Sample records for fourier phase image

  1. Quantitative phase imaging via Fourier ptychographic microscopy.

    PubMed

    Ou, Xiaoze; Horstmeyer, Roarke; Yang, Changhuei; Zheng, Guoan

    2013-11-15

    Fourier ptychographic microscopy (FPM) is a recently developed imaging modality that uses angularly varying illumination to extend a system's performance beyond the limit defined by its optical components. The FPM technique applies a novel phase-retrieval procedure to achieve resolution enhancement and complex image recovery. In this Letter, we compare FPM data to theoretical prediction and phase-shifting digital holography measurement to show that its acquired phase maps are quantitative and artifact-free. We additionally explore the relationship between the achievable spatial and optical thickness resolution offered by a reconstructed FPM phase image. We conclude by demonstrating enhanced visualization and the collection of otherwise unobservable sample information using FPM's quantitative phase. PMID:24322147

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

    PubMed Central

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

    2008-01-01

    This paper briefly reviews the basics of optical Fourier techniques (OFT) and applications for medical image processing as well as phase contrast imaging of live biological specimens. Enhancement of microcalcifications in a mammogram for early diagnosis of breast cancer is the main focus. Various spatial filtering techniques such as conventional 4f filtering using a spatial mask, photoinduced polarization rotation in photosensitive materials, Fourier holography, and nonlinear transmission characteristics of optical materials are discussed for processing mammograms. We also reviewed how the intensity dependent refractive index can be exploited as a phase filter for phase contrast imaging with a coherent source. This novel approach represents a significant advance in phase contrast microscopy. PMID:18458764

  3. Quantitative phase imaging of live cells using fast Fourier phase microscopy

    NASA Astrophysics Data System (ADS)

    Lue, Niyom; Choi, Wonshik; Popescu, Gabriel; Ikeda, Takahiro; Dasari, Ramachandra R.; Badizadegan, Kamran; Feld, Michael S.

    2007-04-01

    Using the decomposition of an image field in two spatial components that can be controllably shifted in phase with respect to each other, a new quantitative-phase microscope has been developed. The new instrument, referred to as the fast Fourier phase microscope (f-FPM), provides a factor of 100 higher acquisition rate compared with our previously reported Fourier phase microscope. The resulting quantitative-phase images are characterized by diffraction limited transverse resolution and path-length stability better than 2 nm at acquisition rates of 10 frames/s or more. These features make the f-FPM particularly appealing for investigating the structure and dynamics of live cells over a broad range of time scales. In addition, we demonstrate the possibility of examining subcellular structures by digitally processing the amplitude and phase information provided by the instrument. Thus we developed software that can emulate phase contrast and differential interference contrast microscopy images by numerically processing FPM images. This approach adds the flexibility of digitally varying the phase shift between the two interfering beams. The images obtained appear as if they were recorded by variable phase contrast or differential interference contrast microscopes that deliver an enhanced view to the subcellular structure when compared with the typical commercial microscope.

  4. Multiple-image encryption based on phase mask multiplexing in fractional Fourier transform domain.

    PubMed

    Liansheng, Sui; Meiting, Xin; Ailing, Tian

    2013-06-01

    A multiple-image encryption scheme is proposed based on the phase retrieval process and phase mask multiplexing in the fractional Fourier transform domain. First, each original gray-scale image is encoded into a phase only function by using the proposed phase retrieval process. Second, all the obtained phase functions are modulated into an interim, which is encrypted into the final ciphertext by using the fractional Fourier transform. From a plaintext image, a group of phase masks is generated in the encryption process. The corresponding decrypted image can be recovered from the ciphertext only with the correct phase mask group in the decryption process. Simulation results show that the proposed phase retrieval process has high convergence speed, and the encryption algorithm can avoid cross-talk; in addition, its encrypted capacity is considerably enhanced. PMID:23722815

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

    NASA Astrophysics Data System (ADS)

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

    2013-11-01

    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.

  6. Double image encryption based on random phase encoding in the fractional Fourier domain.

    PubMed

    Tao, Ran; Xin, Yi; Wang, Yue

    2007-11-26

    A novel image encryption method is proposed by utilizing random phase encoding in the fractional Fourier domain to encrypt two images into one encrypted image with stationary white distribution. By applying the correct keys which consist of the fractional orders, the random phase masks and the pixel scrambling operator, the two primary images can be recovered without cross-talk. The decryption process is robust against the loss of data. The phase-based image with a larger key space is more sensitive to keys and disturbances than the amplitude-based image. The pixel scrambling operation improves the quality of the decrypted image when noise perturbation occurs. The novel approach is verified by simulations. PMID:19550895

  7. Single-channel color image encryption using phase retrieve algorithm in fractional Fourier domain

    NASA Astrophysics Data System (ADS)

    Sui, Liansheng; Xin, Meiting; Tian, Ailing; Jin, Haiyan

    2013-12-01

    A single-channel color image encryption is proposed based on a phase retrieve algorithm and a two-coupled logistic map. Firstly, a gray scale image is constituted with three channels of the color image, and then permuted by a sequence of chaotic pairs generated by the two-coupled logistic map. Secondly, the permutation image is decomposed into three new components, where each component is encoded into a phase-only function in the fractional Fourier domain with a phase retrieve algorithm that is proposed based on the iterative fractional Fourier transform. Finally, an interim image is formed by the combination of these phase-only functions and encrypted into the final gray scale ciphertext with stationary white noise distribution by using chaotic diffusion, which has camouflage property to some extent. In the process of encryption and decryption, chaotic permutation and diffusion makes the resultant image nonlinear and disorder both in spatial domain and frequency domain, and the proposed phase iterative algorithm has faster convergent speed. Additionally, the encryption scheme enlarges the key space of the cryptosystem. Simulation results and security analysis verify the feasibility and effectiveness of this method.

  8. Fractional Fourier domain optical image hiding using phase retrieval algorithm based on iterative nonlinear double random phase encoding.

    PubMed

    Wang, Xiaogang; Chen, Wen; Chen, Xudong

    2014-09-22

    We present a novel image hiding method based on phase retrieval algorithm under the framework of nonlinear double random phase encoding in fractional Fourier domain. Two phase-only masks (POMs) are efficiently determined by using the phase retrieval algorithm, in which two cascaded phase-truncated fractional Fourier transforms (FrFTs) are involved. No undesired information disclosure, post-processing of the POMs or digital inverse computation appears in our proposed method. In order to achieve the reduction in key transmission, a modified image hiding method based on the modified phase retrieval algorithm and logistic map is further proposed in this paper, in which the fractional orders and the parameters with respect to the logistic map are regarded as encryption keys. Numerical results have demonstrated the feasibility and effectiveness of the proposed algorithms. PMID:25321769

  9. Self-images of periodic phase elements in the fractional Fourier transform domain

    NASA Astrophysics Data System (ADS)

    Shovgenyuk, Mykhailo V.; Kozlovskii, Yuri M.

    2006-01-01

    General conditions of periodic phase elements self-images forming (Talbot effect) in the fractional Fourier transform (FrFT) domain is given. Analytical solution of the FrFT images intensity distribution for the different forms (binary, linear, parabolic and others) of periodic elements low-level cell profiles is presented. Intensity difference ?? measuring of the FrFT periodic self-image allow to determine the phase difference ?? of periodic elements low-level cell profile. Theory of the FrFT images forming of periodic phase elements based on signal distribution method is given. We use ambiguity function A ff* (? 0? 0) in difference conjugate coordinates (? 0? 0) as base functional of the periodic phase element distribution. The FrFT distribution A upup*(? 0? 0) corresponds to the rotation matrix T ? which describe rotation of the input signal distribution on an angle ?=p?/2, p=0÷ - the FrFT parameter. The signal distribution method allow to obtain general formula of intensity distribution of the periodic phase element FrFT image. Theoretically proved that at condition F 0/tan?=1, where F 0=T2/4?d - Fresnel number, T - phase element period, ? - wave-length, d - length, periodic phase elements self-images are forming in the FrFT domain. In this case interference term is written as ? - function and intensity distribution I(?) of the FrFT self-images is forming as superposition of the cross displaced on a quarter of period self-images of neighboring phase low-cells. Analysis of the FrFT self-images forming at condition 2F0/tan? is also given. The results of numerical calculations of the periodic phase elements self-images at the different values of the FrFT parameter p are presented. Analytical dependence of the FrFT self-images contrast from phase difference ?? is obtained and the questions about phase microrelief parameters restoration of the phase element low-cell are discussed.

  10. Fourier plane imaging microscopy

    SciTech Connect

    Dominguez, Daniel, E-mail: daniel.dominguez@ttu.edu; Peralta, Luis Grave de [Department of Physics, Texas Tech University, Lubbock, Texas 79409 (United States); Nano Tech Center, Texas Tech University, Lubbock, Texas 79409 (United States); Alharbi, Nouf; Alhusain, Mdhaoui [Department of Physics, Texas Tech University, Lubbock, Texas 79409 (United States); Bernussi, Ayrton A. [Nano Tech Center, Texas Tech University, Lubbock, Texas 79409 (United States); Department of Electrical and Computer Engineering, Texas Tech University, Lubbock, Texas 79409 (United States)

    2014-09-14

    We show how the image of an unresolved photonic crystal can be reconstructed using a single Fourier plane (FP) image obtained with a second camera that was added to a traditional compound microscope. We discuss how Fourier plane imaging microscopy is an application of a remarkable property of the obtained FP images: they contain more information about the photonic crystals than the images recorded by the camera commonly placed at the real plane of the microscope. We argue that the experimental results support the hypothesis that surface waves, contributing to enhanced resolution abilities, were optically excited in the studied photonic crystals.

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

    PubMed

    Wang, Xiaogang; Zhao, Daomu

    2013-09-01

    A nonlinear color and grayscale images cryptosystem based on phase-truncated fractional Fourier transform and optical superposition principle is proposed. In order to realize simultaneous encryption of color and grayscale images, each grayscale image is first converted into two phase masks by using an optical coherent superposition, one of which is treated as a part of input information that will be fractional Fourier transformed while the other in the form of a chaotic random phase mask (CRPM) is used as a decryption key. For the purpose of optical performance, all the processes are performed through three channels, i.e., red, green, and blue. Different from most asymmetric encryption methods, the decryption process is designed to be linear for the sake of effective decryption. The encryption level of a double random phase encryption based on phase-truncated Fourier transform is enhanced by extending it into fractional Fourier domain and the load of the keys management and transmission is lightened by using CRPMs. The security of the proposed cryptosystem is discussed and computer simulation results are presented to verify the validity of the proposed method. PMID:24085074

  12. Imaging Fourier transform spectrometer

    NASA Astrophysics Data System (ADS)

    Villemaire, Andre J.; Fortin, Serge; Giroux, Jean; Smithson, Tracy; Oermann, Raymond J.

    1995-06-01

    Design considerations and experimental measurements from an imaging Fourier transform spectrometer are presented. The system is based on the Bomem MB-series of Fourier transform interferometer and is capable of more than 8 frames/second at 4 cm(superscript -1 apodized spectral resolution. The interferometer features dual output beams, allowing for example, the coverage of two different spectral ranges using a short-wave array and a long- wave array. The present system uses a set of two 8 X 8 InSb detector arrays to cover the 2 to 5.3 micrometers spectral range on two coaligned fields of view of 4 mrad X 4 mrad and 1 mrad X 1 mrad. Predicted noise equivalent spectral radiance as well as instrument lineshape are compared to measurements on the actual system. Particular emphasis is devoted to the behavior of the instrument lineshape with respect to off-axis position in the focal plane.

  13. Fourier plane image amplifier

    DOEpatents

    Hackel, L.A.; Hermann, M.R.; Dane, C.B.; Tiszauer, D.H.

    1995-12-12

    A solid state laser is frequency tripled to 0.3 {micro}m. A small portion of the laser is split off and generates a Stokes seed in a low power oscillator. The low power output passes through a mask with the appropriate hole pattern. Meanwhile, the bulk of the laser output is focused into a larger stimulated Brillouin scattering (SBS) amplifier. The low power beam is directed through the same cell in the opposite direction. The majority of the amplification takes place at the focus which is the fourier transform plane of the mask image. The small holes occupy large area at the focus and thus are preferentially amplified. The amplified output is now imaged onto the multichip module where the holes are drilled. Because of the fourier plane amplifier, only about 1/10th the power of a competitive system is needed. This concept allows less expensive masks to be used in the process and requires much less laser power. 1 fig.

  14. Fourier plane image amplifier

    DOEpatents

    Hackel, Lloyd A. (Livermore, CA); Hermann, Mark R. (San Ramon, CA); Dane, C. Brent (Livermore, CA); Tiszauer, Detlev H. (Tracy, CA)

    1995-01-01

    A solid state laser is frequency tripled to 0.3 .mu.m. A small portion of the laser is split off and generates a Stokes seed in a low power oscillator. The low power output passes through a mask with the appropriate hole pattern. Meanwhile, the bulk of the laser output is focused into a larger stimulated Brillouin scattering (SBS) amplifier. The low power beam is directed through the same cell in the opposite direction. The majority of the amplification takes place at the focus which is the fourier transform plane of the mask image. The small holes occupy large area at the focus and thus are preferentially amplified. The amplified output is now imaged onto the multichip module where the holes are drilled. Because of the fourier plane amplifier, only .about.1/10th the power of a competitive system is needed. This concept allows less expensive masks to be used in the process and requires much less laser power.

  15. Electro-optic imaging Fourier transform spectrometer

    NASA Technical Reports Server (NTRS)

    Chao, Tien-Hsin (Inventor); Znod, Hanying (Inventor)

    2009-01-01

    An Electro-Optic Imaging Fourier Transform Spectrometer (EOIFTS) for Hyperspectral Imaging is described. The EOIFTS includes an input polarizer, an output polarizer, and a plurality of birefringent phase elements. The relative orientations of the polarizers and birefringent phase elements can be changed mechanically or via a controller, using ferroelectric liquid crystals, to substantially measure the spectral Fourier components of light propagating through the EIOFTS. When achromatic switches are used as an integral part of the birefringent phase elements, the EIOFTS becomes suitable for broadband applications, with over 1 micron infrared bandwidth.

  16. Asymmetric double-image encryption method by using iterative phase retrieval algorithm in fractional Fourier transform domain

    NASA Astrophysics Data System (ADS)

    Sui, Liansheng; Lu, Haiwei; Ning, Xiaojuan; Wang, Yinghui

    2014-02-01

    A double-image encryption scheme is proposed based on an asymmetric technique, in which the encryption and decryption processes are different and the encryption keys are not identical to the decryption ones. First, a phase-only function (POF) of each plain image is retrieved by using an iterative process and then encoded into an interim matrix. Two interim matrices are directly modulated into a complex image by using the convolution operation in the fractional Fourier transform (FrFT) domain. Second, the complex image is encrypted into the gray scale ciphertext with stationary white-noise distribution by using the FrFT. In the encryption process, three random phase functions are used as encryption keys to retrieve the POFs of plain images. Simultaneously, two decryption keys are generated in the encryption process, which make the optical implementation of the decryption process convenient and efficient. The proposed encryption scheme has high robustness to various attacks, such as brute-force attack, known plaintext attack, cipher-only attack, and specific attack. Numerical simulations demonstrate the validity and security of the proposed method.

  17. Removal of a mirror image and enhancement of the signal-to-noise ratio in Fourier-domain optical coherence tomography using an electro-optic phase modulator.

    PubMed

    Zhang, Jun; Nelson, J Stuart; Chen, Zhongping

    2005-01-15

    A novel swept-laser-based Fourier-domain optical coherence tomography system using an electro-optic phase modulator was demonstrated. The imaging range was doubled by cancellation of the mirror image. The elimination of low-frequency noises resulting from dc and autocorrelation terms increased the sensitivity by 20 dB. PMID:15675695

  18. Fourier Analysis of Ghost Imaging

    E-print Network

    Honglin Liu; Jing Cheng; Yanfeng Bai; Shensheng Han

    2006-09-28

    Fourier analysis of ghost imaging (FAGI) is proposed in this paper to analyze the properties of ghost imaging with thermal light sources. This new theory is compatible with the general correlation theory of intensity fluctuation and could explain some amazed phenomena. Furthermore we design a series of experiments to verify the new theory and investigate the inherent properties of ghost imaging.

  19. IMAGE RECONSTRUCTION FROM LOCALIZED FOURIER MAGNITUDE

    E-print Network

    Gil Michael; Moshe Porat

    Fourier transform magnitude is, in many cases, the only measurable data in fields such as optics, x-ray imaging, crystallography and astronomy. Spectral phase information is impractical to obtain in these instances, due to the relatively short wavelength involved. In this paper a new algorithm for image reconstruction from localized spectral magnitude is presented. The algorithm is based on localized Fourier transform magnitudes and a single spatial sample to fully reconstruct an image. The process reconstructs successively larger image blocks, until the entire image is restored, using the spatial sample as initial data. It is shown, that even in cases where the spatial sample is badly corrupted, it has little effect on the reconstructed image. The algorithm is analyzed in the presence of noise, and simulation results are presented. 1.

  20. Optical image-hiding method with false information disclosure based on the interference principle and partial-phase-truncation in the fractional Fourier domain

    NASA Astrophysics Data System (ADS)

    Dai, Chaoqing; Wang, Xiaogang; Zhou, Guoquan; Chen, Junlang

    2014-05-01

    An image-hiding method based on the optical interference principle and partial-phase-truncation in the fractional Fourier domain is proposed. The primary image is converted into three phase-only masks (POMs) using an analytical algorithm involved partial-phase-truncation and a fast random pixel exchange process. A procedure of a fake silhouette for a decryption key is suggested to reinforce the encryption and give a hint of the position of the key. The fractional orders of FrFT effectively enhance the security of the system. In the decryption process, the POM with false information and the other two POMs are, respectively, placed in the input and fractional Fourier planes to recover the primary image. There are no unintended information disclosures and iterative computations involved in the proposed method. Simulation results are presented to verify the validity of the proposed approach.

  1. Comment on: Novel image encryption/decryption based on quantum fourier transform and double phase encoding

    NASA Astrophysics Data System (ADS)

    Song, Xian-Hua; Niu, Xia-Mu

    2014-06-01

    In this letter, we have pointed out some problems existed in (Yang et al. in Quantum Inf Process 12(11):3477-3493, 2013). Then, a new restricted quantum image color transformation method is proposed.

  2. Laser Field Imaging Through Fourier Transform Heterodyne

    SciTech Connect

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

    1999-04-05

    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.

  3. Laser field imaging through Fourier transform heterodyne

    NASA Astrophysics Data System (ADS)

    Cooke, Bradly J.; Galbraith, Amy E.; Laubscher, Bryan E.; Strauss, Charlie E. M.; Olivas, Nicholas L.; Grubler, Andrew C.

    1999-05-01

    We 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.

  4. Fourier phase microscopy with white light.

    PubMed

    Bhaduri, Basanta; Tangella, Krishnarao; Popescu, Gabriel

    2013-01-01

    Laser-based Fourier phase microscopy (FPM) works on the principle of decomposition of an image field in two spatial components that can be controllably shifted in phase with respect to each other. However, due to the coherent illumination, the contrast in phase images is degraded by speckles. In this paper we present FPM with spatially coherent white light (wFPM), which offers high spatial phase sensitivity due to the low temporal coherence and high temporal phase stability due to common path geometry. Further, by using a fast spatial light modulator (SLM) and a fast scientific-grade complementary metal oxide semiconductor (sCMOS) camera, we report imaging at a maximum rate of 12.5 quantitative phase frames per second with 5.5 mega pixels image size. We illustrate the utility of wFPM as a contrast enhancement as well as dynamic phase measurement method by imaging section of benign colonic glands and red blood cell membrane fluctuation. PMID:24010005

  5. Fourier phase microscopy with white light

    PubMed Central

    Bhaduri, Basanta; Tangella, Krishnarao; Popescu, Gabriel

    2013-01-01

    Laser-based Fourier phase microscopy (FPM) works on the principle of decomposition of an image field in two spatial components that can be controllably shifted in phase with respect to each other. However, due to the coherent illumination, the contrast in phase images is degraded by speckles. In this paper we present FPM with spatially coherent white light (wFPM), which offers high spatial phase sensitivity due to the low temporal coherence and high temporal phase stability due to common path geometry. Further, by using a fast spatial light modulator (SLM) and a fast scientific-grade complementary metal oxide semiconductor (sCMOS) camera, we report imaging at a maximum rate of 12.5 quantitative phase frames per second with 5.5 mega pixels image size. We illustrate the utility of wFPM as a contrast enhancement as well as dynamic phase measurement method by imaging section of benign colonic glands and red blood cell membrane fluctuation. PMID:24010005

  6. Color image projection based on Fourier holograms.

    PubMed

    Makowski, Michal; Ducin, Izabela; Sypek, Maciej; Siemion, Agnieszka; Siemion, Andrzej; Suszek, Jaroslaw; Kolodziejczyk, Andrzej

    2010-04-15

    A method of color image projection is experimentally validated. It assumes a simultaneous illumination of a spatial light modulator (SLM) with three laser beams converging in a common point on a projection screen. The beams are masked with amplitude filters so that each one illuminates one third of the area of the SLM. A Fourier hologram of a chosen color component of an input image is calculated, and its phase pattern is addressed on a corresponding part of the SLM area. A full-color flat image is formed on the screen as a result of color mixing. Additional techniques of image optimization are applied: time-integral speckle averaging and an off-axis shift of a zero-order peak. Static and animated experimental results of such a color holographic projection with a good image quality are presented. PMID:20410975

  7. Image information mining from geospatial archives based on a combination of the wavelet transform and Fourier phase descriptor

    NASA Astrophysics Data System (ADS)

    Shah, Vijay P.; Younan, Nicholas H.; Durbha, Surya S.; King, Roger L.

    2007-04-01

    In general, reflectance and spatial patterns characterize geospatial data. Current semantic-enabled framework image retrieval systems for geospatial data extract primitive features based on color, texture (Spatial Gray Level Dependency - SGLD matrices), and shape from the segmented homogenous region. However, the form of extracting textural information is computationally expensive. The state-of-the-art image mining system for multimedia image archives uses the wavelet transform for feature extraction to quickly and efficiently capture color and texture information. Since an image consists of three bands, color information is captured by converting the RGB space into HSV space. Thus, a new approach is required to capture the complete reflectance pattern, an important characteristic of geospatial data. This work proposes a new method to perform fast coarse image segmentation using descriptors obtained by combining the 2Dwavelet transform along the spatial axis and the Fourier transform along the spectral axis to capture color and texture information for segmentation. These features are later on used for region-based retrieval in Earth observation data archives. Compared to traditional techniques, result shows that the proposed method provides good retrieval accuracy in terms of F-measure for land cover classes.

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

    NASA Astrophysics Data System (ADS)

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

    2011-03-01

    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 (FD-OCT) to image the vibration of various micro-structures of the cochlea at the same time. An excised cochlea of a guinea pig was stimulated using sounds at various frequencies and vibration image was obtained. When measuring the apex area, vibration signal from different turns, which have different best response frequencies are obtained in the same image. The method has the potential to measure the response from a much wider region of the cochlea than any other currently used method. The noise floor for vibration image for the system at 200 Hz was ~0.3nm.

  9. Fast image alignment in the Fourier domain

    Microsoft Academic Search

    Ahmed Bilal Ashraf; Simon Lucey; Tsuhan Chen

    2010-01-01

    In this paper we propose a framework for gradient de- scent image alignment in the Fourier domain. Specifically, we propose an extension to the classical Lucas & Kanade (LK) algorithm where we represent the source and template image's intensity pixels in the complex 2D Fourier domain rather than in the 2D spatial domain. We refer to this ap- proach as

  10. Double-image encryption without information disclosure using phase-truncation Fourier transforms and a random amplitude mask.

    PubMed

    Wang, Xiaogang; Zhao, Daomu; Chen, Yixiang

    2014-08-10

    We present a study about information disclosure in phase-truncation-based cryptosystems. The main information of the original image to be encoded can be obtained by using a decryption key in the worst case. The problem cannot be thoroughly solved by imaginary part truncating, keeping the encryption keys as private keys, or applying different phase keys for different plaintexts during each encryption process as well as the phase modulation in the frequency domain. In order to eliminate the risk of unintended information disclosure, we further propose a nonlinear spatial and spectral encoding technique using a random amplitude mask (RAM). The encryption process involving two security layers can be fully controlled by a RAM. The spatial encoding of the plaintext images and the simultaneous encryption of the plaintext images and the encryption key greatly enhance the security of system, avoiding several attacks that have cracked the phase-truncation-based cryptosystems. Besides, the hybrid encryption system retains the advantage of a trap door one-way function of phase truncation. Numerical results have demonstrated the feasibility and effectiveness of the proposed encryption algorithm. PMID:25320917

  11. Optical scatter imaging using digital Fourier microscopy

    E-print Network

    Seet, K Y T; Meredith, P; Zvyagin, A V

    2007-01-01

    An approach reported recently by Alexandrov et al. on optical scatter imaging, termed digital Fourier microscopy (DFM), represents an adaptation of digital Fourier holography to selective imaging of biological matter. Holographic mode of recording of the sample optical scatter enables reconstruction of the sample image. Form-factor of the sample constituents provides a basis for discrimination of these constituents implemented via flexible digital Fourier filtering at the post processing stage. Like in the dark-field microscopy, the DFM image contrast appears to improve due to the suppressed optical scatter from extended sample structures. In this paper, we present theoretical and experimental study of DFM using biological phantom that contains polymorphic scatterers.

  12. Single-pixel imaging by means of Fourier spectrum acquisition

    NASA Astrophysics Data System (ADS)

    Zhang, Zibang; Ma, Xiao; Zhong, Jingang

    2015-02-01

    Single-pixel imaging techniques enable to capture a scene without a direct line of sight to the object, but high-quality imaging has been proven challenging especially in the presence of noisy environmental illumination. Here we present a single-pixel imaging technique that can achieve high-quality images by acquiring their Fourier spectrum. We use phase-shifting sinusoid structured illumination for the spectrum acquisition. Applying inverse Fourier transform to the obtained spectrum yields the desired image. The proposed technique is capable of capturing a scene without a direct view of it. Thus, it enables a feasible placement of detectors, only if the detectors can collect the light signals from the scene. The technique is also a compressive sampling like approach, so it can reconstruct an image from sub-Nyquist measurements. We experimentally obtain clear images by utilizing a detector not placed in direct view of the imaged scene even with noise introduced by environmental illuminations.

  13. Single-pixel imaging by means of Fourier spectrum acquisition.

    PubMed

    Zhang, Zibang; Ma, Xiao; Zhong, Jingang

    2015-01-01

    Single-pixel imaging techniques enable to capture a scene without a direct line of sight to the object, but high-quality imaging has been proven challenging especially in the presence of noisy environmental illumination. Here we present a single-pixel imaging technique that can achieve high-quality images by acquiring their Fourier spectrum. We use phase-shifting sinusoid structured illumination for the spectrum acquisition. Applying inverse Fourier transform to the obtained spectrum yields the desired image. The proposed technique is capable of capturing a scene without a direct view of it. Thus, it enables a feasible placement of detectors, only if the detectors can collect the light signals from the scene. The technique is also a compressive sampling like approach, so it can reconstruct an image from sub-Nyquist measurements. We experimentally obtain clear images by utilizing a detector not placed in direct view of the imaged scene even with noise introduced by environmental illuminations. PMID:25649009

  14. Fourier analysis of blood plasma laser images phase maps in the diagnosis of cancer in human organs

    NASA Astrophysics Data System (ADS)

    Angelsky, P. O.; Kushnerick, L. Ya.; Bachinskiy, V. T.; Vanchuliak, O. Ya.; Garazdiuk, M.; Pashkovska, N. V.; Andriychuk, D.

    2013-12-01

    A method of polarization mapping of the optico-anisotropic polycrystalline networks of the blood plasma albumin and globulin proteins with adjusted spatial-frequency filtering of the coordinate distributions of the azimuth and ellipticity of the polarization of laser radiation in the Fourier plane is proposed and substantiated. Comparative studies of the effectiveness of direct methods of mapping and a spatial-frequency selection in differentiating polarization azimuth and ellipticity maps of the field of laser radiation converted by the networks of albumin - globulin crystals of the blood plasma in healthy people and patients with prostate cancer have been carried out.

  15. Lensless Fourier-transform ghost imaging with classical incoherent light

    SciTech Connect

    Zhang, Minghui; Wei, Qing; Shen, Xia; Liu, Yongfeng; Liu, Honglin; Cheng, Jing; Han, Shensheng [Key Laboratory for Quantum Optics and Center for Cold Atom Physics, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai 201800 (China)

    2007-02-15

    The Fourier-transform ghost imaging of both amplitude-only and pure-phase objects was experimentally observed with classical incoherent light at Fresnel distance by a lensless scheme. The experimental results are in good agreement with the standard Fourier transform of the corresponding objects. This scheme provides a route toward aberration-free diffraction-limited three-dimensional images with classically incoherent thermal light (or neutrons), which have no resolution and depth-of-field limitations of lens-based tomographic systems.

  16. Parametric Fourier image characterization toolkit

    Microsoft Academic Search

    J. R. F. Alonso

    1987-01-01

    A suite of APL programs is described for characterization of bounded images for on-line process control or for artificial intelligence recognition functions. Beginning with an acquired threshold and edge enhanced image, the programs:detect the edges and close all bounded areas in the imageproduce arrays with the (x,y) locations of the boundaries of each object (bounded area) in the field, allowing

  17. Novel fringe scanning/Fourier transform method of synthetic imaging

    SciTech Connect

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

    1993-08-01

    We have developed a one-dimensional theory and a computer model for synthetically imaging scenes using a novel fringe scanning/Fourier transform technique. Our method probes a scene using two interfering beams of slightly different frequency. These beams form a moving fringe pattern which scans the scene and resonates with any spatial frequency components having the same spatial frequency as the scanning fringe pattern. A simple, non-imaging detector above the scene observes any scattered radiation from the scene falling onto it. If a resonance occurs between the scanning fringe pattern and the scene, then the scattered radiation will be modulated at the difference frequency between the two probing beams. By changing the spatial period of the fringe pattern and then measuring the amplitude and phase of the modulated radiation that is scattered from the scene, the Fourier amplitudes and phases of the different spatial frequency components making up the scene can be measured. A synthetic image of the scene being probed can be generated from this Fourier amplitude and phase data by taking the inverse Fourier transform of this information. This technique could be used to image objects using light, ultrasonic, or other electromagnetic or acoustic waves.

  18. Image encryption by using fractional Fourier transform and jigsaw transform in image bit planes

    Microsoft Academic Search

    Aloka Sinha; Kehar Singh

    2005-01-01

    We propose a new method for image encryption and decryption in which the image is broken up into bit planes. Each bit plane undergoes a jigsaw transform. The transformed bit planes are combined together and then encrypted using random phase masks and fractional Fourier transforms. The different fractional parameters, the random phase codes, and the jigsaw transform index form the

  19. Phase information in coherent Fourier scatterometry

    NASA Astrophysics Data System (ADS)

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

    2013-04-01

    Incoherent Optical Scatterometry (IOS) is widely used in semiconductor industry in applications related to optical metrology particularly in grating reconstruction. Recently, Coherent Fourier Scatterometry (CFS) has emerged as a strong alternative to the traditional IOS under suitable condition. When available, phase information is an added advantage in CFS to complement the intensity data. Phase information in the scattered far field is dependent on the structure and the composition of the grating. We derive and discuss the phase information accessible through the CFS. Phase difference between the diffracted orders is computed and the polarization dependent phase sensitivity of the grating parameters are discussed. The results are rigorously simulated and an experimental implementation of CFS demonstrates the functionality of the method.

  20. Speckle size in optical Fourier domain imaging

    Microsoft Academic Search

    G. Lamouche; S. Vergnole; C.-E. Bisaillon; M. Dufour; R. Maciejko; J.-P. Monchalin

    2007-01-01

    As in conventional time-domain optical coherence tomography (OCT), speckle is inherent to any Optical Fourier Domain Imaging (OFDI) of biological tissue. OFDI is also known as swept-source OCT (SS-OCT). The axial speckle size is mainly determined by the OCT resolution length and the transverse speckle size by the focusing optics illuminating the sample. There is also a contribution from the

  1. Optical image encryption based on the multiple-parameter fractional Fourier transform.

    PubMed

    Tao, Ran; Lang, Jun; Wang, Yue

    2008-03-15

    A novel image encryption algorithm is proposed based on the multiple-parameter fractional Fourier transform, which is a generalized fractional Fourier transform, without the use of phase keys. The image is encrypted simply by performing a multiple-parameter fractional Fourier transform with four keys. Optical implementation is suggested. The method has been compared with existing methods and shows superior robustness to blind decryption. PMID:18347716

  2. Adaptive system correction for robust Fourier ptychographic imaging.

    PubMed

    Bian, Zichao; Dong, Siyuan; Zheng, Guoan

    2013-12-30

    Fourier ptychography (FP) is a recently developed imaging approach that bypasses the resolution limit defined by the lens' aperture. In current FP imaging platforms, systematic noise sources come from the intensity fluctuation of multiple LED elements and the pupil aberrations of the employed optics. These system uncertainties can significantly degrade the reconstruction quality and limit the achievable resolution, imposing a restriction on the effectiveness of the FP approach. In this paper, we report an optimization procedure that performs adaptive system correction for Fourier ptychographic imaging. Similar to the techniques used in phase retrieval, the reported procedure involves the evaluation of an image-quality metric at each iteration step, followed by the estimation of an improved system correction. This optimization process is repeated until the image-quality metric is maximized. As a demonstration, we used this process to correct for illumination intensity fluctuation, to compensate for pupil aberration of the optics, and to recover several unknown system parameters. The reported adaptive correction scheme may improve the robustness of Fourier ptychographic imaging by factoring out system imperfections and uncertainties. PMID:24514833

  3. Direct phase retrieval in double blind Fourier holography.

    PubMed

    Raz, Oren; Leshem, Ben; Miao, Jianwei; Nadler, Boaz; Oron, Dan; Dudovich, Nirit

    2014-10-20

    Phase measurement is a long-standing challenge in a wide range of applications, from X-ray imaging to astrophysics and spectroscopy. While in some scenarios the phase is resolved by an interferometric measurement, in others it is reconstructed via numerical optimization, based on some a-priori knowledge about the signal. The latter commonly use iterative algorithms, and thus have to deal with their convergence, stagnation, and robustness to noise. Here we combine these two approaches and present a new scheme, termed double blind Fourier holography, providing an efficient solution to the phase problem in two dimensions, by solving a system of linear equations. We present and experimentally demonstrate our approach for the case of lens-less imaging. PMID:25401527

  4. Fourier transform digital holographic adaptive optics imaging system

    PubMed Central

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

    2013-01-01

    A Fourier transform digital holographic adaptive optics imaging system and its basic principles are proposed. The CCD is put at the exact Fourier transform plane of the pupil of the eye lens. The spherical curvature introduced by the optics except the eye lens itself is eliminated. The CCD is also at image plane of the target. The point-spread function of the system is directly recorded, making it easier to determine the correct guide-star hologram. Also, the light signal will be stronger at the CCD, especially for phase-aberration sensing. Numerical propagation is avoided. The sensor aperture has nothing to do with the resolution and the possibility of using low coherence or incoherent illumination is opened. The system becomes more efficient and flexible. Although it is intended for ophthalmic use, it also shows potential application in microscopy. The robustness and feasibility of this compact system are demonstrated by simulations and experiments using scattering objects. PMID:23262541

  5. Adaptive chirp-Fourier transform for chirp estimation with applications in ISAR imaging of maneuvering targets

    NASA Astrophysics Data System (ADS)

    Xia, Xiang-Gen; Wang, Genyuan; Chen, Victor C.

    2001-03-01

    This paper first reviews some basic properties of the discrete chirp-Fourier transform and then present an adaptive chirp- Fourier transform, a generalization of the amplitude and phase estimation of sinusoids (APES) algorithm proposed by Li and Stoica for sinusoidal signals. We finally applied it to the ISAR imaging of maneuvering targets.

  6. Single beam Fourier transform digital holographic quantitative phase microscopy

    NASA Astrophysics Data System (ADS)

    Anand, A.; Faridian, A.; Chhaniwal, V. K.; Mahajan, S.; Trivedi, V.; Dubey, S. K.; Pedrini, G.; Osten, W.; Javidi, B.

    2014-03-01

    Quantitative phase contrast microscopy reveals thickness or height information of a biological or technical micro-object under investigation. The information obtained from this process provides a means to study their dynamics. Digital holographic (DH) microscopy is one of the most used, state of the art single-shot quantitative techniques for three dimensional imaging of living cells. Conventional off axis DH microscopy directly provides phase contrast images of the objects. However, this process requires two separate beams and their ratio adjustment for high contrast interference fringes. Also the use of two separate beams may make the system more vulnerable to vibrations. Single beam techniques can overcome these hurdles while remaining compact as well. Here, we describe the development of a single beam DH microscope providing whole field imaging of micro-objects. A hologram of the magnified object projected on to a diffuser co-located with a pinhole is recorded with the use of a commercially available diode laser and an arrayed sensor. A Fourier transform of the recorded hologram directly yields the complex amplitude at the image plane. The method proposed was investigated using various phase objects. It was also used to image the dynamics of human red blood cells in which sub-micrometer level thickness variation were measurable.

  7. Single beam Fourier transform digital holographic quantitative phase microscopy

    SciTech Connect

    Anand, A., E-mail: arun-nair-in@yahoo.com; Chhaniwal, V. K.; Mahajan, S.; Trivedi, V. [Optics Laboratory, Applied Physics Department, Faculty of Technology and Engineering, M.S. University of Baroda, Vadodara 390001 (India)] [Optics Laboratory, Applied Physics Department, Faculty of Technology and Engineering, M.S. University of Baroda, Vadodara 390001 (India); Faridian, A.; Pedrini, G.; Osten, W. [Institut für Technische Optik, Universität Stuttgart, Pfaffenwaldring 9, 70569 Stuttgart (Germany)] [Institut für Technische Optik, Universität Stuttgart, Pfaffenwaldring 9, 70569 Stuttgart (Germany); Dubey, S. K. [Siemens Technology and Services Pvt. Ltd, Corporate Technology—Research and Technology Centre, Bangalore 560100 (India)] [Siemens Technology and Services Pvt. Ltd, Corporate Technology—Research and Technology Centre, Bangalore 560100 (India); Javidi, B. [Department of Electrical and Computer Engineering, U-4157, University of Connecticut, Storrs, Connecticut 06269-2157 (United States)] [Department of Electrical and Computer Engineering, U-4157, University of Connecticut, Storrs, Connecticut 06269-2157 (United States)

    2014-03-10

    Quantitative phase contrast microscopy reveals thickness or height information of a biological or technical micro-object under investigation. The information obtained from this process provides a means to study their dynamics. Digital holographic (DH) microscopy is one of the most used, state of the art single-shot quantitative techniques for three dimensional imaging of living cells. Conventional off axis DH microscopy directly provides phase contrast images of the objects. However, this process requires two separate beams and their ratio adjustment for high contrast interference fringes. Also the use of two separate beams may make the system more vulnerable to vibrations. Single beam techniques can overcome these hurdles while remaining compact as well. Here, we describe the development of a single beam DH microscope providing whole field imaging of micro-objects. A hologram of the magnified object projected on to a diffuser co-located with a pinhole is recorded with the use of a commercially available diode laser and an arrayed sensor. A Fourier transform of the recorded hologram directly yields the complex amplitude at the image plane. The method proposed was investigated using various phase objects. It was also used to image the dynamics of human red blood cells in which sub-micrometer level thickness variation were measurable.

  8. Target Image Enhancement in Radar Imaging Using Fractional Fourier Transform

    NASA Astrophysics Data System (ADS)

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

    2012-03-01

    This paper presents a new Range-Doppler Algorithm based on Fractional Fourier Transform (RDA-FrFT) to obtain High-Resolution (HR) images for targets in radar imaging. The performance of the proposed RDA-FrFT is compared with the classical RDA algorithm, which is based on the Fast Fourier Transform (FFT). A closed-form expression for the range and azimuth compression of the proposed RDA-FrFT is mathematically derived and analyzed from the HR Synthetic Aperture Radar (SAR) imaging point of view. The proposed RDA-FrFT takes its advantage of the property of the FrFT to resolve chirp signals with high precision. Results show that the proposed RDA-FrFT gives low Peak Side-Lobe (PSL) and Integrated Side-Lobe (ISL) levels in range and azimuth directions for detected targets. HR images are obtained using the proposed RDA-FrFT algorithm.

  9. A half-blind color image hiding and encryption method in fractional Fourier domains

    Microsoft Academic Search

    Fan Ge; Linfei Chen; Daomu Zhao

    2008-01-01

    We have proposed a new technique for digital image encryption and hiding based on fractional Fourier transforms with double random phases. An original hidden image is encrypted two times and the keys are increased to strengthen information protection. Color image hiding and encryption with wavelength multiplexing is proposed by embedding and encryption in R, G and B three channels. The

  10. Speckle size in optical Fourier domain imaging

    NASA Astrophysics Data System (ADS)

    Lamouche, G.; Vergnole, S.; Bisaillon, C.-E.; Dufour, M.; Maciejko, R.; Monchalin, J.-P.

    2007-06-01

    As in conventional time-domain optical coherence tomography (OCT), speckle is inherent to any Optical Fourier Domain Imaging (OFDI) of biological tissue. OFDI is also known as swept-source OCT (SS-OCT). The axial speckle size is mainly determined by the OCT resolution length and the transverse speckle size by the focusing optics illuminating the sample. There is also a contribution from the sample related to the number of scatterers contained within the probed volume. In the OFDI data processing, there is some liberty in selecting the range of wavelengths used and this allows variation in the OCT resolution length. Consequently the probed volume can be varied. By performing measurements on an optical phantom with a controlled density of discrete scatterers and by changing the probed volume with different range of wavelengths in the OFDI data processing, there is an obvious change in the axial speckle size, but we show that there is also a less obvious variation in the transverse speckle size. This work contributes to a better understanding of speckle in OCT.

  11. Random fractional Fourier transform.

    PubMed

    Liu, Zhengjun; Liu, Shutian

    2007-08-01

    We propose a novel random fractional Fourier transform by randomizing the transform kernel function of the conventional fractional Fourier transform. The random fractional Fourier transform inherits the excellent mathematical properties from the fractional Fourier transform and can be easily implemented in optics. As a primary application the random fractional Fourier transform can be directly used in optical image encryption and decryption. The double phase encoding image encryption schemes can thus be modeled with cascaded random fractional Fourier transformers. PMID:17671545

  12. Fast Fourier Transform in the Spiral Honeycomb Image Algebra

    Microsoft Academic Search

    Phil Sheridan; David M. Alexander; Kelly S. Nunn-clark

    2005-01-01

    The Fourier transform is one of the most important transformations in image processing. A major component of this influence comes from the ability to implement it efficiently on a digital computer. This paper describes one such efficient implementation and discusses its implications to digital technology as well as biological vision. The significance of the fast Fourier transform (FFT) presented in

  13. Fourier amplitude and phase analysis in the clinical evaluation of patients with cardiomyopathy

    SciTech Connect

    Alcan, K.E.; Robeson, W.; Graham, M.C.; Palestro, C.; Oliver, F.H.; Benua, R.S.

    1984-06-01

    Fifty-four patients with a cardiomyopathy were studied by Radionuclide Cardangiography (RNCA) and Fourier amplitude and phase image analysis. The study group included patients with ischemic cardiomyopathy (27) and an equal number of patients with a primary cardiomyopathy: drug-induced (22), idiopathic (three), radiation-induced (one), and amyloidosis (one). Twenty-eight patients had rest studies alone and 26 had both rest and stress studies (80 total). The mean rest LVEF in the ischemic group was 27.9%, in the drug-induced group 36.5%, and in the idiopathic group 30%. The stress LVEF decreased in 92% of patients with ischemic cardiomyopathy and 45% of patients with primary (drug-induced) cardiomyopathy. Fourier amplitude and phase images were generated for each study. Amplitude and phase images were abnormal in all patients with an ischemic cardiomyopathy. LV amplitude abnormalities were regional and phase was directional. A zone of dysynergy on phase analysis was present in 44% of patients with ischemic cardiomyopathy. In the drug-induced primary cardiomyopathy group, all patients had abnormal amplitude and 86% had abnormal phase. Amplitude abnormalities were global rather than regional and phase patterns were nondirectional. Only one patient had a zone of dysynergy on the phase image. We conclude that the stress LVEF alone cannot consistently differentiate between ischemic and primary cardiomyopathies and that Fourier amplitude and phase analysis may be useful in determining the etiology of a cardiomyopathy (ischemic vs primary).

  14. Radial Hilbert Transform in terms of the Fourier Transform applied to Image Encryption

    NASA Astrophysics Data System (ADS)

    Morales, Y.; Díaz, L.; Torres, C.

    2015-01-01

    In the present investigation, a mathematical algorithm under Matlab platform using Radial Hilbert Transform and Random Phase Mask for encrypting digital images is implemented. The algorithm is based on the use of the conventional Fourier transform and two random phase masks, which provide security and robustness to the system implemented. Random phase masks used during encryption and decryption are the keys to improve security and make the system immune to attacks by program generation phase masks.

  15. Fourier domain OCT imaging of American cockroach nervous system

    NASA Astrophysics Data System (ADS)

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

    2012-01-01

    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.

  16. Invariant quaternion radial harmonic Fourier moments for color image retrieval

    NASA Astrophysics Data System (ADS)

    Xiang-yang, Wang; Wei-yi, Li; Hong-ying, Yang; Pan-pan, Niu; Yong-wei, Li

    2015-03-01

    Moments and moment invariants have become a powerful tool in image processing owing to their image description capability and invariance property. But, conventional methods are mainly introduced to deal with the binary or gray-scale images, and the only approaches for color image always have poor color image description capability. Based on radial harmonic Fourier moments (RHFMs) and quaternion, we introduced the quaternion radial harmonic Fourier moments (QRHFMs) for representing color images in this paper, which can be seen as the generalization of RHFMs for gray-level images. It is shown that the QRHFMs can be obtained from the RHFMs of each color channel. We derived and analyzed the rotation, scaling, and translation (RST) invariant property of QRHFMs. We also discussed the problem of color image retrieval using invariant QRHFMs. Experimental results are provided to illustrate the efficiency of the proposed color image representation.

  17. Compression imaging based on Fourier transform optical system

    NASA Astrophysics Data System (ADS)

    Lv, Jinfeng; Zhao, Huaici; Zhao, Chunyang

    2014-11-01

    Shannon / Nyquist sampling theorem indicates that during the sampling process the minimum sample rate must be more than the double of the band of the signal so that we can achieve images without distortion. High-frequency sampling leads to mass data and results in high cost of storage and transmission procedure. Compressed sensing indicates that we can sample data at far below the Nyquist frequency when the signals are sparse or can be represented as sparse on some orthogonal basis, and the signals can be recovered without distortion after some certain recovery algorithms. By this means the cost of storage and transmission can be reduced significantly. Unlike conventional optical imaging process, this paper presents a new imaging method using a Fourier transform lens system, which enables single-exposure and single-aperture compressed imaging. First, the Fourier transformation of image signals is accomplished after they pass through a Fourier transform optical system. Second, sparse sample data can be obtained after the spectrum signals pass the sensor array. The process mentioned above can be interpreted as that using a Fourier matrix and a sparse matrix to complete the measurement of the image signals. Third, we make use of fast iterative threshold recovery algorithm to compute the sampling values and obtain the target image signals. Compared with the conventional imaging methods, in the case of ensuring the image quality, our method can significantly reduce the number of samples, thus greatly reduce the data redundancy. Simulation results indicate that the imaging method proposed can be prospective.

  18. Geosynchronous Imaging Fourier Transform Spectrometer (GIFTS): Imaging and Tracking Capability

    NASA Technical Reports Server (NTRS)

    Zhou, D. K.; Larar, A. M.; Liu, Xu; Reisse, R. A.; Smith, W. L.; Revercomb, H. E.; Bingham, G. E.; Zollinger, L. J.; Tansock, J. J.; Huppi, Ronald J.

    2007-01-01

    The geosynchronous-imaging Fourier transform spectrometer (GIFTS) engineering demonstration unit (EDU) is an imaging infrared spectrometer designed for atmospheric soundings. It measures the infrared spectrum in two spectral bands (14.6 to 8.8 microns, 6.0 to 4.4 microns) using two 128 128 detector arrays with a spectral resolution of 0.57/cm with a scan duration of approx. 11 seconds. From a geosynchronous orbit, the instrument will have the capability of taking successive measurements of such data to scan desired regions of the globe, from which atmospheric status, cloud parameters, wind field profiles, and other derived products can be retrieved. The GIFTS EDU provides a flexible and accurate testbed for the new challenges of the emerging hyperspectral era. The EDU ground-based measurement experiment, held in Logan, Utah during September 2006, demonstrated its extensive capabilities and potential for geosynchronous and other applications (e.g., Earth observing environmental measurements). This paper addresses the experiment objectives and overall performance of the sensor system with a focus on the GIFTS EDU imaging capability and proof of the GIFTS measurement concept.

  19. Electro-Optical Imaging Fourier-Transform Spectrometer

    NASA Technical Reports Server (NTRS)

    Chao, Tien-Hsin; Zhou, Hanying

    2006-01-01

    An electro-optical (E-O) imaging Fourier-transform spectrometer (IFTS), now under development, is a prototype of improved imaging spectrometers to be used for hyperspectral imaging, especially in the infrared spectral region. Unlike both imaging and non-imaging traditional Fourier-transform spectrometers, the E-O IFTS does not contain any moving parts. Elimination of the moving parts and the associated actuator mechanisms and supporting structures would increase reliability while enabling reductions in size and mass, relative to traditional Fourier-transform spectrometers that offer equivalent capabilities. Elimination of moving parts would also eliminate the vibrations caused by the motions of those parts. Figure 1 schematically depicts a traditional Fourier-transform spectrometer, wherein a critical time delay is varied by translating one the mirrors of a Michelson interferometer. The time-dependent optical output is a periodic representation of the input spectrum. Data characterizing the input spectrum are generated through fast-Fourier-transform (FFT) post-processing of the output in conjunction with the varying time delay.

  20. Optical color image hiding scheme by using Gerchberg-Saxton algorithm in fractional Fourier domain

    NASA Astrophysics Data System (ADS)

    Chen, Hang; Du, Xiaoping; Liu, Zhengjun; Yang, Chengwei

    2015-03-01

    We proposed an optical color image hiding algorithm based on Gerchberg-Saxton retrieval algorithm in fractional Fourier domain. The RGB components of the color image are converted into a scrambled image by using 3D Arnold transform before the hiding operation simultaneously and these changed images are regarded as the amplitude of fractional Fourier spectrum. Subsequently the unknown phase functions in fractional Fourier domain are calculated by the retrieval algorithm, in which the host RBG components are the part of amplitude of the input functions. The 3D Arnold transform is performed with different parameters to enhance the security of the hiding and extracting algorithm. Some numerical simulations are made to test the validity and capability of the proposed color hiding encryption algorithm.

  1. Fourier Power Spectrum Characteristics of Face Photographs: Attractiveness Perception Depends on Low-Level Image Properties

    PubMed Central

    Langner, Oliver; Wiese, Holger; Redies, Christoph

    2015-01-01

    We investigated whether low-level processed image properties that are shared by natural scenes and artworks – but not veridical face photographs – affect the perception of facial attractiveness and age. Specifically, we considered the slope of the radially averaged Fourier power spectrum in a log-log plot. This slope is a measure of the distribution of special frequency power in an image. Images of natural scenes and artworks possess – compared to face images – a relatively shallow slope (i.e., increased high spatial frequency power). Since aesthetic perception might be based on the efficient processing of images with natural scene statistics, we assumed that the perception of facial attractiveness might also be affected by these properties. We calculated Fourier slope and other beauty-associated measurements in face images and correlated them with ratings of attractiveness and age of the depicted persons (Study 1). We found that Fourier slope – in contrast to the other tested image properties – did not predict attractiveness ratings when we controlled for age. In Study 2A, we overlaid face images with random-phase patterns with different statistics. Patterns with a slope similar to those in natural scenes and artworks resulted in lower attractiveness and higher age ratings. In Studies 2B and 2C, we directly manipulated the Fourier slope of face images and found that images with shallower slopes were rated as more attractive. Additionally, attractiveness of unaltered faces was affected by the Fourier slope of a random-phase background (Study 3). Faces in front of backgrounds with statistics similar to natural scenes and faces were rated as more attractive. We conclude that facial attractiveness ratings are affected by specific image properties. An explanation might be the efficient coding hypothesis. PMID:25835539

  2. Seafood freshness determination through vapour phase Fourier transform infrared spectroscopy

    Microsoft Academic Search

    S. Armenta; N. M. M. Coelho; R. Roda; S. Garrigues; M. de la Guardia

    2006-01-01

    A new vapour-phase manifold has been developed to determine trimethylamine (TMA) in fish and cephalopod samples by Fourier transform infrared (FT-IR) spectroscopy. Samples were treated off-line for 1h with trichloroacetic acid (TCA), filtered and washed. The obtained extracts were aspirated and alkalinized with NaOH 2.0M, in an on-line system. TMA was separated from the solution in a gas phase separator

  3. Image Processing and the Arithmetic Fourier Trans-form

    NASA Astrophysics Data System (ADS)

    Tufts, Donald W.; Fan, Zhigang; Cao, Z.

    1989-05-01

    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 paper, 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 the filter array.

  4. Fourier reconstruction in spotlight mode SAR imaging

    Microsoft Academic Search

    Hong Wen; Mao Shiyi

    1996-01-01

    The spotlight mode SAR imaging procedure can be modeled in two ways. One is from the projectional information introduced from computer-aided tomography (CAT) founded on the projection-slice theorem. By quoting the concept “projection” from CAT to microwave imaging, the spotlight mode SAR can be interpreted as a narrow band tomography reconstruction problem in the far field and small rotation angle

  5. Diagnostic ultrasound tooth imaging using fractional Fourier transform.

    PubMed

    Harput, Sevan; Evans, Tony; Bubb, Nigel; Freear, Steven

    2011-10-01

    An ultrasound contact imaging method is proposed to measure the enamel thickness in the human tooth. A delay-line transducer with a working frequency of 15 MHz is chosen to achieve a minimum resolvable distance of 400 ?m in human enamel. To confirm the contact between the tooth and the transducer, a verification technique based on the phase shift upon reflection is used. Because of the high attenuation in human teeth, linear frequency-modulated chirp excitation and pulse compression are exploited to increase the penetration depth and improve the SNR. Preliminary measurements show that the enamel-dentin boundary creates numerous internal reflections, which cause the applied chirp signals to interfere arbitrarily. In this work, the fractional Fourier transform (FrFT) is employed for the first time in dental imaging to separate chirp signals overlapping in both time and frequency domains. The overlapped chirps are compressed using the FrFT and matched filter techniques. Micro-computed tomography is used for validation of the ultrasound measurements for both techniques. For a human molar, the thickness of the enamel layer is measured with an average error of 5.5% after compressing with the FrFT and 13.4% after compressing with the matched filter based on the average speed of sound in human teeth. PMID:21989873

  6. Aperture-scanning Fourier ptychography for 3D refocusing and super-resolution macroscopic imaging.

    PubMed

    Dong, Siyuan; Horstmeyer, Roarke; Shiradkar, Radhika; Guo, Kaikai; Ou, Xiaoze; Bian, Zichao; Xin, Huolin; Zheng, Guoan

    2014-06-01

    We report an imaging scheme, termed aperture-scanning Fourier ptychography, for 3D refocusing and super-resolution macroscopic imaging. The reported scheme scans an aperture at the Fourier plane of an optical system and acquires the corresponding intensity images of the object. The acquired images are then synthesized in the frequency domain to recover a high-resolution complex sample wavefront; no phase information is needed in the recovery process. We demonstrate two applications of the reported scheme. In the first example, we use an aperture-scanning Fourier ptychography platform to recover the complex hologram of extended objects. The recovered hologram is then digitally propagated into different planes along the optical axis to examine the 3D structure of the object. We also demonstrate a reconstruction resolution better than the detector pixel limit (i.e., pixel super-resolution). In the second example, we develop a camera-scanning Fourier ptychography platform for super-resolution macroscopic imaging. By simply scanning the camera over different positions, we bypass the diffraction limit of the photographic lens and recover a super-resolution image of an object placed at the far field. This platform's maximum achievable resolution is ultimately determined by the camera's traveling range, not the aperture size of the lens. The FP scheme reported in this work may find applications in 3D object tracking, synthetic aperture imaging, remote sensing, and optical/electron/X-ray microscopy. PMID:24921553

  7. Ultrasound elasticity imaging using Fourier based speckle tracking algorithm

    Microsoft Academic Search

    S. Y. Yemelyanov; A. R. Skovoroda; M. A. Lubinski; B. M. Shapo; M. O'Donnell

    1992-01-01

    Quantitative strain images of tissue equivalent phantoms have been obtained for a number of conditions using Fourier-based speckle tracking methods. Experimental results demonstrate that a non-palpable inclusion with Young's modulus only 3 times greater than surrounding material can be easily detected. Comparison of experimental results with theoretical simulations quantifies the overall accuracy of the method

  8. Fourier-ring descriptor to characterize rare circulating cells from images generated using immunofluorescence microscopy.

