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Integrated holographic waveguide display system with a common optical path for visible and infrared light

OPTICS EXPRESS 2018年第25期26卷 32802-32811页

作者： Lv, Zhenlv Liu, Juan Xiao, Jiasheng Kuang, Ying Beijing Inst Technol Sch Opt & Photon Beijing Engn Res Ctr Mixed Real & Adv Display Beijing 100081 Peoples R China

We propose an integrated holographic waveguide display system. An infrared volume holographic grating (IVHG) and a visible light grating are recorded on the mine waveguide to achieve the purpose of a common light path for system miniaturization. Simulated and experimental results verify the feasibility of this method. The coupling efficiencies of the infrared module for eye tracking and the visible light module for augmented reality (AR) display are 40% and 45%. The holographic waveguide has a weight of only 4.3 grams. It is believed that this technique is a good way to achieve a light and thin eye tracking near-eye display. (C) 2018 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

关键词： Diffraction efficiency Diffractive optical elements Holographic displays Holographic recording materials image processing algorithms Total internal reflection

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Printed cylindrical lens pair for application to the seam concealment in tiled displays

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OPTICS EXPRESS 2018年第2期26卷 824-834页

作者： Lee, Seunghwan Lee, Seungjae Yoon, Hyungsoo Lee, Chang-Kun Yoo, Chanhyung Park, Jongjang Byun, Junghwan Kim, Geonhee Lee, Byeongmoon Lee, Byoungho Hong, Yongtaek Seoul Natl Univ Dept Elect & Comp Engn Gwanakro 1 Seoul 08826 South Korea Seoul Natl Univ Inter Univ Semicond Res Ctr ISRC Gwanakro 1 Seoul 08826 South Korea

Seamless tiling of displays is one of the key enabling technologies for the next-generation large-area electronics applications. In this paper, we propose a facile method to demonstrate a seamless display using cylindrical lens pair (CLP) fabricated by dispenser printing method. Optical properties of the printed CLP and corresponding capability of concealing seam in the display are analyzed by a set of luminance simulation and measurement in terms of geometric parameters of the lens. The seamless display with an optimized CLP features a viewing angle of the seam concealment of 40 degrees. (C) 2018 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

关键词： Cylindrical lenses Flat panel displays image processing image processing algorithms LED backlights White light emitting diodes

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Efficient coding and detection of ultra-long IDs for visible light positioning systems

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OPTICS EXPRESS 2018年第10期26卷 13397-13407页

作者： Zhang, Hualong Yang, Chuanchuan Peking Univ State Key Lab Adv Opt Commun Syst & Networks Beijing 100871 Peoples R China

Visible light positioning (VLP) is a promising technique to complement Global Navigation Satellite System (GNSS) such as Global positioning system (GPS) and BeiDou Navigation Satellite System (BDS) which features the advantage of low-cost and high accuracy. The situation becomes even more crucial for indoor environments, where satellite signals are weak or even unavailable. For large-scale application of VLP, there would be a considerable number of Light emitting diode (LED) IDs, which bring forward the demand of long LED ID detection. In particular, to provision indoor localization globally, a convenient way is to program a unique ID into each LED during manufacture. This poses a big challenge for image sensors, such as the CMOS camera in everybody's hands since the long ID covers the span of multiple frames. In this paper, we investigate the detection of ultra-long ID using rolling shutter cameras. By analyzing the pattern of data loss in each frame, we proposed a novel coding technique to improve the efficiency of LED ID detection. We studied the performance of Reed-Solomon (RS) code in this system and designed a new coding method which considered the trade-off between performance and decoding complexity. Coding technique decreases the number of frames needed in data processing, significantly reduces the detection time, and improves the accuracy of detection. Numerical and experimental results show that the detected LED ID can be much longer with the coding technique. Besides, our proposed coding method is proved to achieve a performance close to that of RS code while the decoding complexity is much lower. (C) 2018 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

关键词： CMOS cameras image processing image processing algorithms image quality Light intensity Visible light

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Lens magnification affects the estimates of refractive error obtained using eccentric infrared photorefraction

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JOURNAL OF THE OPTICAL SOCIETY OF AMERICA A-OPTICS image SCIENCE AND VISION 2018年第6期35卷 908-915页

作者： Bharadwaj, Shrikant R. Bandela, Praveen K. Nilagiri, Vinay Kumar LV Prasad Eye Inst Brien Holden Inst Optometry & Vis Sci Rd 2Banjara Hills Hyderabad 500034 Andhra Prades India LV Prasad Eye Inst Hyderabad Eye Res Fdn Prof Brien Holden Eye Res Ctr Rd 2Banjara Hills Hyderabad 500034 Andhra Prades India

Positive- and negative-powered ophthalmic lenses are used in eccentric infrared photorefraction to calibrate the device, correct the subject's baseline refractive error before an experimental manipulation, or stimulate blur-driven accommodation. Through theoretical modeling of luminance gradients formed across the pupil and empirical measurements of the eye's refractive error using a commercial photorefractor, this study shows that image magnification by positive lenses and image minification by negative lenses under- and overestimates the refractive error, respectively, all independent of image defocus. The impact of image magnification/minification therefore appears non-trivial in experimental paradigms involving ophthalmic lenses to manipulate the eye's optics during photorefraction. (c) 2018 Optical Society of America

