optical coherence tomography probe for image-guided intervention  

NASA Astrophysics Data System (ADS)

A motion-compensated hand-held common-path Fourier-domain optical coherence tomography imaging probe has been developed for image guided intervention during microsurgery. A hand-held prototype instrument was designed and fabricated by integrating an imaging fiber probe inside a stainless steel needle which is attached to the ceramic shaft of a piezoelectric motor housed in an aluminum handle. The fiber probe obtains A-scan images. The distance information was extracted from the A-scans to track the sample surface distance and a fixed distance was maintained by a feedback motor control which effectively compensated hand tremor and target movements in the axial direction. Graphical user interface, real-time data processing, and visualization based on a CPU-GPU hybrid programming architecture were developed and used in the implantation of this system. To validate the system, free-hand optical coherence tomography images using various samples were obtained. The system can be easily integrated into microsurgical tools and robotics for a wide range of clinical applications. Such tools could offer physicians the freedom to easily image sites of interest with reduced risk and higher image quality.

Huang, Yong; Song, Cheol; Liu, Xuan; Kang, Jin U.

336

A new, efficient structure for the short-time Fourier transform, with an application in code-division sonar imaging  

Microsoft Academic Search

Although most applications which use the short-time Fourier transform (STFT) temporally downsample the output, some applications exploit a dense temporal sampling of the STFT. One example, coded-division multiple-beam sonar, is discussed. Given a need for the densely sampled STFT, the complexity of the computation can be reduced from O(N log N) for the general short-time FFT structure to O(N) using

M. Covell; J. Richardson

1991-01-01

337

Phase-retrieval ghost imaging of complex-valued objects  

SciTech Connect

An imaging approach, based on ghost imaging, is reported to recover a pure-phase object or a complex-valued object. Our analytical results, which are backed up by numerical simulations, demonstrate that both the complex-valued object and its amplitude-dependent part can be separately and nonlocally reconstructed using this approach. Both effects influencing the quality of reconstructed images and methods to further improve the imaging quality are also discussed.

Gong Wenlin; Han Shensheng [Key Laboratory for Quantum Optics and Center for Cold Atom Physics of the Chinese Academy of Sciences, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai 201800 (China)

2010-08-15

338

Development of neutron tomography and phase contrast imaging technique  

NASA Astrophysics Data System (ADS)

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.

Kashyap, Y. S.; Agrawal, Ashish; Sarkar, P. S.; Shukla, Mayank; Sinha, Amar

2013-02-01

339

Multiple image encryption based on known-plaintext attack and modified G-S phase retrieval algorithm  

NASA Astrophysics Data System (ADS)

We propose a novel multiple image encryption based on fractional Fourier transform (FRT) and known-plaintext attack with modified Gerchberg-Saxton (G-S) phase retrieval algorithm. Multiple images to be encrypted are encoded into corresponding phase-only masks (POMs) using modified G-S algorithm. These POMs are multiplexed into a single POM, which may be referred to as a general key. The individual keys can be generated with the help of all the POMs. Now a random intensity image is encrypted using double phase encoding in which POM and random phase masks (RPM) are used as keys. For decryption, with the concept of known-plaintext attack using intensity image and RPM as keys, the POM is obtained. With this POM, the original images can be retrieved by using individual keys, and correct orders of FRT. We present simulation results with four different gray-scale images. Numerical simulation results support the proposed idea of the multiple image encryption.

Rajput, Sudheesh K.; Nishchal, Naveen K.

2013-06-01

340

Imaging with a rectangular phase grating applied to displacement metrology  

SciTech Connect

We achieved displacement metrology with a high-amplitude signal by using a rectangular phase grating as the pupil in a grating imaging system. The imaging phenomenon with a pupil transmission grating that has a bilevel profile with a 50% duty ratio is discussed on the basis of the optical transfer function. By optimizing the imaging condition, we obtained high-contrast images with high light power under a magnified or demagnified imaging system. The amplitude of the signal in the displacement measurement was four times higher than that of the conventional grating imaging system with amplitude gratings.

Ohmura, Yoichi; Oka, Toru; Nakashima, Toshiro; Hane, Kazuhiro

2006-03-10

341

The nature of protic ionic liquids in the gas phase revisited: Fourier transform ion cyclotron resonance mass spectrometry study of 1,1,3,3-tetramethylguanidinium chloride.  

PubMed

The sublimation/vaporization of the protic ionic liquid 1,1,3,3-tetramethylguanidinium chloride, [Htmg]Cl, was studied by Fourier transform ion cyclotron resonance mass spectrometry in the temperature range 298-488 K and under a reduced pressure of 3.2 x 10(-6) to 1.5 x 10(-5) Pa. The results show that no charged species are present in the vapor over the condensed phase. Furthermore, ion-molecule reaction studies found no evidence of neutral ion pairs in the gas phase. This indicates that the sublimation/vaporization of [Htmg]Cl conforms to the general mechanism postulated for the distillation of protic ionic liquids, which involves a proton transfer leading to the formation of the neutral acid and base precursors, in this case hydrogen chloride and 1,1,3,3-tetramethylguanidine. PMID:20568799

Vitorino, Joana; Leal, João P; Minas da Piedade, Manuel E; Canongia Lopes, José N; Esperança, José M S S; Rebelo, Luís Paulo N

2010-07-15

342

Introducing a Novel Image Quality Measure for Digital Phase-Contrast-Image Evaluation  

Microsoft Academic Search

\\u000a Recently, detective quantum efficiency (DQE) arising from the concept of signal-to-noise ratio (SNR) has been used for assessing\\u000a digital x-ray imaging systems. Using a phase-shift of x-rays that occurs when passing through an object, digital phase contrast\\u000a imaging (herein referred to as “phase imaging”), which involves magnification, can produce images different from those of\\u000a standard contact imaging (herein referred to

Satoru Matsuo; Hiroshi Fujita; Junji Morishita; Tetsuro Katafuchi

2010-01-01

343

Phase retrieval in X-ray phase-contrast imaging suitable for tomography.  

PubMed

In-line phase-contrast X-ray imaging provides images where both absorption and refraction contribute. For quantitative analysis of these images, the phase needs to be retrieved numerically. There are many phase-retrieval methods available. Those suitable for phase-contrast tomography, i.e., non-iterative phase-retrieval methods that use only one image at each projection angle, all follow the same pattern though derived in different ways. We outline this pattern and use it to compare the methods to each other, considering only phase-retrieval performance and not the additional effects of tomographic reconstruction. We also outline derivations, approximations and assumptions, and show which methods are similar or identical and how they relate to each other. A simple scheme for choosing reconstruction method is presented, and numerical phase-retrieval performed for all methods. PMID:21643293

Burvall, Anna; Lundström, Ulf; Takman, Per A C; Larsson, Daniel H; Hertz, Hans M

2011-05-23

344

Phase Difference Application in Fully PolSAR Images  

NASA Astrophysics Data System (ADS)

The probability density function of each phase angle ?pq in complex PolSAR data, follow hypothesis of strong scattering regime, is uniformly distributed over [ - ? , ? ] and therefore does not contain any information about image terrain properties. But interchannel phase information: 1) co-pol phase (the phase difference between the co-polarised channels HH and VV), 2) cross-pol phase (the phase difference between the cross- polarised channels HH and HV, VV and VH), 3) the phase difference between HV and VH channels, are important in SAR polarimetric data along with the intensity. The area of its application in SAR polarimetric images includes the discrimination between dominant scattering situations, crop classification, moving target indication, oil spill observations, forest parameters estimation. This paper represents a brief review of interchannel phase information application in PolSAR imagery, illustrated by images from SIR-C/X-SAR SLC C- and L-band fully polarimetric SAR data of Moscow region and Baikal Lake region, acquired in 1994/10/09. Speckle reduction is one of the main moments in the image interpretation improvement. But it is almost no difference between polarimetric phase difference not filtered or filtered by Lee polarimetric filter. It's not the case for amplitude information in PolSAR images.

Rodionova, N. V.

2009-04-01

345

The Principle and Images of Phase-Contrast Mammography  

Microsoft Academic Search

The technology of phase-contrast mammography is described from its principle through application to digital mammography. An edge effect due to phase contrast has been formulated with geometric optics for phase-contrast imaging with use of current medical x-ray tubes. The spatial resolutio ni n digital mammography is discussed for design of a phase- contrast digital mammography system. Our empirical study of

Hiromu OHARA; Tomonori GIDO; Akira ISHISAKA; Chika HONDA

346

AO-OCT with reference arm phase shifting for complex conjugate artifact-free imaging of in vivo retinal structures  

NASA Astrophysics Data System (ADS)

We summarize the performance of an AO-OCT system with reference arm phase shifting for complex conjugate artifactfree imaging of in vivo retinal structures. As a complex conjugate artifact removal (CCR) method we used a previously reported technique requiring constant phase shifts between consecutive A-scans. In our system these shifts were generated by continuous beam path-length changes from offsetting the pivot point of the scanning mirror placed in the system reference arm. In order to reconstruct the complex spectral fringe pattern we used Fourier transformation along the transverse axis and a filtering algorithm. The suppression ratio of mirror complex artifact images was assessed based on acquired in vivo CCR AO-OCT images. Finally, potential problems and limitations connected with this acquisition scheme and data processing algorithms are discussed.

