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Optimized pupil-plane phase masks for high-contrast imaging

APPLIED OPTICS 2018年第20期57卷 5688-5693页

作者： Wirth, Jacob H. Watnik, Abbie T. Swartzlander, Grover A. Rochester Inst Technol 54 Lomb Mem Dr Rochester NY 14623 USA US Naval Res Lab 4555 Overlook Ave SW Washington DC 20375 USA

A differential evolution algorithm (DEA) is shown to improve the design of phase-only pupil plane masks for imaging in the presence of a high-intensity point source. Strehl and suppression ratio metrics for various phase basis functions were experimentally and numerically calculated. Experiments performed with a spatial light modulator demonstrated 100 times suppression of the peak intensity. The Strehl ratio was found to be higher for the DEA masks compared to the individual phase basis function. (C) 2018 Optical Society of America

关键词： computation methods Image metrics Image quality Imaging systems Spatial frequency Wavefront encoding

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DECONVOLUTION AND PHASE RETRIEVAL WITH USE OF ZERO SHEETS

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JOURNAL OF THE OPTICAL SOCIETY OF AMERICA A-OPTICS IMAGE SCIENCE AND VISION 1995年第9期12卷 1842-1857页

作者： BONES, PJ PARKER, CR SATHERLEY, BL WATSON, RW []Department of Electrical and Electronic Engineering University of Canterbury Christchurch New Zealand

Recent developments in the application of zeros (of the analytically continued spectrum of a compact two-dimensional image) in solving deconvolution and phase retrieval problems are reviewed. New algorithms for use in the presence of noise are described and demonstrated. These include algorithms for deconvolution where the point-spread function is approximately known, for ensemble blind deconvolution (such as is required for ensembles of astronomical speckle images), and for phase retrieval (itself a special case of blind deconvolution). Many of the ideas embodied in the algorithms were foreshadowed by Bates et al. [J. Opt. Sec. Am. A 7, 468 (1990)]. Simulated images are employed in the examples shown, except for phase retrieval, where successful recovery of the phase error in the aperture of a radio telescope is demonstrated.

关键词： Blind deconvolution computation methods Fast Fourier transforms Image quality Phase measurement Phase retrieval

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Composite method for precise freeform optical beam shaping

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APPLIED OPTICS 2015年第31期54卷 9364-9369页

作者： Feng, Zexin Froese, Brittany D. Liang, Rongguang Univ Arizona Coll Opt Sci Tucson AZ 85721 USA Tsinghua Univ Dept Precis Instrument Beijing 100084 Peoples R China Univ Hts New Jersey Inst Technol Dept Math Sci Newark NJ 07102 USA

We present a composite freeform surface construction method for creating a high-accuracy irradiance distribution from a given incident beam under the influence of diffraction. The main idea is that we first determine a fully continuous freeform surface estimate by solving a standard Monge-Ampere equation and then refine it using an iterative Fourier-transform algorithm associated with over-compensation. Although this method can only be implemented in the paraxial approximation, it can significantly simplify the design and is applicable to many examples that fulfill this restriction. The resulting optical surface, unwrapped from the final phase, is an unusual discontinuous freeform surface that can produce very promising performances in terms of surface roughness and irradiance accuracy. (C) 2015 Optical Society of America

关键词： Diffractive optics Geometric optical design computation methods Nonimaging optics Inverse problems Phase retrieval

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Euclidean color-difference formula for small-medium color differences in log-compressed OSA-UCS space

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JOURNAL OF THE OPTICAL SOCIETY OF AMERICA A-OPTICS IMAGE SCIENCE AND VISION 2009年第1期26卷 121-134页

作者： Oleari, Claudio Melgosa, Manuel Huertas, Rafael Univ Parma Dipartimento Fis I-43100 Parma Italy Univ Granada Fac Ciencias Dept Opt E-18071 Granada Spain

This work continues previous research by the same authors [J. Opt. Sec. Am. A 23, 2077 (2006)], where empirical small-medium color differences were: represented by an ellipsoidal equation Delta E(GP) in the Uniform Color System of the Optical Society of America. Now logarithmic compressions on chroma and lightness are introduced to produce a new space with Euclidean color-difference formulas Delta E(E). The CIEDE2000, Delta E(GP), and Delta E(E) formulas are found statistically equivalent in the prediction of many available empirical datasets. However, Delta E(E) is the simplest formula providing relationships with visual processing. These analyses hold true for CIE 1964 Supplementary Standard Observer and D65 illuminant. (C) 2008 Optical Society of America