    PubMed

    Emerson, Tegan; Kirby, Michael; Bethel, Kelly; Kolatkar, Anand; Luttgen, Madelyn; O'Hara, Stephen; Newton, Paul; Kuhn, Peter

    2015-03-01

    We address the problem of subclassification of rare circulating cells using data driven feature selection from images of candidate circulating tumor cells from patients diagnosed with breast, prostate, or lung cancer. We determine a set of low level features which can differentiate among candidate cell types. We have implemented an image representation based on concentric Fourier rings (FRDs) which allow us to exploit size variations and morphological differences among cells while being rotationally invariant. We discuss potential clinical use in the context of treatment monitoring for cancer patients with metastatic disease. PMID:25456146

  9. Pansharpening of multispectral images using filtering in Fourier domain

    NASA Astrophysics Data System (ADS)

    Akoguz, Alper; Kurt, Burak; Pinar, Sedef K.

    2014-10-01

    In this study, there is examined filtering based pansharpening methods which means of using several 2D FIR filters in Fourier domain which implies that the filters are applied after taking 2D Discrete Fourier Transform of both multispectral and panchromatic image and after the pansharpening process in Fourier domain, the resulting pansharpened image is obtained with an inverse 2D DFT. In addition, these methods are compared with commonly used fusion methods which are combined as modulation based and component substitution based methods. The algorithms are applied to SPOT 6 co-registered image couples that were acquired simultaneously. Couples are chosen for three different regions which are a city image (Gebze/Turkey), a forest image (Istanbul/Turkey) and an agriculture field image (Sanliurfa/Turkey) in order to analyse the methods in different regional characteristics. These methods are compared by the fusion quality assessments that have common acceptance in community. The results of these quality assessments shows the filtering based methods had the best scores among the traditional methods.

  10. Image encryption based on interference that uses fractional Fourier domain asymmetric keys.

    PubMed

    Rajput, Sudheesh K; Nishchal, Naveen K

    2012-04-01

    We propose an image encryption technique based on the interference principle and phase-truncation approach in the fractional Fourier domain. The proposed scheme offers multiple levels of security with asymmetric keys and is free from the silhouette problem. Multiple input images bonded with random phase masks are independently fractional Fourier transformed. Amplitude truncation of obtained spectrum helps generate individual and universal keys while phase truncation generates two phase-only masks analytically. For decryption, these two phase-only masks optically interfere, and this results in the phase-truncated function in the output. After using the correct random phase mask, universal key, individual key, and fractional orders, the original image is retrieved successfully. Computer simulation results with four gray-scale images validate the proposed method. To measure the effectiveness of the proposed method, we calculated the mean square error between the original and the decrypted images. In this scheme, the encryption process and decryption keys formation are complicated and should be realized digitally. For decryption, an optoelectronic scheme has been suggested. PMID:22505061

  11. Infrared small target enhancement via phase spectrum of Quaternion Fourier Transform

    NASA Astrophysics Data System (ADS)

    Qi, Shengxiang; Ma, Jie; Li, Hang; Zhang, Shuiping; Tian, Jinwen

    2014-01-01

    Small target enhancement is one of the crucial stages in infrared small target detection. In this paper, we propose a new method using phase spectrum of Quaternion Fourier Transform to enhance small targets while suppressing backgrounds for infrared images. This is inspired by the property that regularly Gaussian-like shape small targets could be considered as attractively salient signal in infrared images and the location information of such signal is implicitly contained in the phase spectrum from frequency domain. Formally, in the proposed method, we adopt the phase spectrum of Quaternion Fourier Transform instead of using traditional Fourier Transform to enhance the targets since the quaternion provides at most four data channels than only one for the latter, which could be helpful to broad types of background clutters by adding more information. For the construction of the quaternion, we present a second-order directional derivative filter via facet model to compute four second order directional derivative maps from four directions respectively as the four data channels. This filter is used to suppress noises and distinguish the targets and backgrounds into separably different textures so that it would boost the robustness of small target enhancement. In experiments, some typical infrared images with various scenes are tested to validate the effectiveness of the proposed method. The results demonstrate that our method actually has good performance and outperforms several state-of-the-art methods, which can be further used for infrared small target detection and tracking.

  12. Asymmetric multiple-image encryption based on coupled logistic maps in fractional Fourier transform domain

    NASA Astrophysics Data System (ADS)

    Sui, Liansheng; Duan, Kuaikuai; Liang, Junli; Zhang, Zhiqiang; Meng, Haining

    2014-11-01

    A multiple-image encryption scheme is proposed based on the asymmetric technique, in which the encryption keys are not identical to the decryption ones. First, each plain image is scrambled based on a sequence of chaotic pairs generated with a system of two symmetrically coupled identical logistic maps. Then, the phase-only function of each scrambled image is retrieved with an iterative phase retrieval process in the fractional Fourier transform domain. Second, all phase-only functions are modulated into an interim, which is encrypted into the ciphertext with stationary white noise distribution by using the fractional Fourier transform and chaotic diffusion. In the encryption process, three random phase functions are used as encryption keys to retrieve the phase-only functions of plain images. Simultaneously, three decryption keys are generated in the encryption process, which make the proposed encryption scheme has high security against various attacks, such as chosen plaintext attack. The peak signal-to-noise is used to evaluate the quality of the decrypted image, which shows that the encryption capacity of the proposed scheme is enhanced considerably. Numerical simulations demonstrate the validity and efficiency of the proposed method.

  13. Binary-Phase Fourier Gratings for Nonuniform Array Generation

    NASA Technical Reports Server (NTRS)

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

    2003-01-01

    We describe a design method for a binary-phase Fourier grating that generates an array of spots 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 final spot array. Unlike the Dammann fanout grating approach, this method allows for the generation of nonuniform, user-defined intensities within the final fanout pattern. Restrictions governing the specification and realization of the array's individual spot intensities are discussed. Design methods used to realize the grating employ both simulated annealing and nonlinear optimization approaches to locate optimal solutions to the grating design problem. The end-use application driving this development operates in the near- to mid-infrared spectrum - allowing for higher resolution in grating specification and fabrication with respect to wavelength than may be available in visible spectrum applications. Fabrication of a grating generating a user-defined nine spot pattern is accomplished in GaAs for the near-infrared. Characterization of the grating is provided through the measurement of individual spot intensities, array uniformity, and overall efficiency. Final measurements are compared to calculated values with a discussion of the results.

  14. A phase space model of Fourier ptychographic microscopy

    PubMed Central

    Horstmeyer, Roarke; Yang, Changhuei

    2014-01-01

    A new computational imaging technique, termed Fourier ptychographic microscopy (FPM), uses a sequence of low-resolution images captured under varied illumination to iteratively converge upon a high-resolution complex sample estimate. Here, we propose a mathematical model of FPM that explicitly connects its operation to conventional ptychography, a common procedure applied to electron and X-ray diffractive imaging. Our mathematical framework demonstrates that under ideal illumination conditions, conventional ptychography and FPM both produce datasets that are mathematically linked by a linear transformation. We hope this finding encourages the future cross-pollination of ideas between two otherwise unconnected experimental imaging procedures. In addition, the coherence state of the illumination source used by each imaging platform is critical to successful operation, yet currently not well understood. We apply our mathematical framework to demonstrate that partial coherence uniquely alters both conventional ptychography’s and FPM’s captured data, but up to a certain threshold can still lead to accurate resolution-enhanced imaging through appropriate computational post-processing. We verify this theoretical finding through simulation and experiment. PMID:24514995

  15. A phase space model of Fourier ptychographic microscopy.

    PubMed

    Horstmeyer, Roarke; Yang, Changhuei

    2014-01-13

    A new computational imaging technique, termed Fourier ptychographic microscopy (FPM), uses a sequence of low-resolution images captured under varied illumination to iteratively converge upon a high-resolution complex sample estimate. Here, we propose a mathematical model of FPM that explicitly connects its operation to conventional ptychography, a common procedure applied to electron and X-ray diffractive imaging. Our mathematical framework demonstrates that under ideal illumination conditions, conventional ptychography and FPM both produce datasets that are mathematically linked by a linear transformation. We hope this finding encourages the future cross-pollination of ideas between two otherwise unconnected experimental imaging procedures. In addition, the coherence state of the illumination source used by each imaging platform is critical to successful operation, yet currently not well understood. We apply our mathematical framework to demonstrate that partial coherence uniquely alters both conventional ptychography's and FPM's captured data, but up to a certain threshold can still lead to accurate resolution-enhanced imaging through appropriate computational post-processing. We verify this theoretical finding through simulation and experiment. PMID:24514995

  16. Detecting correlation functions of ultracold atoms through Fourier sampling of time-of-flight images

    E-print Network

    L. -M. Duan

    2005-11-28

    We propose a detection method for ultracold atoms which allows reconstruction of the full one-particle and two-particle correlation functions from the measurements. The method is based on Fourier sampling of the time-of-flight images through two consecutive impulsive Raman pulses. For applications of this method, we discuss a few examples, including detection of phase separation between superfluid and Mott insulators, various types of spin or superfluid orders, entanglement, exotic or fluctuating orders.

  17. Fourier-processed images of dynamic lung function from list-mode data

    SciTech Connect

    Zubal, I.G.; Rowe, R.W.; Bizais, Y.; Susskind, H.; Bennett, G.W.; Brill, A.B.

    1983-01-01

    Time and volume correlated amplitude and phase images are computed from nuclear medical ventilation studies and for dynamic transmission scans of the lungs. This is made possible by a hardware interface and data acquisition system, developed in-house, allowing camera events and multiple ancillary physiological signals (including lung volume) to be acquired simultaneously in list mode. The first harmonic amplitude and phase images are constructed on an event by event basis. These are computed for both equal time and equal lung volume increments. Time and volume correlated Fourier images for ventilation studies have shown details and functional structures not usually seen in conventional imaging techniques. Processed transmission scans show similar results compared to ventilation images.

  18. Geometric phase analysis based on the windowed Fourier transform for the deformation field measurement

    NASA Astrophysics Data System (ADS)

    Dai, Xianglu; Xie, Huimin; Wang, Qinghua

    2014-06-01

    The geometric phase analysis (GPA), an important image-based deformation measurement method, has been used at both micro- and nano-scale. However, when a deformed image has apparent distortion, non-ignorable error in the obtained deformation field could occur by using this method. In this paper, the geometric phase analysis based on the windowed Fourier transform (WFT) is proposed to solve the above-mentioned issue, defined as the WFT-GPA method. In WFT-GPA, instead of the Fourier transform (FT), the WFT is utilized to extract the phase field block by block, and therefore more accurate local phase information can be acquired. The simulation tests, which include detailed discussion of influence factors for measurement accuracy such as window size and image noise, are conducted with digital deformed grids. The results verify that the WFT-GPA method not only keeps all advantages of traditional GPA method, but also owns a better accuracy for deformation measurement. Finally, the WFT-GPA method is applied to measure the machining distortion incurred in soft ultraviolet nanoimprint lithography (UV-NIL) process. The successful measurement shows the feasibility of this method and offers a full-field way for characterizing the replication quality of UV-NIL process.

  19. Phase retrieval in computer generated schlieren images

    SciTech Connect

    Fiadeiro, P.T.; Emmony, D.C. [Loughborough Univ. of Technology (United Kingdom). Dept. of Physics

    1995-12-31

    The Schlieren technique involves the manipulation of knife edges to limit the field of view in the image formation process. Practical implementation of this technique is not easy due to difficulties in positioning the knife edge in the optical system. A related problem concerns the reproducibility of an event to generate a series of schlieren images for different knife edge positions. A particularly successful method to overcome this problem is the use of the computer to generate such images from single pictures of the event. Computer generation of schlieren images involves the inverse Fourier transformation of the modified complex-valued diffraction pattern (magnitude and phase) of the event. Recording media in general respond only to light intensity and no difficulty is encountered in recording the intensity, and therefore the magnitude. The phase is either unobservable directly or cannot be determined anywhere nearly as accurately as the intensity. The Gerchberg and Saxton iterative algorithm is used to recover the phase from records of intensity (magnitude) taken from the image and Fourier domains of the optical system. The knowledge of magnitude and phase in the Fourier domain (diffraction pattern) will enable one to modify it through a computer knife edge and generate the corresponding schlieren images.

  20. System calibration of Stokes imaging polarimeter using Fourier series analysis

    NASA Astrophysics Data System (ADS)

    Meng, Xin; Li, Jianxin; Zhang, Yumei; Zhu, Rihong

    2014-11-01

    The Stokes imaging polarimeter using a retarder and a polarizer is a direct and conventional method to detect the full Stokes vector of the scene. This method has been widely used for different imaging architectures, such as division of time and division of aperture. System calibration is necessary in polarimetric imagery. The polarization optical elements angular deviation belongs to adjustment error and should be calibration when the device is set up. In this paper we propose a novel method to calibration the angular deviation using Fourier series analysis. A linear polarization state generator including a light source and a linear polarizer is installed before the imaging polarimeter. The polarizer rotates 360-degree uniform and the signal intensity of the input light is recorded by the imaging polarimeter. The angle of the fast axis of the quarter-waveplate respect to the pass axis of the polarizer can be calculated from the obtained data by use of Fourier series analysis. The mathematic model of the presented method is established and proved by mathematical simulation.

  1. Imaging the sun in hard x rays using Fourier telescopes

    NASA Technical Reports Server (NTRS)

    Campbell, J. W.

    1993-01-01

    For several years, solar flares have been observed with a variety of instruments confirming that tremendous amounts of energy are locally stored in the solar magnetic field and then rapidly released during the life of the flare. In concert with observations, theorists have attempted to describe the means by which these energetic events occur and evolve. Two competing theories have emerged and have stood the test of time. One theory describes the flare in terms of nonthermal, electron beam injection into a thick target while the other uses a thermal approach. Both theories provide results which are reasonably consistent with current observations; but to date, none have been able to provide conclusive evidence as to the validity of either model. Imaging on short time scales (1 s) and/or small size scales (1 arc s) should give definitive answers to these questions. In order to test whether a realistic telescope can indeed discriminate between models, we construct model sources based upon the thermal and the nonthermal models and calculate the emission as a function of time and energy in the range from 10 to 100 keV. In addition, we construct model telescopes representing both the spatial modulation collimator (SMC) and the rotating modulation collimator (RMC) techniques of observation using random photon counting statistics. With these two types of telescopes we numerically simulate the instrument response to the above two model flares to see if there are distinct x-ray signatures which may be discernable. We find that theoretical descriptions of the primary models of solar flares do indeed predict different hard x-ray signatures for 1 sec time scales and at 1-5 arc sec spatial resolution. However, these distinguishing signatures can best be observed early in the impulsive phase and from a position perpendicular to the plane of the loop. Furthermore, we find that Fourier telescopes with reasonable and currently attainable design characteristics can image these signatures and that the same sensitive areas and short temporal integration times relative to source evolution (i.e., 1 s), the RMC and the SMC will both provide about the same performance.

  2. Imaging Organ of Corti Vibration Using Fourier-Domain OCT

    NASA Astrophysics Data System (ADS)

    Choudhury, Niloy; Chen, Fangyi; Fridberger, Anders; Zha, Dingjun; Jacques, Steven L.; Wang, Ruikang K.; Nuttall, Alfred L.

    2011-11-01

    Measuring the sound stimulated vibration from various structures in the organ of Corti is important in understanding how the small vibrations are amplified and detected. In this study we examine the feasibility of using phase-sensitive Fourier domain optical coherence tomography (PSFD-OCT) to measure vibration of the cellular structures of the organ of Corti. PSFD-OCT is a low coherence interferrometry system where the interferrogram is detected as a function of wavelength. The phase of the Fourier transformation of the detected spectra contains path deference (between the sample arm and the reference arm) information of the interferometer. In PSFD-OCT this phase is measured as a function of time and thus any time dependent change in the path difference between the sample arm and the reference arm can be detected. In the experiment, we used an in vitro preparation of the guinea pig cochlea and made a surgical opening at the apical end to access the organ of Corti. By applying tones with different frequencies via the intact middle ear, we recorded the structural vibration inside the organ of Corti. Vibration amplitude and phase of different substructures were mapped on a cross-section view of the organ of Corti. Although the measurements were made at the apical turn of the cochlea, it will be possible to make vibration measurement from various turns of the cochlea. The noise floor of the system was 0.3 nm, calibrated using a piezo stack as a calibrator.

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

    PubMed

    Wicker, Kai

    2013-10-21

    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

  4. Instrument concept of the imaging Fourier transform spectrometer GLORIA

    NASA Astrophysics Data System (ADS)

    Friedl-Vallon, F.; Gulde, T.; Hase, F.; Kleinert, A.; Kulessa, T.; Maucher, G.; Neubert, T.; Olschewski, F.; Piesch, C.; Preusse, P.; Rongen, H.; Sartorius, C.; Schneider, H.; Schönfeld, A.; Tan, V.; Bayer, N.; Blank, J.; Dapp, R.; Ebersoldt, A.; Fischer, H.; Graf, F.; Guggenmoser, T.; Höpfner, M.; Kaufmann, M.; Kretschmer, E.; Latzko, T.; Nordmeyer, H.; Oelhaf, H.; Orphal, J.; Riese, M.; Schardt, G.; Schillings, J.; Sha, M. K.; Suminska-Ebersoldt, O.; Ungermann, J.

    2014-03-01

    The Gimballed Limb Observer for Radiance Imaging of the Atmosphere (GLORIA) is an imaging limb emission sounder operating in the thermal infrared region. It is designed to provide measurements of the Upper Troposphere/Lower Stratosphere with high spatial and high spectral resolution. The instrument consists of an imaging Fourier transform spectrometer integrated in a gimbal. The assembly can be mounted in the belly pod of the German high altitude and long range research aircraft HALO and in instrument bays of the Russian M55 Geophysica. Measurements are made predominantly in two distinct modes: the chemistry mode emphasises chemical analysis with high spectral resolution, the dynamics mode focuses on dynamical processes of the atmosphere with very high spatial resolution. In addition the instrument allows tomographic analyses of air volumes. The first measurement campaigns have shown compliance with key performance and operational requirements.

  5. Instrument concept of the imaging Fourier transform spectrometer GLORIA

    NASA Astrophysics Data System (ADS)

    Friedl-Vallon, F.; Gulde, T.; Hase, F.; Kleinert, A.; Kulessa, T.; Maucher, G.; Neubert, T.; Olschewski, F.; Piesch, C.; Preusse, P.; Rongen, H.; Sartorius, C.; Schneider, H.; Schönfeld, A.; Tan, V.; Bayer, N.; Blank, J.; Dapp, R.; Ebersoldt, A.; Fischer, H.; Graf, F.; Guggenmoser, T.; Höpfner, M.; Kaufmann, M.; Kretschmer, E.; Latzko, T.; Nordmeyer, H.; Oelhaf, H.; Orphal, J.; Riese, M.; Schardt, G.; Schillings, J.; Sha, M. K.; Suminska-Ebersoldt, O.; Ungermann, J.

    2014-10-01

    The Gimballed Limb Observer for Radiance Imaging of the Atmosphere (GLORIA) is an imaging limb emission sounder operating in the thermal infrared region. It is designed to provide measurements of the upper troposphere/lower stratosphere with high spatial and high spectral resolution. The instrument consists of an imaging Fourier transform spectrometer integrated into a gimbal. The assembly can be mounted in the belly pod of the German High Altitude and Long Range research aircraft (HALO) and in instrument bays of the Russian M55 Geophysica. Measurements are made in two distinct modes: the chemistry mode emphasises chemical analysis with high spectral resolution, and the dynamics mode focuses on dynamical processes of the atmosphere with very high spatial resolution. In addition, the instrument allows tomographic analyses of air volumes. The first measurement campaigns have shown compliance with key performance and operational requirements.

  6. The use of Fourier reverse transforms in crystallographic phase refinement

    SciTech Connect

    Ringrose, S.

    1997-10-08

    Often a crystallographer obtains an electron density map which shows only part of the structure. In such cases, the phasing of the trial model is poor enough that the electron density map may show peaks in some of the atomic positions, but other atomic positions are not visible. There may also be extraneous peaks present which are not due to atomic positions. A method for determination of crystal structures that have resisted solution through normal crystallographic methods has been developed. PHASER is a series of FORTRAN programs which aids in the structure solution of poorly phased electron density maps by refining the crystallographic phases. It facilitates the refinement of such poorly phased electron density maps for difficult structures which might otherwise not be solvable. The trial model, which serves as the starting point for the phase refinement, may be acquired by several routes such as direct methods or Patterson methods. Modifications are made to the reverse transform process based on several assumptions. First, the starting electron density map is modified based on the fact that physically the electron density map must be non-negative at all points. In practice a small positive cutoff is used. A reverse Fourier transform is computed based on the modified electron density map. Secondly, the authors assume that a better electron density map will result by using the observed magnitudes of the structure factors combined with the phases calculated in the reverse transform. After convergence has been reached, more atomic positions and less extraneous peaks are observed in the refined electron density map. The starting model need not be very large to achieve success with PHASER; successful phase refinement has been achieved with a starting model that consists of only 5% of the total scattering power of the full molecule. The second part of the thesis discusses three crystal structure determinations.

  7. High fidelity magnetic resonance imaging by frequency sweep encoding and Fourier Jun Shen *, Yun Xiang

    E-print Network

    Shen, Jun

    High fidelity magnetic resonance imaging by frequency sweep encoding and Fourier decoding Jun Shen February 2010 Available online 20 February 2010 Keywords: Magnetic resonance imaging Encoding Decoding The dominating schemes for magnetic resonance imaging have been based on the Fourier transform relationship

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

    SciTech Connect

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

    2007-01-31

    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.

  9. Fractional Fourier plane image encryption technique using radial hilbert-, and Jigsaw transform

    NASA Astrophysics Data System (ADS)

    Joshi, Madhusudan; Shakher, Chandra; Singh, Kehar

    2010-07-01

    A new method for image encryption using integral order radial Hilbert transform (RHT) filter in the fractional Fourier transform (FRT) domain has been proposed. The technique is implemented using the popular double random phase encoding method in the fractional Fourier domain. The random phase masks (RPMs), integral orders of the RHT, fractional orders of FRT, and indices of the Jigsaw transform (JT) have been used as keys for encryption and decryption. Simulation results have been presented and the schematic representation for optical implementation has been proposed. The mean-square-error and signal-to-noise ratio between the decrypted image and the input image have been calculated for the correct as well as incorrect orders of the RHT. Effect of occlusion and noise on the performance of the proposed scheme has also been studied. The robustness of the technique has been verified against attack using partial windows of the correct random phase masks. Similar investigations have also been carried out for the chosen-, and the known-plain-text attacks.

  10. Continued Development of a Planetary Imaging Fourier Transform Spectrometer (PIFTS)

    NASA Technical Reports Server (NTRS)

    Sromovsky, L. A.

    2002-01-01

    This report describes continued efforts to evaluate a breadboard of a Planetary Imaging Fourier Transform Spectrometer (PIFTS). The PIFTS breadboard was developed under prior PIDDP funding. That effort is described in the final report for NASA Grant NAG5-6248 and in two conference papers (Sromovsky et al. 2000; Revercomb et al. 2000). The PIFTS breadboard was designed for near-IR (1-5.2 micrometer imaging of planetary targets with spectral resolving powers of several hundred to several thousand, using an InSb detector array providing at least 64x64 pixels imaging detail. The major focus of the development effort was to combine existing technologies to produce a small and low power design compatible with a very low mass flyable instrument. The objective of this grant (NAG5-10729) was further characterization of the breadboard performance, including intercomparisons with the highly accurate non-imaging Advanced Emitted Radiance Interferometer (AERI) (Revercomb et al. 1994; Best et al. 1997).

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

    NASA Astrophysics Data System (ADS)

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

    2012-08-01

    Authors present the discrimination performances of amplitude and phase-only Fourier correlation over the "twin" typed GC-spectra of sheep milk and ripened cheese. Therefore, in order to assess the most robust Fourier correlation method for the "twin" GC-spectra discrimination, the correlation matrix is built up over 17 analyzed GC-spectra in both amplitude and phase domains.

  12. Multiple-image encryption scheme based on cascaded fractional Fourier transform.

    PubMed

    Kong, Dezhao; Shen, Xueju; Xu, Qinzu; Xin, Wang; Guo, Haiqiong

    2013-04-20

    A multiple-image encryption scheme based on cascaded fractional Fourier transform is proposed. In the scheme, images are successively coded into the amplitude and phase of the input by cascading stages, which ends up with an encrypted image and a series of keys. The scheme takes full advantage of multikeys and the cascaded relationships of all stages, and it not only realizes image encryption but also achieves higher safety and more diverse applications. So multiuser authentication and hierarchical encryption are achieved. Numerical simulation verifies the feasibility of the method and demonstrates the security of the scheme and decryption characteristics. Finally, flexibility and variability of the scheme in application are discussed, and the simple photoelectric mixed devices to realize the scheme are proposed. PMID:23669669

  13. Multiresolution graph Fourier transform for compression of piecewise smooth images.

    PubMed

    Hu, Wei; Cheung, Gene; Ortega, Antonio; Au, Oscar C

    2015-01-01

    Piecewise smooth (PWS) images (e.g., depth maps or animation images) contain unique signal characteristics such as sharp object boundaries and slowly varying interior surfaces. Leveraging on recent advances in graph signal processing, in this paper, we propose to compress the PWS images using suitable graph Fourier transforms (GFTs) to minimize the total signal representation cost of each pixel block, considering both the sparsity of the signal's transform coefficients and the compactness of transform description. Unlike fixed transforms, such as the discrete cosine transform, we can adapt GFT to a particular class of pixel blocks. In particular, we select one among a defined search space of GFTs to minimize total representation cost via our proposed algorithms, leveraging on graph optimization techniques, such as spectral clustering and minimum graph cuts. Furthermore, for practical implementation of GFT, we introduce two techniques to reduce computation complexity. First, at the encoder, we low-pass filter and downsample a high-resolution (HR) pixel block to obtain a low-resolution (LR) one, so that a LR-GFT can be employed. At the decoder, upsampling and interpolation are performed adaptively along HR boundaries coded using arithmetic edge coding, so that sharp object boundaries can be well preserved. Second, instead of computing GFT from a graph in real-time via eigen-decomposition, the most popular LR-GFTs are pre-computed and stored in a table for lookup during encoding and decoding. Using depth maps and computer-graphics images as examples of the PWS images, experimental results show that our proposed multiresolution-GFT scheme outperforms H.264 intra by 6.8 dB on average in peak signal-to-noise ratio at the same bit rate. PMID:25494508

  14. Discussion and a new attack of the optical asymmetric cryptosystem based on phase-truncated Fourier transform.

    PubMed

    Wang, Xiaogang; Chen, Yixiang; Dai, Chaoqing; Zhao, Daomu

    2014-01-10

    A discussion and a cryptanalysis of the optical phase-truncated Fourier-transform-based cryptosystem are presented in this paper. The concept of an optical asymmetric cryptosystem, which was introduced into the optical image encryption scheme based on phase-truncated Fourier transforms in 2010, is suggested to be retained in optical encryption. A new method of attack is also proposed to simultaneously obtain the main information of the original image, the two decryption keys from its cyphertext, and the public keys based on the modified amplitude-phase retrieval algorithm. The numerical results illustrate that the computing efficiency of the algorithm is improved and the number of iterations is much less than that by the specific attack, which has two iteration loops. PMID:24514051

  15. Iterative partial phase encoding based on joint fractional Fourier transform correlator adopting phase-shifting digital holography

    NASA Astrophysics Data System (ADS)

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

    2014-02-01

    In this paper, digital holography based on two-step phase shifting interference (PSI) was applied to realize the iterative partial phase encoding with joint fractional transform correlator (JFTC). By this security system, the primitive image is encoded in two joint fractional power spectra (JFPS) corresponding to different phase-shifting values. The encrypted image can be deduced directly from the JFPSs by digital means, thus eliminating the noise interference of dc and conjugate terms. JFTC not only relaxes the alignment requirement but also avoids the beam splitting required by traditional holography. In the iterative partial phase encoding, the random phase masks (RPMs) are generated by chaotic mapping, and encoding areas are confined by a sequence of random binary masks. To recover the primitive image, decipher must regenerate the partial RPMs with correct chaotic conditions and perform inverse fractional Fourier transforms with correct orders. The decryption process can be realized by JFTC or by totally digital means. Simulation and experimental results have been presented to test security level and feasibility of the scheme.

  16. A Method to Perform a Fast Fourier Transform With Primitive Image Transformations

    Microsoft Academic Search

    Phil Sheridan

    2007-01-01

    The Fourier transform is one of the most important transformations in image processing. A major component of this influence comes from the ability to implement it efficiently on a digital computer. This paper describes a new methodology to perform a fast Fourier transform (FFT). This methodology emerges from considerations of the natural physical constraints imposed by image capture devices (camera\\/eye).

  17. Challenge for spectroscopic tomography of biomembrane using imaging type two-dimensional Fourier spectroscopy

    NASA Astrophysics Data System (ADS)

    Qi, Wei; Ishimaru, Ichiro

    2010-02-01

    We propose an image-producing Fourier spectroscopic technology that enables two-dimensional spectroscopic images to be obtained within the focusing plane alone. This technology incorporates auto-correlational phase-shift interferometry that uses only object light generated by the bright points that optically make up the object. We are currently involved in studies of non-invasive technologies used to measure blood components such as glucose and lipids, which are measured for use in daily living. Previous studies have investigated non-invasive technologies that measure blood glucose levels by utilizing near-infrared light that permeates the skin well. It has been confirmed that subtle changes in the concentration of a glucose solution, a sample used to measure the glucose level, can be measured by analyzing the spectroscopic characteristics of near-infrared light; however, when applied to a biomembrane, technology such as this is incapable of precisely measuring the glucose level because light diffusion within the skin disturbs the measurement. Our proposed technology enables two-dimensional spectroscopy to a limited depth below the skin covered by the measurement. Specifically, our technology concentrates only on the vascular territory near the skin surface, which is only minimally affected by light diffusion, as discussed previously; the spectroscopic characteristics of this territory are obtained and the glucose level can be measured with good sensitivity. In this paper we propose an image-producing Fourier spectroscopy method that is used as the measuring technology in producing a three-dimensional spectroscopic image.

  18. Spatial Phase Imaging

    NASA Technical Reports Server (NTRS)

    2006-01-01

    Frequently, scientists grow crystals by dissolving a protein in a specific liquid solution, and then allowing that solution to evaporate. The methods used next have been, variously, invasive (adding a dye that is absorbed by the protein), destructive (crushing protein/salt-crystal mixtures and observing differences between the crushing of salt and protein), or costly and time-consuming (X-ray crystallography). In contrast to these methods, a new technology for monitoring protein growth, developed in part through NASA Small Business Innovation Research (SBIR) funding from Marshall Space Flight Center, is noninvasive, nondestructive, rapid, and more cost effective than X-ray analysis. The partner for this SBIR, Photon-X, Inc., of Huntsville, Alabama, developed spatial phase imaging technology that can monitor crystal growth in real time and in an automated mode. Spatial phase imaging scans for flaws quickly and produces a 3-D structured image of a crystal, showing volumetric growth analysis for future automated growth.

  19. Rotational-translational fourier imaging system requiring only one grid pair

    NASA Technical Reports Server (NTRS)

    Campbell, Jonathan W. (Inventor)

    2006-01-01

    The sky contains many active sources that emit X-rays, gamma rays, and neutrons. Unfortunately hard X-rays, gamma rays, and neutrons cannot be imaged by conventional optics. This obstacle led to the development of Fourier imaging systems. In early approaches, multiple grid pairs were necessary in order to create rudimentary Fourier imaging systems. At least one set of grid pairs was required to provide multiple real components of a Fourier derived image, and another set was required to provide multiple imaginary components of the image. It has long been recognized that the expense associated with the physical production of the numerous grid pairs required for Fourier imaging was a drawback. Herein one grid pair (two grids), with accompanying rotation and translation, can be used if one grid has one more slit than the other grid, and if the detector is modified.

  20. Vector power multiple-parameter fractional Fourier transform of image encryption algorithm

    NASA Astrophysics Data System (ADS)

    Ran, Qiwen; Zhao, Tieyu; Yuan, Lin; Wang, Jian; Xu, Lei

    2014-11-01

    In this paper, we propose a multiple-parameter fractional Fourier transform with its transform order being a real vector, based on which a high-security image encryption scheme is also given. This novel fractional Fourier transform has removed the restriction on the dimension of transform order and highly enhances the security of image encryption scheme proposed in this paper without increasing the computational complexity and hardware cost. The numerical results verify the efficacy and security of this image encryption method. The vector power multi-parameter fractional Fourier transform is a generalized form of the classical fractional Fourier transform with all the previous fractional Fourier transform as its special cases and has theoretical significance in information processing and information security.

  1. The reconstruction of a multidimensional sequence from the phase or magnitude of its Fourier transform

    Microsoft Academic Search

    M. Hayes

    1982-01-01

    This paper addresses two fundamental issues involved in the reconstruction of a multidimensional sequence from either the phase or magnitude of its Fourier transform. The first issue relates to the uniqueness of a multidimensional sequence in terms of its phase or magnitude. Although phase or magnitude information alone is not sufficient, in general, to uniquely specify a sequence, a large

  2. Complete fourier direct magnetic resonance imaging (CFD-MRI) for diffusion MRI

    PubMed Central

    Özcan, Alpay

    2013-01-01

    The foundation for an accurate and unifying Fourier-based theory of diffusion weighted magnetic resonance imaging (DW–MRI) is constructed by carefully re-examining the first principles of DW–MRI signal formation and deriving its mathematical model from scratch. The derivations are specifically obtained for DW–MRI signal by including all of its elements (e.g., imaging gradients) using complex values. Particle methods are utilized in contrast to conventional partial differential equations approach. The signal is shown to be the Fourier transform of the joint distribution of number of the magnetic moments (at a given location at the initial time) and magnetic moment displacement integrals. In effect, the k-space is augmented by three more dimensions, corresponding to the frequency variables dual to displacement integral vectors. The joint distribution function is recovered by applying the Fourier transform to the complete high-dimensional data set. In the process, to obtain a physically meaningful real valued distribution function, phase corrections are applied for the re-establishment of Hermitian symmetry in the signal. Consequently, the method is fully unconstrained and directly presents the distribution of displacement integrals without any assumptions such as symmetry or Markovian property. The joint distribution function is visualized with isosurfaces, which describe the displacement integrals, overlaid on the distribution map of the number of magnetic moments with low mobility. The model provides an accurate description of the molecular motion measurements via DW–MRI. The improvement of the characterization of tissue microstructure leads to a better localization, detection and assessment of biological properties such as white matter integrity. The results are demonstrated on the experimental data obtained from an ex vivo baboon brain. PMID:23596401

  3. Single-Grid-Pair Fourier Telescope for Imaging in Hard-X Rays and gamma Rays

    NASA Technical Reports Server (NTRS)

    Campbell, Jonathan

    2008-01-01

    This instrument, a proposed Fourier telescope for imaging in hard-x rays and gamma rays, would contain only one pair of grids made of an appropriate radiation-absorpting/ scattering material, in contradistinction to multiple pairs of such as grids in prior Fourier x- and gamma-ray telescopes. This instrument would also include a relatively coarse gridlike image detector appropriate to the radiant flux to be imaged. Notwithstanding the smaller number of grids and the relative coarseness of the imaging detector, the images produced by the proposed instrument would be of higher quality.

  4. Parameter estimation in arterial spin labeling MRI: comparing the Four Phase model and the Buxton model with Fourier transform.

    PubMed

    Pham, Vincent; Zhu, Xiao-Ping; Li, Ka-loh; Ji, Jim Xiuquan

    2009-01-01

    This paper presents a comparison between two algorithms that analyze and extract brain perfusion parameters from pulsed arterial spin labeling (ASL). One algorithm is based on the Four Phase Single Capillary Stepwise (FPSCS) model, which divides the time course of the signal difference between the control and labeled image into four phases. The other algorithm utilizes the Buxton model and Fourier transformation (FTB). Both algorithms are implemented on MATLAB to extract the bolus arrival time (BAT) and the cerebral blood flow (CBF). Current results show that the FTB algorithm has similar estimations of the BAT and CBF compared to the FPSCS model with generally faster processing speeds. PMID:19963620

  5. Bright versus dark schlieren imaging: quantitative analysis of quasi-sinusoidal phase objects

    Microsoft Academic Search

    Ismael Núñez; José A. Ferrari

    2007-01-01

    We discuss the schlieren imaging of quasi-sinusoidal phase objects. We demonstrate that, when the zero-order (Fourier) spatial component of the input image is not blocked by the schlieren-knife at the Fourier plane, the intensity distribution on the reconstructed image is a linear function of the phase amplitude. In contrast, if the zero order is completely blocked (i.e., dark Schlieren processing),

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

    PubMed

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

    2008-07-11

    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

  7. Color image encryption based on fractional Fourier transforms and pixel scrambling technique

    Microsoft Academic Search

    Jianlin Zhao; Hongqiang Lu; Qi Fan

    2007-01-01

    Color image encryption based on fractional Fourier transform (FRT) and pixel scrambling technique is presented in this paper. In general, color (RGB) image cannot be directly encrypted using a traditional setup for optical information processing, because which is only adapted to process two-dimensional gray image. In the proposed method, a three-dimensional RGB image is decomposed to three two-dimensional gray images

  8. 3D quantitative Fourier analysis of second harmonic generation microscopy images of collagen structure in cartilage

    NASA Astrophysics Data System (ADS)

    Romijn, Elisabeth I.; Lilledahl, Magnus B.

    2013-02-01

    One of the main advantages of nonlinear microscopy is that it provides 3D imaging capability. Second harmonic generation is widely used to image the 3D structure of collagen fibers, and several works have highlighted the modification of the collagen fiber fabric in important diseases. By using an ellipsoidal specific fitting technique on the Fourier transformed image, we show, using both synthetic images and SHG images from cartilage, that the 3D direction of the collagen fibers can be robustly determined.

  9. Iterative reconstruction of speech from short-time Fourier transform phase and magnitude spectra

    E-print Network

    Iterative reconstruction of speech from short-time Fourier transform phase and magnitude spectra dimensional, signal reconstruction (specifically speech signals) from the magnitude spectrum and the phase magnitude spectrum, and (iii) a signal can be reconstructed to within a scale factor from its magnitude

  10. Phase Retrieval Between Overlapping Orders in Coherent Fourier Scatterometry Using Scanning

    NASA Astrophysics Data System (ADS)

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

    2013-07-01

    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.

  11. Phase discrepancy analysis and compensation for fast Fourier transform based solution of the transport of intensity equation.

    PubMed

    Zuo, Chao; Chen, Qian; Huang, Lei; Asundi, Anand

    2014-07-14

    The transport of intensity equation (TIE) has long been recognized as a quantitative method for phase retrieval and phase contrast imaging. However, it is shown that the most widely accepted fast Fourier transform (FFT) based solutions do not provide an exact solution to the TIE in general. The root of the problem lies in the so-called "Teague's assumption" that the transverse flux is considered to be a conservative field, which cannot be satisfied for a general object. In this work, we present the theoretical analysis of the phase discrepancy owing to the Teague's assumption, and derive the necessary and sufficient conditions for the FFT-based solution to coincide with the exact phase. An iterative algorithm is then proposed aiming to compensate such phase discrepancy in a simple yet effective manner. PMID:25090531

  12. Theory of laser array phase locking by Fourier coupling

    SciTech Connect

    Vysotskii, D V; Napartovich, A P; Troshchieva, V N [State Research Center of Russian Federation 'Troitsk Institute for Innovation and Fusion Research', Troitsk, Moscow Region (Russian Federation)

    2007-04-30

    The type of coupling in a fibre laser array phase locked with the help of an external mirror located at the focal distance from the plane of output ends of individual lasers is studied analytically. The explicit expression is derived for the eigenvalue of the resonator and the restriction on the width of the tuning range in which laser array phase locking is preserved is determined. The influence of the spread in the optical lengths of fibres on the phase-locking efficiency is considered. The phase-locking efficiency is analysed for the spread of optical lengths of fibres considerably exceeding the radiation wavelength. (control of laser radiation parameters)

  13. Avalanche and bit independence characteristics of double random phase encoding in the Fourier and Fresnel domains.

    PubMed

    Moon, Inkyu; Yi, Faliu; Lee, Yeon H; Javidi, Bahram

    2014-05-01

    In this work, we evaluate the avalanche effect and bit independence properties of the double random phase encoding (DRPE) algorithm in the Fourier and Fresnel domains. Experimental results show that DRPE has excellent bit independence characteristics in both the Fourier and Fresnel domains. However, DRPE achieves better avalanche effect results in the Fresnel domain than in the Fourier domain. DRPE gives especially poor avalanche effect results in the Fourier domain when only one bit is changed in the plaintext or in the encryption key. Despite this, DRPE shows satisfactory avalanche effect results in the Fresnel domain when any other number of bits changes in the plaintext or in the encryption key. To the best of our knowledge, this is the first report on the avalanche effect and bit independence behaviors of optical encryption approaches for bit units. PMID:24979643

  14. Optical encryption by combining image scrambling techniques in fractional Fourier domains

    NASA Astrophysics Data System (ADS)

    Liu, Shi; Sheridan, John T.

    2013-01-01

    In this paper, we propose a novel scheme for optical information hiding (encryption) of two-dimensional images by combining image scrambling techniques in fractional Fourier domains. The image is initially randomly shifted using the jigsaw transform algorithm, and then a pixel scrambling technique based on the Arnold transform (ART) is applied. The scrambled image is then encrypted in a randomly chosen fractional Fourier domain. These processes can then be iteratively repeated. The parameters of the architecture, including the jigsaw permutation indices, Arnold frequencies, and fractional Fourier orders, form a very large key space enhancing the security level of the proposed encryption system. Optical implementations are discussed as numerical implementation algorithms. Numerical simulation results are presented to demonstrate the system's flexibility and robustness.

  15. Fast and accurate computation of the Fourier transform of an image Gregory Beylkin

    E-print Network

    Beylkin, Gregory

    function f. Namely, we compute for --N m, n N (with a given accuracy ) the integrals * ,1 1 · f(m,n) = I I in image processing to simply take the FFT of the pixel values of the image in order to evaluate the Fourier transform. Due to the jump discontinuities of the function f, the accuracy of such a computation

  16. Compressed Ultrasound Imaging by Sub-Nyquist Sampling and Fourier Domain Beamforming

    E-print Network

    Eldar, Yonina

    1 Compressed Ultrasound Imaging by Sub-Nyquist Sampling and Fourier Domain Beamforming Alon Eilam the number of samples needed to reconstruct an ultrasound image. We demonstrate our methods on in vivo present an implementation on an ultrasound machine. Utilizing the low data rate, beamforming can be done

  17. Gouy phase shift in Fourier-domain optical coherence tomography

    Microsoft Academic Search

    G. Lamouche; S. Vergnole; M. L. Dufour; B. Gauthier

    2008-01-01

    A Gouy phase shift is acquired each time a beam goes through a focal point. It is a common practice in optical coherence tomography (OCT) systems to focus the light on a sample to obtain a good transverse resolution in addition to the axial resolution provided by the coherence gating. In presence of chromatic aberration, the position of the focal

  18. Realistic 3D image reconstruction in CGH with Fourier transform optical system

    NASA Astrophysics Data System (ADS)

    Ichikawa, Tsubasa; Yamaguchi, Kazuhiro; Sakamoto, Yuji

    2013-03-01

    In CGH, peculiar rendering techniques are necessary to express realistic 3D images because CGHs have parallax. We have proposed the calculation method with the ray tracing method that expresses the hidden surface removal, shading and so on. However, resolutions of current output devices are not high enough to display CGH, so the size of reconstructed images is restricted and viewing zone and visual field are very narrow. To enlarge the size of reconstructed images, the Fourier transform optical system is used. Then we introduce the technique to apply calculation method of CGH with ray tracing method to the Fourier transform optical system in this paper. The Fourier transform optical system reverses the depth of images and reconstructs pseudo stereoscopic 3D images in front of a hologram. We solved this problem by reconstructing images at the back of hologram plane and observing conjugate images. Moreover, we conducted elimination of unnecessary light including 0-th order light. We conducted optical reconstructions that show proposed method is able to make realistic CGHs implementing the hidden surface removal in the Fourier transform optical system.

  19. Ultrasound imaging of long bone fractures and healing with the split-step fourier imaging method.

    PubMed

    Li, Hongjiang; Le, Lawrence H; Sacchi, Mauricio D; Lou, Edmond H M

    2013-08-01

    We applied the split-step Fourier imaging method to back-propagate the ultrasound zero-offset wavefields acquired on the bone surface to the sources of scatterers, which are the reflecting interfaces. The method required, as an input, an estimated slowness (reciprocal of half the velocity) model to map the time-dependent sonogram to the depth image, which provides the geometric properties of the interfaces. The slowness was approximated by a depth-dependent term and a first-order spatially varying perturbation. Simulated data sets were used to validate the method. The reconstructed images show proper mapping of the interfaces and the fracture, and a reasonable cortical thickness measurement with 8.3% error. The images also illustrate clearly the bone fracture healing process of a 1-mm-wide 45° inclined crack with different in-filled tissue velocities for various healing stages. Reconstruction of a fractured bone plate using data from an in vitro experiment is also presented. This study suggests that the proposed imaging method has good potential in quantification of bone fractures and monitoring of the fracture healing process. PMID:23838363

  20. Fourier Transform Heterodyne Techniques Applied To Astronomy

    Microsoft Academic Search

    B. E. Laubscher; B. J. Cooke; B. C. Edwards

    1998-01-01

    Fourier Transform Heterodyne (FTH) is a detection process capable of directly imaging the transverse amplitude and phase of coherent electromagnetic fields. Based on coherent detection principles governing conventional heterodyned systems, Fourier Transform Heterodyne (FTH) incorporates transverse spatial encoding of the local oscillator for image capture. Appropriate selection of spatial encoding functions (basis set) allows image retrieval by way of classic

  1. Robust Global Image Registration Based on a Hybrid Algorithm Combining Fourier- and Spatial-domain Techniques

    NASA Astrophysics Data System (ADS)

    Crabtree, P.; McNicholl, P.; Seanor, C.; Murray-Krezan, J.

    2012-09-01

    A variety of image registration techniques have been investigated for applications such as image analysis, fusion, compression, enhancement, and creating mosaics. In particular, robust registration is a key component for successful multi-frame processing aimed at super-resolution or high dynamic range imaging. Image registration techniques are broadly categorized as global (area) or feature-based, and can also be classified as being performed in either the Fourier- or spatial-domain. Spatial domain methods are typically used for applications requiring accurate estimation of sub-pixel motion, such as multi-frame super-resolution based on de-aliasing. However, these techniques often rely on the availability of a priori information (good initial guess), and are therefore limited in terms of the dynamic range of the global motion estimates. A Gaussian pyramid approach is one standard method for extending the region of convergence of spatial domain techniques. On the other hand, Fourier domain-based correlation techniques such as the log-polar FFT method provide fast and reasonably accurate estimates of global shifts, rotation, and uniform scale changes, and tend to perform well over a large range of frame-to-frame motion magnitudes. In this paper we explore several possible hybrid algorithms for robust global registration based on combining the log-polar FFT and spatial-domain techniques. This includes the straightforward use of the log-polar FFT algorithm to generate an initial guess for use by a spatial domain algorithm, as well as the intertwining of the two methods by applying both global correlation and spatial domain registration at each relevant step within the log-polar FFT algorithm. In addition, we explore the benefits of normalized gradient correlation in performing the coarse log-polar FFT registration. The use of normalized gradient correlation, as opposed to phase-only correlation, has recently been proposed for improving the log-polar FFT method in terms of robustness and dynamic range of the uniform scale estimates. The results presented here are based on image sequences captured in the laboratory using a CMOS machine vision camera.

  2. Phase retrieval using coherent imaging systems with linear transfer functions

    Microsoft Academic Search

    David Paganin; Timur E. Gureyev; Konstantin M. Pavlov; Robert A. Lewis; Marcus Kitchen

    2004-01-01

    We consider the problem of quantitative phase retrieval from images obtained using a coherent shift-invariant linear imaging system whose associated transfer function (i.e., the Fourier transform of the complex point-spread function) is well approximated by a linear function of spatial frequency. This linear approximation to the transfer function is applicable when the spread of spatial frequencies, in a two-dimensional complex

  3. Fabrication and Testing of Binary-Phase Fourier Gratings for Nonuniform Array Generation

    NASA Technical Reports Server (NTRS)

    Keys, Andrew S.; Crow, Robert W.; Ashley, Paul R.; Nelson, Tom R., Jr.; Parker, Jack H.; Beecher, Elizabeth A.

    2004-01-01

    This effort describes the fabrication and testing of binary-phase Fourier gratings designed to generate an incoherent array of output source points with nonuniform user-defined intensities, symmetric about the zeroth order. Like Dammann fanout gratings, these binary-phase Fourier gratings employ only two phase levels to generate a defined output array. Unlike Dammann fanout gratings, these gratings generate an array of nonuniform, user-defined intensities when projected into the far-field regime. The paper describes the process of design, fabrication, and testing for two different version of the binary-phase grating; one designed for a 12 micron wavelength, referred to as the Long-Wavelength Infrared (LWIR) grating, and one designed for a 5 micron wavelength, referred to as the Mid-Wavelength Infrared Grating (MWIR).

  4. Improvement of quality of optical reconstruction of digital Fourier holograms displayed on phase-only SLM by its digital preprocessing

    NASA Astrophysics Data System (ADS)

    Cheremkhin, Pavel A.; Evtikhiev, Nikolay N.; Krasnov, Vitaly V.; Porshneva, Liudmila A.; Rodin, Vladislav G.; Starikov, Sergey N.

    2014-10-01

    Digital holography is popular tool for research and practical applications in various fields of science and technology. Most widespread method of optical reconstruction implements digital hologram display on spatial light modulators (SLM). Optical reconstruction of digital holograms is used for remote display of static and dynamic 2D and 3D scenes, in optical information processing, metrology, interferometry, microscopy, etc. Holograms recorded with digital cameras are amplitude type. Therefore quality of its optical reconstruction with phase SLM is worse compared to amplitude SLM. However application of phase SLM can provide higher diffraction efficiency. To improve quality of optical reconstruction with phase SLM, method of SLM phase modulation depth reduction at digital hologram display is proposed. To our knowledge, this method was applied only in analog holography. Also two other methods of quality improvement are considered: hologram to kinoform conversion and holograms multiplexing. Numerical experiments on modelling of digital Fourier holograms recording and their optical reconstruction by phase SLM were performed. Method of SLM phase modulation depth reduction at digital holograms display was proposed and tested. SLM phase modulation depth ranged from 0 to 2?. Quantity of hologram phase levels equal to 256 corresponds to 2? phase modulation depth. To keep SLM settings while changing phase modulation depth hologram phase distribution was renormalized instead. Dependencies of reconstruction quality on hologram phase modulation depth were obtained. Best quality is achieved at 0.27?÷0.31? phase modulation depth. To reduce speckle noise, hologram multiplexing can be applied. Modeling of multiplex holograms optical reconstruction was conducted. Speckle noise reduction was achieved. For improvement of digital hologram optical reconstruction quality and diffraction efficiency hologram to kinoform conversion can be used. Firstly numerically reconstructed image of object was obtained. Then this image was used for kinoform synthesis. Diffraction efficiency was increased by 6.4 times in comparison with hologram reconstruction.

  5. Terahertz holography for imaging amplitude and phase objects.

    PubMed

    Hack, Erwin; Zolliker, Peter

    2014-06-30

    A non-monochromatic THz Quantum Cascade Laser and an uncooled micro-bolometer array detector with VGA resolution are used in a beam-splitter free holographic set-up to measure amplitude and phase objects in transmission. Phase maps of the diffraction pattern are retrieved using the Fourier transform carrier fringe method; while a Fresnel-Kirchhoff back propagation algorithm is used to reconstruct the complex object image. A lateral resolution of 280 µm and a relative phase sensitivity of about 0.5 rad are estimated from reconstructed images of a metallic Siemens star and a polypropylene test structure, respectively. Simulations corroborate the experimental results. PMID:24977861

  6. Spectral multiplexing and coherent-state decomposition in Fourier ptychographic imaging

    PubMed Central

    Dong, Siyuan; Shiradkar, Radhika; Nanda, Pariksheet; Zheng, Guoan

    2014-01-01

    Information multiplexing is important for biomedical imaging and chemical sensing. In this paper, we report a microscopy imaging technique, termed state-multiplexed Fourier ptychography (FP), for information multiplexing and coherent-state decomposition. Similar to a typical Fourier ptychographic setting, we use an array of light sources to illuminate the sample from different incident angles and acquire corresponding low-resolution images using a monochromatic camera. In the reported technique, however, multiple light sources are lit up simultaneously for information multiplexing, and the acquired images thus represent incoherent summations of the sample transmission profiles corresponding to different coherent states. We show that, by using the state-multiplexed FP recovery routine, we can decompose the incoherent mixture of the FP acquisitions to recover a high-resolution sample image. We also show that, color-multiplexed imaging can be performed by simultaneously turning on R/G/B LEDs for data acquisition. The reported technique may provide a solution for handling the partially coherent effect of light sources used in Fourier ptychographic imaging platforms. It can also be used to replace spectral filter, gratings or other optical components for spectral multiplexing and demultiplexing. With the availability of cost-effective broadband LEDs, the reported technique may open up exciting opportunities for computational multispectral imaging. PMID:24940538

  7. Phase-imaging holographic microscope

    NASA Astrophysics Data System (ADS)

    Brody, Philip S.; Garvin, Charles G.; Gillman, Arthur W.; Shentu, Lian

    1994-05-01

    A real-time holographic microscope for phase imaging is described. The image-formation process is based on the aberration-correcting capability of phase-conjugate illumination. After it has passed through a phase object, the light from a laser beam is recorded as a reflection hologram within a crystal of barium titanate by the self-pumping process. Such a reflection hologram, when illuminated, returns the phase conjugate of the incident distorted optical field. The object is then displaced slightly, and the phase conjugate of the field produced by the undisplaced object now passes through the displaced object. This produces in the object plane an intensity pattern that is an image of gradients in phase retardation. A microscope (objective and ocular) creates a magnified image of the pattern. A digital processor grabs video frames, subtracting from the gradient image the initial optical field acquired before the shift. The subtractive processing results in a final image free of coherent noise and artifacts. We describe the microscope and its operation and show representative images.

