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Band-Limited Angular Spectrum Method for Numerical Simulation of Free-Space Propagation in Far and Near Fields

OPTICS EXPRESS 2009年第22期17卷 19662-19673页

作者： Matsushima, Kyoji Shimobaba, Tomoyoshi Kansai Univ Dept Elect & Elect Engn Osaka 5648680 Japan Chiba Univ Grad Sch Engn Inage Ku Chiba 2638522 Japan

A novel method is proposed for simulating free-space propagation. This method is an improvement of the angular spectrum method (AS). The AS does not include any approximation of the propagation distance, because the formula thereof is derived directly from the Rayleigh-Sommerfeld equation. However, the AS is not an all-round method, because it produces severe numerical errors due to a sampling problem of the transfer function even in Fresnel regions. The proposed method resolves this problem by limiting the bandwidth of the propagation field and also expands the region in which exact fields can be calculated by the AS. A discussion on the validity of limiting the bandwidth is also presented. (C) 2009 Optical Society of America

关键词： computation methods Diffraction theory Digital holographic imaging Discrete Fourier transforms Numerical simulation Propagation methods

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Computer-generated holograms for three-dimensional surface objects with shade and texture

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APPLIED OPTICS 2005年第22期44卷 4607-4614页

作者： Matsushima, K Kansai Univ Dept Elect Engn & Comp Sci Suita Osaka 5648680 Japan

Digitally synthetic holograms of surface model objects are investigated for reconstructing three-dimensional objects with shade and texture. The objects in the proposed techniques are composed of planar surfaces, and a property function defined for each surface provides shape and texture. The field emitted from each surface is independently calculated by a method based on rotational transformation of the property function by use of a fast Fourier transform (FFT) and totaled on the hologram. This technique has led to a reduction in computational cost: FFT operation is required only once for calculating a surface. In addition, another technique based on a theoretical model of the brightness of the reconstructed surfaces enables us to shade the surface of a reconstructed object as designed. Optical reconstructions of holograms synthesized by the proposed techniques are demonstrated. (c) 2005 Optical Society of America.

关键词： computation methods Fast Fourier transforms Optical surfaces Spatial resolution Three dimensional imaging Wave optics

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Decision feedback equalizer for holographic data storage

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APPLIED OPTICS 2018年第15期57卷 4056-4066页

作者： Kim, Kyuhwan Kim, Seung Hun Koo, Gyogwon Seo, Min Seok Kim, Sang Woo Pohang Univ Sci & Technol Dept Elect Engn 77 Cheongam Ro Pohang South Korea

Holographic data storage (HDS) has attracted much attention as a next-generation storage medium. Because HDS suffers from two-dimensional (2D) inter-symbol interference (IST), the partial-response maximum likelihood (PRML) method has been studied to reduce 2D IST. However, the PRML method has various drawbacks. To solve the problems, we propose a modified decision feedback equalizer (DFE) for HDS. To prevent the error propagation problem, which is a typical problem in DFEs, we also propose a reliability factor for HDS. Various simulations were executed to analyze the performance of the proposed methods. The proposed methods showed fast processing speed after training, superior bit error rate performance, and consistency. (C) 2018 Optical Society of America

关键词： computation methods Holographic memory Holographic techniques Laser beams Phase modulation Spatial light modulators

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

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OPTICS EXPRESS 2014年第25期22卷 31426-31433页

作者： Takasaki, Kevin T. Fleischer, Jason W. Princeton Univ Dept Elect Engn Princeton NJ 08544 USA

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. (C) 2014 Optical Society of America

关键词： computation methods Image quality Light scattering Optical memory Phase conjugation Scattering media

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Dynamic non-line-of-sight imaging system based on the optimization of point spread functions

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OPTICS EXPRESS 2021年第20期29卷 32349-32364页

作者： Pei, Chengquan Zhang, Anke Deng, Yue Xu, Feihu Wu, Jiamin Li, David U-Lei Qiao, Hui Fang, Lu Dai, Qionghai Tsinghua Univ Dept Automat Beijing 100084 Peoples R China Tsinghua Univ Tsinghua Berkeley Shenzhen Inst Shenzhen 518000 Peoples R China Beihang Univ Sch Astronaut Beijing Peoples R China Univ Sci & Technol China Dept Modern Phys Hefei 230026 Peoples R China Univ Strathclyde Fac Engn Glasgow G4 0NW Lanark Scotland Tsinghua Univ Dept Elect Engn Beijing 100084 Peoples R China