Zawadzki, Robert J.; Kim, Dae Yu; Jones, Steven M.; Pilli, Suman; Olivier, Scot S.; Werner, John S.

2011-02-01

347

Metrology for a solar imaging Fourier transform spectrometer working in the far UV: from the instrumental concept to the first experimental results  

NASA Astrophysics Data System (ADS)

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.

Ruiz de Galarreta Fanjul, C.; Bouzit, M.; Appourchaux, T.; Dassas, K.; Viale, T.; Philippon, A.; Vial, J.-C.; Maillard, J.-P.

2012-09-01

348

Spectroscopic Imaging with Prospective Motion Correction and Retrospective Phase Correction  

PubMed Central

Motion-induced artefacts in magnetic resonance spectroscopic imaging are much harder to recognize than in imaging experiments and can therefore lead to erroneous interpretation. A method for prospective motion correction based on an optical tracking system has recently been proposed and has already been successfully applied to single voxel spectroscopy. In this work, the utility of prospective motion correction in combination with retrospective phase correction is evaluated for spectroscopic imaging in the human brain. Retrospective phase correction, based on the interleaved reference scan method, is used to correct for motion-induced frequency shifts and ensure correct phasing of the spectra across the whole spectroscopic imaging slice. It is demonstrated that the presented correction methodology can reduce motion-induced degradation of spectroscopic imaging data.

Lange, Thomas; Maclaren, Julian; Buechert, Martin; Zaitsev, Maxim

2011-01-01

349

Phase and amplitude imaging from noisy images by Kalman filtering.  

PubMed

We propose and demonstrate a computational method for complex-field imaging from many noisy intensity images with varying defocus, using an extended complex Kalman filter. The technique offers dynamic smoothing of noisy measurements and is recursive rather than iterative, so is suitable for adaptive measurements. The Kalman filter provides near-optimal results in very low-light situations and may be adapted to propagation through turbulent, scattering, or nonlinear media. PMID:21369102

Waller, Laura; Tsang, Mankei; Ponda, Sameera; Yang, Se Young; Barbastathis, George

2011-01-31

350

Phase TEM for biological imaging utilizing a Boersch electrostatic phase plate: theory and practice.  

PubMed

A Boersch electrostatic phase plate (BEPP) used in a transmission electron microscope (TEM) system can provide tuneable phase shifts and overcome the low contrast problem for biological imaging. Theoretically, a pure phase image with a high phase contrast can be obtained using a BEPP. However, a currently available TEM system utilizing a BEPP cannot achieve sufficiently high phase efficiency for biological imaging, owing to the practical conditions. The low phase efficiency is a result of the blocking of partial unscattered electrons by BEPP, and the contribution of absorption contrast. The fraction of blocked unscattered beam is related to BEPP dimensions and to divergence of the illumination system of the TEM. These practical issues are discussed in this paper. Phase images of biological samples (negatively stained ferritin) obtained by utilizing a BEPP are reported, and the phase contrast was found to be enhanced by a factor of approximately 1.5, based on the calculation using the Rose contrast criterion. The low gain in phase contrast is consistent with the expectation from the current TEM/BEPP system. A new generation of phase TEM utilizing BEPP and designed for biological imaging with a high phase efficiency is proposed. PMID:19289850

Shiue, Jessie; Chang, Chia-Seng; Huang, Sen-Hui; Hsu, Chih-Hao; Tsai, Jin-Sheng; Chang, Wei-Hau; Wu, Yi-Min; Lin, Yen-Chen; Kuo, Pai-Chia; Huang, Yang-Shan; Hwu, Yeukuang; Kai, Ji-Jung; Tseng, Fan-Gang; Chen, Fu-Rong

2009-03-16

351

Quantitative Phase Imaging in Microscopy Using a Spatial Light Modulator  

Microsoft Academic Search

\\u000a In this chapter, we present a new method capable of recovery of the quantitative phase\\u000a information of microscopic samples. Essentially, a spatial light modulator (SLM)\\u000a and digital image processing are the basics to extract the sample’s phase distribution. The SLM\\u000a produces a set of misfocused images of the input sample at the CCD plane by displaying a set of lenses

Vicente Micó; Javier García; Luis Camacho; Zeev Zalevsky

352

Data Fusion of Lockin-Thermography Phase Images  

Microsoft Academic Search

Lockin-thermography is a valuable tool in non-destructive testing of materials because it provides reliable and easy-to-interpret phase images. This paper presents a way to combine phase images obtained at different lockin-frequencies by using scatter plots. Not only features like defects can be extracted out of the raw data, but also thermal wave parameters like reflection coefficients. The extracted features can

C. Spiessberger; A. Gleiter; G. Busse

353

Lung ventilation- and perfusion-weighted Fourier decomposition magnetic resonance imaging: in vivo validation with hyperpolarized 3He and dynamic contrast-enhanced MRI.  

PubMed

The purpose of this work was to validate ventilation-weighted (VW) and perfusion-weighted (QW) Fourier decomposition (FD) magnetic resonance imaging (MRI) with hyperpolarized (3)He MRI and dynamic contrast-enhanced perfusion (DCE) MRI in a controlled animal experiment. Three healthy pigs were studied on 1.5-T MR scanner. For FD MRI, the VW and QW images were obtained by postprocessing of time-resolved lung image sets. DCE acquisitions were performed immediately after contrast agent injection. (3)He MRI data were acquired following the administration of hyperpolarized helium and nitrogen mixture. After baseline MR scans, pulmonary embolism was artificially produced. FD MRI and DCE MRI perfusion measurements were repeated. Subsequently, atelectasis and air trapping were induced, which followed with FD MRI and (3)He MRI ventilation measurements. Distributions of signal intensities in healthy and pathologic lung tissue were compared by statistical analysis. Images acquired using FD, (3)He, and DCE MRI in all animals before the interventional procedure showed homogeneous ventilation and perfusion. Functional defects were detected by all MRI techniques at identical anatomical locations. Signal intensity in VW and QW images was significantly lower in pathological than in healthy lung parenchyma. The study has shown usefulness of FD MRI as an alternative, noninvasive, and easily implementable technique for the assessment of acute changes in lung function. PMID:22392633

Bauman, Grzegorz; Scholz, Alexander; Rivoire, Julien; Terekhov, Maxim; Friedrich, Janet; de Oliveira, Andre; Semmler, Wolfhard; Schreiber, Laura Maria; Puderbach, Michael

2012-03-05

354

Comparison of Subpixel Phase Correlation Methods for Image Registration.  

National Technical Information Service (NTIS)

The popular phase correlation method (PCM) for image registration has been extended to subpixel accuracy by several alternative algorithms, each claiming accuracies on the order of 0.02 - 0.03 pixels for 256 x 256 images. However, the performance reported...

R. A. Reed

2010-01-01

355

Application of Phase Correction to Improve the Interpretation of Crude Oil Spectra Obtained Using 7 T Fourier Transform Ion Cyclotron Resonance Mass Spectrometry  

NASA Astrophysics Data System (ADS)

In this study, a phase-correction technique was applied to the study of crude oil spectra obtained using a 7 T Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). 7 T FT-ICR MS had not been widely used for oil analysis due to the lower resolving power compared with high field FT-ICR MS. For low field instruments, usage of data that has not been phase-corrected results in an inability to resolve critical mass splits of C3 and SH4 (3.4 mDa), and 13C and CH (4.5 mDa). This results in incorrect assignments of molecular formulae, and discontinuous double bond equivalents (DBE) and carbon number distributions of S1, S2, and hydrocarbon classes are obtained. Application of phase correction to the same data, however, improves the reliability of assignments and produces continuous DBE and carbon number distributions. Therefore, this study clearly demonstrates that phase correction improves data analysis and the reliability of assignments of molecular formulae in crude oil anlayses.

Cho, Yunju; Qi, Yulin; O'Connor, Peter B.; Barrow, Mark P.; Kim, Sunghwan

2013-10-01

356

Fourier Transform Light Scattering of Tissues  

NASA Astrophysics Data System (ADS)

We review the basic principles of light-tissue interaction and common methods of investigation. The mathematical framework for describing weakly scattering regime (the Born approximation) as well as the strong scattering regime (the diffusion equation) are described. Traditional techniques based on polarization, time-resolved, single and multiple scattering are reviewed. We then introduce Fourier transform light scattering (FTLS), which is a recent development from our own laboratory. FTLS is the spatial analogue of Fourier transform spectroscopy, in the sense that it provides angular scattering (spatial frequency) data from phase and amplitude measurements in the spatial (image) domain. We show that FTLS can be used as a diagnostic tool by translating the quantitative phase information into data of clinical relevance. Further, FTLS allows us to extract scattering parameters of the tissue from imaging unlabeled, thin tissue slices, using a relationship which we call the scattering-phase theorem. Using these measurements, FTLS can predict the outcome of many other experiments, including time resolved and enhanced backscattering experiments.

