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. ...
PubMed
... All phase information is suppressed. The fast Fourier transform is taken with respect to the intensity distribution of the input image only. ...
DTIC Science & Technology
... We take the discrete Fourier transform of an image and determine a signature based upon a binary phase-only filter (BPOF). ...
The problem of reconstructing a positive semi-definite 3-D image from the measurement of the magnitude of its 2-D fourier transform at a series of orientations is explored. The phase of the fourier transform is not measured. The algorithm developed here u...
National Technical Information Service (NTIS)
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 ...
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 ...
ERIC Educational Resources Information Center
The direct Fourier phase averaging of an ensemble of randomly blurred images has long been thought to be too difficult a problem to undertake realistically owing to the necessity of proper phase unwrapping. It is shown that it is nevertheless possible to average the Fourier ...
Energy Citations Database
This is the beginning step of the procedure. You first need to calculate the Fourier Transform (IT) and the Power Spectrum (PS) of the image that you want to analyze. The Fourier Transform of the image is hidden and all the actual operations take place on...
We present the observation of the activity of artemia, one of the popular marine micro-biota species, in free space by the application of Fourier optics imaging technique The Fourier optic imaging system is consisted by a collimated laser beam source, a F...
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/LIDAR systems, Fourier Transf...
The bispectrum is the natural third-order generalization of the power spectrum. It provides information about correlations between different Fourier components of a signal or image, and about the statistics of Fourier phase. A number of numerical and expe...
We describe our new method for watermarking digital images. Our work is motivated by the study of phase only filters in Fourier optics. In this paper we concentrate on grey scale images, even though our method works for color also. We take the discrete Fo...
The fast Fourier transform, phase iteration, and the least-square fit are combined into an automated processing technique for the analysis of Young's fringe patterns. A Young's fringe pattern is first fast-Fourier-transform filtered to get an initial phase, phase iteration is carried out to ...
We propose a method to encrypt two covert images into an overt image based on phase-truncated Fourier transforms and phase retrieval. In this method, the two original images are self-encoded in the manner that one of the two images is directly separated ...
NASA Astrophysics Data System (ADS)
A new optical image encryption method based on anamorphic fractional Fourier transform (FRT) and phase-shifting interferometry (PSI) is proposed in this paper. The input two-dimensional image to be encrypted is anamorphic fractional Fourier transformed with different orders in the two ...
We present an image encryption algorithm to simultaneously encrypt two images into a single one as the amplitudes of fractional Fourier transform with different orders. From the encrypted image we can get two original images independently by fractional Fourier transforms ...
First-harmonic Fourier analysis of a gated blood-pool study is based on the assumption that the cardiac chambers contract once per cardiac cycle. In atrial arrhythmias this condition may not exist for the atria. We recently studied a patient with atrial flutter and 2:1 artioventricular conduction. There were predictable alterations in the first-harmonic ...
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 ...
The problem of reconstructing a positive semi-definite 3-D image from the measurement of the magnitude of its 2-D fourier transform at a series of orientations is explored. The phase of the fourier transform is not measured. The algorithm developed here utilizes a Hamiltonian, or cost function, that at its minimum ...
DOE Information Bridge
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 ...
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 ...
PubMed Central
Magnetic resonance images are typically displayed as the absolute value of the discrete Fourier transform of the k-space data. However, absorption-mode images, the real part of the discrete Fourier transform of the data after applying an appropriate phase correction, have significant advantages ...
A new color image encryption algorithm based on fractional Fourier transform (FrFT) and chaos is proposed. The colors of the original color image are converted to HSI (hue-saturation-intensity), and the S component is transformed by the random-phase encoding based on FrFT to obtain a new random ...
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 ...
A technique for simultaneous encryption of a color and a gray-scale image is proposed, using single-channel double random-phase encoding in the fractional Fourier domain. Prior to the encryption, the segregated red, green, and blue components of the color image and the gray-scale image are ...
An improved efficient projection of color images is presented. It uses a phase spatial light modulator with three iteratively optimized Fourier holograms displayed simultaneously-each for one primary color. This spatial division instead of time division provides stable images. A pixelated structure of the modulator ...
A novel single-channel color image encryption technique based on joint fractional Fourier transform correlator(JFRTC) and phase retrieval algorithm (PRA) is proposed. The target color image is decomposed into three red, green, blue (RGB) components. A joint image is formed and encoded into two ...
and choroid vessels. Variance imaging is subject to bulk motion artifacts as in phase-resolved Doppler imaging and extra Hilbert/Fourier calculation besides the phase- resolved Doppler calculation. Furthermore, low-based algorithm is used to extract and cor- rect the bulk-motion ...
E-print Network
The ultrasonic imaging attained a special importance in all science areas during the recent years. The development of this area is stimulated by the creation of flexible systems using acoustic phase array (matrix) technology. It is of great importance for applications in the systems for imaging of human organs.
Pure far-field correlated thermal light beams are created with phase grating, and Fourier-transform ghost imaging depending only on the far-field correlation is demonstrated experimentally. Theoretical analysis and the results of experimental investigation of this pure far-field correlated thermal light are presented. Applications ...
retarders, liquid crystal achromatic phase switch. ABSTRACT ... 4000 cm-') to allow high-resolution, high-speed hyperspectral imaging applications [l-51. ... made of a birefringent material, the speed difference in refraction indexes ...