关键词： CIE color spaces Color Color difference Color spaces computation methods Standard observers

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Photorealistic ray tracing to visualize automobile side mirror reflective scenes

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OPTICS EXPRESS 2014年第21期22卷 25729-25738页

作者： Lee, Hocheol Kim, Kyuman Lee, Gang Lee, Sungkoo Kim, Jingu Hanbat Natl Univ Dept Mech Engn Taejon 305719 South Korea Bullsone Co Ltd R&D Inst Inchon 406840 South Korea

We describe an interactive visualization procedure for determining the optimal surface of a special automobile side mirror, thereby removing the blind spot, without the need for feedback from the error-prone manufacturing process. If the horizontally progressive curvature distributions are set to the semi-mathematical expression for a free-form surface, the surface point set can then be derived through numerical integration. This is then converted to a NURBS surface while retaining the surface curvature. Then, reflective scenes from the driving environment can be virtually realized using photorealistic ray tracing, in order to evaluate how these reflected images would appear to drivers. (C) 2014 Optical Society of America

关键词： computation methods Freeform surfaces Image metrics Image processing Optical aberrations Ray tracing

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Operational remote sensing of aerosols over land to account for directional effects

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APPLIED OPTICS 2001年第18期40卷 3060-3075页

作者： Ramon, D Santer, R Univ Littoral Cote dOpale Lab Interdisciplinaire Sci Environm F-62930 Wimereux France

The assumption that the ground is a Lambertian reflector is commonly adopted in operational atmospheric corrections of spaceborne sensors. Through a simple modeling of directional effects in radiative transfer following the second simulation of the satellite signal in the solar spectrum (6S) approach, we propose an operational method to account for the departure from Lambertian behavior of a reflector covered by a scattering medium. This method relies on the computation of coupling terms between the reflecting and the scattering media and is able to deal with a two-layer atmosphere. We focus on the difficult problem of aerosol. remote sensing over land. One popular sensing method relies on observations over dense dark vegetation, for which the surface reflectance is low and quite well defined in the blue and in the red. Therefore a study was made for three cases: (1) dark vegetation covered by atmospheric aerosols, (2) atmospheric aerosols covered by molecules, and finally (3) dark vegetation covered by atmospheric aerosols covered by molecules. Comparisons of top-of-the-atmosphere reflectances computed with our modeling and reference computations made with the successive-order-of-scattering code show the robustness of the modeling in the blue and in the red for aerosol optical thicknesses as great as 0.6 and solar zenith angles as large as 60 degrees. The model begins to fail only in the blue for large solar zenith angles. The benefits expected for aerosol remote sensing over land are evaluated with an aerosol retrieval scheme developed for the Medium-Resolution Imaging Spectrometer. The main result is a better constraint on the aerosol model with inclusion of directional effects and a weaker effect on the optical thickness of the retrieved aerosol. The directional scheme is then applied to the aerosol remote-sensing problem in actual Indian Remote Sensing Satellite P3/Modular Optoelectronic Scanner images over land and shows significant improvement compared with a

关键词： Aerosol effects Atmospheric correction Atmospheric transmittance computation methods Remote sensing Scattering media

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Design of TIR optics generating the prescribed irradiance distribution in the circle region

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JOURNAL OF THE OPTICAL SOCIETY OF AMERICA A-OPTICS IMAGE SCIENCE AND VISION 2012年第9期29卷 1758-1763页

作者： Moiseev, Mikhail A. Doskolovich, Leonid L. Russian Acad Sci Image Proc Syst Inst Samara 443001 Russia Samara State Aerosp Univ Samara 443086 Russia LED Opt Design LLC Samara 443001 Russia

We present the method for computation of highly effective total internal reflection (TIR) optics for LED-based illumination systems. The computation problem is reduced to the integration of several explicit independent first-order differential equations. Two designs of TIR optics are considered and compared: with flat and with aspherical upper surface. The dependence of nonuniformity of generated irradiance distribution on the size of the light source is studied for both designs numerically. It is shown that point source approximation is acceptable in cases when the size of the light source is 5 (or more) times less than the distance to the inner surface of the optical element. (C) 2012 Optical Society of America