Kim, Taewoo; Sridharan, Shamira; Popescu, Gabriel

357

High Sensitivity Attenuated Total Reflection Fourier Transform Infrared Spectroscopy Study of Ultrathin ZrO2 Films: A Study of Phase Change  

SciTech Connect

Attenuated total reflection fourier transform infrared spectroscopy (FTIR ATR) was performed on ultrathin ZrO2 films as thin as {approx}3.0 nm deposited on silicon. An observed vibrational mode near 710 cm-1 undergoes a very pronounced absorption line shape change, corresponding to a structural phase change, as a function of film thickness and thermal processing. This absorption, attributed to the Eu(LO2) and A2u(LO) modes of tetragonal ZrO2, marks the first experimental measurement and verification of vibrational modes for tetragonal ZrO2 in this spectral range. The FTIR-ATR method shows promise as an extremely sensitive and nondestructive tool for high-kappa dielectric film characterization.

Sayan,S.; Chandler-Horowitz, D.; Nguyen, N.; Ehrstein, J.

2008-01-01

358

Phase Contrast Neutron Imaging using Single and Multiple Pinhole Apertures  

NASA Astrophysics Data System (ADS)

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

Mishra, Kaushal Kishor

359

Thermal wave imaging with phase sensitive modulated thermography  

NASA Astrophysics Data System (ADS)

A technique of thermal wave imaging with phase-sensitive modulated thermography ('thermal wave thermography') is described that combines the advantages of both the low-frequency CW modulation (providing phase angle information and a maximum depth range) and rapid scanning as it is used in the conventional thermographic imaging technique. Compared with the usual thermal wave techniques, the new technique provides an increased depth range at a short time required for imaging. The reason for this is that the stationary thermal wave field is excited on the whole sample simultaneously and monitored sequentially. A diagram of the experimental arrangement for thermal wave thermography is included.

Busse, G.; Wu, D.; Karpen, W.

1992-04-01

360

X-ray phase-contrast imaging: the quantum perspective  

NASA Astrophysics Data System (ADS)

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.

Slowik, J. M.; Santra, R.

2013-08-01

361

Interpretation of phase images of delta-doped layers.  

PubMed

An approach is presented that allows independent determination of the mean inner potential contribution to a phase image of a highly doped layer in a semiconductor measured using off-axis electron holography, in order to quantify the contribution to the recorded phase from the dopant potential alone. The method takes into account the possible presence of both substitutional and interstitial dopant atoms and is used here to analyse an experimental phase image of 12 delta-doped B layers in Si that are separated from each other by <6 nm. PMID:23536698

Cooper, David; Dunin-Borkowski, Rafal E

2013-03-26

362

Quantitative phase imaging using a partitioned detection aperture.  

PubMed

We present a technique to quantitatively image the phase of thin quasi-transparent samples using extended source incoherent illumination and off-axis detection apertures. Our technique is achromatic and polarization independent, requires no active elements, and can be readily adapted to standard bright-field microscopes. We demonstrate our technique by quantitatively reconstructing the phase of cheek cells and a microlens. The light efficient, single-shot nature of our technique enables phase imaging at frame rates that are camera limited. PMID:23027279

Parthasarathy, Ashwin B; Chu, Kengyeh K; Ford, Tim N; Mertz, Jerome

2012-10-01

363

Ultrahigh-speed optical coherence tomography imaging and visualization of the embryonic avian heart using a buffered Fourier Domain Mode Locked laser  

NASA Astrophysics Data System (ADS)

The embryonic avian heart is an important model for studying cardiac developmental biology. The mechanisms that govern the development of a four-chambered heart from a peristaltic heart tube are largely unknown due in part to a lack of adequate imaging technology. Due to the small size and rapid motion of the living embryonic avian heart, an imaging system with high spatial and temporal resolution is required to study these models. Here, an optical coherence tomography (OCT) system using a buffered Fourier Domain Mode Locked (FDML) laser is applied for ultrahigh-speed non-invasive imaging of embryonic quail hearts at 100,000 axial scans per second. The high scan rate enables the acquisition of high temporal resolution 2D datasets (195 frames per second or 5.12 ms between frames) and 3D datasets (10 volumes per second). Spatio-temporal details of cardiac motion not resolvable using previous OCT technology are analyzed. Visualization and measurement techniques are developed to non-invasively observe and quantify cardiac motion throughout the brief period of systole (less than 50 msec) and diastole. This marks the first time that the preseptated embryonic avian heart has been imaged in 4D without the aid of gating and the first time it has been viewed in cross section during looping with extremely high temporal resolution, enabling the observation of morphological dynamics of the beating heart during systole.

Jenkins, M. W.; Adler, D. C.; Gargesha, M.; Huber, R.; Rothenberg, F.; Belding, J.; Watanabe, M.; Wilson, D. L.; Fujimoto, J. G.; Rollins, A. M.

2007-05-01

364

Automatic evaluation of nickel alloy secondary phases from SEM images.  

PubMed

Quantitative metallography is a technique to determine and correlate the microstructures of materials with their properties and behavior. Generic commercial image processing and analysis software packages have been used to quantify material phases from metallographic images. However, these all-purpose solutions also have some drawbacks, particularly when applied to segmentation of material phases. To overcome such limitations, this work presents a new solution to automatically segment and quantify material phases from SEM metallographic images. The solution is based on a neuronal network and in this work was used to identify the secondary phase precipitated in the gamma matrix of a Nickel base alloy. The results obtained by the new solution were validated by visual inspection and compared with the ones obtained by a commonly used commercial software. The conclusion is that the new solution is precise, reliable and more accurate and faster than the commercial software. PMID:21181708

de Albuquerque, Victor Hugo C; Silva, Cleiton Carvalho; Menezes, Thiago Ivo de S; Farias, Jesualdo Pereira; Tavares, João Manuel R S

2011-01-01

365

Full-wave approach for x-ray phase imaging.  

PubMed

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

Sung, Yongjin; Sheppard, Colin J R; Barbastathis, George; Ando, Masami; Gupta, Rajiv

2013-07-29

366

Image reconstruction of steel reinforcing bars in concrete using Fourier-domain interpolation applied to a sparsely populated data set  

Microsoft Academic Search

High-resolution image generation of bars in concrete using a single coil scanning inductive sensor is a time consuming process. This paper presents a method of generating the image using a sparsely populated data set (SPDS), obtained from a reduced number of scan lines, whose use is justifies by an analysis of the sensor spatial frequency response. Three methods are discussed:

Muhammad A. M. Zaid; Patrick Gaydecki; Sung Quek; Graham Miller; Bosco Fernandes

2003-01-01

367

Phase contrast neutron imaging at the PULSTAR reactor  

NASA Astrophysics Data System (ADS)

Non-interferometric phase contrast effects have been shown to enhance material edges in neutron images. The achieved contrast enhancement in the image depends upon the neutron coherent scattering lengths of the materials present in the object and the degree of spatial coherence of the neutron beam. Spatial coherence of the beam is achieved using design-based spatial filters, a large L/d ratio (˜10,000) and low average neutron energy. Physically, a large L/d ratio is realized by a pinhole neutron source thereby significantly reducing the neutron beam intensity at the image plane. Thus, performance of such imaging exercises at low/medium intensity neutron sources is associated with additional design considerations that are not needed at high intensity neutron sources, where it has been demonstrated. In the present work, phase contrast neutron imaging was conducted using a suitably designed collimator at the 1-MWth PULSTAR reactor located at North Carolina State University (NCSU). Results of the imaging exercises that depict phase contrast edge enhancement are being presented along with the collimator design. Digital image plate detectors were used to capture images with a range of exposure times between 45 and 120 min.

Mishra, Kaushal K.; Hawari, Ayman I.

2011-10-01

368

Ghost imaging with XY phase series space light modulator  

NASA Astrophysics Data System (ADS)

Ghost imaging has emerged a decade ago as a new imaging technique. Its feature is the image will appear on the optical path, which never passes through the object actually. In this paper, we will give an overview of quantum imaging, include the experiments with two-photon entanglement state source generated by spontaneous parametric down conversion, as well as with pseudo-thermal light. Then we will show our ghost imaging experiment scheme with the pseudo-thermal light source. We obtain the pseudo-thermal source by using a XY Phase Series Spatial Light Modulator (supplied by BNS company) to modulate the laser light. This spatial light modulator changes the phase of the output light field by controlling the loading element on every pixel.

Qin, Jiexin; Liu, Shichao; Huang, Genghua; Shen, Xia; Han, Shensheng; Shu, Rong

2010-11-01

369

Phase-Based Road Detection in Multi-Source Images  

SciTech Connect

The problem of robust automatic road detection in remotely sensed images is complicated by the fact that the sensor, spatial resolution, acquisition conditions, road width, road orientation and road material composition can all vary. A novel technique for detecting road pixels in multi-source remotely sensed images based on the phase (i.e., orientation or directional) information in edge pixels is described. A very dense map of edges extracted from the image is separated into channels, each containing edge pixels whose phases lie within a different range of orientations. The edge map associated with each channel is de-cluttered. A map of road pixels is formed by re-combining the de-cluttered channels into a composite edge image which is itself then separately de-cluttered. Road detection results are provided for DigitalGlobe and TerraServerUSA images. Road representations suitable for various applications are then discussed.

