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

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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Defect detectability based on square wave lock-in thermography

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APPLIED OPTICS 2022年第21期61卷 6134-6143页

作者： Zhu, Pengfei Wu, Dan Wang, Yifan Miao, Zhifei Ningbo Univ Sch Mech Engn & Mech Key Lab Impact & Safety Engn Minist Educ Ningbo 315211 Peoples R China

A lock-in thermography technique based on a periodical square wave is used to detect stainless steel plates with defects. Combining a neural network with lock-in thermography, an image processing technique is proposed, and the results are compared with traditional image processing methods. A full-field defect reconstruction technology is proposed that combines pulsed phase thermography, threshold segmentation technology, and lock-in thermography technology to reconstruct the full-field depth image. This method has fast processing speed and high detection accuracy. Finally, the effects of excitation frequency and duty cycle on thermal image quality, defect detect ion range, and defect detection accuracy are investigated through extensive experiments to arrive at the optimal excitation frequency and duty cycle. (C) 2022 Optica Publishing Group

关键词： Fourier transforms image processing image processing algorithms image quality Neural networks Thermal imaging

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Correlation-based receiver for optical camera communications

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OPTICS EXPRESS 2019年第14期27卷 19150-19155页

作者： Jurado-Verdu, Cristo Matus, Vicente Rabadan, Jose Guerra, Victor Perez-Jimenez, Rafael Univ Las Palmas Gran Canaria IDeTIC Las Palmas Gran Canaria Spain

In color-multiplexed optical camera communications (OCC) systems, data acquisition is restricted by the image processing algorithm capability for fast source recognition, region-of-interest (ROI) detection and tracking, packet synchronization within ROI, estimation of inter-channel interference and threshold computation. In this work, a novel modulation scheme for a practical RGB-LED-based OCC system is presented. The four above-described tasks are held simultaneously. Using confined spatial correlation of well-defined reference signals within the frame's color channels is possible to obtain a fully operating link with low computational complexity algorithms. Prior channel adaptation also grants a substantial increase in the attainable data rate, making the system more robust to interferences. (c) 2019 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

关键词： image processing image processing algorithms LED sources Optical receivers Space division multiplexing Visible light communications

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Open-top axially swept light-sheet microscopy

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BIOMEDICAL OPTICS EXPRESS 2021年第4期12卷 2328-2338页

作者： Kim, Bumju Na, Myeongsu Park, Soohyun Kim, Kitae Park, Jung-Hoon Chung, Euiheon Chang, Sunghoe Kim, Ki Hean Pohang Univ Sci & Technol Div Integrat Biosci & Biotechnol 77 Cheongam Ro Pohang 37673 Gyeongbuk South Korea Seoul Natl Univ Dept Physiol & Biomed Sci Med Res Ctr Coll Med 103 Daehak Ro Seoul 03080 South Korea Pohang Univ Sci & Technol Dept Mech Engn 77 Cheongam Ro Pohang 37673 Gyeoungbuk South Korea Ulsan Natl Inst Sci & Technol UNIST Dept Biomed Engn Ulsan 44919 South Korea Gwangju Inst Sci & Technol Dept Biomed Sci & Engn Gwangju 61005 South Korea

Open-top light-sheet microscopy (OT-LSM) is a specialized microscopic technique for high throughput cellular imaging of large tissue specimens including optically cleared tissues by having the entire optical setup below the sample stage. Current OT-LSM systems had relatively low axial resolutions by using weakly focused light sheets to cover the imaging field of view (FOV). In this report, open-top axially swept LSM (OTAS-LSM) was developed for high-throughput cellular imaging with improved axial resolution. OTAS-LSM swept a tightly focused excitation light sheet across the imaging FOV using an electro tunable lens (ETL) and collected emission light at the focus of the light sheet with a camera in the rolling shutter mode. OTAS-LSM was developed by using air objective lenses and a liquid prism and it had on-axis optical aberration associated with the mismatch of refractive indices between air and immersion medium. The effects of optical aberration were analyzed by both simulation and experiment, and the image resolutions were under 1.6 & micro;m in all directions. The newly developed OTAS-LSM was applied to the imaging of optically cleared mouse brain and small intestine, and it demonstrated the single-cell resolution imaging of neuronal networks. OTAS-LSM might be useful for the high-throughput cellular examination of optically cleared large tissues. (c) 2021 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