NASA Website
Using a RF pulse with linear frequency sweep and a simultaneous encoding gradient, magnetization is sequentially excited accompanied by a quadratic phase profile. This quadratic dependence of magnetization phase on position dephases magnetization away from its vertices, allowing direct spatial encoding and image formation in the time ...
Pulse Phase Thermography (PPT) has been reported as a novel powerful technique of the thermal NDE. It employs application of the Discrete Fourier Transform (DFT) to thermal images obtained following flash heating of the front surface of a specimen. The co...
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 ...
Based on joint transform correlator (JTC) architecture and holographic techniques, a new method for image hiding is presented. A hidden image encrypted by JTC architecture is embedded in the Fourier hologram of the host image. Inverse Fourier transform can be used to obtain the watermarked ...
We propose an optical image watermarking algorithm based on fractional Fourier transform and random phase encoding. The proposed watermarking can be exactly implemented in optics and the secret key is passively generated by the proposed algorithm. In the packaged watermarking system, the host image is unchanged in ...
... FOURIER-BASED RADAR IMAGING TECHNIQUES ... In most current implementations of radar imaging, the images are generated using narrow ...
Fourier Sampling in the NRLA. " The frequency content of each snapshot image is found by. Fourier analysis. " The Fourier domain of the NRLA is known ...
A new optical encryption technique based on computer-generated hologram (CGH) and fractional Fourier transform (FRT) is presented. And the algorithm of making asymmetry FRT CGH is provided in this paper. In this method, the fractional Fourier transform of the input image is performed by two one-dimensional FRT with different orders in ...
The analysis of EKG gated radionuclide cardiac imaging data with Fourier amplitude and phase images is becoming a valuable clinical technique, demonstrating location, size, and severity of regional ventricular abnormalities. Not all commercially available nuclear medicine computer systems offer software for ...
In recent years, the chaos-based cryptographic algorithms have suggested some new and efficient ways to develop secure image encryption techniques. In this paper, we propose a new approach for image encryption based on the multiple-parameter discrete fractional Fourier transform and chaotic logistic maps in order to meet the ...
A holographic technique is applied for digital watermarking by a computer. A digital-watermark image to be hidden is phase modulated in a random fashion, and its Fourier-transformed hologram is superposed on a content image. The watermark is reconstructed by means of a holographic-reconstruction technique from the ...
PurposeTo present a single-step deterministic procedure for unwrapping MRI phase maps.Materials and MethodsUsing an algorithm previously developed for optical applications, Laplacian operators were applied in the Fourier space of the MRI phase map. The original Fourier-based phase unwrapping ...
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 ...
... MOTION, HIGH RESOLUTION, ITERATIONS, DISTORTION, DIFFRACTION ANALYSIS, FOURIER ANALYSIS, RECONNAISSANCE SATELLITES ...
... Descriptors : *INTERFEROMETRY, *MITOCHONDRIA, METABOLISM, SPECTRUM ANALYSIS, FOURIER SPECTROSCOPY. ...
... INTEGRAL TRANSFORMS, ALGORITHMS), (*COMPUTER PROGRAMMING, NUMERICAL ANALYSIS), FOURIER ANALYSIS, NUMERICAL ...
We propose a Fourier-plane encryption technique based on a joint transform correlator (JTC). The technique is based on removing the effect of phase terms in JTC and the auto-correlation terms contribute to reconstructing the original image. Computer simulations and optical experiments show the proposed method is very useful for JTC ...
... Descriptors : (*INTERFEROMETERS, SPECTROSCOPY), (*SPECTROSCOPY, FOURIER ANALYSIS), (*FOURIER ANALYSIS, SPECTROSCOPY ...
... Title : A FOURIER TRANSFORM TECHNIQUE THAT MEASURES PHASE DELAYS BETWEEN ULTRASONIC IMPULSES WITH SUFFICIENT ...
A method, novel to our knowledge, for effective mirror image suppression in Fourier-domain optical coherence tomography based on a phase shift between neighboring A-mode scans is demonstrated. By realizing that the phase shifts of the real and mirror images are mutually reversed and assuming ...
A new approach to the interpolation of three-dimensional (3D) medical images is presented. Instead of going through the conventional interpolation scheme where the continuous function is first reconstructed from the discrete data set and then resampled, the interpolation is achieved with a subunity coordinate translation technique. The original image is ...
Usually edge enhancement of optical images is produced by introduction of loss into the low spatial frequency components of the image-bearing beam in the Fourier plane of a lens. We report on edge-enhanced phase-conjugate images from a mutually pumped conjugator accomplished by spatial ...
A new cryptology in dual fractional Fourier-wavelet domain is proposed in this paper, which is calculated by discrete fractional Fourier transform and wavelet decomposition. Different random phases are used in different wavelet subbands in encryption. A new color image encoding method is also presented with basic ...
Complex phase history data in synthetic aperture radar (SAR) systems require extensive processing before useful images can be obtained. In spotlight mode SAR systems, useful images can be obtained by applying aperture weighting and inverse Fourier transform operations to SAR phase history data. ...