Sengupta, S K; Lopez, A S; Brase, J M; Paglieroni, D W

2004-06-16

370

Phase contrast without phase plates and phase rings-optical solutions for improved imaging of phase structures.  

PubMed

Using the optical methods described, phase specimens can be observed with a modified light microscope in enhanced clarity, purified from typical artifacts which are apparent in standard phase contrast illumination. In particular, haloing and shade-off are absent, lateral and vertical resolution are maximized and the image quality remains constant even in problematic preparations which cannot be well examined in normal phase contrast, such as specimens beyond a critical thickness or covered by obliquely situated cover slips. The background brightness and thus the range of contrast can be continuously modulated and specimens can be illuminated in concentric-peripheral, axial or paraxial light. Additional contrast effects can be achieved by spectral color separation. Normal glass or mirror lenses can be used; they do not need to be fitted with a phase plate or a phase ring. The methods described should be of general interest for all disciplines using phase microscopy. Microsc. Res. Tech., 76:1050-1056, 2013. © 2013 Wiley Periodicals, Inc. PMID:23913620

Piper, Timm; Piper, Jörg

2013-07-30

371

Image processing for phase imperfections in electron holography.  

PubMed

In electron holography, an abrupt reversal of contrast from white to black may occur in a digitally reconstructed phase image, potentially resulting in inaccurate phase information. There are two types of such abrupt reversals. One is a phase jump of 2? during the digital reconstruction process; in this case, the phase can be unwrapped and smoothly connected for such a jump. The other is caused by the disconnection of interference fringes due to weak electron-wave amplitude in some areas of the specimen. We propose a searching technique for finding the disconnection points based on mathematical morphology and then correcting the interference fringes. Finally, a comparatively accurate phase information image is reconstructed from the corrected interference fringes. PMID:23752675

Li, Wei; Zhang, Jianhui; Tanji, Takayoshi

2013-06-01

372

Phase transfer function based method to alleviate image artifacts in wavefront coding imaging system  

NASA Astrophysics Data System (ADS)

Wavefront coding technique can extend the depth of filed (DOF) of the incoherent imaging system. Several rectangular separable phase masks (such as cubic type, exponential type, logarithmic type, sinusoidal type, rational type, et al) have been proposed and discussed, because they can extend the DOF up to ten times of the DOF of ordinary imaging system. But according to the research on them, researchers have pointed out that the images are damaged by the artifacts, which usually come from the non-linear phase transfer function (PTF) differences between the PTF used in the image restoration filter and the PTF related to real imaging condition. In order to alleviate the image artifacts in imaging systems with wavefront coding, an optimization model based on the PTF was proposed to make the PTF invariance with the defocus. Thereafter, an image restoration filter based on the average PTF in the designed depth of field was introduced along with the PTF-based optimization. The combination of the optimization and the image restoration proposed can alleviate the artifacts, which was confirmed by the imaging simulation of spoke target. The cubic phase mask (CPM) and exponential phase mask (EPM) were discussed as example.

Mo, Xutao; Wang, Jinjiang

2013-09-01

373

Optimization of image recording distances for quantitative X-ray in-line phase contrast imaging.  

PubMed

Compared to phase retrieval from single sample-to-detector distance (SDD) image, phase retrieval with multiple SDD images could improve the precision in quantitative X-ray in-line phase contrast imaging (QXIPCI). Among all the related phase retrieval approaches, the two-SDD-image-based one is the simplest and well compromises between precision and dose. However, how to optimize the recording distances for the two images to achieve highest precision, remains unsolved. In this paper, the problem was investigated systematically based on digital simulation and related experiments. Spectral correlation degree (SCD) is introduced to evaluate the pertinence between the two SDD images. The simulation results show that the highest retrieving precision could be obtained while the SDD of the second image is three times that of the first image. The best retrieval could be achieved when SDD of the first image is selected properly, meanwhile the SCD occurs with a typical damping oscillation. Experiments, carried out at the X-ray imaging beamline of SSRF, demonstrated the simulation results. PMID:21369246

Ren, Yuqi; Chen, Can; Chen, Rongchang; Zhou, Guangzhao; Wang, Yudan; Xiao, Tiqiao

2011-02-28

374

Benchtop phase-contrast X-ray imaging.  

PubMed

Clinical radiography has traditionally been based on contrast obtained from absorption when X-rays pass through the body. The contrast obtained from traditional radiography can be rather poor, particularly when it comes to soft tissue. A wide range of media of interest in materials science, biology and medicine exhibit very weak absorption contrast, but they nevertheless produce significant phase shifts with X-rays. The use of phase information for imaging purposes is therefore an attractive prospect. Some of the X-ray phase-contrast imaging methods require highly monochromatic plane wave radiation and sophisticated X-ray optics. However, the propagation-based phase-contrast imaging method adapted in this paper is a relatively simple method to implement, essentially requiring only a microfocal X-ray tube and electronic detection. In this paper, we present imaging results obtained from two different benchtop X-ray sources employing the free space propagation method. X-ray phase-contrast imaging provides higher contrast in many samples, including biological tissues that have negligible absorption contrast. PMID:17714951

Gundogdu, O; Nirgianaki, E; Che Ismail, E; Jenneson, P M; Bradley, D A

2007-07-22

375

Self-focusing media using graded photonic crystals: Focusing, Fourier transforming and imaging, directive emission, and directional cloaking  

Microsoft Academic Search

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

Borislav Vasic

2011-01-01

376

MR image segmentation of the knee bone using phase information.  

PubMed

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

Bourgeat, Pierrick; Fripp, Jurgen; Stanwell, Peter; Ramadan, Saadallah; Ourselin, Sébastien

2007-03-30

377

Robustness of phase retrieval methods in x-ray phase contrast imaging: A comparison  

PubMed Central

Purpose: The robustness of the phase retrieval methods is of critical importance for limiting and reducing radiation doses involved in x-ray phase contrast imaging. This work is to compare the robustness of two phase retrieval methods by analyzing the phase maps retrieved from the experimental images of a phantom. Methods: Two phase retrieval methods were compared. One method is based on the transport of intensity equation (TIE) for phase contrast projections, and the TIE-based method is the most commonly used method for phase retrieval in the literature. The other is the recently developed attenuation-partition based (AP-based) phase retrieval method. The authors applied these two methods to experimental projection images of an air-bubble wrap phantom for retrieving the phase map of the bubble wrap. The retrieved phase maps obtained by using the two methods are compared. Results: In the wrap’s phase map retrieved by using the TIE-based method, no bubble is recognizable, hence, this method failed completely for phase retrieval from these bubble wrap images. Even with the help of the Tikhonov regularization, the bubbles are still hardly visible and buried in the cluttered background in the retrieved phase map. The retrieved phase values with this method are grossly erroneous. In contrast, in the wrap’s phase map retrieved by using the AP-based method, the bubbles are clearly recovered. The retrieved phase values with the AP-based method are reasonably close to the estimate based on the thickness-based measurement. The authors traced these stark performance differences of the two methods to their different techniques employed to deal with the singularity problem involved in the phase retrievals. Conclusions: This comparison shows that the conventional TIE-based phase retrieval method, regardless if Tikhonov regularization is used or not, is unstable against the noise in the wrap’s projection images, while the AP-based phase retrieval method is shown in these experiments to be superior to the TIE-based method for the robustness in performing the phase retrieval.

Yan, Aimin; Wu, Xizeng; Liu, Hong

2011-01-01

378

Depth-Dependent Anisotropies of Amides and Sugar in Perpendicular and Parallel Sections of Articular Cartilage by Fourier Transform Infrared Imaging (FTIRI)  

PubMed Central

Full thickness blocks of canine humeral cartilage were microtomed into both perpendicular sections and a series of 100 parallel sections, each 6 ?m thick. Fourier Transform Infrared Imaging (FTIRI) was used to image each tissue section eleven times under different infrared polarizations (from 0° to 180° polarization states in 20° increments and with an additional 90° polarization), at a spatial resolution of 6.25 ?m and a wavenumber step of 8 cm?1. With increasing depth from the articular surface, amide anisotropies increased in the perpendicular sections and decreased in the parallel sections. Both types of tissue sectioning identified a 90° difference between amide I and amide II in the superficial zone of cartilage. The fibrillar distribution in the parallel sections from the superficial zone was shown to not be random. Sugar had the greatest anisotropy in the upper part of the radial zone in the perpendicular sections. The depth-dependent anisotropic data were fitted with a theoretical equation that contained three signature parameters, which illustrate the arcade structure of collagens with the aid of a fibril model. Infrared imaging of both perpendicular and parallel sections provides the possibility of determining the three-dimensional macromolecular structures in articular cartilage. Being sensitive to the orientation of the macromolecular structure in healthy articular cartilage aids the prospect of detecting the early onset of the tissue degradation that may lead to pathological conditions such as osteoarthritis.

