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On-orbit calibration approach for optical navigation camera in deep space exploration

OPTICS EXPRESS 2016年第5期24卷 5536-5554页

作者： Wang, Mi Cheng, Yufeng Yang, Bo Jin, Shuying Su, Hongbo Wuhan Univ State Key Lab Informat Engn Surveying Mapping & R Wuhan 430079 Peoples R China Wuhan Univ Collaborat Innovat Ctr Geospatial Technol Wuhan 430079 Peoples R China Florida Atlantic Univ Dept Civil Environm & Geomat Engn Boca Raton FL 33431 USA

A spacecraft-borne optical navigation camera is one of the key instruments for optical autonomous navigation, and the line of sight (LOS) of the camera directly affects the accuracy of navigation. We developed an on-orbit calibration approach for a navigation camera to ensure the accuracy, in which a stepwise calibration is performed, external parameters estimated, and internal parameters estimated in a generalized camera frame determined by external parameters. In addition, we proposed a batch and sequential on-orbit estimation method to save on-orbit computing power, and established a strategy to reject misidentified reference stars while keeping consistency in on-orbit parameters estimation. After the calibration, the accuracy of LOS in inertial frame satisfied the need in optical autonomous navigation. The results have been proven precise and robust in three experiments. (C) 2016 Optical Society of America

关键词： Antennas Calibration Camera calibration image processing image processing algorithms Sensors

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MIDDLE INFRARED MULTISPECTRAL AIRCRAFT SCANNER DATA - ANALYSIS FOR GEOLOGICAL APPLICATIONS

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APPLIED OPTICS 1980年第14期19卷 2279-2290页

作者： KAHLE, AB MADURA, DP SOHA, JM The authors are with Jet Propulsion Laboratory California Institute of Technology Pasadena California 91103

Multispectral middle IR (8–13- μ m) data were acquired with an aircraft scanner over Utah. Because these digital image data were dominated by temperature, all six channels were highly correlated. Extensive processing was required to allow geologic photointerpretation based on subtle variations in spectral emittance between rock types. After preliminary processing, ratio images were produced and color ratio composites created from these. Sensor calibration and an atmospheric model allowed determination of surface brightness, temperature, emittance, and color composite emittance images. The best separation of major rock types was achieved with a principal component transformation, followed by a Gaussian stretch, followed by an inverse transformation to the original axes.

关键词： Color difference Color spaces Digital imaging image processing image processing algorithms Multispectral imaging

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Comparison of linear and nonlinear deconvolution algorithms for co-optimization of depth-of-field enhancing binary phase masks

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OSA CONTINUUM 2021年第2期4卷 589-601页

作者： Leveque, Olivier Kulcsar, Caroline Goudail, Francois Univ Paris Saclay Inst Opt Grad Sch CNRS Lab Charles Fabry F-91127 Palaiseau France

The depth-of-field of imaging systems can be enhanced by placing a phase mask in their aperture stop and deconvolving the image. In general, the mask is optimized using a closed-form image quality criterion assuming deconvolution with a Wiener filter. However, nonlinear deconvolution algorithms may have better performance, and the question remains as to whether a better co-designed system could be obtained from optimization with a criterion based on such algorithms. To investigate this issue, we compare optimization of phase masks with criteria based on the Wiener filter and on a nonlinear algorithm regularized by total variation. We show that the obtained optimal masks are identical, and propose a conjecture to explain this fact. This result is important since it supports the frequent co-design practice consisting of optimizing a system with a closed-form criterion based on linear deconvolution and deconvolving with a nonlinear algorithm. (c) 2021 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

关键词： image deconvolution image processing algorithms image quality image reconstruction Imaging systems Power spectral density

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NEW SPACE DOMAIN processing TECHNIQUE FOR PULSED LASER VELOCIMETRY

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APPLIED OPTICS 1990年第23期29卷 3399-3417页

作者： WERNET, MP EDWARDS, RV CASE WESTERN RESERVE UNIV DEPT CHEM ENGNCLEVELANDOH 44106

Current pulsed laser velocimetry data processing techniques offer high precision (1%) velocity estimates, but can require several hours of processing time on specialized array processors. Under some circumstances, a simple, fast, less accurate (~5%), data reduction technique, which also gives unambiguous velocity vector information is acceptable. In this work, we examine a direct space domain processing technique. The direct space domain processing technique was found to be far superior to any other techniques known, in achieving the objectives listed above. It employs a new data coding and reduction technique, where the particle time history information is used directly. Further, it has no 180° directional ambiguity. A complex convection vortex flow was recorded and completely processed in under 2 min on an 80386 based PC, producing a 2-D map of the flow field containing over 300 velocity vectors.