We propose to record digital Fourier hologram of a 3D diffused object and to reconstruct numerically and optically by using phase-only information. This phase-only information is obtained by using 1D-Continuous Wavelet Transform (1DCWT) from the intensity of digital Fourier Hologram. 3D object ...
... to) - Title and Subtitle Fourier Interferometry/Spectral Imaging of Response to Metabolic Challenges in Perinuclear Mitochondria of Normal and ...
This patent describes a method of reducing artifacts in NMR images due to motion-induced phase errors in the phase-encoding dimension when using Fourier transform imaging pulse sequences. The method consists of determining the respiration cycle of the subject to be scanned, and selecting a ...
The optical image encryption based on multichannel fractional Fourier transform (FRT) and double random phase encoding technique is proposed. Optical principles of encoding and decoding are analyzed in detail. With this method, one can encrypt different parts of input image, respectively. The system security can be ...
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 ...
... USING A DISCRETE FOURIER TRANSFORM TO ESTIMATE PHASE [N INTERFEROMETRIC DIRECTION FINDING by Gareth J.Parker ...
We describe a design method for a binary-phase Fourier grating that generates an array of spots with
NASA Technical Reports Server (NTRS)
... Title : Application of a Fourier Transform-Phase-Slope Technique to the Design of an Instrument for the Ultrasonic Measurement of Texture and ...
The Fourier inversion of phased coherent diffraction patterns offers images without the resolution and depth-of-focus limitations of lens-based tomographic systems. We report on our recent experimental images inverted using recent developments in phase retrieval algorithms, and summarize ...
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 ...
We demonstrate experimentally that correct phase imaging without 2pi ambiguity is obtainable in digital holography by using a multiwavelength approach in the microscope configuration. We describe a general approach for removing chromatic aberrations and for controlling the pixel size of the reconstructed phase ...
Magnetic resonance temperature imaging can be used to monitor the progress of thermal ablation therapies, increasing treatment efficacy and improving patient safety. High temporal resolution is important when therapies rapidly heat tissue, but many approaches to faster image acquisition compromise image resolution, slice coverage, or ...
A nonlinear scene analysis algorithm is studied for complex scenes containing realistic targets and background clutter. Infrared and visible spectrum light images are processed. The algorithm combines the Fourier transform phase array of a scene with the ...
A new security system is proposed using optical joint transform correlation technique which employs multiple phase-shifted reference images. In the proposed technique, the address code is used as the reference image and fed into four channels after performing phase shifting on them by different amount. The output ...
An affine mapping mathematical expression of the double-random-phase encryption technique has been deduced utilizing the matrix form of discrete fractional Fourier transforms. This expression clearly describes the encryption laws of the double-random-phase encoding techniques based on both the fractional Fourier ...
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 ...
Optical deflectometry, likewise many other optical methods, permits to reconstruct the wavefront deformations induced by a refractive or a phase object. In this paper, a Fourier based deflectometry method is presented. A telecentric imaging system acquires pictures of a grating being the superposition of two crossed Ronchi rulings of ...
Understanding of biological cell response is facilitated by microscopy techniques, but has been limited by our ability to image cell structure and function at the same time. Current procedure is to obtain separate images, such as phase and fluorescence features, using different imaging techniques one after the ...
We performed a series of experiments using the Air Force Maui Optical Station's 1.6 m telescope and a bare CCD detector to capture speckle images of various satellites. The speckle images were processed with bispectral techniques for recovering image Fourier phase as well as projection ...
We performed a series of experiments using the Air Force Maui Optical Station`s 1.6 m telescope and a bare CCD detector to capture speckle images of various satellites. The speckle images were processed with bispectral techniques for recovering image Fourier phase as well as projection onto ...
We proposed a method to implement spatial phase-shift patterns with subdiffraction limited features through a holographic projection system. The input device of the system displayed phase-only diffractive optical elements that were calculated using the iterative Fourier-transform algorithm with the dummy-area method. By carefully ...
We demonstrate the retrieval of column-density images of cold atoms, using a noninterferometric phase-recovery technique based on a single off-resonant and defocused intensity image. The quantitative column density is retrieved via Fourier inversion and remains robust with respect to detuning and defocus. The ...
Recently, a category of watermarking techniques based on binary phase-only filter (BPOF) has been proposed for image authentication. In such techniques, the authentication is implemented by evaluating the correlation between Fourier phase information and the hidden watermark bitplane. In this paper, we reveal the ...
This paper presents a palmprint recognition algorithm using Phase-Only Correlation (POC). The use of phase components in 2D (two-dimensional) discrete Fourier transforms of palmprint images makes it possible to achieve highly robust image registration and matching. In the proposed algorithm, ...
The security of the encryption and verification techniques with significant output images is examined by a known-plaintext attack. We introduce an iterative phase-retrieval algorithm based on multiple intensity measurements to heuristically estimate the phase key in the Fourier domain by several ...
Conventionally a holographic data storage system uses binary digital data as the input pages. We propose and demonstrate the use of a holographic data storage system for the purpose of invariant pattern recognition of gray-scale images. To improve the correlation accuracy for gray-scale images, we present a coding technique, phase ...
