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Depth imaging denoising of photon-counting lidar

APPLIED OPTICS 2019年第16期58卷 4390-4394页

作者： Huang, Pengwei He, Weiji Gu, Guohua Chen, Qian Nanjing Univ Sci & Technol Nanjing 210094 Jiangsu Peoples R China

Photon-counting lidar systems have difficulty reconstructing target depth images due to ambient noise. In this paper, we propose a novel way of using correlative photons and spatial correlations to reduce the false alarm probability. Experimental results show that the root mean square error of the depth image reconstructed by the proposed algorithm can be 1.68 times and 1.11 times better than that of the fast depth imaging denoising algorithm and log-matched filter estimation. The experimental results show that the proposed algorithm can effectively improve the reconstructed image of photon-counting lidar. (c) 2019 Optical Society of America

关键词： Avalanche photodiodes Geiger modes image processing algorithms image reconstruction Photon correlations Photon counting

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Video-rate lensless endoscope with self-calibration using wavefront shaping

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OPTICS LETTERS 2020年第13期45卷 3629-3632页

作者： Scharf, Elias Dremel, Jakob Kuschmierz, Robert Czarske, Juergen Tech Univ Dresden Lab Measurement & Sensor Syst Tech Dresden Germany

Lensless fiber endoscopes are of great importance for keyhole imaging. Coherent fiber bundles (CFB) can be used in endoscopes as remote phased arrays to capture images. One challenge is to image at high speed while correcting aberrations induced by the CFB. We propose the combination of digital optical phase conjugation, using a spatial light modulator, with fast scanning, for which a 2D galvo scanner and an adaptive lens are employed. We achieve the transmission of laser and image scanning through the CFB. Video-rate imaging at 20 Hz in 2D with subcellular resolution is demonstrated in 3D with 1 Hz. The sub-millimeter-diameter scanning endoscope has a great potential in biomedicine, for manipulation, e.g., in optogenetics, as well as in imaging. (C) 2020 Optical Society of America

关键词： Fiber bundles image processing algorithms Laser scanning Phase conjugation Phased arrays Scanners

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Light field microscopy based on structured light illumination

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OPTICS LETTERS 2021年第14期46卷 3424-3427页

作者： Fu, Zhiqiang Geng, Qiang Chen, Jialong Chu, Li-An Chiang, Ann-Shyn Chen, Shih-Chi Chinese Univ Hong Kong Dept Mech & Automat Engn Shatin Hong Kong Peoples R China Natl Tsing Hua Univ Brain Res Ctr 101Sect 2Kuang Fu Rd Hsinchu 30013 Taiwan

In this Letter, we present the modeling, design, and characterization of a light sheet-based structured light illumination (SLI) light field microscopy (LFM) system for fast 3D imaging, where a digital micromirror device is employed to rapidly generate designed sinusoidal patterns in the imaging field. Specifically, we sequentially obtain uniformly illuminated and structured light field images, followed by post-processing with a new, to the best of our knowledge, algorithm that combines the deconvolution and HiLo algorithms. This enables fast volumetric imaging with improved optical cross-sectioning capability at a speed of 50 volumes per second over an imaging field of 250 x 250 x 80 mu m(3) in the x, y, and z axis, respectively. Mathematical models have been derived to explain the performance enhancement due to suppressed background noises. To verify the results, imaging experiments on fluorescence beads, fern spore, and Drosophila brain samples, have been performed. The results indicate that the light sheet-based SLI-LFM presents a fast 3D imaging solution with substantially improved optical cross-sectioning capability in comparison with a standard light sheet-based LFM. The new light field imaging method may find important applications in the field of biophotonics. (C) 2021 Optical Society of America.