关键词： Far field diffraction Fringe analysis image processing algorithms Laser speckle Laser velocimetry Pulsed operation

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Imaging through fog using quadrature lock-in discrimination

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OSA CONTINUUM 2021年第5期4卷 1649-1657页

作者： Kumar, Shashank Debnath, Bapan Meena, M. S. Fade, Julien Dhar, Sankar Alouini, Mehdi Bretenaker, Fabien Ramachandran, Hema Rantan Res Inst Bangalore 560080 Karnataka India Indian Space Res Org Space Applicat Ctr Ahmadabad Gujarat India Univ Rennes CNRS Inst FOTON UMR 6082 F-35000 Rennes France Shiv Nadar Univ Gautam Buddha Nagar 201314 Uttar Pradesh India Univ Paris Saclay CNRS ENS Paris Saclay Cent SupelecLuMIn F-91190 Gif Sur Yvette France

We report experiments conducted in the field in the presence of fog, that were aimed at imaging under poor visibility. By means of intensity modulation at the source and two-dimensional quadrature lock-in detection by software at the receiver, a significant enhancement of the contrast-to-noise ratio was achieved in the imaging of beacons over hectometric distances. Further by illuminating the field of view with a modulated source, the technique helped reveal objects that were earlier obscured due to multiple scattering of light. This method, thus, holds promise of aiding in various forms of navigation under poor visibility due to fog. (C) 2021 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

关键词： Fast Fourier transforms image processing image processing algorithms image quality LED sources Multiple scattering

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Partially light-controlled imaging system based on High Temperature Poly-Silicon Thin Film Transistor-Liquid Crystal Display

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OPTICS EXPRESS 2010年第10期18卷 10616-10626页

作者： Tang, Yuanhe Zhang, Ruixia Gao, Haiyang Liu, Kai Zhao, Gaoxiang Yang, Xusan Li, Qing Liang, Yuan Ye, Na Liu, Hanchen Liu, Shulin Xian Univ Technol Sch Sci Xian 710048 Peoples R China Xian Polytech Univ Sch Sci Xian 710048 Peoples R China N Night Vis Technol Co LTD Xian Branch Xian 710065 Peoples R China

A partially light-controlled imaging system is proposed as a novel device. It is used to improve the imaging quality at the illumination of 1.979 x 10(5)lx by means of mitigating image contrast. It consists of a High Temperature Poly-Silicon Thin Film Transistor-Liquid Crystal Display (HTPS TFT-LCD), which is set between the lens and CCD and is coupled with CCD by the optical fiber taper. The transmittance of pixelated LCD can be controlled by Field-Programmable Gate Array to realize the partially light-controlled and thus dynamic range of the imaging system can be extended. Samples of indoor objects and outdoor license plate are photographed by the prototype imaging system under strong light. The imaging results of this novel system are satisfactory with better restored details, compared with the photos taken by normal CCD camera (WAT-231S2) which uses aperture and shutter to control the overall light intensity. (C) 2010 Optical Society of America

关键词： image processing image processing algorithms Light intensity Liquid crystal devices Nematic liquid crystals Thin films

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Automatic detection method for BGA defects based on x-ray imaging

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APPLIED OPTICS 2022年第21期61卷 6356-6365页

作者： Xiao, Kai Li, Qin Chen, Yang Natl Univ Def Technol Coll Comp Sci & Technol State Key Lab High Performance Comp Changsha 410073 Peoples R China Natl Key Lab Sci & Technol Blind Signal Proc Chengdu 610000 Peoples R China

Ball grid array (BGA) packaging is a high-density surface mount technology with the advantages of small size, good heat dissipation, and electrical properties, and is widely applied in the production of large-scale integrated circuits. With the rapid development of IC integration, devices assembled using BGA technology generally have greater complexity. However, BGA defects can seriously affect device performance and bring difficulties to product quality inspection. More importantly, in the process of BGA defect inspection, the high complexity of the device brings unprecedented challenges to the precise location of defects, which means that corresponding inspection methods should be improved. To this end, this paper proposes an automatic detection method for BGA defects based on x-ray imaging. First, x-ray imaging technology is utilized to achieve non-destructive detection of the BGA area inside the device and generate image data. On this basis, a set of algorithms including threshold separation, detection filling, and closing operation is designed to complete automatic detection of BGA defects. Furthermore, to objectively evaluate the effectiveness and performance of the proposed method, we conduct a series of comparative experiments using simulated and real data, and generate visual outputs. Through these experiments and analyses, we confirm that the proposed method plays an active and effective role and has robust performance in BCA defect detection. In particular, our method shows the expected performance in precisely finding BGA edge defects and subtle defects. (C) 2022 Optica Publishing Group

关键词： Attenuation coefficient Computed tomography Edge detection image processing image processing algorithms X ray imaging

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Foucault test: a quantitative evaluation method

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JOURNAL OF THE OPTICAL SOCIETY OF AMERICA A-OPTICS image SCIENCE AND VISION 2016年第8期33卷 1604-1611页

作者： Rodriguez, Gustavo Villa, Jesus Ivanov, Rumen Gonzalez, Efren Martinez, Geminiano Univ Autonoma Zacatecas Unidad Acad Ingn Elect Av Ramon Lopez Velarde 801 Zacatecas 98000 Mexico Univ Autonoma Zacatecas Unidad Acad Fis Calz SolidaridadEsquina Paseo Bufa S-N Zacatecas 98060 Mexico Ctr Invest Opt AC Loma Bosque 115Col Lomas Campestre Guanajuato 37150 Mexico