We present the observation of the activity of artemia, one of the popular marine micro-biota species, in free space by the application of Fourier optics imaging technique. The Fourier optic imaging system is consisted by a collimated laser beam source, a Fourier spatial filter, an non-coherent ...
Based on fractional Fourier transform, the double folding operation is studied and introduced into image encryption. This method can implement a kind of the encoding with real number. This characteristic is convenient to the storage and transmission of the encrypted image. The corresponding experimental setup is similar to the scheme ...
The classical double random phase encoding technique (DRPE) is vulnerable to chosen ciphertext attacks, known-plaintext attacks and chosen-plaintext attacks for its linearity. In order to avoid the disadvantages originated from the linearity and symmetric, an improved method for multiple-image encryption based on nonlinear operations in ...
In this work we study the properties offered by holographically recorded volume gratings when applied to image processing in imaging systems. Angular selectivity due to Bragg diffraction modifies the transfer function of the imaging system and spatial filtering operations are performed with no need of a Fourier ...
The resolution of a standard telescope imaging system is severely limited by temperature-gradient induced phase fluctuations in the atmosphere. Short exposure images, however, during which the atmosphere is effectively frozen, contain diffraction-limited resolution information about the object. Techniques for extracting this ...
In vacuum high-intensity lasers can cause photon-photon interaction via the process of virtual vacuum polarization which may be measured by the phase velocity shift of photons across intense fields. In the optical frequency domain, the photon-photon interaction is polarization-mediated described by the Euler-Heisenberg effective action. This theory predicts the vacuum ...
In this paper, we propose a simple method for processing a 2D wrapped phase map that contains a spatial carrier signal in order to completely eliminate, or greatly reduce, the number of phase wraps in the image. The 2D Fourier transform of the wrapped phase map is calculated. Then the spectrum ...
In this paper a binary image encryption technique and decryption system based on a joint transform correlation are proposed. IN this method, an encrypted image is obtained by multiplying a phase encoded original binary image with a random phase. A Fourier transform of the ...
We present a new optical image encryption algorithm that is based on extended fractional Fourier transform (FRT) and digital holography technique. We can perform the encryption and decryption with more parameters compared with earlier similar methods in FRT domain. In the extended FRT encryption system, the input data to be encrypted is extended fractional ...
We consider the reconstruction of a complex-valued object that is coherently illuminated and then viewed through a random-phase screen. The reconstruction involves a phase retrieval based on two intensity measurements. The first is a measurement of the long-exposure averaged intensity of a Fourier transform of the ...
This paper presents an efficient algorithm for iris recognition using phase-based image matching--an image matching technique using phase components in 2D Discrete Fourier Transforms (DFTs) of given images. Experimental evaluation using CASIA iris image ...
Optical snapshot images of photo-acoustically generated sound waves in a water tank can be obtained by 'spiral phase contrast filtering', a variant of phase contrast imaging. To this end a two-dimensional transmission image of the ultrasonic field is recorded by illuminating the water volume by ...
OBJECTIVES: To present a method called Fourier image (FI) for analyzing high-speed videoendoscopy recordings. These false-color images visualize functional vocal fold properties and allow the quantification of phase relations. Furthermore, reference data for phase asymmetries in normophonic ...
A capability for measuring optical phase from holographic interferograms based on the Fourier transform is described. Video images of interferograms are digitized into 0-225 grey level intensity arrays nominally 1000 pixels square. The optical phase for each pixel which generates high-resolution ...
X-ray phase-contrast imaging is a technique that aims to reconstruct the projected absorption and refractive index distributions of an object. One common feature of reconstruction formulas for phase-contrast imaging is the presence of isolated Fourier domain singularities, which can greatly ...
Frequency-variable illumination has been used previously to provide high resolution imaging in one dimension. The paper extends the results on this imaging by frequency scanning to derive the expression for a two-dimensional image. This is the Fourier transformation, with respect to the angle and frequency of ...
SAR phase history data represents a polar array in the Fourier space of a scene being imaged. Polar Format processing is about reformatting the collected SAR data to a Cartesian data location array for efficient processing and image formation. In a real-t...
A complex image with constraints imposed on the amplitude and phase image components is processed using the Gerchberg iterative algorithm for the first time. The use of the Gerchberg iterative algorithm makes it possible to improve the quality of a three-dimensional surface profile reconstructed by the previously proposed method that ...
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 ...
A digital frequency ramping method (DFRM) is proposed to improve the signal-to-noise ratio (SNR) of Doppler flow imaging in Fourier-domain optical coherence tomography (FDOCT). To examine the efficacy of DFRM for enhancing flow detection, computer simulation and tissue phantom study were conducted for phase noise reduction and flow ...
The structure and dynamics of soft matter were studied by differential dynamic optical microscopy. One can retrieve q-space information through image processing and Fourier analysis, even when the feature sizes in real space image are too small to be resolved or even visible in an optical microscope. The temporal sequence of real space ...
When measuring a three-dimensional shape with triangulation and projected interference fringes it is of interest to reduce speckle contrast without destroying the coherence of the projected light. A moving aperture is used to suppress the speckles and thereby reduce the phase error in the fringe image. It is shown that the phase error ...