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

    E-print Network

    Jalali. Bahram

    Amplified dispersive Fourier-transform imaging for ultrafast displacement sensing and barcode and, more importantly, enables fast real-time measurements. Here we describe a novel ultrafast barcode. This technique amplifies and simultaneously maps the spectrally encoded barcode into a temporal waveform

  9. 3D imaging of dental hard tissues with Fourier domain optical coherence tomography

    Microsoft Academic Search

    Yueli L. Chen; Yi Yang; Jing Ma; Jun Yan; Yuanxin Shou; Tianheng Wang; Aruna Ramesh; Jing Zhao; Quing Zhu

    2011-01-01

    A fiber optical coherence tomography (OCT) probe is used for three dimensional dental imaging. The probe has a lightweight miniaturized design with a size of a pen to facilitate clinic in vivo diagnostics. The probe is interfaced with a swept-source \\/ Fourier domain optical coherence tomography at 20K axial scanning rate. The tooth samples were scanned from occlusal, buccal, lingual,

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

    Microsoft Academic Search

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

    1997-01-01

    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

  11. Complex Acquisition of the Fourier Transform Imaging of an Arbitrary Object

    E-print Network

    Minghui Zhang; Jianfei Xu; Xianfu Wang

    2009-05-13

    A scheme to a complex-valued acquisition of the Fourier transform imaging was proposed. The main idea is to project the real and the imaginary parts of a diffraction field to intensity distributions respectively. The whole procedure was algorithm independent and needs no a priori knowledge of an arbitrary objet. An example was demonstrated with a numerical modeling and its results.

  12. Gaseous effluent monitoring and identification using an imaging Fourier transform spectrometer

    SciTech Connect

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

    1993-10-01

    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.

  13. Optical coherence tomography for imaging of subpleural alveolar structure using a Fourier domain mode locked laser

    NASA Astrophysics Data System (ADS)

    Kirsten, Lars; Walther, Julia; Cimalla, Peter; Gaertner, Maria; Meissner, Sven; Koch, Edmund

    2011-06-01

    Optical coherence tomography (OCT) is a noninvasive imaging modality generating cross sectional and volumetric images of translucent samples. In Fourier domain OCT (FD OCT), the depth profile is calculated by a fast Fourier transformation of the interference spectrum, providing speed and SNR advantage and thus making FD OCT well suitable in biomedical applications. The interference spectrum can be acquired spectrally resolved in spectral domain OCT or time-resolved in optical frequency domain imaging (OFDI). Since OCT images still suffer from motion artifacts, especially under in vivo conditions, increased depth scan rates are required. Therefor, the principle of Fourier domain mode locking has been presented by R. Huber et al. circumventing the speed limitations of conventional FD OCT systems. In FDML lasers, a long single mode fiber is inserted in the ring resonator of the laser resulting in an optical round trip time of a few microseconds. Sweeping the wavelength synchronously by a tunable Fabry-Perot filter can provide wavelength sweeps with repetition rates up to a few MHz used for OFDI. Imaging of subpleural lung tissue for investigation of lung dynamics and its elastic properties is a further biomedical application demanding high-speed OCT imaging techniques. For the first time, the visualization of subpleural alveolar structures of a rabbit lung is presented by the use of an FDML-based OCT system enabling repetition rates of 49.5 kHz and 122.6 kHz, respectively.

  14. Sub-wavelength Coherent Imaging of a Pure-Phase Object with Thermal Light

    E-print Network

    Minghui Zhang; Qing Wei; Xia Shen; Yongfeng Liu; Honglin Liu; Yanfeng Bai; Shensheng Han

    2006-12-19

    We report, for the first time, the observation of sub-wavelength coherent image of a pure phase object with thermal light,which represents an accurate Fourier transform. We demonstrate that ghost-imaging scheme (GI) retrieves amplitude transmittance knowledge of objects rather than the transmitted intensities as the HBT-type imaging scheme does.

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

    SciTech Connect

    Saggin, Bortolino; Scaccabarozzi, Diego; Tarabini, Marco

    2011-04-20

    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.

  16. Characterizing and tracking individual colloidal particles using Fourier-Bessel image decomposition.

    PubMed

    Strubbe, Filip; Vandewiele, Stijn; Schreuer, Caspar; Beunis, Filip; Drobchak, Oksana; Brans, Toon; Neyts, Kristiaan

    2014-10-01

    We use Fourier-Bessel Image Decomposition (FBID) of microscopy images to investigate the size, refractive index and 3-dimensional position of individual colloidal microspheres. With measurements of monodisperse polystyrene and poly(methyl methacrylate) particles we achieve a resolution of 1% in size and 0.2% in refractive index for a single image which is sufficient for accurate in situ characterization of polydisperse colloids. Also the binding of avidin molecules to individual biotinylated polystyrene particles is resolved. Finally, the FBID method offers a straightforward approach to 3-dimensional out-of-focus tracking. Here, the z-position of a freely diffusing particle is calculated by applying the statistics of Brownian motion to its set of Fourier-Bessel coefficients. PMID:25322038

  17. Determination of doubly labeled water by gas-phase Fourier transform infrared spectroscopy.

    PubMed

    Khaled, M A; Krumdieck, C L; Ong, J L

    1995-01-01

    Both 2H (deuterium) and 18O (oxygen 18) in isotopically enriched water have been detected by gas-phase Fourier transform infrared (FTIR) spectroscopy at 2,720 and 3,661.8 cm-1, respectively. A linear relationship between varying concentrations of each of these isotopes and their absorbance at the above frequencies indicates that gas-phase FTIR may provide a rapid and potentially less expensive approach to measure doubly labeled water in biological fluids for the estimation of energy expenditure and total body water. PMID:7854152

  18. PHASE CORRELATION METHOD FOR THE ALIGNMENT OF TOTAL SOLAR ECLIPSE IMAGES

    SciTech Connect

    Druckmueller, M., E-mail: druckmuller@fme.vutbr.c [Institute of Mathematics, Faculty of Mechanical Engineering, Brno University of Technology, 616 69 Brno (Czech Republic)

    2009-12-01

    A modified phase correlation method, based on Fourier transform, which enables the alignment of solar coronal images taken during the total solar eclipses, is presented. The method enables the measurement of translation, rotation, and scaling factor between two images. With the application of this technique, pairs of images with different exposure times, different brightness scale, such as linear for CCD and nonlinear for images taken with photographic film, and even images from different emission lines can be aligned with sub-pixel precision.

  19. A Panchromatic Imaging Fourier Transform Spectrometer for the NASA Geostationary Coastal and Air Pollution Events Mission

    Microsoft Academic Search

    Yen-Hung Wu; Richard Key; Stanley Sander; Jean-Francois Blavier; David Rider

    2011-01-01

    This paper summarizes the design and development of the Panchromatic Imaging Fourier Transform Spectrometer (PanFTS) for the NASA Geostationary Coastal and Air Pollution Events (GEO-CAPE) Mission. The PanFTS instrument will advance the understanding of the global climate and atmospheric chemistry by measuring spectrally resolved outgoing thermal and reflected solar radiation. With continuous spectral coverage from the near-ultraviolet through the thermal

  20. Color image encryption based on fractional Fourier transforms and pixel scrambling technique

    NASA Astrophysics Data System (ADS)

    Zhao, Jianlin; Lu, Hongqiang; Fan, Qi

    2007-01-01

    Color image encryption based on fractional Fourier transform (FRT) and pixel scrambling technique is presented in this paper. In general, color (RGB) image cannot be directly encrypted using a traditional setup for optical information processing, because which is only adapted to process two-dimensional gray image. In the proposed method, a three-dimensional RGB image is decomposed to three two-dimensional gray images (R, G and B values of the color image), and the encryption operation will be done on each two-dimensional gray image, then the encoded color image is available by composing the three two-dimensional encrypted images. The decryption process is an inverse of the encryption. The optical encrypting systems based on the presented method is proposed and simulated. Some results of computer simulation are presented to verify the flexibility and the reliability of this method. The quality of decrypted images would be debased with the difference of the fractional order. The frustrated decryption of monochromic image will affect the color of decrypted image. At the end of this paper, an all-optical and photoelectric encryption/decryption systems solution are presented, and the principle of selecting optical devices are also given.

  1. Depth resolved hyperspectral imaging spectrometer based on structured light illumination and Fourier transform interferometry

    PubMed Central

    Choi, Heejin; Wadduwage, Dushan; Matsudaira, Paul T.; So, Peter T.C.

    2014-01-01

    A depth resolved hyperspectral imaging spectrometer can provide depth resolved imaging both in the spatial and the spectral domain. Images acquired through a standard imaging Fourier transform spectrometer do not have the depth-resolution. By post processing the spectral cubes (x, y, ?) obtained through a Sagnac interferometer under uniform illumination and structured illumination, spectrally resolved images with depth resolution can be recovered using structured light illumination algorithms such as the HiLo method. The proposed scheme is validated with in vitro specimens including fluorescent solution and fluorescent beads with known spectra. The system is further demonstrated in quantifying spectra from 3D resolved features in biological specimens. The system has demonstrated depth resolution of 1.8 ?m and spectral resolution of 7 nm respectively. PMID:25360367

  2. Variable-retardance, Fourier-transform imaging spectropolarimeters for visible spectrum remote sensing.

    PubMed

    Tyo, J S; Turner, T S

    2001-03-20

    An imaging, variable-retardance, Fourier-transform spectropolarimeter is presented that is capable of creating spectropolarimetric images of scenes with independent characterization of spatial, spectral, and polarimetric information. The device has a spectral resolution of approximately 225 cm(-1), making it truly hyperspectral in nature. Images of canonical targets such as spheres and cylinders obtained in a laboratory setup are presented. The results demonstrate the capability of developing systems to collect spectropolarimetric data of field images by use of the concept of pushbroom scanning and serial collection of polarimetric information. Further development of a parallelized collection strategy would allow the collection of near-real-time images of real-world targets. PMID:18357136

  3. Perfusion and ventilation filters for Fourier-decomposition MR lung imaging.

    PubMed

    Wujcicki, Artur; Corteville, Dominique; Materka, Andrzej; Schad, Lothar R

    2015-03-01

    MR imaging without the use of contrast agents has recently been used for creating perfusion and ventilation functional lung images. The technique incorporates frequency- or wavelet-domain filters to separate the MR signal components. This paper presents a new, subject-adaptive algorithm for perfusion and ventilation filters design. The proposed algorithm uses a lung signal model for separation of the signal components in the frequency domain. Non-stationary lung signals are handled by a short time Fourier transform. This method was applied to sets of 192 and 90 co-registered non-contrast MR lung images measured for five healthy subjects at the rate of 3,33 images per second, using different slice thicknesses. In each case, the resulted perfusion and ventilation images showed a smaller amount of mutual information, when compared to those obtained using the known lowpass/highpass filter approach. PMID:25466452

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

    DOEpatents

    Olivier, Scot S. (Livermore, CA); Werner, John S. (Davis, CA); Zawadzki, Robert J. (Sacramento, CA); Laut, Sophie P. (Pasedena, CA); Jones, Steven M. (Livermore, CA)

    2010-09-07

    This invention permits retinal images to be acquired at high speed and with unprecedented resolution in three dimensions (4.times.4.times.6 .mu.m). The instrument achieves high lateral resolution by using adaptive optics to correct optical aberrations of the human eye in real time. High axial resolution and high speed are made possible by the use of Fourier-domain optical coherence tomography. Using this system, we have demonstrated the ability to image microscopic blood vessels and the cone photoreceptor mosaic.

  5. Imaging Fourier transform spectroscopy of the boundary layer plume from laser irradiated polymers and carbon materials

    NASA Astrophysics Data System (ADS)

    Acosta, Roberto I.

    The high-energy laser (HEL) lethality community needs for enhanced laser weapons systems requires a better understanding of a wide variety of emerging threats. In order to reduce the dimensionality of laser-materials interaction it is necessary to develop novel predictive capabilities of these events. The objective is to better understand the fundamentals of laser lethality testing by developing empirical models from hyperspectral imagery, enabling a robust library of experiments for vulnerability assessments. Emissive plumes from laser irradiated fiberglass reinforced polymers (FRP), poly(methyl methacrylate) (PMMA) and porous graphite targets were investigated primarily using a mid-wave infrared (MWIR) imaging Fourier transform spectrometer (FTS). Polymer and graphite targets were irradiated with a continuous wave (cw) fiber lasers. Data was acquired with a spectral resolution of 2 cm-1 and spatial resolution as high as 0.52 mm2 per pixel. Strong emission from H2O, CO, CO2 and hydrocarbons were observed in the MWIR between 1900-4000 cm-1. A single-layer radiative transfer model was developed to estimate spatial maps of temperature and column densities of CO and CO2 from the hyperspectral imagery of the boundary layer plume. The spectral model was used to compute the absorption cross sections of CO and CO2, using spectral line parameters from the high temperature extension of the HITRAN. Also, spatial maps of gas-phase temperature and methyl methacrylate (MMA) concentration were developed from laser irradiated carbon black-pigmented PMMA at irradiances of 4-22 W/cm2. Global kinetics interplay between heterogeneous and homogeneous combustion kinetics are shown from experimental observations at high spatial resolutions. Overall the boundary layer profile at steady-state is consistent with CO being mainly produced at the surface by heterogeneous reactions followed by a rapid homogeneous combustion in the boundary layer towards buoyancy.

  6. Fourier-phase analysis of the orbiting bright-spot model for AGN variability

    E-print Network

    V. Karas

    1997-01-13

    Fourier power spectra and phases of a signal from a large number of radiating sources orbiting around a black hole are investigated. It is assumed that the individual sources (bright spots) are located in an accretion disc and their lifetime exceeds the corresponding orbital period. This model is relevant for the short-time X-ray variability of active galactic nuclei. Previous works on this subject were mostly concentrated on temporal characteristics and power spectra of observed light curves. In our present contribution, Fourier phases are brought into consideration and studied systematically for a broad range of input parameters. In particular, conditions for the phase coherence are discussed. It is shown that one can discriminate between the two classes of models which are currently under consideration--orbital motion of a large number of sources versus short-lived independent flares--although parameters of the model are not completely arbitrary. It is also shown that predicted power spectra depend rather strongly on the spot distribution across the disk surface. We conclude that the orbital motion of the spots cannot be the only reason for the source fluctuations, but it certainly influences observational properties of the source intrinsic variability.

  7. Universal and special keys based on phase-truncated Fourier transform.

    PubMed

    Qin, Wan; Peng, Xiang; Meng, Xiangfeng; Gao, Bruce

    2011-08-01

    We propose a novel optical asymmetric cryptosystem based on a phase-truncated Fourier transform. Two decryption keys independent of each other are generated. They are referred to as universal key and special key, respectively. Each of them can be used for decryption independently in absence of the other. The universal key is applicable to decrypt any ciphertext encoded by the same encryption key, but with poor legibility. On the contrary, the special key is adequate for legible decryption, but only valid for one ciphertext corresponding to the specified plaintext. A set of simulation results show the interesting performance of two types of de cryption keys. PMID:25339784

  8. Ultrasonic imaging of an object at the presence of Fourier and non-Fourier transformation in the transmitted through the object acoustic field.

    PubMed

    Andreeva, A; Burova, M; Burov, J

    2007-06-01

    A metal object is computer visualized by registration of the amplitudes of the transmitted through the object short acoustic pulses. The pulses are separated by time, because of the presence of holes and internal compact components in the longitudinal section (structure along the propagation direction of acoustic wave). The acoustic field transmitted through the object is composited from a field presenting Fourier transformation of the hole shape and field, transmitted through the metal components in the longitudinal section of the object. A computer Fourier transformation of the digital data of the amplitude fields transmitted through the object components is performed instead of converging lens. The Fourier series of the object obtained as digital data after the transformation is multiplied with a term, describing the angle distribution of the field on spatial frequencies. The reconstruction of the image of the metal components is performed by reverse transformation, i.e. summing up in all spatial frequencies. 3D visualization of the transmitted through the hole acoustic field determines the hole geometry (circular, square, rectangular). It is shown that at the transmission of a short acoustic pulse through the components with different thicknesses and holes, presenting Fourier and non-Fourier transformation can be registered separately in contrast to the optics. PMID:17395232

  9. Field experiment performance of the receiver elements for a Fourier telescopy imaging system

    NASA Astrophysics Data System (ADS)

    Mathis, J.; Stapp, J.; Cuellar, E. L.; Cooper, J.; Morris, A.; Fairchild, P.; Hult, Dane; Koski, Katrina; Ramzel, Lee; Thornton, Marcia A.

    2005-08-01

    Fourier telescopy (FT) is an active imaging technique that is a candidate for high resolution imaging systems which can be used to obtain satellite images out to geosynchronous target ranges. Fourier telescopy uses multiple beams that illuminate the target with a fringe pattern that sweeps across it due to a set frequency difference between beams. In this way the target spatial frequency components are encoded in the temporal signal that is reflected from the target. The FT receiver can then be composed of a large area "light bucket" collector, since only the integrated temporal signal is necessary to reconstruct the target image. The GEO Light Imaging National Testbed (GLINT) system was previously designed to obtain satellite images at geosynchronous ranges by using this technique. The "light bucket" receiver was designed use forty heliostats, each having a collection area of ten meters square, and composed of a 16 x 16 grid of two foot square mirrors. The heliostats would redirect the return light from the target onto a large spherical concentrator array composed of hexagonal mirror segments. This concentrator would then focus the return light onto a photomultiplier tube (PMT) detector. The FT Field experiment presented in this paper uses one 10-meter square heliostat and a single PMT, plus a scaled down secondary array to provide the optical elements of the receiver for the FT field experiment. In this paper, we will describe the performance characteristics of the heliostat, secondary, and PMT detector. Performance characteristics include optical wavefront, alignment, and alignment stability of the optical elements. Finally, results will be presented after the receiver was integrated with a transmitter system that provided the modulated FT signal from various targets. Image reconstructions will show that even using low quality "Light bucket" receiver optics and a 1.5 km horizontal path through the atmosphere, the modulated signal can still produce good image quality of the targets. Image reconstruction will also be presented for different SNR values in the received signal.

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

    PubMed

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

    2013-02-01

    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. PMID:23412778

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

    PubMed Central

    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

    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. PMID:23412778

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

    PubMed Central

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

    2012-01-01

    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. PMID:22559689

  13. MightySat II.1 Fourier-transform hyperspectral imager payload performance

    NASA Astrophysics Data System (ADS)

    Otten, Leonard J.; Sellar, R. Glenn; Rafert, J. Bruce

    1995-12-01

    Using a new microsat called MightySat II as a platform, Kestrel Corporation is designing and building the first Fourier transform hyperspectral imager (FTHSI) to be operated from a spacecraft. This payload will also be the first to fly on the Phillips Laboratory MightySat II spacecraft series, a new, innovative approach, to affordable space testing of high risk, high payoff technologies. Performance enhancements offered by the Fourier transform approach have shown it to be one of the more promising spaceborne hyperspectral concepts. Simulations of the payload's performance have shown that the instrument is capable of separating a wide range of subtle spectral differences. Variations in the return from the Georges Bank and shoals are discernible and various types of coastal grasses (sea oats and spartina) can be isolated against a sand background.

  14. Subwavelength Fourier-transform imaging without a lens or a beamsplitter

    NASA Astrophysics Data System (ADS)

    Liu, Rui-Feng; Yuan, Xin-Xing; Fang, Yi-Zhen; Zhang, Pei; Zhou, Yu; Gao, Hong; Li, Fu-Li

    2014-05-01

    The fourier-transform patterns of an object are usually observed in the far-field region or obtained in the near-field region with the help of lenses. Here we propose and experimentally demonstrate a scheme of Fourier-transform patterns in the Fresnel diffraction region with thermal light. In this scheme, neither a lens nor a beamsplitter is used, and only one single charge coupled device (CCD) is employed. It means that dividing one beam out of a light source into signal and reference beams is not as necessary as the one done by the use of a beamsplitter in usual ghost interference experiments. Moreover, the coincidence measurement of two point detectors is not necessary and data recorded on a single CCD are sufficient for reconstructing the ghost diffraction patterns. The feature of the scheme promises a great potential application in the fields of X-ray and neutron diffraction imaging processes.

  15. Phase unwrapping for 2-D blind deconvolution of ultrasound images.

    PubMed

    Michailovich, Oleg; Adam, Dan

    2004-01-01

    In most approaches to the problem of two-dimensional homomorphic deconvolution of ultrasound images, the estimation of a corresponding point-spread function (PSF) is necessarily the first stage in the process of image restoration. This estimation is usually performed in the Fourier domain by either successive or simultaneous estimation of the amplitude and phase of the Fourier transform (FT) of the PSE This paper addresses the problem of recovering the FT-phase of the PSF, which is an important reconstruction problem by itself. The purpose of this paper is twofold. First, it provides a theoretical framework, establishing that the FT-phase of the PSF can be effectively estimated by a proper smoothing of the FT-phase of the appropriate radio-frequency (RF) image. Second, it presents a novel approach to the estimation of the FT-phase of the PSF, by solving a continuous Poisson equation over a predefined smooth subspace, in contrast to the discrete Poisson equation solver used for the classical least mean squares phase unwrapping algorithms, followed by a smoothing procedure. The proposed approach is possible due to the distinct properties of the FT-phases, among which the most important property is the availability of precise values of their partial derivatives. This property overcomes the main disadvantage of the discrete schemes, which routinely use wrapped (principal) values of the phase in order to approximate its partial derivatives. Since such an approximation is feasible subject to the restriction that the partial phase differences do not exceed pi in absolute value, the discrete schemes perform satisfactory only for few practical situations. The proposed approach is shown to be independent of this restriction and, thus, it performs for a wider class of the phases with significantly lower errors. The main advantages of the novel method over the algorithms based on discrete schemes are demonstrated in a series of computer simulations and for in vivo measurements. PMID:14719683

  16. Fourier domain mode locked (FDML) lasers at 1050 nm and 202,000 sweeps per second for OCT retinal imaging

    Microsoft Academic Search

    Robert A. Huber; Desmond C. Adler; Vivek J. Srinivasan; Iwona M. Gorczynska; James G. Fujimoto

    2007-01-01

    Retinal imaging ranks amongst the most important clinical applications for optical coherence tomography (OCT) [1, 2]. The recent demonstration of increased sensitivity [3-6] in Fourier Domain detection [7, 8] has opened the way for dramatically higher imaging speeds, up to axial scan rates of several tens of kilohertz. However, these imaging speeds are still not sufficient for high density 3D

  17. The New Physical Optics Notebook: Tutorials in Fourier Optics.

    ERIC Educational Resources Information Center

    Reynolds, George O.; And Others

    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

  18. Phase difference map interpretation of Mach diamond interferometric patterns by Fourier Transform Methods

    NASA Astrophysics Data System (ADS)

    Rodríguez, F.; Dorrío, B. V.; Doval, A. F.

    2008-04-01

    The development of a new interferometric evaluation system has allowed the detailed quantitative characterization of complex Mach diamond patterns in quasi stationary jets of compressed air provided by a Laval nozzle usually employed for laser cutting of ceramic materials. The application of a Mach-Zehnder interferometer in order to observe the stationary shock wave patterns provides fringe patterns that are recorded through a CMOS camera. Their optical phase is extracted through two differential phase evaluation methods that use the Fourier Transform as a fundamental tool. On the basis of the available data, the analysis of the pressure distribution and also of the shock wave patterns that occur in the free jet stream allows us to confirm the hypothesis previously established related with the main characteristics of a free jet.

  19. Higher-dimensional phase imaging

    NASA Astrophysics Data System (ADS)

    Huntley, Jonathan M.

    2010-04-01

    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.

  20. 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)

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

    2012-03-01

    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).

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

    NASA Astrophysics Data System (ADS)

    Cornelio, Anastasia; Bonettini, Silvia; Prato, Marco

    2013-10-01

    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.

  2. Analysis of the Advantages and Limitations of Stationary Imaging Fourier Transform Spectrometer. Revised

    NASA Technical Reports Server (NTRS)

    Beecken, Brian P.; Kleinman, Randall R.

    2004-01-01

    New developments in infrared sensor technology have potentially made possible a new space-based system which can measure far-infrared radiation at lower costs (mass, power and expense). The Stationary Imaging Fourier Transform Spectrometer (SIFTS) proposed by NASA Langley Research Center, makes use of new detector array technology. A mathematical model which simulates resolution and spectral range relationships has been developed for analyzing the utility of such a radically new approach to spectroscopy. Calculations with this forward model emulate the effects of a detector array on the ability to retrieve accurate spectral features. Initial computations indicate significant attenuation at high wavenumbers.

  3. Analysis of stacking faults in gallium nitride by Fourier transform of high-resolution images

    NASA Astrophysics Data System (ADS)

    Kirilenko, D. A.; Sitnikova, A. A.; Kremleva, A. V.; Mynbaeva, M. G.; Nikolaev, V. I.

    2014-12-01

    We present results of studying stacking faults (SFs) in gallium nitride (GaN) with the aid of Fourier transform of high-resolution transmission electron microscopy (HRTEM) images. Using this method, it is possible both to determine the SF type and to directly measure the corresponding displacement vector. This allowed us to explain the peculiarities of the contrast of HRTEM of structures with high SF density (above 106 cm-1). It is established that the displacement vector component in the (0001) plane in these structures can significantly differ from the expected value of that is typical of single SFs.

  4. Fourier transform spectroscopic imaging using an infrared focal-plane array detector.

    PubMed

    Lewis, E N; Treado, P J; Reeder, R C; Story, G M; Dowrey, A E; Marcott, C; Levin, I W

    1995-10-01

    A powerful new mid-infrared spectroscopic chemical imaging technique combining step-scan Fourier transform Michelson interferometry with indium antimonide focal-plane array (FPA) image detection is described. The coupling of an infrared focal-plane array detector to an interferometer provides an instrumental multiplex/multichannel advantage. Specifically, the multiple detector elements enable spectra at all pixels to be collected simultaneously, while the interferometer portion of the system allows all the spectral frequencies to be measured concurrently. With this method of mid-infrared spectroscopic imaging, the fidelity of the generated spectral images is limited only by the number of pixels on the FPA detector, and only several seconds of starting time is required for spectral image acquisition. This novel, high-definition technique represents the future of infrared chemical imaging analysis, a new discipline within the chemical and material sciences, which combines the capability of spectroscopy for molecular analysis with the power of visualization. In particular, chemical imaging is broadly applicable for noninvasive, molecular characterization of heterogeneous materials, since all solid-state materials exhibit chemical nonuniformity that exists either by design or by development during the course of material preparation or fabrication. Imaging, employing Raman and infrared spectroscopy, allows the precise characterization of the chemical composition, domain structure, and chemical architecture of a variety of substances. This information is often crucial to a wide range of activities, extending from the fabrication of new materials to a basic understanding of biological samples. In this study, step-scan imaging principles, instrument design details, and infrared chemical imaging results are presented. Since the prospect of performing high-resolution and high-definition mid-infrared chemical imaging very rapidly has been achieved with the step-scan approach, the implications for the chemical analysis of materials are many and varied. PMID:8686889

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

    NASA Astrophysics Data System (ADS)

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

    2013-03-01

    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.

  6. Fourier Monte Carlo simulation of crystalline membranes in the flat phase

    NASA Astrophysics Data System (ADS)

    Tröster, Andreas

    2013-08-01

    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.

  7. Transition to the Fulde-Ferrel-Larkin-Ovchinnikov planar phase: A quasiclassical investigation with Fourier expansion

    NASA Astrophysics Data System (ADS)

    Combescot, R.; Mora, C.

    2005-04-01

    We explore, in three spatial dimensions, the transition from the normal state to the Fulde-Ferrel-Larkin-Ovchinnikov superfluid phases. We restrict ourselves to the case of the “planar” phase, where the order parameter depends only on a single spatial coordinate. We first show that, in the case of the simple Fulde-Ferrell phase, singularities occur at zero temperature in the free energy which prevents, at low temperature, a reliable use of an expansion in powers of the order parameter. We then introduce in the quasiclassical equations a Fourier expansion for the order parameter and the Green’s functions, and we show that it converges quite rapidly to the exact solution. We finally implement numerically this method and find results in excellent agreement with the earlier work of Matsuo In particular, when the temperature is lowered from the tricritical point, the transition switches from first to second order. In the case of the first-order transition, the spatial dependence of the order parameter at the transition is found to be always very nearly a pure cosine, although the maximum of its modulus may be comparable to the one of the uniform BCS phase.

  8. Slit Function Measurement of An Imaging Spectrograph Using Fourier Transform Techniques

    NASA Technical Reports Server (NTRS)

    Park, Hongwoo; Swimyard, Bruce; Jakobsen, Peter; Moseley, Harvey; Greenhouse, Matthew

    2004-01-01

    Knowledge of a spectrograph slit function is necessary to interpret the unresolved lines in an observed spectrum. A theoretical slit function can be calculated from the sizes of the entrance slit, the detector aperture when it functions as an exit slit, the dispersion characteristic of the disperser, and the point spread function of the spectrograph. A measured slit function is preferred to the theoretical one for the correct interpretation of the spectral data. In a scanning spectrometer with a single exit slit, the slit function is easily measured. In a fixed grating/or disperser spectrograph, illuminating the entrance slit with a near monochromatic light from a pre-monochrmator or a tunable laser and varying the wavelength of the incident light can measure the slit function. Even though the latter technique had been used successfully for the slit function measurements, it had been very laborious and it would be prohibitive to an imaging spectrograph or a multi-object spectrograph that has a large field of view. We explore an alternative technique that is manageable for the measurements. In the proposed technique, the imaging spectrograph is used as a detector of a Fourier transform spectrometer. This method can be applied not only to an IR spectrograph but also has a potential to a visible/UV spectrograph including a wedge filter spectrograph. This technique will require a blackbody source of known temperature and a bolometer to characterize the interferometer part of the Fourier Transform spectrometer. This pa?er will describe the alternative slit function measurement technique using a Fourier transform spectrometer.

  9. Hybrid-dual-fourier tomographic algorithm for a fast three-dimensionial optical image reconstruction in turbid media

    NASA Technical Reports Server (NTRS)

    Alfano, Robert R. (Inventor); Cai, Wei (Inventor)

    2007-01-01

    A reconstruction technique for reducing computation burden in the 3D image processes, wherein the reconstruction procedure comprises an inverse and a forward model. The inverse model uses a hybrid dual Fourier algorithm that combines a 2D Fourier inversion with a 1D matrix inversion to thereby provide high-speed inverse computations. The inverse algorithm uses a hybrid transfer to provide fast Fourier inversion for data of multiple sources and multiple detectors. The forward model is based on an analytical cumulant solution of a radiative transfer equation. The accurate analytical form of the solution to the radiative transfer equation provides an efficient formalism for fast computation of the forward model.

  10. Design of an airborne Fourier transform visible hyperspectral imaging system for light aircraft environmental remote sensing

    NASA Astrophysics Data System (ADS)

    Otten, Leonard John, III; Butler, Eugene W.; Rafert, Bruce; Sellar, R. Glenn

    1995-06-01

    Kestrel Corporation and the Florida Institute of Technology have designed, and are now manufacturing, a Fourier transform visible hyperspectral imager system for use in a single engine light aircraft. The system is composed of a Sagnac-based interferometer optical subsystem, a data management system, and an aircraft attitude and current position sybsystem. The system is designed to have better than 5 nm spectral resolution at 450 nm, operates over the 440 nm to 1150 nm spectral band and has a 2D spatial resolution of 0.8 mrad. An internal calibration source is recorded with every frame of data to retain radiometric accuracy. The entire system fits into a Cessna 206 and uses a conventional downward looking view port located in the baggage compartment. During operation, data are collected at a rate of 15 Mbytes per second and stored direct to a disk array. Data storage has been sized to accommodate 56 minutes of observations. Designed for environmental mapping, this Fourier transform imager has uses in emergency response and military operations.

  11. Measurement of the mid-infrared Fourier spectroscopic imaging of whole human face by portable apparatus (size: 50*50 mm, weight: 200 g)

    NASA Astrophysics Data System (ADS)

    Qi, Wei; Suzuki, Yo; Fujiwara, Masaru; Saito, Tsubasa; Suzuki, Satoru; Abeygunawardhana, Pradeep K.; Wada, Kenji; Nishiyama, Akira; Ishimaru, Ichiro

    2014-11-01

    In the daily living space, measurement of the biological-substance distributions such as sebum can be realized by the proposed method of imaging-type 2-dimensional Fourier spectroscopy. This method has the strong robustness for mechanical vibrations. So, the spectrometer (size: 50*50mm, weight: 200g) can be produced without anti-vibration mechanism. Moreover, the phase shifter is a core part of the spectrometer, and it is constructed by the low-price bimorph type actuator which is depending on the vibration control of the piezoceramic in proposed method. It is appropriate as the actuator of the phase shifter from the evaluation results of the actuator straightness and position accuracy in the midinfrared region. As we know, the Fourier spectroscopy has a high light utilization efficiency. Therefore, the low price microbolometer can be used as the imaging sensor. So, the low-price (10,000 U.S. dollars), compact and high portability spectrometer can be produced. Furthermore, the much higher position accuracy in the short wavelength region is requested as we know, the phase shift correction method has been proposed. In this paper, high performance evaluations of the portable spectroscopy apparatus have been discussed by using the CO2 laser spectroscopy results in the midinfrared region. Then, the phase shift correction method was explained. At the end, we demonstrated the feasibility of the mid-infrared imaging of whole human faces without active illuminations.

  12. 4D imaging of embryonic chick hearts by streak-mode Fourier domain optical coherence tomography

    NASA Astrophysics Data System (ADS)

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

    2012-02-01

    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.

  13. Modeling the viscoplastic micromechanical response of two-phase materials using fast Fourier transforms

    SciTech Connect

    Lebensohn, Ricardo A [Los Alamos National Laboratory; Lee, Sukbin [CMU; Rollett, Anthony D [CMU

    2009-01-01

    A viscoplastic approach using the Fast Fourier Transform (FFT) method for obtaining local mechanical response is utilized to study microstructure-property relationships in composite materials. Specifically, three-dimensional, two-phase digital materials containing isotropically coarsened particles surrounded by a matrix phase, generated through a Kinetic Monte Carlo Potts model for Ostwald ripening, are used as instantiations in order to calculate the stress and strain rate fields under uniaxial tension. The effects of the morphology of the matrix phase, the volume fraction and the contiguity of particles, and the polycrystallinity of matrix phase, on the stress and strain rate fields under uniaxial tension are examined. It is found that the first moments of the stress and strain rate fields have a different dependence on the particle volume fraction and the particle contiguity from their second moments. The average stresses and average strain rates of both phases and of the overall composite have rather simple relationships with the particle volume fraction whereas their standard deviations vary strongly, especially when the particle volume fraction is high, and the contiguity of particles has a noticeable effect on the mechanical response. It is also found that the shape of stress distribution in the BCC hard particle phase evolves as the volume fraction of particles in the composite varies, such that it agrees with the stress field in the BCC polycrystal as the volume of particles approaches unity. Finally, it is observed that the stress and strain rate fields in the microstructures with a polycrystalline matrix are less sensitive to changes in volume fraction and contiguity of particles.

  14. Images of optical periodic elements in the fractional Fourier transform domain

    NASA Astrophysics Data System (ADS)

    Shovgenyuk, Mykhailo V.; Kozlovskii, Yura M.

    2005-09-01

    The theory of periodic phase elements images forming is described based on the method of the coordinate-frequency distribution. The invariant conditions of periodic elements self-images forming which are determined by the ratio of the Fresnel number F0 to tan(p?/2) (where p is the FrFT parameter) are investigated in the FrFT domain. The analytic expressions for the calculation of periodic phase elements at different values of the invariant parameter F0/ tan ? are obtained. It is shown that the FrFT self-image of elementary cell forms as a result of the finite number of the cross displaced elementary cells superposition. The results of numerical calculations of the periodic phase elements self-images in the FrFT domain are presented. The mechanism of constant intensity levels forming depending on the value of invariant parameter is explained.

  15. Discrimination of paper-based kraft tapes using Fourier transform of transmitted light images.

    PubMed

    Sasaoka, Sara; Saito, Koichi; Higashi, Kenjirou; Limwikrant, Waree; Moribe, Kunikazu; Suzuki, Shinichi; Yamamoto, Keiji

    2012-07-10

    This study focused on two-dimensional fast Fourier transform (2D-FFT) as a new technique for the discrimination of kraft tapes, which is a kind of adhesive packing tape. The 2D power spectrum (2D-PS) obtained by applying 2D-FFT to an image enables us to obtain information about the spatial periodicity, even if the periodicity is invisible within the image. However, in the case of kraft tape, peaks in the 2D-PS are too unclear to determine its periodicity. We developed novel analytical image processes combined with 2D-FFT. 2D-FFT was applied to 50 randomly selected areas in a transmitted light image of kraft tape. The 2D-PSs were calculated from each area without applying a logarithmic transformation, accumulated, and processed by the removal of the area surrounding the center, and finally normalized for visualization. These processes enhanced the peaks and eliminated local variations. Through an intra-roll comparison, the 2D-PSs collected from a roll were similar in the location of the peaks and in their patterns at low frequency area. Using an inter-roll comparison, the 2D-PSs from 50 commercially available brand-name products were classified into 26 groups based on these peaks and patterns. All results demonstrate that this method, which is convenient, rapid, and non-destructive, could be a valuable tool for the identification of kraft tapes. PMID:22341568

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

    PubMed

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

    2006-09-01

    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

  17. Holographic microscope for phase imaging

    NASA Astrophysics Data System (ADS)

    Brody, Philip S.; Garvin, Charles G.; Gillman, Arthur W.; Shentu, Lian

    1992-01-01

    We describe a transmission video processing microscope that uses a temporary hologram recorded in real time to provide phase-conjugate illumination of phase and mixed phase and absorption objects. It uses the aberration-removal capabilities of phase conjugation to (1) produce phase contrast in phase objects, (2) make motion in phase objects visible by creating contrast only for moving elements, and (3) eliminate phase background due to an embedding medium or to phase-modulating structures in absorbing (intensity) objects.

  18. Translational Diffusion of Fluorescent Proteins by Molecular Fourier Imaging Correlation Spectroscopy

    PubMed Central

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

    2006-01-01

    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 component of the fluctuating density of a small population of fluorescent molecules, and provides information about the distribution of molecular diffusivities. A theoretical analysis is presented that expresses the detected signal fluctuations in terms of the relevant time-correlation functions for molecular translational diffusion. Furthermore, the role played by optical orientational degrees of freedom is established. We report Fickian self-diffusion of the DsRed tetramer at short timescales. The long-time deviation of our data from Fickian behavior is used to determine the variance of the distribution of the protein self-diffusion coefficient. We compare our results to the expected outcomes for 1), a bi-disperse distribution of protein species, and 2), dynamic disorder of the host solvent. PMID:16920833

  19. INTERFACE OF A REVERSE-PHASE HIGH-PERFORMANCE LIQUID CHROMATOGRAPH WITH A DIFFUSE REFLECTANCE FOURIER TRANSFORM INFRARED SPECTROMETER

    EPA Science Inventory

    An approach to the interface of a reverse-phase high-performance liquid chromatograph and a Fourier transform infrared spectrometer has been developed in which the solutes eluting from the column are continuously extracted into dichloromethane. The application of both flow cell a...

  20. Mathematical Investigation of Gamma Ray and Neutron Absorption Grid Patterns for Homeland Defense Related Fourier Imaging Systems

    NASA Technical Reports Server (NTRS)

    Boccio, Dona

    2003-01-01

    Terrorist suitcase nuclear devices typically using converted Soviet tactical nuclear warheads contain several kilograms of plutonium. This quantity of plutonium emits a significant number of gamma rays and neutrons as it undergoes radioactive decay. These gamma rays and neutrons normally penetrate ordinary matter to a significant distance. Unfortunately this penetrating quality of the radiation makes imaging with classical optics impractical. However, this radiation signature emitted by the nuclear source may be sufficient to be imaged from low-flying aerial platforms carrying Fourier imaging systems. The Fourier imaging system uses a pair of co-aligned absorption grids to measure a selected range of spatial frequencies from an object. These grids typically measure the spatial frequency in only one direction at a time. A grid pair that looks in all directions simultaneously would be an improvement over existing technology. A number of grid pairs governed by various parameters were investigated to solve this problem. By examining numerous configurations, it became apparent that an appropriate spiral pattern could be made to work. A set of equations was found to describe a grid pattern that produces straight fringes. Straight fringes represent a Fourier transform of a point source at infinity. An inverse Fourier transform of this fringe pattern would provide an accurate image (location and intensity) of a point source.

  1. Digital pathology with Fourier ptychography.

    PubMed

    Horstmeyer, Roarke; Ou, Xiaoze; Zheng, Guoan; Willems, Phil; Yang, Changhuei

    2015-06-01

    Fourier ptychographic microscopy (FPM) is a recently introduced method of acquiring high-resolution, wide field of view (FOV) giga-pixel histology images. The FPM procedure first acquires a sequence of low-resolution images of a sample under variable-angle illumination. It then combines these images using a novel phase retrieval algorithm to improve the employed microscope's resolution beyond its conventional limit. Here, we first describe how FPM's resolution improvement can enhance wide FOV histology imaging. Second, we show that FPM also records a thin sample's optical phase, which can help pathologists digitally extract as much information as possible from a given histology slide. PMID:25481664

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

    NASA Astrophysics Data System (ADS)

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

    2013-08-01

    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.

  3. Single-shot X-ray phase-contrast imaging using two-dimensional gratings

    NASA Astrophysics Data System (ADS)

    Sato, Genta; Itoh, Hidenosuke; Nagai, Kentaro; Nakamura, Takashi; Yamaguchi, Kimiaki; Kondoh, Takeshi; Handa, Soichiro; Ouchi, Chidane; Teshima, Takayuki; Setomoto, Yutaka; Den, Toru

    2012-07-01

    We developed a two-dimensional gratings-based X-ray interferometer that requires only a single exposure for clinical radiography. The interferometer consisted of a checkerboard phase grating for ? phase modulation and a latticed amplitude grating. Using a synchrotron radiation source, the phase grating modulates the X-rays and generates a self-image, transformed to a moiré fringe by the amplitude grating. To allow use of a conventional X-ray tube, the latticed source grating was installed downstream from the X-ray tube. Differential phase-contrast and scattering images in two orthogonal directions were obtained by Fourier analysis of the single moiré fringe image and an absorption image. Results show that characteristic features of soft tissue in two orthogonal directions were clearly shown in the differential phase-contrast images.

  4. Mapping agroecological zones and time lag in vegetation growth by means of fourier analysis of time series of NDVI images

    Microsoft Academic Search

    M. Menenti; S. Azzali; W. Verhoef; R. van Swol

    1993-01-01

    Examples are presented of applications of a Fast Fourier transform algorithm to analyse time series of images of Normalized Difference Vegetation Index (NDVI) values. The results obtained for a case study on Zambia indicated that differences in vegetation development among map units of an existing agroclimatic map were not significant, while reliable differences were observed among the map units obtained

  5. EFFICIENT IMAGE RECONSTRUCTION USING PARTIAL 2D FOURIER TRANSFORM L. Deng, C.-L. Yu, C. Chakrabarti

    E-print Network

    Kambhampati, Subbarao

    -II Pro -100 FPGA and a DDR SDRAM. It can process 512 Ã? 512 sized Fourier im- age with 128 Ã? 128 nonzero the implementation of the new reconstruction algorithm on a Xilinx Virtex-II Pro-100 FPGA. For 512 Ã? 512 natural; image reconstruc- tion; FPGA; row-column decomposition; two dimensional de- composition 1. INTRODUCTION

  6. Reduction of periodic noise in Fourier domain optical coherence to-mography images by frequency domain filtering

    E-print Network

    Lübeck, Universität zu

    precise system calibration and additional reference signal measurement. Usually any periodic and quasi- periodic noise leads to the appearance of peaks in the im- age spectrum amplitude. We propose in this paperReduction of periodic noise in Fourier domain optical coherence to- mography images by frequency

  7. a CW Phased Array Ultrasonic Imaging System.

    NASA Astrophysics Data System (ADS)

    Fesler, Kenneth Alan

    1985-06-01

    The goal of this work was to build a digitally scanned and focused ultrasonic phased array imaging system. The system was to consist of two piezoelectric transducer arrays containing 128 elements, transmitting and receiving analog electronics, digital phase controllers, system control electronics, external RF signal processing and a computer to be used for control of the imaging system and the collection and analysis of data. After succeeding in this, the imaging system was reconfigured to provide the first doubly scanned and focused array system, using the transmitting and receiving arrays simultaneously. In other experiments, an entirely new type of ultrasonic transducer array was developed and tested utilizing the piezoelectric material PVF(,2). Bulk wave PVF(,2) arrays for use in liquids were produced and tested and found to perform extremely well. PVF(,2) surface wave arrays were also fabricated and tested for surface acoustic wave scanning on silicon nitride slabs. In a new direction, the phased array imaging system was then modified to determine if it would be possible to produce phase measurements. Several methods of phase imaging by mechanical scan with the phased array system were developed and tested successfully. As a final topic, an entirely different approach to phase imaging, more closely akin to holography, is suggested here as possibly a more effective imaging technique for use with quasi-CW phased array imaging systems.

  8. Light-field-based phase imaging

    NASA Astrophysics Data System (ADS)

    Liu, Jingdan; Xu, Tingfa; Yue, Weirui; Situ, Guohai

    2014-10-01

    Phase contains important information about the diffraction or scattering property of an object, and therefore the imaging of phase is vital to many applications including biomedicine and metrology, just name a few. However, due to the limited bandwidth of image sensors, it is not possible to directly detect the phase of an optical field. Many methods including the Transport of Intensity Equation (TIE) have been well demonstrated for quantitative and non-interferometric imaging of phase. The TIE offers an experimentally simple technique for computing phase quantitatively from two or more defocused images. Usually, the defocused images were experimentally obtained by shifting the camera along the optical axis with slight intervals. Note that light field imaging has the capability to take an image stack focused at different depths by digital refocusing the captured light field of a scene. In this paper, we propose to combine Light Field Microscopy and the TIE method for phase imaging, taking the digital-refocusing advantage of Light Field Microscopy. We demonstrate the propose technique by simulation results. Compare with the traditional camera-shifting technique, light-field imaging allows the capturing the defocused images without any mechanical instability and therefore demonstrate advantage in practical applications.

  9. Phase contrast imaging of cochlear soft tissue

    NASA Astrophysics Data System (ADS)

    Shintani Smith, Stephanie; Hwang, Margaret; Rau, Christoph; Fishman, Andrew J.; Lee, Wah-Keat; Richter, Claus-Peter

    2011-03-01

    A noninvasive technique to image soft tissue could expedite diagnosis and disease management in the auditory system. We propose inline phase contrast imaging with hard X-rays as a novel method that overcomes the limitations of conventional absorption radiography for imaging soft tissue. In this study, phase contrast imaging of mouse cochleae was performed at the Argonne National Laboratory Advanced Photon Source. The phase contrast tomographic reconstructions show soft tissue structures of the cochlea, including the inner pillar cells, the inner spiral sulcus, the tectorial membrane, the basilar membrane, and the Reissner's membrane. The results suggest that phase contrast X-ray imaging and tomographic techniques hold promise to noninvasively image cochlear structures at an unprecedented cellular level.

  10. Phase contrast imaging of cochlear soft tissue.

    SciTech Connect

    Smith, S.; Hwang, M.; Rau, C.; Fishman, A.; Lee, W.; Richter, C. (X-Ray Science Division); (Northwestern Univ.); (Diamond Light Source, Ltd.)

    2011-01-01

    A noninvasive technique to image soft tissue could expedite diagnosis and disease management in the auditory system. We propose inline phase contrast imaging with hard X-rays as a novel method that overcomes the limitations of conventional absorption radiography for imaging soft tissue. In this study, phase contrast imaging of mouse cochleae was performed at the Argonne National Laboratory Advanced Photon Source. The phase contrast tomographic reconstructions show soft tissue structures of the cochlea, including the inner pillar cells, the inner spiral sulcus, the tectorial membrane, the basilar membrane, and the Reissner's membrane. The results suggest that phase contrast X-ray imaging and tomographic techniques hold promise to noninvasively image cochlear structures at an unprecedented cellular level.

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

    E-print Network

    Potsaid, Benjamin M.

    We demonstrate ultrahigh speed swept source/Fourier domain ophthalmic OCT imaging using a short cavity swept laser at 100,000 – 400,000 axial scan rates. Several design configurations illustrate tradeoffs in imaging speed, ...

  12. Design of a high aperture compression ratio, dual-band static Fourier transform imaging spectrometer for remote sensing

    NASA Astrophysics Data System (ADS)

    Zou, Chun-bo; Hu, Bing-Liang; Li, Li-bo; Bai, Qing-Lan; Sun, Xin; Li, Ran; Yang, Jian-Feng

    2014-11-01

    A novel dual-band static Fourier transform imaging spectrometer was designed, which was the spatio-temporally modulated imaging Fourier transform spectrometer based on Sagnac interferometer. The approach represented a simplification and mass reduction over the traditional approach. It could obtain two-dimensional spatial images and one dimensional spectral image in two bands simultaneously. The two bands was separated through a dichroic prism and imaging in two detectors. one band was the visible and near infrared band, with the spectral range 400nm-1000nm and spectral resolution 187.5 wave numbers; the other was the short wave infrared band, with the spectral range 1000nm- 2500nm and spectral resolution 150 wave numbers. To reduce the size of the Interferometer, a high aperture compression ratio telescope system was designed before. The optical aperture was compressed to 1/10, and the volume of interferometer was reduced to 1/1000. For the convenience of engineering implementation, the telescope was composed of two no-aberration object lens: fore-lens and Collimating lens. The two band imaging spectrometers shared the primary lens and the second lens of the fore-lens and use their own collimating lens, interferometers and Fourier transform lens. The collimating lens and the Fourier transform lens of each spectrometer could be designed to the same structural style and parameters. The both spectrometers had a focal length of 1000mm, F number of 5, FOV(field of view) of 1°. Moreover, both image qualities were close to the diffraction limit, the distortion was less than 2%. The advantage of the instrument was that dual band spectral image could be acquired at the same time and the interferometer was miniaturized extremely in the case of unchanged technical indicators.

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

    NASA Astrophysics Data System (ADS)

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

    2011-09-01

    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.

  14. Development of imaging Fourier-transform spectroscopy for the characterization of turbulent jet flames

    NASA Astrophysics Data System (ADS)

    Harley, Jacob L.

    Recent advances in computational models to simulate turbulent, reactive flow fields have outpaced the ability to collect highly constraining data---throughout the entire flow field---for validating and improving such models. In particular, the ability to quantify in three dimensions both the mean scalar fields (i.e. temperature & species concentrations) and their respective fluctuation statistics via hyperspectral imaging would be a game-changing advancement in combustion diagnostics, with high impact in both validation and improvement efforts for computational combustion models. This research effort establishes imaging Fourier- transform spectrometry (IFTS) as a valuable tool (which complements laser diagnostics) for the study of turbulent combustion. Specifically, this effort (1) demonstrates that IFTS can be used to quantitatively measure spatially resolved spectra from a canonical turbulent flame; (2) establishes the utility of quantile spectra in first-ever quantitative comparisons between measured and modeled turbulent radiation interaction (TRI); (3) develops a simple onion-peeling-like spectral inversion methodology suitable for estimating radial scalar distributions in axisymmetric, optically-thick flames; (4) builds understanding of quantile spectra and demonstrates proof of concept for their use in estimating scalar fluctuation statistics.

  15. A Fourier-based method for the restoration of chopped and nodded images

    NASA Astrophysics Data System (ADS)

    Bertero, M.; Boccacci, P.; Custo, A.; De Mol, C.; Robberto, M.

    2003-08-01

    In a series of previous papers we have proposed and validated an iterative method, known as the projected Landweber method, for the restoration of astronomical images taken in chopping and nodding mode. While the method generally provides good results, it may also generate artifacts related to the huge non-uniqueness of the solution of the restoration problem. If the image satisfies additional boundary conditions, the non-uniqueness can be reduced, or even entirely removed. In this paper we investigate the case of periodic boundary conditions, which apply, in particular, to the case of a target area surrounded by a suitable region of empty sky. Periodic boundary conditions do not entirely remove the non-uniqueness of the solution, but allow using Fourier-based techniques. We introduce a new iterative method which can be considered as a relaxed and projected version of the van Cittert method. We formally demonstrate why this method does not produce the artifacts generated by the one we previously proposed, and we present numerical simulations confirming this result. We illustrate the convergence properties of the algorithm in the case of both compact and extended sources. Finally, we briefly discuss the potential and the limitations of the proposed technique.

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

    SciTech Connect

    Abbink, R.E.

    1997-06-01

    This document is the final report on work performed at Sandia National Laboratories during FY 1992 and 1993 for a Laboratory Directed Research and Development (LDRD) program to look at problems associated with the design and long term operation of a short wavelength imaging Fourier Transform (FT) spectrometer for use in space. In attempts to answer two fundamental questions: is a FT spectrometer with a resolution of 1 cm{sup {minus}1} covering the silicon detector wavelength range of 0.4 to 1.1 microns feasible in a long life space instrument and, if so, is it the best method of obtaining the desired information? Emphasis has been on identifying methods which minimize reliance on precision mechanical alignment and precise velocity control. An important consideration has also been to develop methods which will be compatible with a variety of self-scanning solid state imaging devices. A breadboard instrument was constructed using cube corner retroreflectors and a laser diode position reference. Some preliminary results are reported. This work is primarily intended to act as an aid to engineers at Sandia who wish to pursue the fabrication of a flight qualified instrument. The theoretical parts are intended to be somewhat tutorial in nature to aid the engineer who is not familiar with FT spectroscopy.

  17. Symmetric Phase-Only Filtering in Particle-Image Velocimetry

    NASA Technical Reports Server (NTRS)

    Wemet, Mark P.

    2008-01-01

    Symmetrical phase-only filtering (SPOF) can be exploited to obtain substantial improvements in the results of data processing in particle-image velocimetry (PIV). In comparison with traditional PIV data processing, SPOF PIV data processing yields narrower and larger amplitude correlation peaks, thereby providing more-accurate velocity estimates. The higher signal-to-noise ratios associated with the higher amplitude correlation peaks afford greater robustness and reliability of processing. SPOF also affords superior performance in the presence of surface flare light and/or background light. SPOF algorithms can readily be incorporated into pre-existing algorithms used to process digitized image data in PIV, without significantly increasing processing times. A summary of PIV and traditional PIV data processing is prerequisite to a meaningful description of SPOF PIV processing. In PIV, a pulsed laser is used to illuminate a substantially planar region of a flowing fluid in which particles are entrained. An electronic camera records digital images of the particles at two instants of time. The components of velocity of the fluid in the illuminated plane can be obtained by determining the displacements of particles between the two illumination pulses. The objective in PIV data processing is to compute the particle displacements from the digital image data. In traditional PIV data processing, to which the present innovation applies, the two images are divided into a grid of subregions and the displacements determined from cross-correlations between the corresponding sub-regions in the first and second images. The cross-correlation process begins with the calculation of the Fourier transforms (or fast Fourier transforms) of the subregion portions of the images. The Fourier transforms from the corresponding subregions are multiplied, and this product is inverse Fourier transformed, yielding the cross-correlation intensity distribution. The average displacement of the particles across a subregion results in a displacement of the correlation peak from the center of the correlation plane. The velocity is then computed from the displacement of the correlation peak and the time between the recording of the two images. The process as described thus far is performed for all the subregions. The resulting set of velocities in grid cells amounts to a velocity vector map of the flow field recorded on the image plane. In traditional PIV processing, surface flare light and bright background light give rise to a large, broad correlation peak, at the center of the correlation plane, that can overwhelm the true particle- displacement correlation peak. This has made it necessary to resort to tedious image-masking and background-subtraction procedures to recover the relatively small amplitude particle-displacement correlation peak. SPOF is a variant of phase-only filtering (POF), which, in turn, is a variant of matched spatial filtering (MSF). In MSF, one projects a first image (denoted the input image) onto a second image (denoted the filter) as part of a computation to determine how much and what part of the filter is present in the input image. MSF is equivalent to cross-correlation. In POF, the frequency-domain content of the MSF filter is modified to produce a unitamplitude (phase-only) object. POF is implemented by normalizing the Fourier transform of the filter by its magnitude. The advantage of POFs is that they yield correlation peaks that are sharper and have higher signal-to-noise ratios than those obtained through traditional MSF. In the SPOF, these benefits of POF can be extended to PIV data processing. The SPOF yields even better performance than the POF approach, which is uniquely applicable to PIV type image data. In SPOF as now applied to PIV data processing, a subregion of the first image is treated as the input image and the corresponding subregion of the second image is treated as the filter. The Fourier transforms from both the firs and second- image subregions are normalized by the square roots of their respective magnitudes.