Non-line-of-sight (NLOS) imaging reveals hidden objects reflected from diffusing surfaces or behind scattering media. NLOS reconstruction is usually achieved by computational deconvolution of time-resolved transient data from a scanning single-photon avalanche diode (SPAD) detection system. However, using such a system requires a lengthy acquisition, impossible for capturing dynamic NLOS scenes. We propose to use a novel SPAD array and an optimization-based computational method to achieve NLOS reconstruction of 20 frames per second (fps). The imaging system's high efficiency drastically reduces the acquisition time for each frame. The forward projection optimization method robustly reconstructs NLOS scenes from low SNR data collected by the SPAD array. Experiments were conducted over a wide range of dynamic scenes in comparison with confocal and phase-field methods. Under the same exposure time, the proposed algorithm shows superior performances among state-of-the-art methods. To better analyze and validate our system, we also used simulated scenes to validate the advantages through quantitative benchmarks such as PSNR, SSIM and total variation analysis. Our system is anticipated to have the potential to achieve video-rate NLOS imaging. (C) 2021 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

关键词： computation methods Detector arrays Imaging techniques Laser scanning Thermal imaging Three dimensional imaging

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Single-photon peak event detection (SPEED): a computational method for fast photon counting in fluorescence lifetime imaging microscopy

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OPTICS EXPRESS 2021年第23期29卷 37759-37775页

作者： Sorrells, Janet E. Iyer, Rishyashring R. Yang, Lingxiao Chaney, Eric J. Marjanovic, Marina Tu, Haohua Boppart, Stephen A. Univ Illinois Beckman Inst Adv Sci & Technol Urbana IL 61801 USA Univ Illinois Dept Bioengn Urbana IL 61801 USA Univ Illinois Dept Elect & Comp Engn Urbana IL 61801 USA Univ Illinois Carle Illinois Coll Med Urbana IL 61801 USA Canc Ctr Illinois Urbana IL 61801 USA

Fluorescence lifetime imaging microscopy (FLIM) characterizes samples by examining the temporal properties of fluorescence emission, providing useful contrast within samples based on the local physical and biochemical environment of fluorophores. Despite this, FLIM applications have been limited in scope by either poor accuracy or long acquisition times. Here, we present a method for computational single-photon counting of directly sampled time-domain FLIM data that is capable of accurate fluorescence lifetime and intensity measurements while acquiring over 160 Mega-counts-per-second with sub-nanosecond time resolution between consecutive photon counts. We demonstrate that our novel method of Single-photon PEak Event Detection (SPEED) is more accurate than direct pulse sampling and faster than established photon counting FLIM methods. We further show that SPEED can be implemented for imaging and quantifying samples that benefit from higher -throughput and -dynamic range imaging with real-time GPU-accelerated processing and use this capability to examine the NAD(P)H-related metabolic dynamics of apoptosis in human breast cancer cells. computational methods for photon counting such as SPEED open up more opportunities for fast and accurate FLIM imaging and additionally provide a basis for future innovation into alternative FLIM techniques. (C) 2021 Optical Society of America under the terms of the OSA Open Access Publishing Agreement.

关键词： computation methods Optical imaging Photon counting Range imaging Single photon detectors Temporal resolution

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Variational estimation of inhomogeneous specular reflectance and illumination from a single view

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JOURNAL OF THE OPTICAL SOCIETY OF AMERICA A-OPTICS IMAGE SCIENCE AND VISION 2011年第2期28卷 136-146页

作者： Hara, Kenji Nishino, Ko Kyushu Univ Fac Design Dept Visual Commun Design Minami Ku Fukuoka 8158540 Japan Drexel Univ Coll Engn Dept Comp Sci Philadelphia PA 19104 USA