In this paper, dynamic liquid surface measurements using non-disturbing technique based on interferogram analysis with moiré method are described. A sequence of dynamic deformed fringe images can be grabbed by a phase-shifting interferometer (PSI) and saved on disk rapidly. By Fourier transform, filtering, ...
Abstract: JPL is developing a compact, low mass, Electro-Optic Imaging Fourier Transform Spectrometer (E-O IFTS) for hyperspectral imaging applications. ...
Microorganisms, cells and thin tissue sections are transparent and not visible to view in ordinary microscope. Techniques such as phase contrast and Normarski/Differential interference contrast microscopy transform the phase variation information into intensity distribution to reveal the details of internal structures. Similarly fluorescence microscope ...
... Figure 2 Fourier transform of the function shown in Figure 1 ... best to shift the mirror a fraction of a ... produce negative harmonics in the Fourier image of ...
... more significant in other parts of the plume. ... FOURIER TRANSFORMATION, *HYPERSPECTRAL IMAGERY, *PLUMES, *TURBULENCE, FLOW ...
... The Discrete Space Fourier Transform of the sampled image is a periodic extension of the Continuous Space Fourier Transform of the pseudo ...
... NONLINEAR SYSTEMS, RADIANCE, SKY, DEEP WATER, SYNTHESIS, POLARIZATION, FOURIER ANALYSIS, MATHEMATICAL MODELS ...
We report a new synthetic aperture optical microscopy in which high-resolution, wide-field amplitude and phase images are synthesized from a set of Fourier holograms. Each hologram records a region of the complex two-dimensional spatial frequency spectrum of an object, determined by the illumination field�s spatial and spectral ...
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 ...
The interference between repeated Landau-Zener transitions in a qubit swept through an avoided level crossing results in St�ckelberg oscillations in qubit magnetization, a hallmark of the coherent strongly driven regime in two-level systems. The two-dimensional Fourier transforms of the resulting oscillatory patterns are found to exhibit a family of one-dimensional curves in ...
... Title : The Significance of the Fourier Analysis in Signal Detection and Processing in Laser Doppler and Phase Doppler Applications,. ...
... Accession Number : ADA112135. Title : Quantitative Fourier Transform IR Photoacoustic Spectroscopy of Condensed Phases,. ...
We demonstrate a single shot two-dimensional grating-based X-ray phase-contrast imaging using a synchrotron radiation source. A checkerboard designed phase grating for ? phase modulation at 17 keV and 35 keV, and a lattice-shaped amplitude grating with a high aspect ratio to shield X-rays up to 35 keV were ...
The authors present a detection process capable of directly imaging the transverse amplitude, phase, and if desired, Doppler shift of coherent electromagnetic fields. Based on coherent detection principles governing conventional heterodyned RADAR/LIDAR systems, Fourier Transform Heterodyne (FTH) incorporates transverse spatial encoding ...
Partial Fourier reconstruction algorithms exploit the redundancy in magnetic resonance data sets so that half of the data is calculated during image reconstruction rather than acquired. The conjugate synthesis, Margosian, homodyne detection, Cuppen and POCS algorithms are evaluated using spatial frequency domain analysis to show their characteristics and ...
A digital technique for multiplexing and encryption of four RGB images has been proposed using the fractional Fourier transform (FRT). The four input RGB images are first converted into their indexed image formats and subsequently multiplexed into a single image through elementary mathematical ...
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), ...
A technique for reconstructing positive and negative images from an identical intensity-modulated hologram is demonstrated theoretically and experimentally by use of a coaxial holographic storage system. Negative images are obtained by adding a phase-modulated dc component of signal beam on reading. By comparing positive and negative ...
An extension of the far-field x-ray diffraction theory is presented by the introduction of a distorted object for calculation of coherent diffraction patterns in the near-field Fresnel regime. It embeds a Fresnel-zone construction on an original object to form a phase-chirped distorted object, which is then Fourier transformed to form a diffraction ...
Synthetic aperture radar (SAR) imaging suffers from image focus degradation in the presence of phase errors in the received signal due to unknown platform motion or signal propagation delays. We present a new autofocus algorithm, termed Fourier-domain multichannel autofocus (FMCA), that is derived under a linear ...
For coherent X-ray imaging of pure phase objects we study the reliability of linear relations in phase-retrieval algorithms based on a single intensity map after free-space propagation. For large phase changes and/or large propagation distances we propose two venues of working beyond linearity: Projection onto an ...
An anti-noise subpixel algorithm of phase-shifting of fundamental frequency was presented based on the phase-shifting of Fourier transform and the anti-noise characteristics of low-frequency part of the phase spectrum of the image. The essence of the algorithm is that the displacement ...
There is a continuous demand for the computer generated holograms to give an almost perfect reconstruction with a reasonable cost of manufacturing. One method of improving the image quality is to illuminate a Fourier hologram with a quasi-random, but well known, light field phase distribution. It can be achieved with a lithographically ...
Concepts for unconventional sensors capable of high-resolution imaging and parameter estimation for the SDI midcourse discrimination application were developed. The basic sensor consists of a large filled array of small-aperture receivers that measure a laser-illuminated object's Fourier intensity in the aperture of the receiver. Reconstruction of ...