  18. 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

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

    1999-10-01

    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

  19. Applications of semi-implicit Fourier-spectral method to phase

    E-print Network

    Fourier space (see [12,13]). Unfortunately ... To reduce the computational cost, the nonlinear term. {f(17")}k should be ..... modeling microstructural evolution, JOM 48 (1996) 13—18. D. Gottlieb, S.A. Orszag, Numerical Analysis of. Spectral

  20. Fourier transform infrared spectroscopic imaging identifies early biochemical markers of tissue damage

    NASA Astrophysics Data System (ADS)

    Varma, Vishal K.; Ohlander, Samuel; Nguyen, Peter; Vendryes, Christopher; Parthiban, Sujeeth; Hamilton, Blake; Wallis, M. Chad; Kajdacsy-Balla, Andre; Hannaford, Blake; Lendvay, Thomas; Hotaling, James M.; Walsh, Michael J.

    2014-03-01

    Fourier Transform Infrared (FT-IR) spectroscopic imaging can allow for the rapid imaging of tissue biochemistry in a label-free and non-perturbing fashion. With the rapid adoption of new minimally invasive surgery (MIS) technologies over the last 20 years, adequate skill to safely and effectively use these technologies may not be achieved and risk of undue physical pressure being placed on tissues is a concern. Previous work has demonstrated that a number of histological stains can detect tissue damage, however, this process requires the initiation and progression of a signaling cascade that results in the epitope of interest being expressed. We proposed to identify the early biochemical markers associated with physical tissue damage from applied forces, thus not requiring transcriptional and translational protein synthesis as traditional immunohistochemistry does. To demonstrate that FT-IR can measure biochemical changes in tissues that have undergone physical force, we took ex-vivo lamb's liver that had been freshly excised and applied varying levels of physical pressure (0kPa to 30kPa). Tissues were then formalin-fixed, paraffin-embedded, and sectioned on to glass for H and E staining to identify damage and on to an IR slide for FT-IR imaging. Regions of interest containing hepatocytes were identified and average FT-IR spectra were extracted from the damaged and undamaged livers. FT-IR spectra showed clear biochemical changes associated with tissue damage. In addition, chemical changes could be observed proceeding histological changes observed when using conventional staining approaches.

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

    DOEpatents

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

    2000-01-01

    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.

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

    PubMed Central

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

    2009-01-01

    Phase interactions among signals of physical and physiological systems can provide useful information about the underlying control mechanisms of the systems. Physical and biological recordings are often noisy and exhibit nonstationarities that can affect the estimation of phase interactions. We systematically studied effects of nonstationarities on two phase analyses including (i) the widely used transfer function analysis (TFA) that is based on Fourier decomposition and (ii) the recently proposed multimodal pressure flow (MMPF) analysis that is based on Hilbert-Huang transform (HHT) —an advanced nonlinear decomposition algorithm. We considered three types of nonstationarities that are often presented in physical and physiological signals: (i) missing segments of data, (ii) linear and step-function trends embedded in data, and (iii) multiple chaotic oscillatory components at different frequencies in data. By generating two coupled oscillatory signals with an assigned phase shift, we quantify the change in the estimated phase shift after imposing artificial nonstationarities into the oscillatory signals. We found that all three types of nonstationarities affect the performances of the Fourier-based and the HHT-based phase analyses, introducing bias and random errors in the estimation of the phase shift between two oscillatory signals. We also provided examples of nonstationarities in real physiological data (cerebral blood flow and blood pressure) and showed how nonstationarities can complicate result interpretation. Furthermore, we propose certain strategies that can be implemented in the TFA and the MMPF methods to reduce the effects of nonstationarities, thus improving the performances of the two methods. PMID:19658541

  3. X-Ray Phase-Contrast Imaging: Phase Reconstructions

    Microsoft Academic Search

    Xizeng Wu; Hong Liu

    2005-01-01

    Clinical X-ray imaging has always been based on the biological tissue's differences in X-ray attenuation ever since Roentgen discovered X-ray over 100 years ago. However X-ray-tissue interaction causes X-ray phase changes as well. We have identified the four clinically important factors that affect the X-ray phase visibility in clinical imaging. These factors are: body part attenuation, the spatial coherence of

  4. Genetic Algorithm Phase Retrieval for the Systematic Image-Based Optical Alignment Testbed

    NASA Technical Reports Server (NTRS)

    Taylor, Jaime; Rakoczy, John; Steincamp, James

    2003-01-01

    Phase retrieval requires calculation of the real-valued phase of the pupil fimction from the image intensity distribution and characteristics of an optical system. Genetic 'algorithms were used to solve two one-dimensional phase retrieval problem. A GA successfully estimated the coefficients of a polynomial expansion of the phase when the number of coefficients was correctly specified. A GA also successfully estimated the multiple p h e s of a segmented optical system analogous to the seven-mirror Systematic Image-Based Optical Alignment (SIBOA) testbed located at NASA s Marshall Space Flight Center. The SIBOA testbed was developed to investigate phase retrieval techniques. Tiphilt and piston motions of the mirrors accomplish phase corrections. A constant phase over each mirror can be achieved by an independent tip/tilt correction: the phase Conection term can then be factored out of the Discrete Fourier Tranform (DFT), greatly reducing computations.

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

    NASA Astrophysics Data System (ADS)

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

    2012-05-01

    Myocardial infarction often leads to an increase in deposition of fibrillar collagen. Detection and characterization of this cardiac fibrosis is of great interest to investigators and clinicians. Motivated by the significant limitations of conventional staining techniques to visualize collagen deposition in cardiac tissue sections, we have developed a Fourier transform infrared imaging spectroscopy (FT-IRIS) methodology for collagen assessment. The infrared absorbance band centered at 1338 cm-1, which arises from collagen amino acid side chain vibrations, was used to map collagen deposition across heart tissue sections of a rat model of myocardial infarction, and was compared to conventional staining techniques. Comparison of the size of the collagen scar in heart tissue sections as measured with this methodology and that of trichrome staining showed a strong correlation (R=0.93). A Pearson correlation model between local intensity values in FT-IRIS and immuno-histochemical staining of collagen type I also showed a strong correlation (R=0.86). We demonstrate that FT-IRIS methodology can be utilized to visualize cardiac collagen deposition. In addition, given that vibrational spectroscopic data on proteins reflect molecular features, it also has the potential to provide additional information about the molecular structure of cardiac extracellular matrix proteins and their alterations.

  6. Phase-space measurement for depth-resolved memory-effect imaging.

    PubMed

    Takasaki, Kevin T; Fleischer, Jason W

    2014-12-15

    Random scattering of light by a turbid layer prevents conventional imaging of objects hidden behind it. Angular correlations in the scattered light, created by the so-called optical memory effect, have been shown to enable computational image retrieval of hidden sources. However, basic memory-effect imaging contains no spatial (x) information, as only angular (k-space) measurements are made. Here, we use windowed Fourier transforms to record scattered-light images in the full {x,k} phase space. The result is the ability to discriminate size and depth of individual sources that are hidden behind a thin scattering layer. PMID:25607092

  7. Fuzzy Logic Classification of Imaging Laser Desorption Fourier Transform Mass Spectrometry Data

    SciTech Connect

    Timothy R. McJunkin; Jill R. Scott

    2008-06-01

    The fuzzy logic method is applied to classification of mass spectra obtained with an imaging internal source Fourier transform mass spectrometer (I2LD-FTMS). Traditionally, an operator uses the relative abundance of ions with specific mass-to-charge (m/z) ratios to categorize spectra. An operator does this by comparing the spectrum of m/z versus abundance of an unknown sample against a library of spectra from known samples. Automated positioning and acquisition allow the I2LD-FTMS to acquire data from very large grids, which would require classification of up to 3600 spectra per hour to keep pace with the acquisition. The tedious job of classifying numerous spectra generated in an I2LD-FTMS imaging application can be replaced by a fuzzy rule base if the cues an operator uses can be encapsulated. Appropriate methods for assigning fuzzy membership values for inputs (e.g., mass spectrum abundances) and choice of fuzzy inference operators to translate linguistic antecedent into confidence values for the consequence (or in this case the classification) is followed by using the maximum confidence and a necessary minimum threshold for making a crisp decision. This paper also describes a method for gathering statistics on ions, which are not currently used in the rule base, but which may be candidates for making the rule base more accurate and complete or to form new rule bases based on data obtained from known samples. A spatial method for classifying spectra with low membership values, based on neighboring sample classifications, is also presented.

  8. Remote quantification of smokestack effluent mass flow rates using imaging Fourier transform spectrometry

    NASA Astrophysics Data System (ADS)

    Harley, Jacob L.; Gross, Kevin C.

    2011-05-01

    A Telops Hyper-Cam midwave infrared (1.5 - 5.5?m) imaging Fourier-transform spectrometer (IFTS) was used to estimate industrial smokestack total effluent mass flow rates by combining spectrally-determined species concentrations with flow rates estimated via analysis of sequential images in the raw interferogram cube. Measurements of the coalburning smokestack were made with the IFTS at a stand-off distance of 350m. 185 hyperspectral datacubes were collected on a 128(W)×64(H) pixel sub-window (11.4×11.4cm2 per pixel) at a 0.5cm-1 spectral resolution. Strong emissions from H2O, CO2, CO, SO2, and NO were observed in the spectrum. A previously established single-layer radiative transfer model was used to estimate gas concentrations immediately above stack exit, and results compared reasonably with in situ measurements. A simple temporal cross-correlation analysis of sequential imagery enabled an estimation of the flow velocity at center stack. The estimated volumetric flow rate of 106+/-23m/s was within 4% of the reported value. Final effluent mass flow rates for CO2 and SO2 of 13.5+/-3.8kg/s and 71.3+/-19.3g/s were in good agreement with in situ rates of 11.6+/-0.1kg/s and 67.8+/-0.5g/s. NO was estimated at 16.1+/-4.2g/s, which did not compare well to the total NOx (NO +NO2) reported value of 11.2+/-0.2g/s. Unmonitored H2O, HCl , and CO were also estimated at 7.76+/-2.25kg/s, 7.40+/-2.00g/s, and 15.0+/-4.1 g/s respectively.

  9. Fourier Transform Infrared Imaging and Infrared Fiber Optic Probe Spectroscopy Identify Collagen Type in Connective Tissues

    PubMed Central

    Hanifi, Arash; McCarthy, Helen; Roberts, Sally; Pleshko, Nancy

    2013-01-01

    Hyaline cartilage and mechanically inferior fibrocartilage consisting of mixed collagen types are frequently found together in repairing articular cartilage. The present study seeks to develop methodology to identify collagen type and other tissue components using Fourier transform infrared (FTIR) spectral evaluation of matrix composition in combination with multivariate analyses. FTIR spectra of the primary molecular components of repair cartilage, types I and II collagen, and aggrecan, were used to develop multivariate spectral models for discrimination of the matrix components of the tissues of interest. Infrared imaging data were collected from bovine bone, tendon, normal cartilage, meniscus and human repair cartilage tissues, and composition predicted using partial least squares analyses. Histology and immunohistochemistry results were used as standards for validation. Infrared fiber optic probe spectral data were also obtained from meniscus (a tissue with mixed collagen types) to evaluate the potential of this method for identification of collagen type in a minimally-invasive clinical application. Concentration profiles of the tissue components obtained from multivariate analysis were in excellent agreement with histology and immunohistochemistry results. Bone and tendon showed a uniform distribution of predominantly type I collagen through the tissue. Normal cartilage showed a distribution of type II collagen and proteoglycan similar to the known composition, while in repair cartilage, the spectral distribution of both types I and II collagen were similar to that observed via immunohistochemistry. Using the probe, the outer and inner regions of the meniscus were shown to be primarily composed of type I and II collagen, respectively, in accordance with immunohistochemistry data. In summary, multivariate analysis of infrared spectra can indeed be used to differentiate collagen type I and type II, even in the presence of proteoglycan, in connective tissues, using both imaging and fiber optic methodology. This has great potential for clinical in situ applications for monitoring tissue repair. PMID:23717662

  10. Phase imaging with thermal neutrons

    Microsoft Academic Search

    Brendan E. Allman; Keith A. Nugent

    2006-01-01

    Across four decades, Sam Werner has built and performed elegant neutron interferometry experiments to measure a variety of quantum mechanical phases. These experiments have stringent requirements on experimental conditions and neutron beam conditioning. However, since refractive variations within a sample redistribute neutron intensity transverse to the propagation direction, a simple experimental geometry permits non-interferometric phase measurement and relaxes beam-conditioning requirements.

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

    NASA Astrophysics Data System (ADS)

    Vasi?, Borislav; Gaji?, Radoš

    2011-09-01

    Using numerical simulations, we investigate the realization of self-focusing media using two-dimensional graded photonic crystals and their applications for imaging and non-imaging purposes. The two-dimensional graded photonic crystals consist of spatially varying cylindrical holes drilled in a dielectric host. By controlling the gradient of the refractive index and the thickness of the self-focusing medium, it is possible to obtain either a focusing lens with Fourier transforming capabilities or an imaging lens, which produces inverted images. Non-imaging applications include a simple antenna for directive emission obtained from the focusing lens, whereas a directional cloak is obtained by modifying the imaging lens. Graded photonic crystal based devices work well up to the Bragg frequencies. They are compact, made from lossless dielectrics, and compatible with planar lithographic techniques, so they can find applications in a broad frequency range, even at the optical frequencies.

  12. Mercury cadmium telluride focal-plane array detection for mid-infrared Fourier-transform spectroscopic imaging.

    PubMed

    Kidder, L H; Levin, I W; Lewis, E N; Kleiman, V D; Heilweil, E J

    1997-05-15

    By combining step-scan Fourier-transform Michelson interferometry, an infrared microscope, and mercury cadmium telluride focal-plane array image detection we have constructed a mid-infrared spectroscopic imaging system that simultaneously records high-fidelity images and spectra of materials from 3500 to 900 cm(-1) (2.8 to 11 microm) at a variety of spectral resolutions. The fidelity of the spectral images is determined by the pixel number density of the focal-plane array. Step-scan imaging principles and instrument design details are outlined. Spatial resolution measurements and infrared chemical imaging examples are presented, and the results are discussed with respect to implications for chemical analysis of biosystems and composite materials. PMID:18185647

  13. Simulations of astronomical imaging phased arrays

    E-print Network

    Saklatvala, George; Hobson, Michael P

    2007-01-01

    We describe a theoretical procedure for analyzing astronomical phased arrays with overlapping beams, and apply the procedure to simulate a simple example. We demonstrate the effect of overlapping beams on the number of degrees of freedom of the array, and on the ability of the array to recover a source. We show that the best images are obtained using overlapping beams, contrary to common practise, and show how the dynamic range of a phased array directly affects the image quality.

  14. Simulations of astronomical imaging phased arrays

    E-print Network

    George Saklatvala; Stafford Withington; Michael P. Hobson

    2007-09-04

    We describe a theoretical procedure for analyzing astronomical phased arrays with overlapping beams, and apply the procedure to simulate a simple example. We demonstrate the effect of overlapping beams on the number of degrees of freedom of the array, and on the ability of the array to recover a source. We show that the best images are obtained using overlapping beams, contrary to common practise, and show how the dynamic range of a phased array directly affects the image quality.

  15. Phase contrast X-ray imaging

    Microsoft Academic Search

    Byung Mook Weon; Jung Ho Je; Yeukuang Hwu

    2006-01-01

    In the last decade X-ray imaging based on phase contrast greatly advanced thanks to the use of unmonochromatic synchrotron hard X-rays. The recent advances are going beyond microradiology and microtomography to reach nanometre scale. This paper reviews basic theory and selected applications to biomedical and materials sciences. The forthcoming improvements in phase contrast X-ray imaging will lead to even better

  16. Nonlinear Ultrasonic Phased Array Imaging

    NASA Astrophysics Data System (ADS)

    Potter, J. N.; Croxford, A. J.; Wilcox, P. D.

    2014-10-01

    This Letter reports a technique for the imaging of acoustic nonlinearity. By contrasting the energy of the diffuse field produced through the focusing of an ultrasonic array by delayed parallel element transmission with that produced by postprocessing of sequential transmission data, acoustic nonlinearity local to the focal point is measured. Spatially isolated wave distortion is inferred without requiring interrogation of the wave at the inspection point, thereby allowing nonlinear imaging through depth.

  17. Phase contrast portal imaging using synchrotron radiation

    SciTech Connect

    Umetani, K., E-mail: umetani@spring8.or.jp [Japan Synchrotron Radiation Research Institute, SPring-8, Sayo-cho, Sayo-gun, Hyogo 679-5198 (Japan); Kondoh, T. [Kobe University Graduate School of Medicine, Kusunoki-cho, Chuo-ku, Kobe-shi, Hyogo 650-0017 (Japan)

    2014-07-15

    Microbeam radiation therapy is an experimental form of radiation treatment with great potential to improve the treatment of many types of cancer. We applied a synchrotron radiation phase contrast technique to portal imaging to improve targeting accuracy for microbeam radiation therapy in experiments using small animals. An X-ray imaging detector was installed 6.0 m downstream from an object to produce a high-contrast edge enhancement effect in propagation-based phase contrast imaging. Images of a mouse head sample were obtained using therapeutic white synchrotron radiation with a mean beam energy of 130 keV. Compared to conventional portal images, remarkably clear images of bones surrounding the cerebrum were acquired in an air environment for positioning brain lesions with respect to the skull structure without confusion with overlapping surface structures.

  18. Phase contrast portal imaging using synchrotron radiation

    NASA Astrophysics Data System (ADS)

    Umetani, K.; Kondoh, T.

    2014-07-01

    Microbeam radiation therapy is an experimental form of radiation treatment with great potential to improve the treatment of many types of cancer. We applied a synchrotron radiation phase contrast technique to portal imaging to improve targeting accuracy for microbeam radiation therapy in experiments using small animals. An X-ray imaging detector was installed 6.0 m downstream from an object to produce a high-contrast edge enhancement effect in propagation-based phase contrast imaging. Images of a mouse head sample were obtained using therapeutic white synchrotron radiation with a mean beam energy of 130 keV. Compared to conventional portal images, remarkably clear images of bones surrounding the cerebrum were acquired in an air environment for positioning brain lesions with respect to the skull structure without confusion with overlapping surface structures.

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

    NASA Astrophysics Data System (ADS)

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

    2008-10-01

    The ultimate remote sensing benefits of the high resolution Infrared radiance spectrometers will be realized with their geostationary satellite implementation in the form of imaging spectrometers. This will enable dynamic features of the atmosphere's thermodynamic fields and pollutant and greenhouse gas constituents to be observed for revolutionary improvements in weather forecasts and more accurate air quality and climate predictions. As an important step toward realizing this application objective, the Geostationary Imaging Fourier Transform Spectrometer (GIFTS) Engineering Demonstration Unit (EDU) was successfully developed under the NASA New Millennium Program, 2000-2006. The GIFTS-EDU instrument employs three focal plane arrays (FPAs), which gather measurements across the long-wave IR (LWIR), short/mid-wave IR (SMWIR), and visible spectral bands. The raw GIFTS interferogram measurements are radiometrically and spectrally calibrated to produce radiance spectra, which are further processed to obtain atmospheric profiles via retrieval algorithms. The radiometric calibration is achieved using internal blackbody calibration references at ambient (260 K) and hot (286 K) temperatures. The absolute radiometric performance of the instrument is affected by several factors including the FPA off-axis effect, detector/readout electronics induced nonlinearity distortions, and fore-optics offsets. The GIFTS-EDU, being the very first imaging spectrometer to use ultra-high speed electronics to readout its large area format focal plane array detectors, operating at wavelengths as large as 15 microns, possessed non-linearity's not easily removable in the initial calibration process. In this paper, we introduce a refined calibration technique that utilizes Principle Component (PC) analysis to compensate for instrument distortions and artifacts remaining after the initial radiometric calibration process, thus, further enhance the absolute calibration accuracy. This method is applied to data collected during an atmospheric measurement experiment with the GIFTS, together with simultaneous observations by the accurately calibrated AERI (Atmospheric Emitted Radiance Interferometer), both simultaneously zenith viewing the sky through the same external scene mirror at ten-minute intervals throughout a cloudless day at Logan Utah on September 13, 2006. The PC vectors of the calibrated radiance spectra are defined from the AERI observations and regression matrices relating the initial GIFTS radiance PC scores to the AERI radiance PC scores are calculated using the least squares inverse method. A new set of accurately calibrated GIFTS radiances are produced using the first four PC scores in the regression model. Temperature and moisture profiles retrieved from the PC-calibrated GIFTS radiances are verified against radiosonde measurements collected throughout the GIFTS sky measurement period.

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

    PubMed Central

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

    2013-01-01

    For scanning x-ray microscopy, many attempts have been made to image the phase contrast based on a concept of the beam being deflected by a specimen, the so-called differential phase contrast imaging (DPC). Despite the successful demonstration in a number of representative cases at moderate spatial resolutions, these methods suffer from various limitations that preclude applications of DPC for ultra-high spatial resolution imaging, where the emerging wave field from the focusing optic tends to be significantly more complicated. In this work, we propose a highly robust and generic approach based on a Fourier-shift fitting process and demonstrate quantitative phase imaging of a solid oxide fuel cell (SOFC) anode by multilayer Laue lenses (MLLs). The high sensitivity of the phase to structural and compositional variations makes our technique extremely powerful in correlating the electrode performance with its buried nanoscale interfacial structures that may be invisible to the absorption and fluorescence contrasts. PMID:23419650

  1. Design, operation and applications of a visible-light confocal scanning Fourier transform Raman microscope for volumetric Raman spectrochemical imaging

    NASA Astrophysics Data System (ADS)

    Brenan, Colin John Herbert

    A new type of confocal Raman microscope called a Fourier transform confocal Raman microscope (FT-CRM) was designed, built and characterized with respect to its spatio-spectral imaging properties. Several different applications of the FT-CRM are presented that take advantage of its unique spectral and spatial imaging characteristics. The instrument combines focused illumination with spatially-filtered detection in a confocal optical configuration to collect photons scattered from a diffraction-limited volume in the sample (typically [<]5×10-18/ m3) and reject photons from outside that region. The molecular vibrational information encoded in the inelastic, or Raman, spectral component of light scattered from the confocal volume is measured with a visible light Fourier transform Raman spectrometer. By scanning the sample relative to the confocal volume, a volumetric Raman spectrochemical image of the sample can be constructed. Raman scattering is an inherently inefficient process; hence an optimal radius pinhole must be found that balances the FT-CRM optical throughput against the microscope spatial resolution and image contrast. Detailed experimental measurements mapped out the FT-CRM spatial response (axial and lateral), optical throughput and image signal-to-background and signal-to-noise ratios as a function of pinhole radius. Excellent agreement was found between these measurements and the predictions of a theoretical microscope model also developed as part of this thesis. Several applications of the FT-CRM included volumetric compositional imaging of three-dimensional chemically inhomogeneous materials such as cellulose and polyester fibers in water or two immiscible optically- similar liquids, water and trichloroehthylene, in a porous quartz sandstone matrix. The potential of the FT- CRM for non-invasive spectrochemical detection and imaging through a turbid tissue-like medium was demonstrated and a new spectral estimator, Fast Orthogonal Search, was evaluated to replace the discrete Fourier transform to improve the microscope performance.

  2. Spectral modulation interferometry for quantitative phase imaging

    PubMed Central

    Shang, Ruibo; Chen, Shichao; Li, Chengshuai; Zhu, Yizheng

    2015-01-01

    We propose a spectral-domain interferometric technique, termed spectral modulation interferometry (SMI), and present its application to high-sensitivity, high-speed, and speckle-free quantitative phase imaging. In SMI, one-dimensional complex field of an object is interferometrically modulated onto a broadband spectrum. Full-field phase and intensity images are obtained by scanning along the orthogonal direction. SMI integrates the high sensitivity of spectral-domain interferometry with the high speed of spectral modulation to quantify fast phase dynamics, and its dispersive and confocal nature eliminates laser speckles. The principle and implementation of SMI are discussed. Its performance is evaluated using static and dynamic objects. PMID:25780737

  3. Data processing pipeline for a time-sampled imaging Fourier transform spectrometer

    E-print Network

    Naylor, David A.

    plants, growth of illegal crops, etc.), earth observations from air/space (crop management, mineral, to study such things as a galaxy's red shift, a cell's DNA or a counterfeit currency. Fourier transform

  4. FPGA-based multi-channel fluorescence lifetime analysis of Fourier multiplexed frequency-sweeping lifetime imaging.

    PubMed

    Zhao, Ming; Li, Yu; Peng, Leilei

    2014-09-22

    We report a fast non-iterative lifetime data analysis method for the Fourier multiplexed frequency-sweeping confocal FLIM (Fm-FLIM) system [Opt. Express 22, 10221 (2014)]. The new method, named R-method, allows fast multi-channel lifetime image analysis in the system's FPGA data processing board. Experimental tests proved that the performance of the R-method is equivalent to that of single-exponential iterative fitting, and its sensitivity is well suited for time-lapse FLIM-FRET imaging of live cells, for example cyclic adenosine monophosphate (cAMP) level imaging with GFP-Epac-mCherry sensors. With the R-method and its FPGA implementation, multi-channel lifetime images can now be generated in real time on the multi-channel frequency-sweeping FLIM system, and live readout of FRET sensors can be performed during time-lapse imaging. PMID:25321778

  5. Synchronous Phase-Resolving Flash Range Imaging

    NASA Technical Reports Server (NTRS)

    Pain, Bedabrata; Hancock, Bruce

    2007-01-01

    An apparatus, now undergoing development, for range imaging based on measurement of the round-trip phase delay of a pulsed laser beam is described. The apparatus would operate in a staring mode. A pulsed laser would illuminate a target. Laser light reflected from the target would be imaged on a verylarge- scale integrated (VLSI)-circuit image detector, each pixel of which would contain a photodetector and a phase-measuring circuit. The round-trip travel time for the reflected laser light incident on each pixel, and thus the distance to the portion of the target imaged in that pixel, would be measured in terms of the phase difference between (1) the photodetector output pulse and (2) a local-oscillator signal that would have a frequency between 10 and 20 MHz and that would be synchronized with the laser-pulse-triggering signal.

  6. From regular text to artistic writing and artworks: Fourier statistics of images with low and high aesthetic appeal

    PubMed Central

    Melmer, Tamara; Amirshahi, Seyed A.; Koch, Michael; Denzler, Joachim; Redies, Christoph

    2013-01-01

    The spatial characteristics of letters and their influence on readability and letter identification have been intensely studied during the last decades. There have been few studies, however, on statistical image properties that reflect more global aspects of text, for example properties that may relate to its aesthetic appeal. It has been shown that natural scenes and a large variety of visual artworks possess a scale-invariant Fourier power spectrum that falls off linearly with increasing frequency in log-log plots. We asked whether images of text share this property. As expected, the Fourier spectrum of images of regular typed or handwritten text is highly anisotropic, i.e., the spectral image properties in vertical, horizontal, and oblique orientations differ. Moreover, the spatial frequency spectra of text images are not scale-invariant in any direction. The decline is shallower in the low-frequency part of the spectrum for text than for aesthetic artworks, whereas, in the high-frequency part, it is steeper. These results indicate that, in general, images of regular text contain less global structure (low spatial frequencies) relative to fine detail (high spatial frequencies) than images of aesthetics artworks. Moreover, we studied images of text with artistic claim (ornate print and calligraphy) and ornamental art. For some measures, these images assume average values intermediate between regular text and aesthetic artworks. Finally, to answer the question of whether the statistical properties measured by us are universal amongst humans or are subject to intercultural differences, we compared images from three different cultural backgrounds (Western, East Asian, and Arabic). Results for different categories (regular text, aesthetic writing, ornamental art, and fine art) were similar across cultures. PMID:23554592

  7. Measurement of fluid rotation, dilation, and displacement in particle image velocimetry using a Fourier–Mellin cross-correlation

    NASA Astrophysics Data System (ADS)

    Giarra, Matthew N.; Charonko, John J.; Vlachos, Pavlos P.

    2015-03-01

    Traditional particle image velocimetry (PIV) uses discrete Cartesian cross correlations (CCs) to estimate the displacements of groups of tracer particles within small subregions of sequentially captured images. However, these CCs fail in regions with large velocity gradients or high rates of rotation. In this paper, we propose a new PIV correlation method based on the Fourier–Mellin transformation (FMT) that enables direct measurement of the rotation and dilation of particle image patterns. In previously unresolvable regions of large rotation, our algorithm significantly improves the velocity estimates compared to traditional correlations by aligning the rotated and stretched particle patterns prior to performing Cartesian correlations to estimate their displacements. Our algorithm, which we term Fourier–Mellin correlation (FMC), reliably measures particle pattern displacement between pairs of interrogation regions with up to ±180° of angular misalignment, compared to 6–8° for traditional correlations, and dilation/compression factors of 0.5–2.0, compared to 0.9–1.1 for a single iteration of traditional correlations. We apply our FMC algorithm to synthetic computer-generated PIV images with known velocity and vorticity fields, and to an experimentally measured flow field. Our results show that combining FMC with discrete window offset (DWO) or iterative image deformation (IID) algorithms decreases the mean and variance of displacement and vorticity errors compared to traditional correlations, and that FMC accelerates the convergence of IID.

  8. Image fusion algorithm for differential phase contrast imaging

    NASA Astrophysics Data System (ADS)

    Roessl, Ewald; Koehler, Thomas; van Stevendaal, Udo; Martens, Gerhard; Hauser, Nik; Wang, Zhentian; Stampanoni, Marco

    2012-03-01

    Differential phase-contrast imaging in the x-ray domain provides three physically complementary signals:1, 2 the attenuation, the differential phase-contrast, related to the refractive index, and the dark-field signal, strongly influenced by the total amount of radiation scattered into very small angles. In medical applications, it is of the utmost importance to present to the radiologist all clinically relevant information in as compact a way as possible. Hence, the need arises for a method to combine two or more of the above mentioned signals into one image containing all information relevant for diagnosis. We present an image composition algorithm that fuses the attenuation image and the differential phase contrast image into a composite, final image based on the assumption that the real and imaginary part of the complex refractive index of the sample can be related by a constant scaling factor. The merging is performed in such a way that the composite image is characterized by minimal noise-power at each frequency component.

  9. Molecular-scale imaging of unstained deoxyribonucleic acid fibers by phase transmission electron microscopy

    SciTech Connect

    Takai, Yoshizo; Nomaguchi, Tsunenori; Matsushita, Shuhei; Kimura, Yoshihide [Department of Material and Life Science, Graduate School of Engineering, Osaka University, 2-1 Yamada-oka, Suita, Osaka 565-0879 (Japan)

    2006-09-25

    The molecular structure of deoxyribonucleic acid (DNA) fibers was observed by a phase reconstruction method called three-dimensional Fourier filtering using a 200 kV transmission electron microscope. The characteristic helical structure and the spacing of adjacent base pairs of DNA were partially resolved due to an improved signal-to-noise ratio and resolution enhancement by the phase reconstruction although the molecular structure was damaged by the electron beam irradiation. In the spherical aberration-free phase images, the arrangements of single atom-sized spots forming sinusoidal curves were sometimes observed, which seem to be the contrast originating in the sulfur atoms along the main chains.

  10. Image Display and Manipulation System (IDAMS) program documentation, Appendixes A-D. [including routines, convolution filtering, image expansion, and fast Fourier transformation

    NASA Technical Reports Server (NTRS)

    Cecil, R. W.; White, R. A.; Szczur, M. R.

    1972-01-01

    The IDAMS Processor is a package of task routines and support software that performs convolution filtering, image expansion, fast Fourier transformation, and other operations on a digital image tape. A unique task control card for that program, together with any necessary parameter cards, selects each processing technique to be applied to the input image. A variable number of tasks can be selected for execution by including the proper task and parameter cards in the input deck. An executive maintains control of the run; it initiates execution of each task in turn and handles any necessary error processing.

  11. A Panchromatic Imaging Fourier Transform Spectrometer for the NASA Geostationary Coastal and Air Pollution Events Mission

    NASA Technical Reports Server (NTRS)

    Wu, Yen-Hung; Key, Richard; Sander, Stanley; Blavier, Jean-Francois; Rider, David

    2011-01-01

    This paper summarizes the design and development of the Panchromatic Imaging Fourier Transform Spectrometer (PanFTS) for the NASA Geostationary Coastal and Air Pollution Events (GEO-CAPE) Mission. The PanFTS instrument will advance the understanding of the global climate and atmospheric chemistry by measuring spectrally resolved outgoing thermal and reflected solar radiation. With continuous spectral coverage from the near-ultraviolet through the thermal infrared, this instrument is designed to measure pollutants, greenhouse gases, and aerosols as called for by the U.S. National Research Council Decadal Survey; Earth Science and Applications from Space: National Imperatives for the Next Decade and Beyond1. The PanFTS instrument is a hybrid instrument based on spectrometers like the Tropospheric Emissions Spectrometer (TES) that measures thermal emission, and those like the Orbiting Carbon Observatory (OCO), and the Ozone Monitoring Instrument (OMI) that measure scattered solar radiation. Simultaneous measurements over the broad spectral range from IR to UV is accomplished by a two sided interferometer with separate optical trains and detectors for the ultraviolet-visible and infrared spectral domains. This allows each side of the instrument to be independently optimized for its respective spectral domain. The overall interferometer design is compact because the two sides share a single high precision cryogenic optical path difference mechanism (OPDM) and metrology laser as well as a number of other instrument systems including the line-of-sight pointing mirror, the data management system, thermal control system, electrical system, and the mechanical structure. The PanFTS breadboard instrument has been tested in the laboratory and demonstrated the basic functionality for simultaneous measurements in the visible and infrared. It is set to begin operations in the field at the California Laboratory for Atmospheric Remote Sensing (CLARS) observatory on Mt. Wilson measuring the atmospheric chemistry across the Los Angeles basin. Development has begun on a flight size PanFTS engineering model (EM) that addresses all critical scaling issues and demonstrates operation over the full spectral range of the flight instrument which will show the PanFTS instrument design is mature.

  12. A Panchromatic Imaging Fourier Transform Spectrometer for the NASA Geostationary Coastal and Air Pollution Events Mission

    NASA Astrophysics Data System (ADS)

    Wu, Yen-Hung; Key, Richard; Sander, Stanley; Blavier, Jean-Francois; Rider, David

    2011-10-01

    This paper summarizes the design and development of the Panchromatic Imaging Fourier Transform Spectrometer (PanFTS) for the NASA Geostationary Coastal and Air Pollution Events (GEO-CAPE) Mission. The PanFTS instrument will advance the understanding of the global climate and atmospheric chemistry by measuring spectrally resolved outgoing thermal and reflected solar radiation. With continuous spectral coverage from the near-ultraviolet through the thermal infrared, this instrument is designed to measure pollutants, greenhouse gases, and aerosols as called for by the U.S. National Research Council Decadal Survey; Earth Science and Applications from Space: National Imperatives for the Next Decade and Beyond1. The PanFTS instrument is a hybrid based on spectrometers like the Tropospheric Emissions Spectrometer (TES) that measures thermal emission, and those like the Orbiting Carbon Observatory (OCO), and the Ozone Monitoring Instrument (OMI) that measure scattered solar radiation. Simultaneous measurements over the broad spectral range from IR to UV is accomplished by a two sided interferometer with separate optical trains and detectors for the UV-visible and IR spectral domains. This allows each side of the instrument to be independently optimized for its respective spectral domain. The overall interferometer design is compact because the two sides share a single high precision cryogenic optical path difference mechanism (OPDM) and metrology laser as well as a number of other instrument systems including the line-of-sight pointing mirror, the data management system, thermal control system, electrical system, and the mechanical structure. The PanFTS breadboard instrument has been tested in the laboratory and demonstrated the basic functionality for simultaneous measurements in the visible and IR. It is set to begin operations in the field at the California Laboratory for Atmospheric Remote Sensing (CLARS) observatory on Mt. Wilson measuring the atmospheric chemistry across the Los Angeles basin. Development has begun on a flight size PanFTS engineering model (EM) that addresses all critical scaling issues and demonstrates operation over the full spectral range of the flight instrument which will show the PanFTS instrument design is mature.

  13. Amplified Dispersive Fourier-Transform Imaging for Ultrafast Displacement Sensing and Barcode Reading

    E-print Network

    Goda, Keisuke; Jalali, Bahram

    2008-01-01

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2008-09-01

    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 25MHz—four orders of magnitude faster than the current state of the art.

  15. Phase Retrieval Using Estimation Methods For Intensity Correlation Imaging

    E-print Network

    Young, Brian T.

    2010-10-12

    Footprint of a single detector in a di raction limited system : : : : : 47 18 Example of a 3 3 TPD detector grid layout : : : : : : : : : : : : : 48 19 Example of super-pixel arrangements for comparison of conver- gence properties... : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 49 20 Reconstructed images for each of the super-pixel test cases, using the noise-free simulation : : : : : : : : : : : : : : : : : : : : : : : : : 50 21 Super-pixel layout and Fourier transform size for three examples used to test varying Fourier...

  16. A Synthetic Quadrature Phase Detector/Demodulator for Fourier Transform Transform Spectrometers

    NASA Technical Reports Server (NTRS)

    Campbell, Joel

    2008-01-01

    A method is developed to demodulate (velocity correct) Fourier transform spectrometer (FTS) data that is taken with an analog to digital converter that digitizes equally spaced in time. This method makes it possible to use simple low cost, high resolution audio digitizers to record high quality data without the need for an event timer or quadrature laser hardware, and makes it possible to use a metrology laser of any wavelength. The reduced parts count and simplicity implementation makes it an attractive alternative in space based applications when compared to previous methods such as the Brault algorithm.

  17. Imaging IR spectrometer, phase 2

    NASA Technical Reports Server (NTRS)

    Gradie, Jonathan; Lewis, Ralph; Lundeen, Thomas; Wang, Shu-I

    1990-01-01

    The development is examined of a prototype multi-channel infrared imaging spectrometer. The design, construction and preliminary performance is described. This instrument is intended for use with JPL Table Mountain telescope as well as the 88 inch UH telescope on Mauna Kea. The instrument is capable of sampling simultaneously the spectral region of 0.9 to 2.6 um at an average spectral resolution of 1 percent using a cooled (77 K) optical bench, a concave holographic grating and a special order sorting filter to allow the acquisition of the full spectral range on a 128 x 128 HgCdTe infrared detector array. The field of view of the spectrometer is 0.5 arcsec/pixel in mapping mode and designed to be 5 arcsec/pixel in spot mode. The innovative optical design has resulted in a small, transportable spectrometer, capable of remote operation. Commercial applications of this spectrometer design include remote sensing from both space and aircraft platforms as well as groundbased astronomical observations.

  18. Amplified Dispersive FourierTransform Imaging for Ultrafast Displacement Sensing and Barcode Reading

    Microsoft Academic Search

    Keisuke God; Kevin K. Tsi; Bahram Jalali

    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

  19. Quadriwave lateral shearing interferometry for quantitative phase microscopy: coupling phase imaging and fluorescence imaging

    NASA Astrophysics Data System (ADS)

    Bon, Pierre; Savatier, Julien; Wattellier, Benoit; Marguet, Didier; Monneret, Serge

    2011-03-01

    Phase imaging with a high-resolution wavefront sensor is a useful setup for biological imaging. Our setup is based on a quadriwave lateral shearing interferometer mounted on a commercial non-modified transmission white-light microscope. That allows us to make simultaneous measurement in both quantitative transmission phase and fluorescence imaging. We propose here to study co-localization between phase and fluorescence on african green monkey kidney COS7 cells. Phase permits an enhanced visualization of the whole cell and intracellular components while the fluorescence allows a complete identification of each component. Post treatments on phase-shift images are proposed and become very interesting for enhanced visualization of small details such as vesicles or mitochondrias.

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

    NASA Astrophysics Data System (ADS)

    Yamashita, Motoi; Hirao, Atsushi; Kato, Minoru

    2011-04-01

    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, and 152-181 MPa for C13, C15, and C17, respectively, and the transition between the HPR and liquid phases was observed in the pressure ranges of 171-112, 73-47, and 43-70 MPa for C13, C15, and C17, respectively. The P1+P3 band of the methylene rocking mode exhibits factor group splitting caused by intermolecular vibrational coupling. This was observed in both the HPO and HPR phases, while the P1+P3 band did not split in the liquid phase. The separation of the peaks in the P1+P3 band changed discontinuously at the HPO-HPR and HPR-liquid phase transitions, even though the separation is known to change continuously in the transition from the liquid to the high temperature rotator (HTR) phase. In the HPR phase, the ratio of the intensities of the higher and lower frequency components in the P1+P3 doublet is roughly unity independent of pressure, while it is known to be much less than unity in the HTR phase. The separation of the P1+P3 doublet in the HPR phase is found to be larger for longer alkanes. From the intensity ratio, a large proportion of alkane molecules is believed to participate in intermolecular vibrational coupling and possess herringbone-type short-range positional order in the HPR phase. Conversely, in the HTR phase only small proportion of alkane molecules participate in intermolecular vibrational coupling. From the pressure dependence of the separation of the doublet, intermolecular vibrational coupling and herringbone-type short-range positional order is considered to change discontinuously at the HPR-liquid phase transition, while they are reported to change continuously at the HTR-liquid phase transition. The HPR-liquid phase transition is governed by the effect of molecular packing while the HTR-liquid phase transition is predominantly governed by the difference in entropy between the herringbone-type and parallel-type packing.

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

    PubMed

    Yamashita, Motoi; Hirao, Atsushi; Kato, Minoru

    2011-04-14

    The effect of pressure on the phase transition behavior of tridecane (C(13)), pentadecane (C(15)), and heptadecane (C(17)) 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, and 152-181 MPa for C(13), C(15), and C(17), respectively, and the transition between the HPR and liquid phases was observed in the pressure ranges of 171-112, 73-47, and 43-70 MPa for C(13), C(15), and C(17), respectively. The P(1)+P(3) band of the methylene rocking mode exhibits factor group splitting caused by intermolecular vibrational coupling. This was observed in both the HPO and HPR phases, while the P(1)+P(3) band did not split in the liquid phase. The separation of the peaks in the P(1)+P(3) band changed discontinuously at the HPO-HPR and HPR-liquid phase transitions, even though the separation is known to change continuously in the transition from the liquid to the high temperature rotator (HTR) phase. In the HPR phase, the ratio of the intensities of the higher and lower frequency components in the P(1)+P(3) doublet is roughly unity independent of pressure, while it is known to be much less than unity in the HTR phase. The separation of the P(1)+P(3) doublet in the HPR phase is found to be larger for longer alkanes. From the intensity ratio, a large proportion of alkane molecules is believed to participate in intermolecular vibrational coupling and possess herringbone-type short-range positional order in the HPR phase. Conversely, in the HTR phase only small proportion of alkane molecules participate in intermolecular vibrational coupling. From the pressure dependence of the separation of the doublet, intermolecular vibrational coupling and herringbone-type short-range positional order is considered to change discontinuously at the HPR-liquid phase transition, while they are reported to change continuously at the HTR-liquid phase transition. The HPR-liquid phase transition is governed by the effect of molecular packing while the HTR-liquid phase transition is predominantly governed by the difference in entropy between the herringbone-type and parallel-type packing. PMID:21495760

  2. Imaging the ocular anterior segment with real-time, full-range Fourier-domain optical coherence tomography.

    PubMed

    Sarunic, Marinko V; Asrani, Sanjay; Izatt, Joseph A

    2008-04-01

    We have demonstrated a novel Fourier-domain optical coherence tomography system and signal-processing algorithm for full-range, real-time, artifact-free quantitative imaging of the anterior chamber. Cross-sectional full-range images comprising 1024 x 800 pixels (axial x lateral) were acquired and displayed at 6.7 images/s. Volumetric data comprising 1024 x 400 x 60 pixels (axial x lateral x elevation) were acquired in 4.5 seconds with real-time visualization of individual slices and 3-dimensional reconstruction performed in postprocessing. Details of the cornea, limbus, iris, anterior lens capsule, trabecular meshwork, and Schlemm's canal were visualized. Quantitative surface height maps of the corneal epithelium and endothelium were obtained from the volumetric data and used to generate corneal thickness maps. PMID:18413525

  3. Attenuated total reflection Fourier transform infrared imaging with variable angles of incidence: a three-dimensional profiling of heterogeneous materials.

    PubMed

    Chan, K L Andrew; Kazarian, Sergei G

    2007-01-01

    Depth profiling in Fourier transform infrared (FT-IR) spectroscopic imaging has been demonstrated using a single reflection variable angle attenuated total reflection (ATR) accessory. Chemical information about samples can be obtained in three dimensions by acquiring ATR-FT-IR images at different angles of incidence through the ATR crystal. The image quality and field of view achieved at different angles of incidence has been discussed. A polymer film comprising two layers has been used as an example to demonstrate the principle of the measurement. The demonstrated approach is a promising tool to obtain depth profiles of heterogeneous materials. The extent of the measured depths is limited and ranges from approximately 0.3 to 4 microm, but the spatial resolution in the z-direction is not limited by diffraction. The development of this approach opens up the possibility to study the spatial heterogeneity of thin films including biological tissues, such as hair and skin, with high depth resolution. PMID:17311716

  4. Phased Contrast X-Ray Imaging

    ScienceCinema

    Erin Miller

    2012-12-31

    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.

  5. Simulations of astronomical imaging phased arrays

    Microsoft Academic Search

    George Saklatvala; Stafford Withington; Michael P. Hobson

    2008-01-01

    We describe a theoretical procedure for analyzing astronomical phased arrays with overlapping beams, and apply the procedure to simulate a simple example. We demonstrate the effect of overlapping beams on the number of degrees of freedom of the array, and on the ability of the array to recover a source. We show that the best images are obtained using overlapping

  6. Level 0 to 1 processing of the imaging Fourier transform spectrometer GLORIA: generation of radiometrically and spectrally calibrated spectra

    NASA Astrophysics Data System (ADS)

    Kleinert, A.; Friedl-Vallon, F.; Guggenmoser, T.; Höpfner, M.; Neubert, T.; Ribalda, R.; Sha, M. K.; Ungermann, J.; Blank, J.; Ebersoldt, A.; Kretschmer, E.; Latzko, T.; Oelhaf, H.; Olschewski, F.; Preusse, P.

    2014-03-01

    The Gimballed Limb Observer for Radiance Imaging of the Atmosphere (GLORIA) is an imaging Fourier transform spectrometer that is capable of operating on various high altitude research aircraft. It measures the atmospheric emission in the thermal infrared spectral region in limb and nadir geometry. GLORIA consists of a classical Michelson interferometer combined with an infrared camera. The infrared detector has a usable range of 128 × 128 pixels, measuring up to 16 384 interferograms simultaneously. Imaging Fourier transform spectrometers impose a number of challenges with respect to instrument calibration and algorithm development. The innovative optical setup with extremely high optical throughput requires the development of new methods and algorithms for spectral and radiometric calibration. Due to the vast amount of data there is a high demand for scientifically intelligent optimisation of the data processing. This paper outlines the characterisation and processing steps required for the generation of radiometrically and spectrally calibrated spectra. Methods for performance optimisation of the processing algorithm are presented. The performance of the data processing and the quality of the calibrated spectra are demonstrated for measurements collected during the first deployments of GLORIA on aircraft.

  7. Level 0 to 1 processing of the imaging Fourier transform spectrometer GLORIA: generation of radiometrically and spectrally calibrated spectra

    NASA Astrophysics Data System (ADS)

    Kleinert, A.; Friedl-Vallon, F.; Guggenmoser, T.; Höpfner, M.; Neubert, T.; Ribalda, R.; Sha, M. K.; Ungermann, J.; Blank, J.; Ebersoldt, A.; Kretschmer, E.; Latzko, T.; Oelhaf, H.; Olschewski, F.; Preusse, P.

    2014-12-01

    The Gimballed Limb Observer for Radiance Imaging of the Atmosphere (GLORIA) is an imaging Fourier transform spectrometer that is capable of operating on various high-altitude research aircraft. It measures the atmospheric emission in the thermal infrared spectral region in limb and nadir geometry. GLORIA consists of a classical Michelson interferometer combined with an infrared camera. The infrared detector has a usable area of 128 × 128 pixels, measuring up to 16 384 interferograms simultaneously. Imaging Fourier transform spectrometers impose a number of challenges with respect to instrument calibration and algorithm development. The optical setup with extremely high optical throughput requires the development of new methods and algorithms for spectral and radiometric calibration. Due to the vast amount of data there is a high demand for scientifically intelligent optimisation of the data processing. This paper outlines the characterisation and processing steps required for the generation of radiometrically and spectrally calibrated spectra. Methods for performance optimisation of the processing algorithm are presented. The performance of the data processing and the quality of the calibrated spectra are demonstrated for measurements collected during the first deployments of GLORIA on aircraft.

  8. Ultrahigh-speed imaging of the rat retina using ultrahigh-resolution spectral/Fourier domain OCT

    NASA Astrophysics Data System (ADS)

    Liu, Jonathan J.; Potsaid, Benjamin; Chen, Yueli; Gorczynska, Iwona; Srinivasan, Vivek J.; Duker, Jay S.; Fujimoto, James G.

    2010-02-01

    We performed OCT imaging of the rat retina at 70,000 axial scans per second with ~3 ?m axial resolution. Three-dimensional OCT (3D-OCT) data sets of the rat retina were acquired. The high speed and high density data sets enable improved en face visualization by reducing eye motion artifacts and improve Doppler OCT measurements. Minimal motion artifacts were visible and the OCT fundus images offer more precise registration of individual OCT images to retinal fundus features. Projection OCT fundus images show features such as the nerve fiber layer, retinal capillary networks and choroidal vasculature. Doppler OCT images and quantitative measurements show pulsatility in retinal blood vessels. Doppler OCT provides noninvasive in vivo quantitative measurements of retinal blood flow properties and may benefit studies of diseases such as glaucoma and diabetic retinopathy. Ultrahigh speed imaging using ultrahigh resolution spectral / Fourier domain OCT promises to enable novel protocols for measuring small animal retinal structure and retinal blood flow. This non-invasive imaging technology is a promising tool for monitoring disease progression in rat and mouse models to assess ocular disease pathogenesis and response to treatment.

  9. Applications of Fourier Domain Mode Locked lasers for optical coherence tomography imaging

    E-print Network

    Adler, Desmond Christopher, 1978-

    2009-01-01

    Optical coherence tomography (OCT) is a micrometer-resolution imaging technique that produces cross-sectional images of sample microstructure by measuring the amplitude and echo time delay of backscattered light. OCT imaging ...

  10. Quantitative Fourier transform infrared analysis of gas phase cigarette smoke and other gas mixtures

    SciTech Connect

    Cueto, R.; Church, D.F.; Pryor, W.A. (Louisiana State Univ., Baton Rouge (USA))

    1989-03-01

    A new method for the analysis of selected components in complex gas mixtures has been developed utilizing a relatively inexpensive Fourier transform infrared spectrometer and a continuous flow gas cell. The method was used to monitor nitric oxide and nitrogen dioxide concentrations in cigarette smoke with time. Using multivariate least-square regression analysis, it is possible to simultaneously quantitate both NO and NO{sub 2}, even in the presence of overlapping peaks. Using this method, the oxidation of nitric oxide in the presence of isoprene in cigarette smoke and in a model system was followed with time. The method also can be applied to other compounds in smoke or to any other gaseous mixture.

  11. Color image hiding based on the phase retrieval technique and Arnold transform.

    PubMed

    Shi, Xiaoyan; Zhao, Daomu

    2011-05-10

    A new (to our knowledge) method is proposed in this paper for color image hiding and extracting using the phase retrieval algorithm in the fractional Fourier transform (FRFT) domain and Arnold transform (ART). Based on a cascaded phase iterative FRFT algorithm, the three channels (R, G, and B) of the secret color image permuted by ART are encrypted. Then the encoded information is embedded in the blue channel (B channel) of the enlarged color host image. Using the security enhanced encryption method, not only the random phase mask and the wavelength but also the transform parameters of ART and FRFT are provided as additional keys for decryption. It is shown that the security of information hiding will be enhanced. Computer simulations are performed to show the hiding capacity of the proposed system. Numerical results are presented to verify the validity and efficiency of the proposed method. PMID:21556114

  12. Phase modulation pseudocolor encoding ghost imaging

    NASA Astrophysics Data System (ADS)

    Duan, De-Yang; Zhang, Lu; Du, Shao-Jiang; Xia, Yun-Jie

    2015-02-01

    We present a ghost imaging scheme that can obtain a good pseudocolor image of black-and-white objects. The essential idea is to use a multi-wavelength thermal light source and the phase modulation pseudocolor encoding technique, which overcomes the disadvantages of other methods involved spatial filtering. Therefore, the pseudocolor ghost image achieved by this imaging scheme is better than that obtained by other methods in terms of brightness, color, and signal-to-noise ratio. Project supported by the National Natural Science Foundation of China (Grant Nos. 61178012, 11204156, 11304179, and 11247240), the Specialized Research Fund for the Doctoral Program of Higher Education of China (Grant Nos. 20133705110001 and 20123705120002), the Scientific Research Foundation for Outstanding Young Scientists of Shandong Province of China (Grant No. BS2013DX034), and the Natural Science Foundation of Shandong Province of China (Grant No. ZR2012FQ024).

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

    NASA Astrophysics Data System (ADS)

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

    2007-04-01

    The type of coupling in a fibre laser array phase locked with the help of an external mirror located at the focal distance from the plane of output ends of individual lasers is studied analytically. The explicit expression is derived for the eigenvalue of the resonator and the restriction on the width of the tuning range in which laser array phase locking is preserved is determined. The influence of the spread in the optical lengths of fibres on the phase-locking efficiency is considered. The phase-locking efficiency is analysed for the spread of optical lengths of fibres considerably exceeding the radiation wavelength.

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

    PubMed Central

    Yin, Jianhua; Xia, Yang; Lu, Mei

    2011-01-01

    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. PMID:22197357

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

    PubMed

    Yin, Jianhua; Xia, Yang; Lu, Mei

    2012-03-01

    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. PMID:22197357

  16. High-speed Fourier domain Optical Coherence Tomography for structural and functional imaging of the retina

    E-print Network

    Srinivasan, Vivek Jay

    2008-01-01

    Optical Coherence Tomography (OCT) is an emerging optical biomedical imaging technology that enables cross-sectional imaging of scattering tissue with high sensitivity and micron-scale resolution. In conventional OCT, the ...