关键词： Digital micromirror devices image processing algorithms Imaging techniques Light fields Plenoptic imaging Three dimensional imaging

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Shack-Hartmann sensor based on a cylindrical microlens array

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OPTICS LETTERS 2007年第7期32卷 769-771页

作者： Ares, M. Royo, S. Caum, J. Tech Univ Catalonia Ctr Sensor Instrumentat & Syst Dev Terrassa 08222 Spain

We present a Shack-Hartmann wavefront sensor (SHWS) based on a cylindrical microlens array as a device for measuring highly aberrated wavefronts. Instead of the typical spot pattern created by a conventional SHWS, two orthogonal line patterns are detected on a CCD and are superimposed. A processing algorithm uses the continuity of the focal line to extend the dynamic range of measurement by localizing the line, even if it leaves the CCD area confined by the corresponding microcylinder. The measurement of a wavefront from a progressive addition lens with an 80 lambda peak-to-valley value reveals the capabilities of the sensor. (c) 2007 Optical Society of America.

关键词： Calibration Charge coupled devices image processing algorithms Laser coupling Wavefront aberrations Wavefronts

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OPTICAL LOGARITHMIC TRANSFORMATION OF SPECKLE imageS WITH BACTERIORHODOPSIN FILMS

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OPTICS LETTERS 1995年第2期20卷 201-203页

作者： DOWNIE, JD NASA Ames Research Center M/S 269-3 Moffett Field California 94035

The application of logarithmic transformations to speckle images is sometimes desirable in converting the speckle noise distribution into an additive, constant-variance noise distribution. The optical transmission properties of some bacteriorhodopsin films are well suited to implement such a transformation optically in a parallel fashion. I present experimental results of the optical conversion of a speckle image into a transformed image with signal-independent noise statistics, using the real-time photochromic properties of bacteriorhodopsin. The original and transformed noise statistics are confirmed by histogram analysis.

关键词： Digital image processing image metrics image processing image processing algorithms Optically addressed spatial light modulators Speckle noise

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Imaging the electro-kinetic response of biological tissues with optical coherence tomography

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OPTICS LETTERS 2013年第14期38卷 2572-2574页

作者： Wawrzyn, K. Demidov, V. Vuong, B. Harduar, M. K. Sun, C. Yang, V. X. D. Doganay, O. Toronov, V. Xu, Y. Ryerson Univ Dept Phys Toronto ON Canada Ryerson Univ Dept Elect & Comp Engn Toronto ON Canada Univ Toronto Dept Med Toronto ON Canada Univ Toronto Div Neurosurg Toronto ON Canada

We demonstrate the feasibility of using optical coherence tomography (OCT) to detect and image an electro-kinetic response: electric-field induced optical changes (EIOC) in soft biological tissues. A low-frequency electric field was applied to ex vivo samples of porcine heart tissues, while OCT signals were acquired continuously. Experimental results show that the amplitude of the OCT signal change is proportional to the amplitude and inversely proportional to the frequency of the applied electric field. We show that the nonconductive component of the sample was eliminated in the normalized EIOC image. To the best our knowledge, this is the first time a two-dimensional image related to the electro-kinetic response of soft tissues is obtained with depth resolution. Since electro-kinetic properties can change during cancerogenesis, EIOC imaging can potentially be used for cancer detection. (C) 2013 Optical Society of America

关键词： Electric fields Fourier transforms image processing algorithms Light propagation Optical coherence tomography Tissue

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image ALGEBRA REPRESENTATION OF PARALLEL OPTICAL BINARY ARITHMETIC

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APPLIED OPTICS 1989年第6期28卷 1263-1278页

作者： HUANG, KS JENKINS, BK SAWCHUK, AA UNIV SO CALIF INST SIGNAL & IMAGE PROCDEPT ELECT ENGNLOS ANGELESCA 90089

A binary image algebra (BIA) that gives a mathematical description of parallel processing operations is described. Rigorous and concise BIA representations of parallel arithmetic and symbolic substitution operations are given. A sequence of programming steps for implementation of these operations on a parallel architecture is specified by the BIA representation. Examples of arithmetic operations implemented on a digital optical cellular image processor architecture are given.