Xia, Yang; Mittelstaedt, Daniel; Ramakrishnan, Nagarajan; Szarko, Matthew; Bidthanapally, Aruna

2010-01-01

379

Measurement of drug and macromolecule diffusion across atherosclerotic rabbit aorta ex vivo by attenuated total reflection-Fourier transform infrared imaging  

NASA Astrophysics Data System (ADS)

Diffusion of two model drugs-benzyl nicotinate and ibuprofen-and the plasma macromolecule albumin across atherosclerotic rabbit aorta was studied ex vivo by attenuated total reflection-Fourier transform infrared (ATR-FTIR) imaging. Solutions of these molecules were applied to the endothelial surface of histological sections of the aortic wall that were sandwiched between two impermeable surfaces. An array of spectra, each corresponding to a specific location in the section, was obtained at various times during solute diffusion into the wall and revealed the distribution of the solutes within the tissue. Benzyl nicotinate in Ringer's solution showed higher affinity for atherosclerotic plaque than for apparently healthy tissue. Transmural concentration profiles for albumin demonstrated its permeation across the section and were consistent with a relatively low distribution volume for the macromolecule in the middle of the wall. The ability of albumin to act as a drug carrier for ibuprofen, otherwise undetected within the tissue, was demonstrated by multivariate subtraction image analysis. In conclusion, ATR-FTIR imaging can be used to study transport processes in tissue samples with high spatial and temporal resolution and without the need to label the solutes under study.

Palombo, Francesca; Danoux, Charlène B.; Weinberg, Peter D.; Kazarian, Sergei G.

2009-07-01

380

Subtle Morphological Changes in the Mandible of Tabby Mice Revealed by Micro-CT Imaging and Elliptical Fourier Quantification.  

PubMed

X-linked hypohidrotic ectodermal dysplasia (XLHED) is a genetic disorder due to a mutation of the EDA gene and is mainly characterized by an impaired formation of hair, teeth and sweat glands, and craniofacial dysmorphologies. Although tooth abnormalities in Tabby (Ta) mutant mice - the murine model of XLHED - have been extensively studied, characterization of the craniofacial complex, and more specifically the mandibular morphology has received less attention. From 3D micro-CT reconstructions of the left mandible, the mandibular outline observed in lateral view, was quantified using 2D elliptical Fourier analysis. Comparisons between Ta specimens and their wild-type controls were carried out showing significant shape differences between mouse strains enabling a clear distinction between hemizygous Ta specimens and the other mouse groups (WT and heterozygous Eda(Ta/+) specimens). Morphological differences associated with HED correspond not only to global mandibular features (restrained development of that bone along dorsoventral axis), but also to subtle aspects such as the marked backward projection of the coronoid process or the narrowing of the mandibular condylar neck. These modifications provide for the first time, evidence of a predominant effect of the Ta mutation on the mandibular morphology. These findings parallel the well described abnormalities of jugal tooth row and skeletal defects in Ta mice, and underline the role played by EDA-A in the reciprocal epithelial-mesenchymal interactions that are of critical importance in normal dental and craniofacial development. PMID:21541253

Bornert, Fabien; Choquet, Philippe; Gros, Catherine I; Aubertin, Gaelle; Perrin-Schmitt, Fabienne; Clauss, François; Lesot, Hervé; Constantinesco, André; Schmittbuhl, Matthieu

2011-04-20

381

Rotating vortex imaging implemented by a quantized spiral phase modulation  

NASA Astrophysics Data System (ADS)

We demonstrate both theoretically and experimentally that a spiral mask with a finite number of discrete phase levels allows a defocusing induced rotation of the point spread function in the vortex imaging. Two experimental configurations based on a spiral phase modulation of light and a spiral filtering of the spatial spectrum are studied in a unified theoretical treatment. The rotating point spread functions are analyzed in detail for imaging realized by the vortex lens and the 4-f system used in the spiral phase contrast microscopy. The theoretical results are verified by experiments using a spatial light modulator. The method is applicable to a precise focusing and optical imaging allowing depth estimation from diffracted rotation. Apart from implementation simplicity, the main advantages of the method are high energy efficiency, a possibility to operate with either complex amplitude or spatial spectrum of light and variability allowing a simple control of number of lobes of the point spread function.

Baránek, M.; Bouchal, Z.

2013-03-01

382

Phase information contained in meter-scale SAR images  

NASA Astrophysics Data System (ADS)

The properties of single look complex SAR satellite images have already been analyzed by many investigators. A common belief is that, apart from inverse SAR methods or polarimetric applications, no information can be gained from the phase of each pixel. This belief is based on the assumption that we obtain uniformly distributed random phases when a sufficient number of small-scale scatterers are mixed in each image pixel. However, the random phase assumption does no longer hold for typical high resolution urban remote sensing scenes, when a limited number of prominent human-made scatterers with near-regular shape and sub-meter size lead to correlated phase patterns. If the pixel size shrinks to a critical threshold of about 1 meter, the reflectance of built-up urban scenes becomes dominated by typical metal reflectors, corner-like structures, and multiple scattering. The resulting phases are hard to model, but one can try to classify a scene based on the phase characteristics of neighboring image pixels. We provide a "cooking recipe" of how to analyze existing phase patterns that extend over neighboring pixels.

Datcu, Mihai; Schwarz, Gottfried; Soccorsi, Matteo; Chaabouni, Houda

2007-11-01

383

Phased array ultrasound imaging through planar tissue layers.  

PubMed

Conventional ultrasound imaging devices are designed based on the assumption of a homogeneous tissue medium of constant acoustic velocity = 1540 m/sec. However, the body consists of tissue layers of varying thicknesses and velocities which range from 1470 m/sec in fat to 3200 m/sec in skull bone. Refraction effects from these layers degrade ultrasound image quality. In this paper, pulse-echo ultrasound imaging is modeled as imaging an organ of interest through an intervening planar tissue layer, such as liver through fat in the abdomen or brain through skull bone in the adult head. Refraction effects from planar tissue layer interfaces are analyzed using Snell's law and measured using phantoms. We also introduce an on-line phased array correction technique based on planar tissue layers to restore ultrasound image quality. We conclude that fat/organ planar interfaces do not degrade image quality significantly. However, refraction effects at a skull/brain planar interface degrades resolution and target acquisition and introduces geometric distortion. Our plane layer phased array correction technique significantly improves image quality in phantoms through lucite aberrators and improves adult cephalic ultrasound image quality when used through the top of the adult skull. The correction technique is robust even in the presence of inaccurate estimates of skull thickness. PMID:3962008

Smith, S W; Trahey, G E; von Ramm, O T

1986-03-01

384

Dispersive solid-phase extraction for in-sorbent Fourier-transform infrared detection and identification of nerve agent simulants in analysis for verification of chemical weapon convention.  

PubMed

The combination of dispersive solid-phase extraction (DSPE) and Fourier-transform infrared (FTIR) spectroscopy is presented for detection and quantification of markers and simulants of nerve agents. Hydrophilic-lipophilic balance (HLB) sorbent was used for extraction and enrichment of organophosphonates from water. When the extraction efficiency of DSPE was compared with that of conventional solid-phase extraction (SPE), DSPE was more efficient. Extraction conditions such as extraction time, and type and quantity of sorbent material were optimized. In DSPE, extracted analytes are detected and quantified on the sorbent using FTIR as analytical technique. Absorbance in FTIR due to P-O-C stretching was used for detection and quantification. Infrared absorbance of different analytes were compared by determining their molar absorptivities (? (max)). Quantitative analyses were performed employing modified Beer's law, and relative standard deviations (RSDs) for intraday repeatability and interday reproducibility were found to be in the range 0.30-0.90% and 0.10-0.80% respectively. The limit of detection (LOD) was 5-10 ?g?mL(-1). The applicability of the method was tested with an unknown sample prepared by mimicking the sample obtained in an international official proficiency test. PMID:21058018

Garg, Prabhat; Pardasani, Deepak; Mazumder, Avik; Purohit, Ajay; Dubey, D K

2010-11-08

385

Automated Galaxy Morphology: A Fourier Approach  

NASA Astrophysics Data System (ADS)

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% of the variance in many of these Fourier profiles may be characterized in as few as three principal components and that 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% confidence level and can identify the Hubble type with a 1 ? 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 signal-to-noise ratio on the quality of morphological information predicted by these classifiers.