  17. Semiclassical TEM image formation in phase space.

    PubMed

    Lubk, Axel; Röder, Falk

    2015-04-01

    Current developments in TEM such as high-resolution imaging at low acceleration voltages and large fields of view, the ever larger capabilities of hardware aberration correction and the systematic shaping of electron beams require accurate descriptions of TEM imaging in terms of wave optics. Since full quantum mechanic solutions have not yet been established for, e.g., the theory of aberrations, we are exploring semiclassical image formation in the TEM from the perspective of quantum mechanical phase space, here. Firstly, we use two well-known semiclassical approximations, Miller's semiclassical algebra and the frozen Gaussian method, for describing the wave optical generalization of arbitrary geometric aberrations, including nonisoplanatic and slope aberrations. Secondly, we demonstrate that the Wigner function representation of phase space is well suited to also describe incoherent aberrations as well as the ramifications of partial coherence due to the emission process at the electron source. We identify a close relationship between classical phase space and Wigner function distortions due to aberrations as well as classical brightness and quantum mechanical purity. PMID:25579179

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

    Microsoft Academic Search

    Philip De Chazal; John Flynn; Richard B. Reilly

    2005-01-01

    The development of a system for automatically sorting a database of shoeprint images based on the outsole pattern in response to a reference shoeprint image is presented. The database images are sorted so that those from the same pattern group as the reference shoeprint are likely to be at the start of the list. A database of 476 complete shoeprint

  19. Extending Single-Molecule Microscopy Using Optical Fourier Processing

    PubMed Central

    2015-01-01

    This article surveys the recent application of optical Fourier processing to the long-established but still expanding field of single-molecule imaging and microscopy. A variety of single-molecule studies can benefit from the additional image information that can be obtained by modulating the Fourier, or pupil, plane of a widefield microscope. After briefly reviewing several current applications, we present a comprehensive and computationally efficient theoretical model for simulating single-molecule fluorescence as it propagates through an imaging system. Furthermore, we describe how phase/amplitude-modulating optics inserted in the imaging pathway may be modeled, especially at the Fourier plane. Finally, we discuss selected recent applications of Fourier processing methods to measure the orientation, depth, and rotational mobility of single fluorescent molecules. PMID:24745862

  20. Phase Correction of Fourier Transform Ion Cyclotron Resonance Mass Spectra Using MatLab

    NASA Astrophysics Data System (ADS)

    Qi, Yulin; Thompson, Christopher J.; Van Orden, Steve L.; O'Connor, Peter B.

    2011-01-01

    FT-ICR mass spectrometry has been limited to magnitude mode for almost 40 years due to the data processing methods used. However, it is well known that phase correction of the data can theoretically produce an absorption-mode spectrum with a mass-resolving power that is as much as twice as high as conventional magnitude mode, and that it also improves the quality of the peak shape. Temporally dispersed frequency sweep excitation followed by a time delay before detection results in a steep quadratic variation in the signal phase with frequency. Viewing this, it is possible to find the correct phase function by performing a quadratic least squares fit, modified by iterating through phase cycles until the correct quadratic function is found. Here, we present a robust manual method to rotate these signals mathematically and generate a "phased" absorption-mode spectrum. The method can, in principle, be automated. Baseline correction is also included to eliminate the accompanying baseline drift. The resulting experimental FT-ICR absorption-mode spectra exhibit a resolving power that is at least 50% higher than that of the magnitude mode.

  1. Phase correction of Fourier transform ion cyclotron resonance mass spectra using MatLab.

    PubMed

    Qi, Yulin; Thompson, Christopher J; Van Orden, Steve L; O'Connor, Peter B

    2011-01-01

    FT-ICR mass spectrometry has been limited to magnitude mode for almost 40 years due to the data processing methods used. However, it is well known that phase correction of the data can theoretically produce an absorption-mode spectrum with a mass-resolving power that is as much as twice as high as conventional magnitude mode, and that it also improves the quality of the peak shape. Temporally dispersed frequency sweep excitation followed by a time delay before detection results in a steep quadratic variation in the signal phase with frequency. Viewing this, it is possible to find the correct phase function by performing a quadratic least squares fit, modified by iterating through phase cycles until the correct quadratic function is found. Here, we present a robust manual method to rotate these signals mathematically and generate a "phased" absorption-mode spectrum. The method can, in principle, be automated. Baseline correction is also included to eliminate the accompanying baseline drift. The resulting experimental FT-ICR absorption-mode spectra exhibit a resolving power that is at least 50% higher than that of the magnitude mode. PMID:21472552

  2. Microsolvation of reactive systems in the gas phase via Fourier transform microwave spectroscopy

    NASA Astrophysics Data System (ADS)

    Brauer, Carolyn Sue

    Fourier transform microwave spectroscopy has been used to study a number of reactive systems, with the primary goal of probing the effects of solvent on a molecule or a weakly bound acid-base system at the small cluster level. Because these systems are particularly sensitive to their first, nearest neighbors, the studies focus on examining structural changes and electronic rearrangement that occurs with the addition of a single solvent molecule, or microsolvent. The structural effects of microsolvation were examined on two prototypical acid-base systems. The first sought to ascertain the effect of microsolvent polarity by microsolvating HCN-SO3 with Ar and CO, forming the complexes HCN-SO3···Ar and HCN-SO 3···CO. Dipole moments and ab initio calculations also are reported. The second examined the effect of microsolvation on the primary hydrogen bond distance of (CH3)3N···HF, by adding a single HF molecule, forming the complex (CH3) 3N···HF···HF. The Stark effect was measured on a series of hydrogen halide complexes. These systems are prototypical complexes with which to study proton transfer across a hydrogen bond. The resulting dipole moments are discussed in terms of the degree of proton transfer. The dipole moment also was determined for the H2SO4···H 2O complex, which provides an important model system for understanding rates of binary homogeneous nucleation, and a series of ab initio calculations were performed in support of the results. Finally, the microwave spectrum of the radical complex OH-H2O was observed and analyzed using a two-state model which accounts for nuclear motion on the 2A' and 2A" potential surfaces. The results provide insights into the effects of the partial quenching of orbital angular momentum.

  3. Phase retrieval in in-line x-ray phase contrast imaging based on total variation

    E-print Network

    van Vliet, Lucas J.

    Phase retrieval in in-line x-ray phase contrast imaging based on total variation minimization X-ray phase-contrast imaging are aiming to solve an underdetermined linear system of equations of America OCIS codes: (110.7440) X-ray imaging; (100.5070) Phase retrieval; (100.3190) Inverse prob- lems

  4. Phase error suppression by low-pass filtering for synthetic aperture imaging ladar

    NASA Astrophysics Data System (ADS)

    Sun, Zhiwei; Hou, Peipei; Zhi, Ya'nan; Sun, Jianfeng; Zhou, Yu; Xu, Qian; Lu, Zhiyong; Liu, Liren

    2014-09-01

    Compared to synthetic aperture radar (SAR), synthetic aperture imaging ladar (SAIL) is more sensitive to the phase errors induced by atmospheric turbulence, undesirable line-of-sight translation-vibration and waveform phase error, because the light wavelength is about 3-6 orders of magnitude less than that of the radio frequency. This phase errors will deteriorate the imaging results. In this paper, an algorithm based on low-pass filtering to suppress the phase error is proposed. In this algorithm, the azimuth quadratic phase history with phase error is compensated, then the fast Fourier transform (FFT) is performed in azimuth direction, after the low-pass filtering, the inverse FFT is performed, then the image is reconstructed simultaneously in the range and azimuth direction by the two-dimensional (2D) FFT. The highfrequency phase error can be effectively eliminated hence the imaging results can be optimized by this algorithm. The mathematical analysis by virtue of data-collection equation of side-looking SAIL is presented. The theoretical modeling results are also given. In addition, based on this algorithm, a principle scheme of optical processor is proposed. The verified experiment is performed employing the data obtained from a SAIL demonstrator.

  5. Phase contrast imaging of breast tumours with synchrotron radiation

    Microsoft Academic Search

    A. Olivo; L. Rigon; S. J. Vinnicombe; K. C. Cheung; M. Ibison; R. D. Speller

    2009-01-01

    Even though the potential of phase contrast (PC) imaging has been demonstrated in a number of biological tissue samples, the availability of free-space propagation phase contrast images of real breast tumours is still limited. The aim of this study was to obtain phase contrast images of two different pathological breast specimens containing tumours of differing morphological type at two synchrotron

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

    PubMed

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

    2008-09-15

    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 approximately 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 approximately 8 - 9 micron axial resolution at 250,000 axial scans per second, a 512 x 512 x 400 voxel volumetric 3D-OCT data set can be acquired in only approximately 1.3 seconds. Orthogonal registration scans are used to register OCT raster scans and remove residual axial eye motion, resulting in 3D-OCT data sets which preserve retinal topography. Rapid repetitive imaging over small volumes can visualize small retinal features without motion induced distortions and enables volume registration to remove eye motion. Cone photoreceptors in some regions of the retina can be visualized without adaptive optics or active eye tracking. Rapid repetitive imaging of 3D volumes also provides dynamic volumetric information (4D-OCT) which is shown to enhance visualization of retinal capillaries and should enable functional imaging. Improvements in the speed and performance of 3D-OCT volumetric imaging promise to enable earlier diagnosis and improved monitoring of disease progression and response to therapy in ophthalmology, as well as have a wide range of research and clinical applications in other areas. PMID:18795054

  7. In situ permeation study of drug through the stratum corneum using attenuated total reflection Fourier transform infrared spectroscopic imaging

    NASA Astrophysics Data System (ADS)

    Andanson, Jean-Michel; Hadgraft, Jonathan; Kazarian, Sergei G.

    2009-05-01

    Infrared (IR) spectroscopy is one of the most chemically specific analytical methods that gives information about composition, structure, and interactions in a material. IR spectroscopy has been successfully applied to study the permeation of xenobiotics through the skin. Combining IR spectroscopy with an IR array detector led to the development of Fourier transform infrared (FTIR) spectroscopic imaging, which generates chemical information from different areas of a sample at the microscopic level. This is particularly important for heterogeneous samples, such as skin. Attenuated total reflection (ATR)-FTIR imaging has been applied to measure, in situ, the diffusion of benzyl nicotinate (BN) through the outer layer of human skin [stratum corneum (SC)]. In vitro experiments have demonstrated the heterogeneous distribution of SC surface lipids before the penetration of a saturated solution of BN. Image analysis demonstrated a strong correlation between the distribution of lipids and drugs, while ethanol appeared to be homogenously distributed in the SC. These results show the ability of ATR-FTIR imaging to measure simultaneously the affinities of drug and solvent to the lipid-rich and lipid-poor skin domains, respectively, during permeation. This information may be useful in better understanding drug-diffusion pathways through the SC.

  8. Droplet characteristic measurement in Fourier interferometry imaging and behavior at the rainbow angle.

    PubMed

    Briard, Paul; Saengkaew, Sawitree; Wu, Xuecheng; Meunier-Guttin-Cluzel, Siegfried; Chen, Linghong; Cen, Kefa; Gréhan, Gérard

    2013-01-01

    This paper presents the possibility of measuring the three-dimensional (3D) relative locations and diameters of a set of spherical particles and discusses the behavior of the light recorded around the rainbow angle, an essential step toward refractive index measurements. When a set of particles is illuminated by a pulsed incident wave, the particles act as spherical light wave sources. When the pulse duration is short enough to fix the particle location (typically about 10 ns), interference fringes between these different spherical waves can be recorded. The Fourier transform of the fringes divides the complex fringe systems into a series of spots, with each spot characterizing the interference between a pair of particles. The analyses of these spots (in position and shape) potentially allow the measurement of particle characteristics (3D relative position, particle diameter, and particle refractive index value). PMID:23292412

  9. A Fourier-based method for the restoration of chopped and nodded images

    Microsoft Academic Search

    M. Bertero; P. Boccacci; A. Custo; C. De Mol; M. Robberto

    2003-01-01

    In a series of previous papers we have proposed and validated an iterative method, known as the projected Landweber method, for the restoration of astronomical images taken in chopping and nodding mode. While the method generally provides good results, it may also generate artifacts related to the huge non-uniqueness of the solution of the restoration problem. If the image satisfies

  10. Classification of Carpiodes Using Fourier Descriptors: A Content Based Image Retrieval Approach

    Microsoft Academic Search

    Patrick Trahan

    2009-01-01

    Taxonomic classification has always been important to the study of any biological system. Many biological species will go unclassified and become lost forever at the current rate of classification. The current state of computer technology makes image storage and retrieval possible on a global level. As a result, computer-aided taxonomy is now possible. Content based image retrieval techniques utilize visual

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

    Microsoft Academic Search

    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

    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

  12. High-Spatial- and High-Temporal-Resolution Dynamic Contrast-enhanced MR Breast Imaging with Sweep Imaging with Fourier Transformation: A Pilot Study.

    PubMed

    Corum, Curtis A; Benson, John C; Idiyatullin, Djaudat; Snyder, Angela L; Snyder, Carl J; Hutter, Diane; Everson, Lenore I; Eberly, Lynn E; Nelson, Michael T; Garwood, Michael

    2015-02-01

    Purpose To report the results of sweep imaging with Fourier transformation (SWIFT) magnetic resonance (MR) imaging for diagnostic breast imaging. Materials and Methods Informed consent was obtained from all participants under one of two institutional review board-approved, HIPAA-compliant protocols. Twelve female patients (age range, 19-54 years; mean age, 41.2 years) and eight normal control subjects (age range, 22-56 years; mean age, 43.2 years) enrolled and completed the study from January 28, 2011, to March 5, 2013. Patients had previous lesions that were Breast Imaging Reporting and Data System 4 and 5 based on mammography and/or ultrasonographic imaging. Contrast-enhanced SWIFT imaging was completed by using a 4-T research MR imaging system. Noncontrast studies were completed in the normal control subjects. One of two sized single-breast SWIFT-compatible transceiver coils was used for nine patients and five controls. Three patients and five control subjects used a SWIFT-compatible dual breast coil. Temporal resolution was 5.9-7.5 seconds. Spatial resolution was 1.00 mm isotropic, with later examinations at 0.67 mm isotropic, and dual breast at 1.00 mm or 0.75 mm isotropic resolution. Results Two nonblinded breast radiologists reported SWIFT image findings of normal breast tissue, benign fibroadenomas (six of six lesions), and malignant lesions (10 of 12 lesions) concordant with other imaging modalities and pathologic reports. Two lesions in two patients were not visualized because of coil field of view. The images yielded by SWIFT showed the presence and extent of known breast lesions. Conclusion The SWIFT technique could become an important addition to breast imaging modalities because it provides high spatial resolution at all points during the dynamic contrast-enhanced examination. © RSNA, 2014. PMID:25247405

  13. Subcellular Biochemical Investigation of Purkinje Neurons Using Synchrotron Radiation Fourier Transform Infrared Spectroscopic Imaging with a Focal Plane Array Detector

    PubMed Central

    2013-01-01

    Coupling Fourier transform infrared spectroscopy with focal plane array detectors at synchrotron radiation sources (SR-FTIR-FPA) has provided a rapid method to simultaneously image numerous biochemical markers in situ at diffraction limited resolution. Since cells and nuclei are well resolved at this spatial resolution, a direct comparison can be made between FTIR functional group images and the histology of the same section. To allow histological analysis of the same section analyzed with infrared imaging, unfixed air-dried tissue sections are typically fixed (after infrared spectroscopic analysis is completed) via immersion fixation. This post fixation process is essential to allow histological staining of the tissue section. Although immersion fixation is a common practice in this filed, the initial rehydration of the dehydrated unfixed tissue can result in distortion of subcellular morphology and confound correlation between infrared images and histology. In this study, vapor fixation, a common choice in other research fields where postfixation of unfixed tissue sections is required, was employed in place of immersion fixation post spectroscopic analysis. This method provided more accurate histology with reduced distortions as the dehydrated tissue section is fixed in vapor rather than during rehydration in an aqueous fixation medium. With this approach, accurate correlation between infrared images and histology of the same section revealed that Purkinje neurons in the cerebellum are rich in cytosolic proteins and not depleted as once thought. In addition, we provide the first direct evidence of intracellular lactate within Purkinje neurons. This highlights the significant potential for future applications of SR-FTIR-FPA imaging to investigate cellular lactate under conditions of altered metabolic demand such as increased brain activity and hypoxia or ischemia. PMID:23638613

  14. Proteoglycan concentrations in healthy and diseased articular cartilage by Fourier transform infrared imaging and principal component regression

    NASA Astrophysics Data System (ADS)

    Yin, Jianhua; Xia, Yang

    2014-12-01

    Fourier transform infrared imaging (FTIRI) combining with principal component regression (PCR) analysis were used to determine the reduction of proteoglycan (PG) in articular cartilage after the transection of the anterior cruciate ligament (ACL). A number of canine knee cartilage sections were harvested from the meniscus-covered and meniscus-uncovered medial tibial locations from the control joints, the ACL joints at three time points after the surgery, and their contralateral joints. The PG loss in the ACL cartilage was related positively to the durations after the surgery. The PG loss in the contralateral knees was less than that of the ACL knees. The PG loss in the meniscus-covered cartilage was less than that of the meniscus-uncovered tissue in both ACL and contralateral knees. The quantitative mapping of PG loss could monitor the disease progression and repair processes in arthritis.

  15. Fourier optical cryptosystem using complex spatial modulation

    NASA Astrophysics Data System (ADS)

    Sarkadi, T.; Koppa, P.

    2014-09-01

    Our goal is to enhance the security level of a Fourier optical encryption system. Therefore we propose a Mach–Zehnder interferometer based encryption setup. The input data is organized in a binary array, and it is encoded in the two wave fronts propagated in the arms of the interferometer. Both input wave fronts are independently encrypted by Fourier systems, hence the proposed method has two encryption keys. During decryption, the encrypted wave fronts are propagated through the interferometer setup. The interference pattern of the output shows the reconstructed data in cases where the correct decryption Fourier keys are used. We propose a novel input image modulation method with a user defined phase parameter. We show that the security level of the proposed cryptosystem can be enhanced by an optimally chosen phase parameter.

  16. Phased Array Feed Calibration, Beamforming and Imaging

    E-print Network

    Landon, Jonathan; Waldron, Jacob; Jones, David; Stemmons, Alan; Jeffs, Brian D; Warnick, Karl F; Fisher, J Richard; Norrod, Roger D

    2009-01-01

    Phased array feeds (PAFs) for reflector antennas offer the potential for increased reflector field of view and faster survey speeds. To address some of the development challenges that remain for scientifically useful PAFs, including calibration and beamforming algorithms, sensitivity optimization, and demonstration of wide field of view imaging, we report experimental results from a 19 element room temperature L-band PAF mounted on the Green Bank 20-Meter Telescope. Formed beams achieved an aperture efficiency of 69% and system noise temperature of 66 K. Radio camera images of several sky regions are presented. We investigate the noise performance and sensitivity of the system as a function of elevation angle with statistically optimal beamforming and demonstrate cancelation of radio frequency interference sources with adaptive spatial filtering.

  17. PHASED ARRAY FEED CALIBRATION, BEAMFORMING, AND IMAGING

    SciTech Connect

    Landon, Jonathan; Elmer, Michael; Waldron, Jacob; Jones, David; Stemmons, Alan; Jeffs, Brian D.; Warnick, Karl F. [Department of Electrical and Computer Engineering, Brigham Young University, 459 Clyde Building, Provo, UT 84602 (United States); Richard Fisher, J. [National Radio Astronomy Observatory, Charlottesville, VA (United States); Norrod, Roger D. [National Radio Astronomy Observatory, Green Bank, WV (United States)

    2010-03-15

    Phased array feeds (PAFs) for reflector antennas offer the potential for increased reflector field of view and faster survey speeds. To address some of the development challenges that remain for scientifically useful PAFs, including calibration and beamforming algorithms, sensitivity optimization, and demonstration of wide field of view imaging, we report experimental results from a 19 element room temperature L-band PAF mounted on the Green Bank 20 Meter Telescope. Formed beams achieved an aperture efficiency of 69% and a system noise temperature of 66 K. Radio camera images of several sky regions are presented. We investigate the noise performance and sensitivity of the system as a function of elevation angle with statistically optimal beamforming and demonstrate cancelation of radio frequency interference sources with adaptive spatial filtering.

  18. Encrypted imaging based on algebraic implementation of double random phase encoding.

    PubMed

    Nakano, Kazuya; Takeda, Masafumi; Suzuki, Hiroyuki; Yamaguchi, Masahiro

    2014-05-10

    The security of important information captured by sensors and cameras is currently a growing concern as information theft via techniques such as side-channel attacks become increasingly more prevalent. Double random phase encoding (DRPE) is an optical encryption method based on optical Fourier transform that is currently being used to implement secure coherent optical systems. In this paper, we propose a new DRPE implementation for incoherent optical systems based on integral photography that can be applied to "encrypted imaging (EI)" to optically encrypt an image before it is captured by an image sensor. Because the proposed incoherent DRPE is constituted from conventional DRPE by rewriting the optical encryption via discretization and Euler's formula, its security level is the same as that of conventional DRPE. The results of an experiment in which we encrypted a plaintext image optically and then decrypted it numerically demonstrate that our proposed incoherent optical security system is feasible. PMID:24922013

  19. Concentration determination of collagen and proteoglycan in bovine nasal cartilage by Fourier transform infrared imaging and PLS

    NASA Astrophysics Data System (ADS)

    Zhang, Xuexi; Xiao, Zhi-Yan; Yin, Jianhua; Xia, Yang

    2014-09-01

    Fourier transform infrared imaging (FTIRI) combined with chemometrics can be used to detect the structure of bio-macromolecule, measure the concentrations of some components, and so on. In this study, FTIRI with Partial Least-Squares (PLS) regression was applied to study the concentration of two main components in bovine nasal cartilage (BNC), collagen and proteoglycan. An infrared spectrum library was built by mixing the collagen and chondroitin 6-sulfate (main of proteoglycan) at different ratios. Some pretreatments are needed for building PLS model. FTIR images were collected from BNC sections at 6.25?m and 25?m pixel size. The spectra extracted from BNC-FTIR images were imported into the PLS regression program to predict the concentrations of collagen and proteoglycan. These PLS-determined concentrations are agreed with the result in our previous work and biochemical analytical results. The prediction shows that the concentrations of collagen and proteoglycan in BNC are comparative on the whole. However, the concentration of proteoglycan is a litter higher than that of collagen, to some extent.

  20. Ground-Based Measurement Experiment and First Results with Geosynchronous-Imaging Fourier Transform Spectrometer Engineering Demonstration Unit

    NASA Technical Reports Server (NTRS)

    Zhou, Daniel K.; Smith, William L.; Bingham, Gail E.; Huppi, Ronald J.; Revercomb, Henry E.; Zollinger, Lori J.; Larar, Allen M.; Liu, Xu; Tansock, Joseph J.; Reisse, Robert A.; Hooker, Ronald

    2007-01-01

    The geosynchronous-imaging Fourier transform spectrometer (GIFTS) engineering demonstration unit (EDU) is an imaging infrared spectrometer designed for atmospheric soundings. It measures the infrared spectrum in two spectral bands (14.6 to 8.8 microns, 6.0 to 4.4 microns) using two 128 x 128 detector arrays with a spectral resolution of 0.57 cm(exp -1) with a scan duration of approximately 11 seconds. From a geosynchronous orbit, the instrument will have the capability of taking successive measurements of such data to scan desired regions of the globe, from which atmospheric status, cloud parameters, wind field profiles, and other derived products can be retrieved. The GIFTS EDU provides a flexible and accurate testbed for the new challenges of the emerging hyperspectral era. The EDU ground-based measurement experiment, held in Logan, Utah during September 2006, demonstrated its extensive capabilities and potential for geosynchronous and other applications (e.g., Earth observing environmental measurements). This paper addresses the experiment objectives and overall performance of the sensor system with a focus on the GIFTS EDU imaging capability and proof of the GIFTS measurement concept.

  1. Testing results and current status of FTS-2, an imaging Fourier transform spectrometer for SCUBA-2

    E-print Network

    Naylor, David A.

    -Zehnder imaging spectrometer, built for use with the SCUBA-2 camera on the James Clerk Maxwell Telescope (JCMT (FTS) which has been built for use with the SCUBA-2 camera1 on the James Clerk Maxwell Telescope (JCMT

  2. Quantitative Fourier Domain Optical Coherence Tomography Imaging of the Ocular Anterior Segment

    NASA Astrophysics Data System (ADS)

    McNabb, Ryan Palmer

    Clinical imaging within ophthalmology has had transformative effects on ocular health over the last century. Imaging has guided clinicians in their pharmaceutical and surgical treatments of macular degeneration, glaucoma, cataracts and numerous other pathologies. Many of the imaging techniques currently used are photography based and are limited to imaging the surface of ocular structures. This limitation forces clinicians to make assumptions about the underlying tissue which may reduce the efficacy of their diagnoses. Optical coherence tomography (OCT) is a non-invasive, non-ionizing imaging modality that has been widely adopted within the field of ophthalmology in the last 15 years. As an optical imaging technique, OCT utilizes low-coherence interferometry to produce micron-scale three-dimensional datasets of a tissue's structure. Much of the human body consists of tissues that significantly scatter and attenuate optical signals limiting the imaging depth of OCT in those tissues to only 1-2mm. However, the ocular anterior segment is unique among human tissue in that it is primarily transparent or translucent. This allows for relatively deep imaging of tissue structure with OCT and is no longer limited by the optical scattering properties of the tissue. This goal of this work is to develop methods utilizing OCT that offer the potential to reduce the assumptions made by clinicians in their evaluations of their patients' ocular anterior segments. We achieved this by first developing a method to reduce the effects of patient motion during OCT volume acquisitions allowing for accurate, three dimensional measurements of corneal shape. Having accurate corneal shape measurements then allowed us to determine corneal spherical and astigmatic refractive contribution in a given individual. This was then validated in a clinical study that showed OCT better measured refractive change due to surgery than other clinical devices. Additionally, a method was developed to combine the clinical evaluation of the iridocorneal angle through gonioscopy with OCT.

  3. Anisotropic cross talk in an optical interconnection by using a self-pumped phase-conjugate mirror at the Fourier plane

    NASA Astrophysics Data System (ADS)

    Chiou, Arthur

    1992-07-01

    Experimental evidence is presented that, in an optical interconnection using self-pumped phase-conjugate mirror (SPPCM) at the Fourier plane, there is drastic difference between the cross talk in the horizontal direction and the vertical direction. The cross talk that is due to Bragg degeneracy of the multiplexed volume holograms in a SPPCM is reduced along the horizontal direction, but not in the vertical direction. A physical explanation for this observation is given, and it is suggested that similar anisotropic behavior can be expected in other anisotropic properties of Fourier-transformed volume holograms under broad conditions.

  4. Simple merging technique for improving resolution in qualitative single image phase contrast tomography.

    PubMed

    Irvine, S; Mokso, R; Modregger, P; Wang, Z; Marone, F; Stampanoni, M

    2014-11-01

    For dynamic samples and/or for simple ease-of-use experiments, single-image phase contrast tomography is a very effective method for the 3D visualization of materials which would otherwise be indiscernible in attenuation based x-ray imaging. With binary samples (e.g. air-material) and monochromatic wavefields a transport-of-intensity (TIE)-based phase retrieval algorithm is known to retrieve accurate quantitative maps of the phase distribution. For mixed material samples and/or white beam radiation the algorithm can still produce useful qualitative tomographic reconstructions with significantly improved area contrast. The stability of the algorithm comes with a recognized associated loss of spatial resolution due to its essential behaviour as a low-pass filter. One possible answer to this is an image fusion technique that merges the slices reconstructed from raw phase contrast images and those after phase retrieval, where the improved contrast may be acquired without the associated loss of high-frequency information. We present this technique as a simple few-parameter Fourier method, which is easily tunable and highly compatible with current reconstruction steps. PMID:25401876

  5. An optimised framework for reconstructing and processing MR phase images

    Microsoft Academic Search

    Zhaolin Chen; Leigh A. Johnston; Dae Hyuk Kwon; Se Hong Oh; Zang-Hee Cho; Gary F. Egan

    2010-01-01

    Phase contrast imaging holds great potential for in vivo biodistribution studies of paramagnetic molecules and materials. However, in vivo quantification of iron storage and other paramagnetic materials requires improvements in reconstruction and processing of MR complex images. To achieve this, we have developed a framework including (i) an optimal coil sensitivity smoothing filter for phase imaging determined at the maximal

  6. Acoustically modulated x-ray phase contrast imaging.

    PubMed

    Hamilton, Theron J; Bailat, Claude J; Rose-Petruck, Christoph; Diebold, Gerald J

    2004-11-01

    We report the use of ultrasonic radiation pressure with phase contrast x-ray imaging to give an image proportional to the space derivative of a conventional phase contrast image in the direction of propagation of an ultrasonic beam. Intense ultrasound is used to exert forces on objects within a body giving displacements of the order of tens to hundreds of microns. Subtraction of images made with and without the ultrasound field gives an image that removes low spatial frequency features and highlights high frequency features. The method acts as an acoustic 'contrast agent' for phase contrast x-ray imaging, which in soft tissue acts to highlight small density changes. PMID:15584532

  7. Ultrahigh Speed Imaging of the Rat Retina Using Ultrahigh Resolution Spectral/Fourier Domain OCT

    E-print Network

    Liu, Jonathan Jaoshin

    We performed OCT imaging of the rat retina at 70,000 axial scans per second with ~3 ?m axial resolution. Three-dimensional OCT (3D-OCT) data sets of the rat retina were acquired. The high speed and high density data sets ...

  8. Fourier domain design of microgrid imaging polarimeters with improved spatial resolution

    NASA Astrophysics Data System (ADS)

    Hirakawa, Keigo; LeMaster, Daniel A.

    2014-05-01

    Microgrid polarimetric imagers sacrifice spatial resolution for sensitivity to states of linear polarization. We have recently shown that a 2 × 4 microgrid analyzer pattern sacrifices less spatial resolution than the conventional 2× 2 case without compromising polarization sensitivity. In this paper, we discuss the design strategy that uncovered the spatial resolution benefits of the 2 × 4 array.

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

    Microsoft Academic Search

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

    2008-01-01

    The ultimate remote sensing benefits of the high resolution Infrared radiance spectrometers will be realized with their geostationary satellite implementation in the form of imaging spectrometers. This will enable dynamic features of the atmosphere's thermodynamic fields and pollutant and greenhouse gas constituents to be observed for revolutionary improvements in weather forecasts and more accurate air quality and climate predictions. As

  10. Quantitative phase imaging using actively stabilized phase-shifting low-coherence interferometry.

    PubMed

    Iwai, Hidenao; Fang-Yen, Christopher; Popescu, Gabriel; Wax, Adam; Badizadegan, Kamran; Dasari, Ramachandra R; Feld, Michael S

    2004-10-15

    We describe a quantitative phase-imaging interferometer in which phase shifting and noise cancellation are performed by an active feedback loop using a reference laser. Depth gating via low-coherence light allows phase measurement from weakly reflecting biological samples. We demonstrate phase images from a test structure and living cells. PMID:15532280

  11. Imaging retinal degeneration in mice by combining Fourier domain optical coherence tomography and fluorescent scanning laser ophthalmoscopy

    NASA Astrophysics Data System (ADS)

    Hossein-Javaheri, Nima; Molday, Laurie L.; Xu, Jing; Molday, Robert S.; Sarunic, Marinko V.

    2009-02-01

    Visualization of the internal structures of the retina is critical for clinical diagnosis and monitoring of pathology as well as for medical research investigating the root causes of retinal degeneration. Optical Coherence Tomography (OCT) is emerging as the preferred technique for non-contact sub-surface depth-resolved imaging of the retina. The high resolution cross sectional images acquired in vivo by OCT can be compared to histology to visually delineate the retinal layers. The recent demonstration of the significant sensitivity increase obtained through use of Fourier domain (FD) detection with OCT has been used to facilitate high speed scanning for volumetric reconstruction of the retina in software. The images acquired by OCT are purely structural, relying on refractive index differences in the tissue for contrast, and do not provide information on the molecular content of the sample. We have constructed a FDOCT prototype and combined it with a fluorescent Scanning Laser Ophthalmoscope (fSLO) to permit real time alignment of the field of view on the retina. The alignment of the FDOCT system to the specimen is crucial for the registration of measurements taken throughout longitudinal studies. In addition, fluorescence detection has been integrated with the SLO to enable the en face localization of a molecular contrast signal, which is important for retinal angiography, and also for detection of autofluorescence associated with some forms of retinal degeneration, for example autofluorescence lipofuscin accumulations are associated with Stargardt's Macular Dystrophy. The integrated FD OCT/fSLO system was investigated for imaging the retina of the mice in vivo.

  12. Phase Sensitive X-Ray Imaging: Towards its Interdisciplinary Applications

    Microsoft Academic Search

    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

    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

  13. Phase Retrieval Using a Genetic Algorithm on the Systematic Image-Based Optical Alignment Testbed

    NASA Technical Reports Server (NTRS)

    Taylor, Jaime R.

    2003-01-01

    NASA s Marshall Space Flight Center s Systematic Image-Based Optical Alignment (SIBOA) Testbed was developed to test phase retrieval algorithms and hardware techniques. Individuals working with the facility developed the idea of implementing phase retrieval by breaking the determination of the tip/tilt of each mirror apart from the piston motion (or translation) of each mirror. Presented in this report is an algorithm that determines the optimal phase correction associated only with the piston motion of the mirrors. A description of the Phase Retrieval problem is first presented. The Systematic Image-Based Optical Alignment (SIBOA) Testbeb is then described. A Discrete Fourier Transform (DFT) is necessary to transfer the incoming wavefront (or estimate of phase error) into the spatial frequency domain to compare it with the image. A method for reducing the DFT to seven scalar/matrix multiplications is presented. A genetic algorithm is then used to search for the phase error. The results of this new algorithm on a test problem are presented.

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

    NASA Technical Reports Server (NTRS)

    Dennis, Brian R.; Crannell, Carol JO; Desai, Upendra D.; Orwig, Larry E.; Kiplinger, Alan L.; Schwartz, Richard A.; Hurford, Gordon J.; Emslie, A. Gordon; Machado, Marcos; Wood, Kent

    1988-01-01

    The Fourier Imaging X-ray Spectrometer (FIXS) is one of four instruments on SAC-1, the Argentinian satellite being proposed for launch by NASA on a Scout rocket in 1992/3. The FIXS is designed to provide solar flare images at X-ray energies between 5 and 35 keV. Observations will be made on arcsecond size scales and subsecond time scales of the processes that modify the electron spectrum and the thermal distribution in flaring magnetic structures.

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

    NASA Astrophysics Data System (ADS)

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

    2011-12-01

    Particles in the atmosphere influence visibility, climate, and human health. Secondary organic aerosols (SOA) formed from chemical reactions in the atmosphere constitute a portion of total organic particle mass. Most research on SOA has focused on gas phase reactions; however, reactions taking place in cloud and fog drops may be significant. One group of water-soluble compounds that participate in these reactions is phenols. Phenols, emitted from biomass burning, react in the aqueous phase to form low-volatility SOA products. The products formed from these reactions are currently poorly characterized. In order to characterize laboratory-generated samples, we are developing an attenuated total reflectance-Fourier transform infrared spectroscopic (ATR-FTIR) technique to identify and quantify organic functional groups in SOA. Aqueous SOA is made in the laboratory by illuminating solutions of phenolic compounds with an oxidant. The illuminated solution is then blown to dryness in order to determine the mass of SOA produced. The dry SOA is reconstituted in water and drops of this solution are placed onto a single-reflection ATR accessory. In order to identify and quantify functional groups in the complex SOA samples, it is necessary to calibrate with compounds and mixtures of compounds containing bond types similar to those found in the laboratory-generated SOA. Initially, focus has been placed on multiple peaks located in the region between 1800 cm-1 and 800 cm-1, including peaks for C=O and C-O. We distinguish between characteristic absorbances to begin determining the organic functional group composition of the SOA samples. This ATR-FTIR technique complements information from mass spectrometry measurements and allows us to quantify organic mass for non-volatile SOA products.

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

    PubMed Central

    Aizikov, Konstantin; Smith, Donald F.; Chargin, David A.; Ivanov, Sergei; Lin, Tzu-Yung; Heeren, Ron M. A.; O’Connor, Peter B.

    2011-01-01

    The high mass accuracy and resolving power of Fourier transform ion cyclotron resonance mass spectrometers (FT-ICR MS) make them ideal mass detectors for mass spectrometry imaging (MSI), promising to provide unmatched molecular resolution capabilities. The intrinsic low tolerance of FT-ICR MS to RF interference, however, along with typically vertical positioning of the sample, and MSI acquisition speed requirements present numerous engineering challenges in creating robotics capable of achieving the spatial resolution to match. This work discusses a two-dimensional positioning stage designed to address these issues. The stage is capable of operating in ?1 × 10–8 mbar vacuum. The range of motion is set to 100 mm × 100 mm to accommodate large samples, while the positioning accuracy is demonstrated to be less than 0.4 micron in both directions under vertical load over the entire range. This device was integrated into three different matrix assisted laser desorption/ionization (MALDI) FT-ICR instruments and showed no detectable RF noise. The “oversampling” MALDI-MSI experiments, under which the sample is completely ablated at each position, followed by the target movement of the distance smaller than the laser beam, conducted on the custom-built 7T FT-ICR MS demonstrate the stability and positional accuracy of the stage robotics which delivers high spatial resolution mass spectral images at a fraction of the laser spot diameter. PMID:21639522

  17. Investigating the biochemical progression of liver disease through fibrosis, cirrhosis, dysplasia, and hepatocellular carcinoma using Fourier transform infrared spectroscopic imaging

    NASA Astrophysics Data System (ADS)

    Sreedhar, Hari; Pant, Mamta; Ronquillo, Nemencio R.; Davidson, Bennett; Nguyen, Peter; Chennuri, Rohini; Choi, Jacqueline; Herrera, Joaquin A.; Hinojosa, Ana C.; Jin, Ming; Kajdacsy-Balla, Andre; Guzman, Grace; Walsh, Michael J.

    2014-03-01

    Hepatocellular carcinoma (HCC) is the most common form of primary hepatic carcinoma. HCC ranks the fourth most prevalent malignant tumor and the third leading cause of cancer related death in the world. Hepatocellular carcinoma develops in the context of chronic liver disease and its evolution is characterized by progression through intermediate stages to advanced disease and possibly even death. The primary sequence of hepatocarcinogenesis includes the development of cirrhosis, followed by dysplasia, and hepatocellular carcinoma.1 We addressed the utility of Fourier Transform Infrared (FT-IR) spectroscopic imaging, both as a diagnostic tool of the different stages of the disease and to gain insight into the biochemical process associated with disease progression. Tissue microarrays were obtained from the University of Illinois at Chicago tissue bank consisting of liver explants from 12 transplant patients. Tissue core biopsies were obtained from each explant targeting regions of normal, liver cell dysplasia including large cell change and small cell change, and hepatocellular carcinoma. We obtained FT-IR images of these tissues using a modified FT-IR system with high definition capabilities. Firstly, a supervised spectral classifier was built to discriminate between normal and cancerous hepatocytes. Secondly, an expanded classifier was built to discriminate small cell and large cell changes in liver disease. With the emerging advances in FT-IR instrumentation and computation there is a strong drive to develop this technology as a powerful adjunct to current histopathology approaches to improve disease diagnosis and prognosis.

  18. Quantitative assessment of effects of phase aberration and noise on high-frame-rate imaging.

    PubMed

    Chen, Hong; Lu, Jian-yu

    2013-01-01

    The goal of this paper is to quantitatively study effects of phase aberration and noise on high-frame-rate (HFR) imaging using a set of traditional and new parameters. These parameters include the traditional -6-dB lateral resolution, and new parameters called the energy ratio (ER) and the sidelobe ratio (SR). ER is the ratio between the total energy of sidelobe and the total energy of mainlobe of a point spread function (PSF) of an imaging system. SR is the ratio between the peak value of the sidelobe and the peak value of the mainlobe of the PSF. In the paper, both simulation and experiment are conducted for a quantitative assessment and comparison of the effects of phase aberration and noise on the HFR and the conventional delay-and-sum (D&S) imaging methods with the set of parameters. In the HFR imaging method, steered plane waves (SPWs) and limited-diffraction beams (LDBs) are used in transmission, and received signals are processed with the Fast Fourier Transform to reconstruct images. In the D&S imaging method, beams focused at a fixed depth are used in transmission and dynamically focused beams are used in reception for image reconstruction. The simulation results show that the average differences between the -6-dB lateral beam widths of the HFR imaging and the D&S imaging methods are -0.1337mm for SPW and -0.1481mm for LDB, which means that the HFR imaging method has a higher lateral image resolution than the D&S imaging method since the values are negative. In experiments, the average differences are also negative, i.e., -0.2804mm for SPW and -0.3365mm for LDB. The results for the changes of ER and SR between the HFR and the D&S imaging methods have negative values, too. After introducing phase aberration and noise, both simulations and experiments show that the HFR imaging method has also less change in the -6-dB lateral resolution, ER, and SR as compared to the conventional D&S imaging method. This means that the HFR imaging method is less sensitive to the phase aberration and noise. Based on the study of the new parameters on the HFR and the D&S imaging methods, it is expected that the new parameters can also be applied to assess quality of other imaging methods. PMID:22546551

  19. Optical image hiding using double-phase retrieval algorithm based on nonlinear cryptosystem under vortex beam illumination

    NASA Astrophysics Data System (ADS)

    Wang, Xiaogang; Chen, Wen; Chen, Xudong

    2015-03-01

    We propose a novel optical image hiding method based on a double-phase retrieval algorithm (DPRA) using iterative nonlinear double random phase encoding (NDRPE) in Fresnel domain under illumination of an optical vortex (OV) beam. The NDRPE-based DPRA is initially extended from the Fourier transform into the Fresnel domain, which makes the system more flexible and more compact. The proposed method has a faster convergence speed compared to its counterparts based on the linear double random phase encoding (LDRPE). A higher level of security also has been achieved by taking an OV mode as the illumination beam. Simulation results demonstrate the feasibility and security of the proposed approach.

  20. Application of a Fourier-transform infrared imaging system to deciphering obliterated writings for forensic purposes

    NASA Astrophysics Data System (ADS)

    Sugawara, Shigeru

    2014-05-01

    A new method of deciphering obliterated writing is proposed in this paper. Inks with a peak at 1620 cm-1 were used for writing characters on paper, and information protection stamps were then used to obliterate them. Conventional detection methods consisting of visible and near-infrared spectroscopic photography and fluorescent photography of wavelength between 0.4-1.0 ?m were compared with a novel method using infrared spectroscopic imaging with a 16-element mercury cadmium telluride array detector. The samples of obliterated writing could not be detected by the conventional methods, but could by the new method. Therefore, this new method is very useful for deciphering obliterated writing.

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

    NASA Astrophysics Data System (ADS)

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

    2003-10-01

    Dual excitation fluorescence imaging has been used as a first step towards multi-wavelength excitation/emission fluorescence spectral imaging. Target cells are transformed keratinocytes, and other osteosarcoma, human breast and color cancer cells. Mitochondrial membrane potential probes, e.g. TMRM (tetramethylrhodamine methyl ester), Mitotracker Green (Molecular Probes, Inc., Eugene OR,USA; a recently synthesized mitochondrial oxygen probe, [PRE,P1"- pyrene butyl)-2-rhodamine ester] allow dual excitation in the UV plus in teh blue-green spectral regions. Also, using the natural endogenous probe NAD(P)H, preliminary results indicate mitochondrial responses to metabolic challenges (e.g. glucose addition), plus changes in mitochonrial distribution and morphology. In terms of application to biomedicine (for diagnostiscs, prognostsics and drug trials) three parameters have been selected in addition to the natural probe NAD(P)H, i.e. vital fluorescence probing of mitochondria, lysosomes and Golgi apparatus. It is hoped that such a multiparameter approach will allow malignant cell characterization and grading. A new area being introduced is the use of similar methodology for biotechnical applications such as the study of the hydrogen-producing alga Chlamydomonas Reinhardtii, and possible agricultural applications, such as Saccharomyces yeast for oenology. Complementation by Photoacoustic Microscopy is also contemplated, to study the internal conversion component which follows the excitation by photons.

  2. Color image encryption based on color blend and chaos permutation in the reality-preserving multiple-parameter fractional Fourier transform domain

    NASA Astrophysics Data System (ADS)

    Lang, Jun

    2015-03-01

    In this paper, we propose a novel color image encryption method by using Color Blend (CB) and Chaos Permutation (CP) operations in the reality-preserving multiple-parameter fractional Fourier transform (RPMPFRFT) domain. The original color image is first exchanged and mixed randomly from the standard red-green-blue (RGB) color space to R?G?B? color space by rotating the color cube with a random angle matrix. Then RPMPFRFT is employed for changing the pixel values of color image, three components of the scrambled RGB color space are converted by RPMPFRFT with three different transform pairs, respectively. Comparing to the complex output transform, the RPMPFRFT transform ensures that the output is real which can save storage space of image and convenient for transmission in practical applications. To further enhance the security of the encryption system, the output of the former steps is scrambled by juxtaposition of sections of the image in the reality-preserving multiple-parameter fractional Fourier domains and the alignment of sections is determined by two coupled chaotic logistic maps. The parameters in the Color Blend, Chaos Permutation and the RPMPFRFT transform are regarded as the key in the encryption algorithm. The proposed color image encryption can also be applied to encrypt three gray images by transforming the gray images into three RGB color components of a specially constructed color image. Numerical simulations are performed to demonstrate that the proposed algorithm is feasible, secure, sensitive to keys and robust to noise attack and data loss.

  3. Quantitative evaluation of phase processing approaches in susceptibility weighted imaging

    NASA Astrophysics Data System (ADS)

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

    2012-03-01

    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.

  4. [Fundus images mosaicking based on edge extended phase correlation].

    PubMed

    Cui, Dong; Liu, Minmin; Zhang, Guangyu; Jiao, Qing; Chen, Di; Guo, Yongxin

    2013-05-01

    With regard to the large amount of calculation in image mosaic algorithm, an image mosaic algorithm based on extended phase correlation of edge is presented. The improved wavelet edge detection algorithm is to detect edge of blood vessels. Then the image translation, rotation and scale changes are calculated by the extended phase correlation method. These parameters are utilized to stitch images. Finally, image fusion can be achieved by fade-in-fade-out method. It is proved by experiments that this algorithm is simple to calculate, and can effectively achieve the image mosaic. PMID:24015605

  5. Analytic versus adaptive image formation using optical phased arrays

    NASA Astrophysics Data System (ADS)

    Kendrick, Rick; Marron, Joseph C.

    2009-08-01

    Current optical phased arrays produce images by adaptively phasing the output of several telescopes on a common focal plane. Image based phasing techniques such as Phase Diversity, are used to maintain the phasing in real time. This requires both a computationally intensive algorithm for estimating the phasing errors as well as a means for rapidly adjusting the optical path length through each telescope. In this paper we will compare the adaptive technique of phasing multiple telescopes with the analytic technique of digital holography. Digital holography provides a means of digitally estimating and correcting the phasing errors between the multiple telescopes. The process can occur long after the data has been acquired which relaxes the requirements on the stability of the phased array as well as the mechanical complexity. Experimental results will be shown for adaptive and analytical image formation in remote sensing applications.

  6. Matrix-free mass spectrometric imaging using laser desorption ionisation Fourier transform ion cyclotron resonance mass spectrometry

    PubMed Central

    Goodwin, Richard J A; Pitt, Andrew R; Harrison, David; Weidt, Stefan K; Langridge-Smith, Pat R R; Barrett, Michael P; Logan Mackay, C

    2011-01-01

    Mass spectrometry imaging (MSI) is a powerful tool in metabolomics and proteomics for the spatial localization and identification of pharmaceuticals, metabolites, lipids, peptides and proteins in biological tissues. However, sample preparation remains a crucial variable in obtaining the most accurate distributions. Common washing steps used to remove salts, and solvent-based matrix application, allow analyte spreading to occur. Solvent-free matrix applications can reduce this risk, but increase the possibility of ionisation bias due to matrix adhesion to tissue sections. We report here the use of matrix-free MSI using laser desorption ionisation performed on a 12 T Fourier transform ion cyclotron resonance (FTICR) mass spectrometer. We used unprocessed tissue with no post-processing following thaw-mounting on matrix-assisted laser desorption ionisation (MALDI) indium-tin oxide (ITO) target plates. The identification and distribution of a range of phospholipids in mouse brain and kidney sections are presented and compared with previously published MALDI time-of-flight (TOF) MSI distributions. Copyright © 2011 John Wiley & Sons, Ltd. PMID:21416534

  7. Optical security system using jigsaw transforms of the second random phase mask and the encrypted image in a double random phase encoding system

    NASA Astrophysics Data System (ADS)

    Singh, Madan; Kumar, Arvind; Singh, Kehar

    2008-10-01

    In this paper, we have described a simple and secure double random phase encoding and decoding system to encrypt and decrypt a two-dimensional gray scale image. We have used jigsaw transforms of the second random phase mask and the encrypted image. The random phase mask placed in the Fourier plane is broken into independent non-overlapping segments by applying the jigsaw transform. To make the system more secure, a jigsaw transform on the encrypted image is also carried out. The encrypted image is also broken into independent non-overlapping segments. The jigsaw transform indices of random phase code and the encrypted image form the keys for the successful retrieval of the data. Encrypting with this technique makes it almost impossible to retrieve the image without using both the right keys. Results of computer simulation have been presented in support of the proposed idea. Mean square error (MSE) between the decrypted and the original image has also been calculated in support of the technique.

  8. Measurement of retinal blood flow in the rat by combining Doppler Fourier-domain optical coherence tomography with fundus imaging

    NASA Astrophysics Data System (ADS)

    Werkmeister, René M.; Vietauer, Martin; Knopf, Corinna; Fürnsinn, Clemens; Leitgeb, Rainer A.; Reitsamer, Herbert; Gröschl, Martin; Garhöfer, Gerhard; Vilser, Walthard; Schmetterer, Leopold

    2014-10-01

    A wide variety of ocular diseases are associated with abnormalities in ocular circulation. As such, there is considerable interest in techniques for quantifying retinal blood flow, among which Doppler optical coherence tomography (OCT) may be the most promising. We present an approach to measure retinal blood flow in the rat using a new optical system that combines the measurement of blood flow velocities via Doppler Fourier-domain optical coherence tomography and the measurement of vessel diameters using a fundus camera-based technique. Relying on fundus images for extraction of retinal vessel diameters instead of OCT images improves the reliability of the technique. The system was operated with an 841-nm superluminescent diode and a charge-coupled device camera that could be operated at a line rate of 20 kHz. We show that the system is capable of quantifying the response of 100% oxygen breathing on the retinal blood flow. In six rats, we observed a decrease in retinal vessel diameters of 13.2% and a decrease in retinal blood velocity of 42.6%, leading to a decrease in retinal blood flow of 56.7%. Furthermore, in four rats, the response of retinal blood flow during stimulation with diffuse flicker light was assessed. Retinal vessel diameter and blood velocity increased by 3.4% and 28.1%, respectively, leading to a relative increase in blood flow of 36.2%;. The presented technique shows much promise to quantify early changes in retinal blood flow during provocation with various stimuli in rodent models of ocular diseases in rats.

  9. Computational phase imaging based on intensity transport

    E-print Network

    Waller, Laura A. (Laura Ann)

    2010-01-01

    Light is a wave, having both an amplitude and a phase. However, optical frequencies are too high to allow direct detection of phase; thus, our eyes and cameras see only real values - intensity. Phase carries important ...

  10. 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

    Freiser, B.S.

    1993-09-01

    This report focuses on progress in seven areas: (1) Gas-Phase Reactions of Fe(Benzyne){sup +} with Simple Alkyl Halides; (2) Photodissociation and Collision-Induced Dissociation of Molecular Ions From Methylphenol and Chloromethylphenol; (3) Isotopomer Differentiation Using Metal Ion Chemical Ionization Reagents; (4) Multiple Excitation Collisional Activation (MECA) in Fourier Transform Mass Spectrometry; (5) Chemistry of Fe{sup +}-Arene Ions with Halobenzenes; (6) Gas-Phase Photodissociaton Study of Ag(Benzene){sup +} and Ag(Toluene){sup +}; and (7) Reactivity of Ti{sup 2+} and V{sup 2+} with Small Alkanes.

  11. Image quality and dose efficiency of high energy phase sensitive x-ray imaging: Phantom studies

    PubMed Central

    Wong, Molly Donovan; Wu, Xizeng; Liu, Hong

    2014-01-01

    The goal of this preliminary study was to perform an image quality comparison of high energy phase sensitive imaging with low energy conventional imaging at similar radiation doses. The comparison was performed with the following phantoms: American College of Radiology (ACR), contrast-detail (CD), acrylic edge and tissue-equivalent. Visual comparison of the phantom images indicated comparable or improved image quality for all phantoms. Quantitative comparisons were performed through ACR and CD observer studies, both of which indicated higher image quality in the high energy phase sensitive images. The results of this study demonstrate the ability of high energy phase sensitive imaging to overcome existing challenges with the clinical implementation of phase contrast imaging and improve the image quality for a similar radiation dose as compared to conventional imaging near typical mammography energies. In addition, the results illustrate the capability of phase sensitive imaging to sustain the image quality improvement at high x-ray energies and for – breast – simulating phantoms, both of which indicate the potential to benefit fields such as mammography. Future studies will continue to investigate the potential for dose reduction and image quality improvement provided by high energy phase sensitive contrast imaging. PMID:24865208

  12. Micro- and macro-attenuated total reflection Fourier transform infrared spectroscopic imaging. Plenary Lecture at the 5th International Conference on Advanced Vibrational Spectroscopy, 2009, Melbourne, Australia.

    PubMed

    Kazarian, Sergei G; Chan, K L Andrew

    2010-05-01

    Fourier transform infrared (FT-IR) spectroscopic imaging has become a very powerful method in chemical analysis. In this review paper we describe a variety of opportunities for obtaining FT-IR images using the attenuated total reflection (ATR) approach and provide an overview of fundamental aspects, accessories, and applications in both micro- and macro-ATR imaging modes. The advantages and versatility of both ATR imaging modes are discussed and the spatial resolution of micro-ATR imaging is demonstrated. Micro-ATR imaging has opened up many new areas of study that were previously precluded by inadequate spatial resolution (polymer blends, pharmaceutical tablets, cross-sections of blood vessels or hair, surface of skin, single live cells, cancerous tissues). Recent applications of ATR imaging in polymer research, biomedical and forensic sciences, objects of cultural heritage, and other complex materials are outlined. The latest advances include obtaining spatially resolved chemical images from different depths within a sample, and surface-enhanced images for macro-ATR imaging have also been presented. Macro-ATR imaging is a valuable approach for high-throughput analysis of materials under controlled environments. Opportunities exist for chemical imaging of dynamic aqueous systems, such as dissolution, diffusion, microfluidics, or imaging of dynamic processes in live cells. PMID:20482963

  13. Magnetic field induced differential neutron phase contrast imaging

    SciTech Connect

    Strobl, M.; Treimer, W.; Walter, P.; Keil, S.; Manke, I. [Department of Physical Chemistry, Ruprecht Karls University Heidelberg, Im Neuenheimer Feld 229, 69120 Heidelberg, Germany and Hahn-Meitner Institute Berlin, SF1, Glienickerstr. 100, 14109 Berlin (Germany); Hahn-Meitner Institute Berlin, Glienickerstr. 100, 14109 Berlin, Germany and University of Applied Sciences (TFH) Berlin, Luxemburger Str. 10, 13353 Berlin (Germany); Hahn-Meitner Institute Berlin, Glienickerstr. 100, 14109 Berlin (Germany)

    2007-12-17

    Besides the attenuation of a neutron beam penetrating an object, induced phase changes have been utilized to provide contrast in neutron and x-ray imaging. In analogy to differential phase contrast imaging of bulk samples, the refraction of neutrons by magnetic fields yields image contrast. Here, it will be reported how double crystal setups can provide quantitative tomographic images of magnetic fields. The use of magnetic air prisms adequate to split the neutron spin states enables a distinction of field induced phase shifts and these introduced by interaction with matter.