关键词： computation methods Illumination design Light sources Optical elements Optical surfaces Total internal reflection

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Illuminant direction estimation for a single image based on local region complexity analysis and average gray value

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APPLIED OPTICS 2014年第2期53卷 226-236页

作者： Yi, Jizheng Mao, Xia Chen, Lijiang Xue, Yuli Compare, Angelo Beihang Univ Sch Elect & Informat Engn Beijing 100191 Peoples R China Univ Bergamo Dept Human Sci I-24129 Bergamo Italy

Illuminant direction estimation is an important research issue in the field of image processing. Due to low cost for getting texture information from a single image, it is worthwhile to estimate illuminant direction by employing scenario texture information. This paper proposes a novel computation method to estimate illuminant direction on both color outdoor images and the extended Yale face database B. In our paper, the luminance component is separated from the resized YCbCr image and its edges are detected with the Canny edge detector. Then, we divide the binary edge image into 16 local regions and calculate the edge level percentage in each of them. Afterward, we use the edge level percentage to analyze the complexity of each local region included in the luminance component. Finally, according to the error function between the measured intensity and the calculated intensity, and the constraint function for an infinite light source model, we calculate the illuminant directions of the luminance component's three local regions, which meet the requirements of lower complexity and larger average gray value, and synthesize them as the final illuminant direction. Unlike previous works, the proposed method requires neither all of the information of the image nor the texture that is included in the training set. Experimental results show that the proposed method works better at the correct rate and execution time than the existing ones. (C) 2014 Optical Society of America

关键词： computation methods Edge detection Image processing Image recognition algorithms Light properties Light sources

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Light field image super-resolution based on raw data with transformers

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JOURNAL OF THE OPTICAL SOCIETY OF AMERICA A-OPTICS IMAGE SCIENCE AND VISION 2022年第12期39卷 2131-2141页

作者： Guo, Xiao Sang, Xinzhu Yan, Binbin Chen, Duo Wang, Peng Beijing Univ Posts & Telecommun State Key Lab Informat Photon & Opt Commun Beijing 100876 Peoples R China

Light field (LF) image super-resolution (SR) can improve the limited spatial resolution of LF images by using com-plementary information from different perspectives. However, current LF image SR methods only use the RGB data to implicitly exploit the information among different perspectives, without paying attention to the informa-tion loss from raw data to RGB data and the explicit structure information utilization. To address the first issue, a data generation pipeline is developed to collect LF raw data for LF image SR. In addition, to make full use of the multiview information, an end-to-end convolutional neural network architecture (namely, LF-RawSR) is proposed for LF image SR. Specifically, an aggregated module is first used to fuse the angular information based on a volume transformer with plane sweep volume. Then the aggregated feature is warped to all LF views using a cross-view transformer for nonlocal dependencies utilization. The experimental results demonstrate that our method outper-forms existing state-of-the-art methods with a comparative computational cost, and fine details and clear structures can be restored.(c) 2022 Optica Publishing Group

关键词： computation methods Image processing Light fields Light intensity Neural networks Spatial resolution

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Efficient light-scattering calculations for aggregates of large spheres

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APPLIED OPTICS 2003年第15期42卷 2785-2793页

作者： Saija, R Iatì, MA Denti, P Borghese, F Giusto, A Sindoni, OI Univ Messina Dipartimento Fis Mat & Tecnol Fis Avanzate I-98166 Messina Italy Univ Messina Ist Nazl Fis Mat Unita Messina I-98166 Messina Italy Edgewood Chem Biol Ctr Gunpowder Branch Aberdeen Proving Ground MD 21010 USA

Calculation of the scattering pattern from aggregates of spheres through the T-matrix approach yields high-precision results but at a high-computational cost, especially when the aggregate concerned is large or is composed of large-size spheres. With reference to a specific but representative aggregate, we discuss how and to what extent the computational effort can be reduced but still preserve the qualitative features of the signature of the aggregate concerned. (C) 2003 Optical Society of America.

关键词： computation methods In field scattering Mie theory Optical properties Particle scattering Scattering

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