关键词： image processing image processing algorithms image resolution Light sheet microscopy Tunable lenses Wave front sensing

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Three-dimensional collagen fiber mapping and tractography of human uterine tissue using OCT

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BIOMEDICAL OPTICS EXPRESS 2020年第10期11卷 5518-5541页

作者： McLean, James P. Fang, Shuyang Gallos, George Myers, Kristin M. Hendon, Christine P. Columbia Univ Dept Elect Engn New York NY 10027 USA Columbia Univ Dept Mech Engn New York NY 10027 USA Columbia Univ Irving Med Ctr Dept Anesthesiol New York NY 10032 USA

Automatic quantification and visualization of 3-D collagen fiber architecture using Optical Coherence Tomography (OCT) has previously relied on polarization information and/or prior knowledge of tissue-specific fiber architecture. This study explores image processing, enhancement, segmentation, and detection algorithms to map 3-D collagen fiber architecture from OCT images alone. 3-D fiber mapping, histogram analysis, and 3-D tractography revealed fiber groupings and macro-organization previously unseen in uterine tissue samples. We applied our method on centimeter-scale mosaic OCT volumes of uterine tissue blocks from pregnant and non-pregnant specimens revealing a complex, patient-specific network of fibrous collagen and myocyte bundles. (C) 2020 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

关键词： High speed imaging image processing image processing algorithms image quality Second harmonic generation Three dimensional imaging

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Retrieval of the planetary boundary layer height from lidar measurements by a deep-learning method based on the wavelet covariance transform

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OPTICS EXPRESS 2022年第10期30卷 16297-16312页

作者： Mei, Liang Wang, Xiaoqi Gong, Zhenfeng Liu, Kun Hua, Dengxin Wang, Xiaona Dalian Univ Technol Sch Optoelect Engn & Instrumentat Sci Dalian 116024 Peoples R China Xian Univ Technol Sch Mech & Precis Instrument Engn Xian 710048 Peoples R China Dalian Univ Technol Sch Phys Dalian 116024 Peoples R China

Understanding and characterization of the planetary boundary layer (PBL) are of great importance in terms of air pollution management, weather forecasting, modelling of climate change, etc. Although many lidar-based approaches have been proposed for the retrieval of the PBL height (PBLH) in case studies, development of a robust lidar-based algorithm without human intervention is still of great challenging. In this work, we have demonstrated a novel deep-learning method based on the wavelet covariance transform (WCT) for the PBLH evaluation from atmospheric lidar measurements. Lidar profiles are evaluated according to the WCT with a series of dilation values from 200 m to 505 m to generate 2-dimensional wavelet images. A large number of wavelet images and the corresponding PBLH-labelled images are created as the training set for a convolutional neural network (CNN), which is implemented based on a modified VGG16 (VGG - Visual Geometry Group) convolutional neural network. Wavelet images obtained from lidar profiles have also been prepared as the test set to investigate the performance of the CNN. The PBLH is finally retrieved by evaluating the predicted PBLH-labelled image and the wavelet coefficients. Comparison studies with radiosonde data and the Micro-Pulse-Lidar Network (MPLNET) PBLH product have successfully validated the promising performance of the deep-learning method tbr the PBLH retrieval in practical atmospheric sensing. (C) 2022 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement

关键词： Atmospheric measurement High power diode lasers image processing algorithms Lidar Neural networks Wavelet transforms

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Diagnosis of liquid-gas mixed sprays in the near-field region using femtosecond laser induced supercontinuum imaging method

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OPTICS EXPRESS 2020年第3期28卷 3298-3304页

作者： Wang, Mingxin Tan, Wenjiang Si, Jinhai Zheng, Yipeng Huang, Zhenqiang Xi An Jiao Tong Univ Key Lab Phys Elect & Devices Minist Educ Shannxi Key Lab Informat Photon TechSch Elect Sc Xianning Xilu 28 Xian 710049 Peoples R China