  14. Schlieren confocal microscopy for phase-relief imaging.

    PubMed

    Xie, Hao; Jin, Dayong; Yu, Junjie; Peng, Tong; Ding, Yichen; Zhou, Changhe; Xi, Peng

    2014-03-01

    We demonstrate a simple phase-sensitive microscopic technique capable of imaging the phase gradient of a transparent specimen, based on the Schlieren modulation and confocal laser scanning microscopy (CLSM). The incident laser is refracted by the phase gradient of the specimen and excites a fluorescence plate behind the specimen to create a secondary illumination; then the fluoresence is modulated by a partial obstructor before entering the confocal pinhole. The quantitative relationship between the image intensity and the sample phase gradient can be derived. This setup is very easy to be adapted to current confocal setups, so that multimodality fluorescence/structure images can be obtained within a single system. PMID:24690716

  15. Edge Detection in Digital Images Using Dispersive Phase Stretch Transform

    PubMed Central

    Asghari, Mohammad H.; Jalali, Bahram

    2015-01-01

    We describe a new computational approach to edge detection and its application to biomedical images. Our digital algorithm transforms the image by emulating the propagation of light through a physical medium with specific warped diffractive property. We show that the output phase of the transform reveals transitions in image intensity and can be used for edge detection. PMID:25878656

  16. Phase contrast image restoration via dictionary representation of diffraction patterns.

    PubMed

    Su, Hang; Yin, Zhaozheng; Kanade, Takeo; Huh, Seungil

    2012-01-01

    The restoration of microscopy images makes the segmentation and detection of cells easier and more reliable, which facilitates automated cell tracking and cell behavior analysis. In this paper, the authors analyze the image formation process of phase contrast images and propose an image restoration method based on the dictionary representation of diffraction patterns. By formulating and solving a min-l1 optimization problem, each pixel is restored into a feature vector corresponding to the dictionary representation. Cells in the images are then segmented by the feature vector clustering. In addition to segmentation, since the feature vectors capture the information on the phase retardation caused by cells, they can be used for cell stage classification between intermitotic and mitotic/apoptotic stages. Experiments on three image sequences demonstrate that the dictionary-based restoration method can restore phase contrast images containing cells with different optical natures and provide promising results on cell stage classification. PMID:23286182

  17. Broadband Phase Retrieval for Image-Based Wavefront Sensing

    NASA Technical Reports Server (NTRS)

    Dean, Bruce H.

    2007-01-01

    A focus-diverse phase-retrieval algorithm has been shown to perform adequately for the purpose of image-based wavefront sensing when (1) broadband light (typically spanning the visible spectrum) is used in forming the images by use of an optical system under test and (2) the assumption of monochromaticity is applied to the broadband image data. Heretofore, it had been assumed that in order to obtain adequate performance, it is necessary to use narrowband or monochromatic light. Some background information, including definitions of terms and a brief description of pertinent aspects of image-based phase retrieval, is prerequisite to a meaningful summary of the present development. Phase retrieval is a general term used in optics to denote estimation of optical imperfections or aberrations of an optical system under test. The term image-based wavefront sensing refers to a general class of algorithms that recover optical phase information, and phase-retrieval algorithms constitute a subset of this class. In phase retrieval, one utilizes the measured response of the optical system under test to produce a phase estimate. The optical response of the system is defined as the image of a point-source object, which could be a star or a laboratory point source. The phase-retrieval problem is characterized as image-based in the sense that a charge-coupled-device camera, preferably of scientific imaging quality, is used to collect image data where the optical system would normally form an image. In a variant of phase retrieval, denoted phase-diverse phase retrieval [which can include focus-diverse phase retrieval (in which various defocus planes are used)], an additional known aberration (or an equivalent diversity function) is superimposed as an aid in estimating unknown aberrations by use of an image-based wavefront-sensing algorithm. Image-based phase-retrieval differs from such other wavefront-sensing methods, such as interferometry, shearing interferometry, curvature wavefront sensing, and Shack-Hartmann sensing, all of which entail disadvantages in comparison with image-based methods. The main disadvantages of these non-image based methods are complexity of test equipment and the need for a wavefront reference.

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

    NASA Astrophysics Data System (ADS)

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

    2012-04-01

    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.

  19. 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

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

    2011-01-01

    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. PMID:21639572

  20. 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)

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

    2011-05-01

    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.

  1. X-ray phase contrast imaging and noise evaluation using a single phase grating interferometer.

    PubMed

    Rizzi, J; Mercère, P; Idir, M; Silva, P Da; Vincent, G; Primot, Jérôme

    2013-07-15

    In this paper we present some quantitative measurements of X-ray phase contrast images and noise evaluation obtained with a recent grating based X-ray phase contrast interferometer. This device is built using a single phase grating and a large broadband X-ray source. It was calibrated using a reference sample and finally used to perform measurements of a biological fossil: a mosquito trapped in amber. As phase images, noise was evaluated from the measured interferograms. PMID:23938580

  2. The Mathematics of Double-Fourier Interferometers

    NASA Astrophysics Data System (ADS)

    Elias, Nicholas M., II; Harwit, Martin; Leisawitz, David; Rinehart, Stephen A.

    2007-03-01

    Recent studies, which are the impetus for this paper, have investigated the possibility of astronomical wide-field double-Fourier interferometry at submillimeter and midinfrared wavelengths. Double-Fourier interferometry combines Michelson interferometry and Fourier transform spectroscopy. At the present time, it is the only technique that promises simultaneous high spatial and spectral resolution. First, we derive the near-general output response for wide-field double-Fourier interferometers using the Jones and Mueller calculi. We employ a ``systems'' approach, expressing the instrument behavior in terms of matrix electric field and intensity impulse responses (point-spread functions) between the sky and the focal plane. This approach is helpful for integrated modeling, Monte Carlo simulations, and developing instrument requirements from science goals. Second, we furnish three wavenumber-dependent observables-visibilities, squared visibility magnitudes, and dirty/processed images-plus their (co)variances in the photon-rich regime. Third, to obtain a basic understanding of the mathematics in this paper, the output responses for perfect, phase-aberrated, and polarization-mismatched optics are produced. Last, we present ideas for future research in wide-field double-Fourier interferometers, such as SPIRIT and SPECS.

  3. Unsupervised Segmentation of Hyperspectral Images Using Modified Phase Correlation

    Microsoft Academic Search

    A. Erturkerturk; S. Erturkerturk

    2006-01-01

    This letter presents hyperspectral image segmentation based on the phase-correlation measure of subsampled hyperspectral data, which is referred to as modified phase correlation. The hyperspectral spectrum of each pixel is initially subsampled to gain robustness against noise and spatial variability, and phase correlation is applied to determine spectral similarity. Similar and dissimilar pixels are decided according to the peak value

  4. Imaging crystallographic phases using time-of-flight neutron diffraction

    Microsoft Academic Search

    Matthias Gutmann; Winfried Kockelmann; Laurent Chapon; Paolo G. Radaelli

    2006-01-01

    Identification and imaging of crystallographic phases inside an object can be achieved by time-of-flight neutron diffraction, based on a correction formula that is usually used to account for a sample offset on a powder diffractometer. The procedure allows the distribution of crystallographic phases along the incident beam path through the thickness of the material to be reconstructed. Phase reconstruction is

  5. CHARACTERIZATION OF AMBIENT PM2.5 AEROSOL AT A SOUTHEASTERN US SITE: FOURIER TRANSFORM INFRARED ANALYSIS OR PARTICLE PHASE

    EPA Science Inventory

    During a field study in the summer of 2000 in the Research Triangle Park (RTP), aerosol samples were collected using a five stage cascade impactor and subsequently analyzed using Fourier Transform Infrared Spectroscopy (FTIR). The impaction surfaces were stainless steel disks....

  6. Interpretation of electron holographic phase images and defocused bright-field images of nanocarbon field emitters

    E-print Network

    Dunin-Borkowski, Rafal E.

    Interpretation of electron holographic phase images and defocused bright-field images of nanocarbon, Lyngby, Denmark filippo_ubaldi@yahoo.it Keywords: electron holography, Fresnel imaging, electrostatic field, image simulation Electron holography is well suited to the investigation of electric and magnetic

  7. Introduction to Fourier Analysis Definition of Fourier analysis

    E-print Network

    Wilkinson, Gerald S.

    Frequency spectrum Phase spectrum #12;Types of periodic waveforms · Amplitude varies in a repeating manner;Periodic nonsinusoidal signals Harmonic series #12;Harmonic series · Harmonic frequencies are integerIntroduction to Fourier Analysis · Definition of Fourier analysis · Analysis of periodic waves

  8. Phase retrieval using regularization method in intensity correlation imaging

    NASA Astrophysics Data System (ADS)

    Li, Xiyu; Gao, Xin; Tang, Jia; Lu, Changming; Wang, Jianli; Wang, Bin

    2014-11-01

    Intensity correlation imaging(ICI) method can obtain high resolution image with ground-based low precision mirrors, in the imaging process, phase retrieval algorithm should be used to reconstituted the object's image. But the algorithm now used(such as hybrid input-output algorithm) is sensitive to noise and easy to stagnate. However the signal-to-noise ratio of intensity interferometry is low especially in imaging astronomical objects. In this paper, we build the mathematical model of phase retrieval and simplified it into a constrained optimization problem of a multi-dimensional function. New error function was designed by noise distribution and prior information using regularization method. The simulation results show that the regularization method can improve the performance of phase retrieval algorithm and get better image especially in low SNR condition

  9. Fast volumetric phase-gradient imaging in thick samples

    PubMed Central

    David Giese, J.; Ford, Tim N.; Mertz, Jerome

    2014-01-01

    Oblique back-illumination microscopy (OBM) provides high resolution, sub-surface phase-gradient images from arbitrarily thick samples. We present an image formation theory for OBM and demonstrate that OBM lends itself to volumetric imaging because of its capacity for optical sectioning. In particular, OBM can provide extended depth of field (EDOF) images from single exposures, by rapidly scanning the focal plane with an electrically tunable lens. These EDOF images can be further enhanced by deconvolution. We corroborate our theory with experimental volumetric images obtained from transparent bead samples and mouse cortical brain slices. PMID:24515075

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

    NASA Astrophysics Data System (ADS)

    Rajput, Sudheesh K.; Nishchal, Naveen K.

    2013-06-01

    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.

  11. Adaptive optics and phase diversity imaging for responsive space applications.

    SciTech Connect

    Smith, Mark William; Wick, David Victor

    2004-11-01

    The combination of phase diversity and adaptive optics offers great flexibility. Phase diverse images can be used to diagnose aberrations and then provide feedback control to the optics to correct the aberrations. Alternatively, phase diversity can be used to partially compensate for aberrations during post-detection image processing. The adaptive optic can produce simple defocus or more complex types of phase diversity. This report presents an analysis, based on numerical simulations, of the efficiency of different modes of phase diversity with respect to compensating for specific aberrations during post-processing. It also comments on the efficiency of post-processing versus direct aberration correction. The construction of a bench top optical system that uses a membrane mirror as an active optic is described. The results of characterization tests performed on the bench top optical system are presented. The work described in this report was conducted to explore the use of adaptive optics and phase diversity imaging for responsive space applications.

  12. Simultaneous birefringence imaging and depth phase resolved measurement using a Fourier domain OCT system

    NASA Astrophysics Data System (ADS)

    Briones-R., Manuel de J.; De La Torre-Ibarra, Manuel H.; Mendoza-Santoyo, Fernando; Pedroza-G., Jesús

    2015-05-01

    A low cost optical coherence tomography (OCT) system to measure simultaneously the birefringence and the internal deformation of a porcine cornea is proposed. The optical system uses polarized light to recover simultaneously the s and p polarization states while a couple of cameras record a fringe pattern that serves to reconstruct the internal structure of the cornea. The p and s interference signals are registered separately in each 2D CMOS array which generates in a single shot an entire B-scan, a feature that allows the tracking of non-repeatable deformations. A birefringence map is generated within the tissue when the p and s polarization states are combined. The experiments were conducted on a cornea that is deformed using a hydro static pressure rig which introduces mechanical micro deformations on it, and the results show concomitantly the micro structure of the cornea, its birefringence and the mechanical micro deformation.

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

    PubMed

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

    2010-09-13

    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

  14. Phase-space formulation for phase-contrast x-ray imaging

    Microsoft Academic Search

    Xizeng Wu; Hong Liu

    2005-01-01

    Phase-space formulation based on the Wigner distribution has been presented for analyzing phase-contrast image formation. Based on the statistical nature and affine canonical covariance of Wigner distributions in the phase space, we show that the partial coherence effects of incident x-ray wave field on image intensity are simply accounted for by a multiplication factor, which is the reduced complex degree

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

    PubMed

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

    2012-01-01

    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

  16. Fourier Transform Near Infrared Microspectroscopy, Infrared Chemical Imaging, High-Resolution Nuclear Magnetic Resonance and Fluorescence Microspectroscopy Detection of Single Cancer Cells and Single Viral Particles

    E-print Network

    Baianu,I C; Hofmann, N E; Korban, S S; Lozano, P; You, T

    2004-01-01

    Single Cancer Cells from Human tumors are being detected and imaged by Fourier Transform Infrared (FT-IR), Fourier Transform Near Infrared (FT-NIR)Hyperspectral Imaging and Fluorescence Correlation Microspectroscopy. The first FT-NIR chemical, microscopic images of biological systems approaching one micron resolution are here reported. Chemical images obtained by FT-NIR and FT-IR Microspectroscopy are also presented for oil in soybean seeds and somatic embryos under physiological conditions. FT-NIR spectra of oil and proteins were obtained for volumes as small as two cubic microns. Related, HR-NMR analyses of oil contents in somatic embryos as well as 99% accurate calibrations are also presented here with nanoliter precision. Such high-resolution, 400 MHz H-1 NMR analyses allowed the selection of mutagenized embryos with higher oil content (e.g. >~20%) compared to the average levels in non-mutagenized control embryos. Moreover, developmental changes in single soybean seeds and/or somatic embryos may be monito...

  17. Application of phase-diversity to solar images

    Microsoft Academic Search

    Mats G. Lofdahl; Goran B. Scharmer

    1994-01-01

    We have implemented a least-squares technique for recovering phase information and alignment parameters from simultaneously obtained focused and defocused solar images. Small subfields are used, in order to deal with anisoplanatism. The method is applied to sequences of 100 8-bit solar granulation images. These data enable a number of consistency tests, all of which demonstrate that the technique works. Alignment

  18. Phase-sensitive X-ray imager

    DOEpatents

    Baker, Kevin Louis

    2013-01-08

    X-ray phase sensitive wave-front sensor techniques are detailed that are capable of measuring the entire two-dimensional x-ray electric field, both the amplitude and phase, with a single measurement. These Hartmann sensing and 2-D Shear interferometry wave-front sensors do not require a temporally coherent source and are therefore compatible with x-ray tubes and also with laser-produced or x-pinch x-ray sources.

  19. Fourier domain mode-locked lasers for swept source OCT imaging at up to 290 kHz scan rates

    Microsoft Academic Search

    R. Huber; K. Taira; M. Wojtkowski; J. G. Fujimoto

    2006-01-01

    A new type of laser operation, Fourier Domain Mode Locking (FDML), is demonstrated for high performance, frequency swept light sources. FDML achieves superior sweep speeds, coherence lengths and bandwidths compared to standard bulk or fiber lasers. At 1300 nm a sweep range up to 145 nm, up to 4 cm delay length, and sweep rates up to 290 kHz were

  20. Triple-phase bone image abnormalities in Lyme arthritis

    SciTech Connect

    Brown, S.J.; Dadparvar, S.; Slizofski, W.J.; Glab, L.B.; Burger, M. (Hahnemann Univ. Hospital, Philadelphia, PA (USA))

    1989-10-01

    Arthritis is a frequent manifestation of Lyme disease. Limited triple-phase Tc-99m MDP bone imaging of the wrists and hands with delayed whole-body images was performed in a patient with Lyme arthritis. This demonstrated abnormal joint uptake in the wrists and hands in all three phases, with increased activity seen in other affected joints on delayed whole-body images. These findings are nonspecific and have been previously described in a variety of rheumatologic conditions, but not in Lyme disease. Lyme disease should be considered in the differential diagnosis of articular and periarticular bone scan abnormalities.

  1. Video sequence segmentation and keyframe description based on phase-correlation of differential images

    NASA Astrophysics Data System (ADS)

    Song, Yongjiang; Xia, LiangZheng; Yang, Shizhou

    2001-09-01

    Video segmentation, key-frame selection and description are essential steps for CBIR. New techniques about video sequences to suit the needs of CBIR are studied in this article. Data structure of video, a key of CBIR, is defined by scene, shot and key-frame of shot. Secondly, we propose a completely implement method of scene segmentation and shot segmentation using phase correlation function of differential images. Moreover, we define key-frame of a shot base don the mosaic picture an describe it based on the Fourier Descriptor after we discuss various select schemes of shot key-frame depend on the characters of video sequence. There are diverse movements between two frames, such as shift, rotation and scale. In this paper, we introduce the phase correlatively between images in log- polar coordinates to detect rotation and scale and the phase correlativity in Cartesian coordinates is exploited to find shift. We further demonstrate that the proposed method as a powerful tool for segmentation of video sequences.

  2. Phase-shifting technique for improving the imaging capacity of sparse-aperture optical interferometers.

    PubMed

    Hénault, François

    2011-07-20

    We describe the principle of a multiaperture interferometer that uses a phase-shifting technique and is suitable for quick snapshot imaging of astrophysical objects at extreme angular resolution through Fourier inversion. A few advantages of the proposed design are highlighted, among which are radiometric efficiency, field of view equivalent to those of Fizeau interferometers, and a preliminary calibration procedure allowing characterization of instrumental errors. For large telescope numbers, the proposed design also results in considerable simplification of the optical and mechanical design. Numerical simulations suggest that it should be possible to couple hundreds of telescopes on a single 4K × 4K detector array, using only conventional optical components or emerging technologies. PMID:21772409

  3. Phase Sensitive Cueing for 3D Objects in Overhead Images

    SciTech Connect

    Paglieroni, D W; Eppler, W G; Poland, D N

    2005-02-18

    A 3D solid model-aided object cueing method that matches phase angles of directional derivative vectors at image pixels to phase angles of vectors normal to projected model edges is described. It is intended for finding specific types of objects at arbitrary position and orientation in overhead images, independent of spatial resolution, obliqueness, acquisition conditions, and type of imaging sensor. It is shown that the phase similarity measure can be efficiently evaluated over all combinations of model position and orientation using the FFT. The highest degree of similarity over all model orientations is captured in a match surface of similarity values vs. model position. Unambiguous peaks in this surface are sorted in descending order of similarity value, and the small image thumbnails that contain them are presented to human analysts for inspection in sorted order.

  4. Full-wave approach for x-ray phase imaging.

    PubMed

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

    2013-07-29

    We present a rigorous forward model for phase imaging of a 3-D object illuminated by a cone-shaped x-ray beam. Our model is based on a full-wave approach valid under the first Rytov approximation, and thus can be used with large and thick objects, e.g., luggage and human patients. We unify light-matter interaction and free-space propagation into an integrated wave optics framework. Therefore, our model can accurately calculate x-ray phase images formed with sources of arbitrary shape, and it can be effectively incorporated into x-ray phase tomography as a forward model. Within the best of our knowledge, this is the first non-paraxial, full-wave model for X-ray phase imaging. PMID:23938626

  5. Self-imaging of transparent objects and structures in focusing of spatially phase-modulated laser radiation into a weakly absorbing medium

    SciTech Connect

    Bubis, E L [Institute of Applied Physics, Russian Academy of Sciences, Nizhny Novgorod (Russian Federation)

    2011-06-30

    Self-imaging of transparent objects and structures in focusing of a spatially phase-modulated laser beam into an extended weakly absorbing medium is described. The laser power level that is necessary for effective imaging corresponds to the illuminating beam power when thermal self-defocusing starts evolving in the medium. The effect can be described in terms of the ideology of Zernike's classical phase-contrast method. Edge enhancement in visualised images of transparent objects is experimentally demonstrated. Self-imaging of a microscopic object in the form of transparent letters and long-lived refractive-index fluctuations in liquid glycerol is shown. Due to the adaptivity of the process under consideration, unlike the classical case, self-imaging occurs also in the situations where a beam is displaced (undergoes random walk) as a whole in the Fourier plane, for example, in the presence of thermal flows. (image processing)

  6. Phase Preserving Dynamic Range Compression of Aeromagnetic Images

    NASA Astrophysics Data System (ADS)

    Kovesi, Peter

    2014-05-01

    Geoscientific images with a high dynamic range, such as aeromagnetic images, are difficult to present in a manner that facilitates interpretation. The data values may range over 20000 nanoteslas or more but a computer monitor is typically designed to present input data constrained to 8 bit values. Standard photographic high dynamic range tonemapping algorithms may be unsuitable, or inapplicable to such data because they are have been developed on the basis of statistics of natural images, feature types found in natural images, and models of the human visual system. These algorithms may also require image segmentation and/or decomposition of the image into base and detail layers but these operations may have no meaning for geoscientific images. For geological and geophysical data high dynamic range images are often dealt with via histogram equalization. The problem with this approach is that the contrast stretch or compression applied to data values depends on how frequently the data values occur in the image and not on the magnitude of any data features themselves. This can lead to inappropriate distortions in the output. Other approaches include use of the Automatic Gain Control algorithm developed by Rajagopalan, or the tilt derivative. A difficulty with these approaches is that the signal can be over-normalized and perception of the overall variations in the signal can be lost. To overcome these problems a method is presented that compresses the dynamic range of an image while preserving local features. It makes no assumptions about the formation of the image, the feature types it contains, or its range of values. Thus, unlike algorithms designed for photographic images, this algorithm can be applied to a wide range of scientific images. The method is based on extracting local phase and amplitude values across the image using monogenic filters. The dynamic range of the image can then be reduced by applying a range reducing function to the amplitude values, for example taking the logarithm, and then reconstructing the image using the original phase values. An important attribute of this approach is that the local phase information is preserved, this is important for the human visual system in interpreting the image. The result is an image that retains the fidelity of its features within a greatly reduced dynamic range. An additional advantage of the method is that the range of spatial frequencies that are used to reconstruct the image can be chosen via high-pass filtering to control the scale of analysis. A relatively low cutoff frequency allows large overall trends in the data to be observed. As the spatial cutoff frequency is progressively increased the analysis becomes more localized and the relative magnitudes of features become more equal.

  7. Imaging analysis of photorefractive phased array beamforming

    NASA Astrophysics Data System (ADS)

    Kriehn, Gregory; Kiruluta, Andrew M.; Silveira, Paulo E. X.; Weaver, Samuel P.; Wagner, Kelvin H.

    1998-10-01

    We present the analytical description of a photorefractive phased array beamforming system using the BEAMTAP (Broadband and Efficient Adaptive Method for True-Time-Delay Array Processing) algorithm for a large N-element array that requires only 2 tapped delay lines (TDLs) instead of the conventional N TDLs. Simulation results indicate that the processor is able to adapt to a broadband signal of interest at a specific angle of arrival. We show that the system produces a coherent sum of the desired signals from the phased array, with the corresponding time delays appropriately compensated for in an adaptive fashion without prior knowledge of the angle-of-arrival.

  8. Fourier Transform Heterodyne Techniques Applied To Astronomy

    NASA Astrophysics Data System (ADS)

    Laubscher, B. E.; Cooke, B. J.; Edwards, B. C.

    1998-12-01

    Fourier Transform Heterodyne (FTH) is a detection process capable of directly imaging the transverse amplitude and phase of coherent electromagnetic fields. Based on coherent detection principles governing conventional heterodyned systems, Fourier Transform Heterodyne (FTH) incorporates transverse spatial encoding of the local oscillator for image capture. Appropriate selection of spatial encoding functions (basis set) allows image retrieval by way of classic Fourier manipulations. Of practical interest: 1) Imaging is accomplished on a single element detector/sensor requiring no additional scanning or moving components. 2) Because detection is governed by heterodyne principles, near quantum limited performance is achievable. 3) The concept is general with the applicable electromagnetic spectrum encompassing the RF through optical. Although FTH is currently in its infancy, we believe this technique will provide new tools and concepts important to the development of future astronomical systems. For example: 1) An FTH-based optical or infrared interferometer (whether ground-based or space-based) can operate in direct analogy to VLBI radio astronomy systems. 2) FTH may be capable of measuring the atmospheric distortions of a target star to guide adaptive optical correction systems. 3) FTH may be used to determine the adjustments required to align a deployed structure in space and can remove aberrations from slight residual misalignments during operation. The work to be presented will include a brief introduction of the underlying principles governing FTH imaging, followed by cursory description of a simple proof-of-concept experiment carried out using a HeNe laser, a 69 element spatial phase modulator, and a 36 term Zernike basis set. Finally, astronomical applications will be discussed.

  9. Optical Physics of Imaging and Interferometric Phased Arrays

    E-print Network

    Withington, S; Hobson, M P; Withington, Stafford; Saklatvala, George; Hobson, Michael P.

    2006-01-01

    Microwave, submillimetre-wave, and far-infrared phased arrays are of considerable importance for astronomy. We consider the behaviour imaging phased arrays and interferometric phased arrays from a functional perspective. It is shown that the average powers, field correlations, power fluctuations, and correlations between power fluctuations at the output ports of an imaging or interferometric phased array can be found once the synthesised reception patterns are known. The reception patterns do not have to be orthogonal or even linearly independent. It is shown that the operation of phased arrays is intimately related to the mathematical theory of frames, and that the theory of frames can be used to determine the degree to which any class of intensity or field distribution can be reconstructed unambiguously from the complex amplitudes of the travelling waves at the output ports. The theory can be used to set up a likelihood function that can, through Fisher information, be used to determine the degree to which ...

  10. Super resolution imaging with an ELT: Kernel-phase interferometry

    NASA Astrophysics Data System (ADS)

    Martinache, Frantz

    2013-12-01

    Kernel-phase is a recently developed paradigm that tackles the classical problem of image deconvolution, based on an interferometric point of view of image formation. Kernel-phase inherits and borrows from the notion of closure-phase, especially as it is used in the context of non-redundant Fizeau interferometry, but extends its application to pupils of arbitrary shape, for diffraction limited images. The additional calibration brought by kernel-phase boosts the resolution of conventional images and enables the detection of otherwise hidden faint features at the resolution limit and beyond, a regime often refered to as super-resolution, which for a 30-meter telescope in the near IR, this translates into a resolving power smaller than 10 mas. Kernel-phase analysis of archival space and ground based AO data leads to new discoveries and/or improved relative astrometry and photometry. The paper presents the current status of the technique and some of its recent developments and applications that lead to recommendations for super-resolution imaging with ELTs.

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

    NASA Astrophysics Data System (ADS)

    Mo, Xutao; Wang, Jinjiang

    2013-09-01

    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.

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

    PubMed Central

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

    2012-01-01

    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 achieved by integrating an imaging fiber probe inside a stainless steel needle and 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. Real-time data acquisition, processing, motion compensation, and image visualization and saving were implemented on a custom CPU-GPU hybrid architecture. We performed 10× zero padding to the raw spectrum to obtain 0.16 µm position accuracy with a compensation rate of 460 Hz. The root-mean-square error of hand-held distance variation from target position was measured to be 2.93 µm. We used a cross-correlation maximization-based shift correction algorithm for topology correction. To validate the system, we performed free-hand OCT M-scan imaging using various samples. PMID:23243562

  13. Self-imaging phase mask used in digital holography with phase-shifting

    NASA Astrophysics Data System (ADS)

    Fajst, Agnieszka; Sypek, Maciej; Makowski, Michal; Suszek, Jaroslaw; Kolodziejczyk, Andrzej

    2008-12-01

    The digital reconstruction of an optically recorded hologram has become a fast developing method and has found a vast practical application in many branches of science and industry. An especially invented diffractive optical element with self imaging properties is placed in the reference beam. In the recording process this element forms its self-image in the hologram plane. Self-imaging properties of the diffractive optical element provide the possibility of recording a digital hologram by means of the phase-shifting without any additional imaging components. The innovation of the proposed method lies in using a self-imaging diffractive optical element which enables a significant simplification of a spatial phase shifting optical setup used to record the digital hologram with only a small decrease of the quality of the reconstructed image.

  14. Phase retrieval and differential phase-contrast imaging with low-brilliance

    E-print Network

    Loss, Daniel

    -sensitive imaging methods to improve the contrast1,2 . However, the requirements of the illuminating radiation mean that hard-X-ray phase-sensitive imaging has until now been impractical with more readily available X of the use of crystal optics, interferometric and analyser-based methods rely on a highly parallel

  15. Bessel Fourier Orientation Reconstruction (BFOR): An Analytical Diffusion Propagator Reconstruction for Hybrid Diffusion Imaging and Computation of q-Space Indices

    PubMed Central

    Hosseinbor, A. Pasha; Chung, Moo K.; Wu, Yu-Chien; Alexander, Andrew L.

    2012-01-01

    The ensemble average propagator (EAP) describes the 3D average diffusion process of water molecules, capturing both its radial and angular contents. The EAP can thus provide richer information about complex tissue microstructure properties than the orientation distribution function (ODF), an angular feature of the EAP. Recently, several analytical EAP reconstruction schemes for multiple q-shell acquisitions have been proposed, such as diffusion propagator imaging (DPI) and spherical polar Fourier imaging (SPFI). In this study, a new analytical EAP reconstruction method is proposed, called Bessel Fourier orientation reconstruction (BFOR), whose solution is based on heat equation estimation of the diffusion signal for each shell acquisition, and is validated on both synthetic and real datasets. A significant portion of the paper is dedicated to comparing BFOR, SPFI, and DPI using hybrid, non-Cartesian sampling for multiple b-value acquisitions. Ways to mitigate the effects of Gibbs ringing on EAP reconstruction are also explored. In addition to analytical EAP reconstruction, the aforementioned modeling bases can be used to obtain rotationally invariant q-space indices of potential clinical value, an avenue which has not yet been thoroughly explored. Three such measures are computed: zero-displacement probability (Po), mean squared displacement (MSD), and generalized fractional anisotropy (GFA). PMID:22963853

  16. Optical image encryption in phase space

    NASA Astrophysics Data System (ADS)

    Liu, Jun; Xu, Xiaobin; Situ, Guohai; Wu, Quanying

    2014-11-01

    In the field of optical information security, the research of double random phase encoding is becoming deeper with each passing day, however the encryption system is linear, and the dependencies between plaintext and ciphertext is not complicated, with leaving a great hidden danger to the security of the encryption system. In this paper, we encrypted the higher dimensional Wigner distribution function of low dimensional plaintext by using the bilinear property of Wigner distribution function. Computer simulation results show that this method can not only enlarge the key space, but also break through the linear characteristic of the traditional optical encryption technology. So it can significantly improve the safety of the encryption system.

  17. Calculating T2 in images from a phased array receiver.

    PubMed

    Hardy, Peter A; Andersen, Anders H

    2009-04-01

    Images reconstructed from multielement, phased array coils and presented as the square root of the sum of the squares of the signals received by the individual elements have a distribution of signal and noise that distorts the relationship between the image intensity and the underlying signal. The distortion is accentuated for long echo times for which the signal-to-noise ratio (SNR) may be low. When measuring T(2) or T(2)* this signal distortion leads to biased estimates of these parameters. We demonstrate this effect and its dependence on the image SNR and the number of elements in a phased array coil. We evaluated the effects of four techniques for calculating T(2) from data acquired in phased array coils (log transform, least squares, lookup table correction, and maximum likelihood [ML] estimation). The ML estimation gave the most accurate T(2) in the presence of this bias. PMID:19215046

  18. Calculating T2 in Images from a Phased Array Receiver

    PubMed Central

    Hardy, Peter A.; Andersen, Anders H.

    2009-01-01

    Images reconstructed from multi-element, phased array coils and presented as the square root of the sum of the squares of the signals received by the individual elements have a distribution of signal and noise which distorts the relationship between the image intensity and the underlying signal. The distortion is accentuated for long echo times where the signal-to-noise ratio may be low. When measuring T2 or T2* this signal distortion leads to biased estimates of these parameters. We demonstrate this effect and its dependence on the image signal-to-noise ratio and the number of elements in a phased array coil. We evaluated the effects of four techniques for calculating T2 from data acquired in phased array coils (log transform, least squares, look-up table correction and maximum likelihood estimation). The maximum likelihood estimation gave the most accurate T2 in the presence of this bias. PMID:19215046

  19. Assessment of material blending distribution for electrospun nanofiber membrane by Fourier transform infrared (FT-IR) microspectroscopy and image cluster analysis

    NASA Astrophysics Data System (ADS)

    Sunthornvarabhas, Jackapon; Thumanu, Kanjana; Limpirat, Wanwisa; Kim, Hyun-Joong; Piyachomkwan, Kuakoon; Sriroth, Klanarong

    2014-09-01

    Electrospun nanofibers between starch and polyethylene oxide were successfully prepared to be used as a template for wound healing application. Material blending ratios and fabrication conditions were optimized to determine the ability to control material spatial for further development. A fourier Transform Infrared (FT-IR) mapping system and purposed modified image clustering analysis were adopted to evaluate the material homogeneity of a sheet of homogeneous composite nanofibers. The fabrication conditions and material blending ratios both have an influence on the material distribution and optimum points were observed from this technique. This study showed the possibility of using a quick and non-destructive technique and a modified image cluster analysis technique to evaluate the homogeneity of the electrospun nanofiber sheet.

  20. Subwavelength imaging using phase-conjugating nonlinear nanoantenna arrays.

    PubMed

    Chen, Pai-Yen; Alù, Andrea

    2011-12-14

    We investigate the use of nonlinear metasurfaces formed by plasmonic nanoantennas loaded with ?(3) nonlinear elements, in order to realize subwavelength imaging based on phase conjugation and time reversal. The nanoantennas' plasmonic resonance is used to boost the nonlinear response over an ultrathin surface, meeting the conditions for efficient phase conjugation necessary for imaging applications. Pairing two such surfaces, we put forward a realistic design for a time-reversal 'perfect lens', which can overcome the limitations in resolution and sensitivity to losses typical of negative-index lenses. PMID:22087878

  1. Development of a multichannel Fourier transform spectrometer.

    PubMed

    Ebizuka, N; Wakaki, M; Kobayashi, Y; Sato, S

    1995-12-01

    We devised a novel type of multichannel Fourier transform spectrometer (MCFTS) that incorporates a Wollaston prism, polarizing interferometer combined with two Savart plates and a phase-retarding plate. This original MCFTS produces a number of lines of folded interferograms recorded with a two-dimensional imaging detector such as a CCD detector. In the present type of MCFTS, the total incident light is available except for a small amount of reflection loss. It is possible to enhance the signal-to-noise ratio. The enhancement of the resolving power is also expected by the connection of the interferograms with a newly developed method. PMID:21068884

  2. Parametric phase information based 2D Cepstrum PSF estimation method for blind de-convolution of ultrasound imaging

    NASA Astrophysics Data System (ADS)

    Kang, Jooyoung; Park, Sung-Chan; Kim, Jung-ho; Song, Jongkeun

    2014-02-01

    In the ultrasound imaging system, blurring which occurs after passing through ultrasound scanner system, represents point spread function (PSF) that describes the response of the ultrasound imaging system to a point source distribution. So, de-blurring can be achieved by de-convolving the ultrasound images with an estimated of corresponding PSF. However, it is hard to attain an accurate estimation of PSF due to the unknown properties of the tissues of the human body through the ultrasound signal propagates. In this paper, we present a new method for PSF estimation in the Fourier domain (FD) based on parametric minimum phase information, and simultaneously, it performs fast 2D de-convolution in the ultrasound imaging system. Although most of complex cepstrum methods [14], are obtained using complex 2D phase unwrapping [18] [19] in order to estimate the FD-phase information of PSF, our algorithm estimates the 2D PSF using 2D FD-phase information with the parametric weighting factor ? and ?. They affect the feature of PSF shapes.This makes the computations much simpler and the estimation more accurate. Our algorithm works on the beam-formed uncompressed radio-frequency data, with pre-measured and estimated 2D PSFs database from actual probe used. We have tested our algorithm with vera-sonic system and commercial ultrasound scanner (Philips C4-2), in known speed of sound phantoms and unknown speeds in vivo scans.

  3. High-resolution phase-conjugate imaging in double-pumped phase conjugators

    NASA Astrophysics Data System (ADS)

    Yarrison-Rice, Jan M.; Sharp, Edward J.; Wood, Gary L.; Salamo, Gregory J.; Klank, Robert; Neurgaonkar, Ratnakar R.

    1995-11-01

    Phase-conjugate images with a resolution greater than 250 lines/mm are obtained through the use of a bridge, double-pumped phase conjugator. We demonstrate that this conjugator can carry out image-processing tasks, such as the addition and subtraction of complex spatial distributions, with a spatial resolution of greater than 100 lines/mm. These results represent a significant improvement over previously reported resolutions obtained from photorefractive mutually pumped phase conjugators and approach the theoretical limit imposed by the grating spacing and cross talk.

  4. Phase space imaging in optical design

    NASA Astrophysics Data System (ADS)

    Rausch, Denise; Herkommer, Alois

    2014-09-01

    In the last years the requirement of special illumination optics increased in the course of developing specific optical systems for wide range of applications in industries and science. Standard components become continuously substituted by more complex freeform surfaces with higher efficiency. Therefore, other methods in evaluating optical systems are of special interest. In illumination design the classic way to check the performance of a system is to trace a huge number of rays through the system and analyze the radiance and irradiance distribution on the target surface. Another access to the most important illumination quantities like radiance is to look at the transformation of etendue in phase space. This offers a new perspective for the optical designer onto illumination systems. Another interesting aspect is the analysis of aberrations also for freeform elements where standard aberration theory for rotational symmetric systems fail.

  5. Full-phase image encryption by two-step phase-shifting interferometry

    NASA Astrophysics Data System (ADS)

    Meng, Xiangfeng; Cai, Luzhong; Xu, Xianfeng; Yang, Xiulun; Shen, Xiaoxia; Dong, Guoyan; Zhang, Hao

    2008-07-01

    We have proposed a full-phase image encryption method based on double random-phase encoding in Fresnel domain and pixel random permutation (PRP) technique with the use of two-step phase-shifting interferometry (PSI) we reported recently, and verified the effectiveness of this method and its robustness against occlusion and noise attacks by a series of numerical simulations. Comparing with other similar methods, this approach can decrease the number of the interferograms to be delivered from at least three needed in ordinary PSI to only two, give much better performance of image reconstruction than amplitude-based encryption, and provide much higher security level. This method is usable for both the gray-level images and binary images, and usually the latter will lead to better results.

  6. Phase-space formulation for phase-contrast x-ray imaging.

    PubMed

    Wu, Xizeng; Liu, Hong

    2005-10-01

    Phase-space formulation based on the Wigner distribution has been presented for analyzing phase-contrast image formation. Based on the statistical nature and affine canonical covariance of Wigner distributions in the phase space, we show that the partial coherence effects of incident x-ray wave field on image intensity are simply accounted for by a multiplication factor, which is the reduced complex degree of coherence of the incident x-ray wave field. We show especially that with the undulator sources one cannot obtain the phase-contrast intensity by summing over the contributions from all electron positions, since the van Cittert-Zernike theorem fails in general for undulators. We derive a comprehensive formula that quantifies the effects of partial spatial coherence, polychromatic spectrum, body attenuation, imaging-detector resolution, and radiation dose on phase-contrast visibility in clinical imaging. The results of our computer modeling and simulations show how the formula can provide design guidelines and optimal parameters for clinical x-ray phase-contrast imaging systems. PMID:16231790

  7. Phase-space formulation for phase-contrast x-ray imaging

    SciTech Connect

    Wu Xizeng; Liu Hong

    2005-10-01

    Phase-space formulation based on the Wigner distribution has been presented for analyzing phase-contrast image formation. Based on the statistical nature and affine canonical covariance of Wigner distributions in the phase space, we show that the partial coherence effects of incident x-ray wave field on image intensity are simply accounted for by a multiplication factor, which is the reduced complex degree of coherence of the incident x-ray wave field. We show especially that with the undulator sources one cannot obtain the phase-contrast intensity by summing over the contributions from all electron positions, since the van Cittert-Zernike theorem fails in general for undulators. We derive a comprehensive formula that quantifies the effects of partial spatial coherence, polychromatic spectrum, body attenuation, imaging-detector resolution, and radiation dose on phase-contrast visibility in clinical imaging. The results of our computer modeling and simulations show how the formula can provide design guidelines and optimal parameters for clinical x-ray phase-contrast imaging systems.

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

    SciTech Connect

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

    2008-01-01

    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.

  9. Identification of volatile basic components in tobacco by headspace liquid-phase microextraction coupled to matrix-assisted laser desorption/ionization with Fourier transform mass spectrometry.

    PubMed

    Sun, Shihao; Cheng, Zhihong; Xie, Jianping; Zhang, Jianxun; Liao, Yuanxi; Wang, Haoyang; Guo, Yinlong

    2005-01-01

    A method incorporating headspace liquid-phase microextraction (HS-LPME) coupled to matrix-assisted laser desorption/ionization (MALDI) with Fourier transform mass spectrometry (FTMS) was established to analyze volatile basic components in tobacco. The sample preparation volume for MALDI-MS was compatible with the volume of the solvent microdrop in the HS-LPME procedure. The pH and the polarity of the solvent for HS-LPME were adjusted by choice of the MALDI matrix and matrix additive. Based on the elemental composition and tandem mass spectrometry information, 25 volatile nitrogenous compounds in tobacco were detected and identified. The approach is fast and sensitive, and has the potential for automation for high-throughput analysis. This approach offers an alternative method for analysis of trace volatile organic compounds in complex samples. PMID:15768451

  10. Fully phase image encryption using double random-structured phase masks in gyrator domain.

    PubMed

    Singh, Hukum; Yadav, A K; Vashisth, Sunanda; Singh, Kehar

    2014-10-01

    We propose a method for fully phase image encryption based on double random-structured phase mask encoding in the gyrator transform (GT) domain. The security of the system is strengthened by parameters used in the construction of a structured phase mask (SPM) based on a devil's vortex Fresnel lens (DVFL). The input image is recovered using the correct parameters of the SPMs, transform orders of the GT, and conjugate of the random phase masks. The use of a DVFL-based SPM enhances security by increasing the key space for encryption, and also overcomes the problem of axis alignment associated with an optical setup. The proposed scheme can also be implemented optically. The computed values of mean squared error between the retrieved and the original image show the efficacy of the proposed scheme. We have also investigated the scheme's sensitivity to the encryption parameters, and robustness against occlusion and multiplicative Gaussian noise attacks. PMID:25322235

  11. Whole-cell phase contrast imaging at the nanoscale using Fresnel Coherent Diffractive Imaging Tomography

    PubMed Central

    Jones, Michael W. M.; van Riessen, Grant A.; Abbey, Brian; Putkunz, Corey T.; Junker, Mark D.; Balaur, Eugeniu; Vine, David J.; McNulty, Ian; Chen, Bo; Arhatari, Benedicta D.; Frankland, Sarah; Nugent, Keith A.; Tilley, Leann; Peele, Andrew G.

    2013-01-01

    X-ray tomography can provide structural information of whole cells in close to their native state. Radiation-induced damage, however, imposes a practical limit to image resolution, and as such, a choice between damage, image contrast, and image resolution must be made. New coherent diffractive imaging techniques, such Fresnel Coherent Diffractive Imaging (FCDI), allows quantitative phase information with exceptional dose efficiency, high contrast, and nano-scale resolution. Here we present three-dimensional quantitative images of a whole eukaryotic cell by FCDI at a spatial resolution below 70?nm with sufficient phase contrast to distinguish major cellular components. From our data, we estimate that the minimum dose required for a similar resolution is close to that predicted by the Rose criterion, considerably below accepted estimates of the maximum dose a frozen-hydrated cell can tolerate. Based on the dose efficiency, contrast, and resolution achieved, we expect this technique will find immediate applications in tomographic cellular characterisation. PMID:23887204

  12. Rapid quantitative phase imaging for partially coherent light microscopy.

    PubMed

    Rodrigo, José A; Alieva, Tatiana

    2014-06-01

    Partially coherent light provides promising advantages for imaging applications. In contrast to its completely coherent counterpart, it prevents image degradation due to speckle noise and decreases cross-talk among the imaged objects. These facts make attractive the partially coherent illumination for accurate quantitative imaging in microscopy. In this work, we present a non-interferometric technique and system for quantitative phase imaging with simultaneous determination of the spatial coherence properties of the sample illumination. Its performance is experimentally demonstrated in several examples underlining the benefits of partial coherence for practical imagining applications. The programmable optical setup comprises an electrically tunable lens and sCMOS camera that allows for high-speed measurement in the millisecond range. PMID:24921541

  13. Mouse blood vessel imaging by in-line x-ray phase-contrast imaging

    Microsoft Academic Search

    Xi Zhang; Xiao-Song Liu; Xin-Rong Yang; Shao-Liang Chen; Pei-Ping Zhu; Qing-Xi Yuan

    2008-01-01

    It is virtually impossible to observe blood vessels by conventional x-ray imaging techniques without using contrast agents. In addition, such x-ray systems are typically incapable of detecting vessels with diameters less than 200 µm. Here we show that vessels as small as 30 µm could be detected using in-line phase-contrast x-ray imaging without the use of contrast agents. Image quality

  14. Correction of phase-error for phase-resolved k-clocked optical frequency domain imaging

    NASA Astrophysics Data System (ADS)

    Mo, Jianhua; Li, Jianan; de Boer, Johannes F.

    2012-01-01

    Phase-resolved optical frequency domain imaging (OFDI) has emerged as a promising technique for blood flow measurement in human tissues. Phase stability is essential for this technique to achieve high accuracy in flow velocity measurement. In OFDI systems that use k-clocking for the data acquisition, phase-error occurs due to jitter in the data acquisition electronics. We presented a statistical analysis of jitter represented as point shifts of the k-clocked spectrum. We demonstrated a real-time phase-error correction algorithm for phase-resolved OFDI. A 50 KHz wavelength-swept laser (Axsun Technologies) based balanced-detection OFDI system was developed centered at 1310 nm. To evaluate the performance of this algorithm, a stationary gold mirror was employed as sample for phase analysis. Furthermore, we implemented this algorithm for imaging of human skin. Good-quality skin structure and Doppler image can be observed in real-time after phase-error correction. The results show that the algorithm can effectively correct the jitter-induced phase error in OFDI system.

  15. Differential phase contrast X-ray imaging system and components

    DOEpatents

    Stutman, Daniel; Finkenthal, Michael

    2014-07-01

    A differential phase contrast X-ray imaging system includes an X-ray illumination system, a beam splitter arranged in an optical path of the X-ray illumination system, and a detection system arranged in an optical path to detect X-rays after passing through the beam splitter.

  16. Phasing segmented mirrors using defocused images at visible wavelengths

    Microsoft Academic Search

    A. Schumacher; N. Devaney

    2006-01-01

    Plans for future optical telescopes of diameter more than 10m are based on segmented mirrors, made up of hundreds or even thousands of segments. A challenge for these telescopes is the alignment in piston (cophasing) where phase differences between individual segments have to be reduced to a small fraction of the observing wavelength in order to avoid degradation of image

  17. 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...

  18. Cassini UVIS Observatory Phase spectral imaging of the Saturn system

    Microsoft Academic Search

    D. Shemansky; Cassini Uvis

    2004-01-01

    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

  19. Dynamic Studies of Lung Fluid Clearance with Phase Contrast Imaging

    SciTech Connect

    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

    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.

  20. Drive frequency dependent phase imaging in piezoresponse force microscopy

    SciTech Connect

    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

    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.

  1. Imaging through turbulence with a quadrature-phase optical interferometer.

    PubMed

    Kern, Brian; Dimotakis, Paul E; Martin, Chris; Lang, Daniel B; Thessin, Rachel N

    2005-12-01

    We present an improved technique for imaging through turbulence at visible wavelengths using a rotation shearing pupil-plane interferometer, intended for astronomical and terrestrial imaging applications. While previous astronomical rotation shearing interferometers have made only visibility modulus measurements, this interferometer makes four simultaneous measurements on each interferometric baseline, with phase differences of pi/2 between each measurement, allowing complex visibility measurements (modulus and phase) across the entire input pupil in a single exposure. This technique offers excellent wavefront resolution, allowing operation at visible wavelengths on large apertures, is potentially immune to amplitude fluctuations (scintillation), and may offer superior calibration capabilities to other imaging techniques. The interferometer has been tested in the laboratory under weakly aberrating conditions and at Palomar Observatory under ordinary astronomical observing conditions. This research is based partly on observations obtained at the Hale Telescope. PMID:16353815

  2. 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)

    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

    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.

  3. Partially coherent phase imaging with simultaneous source recovery

    PubMed Central

    Jingshan, Zhong; Tian, Lei; Dauwels, Justin; Waller, Laura

    2014-01-01

    We propose a new method for phase retrieval that uses partially coherent illumination created by any arbitrary source shape in Köhler geometry. Using a stack of defocused intensity images, we recover not only the phase and amplitude of the sample, but also an estimate of the unknown source shape, which describes the spatial coherence of the illumination. Our algorithm uses a Kalman filtering approach which is fast, accurate and robust to noise. The method is experimentally simple and flexible, so should find use in optical, electron, X-ray and other phase imaging systems which employ partially coherent light. We provide an experimental demonstration in an optical microscope with various condenser apertures. PMID:25657890

  4. Implications of a new phase function for autonomous underwater imaging

    NASA Astrophysics Data System (ADS)

    Fournier, G. R.; Sanjuan-Calzado, V.; Trees, C.

    2014-05-01

    Autonomous underwater vehicles do not have sufficient communications bandwidth over long ranges to send back real time images even for monitoring purposes. Autonomous imaging from underwater vehicles will therefore, require realtime imaging system performance prediction in order to ensure that the vehicle can position itself at a range that will allow it to take an image of the scene or target of interest at the required resolution and contrast level. Ideally the inherent optical properties of the surrounding waters should be measured onboard. This may not be feasible or only a restricted set may be measurable. In order to improve the prediction of the imaging performance, a physics-based analytic phase function that could effectively exploit any a priori or in-situ measured parameters would be extremely helpful. Such a new physics-based analytic phase function has been derived and tested against exact scattering codes. Among other features it is sufficiently precise to allow an accurate determination of the backscatter ratio based on an estimate of the mean index of refraction. The new formulation shows clearly why the backscatter ratio, which is the dominant factor in determining imaging range, is insensitive to the inverse power of the size distribution and almost entirely controlled by the mean index of refraction. This new formulation also has a direct application to improve inverse radiative transfer equation (RTE) modeling for estimating inherent optical properties (total absorption and total backscattering) from measured apparent optical properties (ocean color).

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

    Microsoft Academic Search

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

    2003-01-01

    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:

  6. Optical Physics of Imaging and Interferometric Phased Arrays

    E-print Network

    Stafford Withington; George Saklatvala; Michael P. Hobson

    2006-09-12

    Microwave, submillimetre-wave, and far-infrared phased arrays are of considerable importance for astronomy. We consider the behaviour imaging phased arrays and interferometric phased arrays from a functional perspective. It is shown that the average powers, field correlations, power fluctuations, and correlations between power fluctuations at the output ports of an imaging or interferometric phased array can be found once the synthesised reception patterns are known. The reception patterns do not have to be orthogonal or even linearly independent. It is shown that the operation of phased arrays is intimately related to the mathematical theory of frames, and that the theory of frames can be used to determine the degree to which any class of intensity or field distribution can be reconstructed unambiguously from the complex amplitudes of the travelling waves at the output ports. The theory can be used to set up a likelihood function that can, through Fisher information, be used to determine the degree to which a phased array can be used to recover the parameters of a parameterised source. For example, it would be possible to explore the way in which a system, perhaps interferometric, might observe two widely separated regions of the sky simultaneously.

  7. Absorption-Mode Fourier Transform Mass Spectrometry: the Effects of Apodization and Phasing on Modified Protein Spectra

    PubMed Central

    Qi, Yulin; Li, Huilin; Wills, Rebecca H.; Perez-Hurtado, Pilar; Yu, Xiang; Kilgour, David. P. A.; Barrow, Mark P.; Lin, Cheng; O’Connor, Peter B.

    2014-01-01

    The method of phasing broadband FT-ICR spectra allows plotting the spectra in the absorption-mode; this new approach significantly improves the quality of the data at no extra cost. Herein, an internal calibration method for calculating the phase function has been developed, and successfully applied to the top-down spectra of modified proteins, where the peak intensities vary by >100×. The result shows that the use of absorption-mode spectra allows more peaks to be discerned within the recorded data, and this can reveal much greater information about the protein and modifications under investigation. In addition, noise and harmonic peaks can be assigned immediately in the absorption-mode. PMID:23568027

  8. Fourier transform spectral imaging microscopy (FT-SIM) and scanning Raman microscopy for the detection of indoor common contaminants on the surface of dental implants.

    PubMed

    Lutin, Anna; Bulatov, Valery; Jadwat, Yusuf; Wood, Neil H; Feller, Liviu; Schechter, Israel

    2015-03-01

    Endosteal dental implants are used routinely with high success rates to rehabilitate the integrity of the dentition. However if implant surfaces become contaminated by foreign material, osseointegration may not occur and the dental implant will fail because of the lack of mechanical stability. Detection and characterization of dental implant surface contaminants is a difficult task. In this article we investigate the application of several spectral microscopy methods to detect airborne contaminants on dental implant surfaces. We found that Fourier Transform Spectral Imaging Microscopy (FT-SIM) and scanning Raman microscopy provided the most useful information. Some implants possess weak and homogeneous auto-fluorescence and are best analyzed using FT-SIM methods, while others are Raman inactive and can be analyzed using scanning Raman microscopy. PMID:25618702

  9. Motionless electromagnetic phase stepping versus mechanical phase stepping in x-ray phase-contrast imaging with a compact source.

    PubMed

    Harmon, Katherine J; Miao, Houxun; Gomella, Andrew A; Bennett, Eric E; Foster, Barbara A; Bhandarkar, Priya; Wen, Han

    2015-04-21

    X-ray phase contrast imaging based on grating interferometers detects the refractive index distribution of an object without relying on radiation attenuation, thereby having the potential for reduced radiation absorption. These techniques belong to the broader category of optical wavefront measurement, which requires stepping the phase of the interference pattern to obtain a pixel-wise map of the phase distortion of the wavefront. While phase stepping traditionally involves mechanical scanning of a grating or mirror, we developed electromagnetic phase stepping (EPS) for imaging with compact sources to obviate the need for mechanical movement. In EPS a solenoid coil is placed outside the x-ray tube to shift its focal spot with a magnetic field, causing a relative movement between the projection of the sample and the interference pattern in the image. Here we present two embodiments of this method. We verified experimentally that electromagnetic and mechanical phase stepping give the same results and attain the same signal-to-noise ratios under the same radiation dose. We found that the relative changes of interference fringe visibility were within 3.0% when the x-ray focal spot was shifted by up to 1.0?mm in either direction. We conclude that when using x-ray tube sources, EPS is an effective means of phase stepping without the need for mechanical movement. PMID:25803511

  10. Motionless electromagnetic phase stepping versus mechanical phase stepping in x-ray phase-contrast imaging with a compact source

    NASA Astrophysics Data System (ADS)

    Harmon, Katherine J.; Miao, Houxun; Gomella, Andrew A.; Bennett, Eric E.; Foster, Barbara A.; Bhandarkar, Priya; Wen, Han

    2015-04-01

    X-ray phase contrast imaging based on grating interferometers detects the refractive index distribution of an object without relying on radiation attenuation, thereby having the potential for reduced radiation absorption. These techniques belong to the broader category of optical wavefront measurement, which requires stepping the phase of the interference pattern to obtain a pixel-wise map of the phase distortion of the wavefront. While phase stepping traditionally involves mechanical scanning of a grating or mirror, we developed electromagnetic phase stepping (EPS) for imaging with compact sources to obviate the need for mechanical movement. In EPS a solenoid coil is placed outside the x-ray tube to shift its focal spot with a magnetic field, causing a relative movement between the projection of the sample and the interference pattern in the image. Here we present two embodiments of this method. We verified experimentally that electromagnetic and mechanical phase stepping give the same results and attain the same signal-to-noise ratios under the same radiation dose. We found that the relative changes of interference fringe visibility were within 3.0% when the x-ray focal spot was shifted by up to 1.0?mm in either direction. We conclude that when using x-ray tube sources, EPS is an effective means of phase stepping without the need for mechanical movement.

  11. Phase correction for collision model analysis and enhanced resolving power of fourier transform ion cyclotron resonance mass spectra.