The third-order optical nonlinearities of semiconductor CdS are investigated using 4f nonlinear image technique with phase object at 745 nm. The measurement method is based on the 4f coherent optical processor system in Fourier optics. The nonlinear parameters of sample can be verified by numerical fitting the nonlinear ...
A swept source based Fourier domain optical Doppler tomography (FDODT) system was developed. The technique is based on a phase resolved method where phase information was retrieved from the reconstructed complex fringe signals. The aliasing effects and artifacts caused by lateral scanning and sample movement were removed with a signal ...
A swept source based Fourier domain optical Doppler tomography (FDODT) system was developed. The technique is based on a phase-resolved method where phase information was retrieved from the reconstructed complex fringe signals. The aliasing effects and artifacts caused by lateral scanning and sample movement were removed with a signal ...
SAR phase history data represents a polar array in the Fourier space of a scene being imaged. Polar Format processing is about reformatting the collected SAR data to a Cartesian data location array for efficient processing and image formation. In a real-time system, this reformatting or ...
The 2-D Fractional Fourier Transform (FRFT) has been shown to be applicable to the Synthetic Aperture Radar (SAR) imaging problem. Streamlined versions presented here makes the 2-D FRFT comparable with and slightly faster than the Range Doppler (RD) and Extended Chirp Scaling (ECS) methods. The 2-D FRFT is streamlined by eliminating redundancy due to the ...
This invention is comprised of an imaging Fourier transform spectrometer having a Fourier transform infrared spectrometer providing a series of images to a focal plane array camera. The focal plane array camera is clocked to a multiple of zero crossing oc...
The recording and numerical reconstruction of digital lensless Fourier hologram is analyzed. Based on the quadratic phase mask of the reconstructed image field the two common methods for phase reconstruction are discussed and compared by computer simulations. The results show that the automatic ...
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 ...
Fourier synthesis (FS) inverse problem consists in reconstructing a multi-variable function from the measured data which correspond to partial and uncertain knowledge of its Fourier Transform (FT). By partial knowledge we mean either partial support and/or the knowledge of only the module and by uncertain we mean both uncertainty of the model and noisy ...
Traditional optical imaging systems rely on lenses and spatially-resolved detection to probe distinct locations on the object. We develop a novel computational approach to 2D and 3D imaging that instead measures the object's spatial Fourier transform using a single-element detector and without requiring precision optics. This ...
This article is concerned with frequency filtering for electronic speckle pattern interferometry wrapped phase patterns. We propose a robust localized Fourier transform filter which is an extension of the root filtering method (RFM). We improve the RFM from a simple technical process and a filter function in the frequency domain. In our method, the ...
The present conference discusses topics in the research fields of multisensor recognition and tracking, optical correlators and pattern recognition, optical processing applications, phase-only filters, digital signal processing techniques, and neural nets for image processing. Attention is given to multisensor data fusion for multitarget tracking, fast ...
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 ...
... In microwave imaging, aperture data are ... Microwave imagery, Image quality, and ... COMPRESSION, *QUALITY, IMAGES, MICROWAVES, FOURIER ...
A new methodology for examining the interactions of microbes with heterogeneous minerals is presented. Imaging laser desorption Fourier transform mass spectrometry was used to examine the colonization patterns of Burkholderia vietnamiensis G4 (previously Burkholderia cepacia G4) on a heterogeneous basalt sample. Depth-profile imaging ...
A new methodology for examining the interactions of microbes with heterogeneous minerals is presented. Imaging laser-desorption Fourier transform mass spectrometry was used to examine the colonization patterns of Burkholderia vietnamiensis (Burkholderia cepacia) G4 on a heterogeneous basalt sample. Depth-profile imaging found that the ...
Symmetry provides a source of redundancy which can be exploited in image reconstruction. In particular, internal symmetries in molecules can help to compensate for the loss of Fourier phase information in macromolecular x-ray crystallography. Symmetry projections are incorporated into iterative projection algorithms for reconstruction ...
We describe the implementation of quantitative Differential Interference Contrast (DIC) Microscopy using a spatial light modulator (SLM) as a flexible Fourier filter in the optical path. The experimental arrangement allows for the all-electronic acquisition of multiple phase shifted DIC-images at video rates which are analyzed to yield ...
We introduce the binary superposed phase retrieval problem that aims at reconstructing multiple 0/1-valued functions with nonoverlapping bounded supports from moduli of superpositions of several displaced copies of their individual Fourier transforms. We discuss an application in coherent diffraction imaging of crystalline objects, ...
The technique of Fourier transform infrared (FT-IR) spectroscopic imaging with focal plane array detectors has proved to be a powerful technique for rapid chemical visualization of samples with a lateral resolution up to about 10 mum. However, the potential of FT-IR imaging for the characterization of anisotropic materials can be ...
In this paper, an optical color image encryption/decryption technology based on joint fractional Fourier transform correlator and double random phase encoding (DRPE) is developed. In this method, the joint fractional power spectrum of the image to be encrypted and the key codes is recorded as the encrypted data. ...