关键词： Contact lenses Eye movements image processing algorithms Refractive anomalies Visual accommodation Visual acuity

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On the development of an effective image acquisition system or diamond quality grading

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APPLIED OPTICS 2018年第33期57卷 9887-9897页

作者： Wang, Wenjing Cai, Lilong Hong Kong Univ Sci & Technol Dept Mech Engn Kowloon Hong Kong Peoples R China

In this paper, an effective diamond image acquisition system is proposed for capturing images of the diamond sample under inspection separately with transmitted and reflected light. The proposed system consists of two parts: a lighting system and an imaging system. The lighting system is a newly designed integrating sphere that can control the light distribution in the image plane and provide uniform illumination to the diamond sample while it is being inspected under white LED lamps with a specific spectral power distribution. The imaging system comprises industrial-grade lenses, cameras, and a sample loading plate. One set of lenses and a camera is installed at the port of the lower hemisphere. This arrangement ensures that all light rays illuminated to the image plane are transmitted light. On die other hand, all light captured by the other set of lenses and a camera installed on the upper hemisphere is reflected light. The proposed design utilizes the ray tracing processing method based on the physical properties of materials and adjusts the parameters of each optical component. When properly designed, the signal-to-noise ratio of captured diamond images is significantly improved, so that imperfections inside the diamond or on its surface can be clearly distinguished. The proposed image acquisition system is cost-effective and compact. The experimental results agree well with the theoretical analysis and verify the effectiveness of the proposed image acquisition system. The proposed system will facilitate, improve, and simplify automated diamond quality grading. (C) 2018 Optical Society of America

关键词： Edge detection image processing image processing algorithms image quality Material properties Optical components

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250 kHz, 1.5 μm resolution SD-OCT for in-vivo cellular imaging of the human cornea

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BIOMEDICAL OPTICS EXPRESS 2018年第12期9卷 6569-6583页

作者： Tan, Bingyao Hosseinaee, Zohreh Han, Le Kralj, Olivera Sorbara, Luigina Bizheva, Kostadinka Univ Waterloo Dept Phys & Astron Waterloo ON N2L 3G1 Canada Singapore Natl Eye Ctr Singapore Eve Res Inst Singapore Singapore Univ Waterloo Dept Syst Design Engn Waterloo ON N2L 3G1 Canada Univ Waterloo Sch Optometry & Vis Sci Waterloo ON N2L 3G1 Canada

We present the first spectral domain optical coherence tomography (SD-OCT) system that combines an isotropic imaging resolution of similar to 1.5 mu m in biological tissue with a 250 kHz image acquisition rate, for in vivo non-contact, volumetric imaging of the cellular structure of the human cornea. OCT images of the healthy human cornea acquired with this system reveal the cellular structure of the corneal epithelium, cellular debris and mucin clusters in the tear film, the shape, size and spatial distribution of the sub-basal corneal nerves and keratocytes in the corneal stroma, as well as reflections from endothelial nuclei. The corneal images presented here demonstrate the potential clinical value of the new high speed. high resolution OCT system for non-invasive diagnostics and monitoring the treatment of corneal diseases. (C) 2018 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

关键词： Full field optical coherence tomography High speed photography image processing image processing algorithms Optical imaging Three dimensional imaging

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Real-time identification of the singleness of a trapped bead in optical tweezers

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APPLIED OPTICS 2018年第5期57卷 1241-1246页

作者： Hu, Chunguang Su, Chenguang Yun, Zelin Wang, Sirong He, Chengzhi Gao, Xiaoqing Li, Shuai Li, Hongbin Hu, Xiaodong Hu, Xiaotang Tianjin Univ State Key Lab Precis Measuring Technol & Instrume Tianjin 300072 Peoples R China Univ British Columbia Dept Chem Vancouver BC V6T 1Z1 Canada

Beads trapped in optical tweezers are aligned along the optical propagation direction, which makes it difficult to determine the number of beads with bright-field microscopy. This problem also dramatically influences the measurement of the optical trapping based single-molecule force spectroscopy. Here, we propose a video processing approach to count the number of trapped micro-objects in real time. The approach uses a normalized cross-correlation algorithm and image enhancement techniques to amplify a slight change of the image induced by the entry of an exotic object. As tested, this method introduces a similar to 10% change per bead to the image similarity, and up to four beads, one-by-one falling into the trap, are identified. Moreover, the feasibility of the above analysis in a moving trap is investigated. A movement of the trap leads to a fluctuation of less than 2% for the similarity signal and can be ignored in most cases. The experimental results prove that image similarity measurement is a sensitive way to monitor the interruption, which is very useful, especially during experiments. In addition, the approach is easy to apply to an existing optical tweezers system. (c) 2018 Optical Society of America

关键词： Coherence imaging image processing algorithms image quality Low coherence interferometry Optical measurement Optical tweezers