    PubMed

    Vining, B A; Bossio, R E; Marshall, A G

    1999-01-15

    Phase correction of FT-ICR data yields an absorption spectrum that offers a gain by up to a factor of 2 in mass resolving power (at half-maximum peak height), compared to conventional magnitude-mode display. That improvement is equivalent to doubling the applied magnetic field strength, without loss in signal-to-noise (S/N) ratio, provided that the time-domain data are padded with an equal number of zeroes before FFT. Our simple, visual, user-interactive algorithm quickly corrects for zero-order and first-order variation of phase with frequency. We find that the theoretical mass resolving power enhancement for pressure-limited absorption-mode over magnitude-mode line shape depends on the collision mechanism: factor of 1.40 for hard sphere vs 3(1/2) for Langevin (ion: induced dipole). Thus, the experimental enhancement in mass resolving power (factor of 1.43 +/- 0.09) for isotopically resolved peaks in the FT-ICR mass spectra of electrosprayed bovine carbonic anhydrase (approximately 29 kDa) directly supports the hard-sphere collision model. Optimal implementation of phasing requires the following: (a) a delay between excitation and detection of less than half of one sampling interval to avoid baseline "roll" and Gibb's oscillations; (b) accurate analog-to-digital conversion; (c) a sufficiently long acquisition period to yield several data points per absorption-mode peak width at half-maximum peak height; and (d) avoidance of FT-ICR apodization functions (e.g., Hamming and Hanning) that suppress the initial time-domain data. Pulsed single-frequency excitation (duration much less than the reciprocal of the Nyquist bandwidth) can eliminate higher than first-order variation of phase with frequency. Phased FT-ICR spectra should prove especially desirable for analysis of complex mixtures, for resolving isotopic distributions in electrosprayed multiply charged macromolecules and for characterizing ion collisions (and thus ion size and shape). PMID:9949733

  12. Fourier methods for biosequence analysis.

    PubMed Central

    Benson, D C

    1990-01-01

    Novel methods are discussed for using fast Fourier transforms for DNA or protein sequence comparison. These methods are also intended as a contribution to the more general computer science problem of text search. These methods extend the capabilities of previous FFT methods and show that these methods are capable of considerable refinement. In particular, novel methods are given which (1) enable the detection of clusters of matching letters, (2) facilitate the insertion of gaps to enhance sequence similarity, and (3) accommodate to varying densities of letters in the input sequences. These methods use Fourier analysis in two distinct ways. (1) Fast Fourier transforms are used to facilitate rapid computation. (2) Fourier expansions are used to form an 'image' of the sequence comparison. PMID:2243777

  13. Image fusion scheme for differential phase contrast mammography

    NASA Astrophysics Data System (ADS)

    Wang, Z.; Clavijo, C. A.; Roessl, E.; van Stevendaal, U.; Koehler, T.; Hauser, N.; Stampanoni, M.

    2013-07-01

    Latest progresses in breast imaging using differential phase contrast technique pose the question how to fuse multiple information (yielded by the absorption, differential phase, and scattering signals) into a single, but more informative image for clinical diagnosis and evaluation. In this work, we propose an image fusion scheme based on the multiple-resolution (MR) framework. The three signals are first transformed into multiple bands presenting information at different frequency and then a two-step processing follows: section 3.2 an intra-band processing enhances the local signal-to-noise ratio using a novel noise estimation method and context modeling; section 3.3 an inter-band processing weights each band by considering their characteristics and contributions, as well as suppressing the global noise level. The fused image, which looks similar to conventional mammogram but with significantly enhanced detail features, is then reconstructed by inverse transform. This fused image is compatible with clinical settings and enables the radiologists to use their years of diagnosis experiences in mammography.

  14. Parallel phase-sensitive three-dimensional imaging camera

    DOEpatents

    Smithpeter, Colin L. (Albuquerque, NM); Hoover, Eddie R. (Sandia Park, NM); Pain, Bedabrata (Los Angeles, CA); Hancock, Bruce R. (Altadena, CA); Nellums, Robert O. (Albuquerque, NM)

    2007-09-25

    An apparatus is disclosed for generating a three-dimensional (3-D) image of a scene illuminated by a pulsed light source (e.g. a laser or light-emitting diode). The apparatus, referred to as a phase-sensitive 3-D imaging camera utilizes a two-dimensional (2-D) array of photodetectors to receive light that is reflected or scattered from the scene and processes an electrical output signal from each photodetector in the 2-D array in parallel using multiple modulators, each having inputs of the photodetector output signal and a reference signal, with the reference signal provided to each modulator having a different phase delay. The output from each modulator is provided to a computational unit which can be used to generate intensity and range information for use in generating a 3-D image of the scene. The 3-D camera is capable of generating a 3-D image using a single pulse of light, or alternately can be used to generate subsequent 3-D images with each additional pulse of light.

  15. A grating-based single-shot x-ray phase contrast and diffraction method for in vivo imaging

    SciTech Connect

    Bennett, Eric E.; Kopace, Rael; Stein, Ashley F.; Wen Han [National Heart, Lung, and Blood Institute, National Institutes of Health, Imaging Physics Section, Translational Medicine Branch, 10 Center Drive, MSC 1061, Bethesda, Maryland 20892 (United States)

    2010-11-15

    Purpose: The purpose of this study is to develop a single-shot version of the grating-based phase contrast x-ray imaging method and demonstrate its capability of in vivo animal imaging. Here, the authors describe the principle and experimental results. They show the source of artifacts in the phase contrast signal and optimal designs that minimize them. They also discuss its current limitations and ways to overcome them. Methods: A single lead grid was inserted midway between an x-ray tube and an x-ray camera in the planar radiography setting. The grid acted as a transmission grating and cast periodic dark fringes on the camera. The camera had sufficient spatial resolution to resolve the fringes. Refraction and diffraction in the imaged object manifested as position shifts and amplitude attenuation of the fringes, respectively. In order to quantify these changes precisely without imposing a fixed geometric relationship between the camera pixel array and the fringes, a spatial harmonic method in the Fourier domain was developed. The level of the differential phase (refraction) contrast as a function of hardware specifications and device geometry was derived and used to guide the optimal placement of the grid and object. Both ex vivo and in vivo images of rodent extremities were collected to demonstrate the capability of the method. The exposure time using a 50 W tube was 28 s. Results: Differential phase contrast images of glass beads acquired at various grid and object positions confirmed theoretical predictions of how phase contrast and extraneous artifacts vary with the device geometry. In anesthetized rats, a single exposure yielded artifact-free images of absorption, differential phase contrast, and diffraction. Differential phase contrast was strongest at bone-soft tissue interfaces, while diffraction was strongest in bone. Conclusions: The spatial harmonic method allowed us to obtain absorption, differential phase contrast, and diffraction images, all from a single raw image and is feasible in live animals. Because the sensitivity of the method scales with the density of the gratings, custom microfabricated gratings should be superior to off-the-shelf lead grids.

  16. Image Processing for AN Amplitude and Phase Acoustic Microscope.

    NASA Astrophysics Data System (ADS)

    Reinholdtsen, Paul Andrew

    1989-09-01

    We have built a scanning acoustic microscope (SAM) operating in the 3 to 10 MHz range that measures both amplitude and phase reliably and accurately. It has been primarily used in non-destructive evaluation (NDE) of machined parts, composite materials, etc. for the presence of cracks, voids, and delaminations. Most SAMs measure amplitude only; by measuring phase as well, we can carry out quantitative NDE and image processing that can not be done with amplitude or phase alone. We have demonstrated several image processing applications that use amplitude and phase measurements; such as transducer characterization, material reflectance function measurements using V(z) inversion, and thin film/delamination thickness measurements. The transverse and depth resolution of the microscope can be enhanced by numerically post processing the digitized images. The enhanced depth resolution has been applied to measuring the profile of deep trenches (2 mm wide by 5 mm deep) designed as scale models of integrated circuit capacitors (2.4 ?m by 6 ?m). This technique could also be applied to a system scaled down in wavelength to characterize ICs. Such a system would use an acoustic microscope operating at higher frequencies or a confocal scanning optical microscope (CSOM) that measures amplitude and phase. Even better depth resolution can be obtained by numerically combining images taken at several different frequencies. The resulting image has a greater range of coverage in the spatial frequency domain in the depth direction than does a single frequency image. This technique could also be implemented in a CSOM using illumination from lasers operating at different wavelengths. The methods has the potential of sharpening the depth response of an optical microscope by a factor of two from what is currently possible. The ability of the acoustic microscope to measure phase allows a novel application for acoustic microscopes: the measurement of capillary waves. Capillary waves are short wavelength ripples on the surface of water. The presence of capillary waves initiates the buildup of larger waves via wind interaction. A measurement of their damping could thus give an indication of weather changes. (Abstract shortened with permission of author.).

  17. Structural and functional imaging of the human and small animal eyes using ultrahigh speed Fourier domain optical coherence tomography

    E-print Network

    Choi, Woo Jhon

    2014-01-01

    Optical coherence tomography (OCT) is a non-invasive optical imaging technique that allows the three-dimensional structure of biological tissue to be visualized with micrometer resolution. In ophthalmology OCT has the ...

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

    Microsoft Academic Search

    Borislav Vasic

    2011-01-01

    Using numerical simulations, we investigate the realization of self-focusing media using two-dimensional graded photonic crystals and their applications for imaging and non-imaging purposes. The two-dimensional graded photonic crystals consist of spatially varying cylindrical holes drilled in a dielectric host. By controlling the gradient of the refractive index and the thickness of the self-focusing medium, it is possible to obtain either

  19. Phase calibration of imaging radar polarimeter Stokes matrices

    NASA Technical Reports Server (NTRS)

    Zebker, Howard A.; Lou, Yunling

    1990-01-01

    It is shown that the Stokes matrices measured by an imaging radar polarimeter provide enough information for the accurate phase calibration of the observed polarimetric characteristics of a surface. This is important because it allows the data to be reduced in volume in an operational synthetic aperture radar correlator with no prior knowledge of the conditions at the surface, and the end user can later select the particular region where he or she is comfortable with making an assumption regarding the relative phases of the hh and vv signals. No ground calibration equipment is necessary, as all important parameters are derived from the data themselves.

  20. Fourier transform infrared imaging and microscopy studies of Pinus radiata pulps regarding the simultaneous saccharification and fermentation process.

    PubMed

    Castillo, Rosario Del P; Araya, Juan; Troncoso, Eduardo; Vinet, Silenne; Freer, Juanita

    2015-03-25

    The distribution and chemical patterns of lignocellulosic components at microscopic scale and their effect on the simultaneous saccharification and fermentation process (SSF) in the production of bioethanol from Pinus radiata pulps were analyzed by the application of diverse microscopical techniques, including scanning electronic microscopy (SEM), confocal laser scanning microscopy (CLSM) and attenuated total reflectance (ATR) - Fourier transform infrared microspectroscopy. This last technique was accompanied with multivariate methods, including principal component analysis (PCA) and multivariate curve resolution with alternating least squares (MCR-ALS) to evaluate the distribution patterns and to generate pure spectra of the lignocellulosic components of fibers. The results indicate that the information obtained by the techniques is complementary (ultrastructure, confocality and chemical characterization) and that the distribution of components affects the SSF yield, identifying lignin coalescence droplets as a characteristic factor to increase the SSF yield. Therefore, multivariate analysis of the infrared spectra enabled the in situ identification of the cellulose, lignin and lignin-carbohydrates arrangements. These techniques could be used to investigate the lignocellulosic components distribution and consequently their recalcitrance in many applications where minimal sample manipulation and microscale chemical information is required. PMID:25732688

  1. Doppler streak mode Fourier domain optical coherence tomography

    NASA Astrophysics Data System (ADS)

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

    2012-01-01

    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.

  2. A Phased Array Coil for Human Cardiac Imaging

    PubMed Central

    Constantinides, Chris D.; Westgate, Charles R.; O'Dell, Walter G.; Zerhouni, Elias A.; McVeigh, Elliot R.

    2007-01-01

    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. PMID:7674903

  3. Quantitative phase imaging using a deep UV LED source.

    PubMed

    Singh, Alok Kumar; Faridian, Ahmad; Gao, Peng; Pedrini, Giancarlo; Osten, Wolfgang

    2014-06-15

    We propose a method for high resolution phase imaging of biological and non-biological samples using an incoherent deep ultraviolet (DUV) LED source. The diffraction pattern of the object wave is recorded at different axial planes and the phase is retrieved by propagation of the angular spectrum. To maintain enough light intensity, we avoided using a pinhole or spectral filter for increasing the coherence of the DUV LED source. This makes the setup very simple and cost effective. The short wavelength (285 nm) of the DUV light, tuned to the absorption peak of the biological samples, allows simultaneously high resolution and high contrast images. The experimental results are presented to verify this principle. PMID:24978513

  4. Automatic detection of ridges in lunar images using phase symmetry and phase congruency

    NASA Astrophysics Data System (ADS)

    Micheal, Anto A.; Vani, K.; Sanjeevi, S.

    2014-12-01

    Lunar surface exploration is increasing rapidly. These exploring satellites provide a large number of high resolution images containing topographical information. The topographical information in lunar surface are craters, ridges, mountains and grabens. Extracting this topographical information manually is time-consuming. Hence, an automatic feature extraction is favored. This paper presents a novel approach using image processing techniques to automatically detect ridges in lunar images. The approaches adopted for this development includes phase symmetry, phase congruency and morphological operations to automatically detect significant ridges. The phase symmetry extracts symmetry features with discontinuities, phase congruency extracts features lying in low contrast regions and morphological operations such as thinning and pruning are used to obtain significant ridges. The proposed novel approach experiments on a test set of different regions. These different region images are obtained from different sensors (LROC, Selene and Clementine) having different spatial resolution and illumination variation. The results obtained are compared with the plan curvature method; and they are evaluated based on true and false detection of ridge pixels. Irrespective of illumination variation and spatial resolution, the proposed approach provides better results than the plan curvature method and its detection rate is approximately 92%.

  5. Fourier analysis of the imaging characteristics of a CMOS active pixel detector for mammography by using a linearization method

    NASA Astrophysics Data System (ADS)

    Han, Jong Chul; Yun, Seungman; Youn, Hanbean; Kam, Soohwa; Cho, Seungryong; Achterkirchen, Thorsten G.; Kim, Ho Kyung

    2014-09-01

    Active pixel design using the complementary metal-oxide-semiconductor (CMOS) process is a compelling solution for use in X-ray imaging detectors because of its excellent electronic noise characteristics. We have investigated the imaging performance of a CMOS active pixel photodiode array coupled to a granular phosphor through a fiber-optic faceplate for mammographic applications. The imaging performance included the modulation-transfer function (MTF), noise-power spectrum (NPS), and detective quantum efficiency (DQE). Because we observed a nonlinear detector response at low exposures, we used the linearization method for the analysis of the DQE. The linearization method uses the images obtained at detector input, which are converted from those obtained at detector output by using the inverse of the detector response. Compared to the conventional method, the linearization method provided almost the same MTF and a slightly lower normalized NPS. However, the difference between the DQE results obtained by using the two methods was significant. We claim that the conventional DQE analysis of a detector having a nonlinear response characteristic can yield wrong results. Under the standard mammographic imaging condition, we obtained a DQE performance that was competitive with the performances of conventional flat-panel mammography detectors. We believe that the CMOS detector investigated in this study can be successfully used for mammography.

  6. Phase contrast in Simultaneous Topography and Recognition imaging.

    PubMed

    Fuss, M C; Sahagún, E; Köber, M; Briones, F; Luna, M; Sáenz, J J

    2009-08-01

    The operation of a force microscope in Simultaneous Topography and Recognition (TREC) imaging mode is analyzed by means of numerical simulations. Both topography and recognition signals are analyzed by using a worm-like chain force as the specific interaction between the functionalized tip probe and the sample. The special feedback mechanism in this mode is shown to couple the phase signal to the presence of molecular recognition interactions even in absence of dissipation. PMID:19523768

  7. Efficient phase contrast imaging in STEM using a pixelated detector. Part II: Optimisation of imaging conditions.

    PubMed

    Yang, Hao; Pennycook, Timothy J; Nellist, Peter D

    2015-04-01

    In Part I of this series of two papers, we demonstrated the formation of a high efficiency phase-contrast image at atomic resolution using a pixelated detector in the scanning transmission electron microscope (STEM) with ptychography. In this paper we explore the technique more quantitatively using theory and simulations. Compared to other STEM phase contrast modes including annular bright field (ABF) and differential phase contrast (DPC), we show that the ptychographic phase reconstruction method using pixelated detectors offers the highest contrast transfer efficiency and superior low dose performance. Applying the ptychographic reconstruction method to DPC segmented detectors also improves the detector contrast transfer and results in less noisy images than DPC images formed using difference signals. We also find that using a minimum array of 16×16 pixels is sufficient to provide the highest signal-to-noise ratio (SNR) for imaging beam sensitive weak phase objects. Finally, the convergence angle can be adjusted to enhance the contrast transfer based on the spatial frequencies of the specimen under study. PMID:25481091

  8. Improved Phased Array Imaging of a Model Jet

    NASA Technical Reports Server (NTRS)

    Dougherty, Robert P.; Podboy, Gary G.

    2010-01-01

    An advanced phased array system, OptiNav Array 48, and a new deconvolution algorithm, TIDY, have been used to make octave band images of supersonic and subsonic jet noise produced by the NASA Glenn Small Hot Jet Acoustic Rig (SHJAR). The results are much more detailed than previous jet noise images. Shock cell structures and the production of screech in an underexpanded supersonic jet are observed directly. Some trends are similar to observations using spherical and elliptic mirrors that partially informed the two-source model of jet noise, but the radial distribution of high frequency noise near the nozzle appears to differ from expectations of this model. The beamforming approach has been validated by agreement between the integrated image results and the conventional microphone data.

  9. An active co-phasing imaging testbed with segmented mirrors

    NASA Astrophysics Data System (ADS)

    Zhao, Weirui; Cao, Genrui

    2011-06-01

    An active co-phasing imaging testbed with high accurate optical adjustment and control in nanometer scale was set up to validate the algorithms of piston and tip-tilt error sensing and real-time adjusting. Modularization design was adopted. The primary mirror was spherical and divided into three sub-mirrors. One of them was fixed and worked as reference segment, the others were adjustable respectively related to the fixed segment in three freedoms (piston, tip and tilt) by using sensitive micro-displacement actuators in the range of 15mm with a resolution of 3nm. The method of twodimension dispersed fringe analysis was used to sense the piston error between the adjacent segments in the range of 200?m with a repeatability of 2nm. And the tip-tilt error was gained with the method of centroid sensing. Co-phasing image could be realized by correcting the errors measured above with the sensitive micro-displacement actuators driven by a computer. The process of co-phasing error sensing and correcting could be monitored in real time by a scrutiny module set in this testbed. A FISBA interferometer was introduced to evaluate the co-phasing performance, and finally a total residual surface error of about 50nm rms was achieved.

  10. Implementation of a phase array diffuse optical tomographic imager

    NASA Astrophysics Data System (ADS)

    Rajan, K.; Vijayakumar, V.; Biswas, Samir Kumar; Vasu, R. M.

    2008-08-01

    Diffuse optical tomography (DOT) using near-infrared (NIR) light is a promising tool for noninvasive imaging of deep tissue. This technique is capable of quantitative reconstructions of absorption coefficient inhomogeneities of tissue. The motivation for reconstructing the optical property variation is that it, and, in particular, the absorption coefficient variation, can be used to diagnose different metabolic and disease states of tissue. In DOT, like any other medical imaging modality, the aim is to produce a reconstruction with good spatial resolution and accuracy from noisy measurements. We study the performance of a phase array system for detection of optical inhomogeneities in tissue. The light transport through a tissue is diffusive in nature and can be modeled using diffusion equation if the optical parameters of the inhomogeneity are close to the optical properties of the background. The amplitude cancellation method that uses dual out-of-phase sources (phase array) can detect and locate small objects in turbid medium. The inverse problem is solved using model based iterative image reconstruction. Diffusion equation is solved using finite element method for providing the forward model for photon transport. The solution of the forward problem is used for computing the Jacobian and the simultaneous equation is solved using conjugate gradient search. The simulation studies have been carried out and the results show that a phase array system can resolve inhomogeneities with sizes of 5mm when the absorption coefficient of the inhomogeneity is twice that of the background tissue. To validate this result, a prototype model for performing a dual-source system has been developed. Experiments are carried out by inserting an inhomogeneity of high optical absorption coefficient in an otherwise homogeneous phantom while keeping the scattering coefficient same. The high frequency (100MHz) modulated dual out-of-phase laser source light is propagated through the phantom. The interference of these sources creates an amplitude null and a phase shift of 180° along a plane between the two sources with a homogeneous object. A solid resin phantom with inhomogeneities simulating the tumor is used in our experiment. The amplitude and phase changes are found to be disturbed by the presence of the inhomogeneity in the object. The experimental data (amplitude and the phase measured at the detector) are used for reconstruction. The results show that the method is able to detect multiple inhomogeneities with sizes of 4mm. The localization error for a 5 mm inhomogeneity is found to be approximately 1mm.

  11. Photothermal heterodyne phase imaging of gold seed and germanium nanowire

    NASA Astrophysics Data System (ADS)

    Jung, Yookyung; Lin, Nan; Yang, Chen; Cheng, Ji-Xin

    2010-02-01

    Photothermal heterodyne imaging has demonstrated a high sensitivity of seeing single metallic nanoparticles of diameter down to 5 nm. However, rare attention has been paid to the phase of the photothermal heterodyne signal relative to that of the modulated pump beam. We show that the phase of the photothermal heterodyne signal from semiconducting nanomaterials such as silicon and germanium nanowires is around 0 degree, while that from metallic nanomaterials such as silver and gold nanoparticles (NPs) is around 180 degrees. Using this property we have been able to distinguish gold seeds from germanium nanowire (GeNW) body in a label-free and contact-free manner. A theoretical model based on light scattering by a fluctuating dielectric material was used to explain the origin of different phases in the photothermal heterodyne signal.

  12. Experience with 800 x 800 virtual phase and 500 x 500 three-phase CCD imagers

    NASA Technical Reports Server (NTRS)

    Hlivak, R. J.; Henry, J. P.; Pilcher, C. B.

    1984-01-01

    A description of the Galileo/Institute for Astronomy charge-coupled device (CCD) imaging system and its initial operation has been presented previously. Originally designed to operate a 500 x 500 backside illuminated three-phase CCD, the system has been modified to allow use of either the 500 x 500 sensor or the TI 800 x 800 virtual phase CCD. The modifications for the operation of the virtual phase CCD and current system performance with each type of sensor are discussed. A description is given of the implementation of various techniques discovered at the Jet Propulsion Laboratory that improve imager performance. These techniques include tri-level clocking of the virtual phase CCD to eliminate spurious charge generation in the serial register, the use of ultraviolet light flood with the backside thinned 500 x 500 three-phase device to dramatically improve the quantum efficiency in the blue, and the practical elimination of deferred charge in the three-phase device. Results of astronomical observations with each sensor are presented.

  13. Detection of microscopic particles present as contaminants in latent fingerprints by means of synchrotron radiation-based Fourier transform infra-red micro-imaging.

    PubMed

    Banas, A; Banas, K; Breese, M B H; Loke, J; Heng Teo, B; Lim, S K

    2012-08-01

    Synchrotron radiation-based Fourier transform infra-red (SR-FTIR) micro-imaging has been developed as a rapid, direct and non-destructive technique. This method, taking advantage of the high brightness and small effective source size of synchrotron light, is capable of exploring the molecular chemistry within the microstructures of microscopic particles without their destruction at high spatial resolutions. This is in contrast to traditional "wet" chemical methods, which, during processing for analysis, often caused destruction of the original samples. In the present study, we demonstrate the potential of SR-FTIR micro-imaging as an effective way to accurately identify microscopic particles deposited within latent fingerprints. These particles are present from residual amounts of materials left on a person's fingers after handling such materials. Fingerprints contaminated with various types of powders, creams, medications and high explosive materials (3-nitrooxy-2,2-bis(nitrooxymethyl)propyl nitrate (PETN), 1,3,5-trinitro-1,3,5-triazinane (RDX), 2-methyl-1,3,5-trinitrobenzene (TNT)) deposited on various - daily used - substrates have been analysed herein without any further sample preparation. A non-destructive method for the transfer of contaminated fingerprints from hard-to-reach areas of the substrates to the place of analysis is also presented. This method could have a significant impact on forensic science and could dramatically enhance the amount of information that can be obtained from the study of fingerprints. PMID:22693711

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

    NASA Technical Reports Server (NTRS)

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

    1993-01-01

    Fourier transform-infrared (FTIR) spectroscopy was used to examine films representative of stratospheric sulfuric acid aerosols. Thin films of sulfuric acid were formed in situ by the condensed phase reaction of SO3 with H2O. FTIR spectra show that the sulfuric acid films absorb water while cooling in the presence of water vapor. Using stratospheric water pressures, the most dilute solutions observed were greater than 40 wt % before simultaneous ice formation and sulfuric acid freezing occurred. FTIR spectra also revealed that the sulfuric acid films crystallized mainly as sulfuric acid tetrahydrate (SAT). Crystallization occurred either when the composition was about 60 wt% H2SO4 or after ice formed on the films at temperatures 1-4 K below the ice frost point. Finally, we determined that the melting point for SAT depended on the background water pressure and was 216-219 K in the presence of 4 x 10(exp -4) Torr H2O. Our results suggest that once frozen, sulfuric acid aerosols in the stratosphere are likely to melt at these temperatures, 30 K colder than previously thought.

  15. On-line vapor-phase generation followed by Fourier-transform infrared spectrometry for the quantitative analysis of water-soluble penicillin G in pharmaceutical formulations.

    PubMed

    Sadeghi, Mahdi; Zeeb, Mohsen; Kalaee, Mohammad R

    2010-01-01

    The combination of vapor-phase generation (VPG) and Fourier-transform infrared (FTIR) spectrometry was performed as an alternative analytical technique for the determination of water-soluble penicillin G (PENG). Samples were transferred into a heated reactor, and a potassium iodate solution was injected into the reactor. Carbon monoxide (CO) generated under these conditions was carried via a N(2) gas carrier stream inside the IR gas cell, and the corresponding FTIR spectra were continuously recorded as a function of time. Analytical measurements were made using the maximum absorbance of the CO band at 2170 +/- 4 cm(-1). Various factors influencing the analytical signals were evaluated and selected. The figures of merit of the proposed method involve a linear calibration curve over the range of 3 to 320 mg L(-1), a limit of detection of 0.5 mg L(-1) and a precision of 2.6%. The method was successfully applied to PENG determination in pharmaceutical preparations. PMID:20467133

  16. Phase-unwrapping algorithm for images with high noise content based on a local histogram

    NASA Astrophysics Data System (ADS)

    Meneses, Jaime; Gharbi, Tijani; Humbert, Philippe

    2005-03-01

    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 pixels are segmented between interfringe and fringe boundary areas by use of a local histogram of a wrapped phase. The algorithm has been used successfully to unwrap phase images generated in a three-dimensional shape measurement for noninvasive quantification of human skin structure in dermatology, cosmetology, and plastic surgery.

  17. Noninvasive Imaging of the Foveal Avascular Zone with High-Speed, Phase-Variance Optical Coherence Tomography

    PubMed Central

    Fingler, Jeff; Zawadzki, Robert J.; Park, Susanna S.; Morse, Lawrence S.; Schwartz, Daniel M.; Fraser, Scott E.; Werner, John S.

    2012-01-01

    Purpose. To demonstrate the application of phase-variance optical coherence tomography (pvOCT) for contrast agent–free in vivo imaging of volumetric retinal microcirculation in the human foveal region and for extraction of foveal avascular zone dimensions. Methods. A custom-built, high-speed Fourier-domain OCT retinal imaging system was used to image retinas of two healthy subjects and eight diabetic patients. Through the acquisition of multiple B-scans for each scan location, phase differences between consecutive scans were extracted and used for phase-variance contrast, identifying motion signals from within blood vessels and capillaries. The en face projection view of the inner retinal layers segmented out from volumetric pvOCT data sets allowed visualization of a perfusion network with the foveal avascular zone (FAZ). In addition, the authors presented 2D retinal perfusion maps with pseudo color-coded depth positions of capillaries. Results. Retinal vascular imaging with pvOCT provides accurate measurements of the FAZ area and its morphology and a volumetric perfusion map of microcapillaries. In this study using two images from each fundus fluorescein angiography (FA) and pvOCT, the measured average areas of the FAZ from two healthy subjects were below 0.22 mm2, and each of eight diabetic patients had an enlarged FAZ area, larger than 0.22 mm2. Moreover, the FAZ areas demonstrated a significant correlation (r = 0.91) between measurements from FA and pvOCT. Conclusions. The high-speed pvOCT allows contrast agent–free visualization of capillary networks in the human foveal region that is analogous to fundus FA imaging. This could allow for noninvasive diagnosis and progression monitoring of diabetic retinopathy in clinical settings. PMID:22125275

  18. Cardiac-phase filtering in intracardiac particle image velocimetry

    NASA Astrophysics Data System (ADS)

    Jamison, R. Aidan; Fouras, Andreas; Bryson-Richardson, Robert J.

    2012-03-01

    The ability to accurately measure velocity within the embryonic zebrafish heart, at high spatial and temporal resolution, enables further insight into the effects of hemodynamics on heart development. Unfortunately, currently available techniques are unable to provide the required resolution, both spatial and temporal, for detailed analysis. Advances in imaging hardware are allowing bright field imaging combined with particle image velocimetry to become a viable technique for the broader community at the required spatial and temporal resolutions. While bright field imaging offers the necessary temporal resolution, this approach introduces heart wall artifacts that interfere with accurate velocity measurement. This study presents a technique for cardiac-phase filtering of bright field images to remove the heart wall and improve velocimetry measurements. Velocity measurements were acquired for zebrafish embryos ranging from 3 to 6 days postfertilization. Removal of the heart wall was seen to correct a severe (3-fold) underestimation in velocity measurements obtained without filtering. Additionally, velocimetry measurements were used to quantitatively detect developmental changes in cardiac performance in vivo, investigating both changes in contractile period and maximum velocities present through the ventricular-bulbar valve.

  19. The Geostationary Fourier Transform Spectrometer

    Microsoft Academic Search

    Richard Key; Stanley Sander; Annmarie Eldering; David Rider; Jean-Francois Blavier; Dmitriy Bekker; Yen-Hung Wu; Ken Manatt

    2012-01-01

    The Geostationary Fourier Transform Spectrometer (GeoFTS) is an imaging spectrometer designed for an earth science mission to measure key atmospheric trace gases and process tracers related to climate change and human activity. The GeoFTS instrument is a half meter cube size instrument designed to operate in geostationary orbit as a secondary “hosted” payload on a commercial geostationary satellite mission. The

  20. Automatic Selection of Mask and Arterial Phase Images for Temporally Resolved MR Digital

    E-print Network

    Zabih, Ramin

    X-ray angiography, where image postprocessing has been used frequently to improve vasculatureAutomatic Selection of Mask and Arterial Phase Images for Temporally Resolved MR Digital for selecting arterial phase images and mask images to generate an optimal sum- mary arteriogram. A paired

  1. Generalized formulation of an encryption system based on a joint transform correlator and fractional Fourier transform

    NASA Astrophysics Data System (ADS)

    Vilardy, Juan M.; Torres, Yezid; Millán, María S.; Pérez-Cabré, Elisabet

    2014-12-01

    We propose a generalization of the encryption system based on double random phase encoding (DRPE) and a joint transform correlator (JTC), from the Fourier domain to the fractional Fourier domain (FrFD) by using the fractional Fourier operators, such as the fractional Fourier transform (FrFT), fractional traslation, fractional convolution and fractional correlation. Image encryption systems based on a JTC architecture in the FrFD usually produce low quality decrypted images. In this work, we present two approaches to improve the quality of the decrypted images, which are based on nonlinear processing applied to the encrypted function (that contains the joint fractional power spectrum, JFPS) and the nonzero-order JTC in the FrFD. When the two approaches are combined, the quality of the decrypted image is higher. In addition to the advantages introduced by the implementation of the DRPE using a JTC, we demonstrate that the proposed encryption system in the FrFD preserves the shift-invariance property of the JTC-based encryption system in the Fourier domain, with respect to the lateral displacement of both the key random mask in the decryption process and the retrieval of the primary image. The feasibility of this encryption system is verified and analyzed by computer simulations.

  2. SAR image construction from periodically gapped phase-history data

    NASA Astrophysics Data System (ADS)

    Larsson, Erik G.; Li, Jianwei J.

    2002-08-01

    It is known that high-resolution synthetic aperture radar (SAR) imaging can be cast as a spectral analysis problem, and consequently a number of sophisticated spectral estimation methods have been applied to SAR imaging. These method include the classical Capon method and the closely related Amplitude and Phase Estimation (APES) algorithm. In this paper, we show how Capon and APES can be extended to deal with spectral analysis of periodically gapped (PG) data, i.e. data where samples are missing in a periodic fashion. This problem is highly relevant for SAR imaging with angular diversity since in that case the measured phase-history data matrix contains missing columns. Our extension of Capon and APES is based on a transform that maps a one-dimensional (1D) periodically gapped time-series into a uniformly sampled two-dimensional (2D) data set. We show that the stationarity properties of the 1D signal are left unchanged by the transformation, and as a result the conventional 2D Capon and APES methods can be applied to the transformed data. An associated inverse transform is used to extract the 1D spectral estimate from the 2D one. The new method is computationally and conceptually non-intricate and it does not involve any interpolation of the missing data. Despite its striking simplicity, numerical results indicate that the new method can be a promising tool for SAR imaging with angular diversity as well as for time-series analysis. In SAR applications, the new method may be particularly suitable for accurate imaging of a small region of interest.

  3. Signal Processing Issues in Fourier Transform Spectrometers

    Microsoft Academic Search

    Monson H. Hayes

    2002-01-01

    There are a number of interesting and challenging signal processing problems related to the design of a Fourier Transform Spectrometer (FTS). In this project, we look at a few of these problems in two different types of spectrometers-the Geostationary Imaging Fourier Transform Spectrometer (GIFTS), and a Far Infrared (FIR) FTS. One of the si nal processing challenges in GIFTS is

  4. Isolating stem cells in the inter-follicular epidermis employing synchrotron radiation-based Fourier-transform infrared microspectroscopy and focal plane array imaging.

    PubMed

    Patel, Imran I; Harrison, Wesley J; Kerns, Jemma G; Filik, Jacob; Wehbe, Katia; Carmichael, Paul L; Scott, Andrew D; Philpott, Mike P; Frogley, Mark D; Cinque, Gianfelice; Martin, Francis L

    2012-10-01

    Normal function and physiology of the epidermis is maintained by the regenerative capacity of this tissue via adult stem cells (SCs). However, definitive identifying markers for SCs remain elusive. Infrared (IR) spectroscopy exploits the ability of cellular biomolecules to absorb in the mid-IR region (? = 2.5-25 ?m), detecting vibrational transitions of chemical bonds. In this study, we exploited the cell's inherent biochemical composition to discriminate SCs of the inter-follicular skin epidermis based on IR-derived markers. Paraffin-embedded samples of human scalp skin (n = 4) were obtained, and 10-?m thick sections were mounted for IR spectroscopy. Samples were interrogated in transmission mode using synchrotron radiation-based Fourier-transform IR (FTIR) microspectroscopy (15 × 15 ?m) and also imaged employing globar-source FTIR focal plane array (FPA) imaging (5.4 × 5.4 ?m). Dependent on the location of derived spectra, wavenumber-absorbance/intensity relationships were examined using unsupervised principal component analysis. This approach showed clear separation and spectral differences dependent on cell type. Spectral biomarkers concurrently associated with segregation of SCs, transit-amplifying cells and terminally-differentiated cells of epidermis were primarily PO(2)(-) vibrational modes (1,225 and 1,080 cm(-1)), related to DNA conformational alterations. FPA imaging coupled with hierarchical cluster analysis also indicated the presence of specific basal layer cells potentially originating from the follicular bulge, suggested by co-clustering of spectra. This study highlights PO (2) (-) vibrational modes as potential putative SC markers. PMID:22945554

  5. RESTORATION OF WEAK PHASE-CONTRAST IMAGES RECORDED WITH A HIGH DEGREE OF DEFOCUS: THE"TWIN IMAGE" PROBLEM ASSOCIATED WITH CTF CORRECTION

    SciTech Connect

    Downing, Kenneth H.; Glaeser, Robert M.

    2008-03-28

    Relatively large values of objective-lens defocus must normally be used to produce detectable levels of image contrast for unstained biological specimens, which are generally weak phase objects. As a result, a subsequent restoration operation must be used to correct for oscillations in the contrast transfer function (CTF) at higher resolution. Currently used methods of CTF-correction assume the ideal case in which Friedel mates in the scattered wave have contributed pairs of Fourier components that overlap with one another in the image plane. This"ideal" situation may be only poorly satisfied, or not satisfied at all, as the particle size gets smaller, the defocus value gets larger, and the resolution gets higher. We have therefore investigated whether currently used methods of CTF correction are also effective in restoring the single-sideband image information that becomes displaced (delocalized) by half (or more) the diameter of a particle of finite size. Computer simulations are used to show that restoration either by"phase flipping" or by multiplying by the CTF recovers only about half of the delocalized information. The other half of the delocalized information goes into a doubly defocused"twin" image of the type produced during optical reconstruction of an in-line hologram. Restoration with a Wiener filter is effective in recovering the delocalized information only when the signal-to-noise ratio (S/N) is orders of magnitude higher than that which exists in low-dose images of biological specimens, in which case the Wiener filter approaches division by the CTF (i.e. the formal inverse). For realistic values of the S/N, however, the"twin image" problem seenwith a Wiener filter is very similar to that seen when either phase flipping or multiplying by the CTF are used for restoration. The results of these simulations suggest that CTF correction is a poor alternative to using a Zernike-type phase plate when imaging biological specimens, in which case the images can be recorded in a close-to-focus condition, and delocalization of high-resolution information is thus minimized.

  6. Phase and fluorescence imaging by combination of digital holographic microscopy and fluorescence microscopy

    NASA Astrophysics Data System (ADS)

    Quan, Xiangyu; Nitta, Kouichi; Matoba, Osamu; Xia, Peng; Awatsuji, Yasuhiro

    2015-03-01

    Hybrid digital holographic microscopy that combines fluorescence microscopy and digital holographic microscopy into a single system for biological applications is proposed. In the proposed system, a phase image and a fluorescence image can be obtained simultaneously by selecting the different wavelengths of the fluorescent light and the phase measurement. Especially for biological applications, the cell structure can be obtained by the phase imaging based on digital holography and nucleus of the cell can be obtained by the fluorescence imaging. The measurement of fluorescence beads and egera densa presented the feasibility of simultaneous detection of both a phase image and a fluorescence image.

  7. Fourier Transforms, Fourier Series and the FFT

    NSDL National Science Digital Library

    Lisette de Pillis

    The goal of this module is to give students an understanding of the one-dimensional Fourier Transform, both mathematically and computationally, with a focus on finding periodicity in data. To motivate the study of the Fourier Transform, the students will be presented with certain application areas, such as searching for periodic patterns in CO2 data and differentiating between two sound signals using their power spectra. Students will explore some computational issues and challenges of the Discrete and Fast Fourier Transforms.

  8. Three-phase radionuclide bone imaging in sports medicine

    SciTech Connect

    Rupani, H.D.; Holder, L.E.; Espinola, D.A.; Engin, S.I.

    1985-07-01

    Three-phase radionuclide bone (TPB) imaging was performed on 238 patients with sports-related injuries. A wide variety of lesions was encountered, but the most frequent lesions seen were stress fractures of the lower part of the leg at the junction of the middle and distal thirds of the posterior tibial cortex (42 of 79 lesions). There were no differences in the type, location, or distribution of lesions between males and females or between competitive and noncompetitive athletes. In 110 cases, bone stress lesions were often diagnosed when radiographs were normal, whereas subacute or chronic soft-tissue abnormalities had few specific scintigraphic features. TPB imaging provides significant early diagnostic information about bone stress lesions. Normal examination results (53 cases) exclude underlying osseous pathologic conditions.

  9. Dose and detectability improvements with high energy phase sensitive x-ray imaging in comparison to low energy conventional imaging

    PubMed Central

    Wong, Molly Donovan; Yan, Aimin; Ghani, Muhammad; Li, Yuhua; Fajardo, Laurie; Wu, Xizeng; Liu, Hong

    2014-01-01

    The objective of this study was to demonstrate the potential benefits of using high energy x-rays for phase sensitive breast imaging through a comparison with conventional mammography imaging. We compared images of a contrast-detail (CD) phantom acquired on a prototype phase sensitive x-ray imaging system with images acquired on a commercial flat panel digital mammography unit. The phase contrast images were acquired using a micro-focus x-ray source with a 50 ?m focal spot at 120 kVp and 4.5 mAs, with a magnification factor of 2.46 and a 50 ?m pixel pitch. A phase attenuation duality (PAD)-based phase retrieval algorithm that requires only a single phase contrast image was applied. Conventional digital mammography images were acquired at 27 kVp, 131 mAs and 28 kVp, 54 mAs. For the same radiation dose, both the observer study and SNR/FOM comparisons indicated a large improvement by the phase retrieved image as compared to the clinical system for the larger disk sizes, but the improvement was not enough to detect the smallest disks. Compared to the double dose image acquired with the clinical system, the observer study also indicated that the phase retrieved image provided improved detection capabilities for all disk sizes except the smallest disks. Thus the SNR improvement provided by phase contrast imaging is not yet enough to offset the noise reduction provided by the clinical system at the doubled dose level. However, the potential demonstrated by this study for high energy phase sensitive x-ray imaging to improve lesion detection and reduce radiation dose in mammography warrants further investigation of this technique. PMID:24732108

  10. Improved phase imaging from intensity measurements in multiple planes

    SciTech Connect

    Soto, Marcos; Acosta, Eva

    2007-11-20

    Problems stemming from quantitative phase imaging from intensity measurements play a key role in many fields of physics. Techniques based on the transport of intensity equation require an estimate of the axial derivative of the intensity to invert the problem. Derivation formulas in two adjacent planes are commonly used to experimentally compute the derivative of the irradiance. Here we propose a formula that improves the estimate of the derivative by using a higher number of planes and taking the noisy nature of the measurements into account. We also establish an upper and lower limit for the estimate error and provide the distance between planes that optimizes the estimate of the derivative.

  11. Femtosecond spectral phase shaping for CARS spectroscopy and imaging

    NASA Astrophysics Data System (ADS)

    Postma, Sytse; van Rhijn, Alexander C. W.; Korterik, Jeroen P.; Herek, Jennifer L.; Offerhaus, Herman L.

    Coherent Anti-Stokes Raman Scattering (CARS) is a third-order non-linear optical process that provides label-free, chemically selective microscopy by probing the internal vibrational structure of molecules. Due to the resonant enhancement of the CARS process, faster imaging is possible compared to Raman microscopy. CARS is unaffected by background fluorescence, but the inherent non-resonant background signal can overwhelm the resonant signal. We demonstrate how simple phase shapes on the pump (and probe) beam reduce the background signal and enhance the resonant signal. We demonstrate chemically selective microscopy using these shaped pulses on plastic beads.

  12. Development of a synthetic phase contrast imaging diagnostic

    NASA Astrophysics Data System (ADS)

    Rost, J. C.; Lin, L.; Porkolab, M.

    2010-06-01

    A "synthetic diagnostic" has been developed to calculate the expected experimental response of phase contrast imaging (PCI), a scattering diagnostic used to measure density fluctuations in laboratory plasmas, to a tokamak discharge modeled with the GYRO nonlinear gyrokinetic code [J. Candy and R. Waltz, J. Comput. Phys. 186, 545 (2003)]. The synthetic PCI includes the spatial response of the experimental diagnostic, primarily implemented as a line integral of plasma density along the beam path, and the minimum and maximum wavenumber response resulting from the detection scheme. The synthetic PCI can be used for comparisons between GYRO and experiment as well as studies of the PCI response.

  13. Development of a synthetic phase contrast imaging diagnostic

    SciTech Connect

    Rost, J. C.; Lin, L.; Porkolab, M. [Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States)

    2010-06-15

    A ''synthetic diagnostic'' has been developed to calculate the expected experimental response of phase contrast imaging (PCI), a scattering diagnostic used to measure density fluctuations in laboratory plasmas, to a tokamak discharge modeled with the GYRO nonlinear gyrokinetic code [J. Candy and R. Waltz, J. Comput. Phys. 186, 545 (2003)]. The synthetic PCI includes the spatial response of the experimental diagnostic, primarily implemented as a line integral of plasma density along the beam path, and the minimum and maximum wavenumber response resulting from the detection scheme. The synthetic PCI can be used for comparisons between GYRO and experiment as well as studies of the PCI response.

  14. X-ray phase imaging: from synchrotron to hospital

    PubMed Central

    Momose, Atsushi; Yashiro, Wataru; Kido, Kazuhiro; Kiyohara, Junko; Makifuchi, Chiho; Ito, Tsukasa; Nagatsuka, Sumiya; Honda, Chika; Noda, Daiji; Hattori, Tadashi; Endo, Tokiko; Nagashima, Masabumi; Tanaka, Junji

    2014-01-01

    With the aim of clinical applications of X-ray phase imaging based on Talbot–Lau-type grating interferometry to joint diseases and breast cancer, machines employing a conventional X-ray generator have been developed and installed in hospitals. The machine operation especially for diagnosing rheumatoid arthritis is described, which relies on the fact that cartilage in finger joints can be depicted with a dose of several milligray. The palm of a volunteer observed with 19?s exposure (total scan time: 32?s) is reported with a depicted cartilage feature in joints. This machine is now dedicated for clinical research with patients. PMID:24470409

  15. Spatiotemporal Characterization of a Fibrin Clot Using Quantitative Phase Imaging

    PubMed Central

    Gannavarpu, Rajshekhar; Bhaduri, Basanta; Tangella, Krishnarao; Popescu, Gabriel

    2014-01-01

    Studying the dynamics of fibrin clot formation and its morphology is an important problem in biology and has significant impact for several scientific and clinical applications. We present a label-free technique based on quantitative phase imaging to address this problem. Using quantitative phase information, we characterized fibrin polymerization in real-time and present a mathematical model describing the transition from liquid to gel state. By exploiting the inherent optical sectioning capability of our instrument, we measured the three-dimensional structure of the fibrin clot. From this data, we evaluated the fractal nature of the fibrin network and extracted the fractal dimension. Our non-invasive and speckle-free approach analyzes the clotting process without the need for external contrast agents. PMID:25386701

  16. Rytov approximation for x-ray phase imaging.

    PubMed

    Sung, Yongjin; Barbastathis, George

    2013-02-11

    In this study, we check the accuracy of the first-order Rytov approximation with a homogeneous sphere as a candidate for application in x-ray phase imaging of large objects e.g., luggage at the airport, or a human patient. Specifically, we propose a validity condition for the Rytov approximation in terms of a parameter V that depends on the complex refractive index of the sphere and the Fresnel number, for Fresnel numbers larger than 1000. In comparison with the exact Mie solution, we provide the accuracy of the Rytov approximation in predicting the intensity and phase profiles after the sphere. For large objects, where the Mie solution becomes numerically impractical, we use the principle of similarity to predict the accuracy of the Rytov approximation without explicit calculation of the Mie solution. Finally, we provide the maximum radius of the sphere for which the first order Rytov approximation remains valid within 1% accuracy. PMID:23481723

  17. Computational methods for microfluidic microscopy and phase-space imaging

    NASA Astrophysics Data System (ADS)

    Pegard, Nicolas Christian Richard

    Modern optical devices are made by assembling separate components such as lenses, objectives, and cameras. Traditionally, each part is optimized separately, even though the trade-offs typically limit the performance of the system overall. This component-based approach is particularly unfit to solve the new challenges brought by modern biology: 3D imaging, in vivo environments, and high sample throughput. In the first part of this thesis, we introduce a general method to design integrated optical systems. The laws of wave propagation, the performance of available technology, as well as other design parameters are combined as constraints into a single optimization problem. The solution provides qualitative design rules to improve optical systems as well as quantitative task-specific methods to minimize loss of information. Our results have applications in optical data storage, holography, and microscopy. The second part of this dissertation presents a direct application. We propose a more efficient design for wide-field microscopy with coherent light, based on double transmission through the sample. Historically, speckle noise and aberrations caused by undesired interferences have made coherent illumination unpopular for imaging. We were able to dramatically reduce speckle noise and unwanted interferences using optimized holographic wavefront reconstruction. The resulting microscope not only yields clear coherent images with low aberration---even in thick samples---but also increases contrast and enables optical filtering and in-depth sectioning. In the third part, we develop new imaging techniques that better respond to the needs of modern biology research through implementing optical design optimization. Using a 4D phase-space distribution, we first represent the state and propagation of incoherent light. We then introduce an additional degree of freedom by putting samples in motion in a microfluidic channel, increasing image diversity. From there, we develop a design that is minimally invasive yet optimizes the transfer of information from sample to detector. This optimization best responds to the desired imaging application. We present three microfluidic devices which can all be implemented as a compact add-on device for commercial microscopes. The first is a flow-scanning structured illumination microfluidic microscopy device demonstrating enhanced resolution in 2D. The second is a method for 3D deconvolution microscopy with a tilted channel to acquire and deconvolve gradually defocused images. Finally, we demonstrate optical projection microscopic tomography with simultaneous phase and intensity imaging capabilities in 3D by combining flow-scanning and optical acquisition in phase space. Experimental results utilize yeast cells as well as live C.elegans.. In the fourth part, we show that optical system optimization also has non-imaging applications such as solar cell engineering. Instead of looking for an optical setup that maximizes the transfer of information, we implement inexpensive surface wrinkles and folds in the layered structure of organic solar cells and optimize their surface density. This strategy enhances light trapping and further improves the electric conversion of solar energy.

  18. Fourier Lucas-Kanade algorithm.

    PubMed

    Lucey, Simon; Navarathna, Rajitha; Ashraf, Ahmed Bilal; Sridharan, Sridha

    2013-06-01

    In this paper, we propose a framework for both gradient descent image and object alignment in the Fourier domain. Our method centers upon the classical Lucas & Kanade (LK) algorithm where we represent the source and template/model in the complex 2D Fourier domain rather than in the spatial 2D domain. We refer to our approach as the Fourier LK (FLK) algorithm. The FLK formulation is advantageous when one preprocesses the source image and template/model with a bank of filters (e.g., oriented edges, Gabor, etc.) as 1) it can handle substantial illumination variations, 2) the inefficient preprocessing filter bank step can be subsumed within the FLK algorithm as a sparse diagonal weighting matrix, 3) unlike traditional LK, the computational cost is invariant to the number of filters and as a result is far more efficient, and 4) this approach can be extended to the Inverse Compositional (IC) form of the LK algorithm where nearly all steps (including Fourier transform and filter bank preprocessing) can be precomputed, leading to an extremely efficient and robust approach to gradient descent image matching. Further, these computational savings translate to nonrigid object alignment tasks that are considered extensions of the LK algorithm, such as those found in Active Appearance Models (AAMs). PMID:23599053

  19. 3D Cardiac microvessels embolization imaging based on X-ray phase contrast imaging

    PubMed Central

    2014-01-01

    Background The treatment of microcirculatory impairment will have great impact if it can be applied to myocardial infarction (MI) patients. The problem is how to study these tiny structures and microphenomenon in heart. Methods We investigated the visualization of cardiac microvessels embolization by the mean of X-ray phase contrast imaging (XPCI), which is a recently emerged imaging technique. Using the information of X-ray phase shift, it is sensitive to weak absorbing materials. Two MI SD rats were used as the microvessel embolization samples. MI was surgically induced by ligating left anterior descending artery. Imaging was performed 24 hours post-infarct, with barium sulfate as contrast agent. Results The coronary arteries were visualized with smooth walls and clear edges. The ligated vessels, with the diameter of about three hundred microns, can be clearly distinguished and there were no distal blood flow downstream from these branches. The results indicate that phase contrast imaging can directly demonstrate the distribution of microvessels, and estimate the area of MI. The infarct location was in good agreement with pathological analyses of the models. Conclusions The advantage of our method is directly observing and evaluating microvessel embolization which simplifies the procedure of diagnoses. Moreover, it is helpful for predicting the prognosis in MI and judging if angiogenesis happens. PMID:24886327

  20. Efficient phase contrast imaging in STEM using a pixelated detector. Part 1: Experimental demonstration at atomic resolution.

    PubMed

    Pennycook, Timothy J; Lupini, Andrew R; Yang, Hao; Murfitt, Matthew F; Jones, Lewys; Nellist, Peter D

    2015-04-01

    We demonstrate a method to achieve high efficiency phase contrast imaging in aberration corrected scanning transmission electron microscopy (STEM) with a pixelated detector. The pixelated detector is used to record the Ronchigram as a function of probe position which is then analyzed with ptychography. Ptychography has previously been used to provide super-resolution beyond the diffraction limit of the optics, alongside numerically correcting for spherical aberration. Here we rely on a hardware aberration corrector to eliminate aberrations, but use the pixelated detector data set to utilize the largest possible volume of Fourier space to create high efficiency phase contrast images. The use of ptychography to diagnose the effects of chromatic aberration is also demonstrated. Finally, the four dimensional dataset is used to compare different bright field detector configurations from the same scan for a sample of bilayer graphene. Our method of high efficiency ptychography produces the clearest images, while annular bright field produces almost no contrast for an in-focus aberration-corrected probe. PMID:25458189

  1. Quantification of dispersed phase concentration using light sheet imaging methods

    NASA Astrophysics Data System (ADS)

    Knowles, Philip L.; Kiger, Ken T.

    2012-03-01

    With the prevalence of particle image velocimetry (PIV) as a quantitative tool for fluid mechanics diagnostics, its application for analyzing complicated multiphase flows has been steadily increasing over the last several decades. While the primary issue in using PIV for multiphase flows is in separating the information of the phases for independent analysis with a minimum of spurious "cross-talk," an equally crucial but often overlooked point is in the accurate quantitative measurement of the dispersed phase concentration. Accurate concentration measurement is important due to the fact that the dispersed phase is often heterogeneously distributed in both space and time, either due to a non-uniformity of the source of particulates (such as a spray nozzle or sediment boundary) or due to inertial migration of the particles even from originally homogeneous spatial distributions. In the current work, we examine the effects of light sheet profile distortion and attenuation by tracer seeding particles, as well as reflected light from local wall boundaries on the effective light sheet thickness. The effective thickness is critical for concentration measurements, as it dictates the dispersed phase detection volume. A direct calibration method is demonstrated to measure the effective light sheet thickness in a water/glass bead system, which shows that systematic bias errors on the order of 30% can result if the reflective bed condition is not accounted for, and the errors can be as high as 50% or more if a single-point measure of the sheet width is used.

  2. Quantization noise and its reduction in lensless Fourier digital holography.

    PubMed

    Pandey, Nitesh; Hennelly, Bryan

    2011-03-01

    Digital holography is an imaging technique that enables recovery of topographic 3D information about an object under investigation. In digital holography, an interference pattern is recorded on a digital camera. Therefore, quantization of the recorded hologram is an integral part of the imaging process. We study the influence of quantization error in the recorded holograms on the fidelity of both the intensity and phase of the reconstructed image. We limit our analysis to the case of lensless Fourier off-axis digital holograms. We derive a theoretical model to predict the effect of quantization noise and we validate this model using experimental results. Based on this, we also show how the resultant noise in the reconstructed image, as well as the speckle that is inherent in digital holography, can be conveniently suppressed by standard speckle reduction techniques. We show that high-quality images can be obtained from binary holograms when speckle reduction is performed. PMID:21364713

  3. Derivatization technique to increase the spectral selectivity of two-dimensional Fourier transform infrared focal plane array imaging: analysis of binder composition in aged oil and tempera paint.

