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Effective star tracking method based on optical flow analysis for star trackers

APPLIED OPTICS 2016年第36期55卷 10335-10340页

作者： Sun, Ting Xing, Fei Wang, Xiaochu Li, Jin Wei, Minsong You, Zheng Tsinghua Univ Dept Precis Instrument Beijing 100084 Peoples R China Beijing Informat Sci & Technol Univ Sch Instrument Sci & Opto Elect Engn Beijing 100192 Peoples R China China Acad Space Technol Qian Xuesen Lab Space Technol Beijing 100094 Peoples R China

Benefiting from rapid development of imaging sensor technology, modern optical technology, and a high-speed computing chip, the star tracker's accuracy, dynamic performance, and update rate have been greatly improved with low power consumption and miniature size. The star tracker is currently one of the most competitive attitude measurement sensors. However, due to restrictions of the optical imaging system, difficulties still exist in moving star spot detection and star tracking when in special motion conditions. An effective star tracking method based on optical flow analysis for star trackers is proposed in this paper. Spot-based optical flow, based on a gray gradient between two adjacent star images, is analyzed to distinguish the star spot region and obtain an accurate star spot position so that the star tracking can keep continuous under high dynamic conditions. The obtained star vectors and extended Kalman filter (EKF) are then combined to conduct an angular velocity estimation to ensure region prediction of the star spot;this can be combined with the optical flow analysis result. Experiment results show that the method proposed in this paper has advantages in conditions of large angular velocity and large angular acceleration, despite the presence of noise. Higher functional density and better performance can be achieved;thus, the star tracker can be more widely applied in small satellites, remote sensing, and other complex space missions. (C) 2016 Optical Society of America

关键词： image analysis image processing algorithms image sensors Imaging noise Optical flow Remote sensing

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Continuous zoom compound eye imaging system based on liquid lenses

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OPTICS EXPRESS 2021年第23期29卷 37565-37579页

作者： Zheng, Yi Wang, Di Jiang, Zhao Liu, Chao Wang, Qiong-Hua Beihang Univ Sch Instrumentat & Optoelect Engn Beijing 100191 Peoples R China

In this paper, a continuous zoom compound eye imaging system based on liquid lenses is proposed. The main imaging part of the system consists of a liquid compound eye, two liquid lenses and a planar image sensor. By adjusting the liquid injection volumes of the liquid compound eye and liquid lenses, the system can realize continuous zoom imaging without any mechanical movement of imaging components. According to the results of experiments, the paraxial magnification of the target can range from similar to 0.019x to similar to 0.037x at a fixed working distance. Moreover, the system can realize continuous focusing at a fixed paraxial magnification when the working distance ranges from similar to 200mm to similar to 300mm. Compared with the traditional artificial compound eye imaging systems, the proposed system increases the adjustability and matches the variable image surfaces of the liquid compound eye to a planar image sensor. The aspherical effects of the liquid compound eye and liquid lenses are also considered in the design of the system. The system is expected to be used for imaging in various scenes, such as continuous zoom panoramic imaging, 3D scanning measurement and so on. (C) 2021 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement

关键词： image processing algorithms image quality Imaging systems Liquid lenses Optical imaging Planar lenses

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Improvement of an optical image by the measurement reduction technique at parametric multiplexing

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JOURNAL OF THE OPTICAL SOCIETY OF AMERICA B-OPTICAL PHYSICS 2019年第4期36卷 901-909页

作者： Balakin, D. A. Chirkin, A. S. Moscow MV Lomonosov State Univ Fac Phys Leninskie Gory 1Bld 2 Moscow 119991 Russia Moscow MV Lomonosov State Univ Int Laser Ctr Leninskie Gory 1Bld 62 Moscow 119991 Russia

In the process of parametric optical image amplification, images are formed at new frequencies in addition to the amplified original image. We show that parametric multiplexing of optical images can be used to produce an image with improved quality. As an example, we study the parametric amplification of an optical image at low-frequency pumping in which multiplexed optical images turn out to be quantum-correlated. Additional improvement is made possible by using the information about the object that is available to the researcher, in particular, about sparsity of its image. To take the available information into account, we apply the measurement reduction technique. (C) 2019 Optical Society of America

关键词： Fourier transforms image processing image processing algorithms image quality Point spread function Wavelet transforms

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Integral image rendering procedure for aberration correction and size measurement

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APPLIED OPTICS 2014年第15期53卷 3176-3182页