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Automatic quantification of choroidal neovascularization lesion area on OCT angiography based on density cell-like P systems with active membranes

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BIOMEDICAL OPTICS EXPRESS 2018年第7期9卷 3208-3219页

作者： Xue, Jie Camino, Acner Bailey, Steven T. Liu, Xiyu Li, Dengwang Jia, Yali Oregon Hlth & Sci Univ Casey Eye Inst Portland OR 97239 USA Shandong Normal Univ Sch Management Sci & Engn Jinan 250014 Shandong Peoples R China Shandong Normal Univ Sch Phys & Elect Shandong Prov Key Lab Med Phys & Image Proc Techn Jinan 250014 Shandong Peoples R China

Detecting and quantifying the size of choroidal neovascularization (CNV) is important for the diagnosis and assessment of neovascular age-related macular degeneration. Depth-resolved imaging of the retinal and choroidal vasculature by optical coherence tomography angiography (OCTA) has enabled the visualization of CNV. However, due to the prevalence of artifacts, it is difficult to segment and quantify the CNV lesion area automatically. We have previously described a saliency algorithm for CNV detection that could identify a CNV lesion area with 83% accuracy. However, this method works under the assumption that the CNV region is the most salient area for visual attention in the whole image and consequently, errors occur when this requirement is not met (e.g. when the lesion occupies a large portion of the image). Moreover, saliency image processing methods cannot extract the edges of the salient object very accurately. In this paper, we propose a novel and automatic CNV segmentation method based on an unsupervised and parallel machine learning technique named density cell-like P systems (DEC P systems). DEC P systems integrate the idea of a modified clustering algorithm into cell-like P systems. This method improved the accuracy of detection to 87.2% on 22 subjects and obtained clear boundaries of the CNV lesions. (C) 2018 Optical Society of America under the terms of the OSA Open Access Publishing Agreement.

关键词： Digital imaging image processing image processing algorithms Medical image processing Optical coherence tomography Pattern recognition

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RGB-to-RGBG conversion algorithm with adaptive weighting factors based on edge detection and minimal square error

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JOURNAL OF THE OPTICAL SOCIETY OF AMERICA A-OPTICS image SCIENCE AND VISION 2018年第6期35卷 969-976页

作者： Huang, Chengqiang Yang, Youchang Wu, Bo Yu, Weize Zunyi Normal Univ Sch Phys & Elect Sci Lab Applicat Specif Integrated Circuit Zunyi 563006 Peoples R China Old Dominion Univ Dept Elect & Comp Engn Norfolk VA 23529 USA

The sub-pixel arrangement of the RGBG panel and the image with RGB format are different and the algorithm that converts RGB to RGBG is urgently needed to display an image with RGB arrangement on the RGBG panel. However, the information loss is still large although color fringing artifacts are weakened in the published papers that study this conversion. In this paper, an RGB-to-RGBG conversion algorithm with adaptive weighting factors based on edge detection and minimal square error (EDMSE) is proposed. The main points of innovation include the following: (1) the edge detection is first proposed to distinguish image details with serious color fringing artifacts and image details which are prone to be lost in the process of RGB-RGBG conversion;(2) for image details with serious color fringing artifacts, the weighting factor 0.5 is applied to weaken the color fringing artifacts;and (3) for image details that are prone to be lost in the process of RGB-RGBG conversion, a special mechanism to minimize square error is proposed. The experiment shows that the color fringing artifacts are slightly improved by EDMSE, and the values of MSE of the image processed are 19.6% and 7% smaller than those of the image processed by the direct assignment and weighting factor algorithm, respectively. The proposed algorithm is implemented on a field programmable gate array to enable the image display on the RGBG panel. (C) 2018 Optical Society of America

关键词： Edge detection image display image metrics image processing image processing algorithms Organic light emitting diodes

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Focus detection by shearing interference of vortex beams for non-imaging systems

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APPLIED OPTICS 2018年第5期57卷 1037-1042页

作者： Li, Xiongfeng Zhan, Shichao Liang, Yiyong Zhejiang Univ State Key Lab Modern Opt Instrumentat Hangzhou 310027 Zhejiang Peoples R China

In focus detection of non-imaging systems, the common image-based methods are not available. Also, interference techniques are seldom used because only the degree with hardly any direction of defocus can be derived from the fringe spacing. In this paper, we propose a vortex-beam-based shearing interference system to do focus detection for a focused laser direct-writing system, where a vortex beam is already involved. Both simulated and experimental results show that fork-like features are added in the interference patterns due to the existence of an optical vortex, which makes it possible to distinguish the degree and direction of defocus simultaneously. The theoretical fringe spacing and resolution of this method are derived. A resolution of 0.79 mu m can be achieved under the experimental combination of parameters, and it can be further improved with the help of the image processing algorithm and closed-loop controlling in the future. Finally, the influence of incomplete collimation and the wedge angle of the shear plate is discussed. This focus detection approach is extremely appropriate for those non-imaging systems containing one or more focused vortex beams. (C) 2018 Optical Society of America

关键词： image processing algorithms Interference Laser beams Light beams Optical vortices Vortex beams

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