    PubMed

    Zumbühl, Stefan; Scherrer, Nadim C; Eggenberger, Urs

    2014-01-01

    The interpretation of standard Fourier transform infrared spectra (FT-IR) on oil-based paint samples often suffers from interfering bands of the different compounds, namely, binder, oxidative aging products, carboxylates formed during aging, and several pigments and fillers. The distinction of the aging products such as ketone and carboxylic acid functional groups pose the next problem, as these interfere with the triglyceride esters of the oil. A sample preparation and derivatization technique using gaseous sulfur tetrafluoride (SF4), was thus developed with the aim to discriminate overlapping signals and achieve a signal enhancement on superposed compounds. Of particular interest in this context is the signal elimination of the broad carboxylate bands of the typical reaction products developing during the aging processes in oil-based paints, as well as signal interference originating from several typical pigments in this spectral range. Furthermore, it is possible to distinguish the different carbonyl-containing functional groups upon selective alteration. The derivatization treatment can be applied to both microsamples and polished cross sections. It increases the selectivity of the infrared spectroscopy technique in a fundamental manner and permits the identification and two-dimensional (2D) localization of binder components in aged paint samples at the micrometer scale. The combination of SF4 derivatization with high-resolution 2D FT-IR focal plane array (FPA) imaging delivers considerable advances to the study of micro-morphological processes involving organic compounds. PMID:24694702

  4. Understanding the Phase Contrast Optics to Restore Artifact-free Microscopy Images for Segmentation

    PubMed Central

    Yin, Zhaozheng; Kanade, Takeo; Chen, Mei

    2012-01-01

    Phase contrast, a noninvasive microscopy imaging technique, is widely used to capture time-lapse images to monitor the behavior of transparent cells without staining or altering them. Due to the optical principle, phase contrast microscopy images contain artifacts such as the halo and shade-off that hinder image segmentation, a critical step in automated microscopy image analysis. Rather than treating phase contrast microscopy images as general natural images and applying generic image processing techniques on them, we propose to study the optical properties of the phase contrast microscope to model its image formation process. The phase contrast imaging system can be approximated by a linear imaging model. Based on this model and input image properties, we formulate a regularized quadratic cost function to restore artifact-free phase contrast images that directly correspond to the specimen's optical path length. With artifacts removed, high quality segmentation can be achieved by simply thresholding the restored images. The imaging model and restoration method are quantitatively evaluated on microscopy image sequences with thousands of cells captured over several days. We also demonstrate that accurate restoration lays the foundation for high performance in cell detection and tracking. PMID:22386070

  5. Understanding the phase contrast optics to restore artifact-free microscopy images for segmentation.

    PubMed

    Yin, Zhaozheng; Kanade, Takeo; Chen, Mei

    2012-07-01

    Phase contrast, a noninvasive microscopy imaging technique, is widely used to capture time-lapse images to monitor the behavior of transparent cells without staining or altering them. Due to the optical principle, phase contrast microscopy images contain artifacts such as the halo and shade-off that hinder image segmentation, a critical step in automated microscopy image analysis. Rather than treating phase contrast microscopy images as general natural images and applying generic image processing techniques on them, we propose to study the optical properties of the phase contrast microscope to model its image formation process. The phase contrast imaging system can be approximated by a linear imaging model. Based on this model and input image properties, we formulate a regularized quadratic cost function to restore artifact-free phase contrast images that directly correspond to the specimen's optical path length. With artifacts removed, high quality segmentation can be achieved by simply thresholding the restored images. The imaging model and restoration method are quantitatively evaluated on microscopy image sequences with thousands of cells captured over several days. We also demonstrate that accurate restoration lays the foundation for high performance in cell detection and tracking. PMID:22386070

  6. Generic ring fourier descriptors for shape description

    Microsoft Academic Search

    Jian-Wei Yang; Xiang-Jun Zhao; Ru-Shi Lan

    2010-01-01

    The traditional Fourier descriptor (FD) can only be used to objects with single boundary. We develop a novel method, Generic Ring Fourier Descriptor (GRFD), which can be applicable to gray-scale image. Firstly, we take an unconventional view of the traditional FDs, as we treat the boundary as a closed-curve in a 2-D binary image. Consequently, the generated FD (GFD) is

  7. Level 2 processing for the imaging Fourier transform spectrometer GLORIA: derivation and validation of temperature and trace gas volume mixing ratios from calibrated dynamics mode spectra

    NASA Astrophysics Data System (ADS)

    Ungermann, J.; Blank, J.; Dick, M.; Ebersoldt, A.; Friedl-Vallon, F.; Giez, A.; Guggenmoser, T.; Höpfner, M.; Jurkat, T.; Kaufmann, M.; Kaufmann, S.; Kleinert, A.; Krämer, M.; Latzko, T.; Oelhaf, H.; Olchewski, F.; Preusse, P.; Rolf, C.; Schillings, J.; Suminska-Ebersoldt, O.; Tan, V.; Thomas, N.; Voigt, C.; Zahn, A.; Zöger, M.; Riese, M.

    2014-12-01

    The Gimballed Limb Observer for Radiance Imaging of the Atmosphere (GLORIA) is an airborne infrared limb-imager combining a two-dimensional infrared detector with a Fourier transform spectrometer. It was operated aboard the new German Gulfstream G550 research aircraft HALO during the Transport And Composition in the upper Troposphere/lowermost Stratosphere (TACTS) and Earth System Model Validation (ESMVAL) campaigns in summer 2012. This paper describes the retrieval of temperature and trace gas (H2O, O3, HNO3) volume mixing ratios from GLORIA dynamics mode spectra. 26 integrated spectral windows are employed in a joint fit to retrieve seven targets using consecutively a fast and an accurate tabulated radiative transfer model. Typical diagnostic quantities are provided including effects of uncertainties in the calibration and horizontal resolution along the line-of-sight. Simultaneous in-situ observations by the BAsic HALO Measurement And Sensor System (BAHAMAS), the Fast In-Situ Stratospheric Hygrometer (FISH), FAIRO, and the Atmospheric chemical Ionization Mass Spectrometer (AIMS) allow a validation of retrieved values for three flights in the upper troposphere/lowermost stratosphere region spanning polar and sub-tropical latitudes. A high correlation is achieved between the remote sensing and the in-situ trace gas data, and discrepancies can to a large fraction be attributed to differences in the probed air masses caused by different sampling characteristics of the instruments. This 1-D processing of GLORIA dynamics mode spectra provides the basis for future tomographic inversions from circular and linear flight paths to better understand selected dynamical processes of the upper troposphere and lowermost stratosphere.

  8. Detection and imaging of the moving target using frequency space-time adaptive processing and fractional Fourier transform

    NASA Astrophysics Data System (ADS)

    Wu, Jian; Jiang, Yongmei; Kuang, Gangyao

    2014-10-01

    As for multi-channel SAR, the spectrum of the clutter is spatially-temporally coupled, and the echo of the moving target is chirp signal. A novel method based on STAP and FrFT is proposed in this paper, which is used for moving target detection and parameter estimation. Two steps are used for fast target detection : the coarse detection in low range resolution and parameter estimation for the specific data where the moving target appears. This paper discusses the principle of frequency STAP for clutter suppression firstly, and subsequently infers that the signal after clutter suppression is chirp signal. Then FrFT is introduced to estimate the parameters of the output signal, which can be used to estimate the parameters of the moving target. Finally, the process of the proposed method is introduced. Matching function is constructed to compensate the phase deviation caused by movement and focus the moving target. The effectiveness of the proposed method is validated by the simulation.

  9. Evaluation of edge effect due to phase contrast imaging for mammography

    SciTech Connect

    Matsuo, Satoru; Katafuchi, Tetsuro; Tohyama, Keiko; Morishita, Junji; Yamada, Katsuhiko; Fujita, Hiroshi [Department of Radiology, Shiga University of Medical Science, Shiga (Japan); Department of Radiology, National Cardiovascular Center, Suita, Osaka (Japan); Kyoto College of Medical Technology, Kyoto, (Japan); Department of Health Sciences, School of Medicine, Kyushu University (Japan); Kyoto College of Medical Technology, Kyoto (Japan); Department of Intelligent Image Information, Graduate School of Medicine, Gifu University (Japan)

    2005-08-15

    It is well-known that the edge effect produced by phase contrast imaging results in the edge enhancement of x-ray images and thereby sharpens those images. It has recently been reported that phase contrast imaging using practical x-ray tubes with small focal spots has improved image sharpness as observed in the phase contrast imaging with x-ray from synchrotron radiation or micro-focus x-ray tubes. In this study, we conducted the phase contrast imaging of a plastic fiber and plant seeds using a customized mammography equipment with a 0.1 mm focal spot, and the improvement of image sharpness was evaluated in terms of spatial frequency response of the images. We observed that the image contrast of the plastic fiber was increased by edge enhancement, and, as predicted elsewhere, spectral analysis revealed that as the spatial frequencies of the x-ray images increased, so did the sharpness gained through phase contrast imaging. Thus, phase contrast imaging using a practical molybdenum anode tube with a 0.1 mm-focal spot would benefit mammography, in which the morphological detectability of small species such as micro-calcifications is of great concern. And detectability of tumor-surrounded glandular tissues in dense breast would be also improved by the phase contrast imaging.

  10. Matrix phased array (MPA) imaging technology for resistance spot welds

    SciTech Connect

    Na, Jeong K.; Gleeson, Sean T. [Edison Welding Institute, 1250 Arthur E. Adams Drive, Columbus, OH 43221 (United States)

    2014-02-18

    A three-dimensional MPA probe has been incorporated with a high speed phased array electronic board to visualize nugget images of resistance spot welds. The primary application area of this battery operated portable MPA ultrasonic imaging system is in the automotive industry which a conventional destructive testing process is commonly adopted to check the quality of resistance spot welds in auto bodies. Considering an average of five-thousand spot welds in a medium size passenger vehicle, the amount of time and effort given to popping the welds and measuring nugget size are immeasurable in addition to the millions of dollars' worth of scrap metals recycled per plant per year. This wasteful labor intensive destructive testing process has become less reliable as auto body sheet metal has transitioned from thick and heavy mild steels to thin and light high strength steels. Consequently, the necessity of developing a non-destructive inspection methodology has become inevitable. In this paper, the fundamental aspects of the current 3-D probe design, data acquisition algorithms, and weld nugget imaging process are discussed.

  11. Matrix phased array (MPA) imaging technology for resistance spot welds

    NASA Astrophysics Data System (ADS)

    Na, Jeong K.; Gleeson, Sean T.

    2014-02-01

    A three-dimensional MPA probe has been incorporated with a high speed phased array electronic board to visualize nugget images of resistance spot welds. The primary application area of this battery operated portable MPA ultrasonic imaging system is in the automotive industry which a conventional destructive testing process is commonly adopted to check the quality of resistance spot welds in auto bodies. Considering an average of five-thousand spot welds in a medium size passenger vehicle, the amount of time and effort given to popping the welds and measuring nugget size are immeasurable in addition to the millions of dollars' worth of scrap metals recycled per plant per year. This wasteful labor intensive destructive testing process has become less reliable as auto body sheet metal has transitioned from thick and heavy mild steels to thin and light high strength steels. Consequently, the necessity of developing a non-destructive inspection methodology has become inevitable. In this paper, the fundamental aspects of the current 3-D probe design, data acquisition algorithms, and weld nugget imaging process are discussed.

  12. Real Time Blood Testing Using Quantitative Phase Imaging

    PubMed Central

    Pham, Hoa V.; Bhaduri, Basanta; Tangella, Krishnarao; Best-Popescu, Catherine; Popescu, Gabriel

    2013-01-01

    We demonstrate a real-time blood testing system that can provide remote diagnosis with minimal human intervention in economically challenged areas. Our instrument combines novel advances in label-free optical imaging with parallel computing. Specifically, we use quantitative phase imaging for extracting red blood cell morphology with nanoscale sensitivity and NVIDIA’s CUDA programming language to perform real time cellular-level analysis. While the blood smear is translated through focus, our system is able to segment and analyze all the cells in the one megapixel field of view, at a rate of 40 frames/s. The variety of diagnostic parameters measured from each cell (e.g., surface area, sphericity, and minimum cylindrical diameter) are currently not available with current state of the art clinical instruments. In addition, we show that our instrument correctly recovers the red blood cell volume distribution, as evidenced by the excellent agreement with the cell counter results obtained on normal patients and those with microcytic and macrocytic anemia. The final data outputted by our instrument represent arrays of numbers associated with these morphological parameters and not images. Thus, the memory necessary to store these data is of the order of kilobytes, which allows for their remote transmission via, for example, the cellular network. We envision that such a system will dramatically increase access for blood testing and furthermore, may pave the way to digital hematology. PMID:23405194

  13. Role of phase key in the double random phase encoding technique: an error analysis.

    PubMed

    Monaghan, David S; Situ, Guohai; Gopinathan, Unnikrishnan; Naughton, Thomas J; Sheridan, John T

    2008-07-20

    We perform a numerical analysis of the double random phase encryption-decryption technique to determine how, in the case of both amplitude and phase encoding, the two decryption keys (the image- and Fourier-plane keys) affect the output gray-scale image when they are in error. We perform perfect encryption and imperfect decryption. We introduce errors into the decrypting keys that correspond to the use of random distributions of incorrect pixel values. We quantify the effects that increasing amounts of error in the image-plane key, the Fourier-plane key, and both keys simultaneously have on the decrypted image. Quantization effects are also examined. PMID:18641750

  14. Inpainting algorithm for jacquared image based on phase-field model

    Microsoft Academic Search

    Zhilin Feng; Jianwei Yin; Jianan Zhou

    2008-01-01

    Jacquard image inpainting is an interesting new research topic in pattern preprocessing for jacquard CAD. Phase field model has been well acknowledged as an important method for image inpainting. This paper discussed the problem of jacquard image inpainting by approaching the phase field paradigm from a numerical approximation perspective. The basic idea is to represent the damaged pattern of interest

  15. Ultrasound phase contrast thermal imaging with reflex transmission imaging methods in tissue phantoms

    PubMed Central

    Farny, Caleb H.; Clement, Gregory T.

    2009-01-01

    Thermal imaging measurements using ultrasound phase contrast have been performed in tissue phantoms heated with a focused ultrasound source. Back projection and reflex transmission imaging principles were employed to detect sound speed-induced changes in the phase caused by an increase in the temperature. The temperature was determined from an empirical relationship for the temperature dependence on sound speed. The phase contrast was determined from changes in the sound field measured with a hydrophone scan conducted before and during applied heating. The lengthy scanning routine used to mimic a large two-dimensional array required a steady-state temperature distribution within the phantom. The temperature distribution in the phantom was validated with magnetic resonance (MR) thermal imaging measurements. The peak temperature was found to agree within 1°C with MR and good agreement was found between the temperature profiles. The spatial resolution was 0.3 × 0.3 × 0.3 mm, comparing favorably with the 0.625 × 0.625 × 1.5 mm MR spatial resolution. PMID:19683380

  16. Geophysical data fusion for subsurface imaging. Phase 1

    SciTech Connect

    Hoekstra, P.; Vandergraft, J.; Blohm, M.; Porter, D.

    1993-08-01

    A geophysical data fusion methodology is under development to combine data from complementary geophysical sensors and incorporate geophysical understanding to obtain three dimensional images of the subsurface. The research reported here is the first phase of a three phase project. The project focuses on the characterization of thin clay lenses (aquitards) in a highly stratified sand and clay coastal geology to depths of up to 300 feet. The sensor suite used in this work includes time-domain electromagnetic induction (TDEM) and near surface seismic techniques. During this first phase of the project, enhancements to the acquisition and processing of TDEM data were studied, by use of simulated data, to assess improvements for the detection of thin clay layers. Secondly, studies were made of the use of compressional wave and shear wave seismic reflection data by using state-of-the-art high frequency vibrator technology. Finally, a newly developed processing technique, called ``data fusion,`` was implemented to process the geophysical data, and to incorporate a mathematical model of the subsurface strata. Examples are given of the results when applied to real seismic data collected at Hanford, WA, and for simulated data based on the geology of the Savannah River Site.

  17. Fingerprint classification using fast Fourier transform and nonlinear discriminant analysis

    Microsoft Academic Search

    Cheong Hee Park; Haesun Park

    2005-01-01

    In this paper, we present a new approach for fingerprint class ification based on Discrete Fourier Transform (DFT) and nonlinear discriminant analysis. Utilizing the Discrete Fourier Transform and directional filters, a relia ble and efficient directional image is constructed from each fingerprint image, and then no nlinear discriminant analysis is applied to the constructed directional images, reducing the dimension dra-

  18. USING PHASE AND MAGNITUDE INFORMATION OF THE COMPLEX DIRECTIONAL FILTER BANK FOR TEXTURE IMAGE RETRIEVAL

    E-print Network

    Oraintara, Soontorn

    USING PHASE AND MAGNITUDE INFORMATION OF THE COMPLEX DIRECTIONAL FILTER BANK FOR TEXTURE IMAGE, Fontainebleau, 77305 France ABSTRACT This paper discusses how to utilize both magnitude and phase in- formation images. This paper discusses how magnitude and phase information of the complex directional lter bank

  19. Cortical Enhanced Tissue Segmentation of Neonatal Brain MR Images Acquired by a Dedicated Phased Array Coil

    E-print Network

    Utah, University of

    this problem, a dedicated phased array neonatal head coil is utilized to improve MR image quality;a dedicated neonatal phased array coil is devised to improve the SNR as well as spatial resolutionCortical Enhanced Tissue Segmentation of Neonatal Brain MR Images Acquired by a Dedicated Phased

  20. Signal-to-NoiseMeasurements in Magnitude Images from NMR Phased Arrays

    E-print Network

    Atalar, Ergin

    Signal-to-NoiseMeasurements in Magnitude Images from NMR Phased Arrays Chris D. Constantinides% with respectto the true SNR valuesas a result of noise correlations between receivers. Key words: phased array of NMR signals in phased array systems, a number of image reconstruction algorithms have been developed

  1. (SAITO Takeshi) Fourier Galois

    E-print Network

    Bannai, Kenichi

    (SAITO Takeshi) A. Galois Fourier Laumon Abbes Fourier Galois Fourier Laumon Laumon Hilbert p. B. 1. K. Kato and T. Saito "Ramification theory for varieties over a perfect field", Annals of Math. 168 (2008), 33-96. 2. A. Abbes and T. Saito "Analyse micro- locale -adique en caract´eristique p > 0

  2. Hierarchical security system using real-valued data and orthogonal code in Fourier domain

    NASA Astrophysics Data System (ADS)

    Kim, Hyun-Jun; Seo, Dong-Hoan; Hwang, Kwang-Il; Lim, Tae-Woo

    2014-02-01

    We propose a novel hierarchical encryption scheme using orthogonal code in Fourier domain and decryption based on interferometer system. The proposed system is composed of hierarchical ciphertexts with positive real values which can be applied for practical transmission such as Internet, and decryption keys with real valued function which has orthogonal characteristic in the decryption system. Since the original information is encrypted on the Fourier plane, the proposed encryption is more tolerant to loss of key information by scratching or cutting than encryption in a spatial domain. The resulting image using Fourier transform and an interferometer system with constant phase retarder is then decrypted by use of a ciphertext with different security level and each of decryption keys made from the multiplication of orthogonal code and random phase code in order to enhance the level of security. We demonstrate the efficiency of the proposed method and the fault-tolerance properties of data loss through several simulations.

  3. A new method of phase derivative extracting for off-axis quantitative phase imaging

    NASA Astrophysics Data System (ADS)

    Xu, Yuanyuan; Wang, Yawei; Jin, Weifeng; Lv, Cuihong; Wu, Hui

    2013-09-01

    We present a new derivative method for phase information extraction in off-axis quantitative phase imaging (QPI). Similar to other rapid derivative method, this method only uses the interference term, the 1st and 2nd order derivatives of a single interferogram in QPI, but the assumption in our method is different from that of other derivative method. And this method can be used to optimize small spatial frequency processing capability in slightly off-axis QPI. We illustrate the proposed method with theory and simulation experiment of a ball, and prove our method by comparing our simulation results with the experimental results of the red blood cell and the skin cancer cell, respectively.

  4. Tunable elastomer-based virtually imaged phased array.

    PubMed

    Metz, Philipp; Block, Hendrik; Behnke, Christopher; Krantz, Matthias; Gerken, Martina; Adam, Jost

    2013-02-11

    Virtually imaged phased arrays (VIPAs) offer a high potential for wafer-level integration and superior optical properties compared to conventional gratings. We introduce an elastomer-based tunable VIPA enabling fine tuning of the dispersion characteristics. It consists of a poly-dimethylsiloxane (PDMS) layer sandwiched between silver bottom and top coatings, which form the VIPA's high reflective and semi-transparent mirror, respectively. The latter also acts as an electrode for Joule heating, such that the optical PDMS resonator cavity tuning is carried out via a combination of thermal expansion and the thermo-optic effect. Analogous to the free spectral range (FSR), based on a VIPA specific dispersion law, we introduce a new characteristic VIPA performance measure, namely the free angular range (FAR). We report a tuning span of one FAR achieved by a 7.2K temperature increase of a 170?m PDMS VIPA. Both resonance quality and tunability are analyzed in numerical simulations and experiments. PMID:23481792

  5. Quasi-Born Fourier migration

    NASA Astrophysics Data System (ADS)

    Huang, Lian-Jie; Fehler, C. Michael

    2000-03-01

    The Born approximation of the Lippman-Schwinger equation has recently been used to implement a recursive method for seismic migration of pressure wavefields. This Born-based method is stable only when the scattering from heterogeneities within an extrapolation depth interval is weak. To handle strong scattering accurately and efficiently, we propose a quasi-Born approximation of the Lippman-Schwinger equation to extrapolate pressure wavefields downwards recursively. We assume that the scattered wavefield is linearly related to the incident wavefield by a scalar function that varies slowly with lateral position within an extrapolation depth interval. The extrapolation is implemented as a dual-doma in procedure in the frequency-space and frequency-wavenumber domains. Fast Fourier transforms are used to transform data between these two domains. The quasi-Born-based depth-migration algorithm is termed the quasi-Born Fourier method. It can efficiently produce good-quality images of complex structures with strong lateral perturbations of slowness. It is stable for strong scattering and can accurately handle scattering and wave propagation along directions at large angles from the main propagation direction. Image quality obtained using the new method is similar to that of a dual-domain migration method that uses the Rytov approximation within each extrapolation depth interval, but the computational speed of the new method is approximately 27 per cent faster than the latter method for pre-stack migration of an industry standard data set-the Marmousi data set. Compared to the Born-based migration method, the quasi-Born Fourier method is slightly less efficient because it requires an additional multiplication and an additional division for each lateral gridpoint in each step of wavefield extrapolation. For weak scattering, the quasi-Born Fourier method converges to the Born-based method. To improve the efficiency of the quasi-Born Fourier method further without losing its accuracy, we propose a hybrid Born/quasi-Born Fourier method in which the Born-based method is used when the scattering within an extrapolation depth interval is weak, and the quasi-Born Fourier method is used for other cases. This hybrid method is approximately 32 per cent faster than the Rytov-based method for the pre-stack depth migration of the Marmousi data set, while the images obtained using both methods have almost the same quality.

  6. Accelerated Proton Echo Planar Spectroscopic Imaging (PEPSI) Using GRAPPA with a 32-Channel Phased-Array

    E-print Network

    Accelerated Proton Echo Planar Spectroscopic Imaging (PEPSI) Using GRAPPA with a 32-Channel PhasedD proton echo planar spec- troscopic imaging (PEPSI) at 3T using generalized autocalibrat- ing words: proton echo planar spectroscopic imaging; PEPSI; MR spectroscopic imaging; parallel MRI; 32

  7. Optical encryption for large-sized images using random phase-free method

    E-print Network

    Shimobaba, Tomoyoshi; Endo, Yutaka; Hirayama, Ryuji; Hiyama, Daisuke; Hasegawa, Satoki; Nagahama, Yuki; Sano, Marie; Sugie, Takashige; Ito, Tomoyoshi

    2015-01-01

    We propose an optical encryption framework that can encrypt and decrypt large-sized images beyond the size of the encrypted image using our two methods: random phase-free method and scaled diffraction. In order to record the entire image information on the encrypted image, the large-sized images require the random phase to widely diffuse the object light over the encrypted image; however, the random phase gives rise to the speckle noise on the decrypted images, and it may be difficult to recognize the decrypted images. In order to reduce the speckle noise, we apply our random phase-free method to the framework. In addition, we employ scaled diffraction that calculates light propagation between planes with different sizes by changing the sampling rates.

  8. Direct Imaging Searches with the Apodizing Phase Plate Coronagraph

    NASA Astrophysics Data System (ADS)

    Kenworthy, M.; Meshkat, T.; Otten, , G.; Codona, J.

    2014-03-01

    The sensitivity of direct imaging searches for extrasolar planets is limited by the presence of diffraction rings from the primary star. Coronagraphs are angular filters that minimise these diffraction structures whilst allowing light from faint companions to shine through. The Apodizing Phase Plate (APP; Kenworthy 2007) coronagraph is a simple pupil plane optic that suppresses diffraction over a 180 degree region around each star simultaneously, providing easy beam switching observations and requiring no time consuming optical alignment at the telescope. We will present our results on using the APP at the Very Large Telescope in surveys for extrasolar planets around A/F and debris disk hosting stars in the L' band (3.8 microns) in the Southern Hemisphere, where we reach a contrast of 12 magnitudes at 0.5 arcseconds (Meshkat 2013). In Leiden, we are also developing the next generation of broadband achromatic coronagraphs that can simultaneously image both sides of the star using Vector APPs (Snik 2012, Otten 2012). Recent laboratory results showing the potential of this technology for future ELTs will also be presented.

  9. Quantitative phase imaging of human red blood cells using phase-shifting white light interference microscopy with colour fringe analysis

    NASA Astrophysics Data System (ADS)

    Singh Mehta, Dalip; Srivastava, Vishal

    2012-11-01

    We report quantitative phase imaging of human red blood cells (RBCs) using phase-shifting interference microscopy. Five phase-shifted white light interferograms are recorded using colour charge coupled device camera. White light interferograms were decomposed into red, green, and blue colour components. The phase-shifted interferograms of each colour were then processed by phase-shifting analysis and phase maps for red, green, and blue colours were reconstructed. Wavelength dependent refractive index profiles of RBCs were computed from the single set of white light interferogram. The present technique has great potential for non-invasive determination of refractive index variation and morphological features of cells and tissues.

  10. Digital image synthesis and multiple-image encryption based on parameter multiplexing and phase-shifting interferometry

    Microsoft Academic Search

    X. F. Meng; L. Z. Cai; Y. R. Wang; X. L. Yang; X. F. Xu; G. Y. Dong; X. X. Shen

    2009-01-01

    A novel digital image synthesis and multiple-image encryption technique based on parameter multiplexing and phase-shifting interferometry by discrete Fresnel transform is proposed. Both the image synthesis and the multiple-image encryption can be realized with the same system arrangement and similar principles, while the former is achieved by using different sets of parameters (wavelength and distance) and the same set of

  11. Interparticle Interactions and Direct Imaging of Colloidal Phases Assembled from Microsphere-Nanoparticle

    E-print Network

    Weeks, Eric R.

    Interparticle Interactions and Direct Imaging of Colloidal Phases Assembled from Microsphere the interparticle interactions, phase behavior, and structure of microsphere-nanoparticle mixtures that possess high microsphere interactions in suspension, yielding new insight into the origin of the experimentally observed

  12. Implementation of measure of relative tendency to phase image filtering spacial based

    NASA Astrophysics Data System (ADS)

    Syakrani, Nurjannah; Baskoro, Edy T.; Mengko, Tati L. R.; Suksmono, A. B.

    2014-03-01

    Complex image can split to magnitudo and phase images. The phase of complex function is uniquely defined only in the principal or wrapped value range (-?, ?]. Complex image is producted by special equipment as MRI, InSAR and Optics. Image acquisition has noise mostly. The noise come from modality, transmission media or object of image. Generally, the noise has two classification that are additive as Gaussian or multiplicative as speckle. The noise make image processing effectiveless. One of measure of relative tendency in Statistics is quartile consist of low, middle (median) and upper quartiles. Until now, basic spatial filtering method is constructed mean based that linear category or median based that simple nonlinear category. There is different formulation to get measure of central or relatif tendency between magnitudo and phase data. This paper propose a new filtering method base on quartile to phase image specially. Using 3×3 window to implementation of quartile algorithm in Matlab is tested to simulation phase image named Peak2XY by two kind of noises that are Gaussian and Speckle. For example, PSNR of upper quartile filtering to Peak2XY by Gaussian noise with mean =0, variance=0.01, are LoQu = +20.2622; MidQu = +23.7045; UpQu = +21.3528. The quartile filtering method also tested to head phase image of Magnetics Resonance Imaging and Fuji of InSAR phase image.

  13. Phase imaging by atomic force microscopy: analysis of living homoiothermic vertebrate cells.

    PubMed Central

    Nagao, E; Dvorak, J A

    1999-01-01

    Atomic force microscope-based phase imaging in air is capable of elucidating variations in material properties such as adhesion, friction, and viscoelasticity. However, the interpretation of phase images of specimens in a fluid environment requires clarification. In this report, we systematically analyzed atomic force microscope-derived phase images of mica, glass, and collagen under the same conditions as used for living cells at various tapping forces; the resulting data provide critical information for the interpretation of phase images of living cells. The peripheral regions of COS-1 cells consistently show a more negative phase shift than the glass substrate in phase images at set-point amplitude: free amplitude (Asp/A0) = 0.6-0.8. In addition, at all Asp/A0 values suitable for phase imaging, tapping frequency appears to be high enough to ensure that phase shifts are governed primarily by stiffness. Consequently, phase imaging is capable of high resolution studies of the cellular surface by detecting localized variations in stiffness. We demonstrate that phase imaging of a bifurcating fiber in COS-1 cell cytoplasm is readily capable of a lateral resolution of approximately 30 nm. PMID:10354454

  14. A hybrid heuristic algorithm to improve known-plaintext attack on Fourier plane encryption.

    PubMed

    Liu, Wensi; Yang, Guanglin; Xie, Haiyan

    2009-08-01

    A hybrid heuristic attack scheme that combines the hill climbing algorithm and the simulated annealing algorithm is proposed to speed up the search procedure and to obtain a more accurate solution to the original key in the Fourier plane encryption algorithm. And a unit cycle is adopted to analyze the value space of the random phase. The experimental result shows that our scheme can obtain more accurate solution to the key that can achieve better decryption result both for the selected encrypted image and another unseen ciphertext image. The searching time is significantly reduced while without any exceptional case in searching procedure. For an image of 64x64 pixels, our algorithm costs a comparatively short computing time, about 1 minute, can retrieve the approximated key with the normalized root mean squared error 0.1, therefore, our scheme makes the known-plaintext attack on the Fourier plane image encryption more practical, stable, and effective. PMID:19654800

  15. The History of the Fourier Tachometer

    NASA Astrophysics Data System (ADS)

    Beckers, J. M.; Brown, T. M.

    2013-12-01

    Following a suggestion by one of us (T. Brown) we developed in 1978 at the Sacramento Peak Observatory the first version of what we called a Fourier Tachometer which measured the phase of a single frequency component of the Fourier transform of the solar spectrum associated with a specific solar spectrum line (Beckers & Brown 1978). This phase is a direct measure of the wavelength of that Line, its Doppler shift and by using polarization optics, its Zeeman splitting. This first version based on a Michelson interferometer (FT I) was later (Evans 1081) greatly improved by J.W. Evans by using a Solid Polarizing Interferometer (version FT II). The latest version stands out by its ability to: (i) get wavelength measurements over a large 2D field-of-view without the cumbersome use of a high-resolution spectrograph, (ii) have a wide angular field-of-view and étendue, (iii) be mechanically stable and use much real-time digital processing. The FT II was selected for use in Global Oscillation Network Group (GONG) in about 1985 and has since then also been used in the space based helioseismometers — Micheson Doppler Imager (MDI) onboard Solar and Heliospheric Observatory (Scherrer et al. 1995) and Helioseismic Magnetic Imager (HMI) onboard Solar Dynamics Observatory (Scherrer et al. 2012). The FT II performance has increased over the years with the current HMI version having 4096 × 4096 pixels, or 0.5 × 0.5 arcsec for the HMI full disk facility, and a cadence of 45 seconds. However, except for some early observations at the Sacramento Peak, the Fourier Tachometer has not appeared to have been applied to non-helioseismology ground-based observations. In ground-based telescopes science full precise line profiles are generally desired making the FT II undesirable since it only measures something close to their center-of-gravity. For future very large diameter (1.5 - 8 m) ground-based solar telescopes that will also be the case. But complimentary FT II observations, for example from the spectrograph reflecting slit-jaws, would provide valuable, high time and spatial resolution complimentary observations. The HMI version would have pixel sizes of about 0.03 × 0.03 arcsec, closely matching the telescope resolution over a 2 × 2 arcmin field-of-view provided by its Multi-Conjugate Adaptive Optics system.

  16. Simultaneous transmission for an encrypted image and a double random-phase encryption key.

    PubMed

    Yuan, Sheng; Zhou, Xin; Li, Da-hai; Zhou, Ding-fu

    2007-06-20

    We propose a method to simultaneously transmit double random-phase encryption key and an encrypted image by making use of the fact that an acceptable decryption result can be obtained when only partial data of the encrypted image have been taken in the decryption process. First, the original image data are encoded as an encrypted image by a double random-phase encryption technique. Second, a double random-phase encryption key is encoded as an encoded key by the Rivest-Shamir-Adelman (RSA) public-key encryption algorithm. Then the amplitude of the encrypted image is modulated by the encoded key to form what we call an encoded image. Finally, the encoded image that carries both the encrypted image and the encoded key is delivered to the receiver. Based on such a method, the receiver can have an acceptable result and secure transmission can be guaranteed by the RSA cipher system. PMID:17538671

  17. Proton bound homodimers and heterodimers of amides and amines in the gas phase. Equilibrium studies by Fourier transform ion cyclotron resonance spectrometry

    Microsoft Academic Search

    Matthias Witt; Hans-Friedrich Grützmacher

    2002-01-01

    By injection of the proton bound homodimer [DMF·H+·DMF] of N,N-dimethylformamide (DMF) generated in an external ion source into a mixture of DMF and a second base within the\\u000a cell of a Fourier transform ion cyclotron resonance (FT-ICR) spectrometer the equilibria between [DMF·H+·DMF] and the other possible proton bound dimers [DMF·H+·base] and [base·H+·base] have been studied for 13 different bases. Strongly

  18. Phase-resolved optical Doppler tomography for imaging flow dynamics in microfluidic channels

    E-print Network

    Chen, Zhongping

    Phase-resolved optical Doppler tomography for imaging flow dynamics in microfluidic channels Lei and Computer Science, Department of Biomedical Engineering, Integrated Nanosystem Research Facility and Beckman June 2004) Phase-resolved optical Doppler tomography (ODT), an imaging technique based on low coherence

  19. Tissue imaging and serum lipidomic profiling for screening potential biomarkers of thyroid tumors by matrix-assisted laser desorption/ionization-Fourier transform ion cyclotron resonance mass spectrometry.

    PubMed

    Guo, Shuai; Qiu, Ling; Wang, Yanming; Qin, Xuzhen; Liu, Hui; He, Manwen; Zhang, Yaping; Li, Zhili; Chen, Xiaohong

    2014-07-01

    Changes in serum lipidome and in tissue lipidome are associated with cancer. In this study, tissue mass spectrometry imaging (MSI) and serum lipid profiling by matrix-assisted laser desorption/ionization-Fourier transform ion cyclotron resonance mass spectrometry (MALDI-FTICR MS) were performed to investigate significantly changed lipids in both tumor (malignant thyroid cancer (MTC) and benign thyroid tumor (BTT)) tissues and sera. Y-scatterplots of variable importance in the projection (VIP) values vs. fold change values indicate that change trends in the levels of ten lipids (i.e., phosphatidylcholine (PC)(34:1), PC(36:1), PC(38:6), phosphatidic acid (PA) (36:2), PA(36:3), PA(38:3), PA(38:4), PA(38:5), PA(40:5), and sphingomyelin (SM)(34:1)) in both tissues and sera from MTC patients, BTT patients, and normal individuals are significantly associated with these three types of pathophysiological status. In order to examine their diagnostic ability, 289 serum samples from 124 MTC patients, 43 BTT patients, and 122 normal controls were randomly divided into the training set and validation set. A biomarker of PC(34:1) exhibited excellent diagnostic ability to differentiate both MTC and BTT patients from normal individuals, with an area under the receiver operating characteristic (ROC) curve value of 0.984, a sensitivity of 96.4 %, and a specificity of 92.7 %. A panel which included PA(36:3) and SM(34:1) could distinguish between MTC and BTT, with an area under receiver operating characteristic curve (AUC) of 0.961, a sensitivity of 87.8 %, and a specificity of 92.9 %. It is worth noting that a panel consisting of PC(34:1), PA(36:3), and SM(34:1) could differentiate MTC patients from both BTT patients and normal individuals, with an AUC of 0.841, a sensitivity of 86.6 %, and a specificity of 75.5 %. PMID:24842401

  20. A STATISTICAL APPROACH TO IMAGE WARPING Chris Glasbey

    E-print Network

    Stone, J. V.

    ;Question 1: Can we superimpose microscope images? brightfield DIC phase contrast 2 #12;Question 2: Can we splines ( kriging) 10 #12;An example of thin plate splines: Venus Venus warped average Arad et al microscope images? The Fourier representation of Y is Yx = A cos + 2 T x x X. Y A (amplitude) (phase

  1. Double color image encryption using iterative phase retrieval algorithm in quaternion gyrator domain.

    PubMed

    Shao, Zhuhong; Shu, Huazhong; Wu, Jiasong; Dong, Zhifang; Coatrieux, Gouenou; Coatrieux, Jean Louis

    2014-03-10

    This paper describes a novel algorithm to encrypt double color images into a single undistinguishable image in quaternion gyrator domain. By using an iterative phase retrieval algorithm, the phase masks used for encryption are obtained. Subsequently, the encrypted image is generated via cascaded quaternion gyrator transforms with different rotation angles. The parameters in quaternion gyrator transforms and phases serve as encryption keys. By knowing these keys, the original color images can be fully restituted. Numerical simulations have demonstrated the validity of the proposed encryption system as well as its robustness against loss of data and additive Gaussian noise. PMID:24663832

  2. A new approach for extracting phase effect based on in-line X-ray phase imaging

    NASA Astrophysics Data System (ADS)

    Xia, Tian; Ma, Junshan; Zhang, Xuelong; Cheng, Jinghai; Peng, Weijun; Yao, Xufeng

    2014-05-01

    In clinical applications, the X-ray spectra from tungsten are continuous, and include both attenuation and phase effects for in-line X-ray imaging. A new approach for extracting the pure phase effect from the mixed images is presented. In this work, a normalized imaging formula independent of the light intensity is derived for the polychromatic case. Taking both photoelectric and Compton interactions into account, the attenuation effects at 70 and 50 kVp for borosilicate pyrex, air, and water are accurately calculated and shown to be stable across these substances. The attenuation effect at the interface can be greatly weakened by the subtraction of the attenuation effects of two normalized images, thus revealing details of the phase effect. The experimental results show that this approach is valid.

  3. 'Edge illumination' in X-ray Phase Contrast Imaging

    SciTech Connect

    Munro, Peter R. T.; Ignatyev, Konstantin; Diemoz, Paul C.; Szafraniec, Magdalena B.; Hagen, Charlotte K.; Millard, Thomas P.; Zapata, Cesar E.; Speller, Robert D.; Olivo, Alessandro [Department of Medical Physics and bioengineering, UCL, London WC1E 6BT (United Kingdom)

    2012-07-31

    In the late '90s, the concept of 'edge illumination' was developed at ELETTRA in Italy as an alternative method to increase the phase sensitivity of an imaging system. The main idea was to be able to reproduce the fine angular selection of 'analyzer' crystals without actually using a crystal, as this would allow employing the method with divergent and polychromatic (i.e. conventional) x-ray sources. It was observed that this could be achieved by illuminating only the edges of the detector pixels, and that the method's sensitivity could be progressively increased by illuminating smaller pixel fractions closer to its physical edge. A few years later the idea was adapted for use with a conventional source by means of two sets of x-ray masks ('coded aperture' masks), which enabled obtaining the same effect for each row (or column) of pixels of an area detector illuminated by a cone beam. This article reviews the method and presents recent examples of application.

  4. Simplified approach for quantitative digital holographic phase contrast imaging of living cells

    NASA Astrophysics Data System (ADS)

    Kemper, Björn; Vollmer, Angelika; Rommel, Christina E.; Schnekenburger, Jürgen; Bally, Gert Von

    2011-02-01

    Many interferometry-based quantitative phase contrast imaging techniques require a separately generated coherent reference wave. This results in a low phase stability and the demand for a precise adjustment of the intensity ratio between object and reference wave. To overcome these problems, the performance of a Michelson interferometer approach for digital holographic microscopy was analyzed that avoids a separately generated reference wave by superposition of different image areas. It is shown that this simplified arrangement yields improved phase stability. Furthermore, results from time-lapse investigations on living pancreas tumor cells demonstrate the capability of the method for reliable quantitative phase contrast imaging.

  5. Quantitative evaluation of annular bright-field phase images in STEM.

    PubMed

    Ishida, Takafumi; Kawasaki, Tadahiro; Tanji, Takayoshi; Ikuta, Takashi

    2015-04-01

    A phase reconstruction method based on multiple scanning transmission electron microscope (STEM) images was evaluated quantitatively using image simulations. The simulation results indicated that the phase shift caused by a single atom was proportional to the 0.6th power of the atomic number Z. For a thin SrTiO3 [001] crystal, the reconstructed phase at each atomic column increased according to the specimen thickness. The STEM phase images can quantify the oxygen vacancy concentration if the thickness is less than several nanometers. PMID:25568080

  6. Retrofit implementation of Zernike phase plate imaging for cryo-TEM

    PubMed Central

    Marko, Michael; Leith, ArDean; Hsieh, Chyongere; Danev, Radostin

    2011-01-01

    In-focus phase-plate imaging is particularly beneficial for cryo-TEM because it offers a substantial overall increase in image contrast, without an electron dose penalty, and it simplifies image interpretation. We show how phase-plate cryo-TEM can be implemented with an appropriate existing TEM, and provide a basic practical introduction to use of thin-film (carbon) phase plates. We point out potential pitfalls of phase-plate operation, and discuss solutions. We provide information on evaluating a particular TEM for its suitability. PMID:21272647

  7. Development of Fourier domain optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Wang, Rui

    Fourier domain optical coherence tomography (FD-OCT) is a high-speed, high-resolution, and noninvasive imaging technique that can obtain cross-sectional images of light scattering medium, such as biomedical tissues. In this thesis, I report three novel methods in FD-OCT technique including common-path endoscopic FD-OCT, streak-mode FD-OCT, and Doppler streak-mode FD-OCT. Finally, I apply the streak mode FD-OCT to ultrahigh-speed, noninvasive, live imaging of embryonic chick hearts. An extension of conventional FD-OCT technique is endoscopic FD-OCT, which can access internal organs by utilizing a miniaturized catheter design. However, its image signal suffers from the bending of the endoscopic catheter. To address this problem, a common-path endoscopic FD-OCT system was developed to avoid the polarization mismatch. Consequently, the OCT images were immune to the catheter bending. In addition, a Microelectromechanical system (MEMS) motor was integrated into the miniaturized probe to achieve circumferential scanning within lumen samples. In conventional FD-OCT, the imaging speed is limited by the slow line-scan rate of the camera. We developed the streak-mode FD-OCT technique, in which an area-scan camera is used instead of a line-scan camera to record the FD-OCT spectrum. Using this technique, high temporal resolution of 1000--2000 cross-sectional images of the sample were obtained in one second. Doppler FD-OCT is a functional extension of FD-OCT technique, which can measure the flow velocity within biomedical tissues. However, conventional techniques are not available to measure high speed flow due to slow imaging speed, phase wrapping, and fringe wash out issues. Based on the streak mode FD-OCT, a novel Doppler technique was developed that addressed these problems. It has been well established that cardiac dynamics play an important role in the early development of an embryonic heart. However, the mechanism by which cardiac dynamics affect the development of a peristaltic tube into a four-chambered heart is still unclear. This is mainly due to lack of investigative tools, such as an imaging technique with sufficiently high spatial and temporal resolution. Using streak-mode FD-OCT, 4D (3D + time) images of beating hearts have been reconstructed. This marks the first time that the embryonic animal heart has been 4D imaged using a megahertz OCT.

  8. Measurements of liquid-phase turbulence in gas-liquid two-phase flows using particle image velocimetry

    NASA Astrophysics Data System (ADS)

    Zhou, Xinquan; Doup, Benjamin; Sun, Xiaodong

    2013-12-01

    Liquid-phase turbulence measurements were performed in an air-water two-phase flow loop with a circular test section of 50 mm inner diameter using a particle image velocimetry (PIV) system. An optical phase separation method--planar laser-induced fluorescence (PLIF) technique—which uses fluorescent particles and an optical filtration technique, was employed to separate the signals of the fluorescent seeding particles from those due to bubbles and other noises. An image pre-processing scheme was applied to the raw PIV images to remove the noise residuals that are not removed by the PLIF technique. In addition, four-sensor conductivity probes were adopted to measure the radial distribution of the void fraction. Two benchmark tests were performed: the first was a comparison of the PIV measurement results with those of similar flow conditions using thermal anemometry from previous studies; the second quantitatively compared the superficial liquid velocities calculated from the local liquid velocity and void fraction measurements with the global liquid flow rate measurements. The differences of the superficial liquid velocity obtained from the two measurements were bounded within ±7% for single-phase flows and two-phase bubbly flows with the area-average void fraction up to 18%. Furthermore, a preliminary uncertainty analysis was conducted to investigate the accuracy of the two-phase PIV measurements. The systematic uncertainties due to the circular pipe curvature effects, bubble surface reflection effects and other potential uncertainty sources of the PIV measurements were discussed. The purpose of this work is to facilitate the development of a measurement technique (PIV-PLIF) combined with image pre-processing for the liquid-phase turbulence in gas-liquid two-phase flows of relatively high void fractions. The high-resolution data set can be used to more thoroughly understand two-phase flow behavior, develop liquid-phase turbulence models, and assess high-fidelity codes for multi-phase flows.

  9. Process for rapid detection of fratricidal defects on optics using Linescan Phase Differential Imaging

    SciTech Connect

    Ravizza, F L; Nostrand, M C; Kegelmeyer, L M; Hawley, R A; Johnson, M A

    2009-11-05

    Phase-defects on optics used in high-power lasers can cause light intensification leading to laser-induced damage of downstream optics. We introduce Linescan Phase Differential Imaging (LPDI), a large-area dark-field imaging technique able to identify phase-defects in the bulk or surface of large-aperture optics with a 67 second scan-time. Potential phase-defects in the LPDI images are indentified by an image analysis code and measured with a Phase Shifting Diffraction Interferometer (PSDI). The PSDI data is used to calculate the defects potential for downstream damage using an empirical laser-damage model that incorporates a laser propagation code. A ray tracing model of LPDI was developed to enhance our understanding of its phase-defect detection mechanism and reveal limitations.

  10. Depth-Resolved And Contrast Enhanced Optical Coherence Imaging Using Phase Coherent Photorefractive Quantum Wells

    NASA Astrophysics Data System (ADS)

    Kabir, A.; Dongol, A.; Wang, X.; Wagner, H. P.

    2011-12-01

    We demonstrate two complementary real-time optical coherence imaging acquisition modes using all-optical phase coherent photorefractive ZnSe quantum wells. Real-time three-dimensional particle tracking of glass beads in solution as well as imaging beads in contrast enhanced mode demonstrate the potential of these quantum wells for time-resolved holographic imaging.

  11. Medical phase contrast x-ray imaging: current status and future prospects

    Microsoft Academic Search

    R. A. Lewis

    2004-01-01

    The exploitation of phase contrast appears to offer the tantalising possibility of creating the biggest change in medical x-ray imaging since the invention of computed tomography. A considerable number of experiments performed by researchers across four continents have produced some extraordinary images. These images have demonstrated greatly enhanced contrast over conventional methods revealing soft tissue discrimination at micron scale resolutions.

  12. Characterization of the Phase Contrast Imaging system based on the miniature synchrotron MIRRORCLE-6X

    E-print Network

    van Vliet, Lucas J.

    This article provides a quantitative characteriazation of an X-ray Phase Contrast Imaging (PCI) system based into prototypes of the other imaging modalities of the X-ray PCI family. Currently achievable levels of contrast of the target that can be efficiently used in MIRRORCLE-6X for an X-Ray imaging is of the order of 30 - 40µm

  13. The study of high-resolution imaging of astronomical object based on phase-diversity method

    NASA Astrophysics Data System (ADS)

    Li, Q.; Shen, M. Z.

    2007-01-01

    The high resolution imaging of astronomical object based on phase-diversity method is a technique for obtaining estimates of both the object and the distribution of wavefront induced by atmospheric turbulence,by exploiting the simultaneous collection of one or more pairs of short-exposure images. One of the pair images is the conventional focal-plane image and another is formed by further blurring the focal-image by defocus.The telescopic optical system and image collection system of phase-diversity method are simulated by using computer in this paper. Based on signal estimation theory and optimization theory, the objective function is derived under additive Gaussian noise model. The resulting large scale unconstrained optimization problem is solved numerically using a limited memory BFGS method. The restoring results demonstrate that the phase-diversity method is remarkably efficient for removing the effect of atmospheric turbulence and solving the image restoration problem of astronomical extended object.

  14. X-ray elastography: Modification of x-ray phase contrast images using ultrasonic radiation pressure

    SciTech Connect

    Hamilton, Theron J.; Bailat, Claude; Rose-Petruck, Christoph; Diebold, Gerald J. [Department of Chemistry, Brown University, Providence, Rhode Island 02912 (United States); Gehring, Stephan; Laperle, Christopher M.; Wands, Jack [Liver Research Center, Warren Alpert School of Medicine and Rhode Island Hospital, Brown University, Providence, Rhode Island 02912 (United States)

    2009-05-15

    The high resolution characteristic of in-line x-ray phase contrast imaging can be used in conjunction with directed ultrasound to detect small displacements in soft tissue generated by differential acoustic radiation pressure. The imaging method is based on subtraction of two x-ray images, the first image taken with, and the second taken without the presence of ultrasound. The subtraction enhances phase contrast features and, to a large extent, removes absorption contrast so that differential movement of tissues with different acoustic impedances or relative ultrasonic absorption is highlighted in the image. Interfacial features of objects with differing densities are delineated in the image as a result of both the displacement introduced by the ultrasound and the inherent sensitivity of x-ray phase contrast imaging to density variations. Experiments with ex vivo murine tumors and human tumor phantoms point out a diagnostic capability of the method for identifying tumors.

  15. SLM-based off-axis Fourier filtering in microscopy with white light illumination.

    PubMed

    Steiger, Ruth; Bernet, Stefan; Ritsch-Marte, Monika

    2012-07-01

    In various microscopy applications spatial light modulators (SLMs) are used as programmable Fourier filters to realize different optical contrast enhancement methods. It is often advantageous to use the SLM in off-axis configuration, where the filtered image wave is sent into the first diffraction order of a blazed grating superposed to the phase mask on the SLM. Because of dispersion this approach is, however, typically limited to spectrally narrowband illumination. Here we suggest a method involving a grating for pre-compensation, which allows one to use spectrally broadband (even thermal) light in SLM-based Fourier filtering. The proposed approach is demonstrated by multicolor imaging of amplitude and phase objects, such as a resolution target, onion epidermal cells and human epithelial cheek cells. PMID:22772234

  16. Windowed Fourier transform as an essential digital interferometry tool to study coupled heat and mass transfer

    NASA Astrophysics Data System (ADS)

    Ahadi, Amirhossein; Khoshnevis, Ahmad; Saghir, M. Ziad

    2014-04-01

    Series of thermodiffusion experiments using optical digital interferometry (ODI) have been conducted onboard the International Space Station. Conventionally, the two-dimensional (2D) fast Fourier transform (FFT) fringe analysis technique has been applied as a fast and reliable technique to extract data. In this study, for the first time, the windowed Fourier transform (WFT) method is used to analyze the same experiments. In this method, a Fourier transformation is applied on the fringes at two different stages: initially, during the filtration of the non-zero peaks and then on the wrapped phase image. We provide a detailed comparison between FFT and WFT results of binary and ternary mixtures for ODI thermodiffusion experiments. The substantial enhancements of this method are presented and discussed for different experiments conducted for both binary and ternary mixtures. We show that while disturbances in the phase fringe pattern can cause significant error in FFT techniques, if the windowed Fourier filtration (WFF) parameters are properly chosen this type of noise can be eliminated during WFF analysis. The importance of replacing the FFT method becomes more pronounced for the ternary system, as this method fails to reconcile reliable concentration profiles. The results of this work can show that the application of the windowed Fourier transform in optical digital interferometry investigations show improved results over the same experiments analyzed using FFT methods, especially for experiments involving very small heat and mass fluxes such as the Soret effect in multicomponent mixtures.

  17. Buffered Fourier domain mode locking: unidirectional swept laser sources for optical coherence tomography imaging at 370,000 lines\\/s

    Microsoft Academic Search

    Robert Huber; Desmond C. Adler; James G. Fujimoto

    2006-01-01

    We describe buffered Fourier domain mode locking (FDML), a technique for tailoring the output and multiplying the sweep rate of FDML lasers. Buffered FDML can be used to create unidirectional wavelength sweeps from the normal bidirectional sweeps in an FDML laser without sacrificing sweep rate. We also investigate the role of the laser source in dynamic range versus sensitivity performance

  18. Hard-x-ray phase-imaging microscopy using the self-imaging phenomenon of a transmission grating

    NASA Astrophysics Data System (ADS)

    Yashiro, Wataru; Harasse, Sebastien; Takeuchi, Akihisa; Suzuki, Yoshio; Momose, Atsushi

    2010-10-01

    We report on a hard-x-ray imaging microscope consisting of a lens, a sample, and a transmission grating. After the theoretical framework of self-imaging phenomenon by the grating in the system is presented, equations for the electric field on the image plane are derived for ideal and real lenses and an equation for the intensity on the image plane for partially coherent illumination is derived. The equations are simple and similar to those applying to a projection microscope consisting of a transmission grating except that there is no defocusing effect, regardless of whether the grating is in front of or behind the lens. This means that x-ray phase-imaging microscopy can be done without the defocusing effect. It is also shown that, by resolving the self-image on the image plane, high-sensitive x-ray phase-imaging microscopy can be attained without degradation in the spatial resolution due to diffraction by the grating. Experimental results obtained using partially coherent illumination from a synchrotron x-ray source confirm that hard-x-ray phase-imaging microscopy can be quantitatively performed with high sensitivity and without the spatial resolution degradation.

  19. Fourier plane filters

    NASA Technical Reports Server (NTRS)

    Oliver, D. S.; Aldrich, R. E.; Krol, F. T.

    1972-01-01

    An electrically addressed liquid crystal Fourier plane filter capable of real time optical image processing is described. The filter consists of two parts: a wedge filter having forty 9 deg segments and a ring filter having twenty concentric rings in a one inch diameter active area. Transmission of the filter in the off (transparent) state exceeds fifty percent. By using polarizing optics, contrast as high as 10,000:1 can be achieved at voltages compatible with FET switching technology. A phenomenological model for the dynamic scattering is presented for this special case. The filter is designed to be operated from a computer and is addressed by a seven bit binary word which includes an on or off command and selects any one of the twenty rings or twenty wedge pairs. The overall system uses addressable latches so that once an element is in a specified state, it will remain there until a change of state command is received. The drive for the liquid crystal filter is ? 30 V peak at 30 Hz to 70 Hz. These parameters give a rise time for the scattering of 20 msec and a decay time of 80 to 100 msec.

  20. Analyzing Signals Fourier transform

    E-print Network

    Sweldens, Wim

    Page 1 1 Analyzing Signals Fourier transform s frequency content s linear combination of sin frequency analysis s windowed Fourier transform 6 #12;Page 4 7 Gabor Transform function to analyze window Gabor Transform Spatial domain Gabor domain b #12;Page 5 9 Gabor Transform Problems s discrete version