Object identification in deep space is a surveillance mission crucial to our national defense. Satellite health/status monitoring is another important space surveillance task with both military and civilian applications. Deep space satellites provide challenging targets for ground-based optical sensors due to the extreme range imposed by geo-stationary and geo-synchronous orbits. The Air Force ...
We present results from a four-port Michelson interferometer built to demonstrate imaging Fourier transform spectroscopy for astronomical applications.
PROPOSAL TITLE: Electro-Optic Imaging Fourier Transform Spectral Polarimeter ... particularly in improved environmental assessment. ...
... Abstract : In the past decades, picture processing has been developed in two ways: by means of Fourier optical techniques with optical image ...
We have investigated the multiplicity and complexity in eigenvalues of the fractional Fourier transform and found that the ambiguity of the eigenvalues may indicate randomness. We have therefore proposed a method to randomize the Fourier transform. Such a random Fourier transform can be applied in the field of ...
Using the wave nature of X-rays, in-vitro phase-contrast X-ray imaging can clearly reveal the detailed inner structures of cancer in human and rabbit. In this study, using a newly developed imaging system with a two-crystal interferometer and the Fourier data acquisition technique, we presented, for the first time, ...
Fourier phase images have been used with some success to detect and quantify left ventricular (LV) wall motion defects. In abnormal regions of the LV, wall motion asynchronies often cause the time activity curve (TAC) to be shifted in phase. Such regional shifts are detected by analysis of the distribution function ...
Near-surface atoms from a Cu(001) surface were imaged using 3p photo- electron holograms. The angle-dependent electron diffraction patterns that constitute an electron hologram were Fourier transformed to create a tree dimensional, real-space image of the scattering atoms. We have made use of a multiple-wavenumber, ...
A functional Fourier domain optical coherence tomography instrument offering spectral Doppler imaging of in vivo pulsatile human retinal blood flow was constructed. An improved phase-resolved algorithm was developed to correct bulk motion artifacts. Spectral Doppler imaging provides complementary temporal flow ...
Anisotropic properties of materials can be determined by measuring the propagation of elastic waves in different directions. A laser imaging approach is presented that utilizes the adaptive property of photorefractive materials to produce a real-time measurement of the antisymmetric Lamb or flexural traveling wave mode displacement and phase. Continuous ...
A New Fourier-Type Phase Estimation Method for Sensorless Drives of Permanent-Magnet Synchronous Motors
A phase discrimination method for two-phase PIV is presented that is capable of simultaneously separating the two phases from time-resolved stereoscopic PIV images taken in a particle-laden jet. The technique developed expands on previous work done by Khalitov and Longmire (Exp Fluids 32:252-268,
A Talbot-Lau interferometer using two-dimensional gratings and a conventional x-ray tube has been used to investigate a phase-contrast imaging technique that is sensitive to phase gradients in two orthogonal directions. Fourier analysis of Moir� fringe patterns was introduced to obtain differential ...
To form a laser image, there usually are two kinds of image forming methods. One is to direct slender laser beams to special points by light directing element (LDE). The other one is light blocking method where amplitude spatial light modulator (SLM) used to form laser image. The former method has high light efficiency for none light ...
Abstract. The ath-order fractional Fourier transform is a generalization of the ordinary Fourier transform such that the zeroth-order fractional Fourier transform operation is equal to the identity operation and the first-order fractional Fourier transform is equal to the ordinary Fourier ...
Crystals of ion-free gramicidin A (P212121: a = 24.61, b = 32.28, c = 32.52) have been investigated using neutron diffraction. A difference analysis of crystals soaked in ethanol/H2O as opposed to ethanol-d6/D2O has led to single isomorphous replacement Fourier projections of the structure at 5-A resolution. The gramicidin dimer appears to be a 32-A-long cylinder oriented ...
Most partial Fourier (PF) approaches use a low-resolution phase estimate in the reconstruction to account for non-zero phases of the image. These methods may fail when there are large phase errors, a situation commonly encountered in T(*)(2)-weighted functional MRI (fMRI). To mitigate this ...
We present a novel full-field low-coherence interference (LCI) microscope, which exhibits ultra-high axial resolution due to a broadband super continuum light source and which is at the same time capable to generate different contrast modes by using Fourier-plane filtering with a spatial light modulator. By changing the phase and spatial frequencies of the ...
Forty-one patients (25 male, 16 female) were studied by Radionuclide Cardangiography (RNCA) in our institution. There were 42 rest studies and 24 stress studies (66 studies total). Sixteen patients were normal, 15 had ASHD, seven had a cardiomyopathy, and three had left-sided valvular regurgitation. Each study was preprocessed using both the standard nine-point smoothing method and ...
An integrated technique for Fourier analysis in multigated blood pool ECT study has been developed. Following the administration of 15-20 mCi of Tc-99m RBC, ECG-gated cardiac blood pool data were acquired using an ECT system with dual opposed gamma cameras. Fundamental studies for data acquisition showed that acquisition time of 10 sec. for each projection, 14 divisions of one ...
In this paper, we propose a method for optical image encryption based on fractional Fourier transform (FRFT) and Arnold transform (ART) in phase-shifting digital holography. An input image is first divided into eight bit planes, and each bit plane is encrypted based on double random-phase masks ...