Reliable and accurate testing methods are essential to guiding the polishing process during the figuring of optical telescope mirrors. With the natural advancement of technology, the procedures and instruments used to carry out this delicate task have consistently increased in sensitivity, but also in complexity and cost. Fortunately, throughout history, the Foucault knife-edge test has shown the potential to measure transverse aberrations in the order of the wavelength, mainly when described in terms of physical theory, which allows a quantitative interpretation of its characteristic shadowmaps. Our previous publication on this topic derived a closed mathematical formulation that directly relates the knife-edge position with the observed irradiance pattern. The present work addresses the quite unexplored problem of the wavefront's gradient estimation from experimental captures of the test, which is achieved by means of an optimization algorithm featuring a proposed ad hoc cost function. The partial derivatives thereby calculated are then integrated by means of a Fourier-based algorithm to retrieve the mirror's actual surface profile. To date and to the best of our knowledge, this is the very first time that a complete mathematical-grounded treatment of this optical phenomenon is presented, complemented by an image-processing algorithm which allows a quantitative calculation of the corresponding slope at any given point of the mirror's surface, so that it becomes possible to accurately estimate the aberrations present in the analyzed concave device just through its associated foucaultgrams. (C) 2016 Optical Society of America

关键词： Digital image processing image processing algorithms Irradiance Optical surfaces Optical telescopes Optical testing

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Exposure-fusion-based dot-grid image acquisition and recognition for sheet metal strain analysis

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APPLIED OPTICS 2017年第35期56卷 9706-9715页

作者： Shi, Bao-Quan Zhang, Li-Kun Yao, Chen-Song Du, Shu-Xing Ye, JunJie Xidian Univ Minist Educ Key Lab Elect Equipment Struct Design Xian 710071 Shaanxi Peoples R China

Dot-grid images are usually captured for grid strain analysis during sheet metal forming. Due to the strong reflective characteristic of the metallic surfaces, the recorded dot-grid images often have poor quality, low positioning accuracy, and low recognition rate. Therefore, an exposure-fusion-based dot-grid image acquisition and recognition approach is proposed. First, multiple dot-grid images are captured at different exposure levels. Subsequently, the recorded multi-exposure dot-grid images are fused into a new high-quality dot-grid image based on exposure fusion technology. Finally, a dot-grid image recognition procedure is developed to detect the dot-grids in the new dot-grid image. Both synthetic and real dot-grid images were tested to verify the performance of the novel approach. When synthetic dot-grid images were tested, the maximum positioning error was up to 6.044 pixels if they were recognized in the traditional way, whereas the maximum positioning error was reduced to 0.132 pixels if the novel approach was adopted. When real dot-grid images were tested, the lowest recognition rate is only 50.52% if they were recognized in the traditional way. Nevertheless, the recognition rate can reach about 91% if the novel approach was employed. These experimental results show the superiorities of the novel approach. (C) 2017 Optical Society of America

关键词： Digital image processing Edge detection image processing algorithms Optical measurement Speckle patterns Strain measurement

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Light field camera study of near-ground turbulence anisotropy and observation of small outer-scales

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OPTICS LETTERS 2020年第5期45卷 1156-1159页

作者： Wu, Chensheng Paulson, Daniel A. Rzasa, John R. Davis, Christopher C. Univ Maryland Elect & Comp Engn Dept College Pk MD 20742 USA Univ Maryland Bioengn Dept College Pk MD 20742 USA Univ Maryland Fischell Inst Biomed Devices College Pk MD 20742 USA

Understanding turbulence effects on laser beam propagation is critical to the emerging design, study, and test of many long-range free space optical (FSO) communication and directed energy systems. Conventional studies make the prevalent assumption of isotropic turbulence, while more recent results suggest anisotropic turbulence for atmospheric channels within a few meters elevation above the ground. As countless FSO systems have been and continue to be deployed in such channels, analysis of anisotropic modelings has become one of the fastest growing areas in FSO research. This in turn motivates new tools that can distinguish anisotropic characteristics to improve both modeling accuracy and physical interpretations. Wavefront sensors such as Shack-Hartmann sensors, interferometers, and plenoptic sensors have been devised and used in experiments;however, they all require rigid alignments that lack resilience against temperature gradient buildup and beam wander. We find that by using a light field camera (LFC) that extracts perturbation of individual light rays, the wave structure function of turbulence can be retrieved with high reliability. Furthermore, we find through experiments that the outer scales of near-ground turbulence tend to be a magnitude smaller than conventional theoretical assumptions, agreeing with new findings by others but being absent in current theoretical modelings. As a result, we believe that the LFC is an ideal candidate in the frontier of turbulence research;it is both commercially available and easy to adapt to turbulence experiments. (C) 2020 Optical Society of America

关键词： Atmospheric turbulence image processing algorithms Laser beam propagation Plenoptic imaging Power spectral density Turbulence effects

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