Estimating the illumination and the reflectance properties of an object surface from a few images is an important but challenging problem. The problem becomes even more challenging if we wish to deal with real-world objects that naturally have spatially inhomogeneous reflectance. In this paper, we derive a novel method for estimating the spatially varying specular reflectance properties of a surface of known geometry as well as the illumination distribution of a scene from a specular-only image, for instance, recovered from two images captured with a polarizer to separate reflection components. Unlike previous work, we do not assume the illumination to be a single point light source. We model specular reflection with a spherical statistical distribution and encode its spatial variation with a radial basis function (RBF) network of their parameter values, which allows us to formulate the simultaneous estimation of spatially varying specular reflectance and illumination as a constrained optimization based on the I-divergence measure. To solve it, we derive a variational algorithm based on the expectation maximization principle. At the same time, we estimate optimal encoding of the specular reflectance properties by learning the number, centers, and widths of the RBF hidden units. We demonstrate the effectiveness of the method on images of synthetic and real-world objects. (C) 2011 Optical Society of America

关键词： computation methods Inverse problems Laser ranging Light sources Polarizers Spatial resolution

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Fast method for calculating a curved hologram in a holographic display

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OPTICS EXPRESS 2020年第8期28卷 11290-11300页

作者： Kang, Ruidan Liu, Juan Pi, Dapu Duan, Xinhui Beijing Inst Lechnol Sch Opt & Photon Beijing Engn Res Ctr Mixed Real & Adv Display Beijing 100081 Peoples R China

A curved hologram can increase the view angle in a holographic display. The huge data processing and curved computer-generated hologram (CCGH) computation time is still a challenge for real-time display. Here, we propose two fast methods to accelerate the computation. The first one is a diffraction compensation (DC) method where the diffraction calculation is from the wave-front recording plane (WRP) to a CCGH. The other is an approximate compensation (AC) method that adds a phase difference distribution to the WRP to obtain the CCGH. Numerical simulations and optical experiments are performed, which demonstrate that the two methods are feasible and the computation time is dramatically reduced. The AC method can further reduce time significantly compared with the DC method. And the image quality for proposed methods is similar. It is expected that these fast methods can be combined with curved display screen and flexible display materials in the future. (C) 2020 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

关键词： computation methods Holographic displays Holographic recording Image quality Numerical simulation Phase modulation

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Three-dimensional polarimetric computational integral imaging

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OPTICS EXPRESS 2012年第14期20卷 15481-15488页

作者： Xiao, Xiao Javidi, Bahram Saavedra, Genaro Eismann, Michael Martinez-Corral, Manuel Univ Connecticut Dept Elect & Comp Engn Storrs CT 06269 USA Univ Valencia Dept Opt E-46100 Burjassot Spain USAF Sensors Directorate Res Lab Wright Patterson AFB OH 45433 USA

In this paper, we propose a novel 3D polarimetric computational integral imaging system by using polarization diversity of objects under natural illumination conditions. In the system, the measured Stokes polarization parameters are utilized to generate degree of polarization images of a 3D scene. Based on degree of polarization images and original 2D images, we utilize a modified computational reconstruction method to perform 3D polarimetric image reconstruction. The system may be used to detect or classify objects with distinct polarization signatures in 3D space. Experimental results also show the proposed system may mitigate the effect of occlusion in 3D reconstruction. (C) 2012 Optical Society of America

关键词： Circular polarization computation methods Image reconstruction Polarimetric imaging Surface measurements Three dimensional imaging

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Full-automatic self-calibration of color digital cameras using color targets

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OPTICS EXPRESS 2011年第19期19卷 18164-18174页

作者： Yilmazturk, F. Aksaray Univ Aksaray Turkey

In photogrammetric applications, camera calibration and orientation procedures are a prerequisite for the extraction of precise and reliable 3D metric information from images. This study presents a method for full automatic calibration of color digital cameras using color targets. Software developed using Borland C + + Builder programming language is used to apply the method. With this software, the calibration process is carried out in 3 stages: firstly, at least four of six color targets (whose 3D object coordinates are known) on each image of the overall test field are detected and the approximate exterior orientation parameters are computed. Then, the remaining target points are measured using the approximate image locations, determined using these parameters and the 3D object point coordinates parameters. Finally, calibration parameters are determined using a self-calibration bundle adjustment technique. The colored targets within the test field are assigned labels corresponding to their color. For the detection of color targets and computation of approximate exterior orientation elements, HSV color space was used together with space resection computation method for all the possible color labels of targets. To test the proposed method, full automatic calibration was carried out using six different digital cameras. The calibration accuracies achieved in object space were within the range 0.006 to 0.030 mm;the accuracies achieved in image space were within the range 0.14 to 0.51 mu m. (C) 2011 Optical Society of America

关键词： Camera calibration CCD cameras Color detection Color spaces computation methods Image processing

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