作者： Sommer, Holger Ihrig, Andreas Ebenau, Melanie Fluehs, Dirk Spaan, Bernhard Eichmann, Marion Tech Univ Dortmund Fak Phys D-44221 Dortmund Germany Univ Klinikum Essen Klin Strahlenphys D-45122 Essen Germany

The challenge in rendering integral images is to use as much information preserved by the light field as possible to reconstruct a captured scene in a three- dimensional way. We propose a rendering algorithm based on the projection of rays through a detailed simulation of the optical path, considering all the physical properties and locations of the optical elements. The rendered images contain information about the correct size of imaged objects without the need to calibrate the imaging device. Additionally, aberrations of the optical system may be corrected, depending on the setup of the integral imaging device. We show simulation data that illustrates the aberration correction ability and experimental data from our plenoptic camera, which illustrates the capability of our proposed algorithm to measure size and distance. We believe this rendering procedure will be useful in the future for three-dimensional ophthalmic imaging of the human retina. (C) 2014 Optical Society of America

关键词： image processing algorithms image quality Light fields Medical imaging Optical aberrations Three dimensional imaging

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Active photonic sensing for super-resolved reading performance in simulated prosthetic vision

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BIOMEDICAL OPTICS EXPRESS 2019年第3期10卷 1081-1096页

作者： Abraham, Chen Farah, Nairouz Gerbi-Zarfati, Liron Harpaz, Yuval Zalvesky, Zeev Mandel, Yossi Bar Ilan Univ Fac Engn Ramat Gan Israel Bar Ilan Univ Nanotechnol Ctr Ramat Gan Israel Bar Ilan Univ Fac Life Sci Sch Optometry & Vis Sci Ramat Gan Israel Bar Ilan Univ Bar Ilan Inst Nanotechnol & Adv Mat BINA Ramat Gan Israel Bar Ilan Univ Gonda Brain Res Ctr Ramat Gan Israel

In this work, we study the enhancement of simulated prosthetic reading performance through "active photonic sensing" in normally sighted subjects. Three sensing paradigms were implemented: active sensing, in which the subject actively scanned the presented words using the computer mouse, with an option to control text size;passive scanning produced by software-initiated horizontal movements of words;and no scanning. Our findings reveal a 30% increase in word recognition rate with active scanning as compared to no or passive scanning and up to 14-fold increase with zooming. These results highlight the importance of a patient interactive interface and shed light on techniques that can greatly enhance prosthetic vision quality. (C) 2019 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

关键词： Eye movements Field size image processing algorithms Retinal ganglion cells Visual acuity Visual system

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Real-time visible light positioning supporting fast moving speed

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OPTICS EXPRESS 2020年第10期28卷 14503-14510页

作者： Lin, Puxi Hu, Xubin Ruan, Yukui Li, Huaping Fang, Junjian Zhong, Yongchun Zheng, Huadan Fang, Junbin Jiang, Zoe Lin Chen, Zhe Jinan Univ Guangdong Prov Engn Technol Res Ctr VLC Guangzhou Municipal Key Lab Engn Technol VLC Guangzhou 510632 Peoples R China Jinan Univ Dept Optoelect Engn Guangzhou 510632 Peoples R China Peng Cheng Lab Cyberspace Secur Res Ctr Shenzhen 518055 Peoples R China Harbin Inst Technol Shenzhen 518055 Peoples R China

Real-time capability is a key factor which affects the practicality of an indoor positioning system significantly. While visible light positioning (VLP) is widely studied since it can provide indoor positioning functionality with LED illumination, the existing VLP systems still suffer from the high positioning latency and are not practical for mobile units with high moving speed. In this paper, a real-time VLP system with low positioning latency and high positioning accuracy is proposed. With the lightweight image processing algorithm, the proposed system can be implemented on low-cost embedded system and support real-time accurate indoor positioning for mobile units with a fast moving speed. Experimental results show that the proposed system implemented on a Raspberry Pi can achieve a positioning accuracy of 3.93 cm and support the moving speed up to 38.5 km/h. (c) 2020 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

关键词： image processing image processing algorithms image sensors LED lighting Ultrawideband signals Visible light

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Automatic target detection in forward-looking infrared imagery via probabilistic neural networks

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APPLIED OPTICS 2009年第3期48卷 464-476页