Odewahn, S. C.; Cohen, S. H.; Windhorst, R. A.; Philip, Ninan Sajeeth

2002-04-01

386

2-D phase contrast imaging of turbulence structure on LHD  

Microsoft Academic Search

CO2 laser-based phase contrast imaging (PCI) equipped with a 6 by 8 element two-dimensional (2-D) array of photoconductors is used on the large helical device (LHD) for studying plasma density microfluctuations. Observing 2-D structures of turbulence and strong magnetic shear along the viewing line on LHD permit conversion of a 2-D-PCI image to a 2-D picture of the radial distribution

Leonid N. Vyacheslavov; K. Tanaka; A. L. Sanin; K. Kawahata; C. Michael; T. Akiyama

2005-01-01

387

Detection of Pathological Cells in Phase Contrast Cytological Images  

Microsoft Academic Search

This paper presents a practical combination of image processing and pattern recognition techniques in order to identify pathological\\u000a and atypical cells in phase contrast cytological images. The algorithms involved in the processing cover: oriented edge detection,\\u000a ridge following, contour grouping and ellipse fitting. The Hough Transform and other techniques are discussed for comparison.\\u000a Various pattern recognition techniques are tested and

Marcin Smereka; Grzegorz Glab

2006-01-01

388

Phase-sensitive near-field imaging of metal nanoparticles  

NASA Astrophysics Data System (ADS)

We report on the near-field imaging of silver nanoparticles using an aperture-type near-field microscope operated in illumination mode. The nanoparticles are imaged as interference patterns, due to far-field superposition of the optical fields emitted from the tip and elastically scattered from localized surface plasmons (SP). Aperture-type probe can thus be used to obtain information on the phase shift associated with localized SP coupling at the illumination wavelength.

Prikulis, J.; Xu, H.; Gunnarsson, L.; Kall, M.; Olin, H.

2002-11-01

389

A Phased Array Coil for Human Cardiac Imaging  

PubMed Central

A prototype cardiac phased array receiver coil was constructed that comprised a cylindrical array and a separate planar array. Both arrays had two coil loops with the same coil dimensions. Data acquisition with the cylindrical array placed on the human chest, and the planar array placed under the back, yielded an overall enhancement of the signal-to-noise ratio (SNR) over the entire heart by a factor of 1.1–2.85 over a commercially available flexible coil and a commercially available four-loop planar phased array coil. This improvement in SNR can be exploited in cardiac imaging to increase the spatial resolution and reduce the image acquisition time.

Constantinides, Chris D.; Westgate, Charles R.; O'Dell, Walter G.; Zerhouni, Elias A.; McVeigh, Elliot R.

2007-01-01

390

Deconvolution microscopy of living cells for phase-contrast imaging  

NASA Astrophysics Data System (ADS)

The goal of deconvolution microscopy for phase-contrast imaging is to reassign the optical blur to its original position and to reduce statistical noise, thus visualizing the cellular structures of living cells in three dimensions and at subresolution scale. The major features of this technology for a phase-contrast microscopy are discussed through a series of theoretical analyses. A few of possible sources of aberrations and image degradation processes are presented. The theoretical and experimental results have shown that deconvolution microscopy can enhance resolution and contrast by either subtracting or reassigning out-of-focus blur.

Cheng, Guanxiao; Xu, Ping; Sun, Zhilong; Hong, Chunquan; Li, Zelin

2013-05-01

391

Phase contrast imaging with micro focus x-ray tube  

NASA Astrophysics Data System (ADS)

Now the phase-contrast (PC) radiography with monochromatic synchmtron radiation sources is very promising for use in non-destructive industrial control, medical and biological X-ray imaging. Unfortunately synchrotron sources are rather expensive for laboratory practice. We are developing a phase-contrast imaging with a micro focus X-ray tube. We performed numerical calculations with Fresnel-Kirchhgoff formalism to obtain values of PC-signals taking into account polychromatic nature of X-ray radiation, a finite size of a source, and a finite resolution of a detector including spectral sensitivity of the detector. We conducted experiments with a micro focus X-ray tube to find absolute values of PC signals for some models of biological tissue and technical materials in presence of scattering X-rays that emerge from the object. By means of simple set of the experimental arrangement it is possible to obtain the phase-contrast image map of the boundaries between regions with the density difference of order ~1 g/cm3. Under experimental conditions the minimal detected PC-signal is found for the plastic fiber 45 tm in diameter. Examples ofthe X-ray PC-images of fishes, images of air bubbles and ribs, slag inclusions in joint weld of Al-Li alloy materials, and images of sapphire microspheres for cellular metallic structures are presented.

Shovkun, V. Y.; Kumakhov, M. A.

2005-07-01

392

Phase-unwrapping algorithm for images with high noise content based on a local histogram  

Microsoft Academic Search

We present a robust algorithm of phase unwrapping that was designed for use on phase images with high noise content. We proceed with the algorithm by first identifying regions with continuous phase values placed between fringe boundaries in an image and then phase shifting the regions with respect to one another by multiples of 2pi to unwrap the phase. Image

Jaime Meneses; Tijani Gharbi; Philippe Humbert

2005-01-01

393

Phase shifting calibrated with digital image correlation method  

NASA Astrophysics Data System (ADS)

Three-dimensional (3D) shape measurement can be accurately performed using sinusoid grating projection. However, the projection technique requires very accurate phase shifting of the grating. A method for phase shifting calibration which utilizes gray value correlation of image patterns is presented. The method enables calibration to be performed at sub-pixel accuracy. Experiments were carried out to verify the proposed calibration method.

Jiang, Ming; Tam, H. Y.; He, Xiao Yuan

2005-04-01

394

Whole-cell phase contrast imaging at the nanoscale using Fresnel Coherent Diffractive Imaging Tomography  

NASA Astrophysics Data System (ADS)

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.

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.

2013-07-01

395

Quantitative radiography of magnetic fields using neutron spin phase imaging.  

PubMed

We report on a novel neutron radiography technique that uses the Ramsey principle, a method similar to neutron spin echo. For the first time quantitative imaging measurements of magnetic objects and fields could be performed. The strength of the spin-dependent magnetic interaction is detected by a change in the Larmor precession frequency of the neutron spins. Hence, one obtains in addition to the normal attenuation radiography image a so-called neutron spin phase image, which provides a two-dimensional projection of the magnetic field integrated over the neutron flight path. PMID:19392450

Piegsa, F M; van den Brandt, B; Hautle, P; Kohlbrecher, J; Konter, J A

2009-04-09

396

Phase-space formulation for phase-contrast x-ray imaging  

SciTech Connect

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.

Wu Xizeng; Liu Hong

2005-10-01

397

Phase-Sensitive X-ray Imaging of Synovial Joints  

PubMed Central

Objective To test the efficacy of phase-sensitive x-ray imaging for intact synovial joints, whereby refraction effects, along with the attenuation of conventional radiography, can be exploited. Design Intact cadaveric human knee joints were imaged, in the computed tomographic mode, using an analyzer based x-ray system at the National Synchrotron Light Source, Brookhaven National Laboratory. A collimated fan beam of 51 keV X-rays was prepared by a silicon [1,1,1 reflection] double-crystal monochromator. The x-ray beam transmitted through the specimen was imaged after diffraction in the vertical plane by means of the analyzer crystal with the analyzer crystal tuned to its half-reflectivity point (6.5 microradians). A two-dimensional filtered backprojection (FBP) algorithm was used for reconstructing transverse slices of images. Results The resulting images demonstrate simultaneous soft-tissue and bone contrast at a level that has not been achieved previously. Identifiable structures include articular cartilage, cruciate ligaments, loose connective tissue, menisci, and chondrocalcinosis. Conclusion Phase-sensitive x-ray imaging using an analyzer-based system renders exceptionally high quality images of soft and hard tissues within synovial joints, with high contrast and resolution, and thus holds promise for the eventual clinical utility.

Li, Jun; Zhong, Zhong; Connor, Dean; Mollenhauer, Jorgen; Muehleman, Carol

2009-01-01

398

Phase relief imaging with confocal laser scanning system  

NASA Astrophysics Data System (ADS)

Confocal laser scanning microscopy (CLSM) has become one of the most important biomedical research tools today due to its noninvasive and 3-D abilities. It enables imaging in living tissue with better resolution and contrast, and plays a growing role among microscopic techniques utilized for investigating numerous biological problems. In some cases, the sample was phase-sensitive, thus we introduce a novel method named laser oblique scanning optical microscopy (LOSOM) which could obtain a relief image in transparent sample directly. Through the LOSOM system, mouse kidney and HeLa cells sample were imaged and 10x, 20x and 40x magnify objective imaging results were realized respectively. Also, we compared the variation of pinhole size versus imaging result. One major parameters of LOSOM is the distance between fluorescence medium and the sample. Previously, this distance was set to 1.2 mm, which is the thickness of the slide. The experiment result showed that decreasing d can increase the signal level for LOSOM phase-relief imaging. We have also demonstrated the application of LOSOM in absorption imaging modality, when the specimen is non-transparent.