Due to high speed moving of the target, the wideband radar echoes after dechirping is a multi-component LFM signal. Directly using the fast Fourier transform (FFT) to implement pulse compression, the high resolution range profile (HRRP) will be broadened and distorted. To improve the quality of the HRRP, considering the fractional Fourier transform (FRFT) ...
A fringe analysis technique, which makes use of the spatial filtering property of the Fourier transform method, for the elimination of random impulsive noise in the wrapped phase maps obtained using the phase stepping technique, is presented. Phase noise is converted into intensity noise by transforming the wrapped ...
We investigate the ISAR imaging model using two different approaches the Fourier and the wavelet transform. Starting from the weak-scatter far-field model we explain why this approximation it's a Fourier Transform. We investigate the scattering mechanisms...
We present what we believe to be the first implementation of Fourier transform (FT) holography using a tabletop coherent x-ray source. By applying curvature correction to compensate for the large angles inherent in high-NA coherent imaging, we achieve image resolution of 89 nm using high-harmonic beams at a wavelength of 29 nm. ...
A general purpose block-to-block affine transformation estimator is described. The estimator is based on Fourier slice analysis and Fourier spectral alignment. It shows encouraging performance in terms of both speed and accuracy compared to existing methods. The key elements of its success are attributed to the ability to: 1) locate an arbitrary number of ...
This paper presents a new approach to non-rigid registration. A hierarchical subdivision approach is applied, with local normalized phase correlation for patch registration. The major improvement is achieved by implementing a suitable decimation at each level. The decimation is implemented via a Gram polynomial basis. Both global and local polynomial approximation are ...
One consequence of the self-amplified stimulated emission process used to generate x rays in free electron lasers (FELs) is the intrinsic shot-to-shot variance in the wavelength and temporal coherence. In order to optimize the results from diffractive imaging experiments at FEL sources, it will be advantageous to acquire a means of collecting coherence and spectral information ...
We explore the polarization dependence of the nonlinear response of a planar nematic liquid crystal cell doped with 1% wt of methyl red dye. The results obtained show that the refractive index change can be switched from a positive value to a negative one as the polarization of the beam changes from parallel to perpendicular with respect to the rubbing direction. This property is exploited in a ...
The technique of maximizing sharpness metrics has been used to estimate and compensate for aberrations with adaptive optics, to correct phase errors in synthetic-aperture radar, and to restore images. The largest class of sharpness metrics is the sum over a nonlinear point transformation of the image intensity. How the second ...
A Windows based application system for data collection, Fourier reconstruction and analysis of pure phase encoded constant-time radio frequency electron paramagnetic resonance (EPR) images, is described. The graphical user interface (GUI) of the system was written in MATLAB version 5.0, using its built-in GUI utilities. Design ...
People can recognize the meaning or gist of a scene from a single glance, and a few recent studies have begun to examine the sorts of information that contribute to scene gist recognition. The authors of the present study used visual masking coupled with image manipulations (randomizing phase while maintaining the Fourier amplitude ...
An optical joint transform correlation-based cryptographic system is a used to feed multiple phase-shifted encryption keys into four parallel channels along with a to-be-encrypted signal in the form of an image. The resulting joint power spectra (JPS) signals are phase-shifted and then combined to yield a modified JPS signal. Inverse ...
This paper presents an absolute phase calculation method from one composite RGB fringe pattern image by using the windowed Fourier transform (WFT) algorithm and the optimum three-frequency selection method. Three fringe patterns having the optimum fringe numbers are coded into the red, green and blue channels of a composite color ...
A subaperture autofocus algorithm for synthetic aperture radar (SAR) partitions range-compressed phase-history data collected over a full aperture into equal-width subapertures. Application of a one-dimensional Fourier transform to each range bin converts each subaperture data set into a full-scene image (map). Any linear ...
An approach to near-field beam shaping using a pixellated binary phase plate is presented. Continuous spatial-intensity modulation without phase modulation is obtained in an image plane of the phase plate after far-field Fourier filtering. The phase plate is a substrate ...
Phase sensitive x-ray imaging extends standard x-ray microscopy techniques by offering up to a thousand times higher sensitivity than absorption-based techniques. If an object is illuminated with a sufficiently coherent beam, phase contrast is achieved by moving the detector downstream from the object. There is a quantitative ...
We demonstrate edge-enhanced imaging produced by volume phase gratings recorded on a polyvinyl alcohol/acrylamide photopolymer. Bragg diffraction, exhibited by volume gratings, modifies the impulse response of the imaging system, facilitating spatial filtering operations with no need for a physical Fourier plane. ...
A method of reconstructing positive and negative images from Fourier holograms recorded without the dc components is demonstrated by use of a coaxial holographic storage system. Reconstructed images are obtained by adding a phase-modulated dc component of the signal beam on reading. Contrast reversal of the ...
The Geosynchronous Imaging Fourier Transform Spectrometer (GIFTS) is the first hyper-spectral remote
... BY CONVERTING A FRESNEL TRANSFORM MICROWAVE HOLOGRAM INTO ... TECHNIQUE OF NUMERICAL IMAGE RECONSTRUCTION FROM ...