作者： Khan, Jesmin F. Alam, Mohammad S. Bhuiyan, Sharif M. A. Univ Alabama Dept Elect & Comp Engn Huntsville AL 35899 USA Univ S Alabama Dept Elect & Comp Engn Mobile AL 36688 USA

This paper presents a technique for automatic detection of the targets in forward-looking infrared (FLIR) imagery. Mathematical morphology is applied for the preliminary selection of possible regions of interest (ROI). An efficient clutter rejecter module based on probabilistic neural network is proposed, which is trained by using both target and background features to ensure excellent classification performance by moving the ROI in several directions with respect to the center of the detected target patch. Experimental results using real-life FLIR imagery confirm the excellent performance of the detector and the effectiveness of the proposed clutter rejecter module. (C) 2009 Optical Society of America

关键词： Feature extraction Forward looking infrared image processing image processing algorithms Neural networks Wavelet transforms

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Optical coherence tomography for quality assessment of embedded microchannels in alumina ceramic

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OPTICS EXPRESS 2012年第4期20卷 4603-4618页

作者： Su, Rong Kirillin, Mikhail Ekberg, Peter Roos, Arne Sergeeva, Ekaterina Mattsson, Lars Royal Inst Technol Dept Prod Engn S-10044 Stockholm Sweden Inst Appl Phys RAS Lab Biophoton Nizhnii Novgorod 603950 Russia Uppsala Univ Angstrom Lab S-75121 Uppsala Sweden

Large-scale and cost-effective manufacturing of ceramic micro devices based on tape stacking requires the development of inspection systems to perform high-resolution in-process quality control of embedded manufactured cavities, metal structures and defects. With an optical coherence tomography (OCT) system operating at 1.3 mu m and a dedicated automated line segmentation algorithm, layer thicknesses can be measured and laser-machined channels can be verified in alumina ceramics embedded at around 100 mu m depth. Monte Carlo simulations are employed to analyze the abilities of OCT in imaging of the embedded channels. The light scattering parameters required as input data for simulations are evaluated from the integrating sphere measurements of collimated and diffuse transmittance spectra using a reconstruction algorithm based on refined diffusion approximation approach. (C)2012 Optical Society of America

关键词： image processing algorithms image quality Light scattering Optical coherence tomography Reconstruction algorithms Speckle reduction

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Theoretical foundations for joint digital-optical analysis of electro-optical imaging systems

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APPLIED OPTICS 2008年第10期47卷 B64-B75页

作者： Stork, David G. Robinson, M. Dirk Ricoh Innovat Menlo Pk CA 94025 USA

We describe the mathematical and conceptual foundations for a novel methodology for jointly optimizing the design and analysis of the optics, detector, and digital image processing for imaging systems. Our methodology is based on the end-to-end merit function of predicted average pixel sum-squared error to find the optical and image processing parameters that minimize this merit function. Our approach offers several advantages over the traditional principles of optical design, such as improved imaging performance, expanded operating capabilities, and improved as-built performance, (C) 2008 Optical Society of America.

关键词： Digital image processing image processing image processing algorithms image quality Imaging systems Wavefront encoding

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Toward omnidirectional and automated imaging system for measuring oceanic whitecap coverage

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JOURNAL OF THE OPTICAL SOCIETY OF AMERICA A-OPTICS image SCIENCE AND VISION 2018年第4期35卷 515-521页

作者： Al-Lashi, Raied S. Webster, Merlin Gunn, Steve R. Czerski, Helen Univ Leeds Fac Math & Phys Sci Sch Food Sci & Nutr Leeds W Yorkshire England Univ Southampton Fac Phys Sci & Engn Sch Elect & Comp Sci Southampton Hants England UCL Fac Engn Sci Dept Mech Engn London England

Accurate measurements of the oceanic whitecap coverage from whitecap images are required for better understanding the air - gas transfer and aerosol production processes. However, this is a challenging task because the whitecap patches are formed immediately after the wave breaks and are spread over a wide area. The main challenges in designing a whitecap-imaging instrument are the small field of view of the camera lens, processing large numbers of images, recording data over long time periods, and deployment difficulties in stormy conditions. This paper describes the design of a novel high-resolution optical instrument for imaging oceanic whitecaps and the automated algorithm processing the collected images. The instrument was successfully deployed in 2013 as part of the HiWINGS campaign in the North Atlantic Ocean. The instrument uses a fish-eye camera lens to image the whitecaps in wide angle of view (180 degrees).

关键词： Camera calibration image processing image processing algorithms image quality image resolution Imaging techniques

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