Peng, Tong; Xie, Hao; Ding, Yichen; Xi, Peng

2013-02-01

399

Direct phase retrieval  

Microsoft Academic Search

A direct, noniterative approach to retrieving a multidimensional complex image (i.e., its phase can vary from pixel to pixel) from the magnitude of its Fourier transform is developed. The uniqueness of the reconstruction is shown to be a direct consequence of the existence of zero surfaces or sheets in the multidimensional z transforms of the image. The analytic properties of

W. Fright; R. Bates

1987-01-01

400

Evaluation of physical image characteristics of phase contrast mammography  

NASA Astrophysics Data System (ADS)

Recently, the system called PCM (phase contrast mammography) came to be applied to clinical examinations. The PCM images are acquired as 1.75x-magnified images using small focal spot, then reduced to real object's size by image processing. The PCM images had the feature that edges of objects were enhanced. It was reported that the edges were enhanced because of refraction of X rays. We measured physical image characteristics of the PCM, to compare image characteristics of the PCM with those of a conventional mammography. Specifically, response characteristics to objects and noise characteristics in the spatial frequency domain were measured. As the results, compared with the conventional mammography, response characteristics of the PCM were high. If the placement conditions of objects were changed, response characteristics were also changed. And if the shape of objects was changed, response characteristics also were changed. Noise characteristics of the PCM were better than those of the conventional mammography. Furthermore, in order to investigate why edges of objects in the PCM images were enhanced, we simulated image profiles which would be obtained if X rays were refracted. And, we found the possibility that edge enhancements of the PCM images were based on refraction of X rays.

Yamazaki, Asumi; Ichikawa, Katushiro; Kodera, Yoshie

2007-03-01

401

Holographic digital data storage using phase- modulated pixels  

Microsoft Academic Search

We propose and demonstrate the use of phase images for holographic data storage. Use of phase images as input leads to uniform diffraction efficiency of multiplexed data pages. Use of binary phase-based data pages with 0 and p phase changes produces uniform spectral distribution at the Fourier plane. This in turn facilitates better recording of higher spatial frequencies. We experimentall

Renu John; Joby Joseph; Kehar Singh

2004-01-01

402

Effect of Ingested Tungsten Oxide (WOx) Nanofibers on Digestive Gland Tissue of Porcellio scaber (Isopoda, Crustacea): Fourier Transform Infrared (FTIR) Imaging.  

PubMed

Tungsten nanofibers are recognized as biologically potent. We study deviations in molecular composition between normal and digestive gland tissue of WOx nanofibers (nano-WOx) fed invertebrate Porcellio scaber (Iosopda, Crustacea) and revealed mechanisms of nano-WOx effect in vivo. Fourier Transform Infrared (FTIR) imaging performed on digestive gland epithelium was supplemented by toxicity and cytotoxicity analyses as well as scanning electron microscopy (SEM) of the surface of the epithelium. The difference in the spectra of the Nano-WOx treated and control cells showed up in the central region of the cells and were related to lipid peroxidation, and structural changes of nucleic acids. The conventional toxicity parameters failed to show toxic effects of nano-WOx, whereas the cytotoxicity biomarkers and SEM investigation of digestive gland epithelium indicated sporadic effects of nanofibers. Since toxicological and cytological measurements did not highlight severe effects, the biochemical alterations evidenced by FTIR imaging have been explained as the result of cell protection (acclimation) mechanisms to unfavorable conditions and indication of a nonhomeostatic state, which can lead to toxic effects. PMID:23952740

Novak, Sara; Drobne, Damjana; Vaccari, Lisa; Kiskinova, Maya; Ferraris, Paolo; Birarda, Giovanni; Remškar, Maja; Ho?evar, Matej

2013-09-10

403

Monitoring the pH-Dependent Oximation of Methyl Ethyl Ketone and Benzaldehyde by in situ Fourier Transform IR Spectroscopy in a Heterogeneous Liquid-Liquid Two-Phase System  

Microsoft Academic Search

In situ Fourier transform IR spectroscopy was a useful tool in monitoring the pH-dependent and two-step oximation of methyl ethyl ketone and benzaldehyde in a liquid–liquid two-phase system, one phase of which was water. Carrying out the oximations at pH 8, the oximation was complete within 45 min and the corresponding carbonyl compound–hydroxylamine adduct (2) could be detected as an intermediate,

Gyorgy Keglevich; Istvan Csontos; Nikolett Szilagyi

2009-01-01

404

The potential role of Fourier transform infrared spectroscopy and imaging in cancer diagnosis incorporating complex mathematical methods.  

PubMed

Infrared spectroscopy and imaging technology can provide new diagnostic capabilities for cancer research applications and to physicians directly involved in patient treatment. A methodology that permits the phenotypical description of cells and tissues is introduced, as well as a variety of new evaluation techniques that allow researchers and physicians to evaluate the infrared data at different levels of sophistication. The detection of cell alterations in the case of Chronic Lymphocytic Leukemia (CLL) demonstrates the capability of infrared spectroscopy to identify and stage this type of cancer, providing new prospects for diagnosis and treatment. The pathological study of oral tissue affected by Squamous Cell Carcinoma (SCC) illustrates the potential of Infrared Spectroscopy and Imaging for tissue diagnosis and cancer staging based in altered cell biochemistry, without using stains or any other marker technology. An example of combined fluid, cell and tissue analysis of thyroid cancers based on infrared technology is introduced to demonstrate the possibility of earlier detection of gland abnormalities and biochemical alterations in cell extracts using fine needle aspirates. Simple statistical techniques such as bivariate histogram analysis can distinguish between normal and altered cells and tissues when applied to infrared spectra and images. More complex mathematical techniques such as Principal Component Analysis (PCA) or Artificial Neural Networks (ANN) provide additional evaluation capabilities that can relate spectra of an unknown sample to an infrared reference database of known cell states. It is documented how this new infrared technology could enhance the diagnoses, treatment decisions and prognoses of patients in the field of cancer medicine. PMID:12622515

Schultz, Christian P

2002-04-01

405

Dynamic measurements by color gratings projection method using a two-step Fourier transform method  

NASA Astrophysics Data System (ADS)

The Fourier transform method is an analytical method for interferograms with a spatial linear carrier. Interferograms with a spatial linear carrier are analyzed to obtain the phase, by eliminating the noise from the shape components of the interferograms in the Fourier domain. However, when the noise and shape components overlap in the Fourier domain, it is difficult to eliminate only the overlapped noise components using conventional filtering techniques, such as bandpass filtering. Accordingly, a method is proposed to solve this problem using two interferograms with slightly different carrier frequencies. In this method, the Fourier transforms of two interferograms with slightly different carrier frequencies are separately calculated. Both of the spectra resulting from the Fourier transforms of the interferograms contain the same noise components; however, the locations of these components differ slightly for the two spectra. By subtracting the two Fourier spectra, the noise components are removed, and the main components are generated, because the frequency difference between the two components is small. We have named the proposed method the "two-step Fourier transpose method". The validity of the proposed filtering method is confirmed by experiments in which two color fringes are projected simultaneously onto a scatter object. Images of the color fringes are acquired via a CCD camera under the slow deformation of the scatter object. The images are then analyzed via the proposed method.

Kamiya, Kazuhide; Nomura, Takashi; Tanbo, Ami; Kimihisa, Matsumoto; Hatsuzou, Tashiro; Suzuki, Shinya

2012-11-01

406

Doppler streak mode Fourier domain optical coherence tomography  

NASA Astrophysics Data System (ADS)

Doppler Fourier domain optical coherence tomography is able to be used for in vivo blood flow measurement. In conventional methods, the highest velocity that can be measured is limited to the range the phase shift between two successively recorded depth profiles at the same probe-beam location, which cannot exceed (-?, ?), otherwise phase wrapping will occur. This phase-wrapping limit is determined by the time interval between two consecutive A-scans. We present a novel approach to shorten the time interval between two consecutive A-scans and thus increase the phase-wrapping limit by using an area scan camera to record the interference spectrum in a streak mode. To demonstrate the effectiveness of this method, the blood flows in HH18 and HH19 chick hearts were imaged and phase wrapping free Doppler images were obtained.

Wang, Rui; Yun, Julie X.; Goodwin, Richard; Markwald, Roger; Runyan, Raymond B.; Gao, Bruce

2012-02-01

407

Phase and image reconstruction from interferometric imaging: Integration of the phasors.  

NASA Astrophysics Data System (ADS)

We present a new approach of a phase recovery method derived from the Knox-Thompson one, and used to reconstruct images blurred by the atmospheric turbulence. We rebuild the phase of the visibility whose main value contains discontinuities due to random phase shifts induced by the turbulence. The method presented in this paper is an upgrade of the one described by Monin et al. (1992) who computed the average of spatial phase gradients. We now work on integration of the phasors gradients exp(i??), computing the average phasor components of the cross-spectrum of the visibility to reconstruct the original phase. We discuss the implied hypothesis and the advantage of our new approach. We present results on simulated images which visibility phases have been distorted using a model of atmospheric perturbed wavefronts, as well as an application on real speckle data.

Ageorges, N.; Monin, J.-L.; Desbat, L.; Tessier, E.

1995-07-01

408

LOW COST IMAGER FOR POLLUTANT GAS LEAK DETECTION - PHASE II  

EPA Science Inventory

An inexpensive imaging Instrument to quickly locate leaks of methane and other greenhouse and VOC gases would reduce the cost and effort expended by industry to comply with EPA regulations. In Phase I, of this WBIR program, a new gas leak visualization camera was demonstrated...