关键词： Digital optical computing image processing image processing algorithms Optical computers Optical computing Parallel processing

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Improved texture reproduction assessment of camera-phone-based medical devices with a dead leaves target

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OSA CONTINUUM 2019年第6期2卷 1863-1879页

作者： Suresh, Nitin Pfefer, T. Joshua Su, Jiahao Chen, Yu Wang, Quanzeng US FDA Ctr Devices & Radiol Hlth 10903 New Hampshire Ave Silver Spring MD 20993 USA Univ Maryland Dept Elect & Comp Engn 2410 AV Williams Bldg College Pk MD 20742 USA Univ Maryland Fischell Dept Bioengn 4108 Clark Hall College Pk MD 20742 USA

Camera-phone-based medical devices (CPMDs) represent a major emerging platform for point-of-care diagnostic imaging of biological tissue. In order to evaluate degradation in texture reproduction due to visible light image processing performed by CPMDs, a method (MTFDL) involving the generation of a modulation transfer function (MTF) based on measurements of a 'dead leaves (DL)' target has been proposed. In this study, we have identified discrepancies in the quantification of noise based on gray patches of the DL target as compared to the textual region. To address this issue, we have proposed an approach (MTFDL-den) for accurate MTFDL calculation through the use of effectively denoised DL images. Furthermore, we demonstrate that our MTFDL-den approach provides superior robustness to simulated noise. These findings will help establish effective standardized test methods for realistic benchtop assessment of CPMD image quality. (C) 2019 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

关键词： Digital image processing image processing image processing algorithms image quality Medical image processing Visible light

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INSTANTANEOUS VELOCITY-FIELD MEASUREMENTS IN UNSTEADY GAS-FLOW BY SPECKLE VELOCIMETRY

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APPLIED OPTICS 1983年第4期22卷 535-540页

作者： MEYNART, R The author is with Universite Libre de Bruxelles Service des Milieux Continus 1050 Bruxelles Belgium.

An application of speckle photography techniques to unsteady gas flow measurements is presented. The instrumentation developed for the analysis of double-exposure photographs by digital signal processing is described. It is shown that 2-D velocity fields can be measured even when the flow is not perfectly 2-D. Accuracy and limitations of these techniques are discussed.

关键词： Digital image processing Fringe analysis image processing image processing algorithms Signal processing Speckle photography

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image DECONVOLUTION BY A LOGARITHMIC EXPONENTIAL NONLINEAR JOINT TRANSFORM PROCESS

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APPLIED OPTICS 1990年第5期29卷 685-690页

作者： JAVIDI, B RUIZ, C RUIZ, J The authors are with University of Connecticut Electrical & Systems Engineering Department Storrs Connecticut 06269-3157

We present a nonlinear joint transform processor that uses logarithmic and exponential nonlinearities at the Fourier plane to remove the amplitude distortion effects of a smearing function. The smeared image and the blur function are displayed side by side at the input plane of the system. The exact Fourier phase of the original image is restored in the joint power spectrum from the product of the Fourier transform of the smeared image with the complex conjugate of the Fourier transform of the smearing function. The Fourier amplitude of the original image is recovered by applying the logarithmic nonlinearity to both the joint power spectrum of the smeared image and the blur function, and the Fourier spectrum of the blur function. The amplitude distortion of the joint power spectrum is then removed by subtracting the log of the Fourier spectrum of the blur function from the log of the joint power spectrum. An exponential nonlinearity is then applied to the output of the logarithmic subtraction to implement an inverse logarithmic operation and to recover the Fourier amplitude. An inverse Fourier transform operation will yield the unsmeared image at the output plane of the processor. An analysis of the logarithmic/exponential nonlinear signal processor for image deconvolution is presented. Computer simulation is presented to investigate the performance of the nonlinear processor for a linearly smeared image.

关键词： Fourier transforms image deconvolution image processing algorithms image restoration Power spectra Spatial filtering

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