409

Artifact in SE phase images can mimic aortic dissection.  

PubMed

Phase images of cardiac-triggered thoracic spin-echo scans can present an artifactual border-like feature across the aorta. This may be misinterpreted as a dissection. The artifact results from helical flow in the aorta; cause and appearance of the artifact are discussed. PMID:8956148

den Boer, J A; Rozeboom, A R

410

Phase Diversity and Polarization Augmented Techniques for Active Imaging.  

National Technical Information Service (NTIS)

A multi-frame active phase diversity imaging (APDI) algorithm is derived for coherent light statistics and demonstrated. In addition to conventional focal-plane and diversity-plane data, a statistical description for pupil-plane (PP) intensity is formed a...

P. M. Johnson

2007-01-01

411

Imaging for Borehole Wall by a Cylindrical Linear Phased Array  

Microsoft Academic Search

A new ultrasonic cylindrical linear phased array (CLPA) transducer is designed and fabricated for the borehole wall imaging in petroleum logging based on the previous theoretical researches. First, the CLPA transducer, which is made up of numbers of the piezoelectric elements distributed on the surface of a cylinder uniformly, is designed and fabricated. By transmitting and receiving acoustic waves with

Bi-Xing Zhang; Fang-Fang Shi; Xian-Mei Wu; Jun-Jie Gong; Cheng-Guang Zhang

2010-01-01

412

Cassini UVIS Observatory Phase spectral imaging of the Saturn system  

Microsoft Academic Search

The Cassini UVIS spectrometer systems began the Program Observatory Phase on December 25, 2003, with mosaics of the Saturn system for the purpose of obtaining spectral images of the ˜ 30 X 50 Saturn radii (RS) region surrounding planet center. The first group of mosaics were obtained daily through January 6, 2004. The experiment resumed again on February 7, 2004

D. Shemansky; Cassini Uvis

2004-01-01

413

Dynamic Studies of Lung Fluid Clearance with Phase Contrast Imaging  

SciTech Connect

Clearance of liquid from the airways at birth is a poorly understood process, partly due to the difficulties of observing and measuring the distribution of air within the lung. Imaging dynamic processes within the lung in vivo with high contrast and spatial resolution is therefore a major challenge. However, phase contrast X-ray imaging is able to exploit inhaled air as a contrast agent, rendering the lungs of small animals visible due to the large changes in the refractive index at air/tissue interfaces. In concert with the high spatial resolution afforded by X-ray imaging systems (<100 {mu}m), propagation-based phase contrast imaging is ideal for studying lung development. To this end we have utilized intense, monochromatic synchrotron radiation, together with a fast readout CCD camera, to study fluid clearance from the lungs of rabbit pups at birth. Local rates of fluid clearance have been measured from the dynamic sequences using a single image phase retrieval algorithm.

Kitchen, Marcus J.; Williams, Ivan; Irvine, Sarah C.; Morgan, Michael J.; Paganin, David M. [School of Physics, Monash University, Victoria 3800 (Australia); Lewis, Rob A.; Pavlov, Konstantin [Monash Centre for Synchrotron Science, Monash University, Victoria 3800 (Australia); Hooper, Stuart B.; Wallace, Megan J. [Department of Physiology, Monash University, Victoria 3800 (Australia); Siu, Karen K. W. [School of Physics, Monash University, Victoria 3800 (Australia); Department of Medical Imaging and Radiation Science, Monash University, Victoria 3800 (Australia); Yagi, Naoto; Uesugi, Kentaro [SPring-8/JASRI, Mikazuki, Hyogo 679-5198 (Japan)

2007-01-19

414

Fourier-Bessel rotational invariant eigenimages  

NASA Astrophysics Data System (ADS)

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 bandlimited 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.

Zhao, Zhizhen; Singer, Amit

2013-05-01

415

Drive frequency dependent phase imaging in piezoresponse force microscopy  

SciTech Connect

The drive frequency dependent piezoresponse (PR) phase signal in near-stoichiometric lithium niobate crystals is studied by piezoresponse force microscopy. It is clearly shown that the local and nonlocal electrostatic forces have a great contribution to the PR phase signal. The significant PR phase difference of the antiparallel domains are observed at the contact resonances, which is related to the electrostatic dominated electromechanical interactions of the cantilever and tip-sample system. Moreover, the modulation voltage induced frequency shift at higher eigenmodes could be attributed to the change of indention force depending on the modulation amplitude with a piezoelectric origin. The PR phase of the silicon wafer is also measured for comparison. It is certificated that the electrostatic interactions are universal in voltage modulated scanning probe microscopy and could be extended to other phase imaging techniques.

Bo Huifeng; Kan Yi; Lu Xiaomei; Liu Yunfei; Peng Song; Wang Xiaofei; Cai Wei; Xue Ruoshi; Zhu Jinsong [Department of Physics, National Laboratory of Solid State Microstructures, Nanjing University, Nanjing 210093 (China)

2010-08-15

416

Phase classification by mean shift clustering of multispectral materials images.  

PubMed

A mean-shift clustering (MSC) algorithm is introduced as a valuable alternative to perform materials phase classification from multispectral images. As opposed to other multivariate statistical techniques, such as factor analysis or principal component analysis (PCA), clustering techniques directly assign a class label to each pixel, so that their outputs are phase segmented images, i.e., there is no need for an additional segmentation algorithm. On the other hand, as compared to other clustering procedures and classification methods, such as segmentation by thresholding of multiple spectral components, MSC has the advantages of not requiring previous knowledge of the number of data clusters and not assuming any shape for these clusters, i.e., neither the number nor the composition of the phases must be previously known. This makes MSC a particularly useful tool for exploratory research, assisting phase identification of unknown samples. Visualization and interpretation of the results are also simplified, since the information content of the output image does not depend on the particular choice of the content of the color channels.We applied MSC to the analysis of two sets of X-ray maps acquired in scanning electron microscopes equipped with energy-dispersive detection systems. Our results indicate that MSC is capable of detecting additional phases, not clearly identified through PCA or multiple thresholding, with a very low empirical reject rate. PMID:23800390

Martins, Diego Schmaedech; Josa, Victor M Galván; Castellano, Gustavo; da Costa, José A T Borges

2013-06-26

417

Separation of formants from glottal impulses in high-resolution spectrograms using higher-order short-time Fourier transform (STFT) phase derivatives  

NASA Astrophysics Data System (ADS)

The channelized instantaneous frequency of a signal x(T) is CIFx(?,T)=(?/?T)arg(Fh(?,T)), where Fh is the short-time Fourier transform of x(T) using window function h. The local group delay of a signal is LGDx(?,T)=-(?/??)arg(Fh(?,T)). For each point Fh(?0,T0) in the STFT, the f-t coordinates [CIF(?0,T0),t-LGD(?0,T0)] pinpoint the local mean of the Rihacek distribution of complex signal energy, and this reassignment of the STFT magnitude yields a high-resolution spectrogram without blurriness [Auger and Flandrin, ``Improving the readability of time-frequency and time-scale representations by the reassignment method,'' IEEE Trans. Signal Process 43(5), 1068-1089 (1995)]. Nelson [``Instantaneous higher order phase derivatives,'' Digital Signal Process 12, 416-428 (2002)] demonstrated that the significant AM/FM components of a signal x(T) have (?/??)CIFx(?,T)~=0. By plotting just those STFT points meeting this condition to within a threshold, a spectrogram showing only speech resonances can be drawn using short analysis frames. By moving to a long-frame analysis, the resonance tracker becomes an effective pitch and harmonic tracker. Nelson further demonstrated that the impulses in a signal x(T) have (?/?T)LGDx(?,T)~=1. By plotting just those points meeting this condition to within a threshold, a spectrogram of speech impulses can alternatively be drawn.

Fulop, Sean A.

2004-10-01

418

Sample handling and contamination encountered when coupling offline normal phase high performance liquid chromatography fraction collection of petroleum samples to Fourier transform ion cyclotron resonance mass spectrometry.  

PubMed

Normal phase high performance liquid chromatography (HPLC) is used to separate a gas oil petroleum sample, and the fractions are collected offline and analyzed on a high resolution Fourier Transform Ion Cyclotron Resonance Mass Spectrometer (FT-ICR MS). The separation prior to MS analysis dilutes the sample significantly; therefore the fractions need to be prepared properly to achieve the best signal possible. The methods used to prepare the HPLC fractions for MS analysis are described, with emphasis placed on increasing the concentration of analyte species. The dilution effect also means that contamination in the MS spectra needs to be minimized. The contamination from molecular sieves, plastics, soap, etc. and interferences encountered during the offline fraction collection process are described and eliminated. A previously unreported MS contamination of iron formate clusters with a 0.8 mass defect in positive mode electrospray is also described. This interference resulted from the stainless steel tubing in the HPLC system. Contamination resulting from what has tentatively been assigned as palmitoylglycerol and stearoylglycerol was also observed; these compounds have not previously been reported as contaminant peaks. PMID:22840706

Oro, Nicole E; Whittal, Randy M; Lucy, Charles A

2012-07-04