Direct femtosecond shadowgraphy and supercontinuum (SC)-illumination imaging methods for diagnosing liquid-gas mixed sprays in the near-field region of spray nozzles were compared. Some big spray structures can be captured using femtosecond shadowgraphy which can freeze the motion of the sprays. But the speckles caused by the interference of multi-scattered photons erode the edges of ligaments and conceal many fine droplets. SC-illumination imaging can not only freeze the motion of the sprays but also significantly suppressing the speckles, presenting a more realistic spray pattern. Based on the SC imaging technology, the effects of various factors such as flow ratio of gas to liquid (GLR), total flow and nozzle size on the spray were studied. (C) 2020 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

关键词： Digital image processing image processing algorithms image quality Imaging systems Imaging techniques Speckle patterns

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Monitoring of vital bio-signs by analysis of speckle patterns in a fabric-integrated multimode optical fiber sensor

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OPTICS EXPRESS 2020年第14期28卷 20830-20844页

作者： Bennett, Aviya Beiderman, Yevgeny Agdarov, Sergey Beiderman, Yafim Hendel, Rotem Straussman, Barak Zalevsky, Zeev Bar Ilan Univ Fac Engn Ramat Gan Israel Nanotechnol Ctr Ramat Gan Israel Technion Israel Inst Technol Dept Elect Engn Haifa Israel

Continuous noninvasive measurement of vital bio-signs, such as cardiovascular parameters, is an important tool in evaluation of the patient's physiological condition and health monitoring. Based on new enabling technologies, continuous monitoring of heart and respiration rate, pulse wave velocity and blood pressure have been investigated, advanced and reflected in numerous papers published in recent years. In this paper, we introduce a new technique for noninvasive sensing of vital bio-signs based on a multimode optical fiber sensor that can be integrated into a fabric. The sensor consists of a laser, optical fiber, video camera and computer. Its operation is based on tracking of point-wise intensity variations on speckle patterns caused by interference of the light modes within the fiber subjected to deformation. The paper contains theoretical analysis and experimental validation of the proposed scheme. The main goal is to advance a simple low-cost sensor embedded in a cloth fabric to track changes in the cardiovascular condition of the wearer. (C) 2020 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

关键词： Bending sensors image processing algorithms Laser sensors Optical sensing Sensor performance Speckle patterns

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Single-lens multi-mirror laser stereo vision-based system for measuring internal thread geometrical parameters

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OPTICS EXPRESS 2022年第26期30卷 47625-47646页

作者： LI, Xiao LI, Wei Xin, Haijun Zhou, Jingyu Chen, Huaiyuan Chen, Xingpei Yin, Xiaokang Yuan, Xin'an Ma, Xin China Univ Petr East China Dept Mech & Elect Engn Qingdao 266580 Shandong Peoples R China Weifang Inst Special Equipment Inspection & Res Wei Fang Peoples R China CUHK Dept Mech & Automat Engn Hong Kong Peoples R China

Oilfield pipes with out-of-tolerance internal thread can lead to failures, so the internal thread geometric parameters need to be measured. To tackle the problem of the low efficiency, poor accuracy, easy wear, and poor accessibility of existing methods, a single-lens multi-mirror laser stereo vision-based system for measuring geometric parameters of the internal thread is proposed, which allows the measurement of three parameters in one setup by completely reproducing the three-dimensional (3D) tooth profiles of the internal thread. In the system design, to overcome the incomplete representation of imaging parameters caused by insufficient consideration of dimensions and structural parameters of the existing models, an explicit 3D optical path model without a reflecting prism is first proposed. Then, considering the intervention of the reflecting prism, a calculation model for the suitable prism size and the final imaging parameters of the vision system is proposed, which ensures the measurement accessibility and accuracy by solving the problem that the existing system design only depends on experience without theoretical basis. Finally, based on the American Petroleum Institute standard, internal thread geometric parameters are obtained from the vision-reconstructed 3D tooth profiles. According to the optimized structural parameters, a vision system is built for measuring the internal thread geometric parameters of two types of oilfield pipes. Accuracy verification and typical internal thread measurement results show that the average measurement errors of the vision system proposed for the pitch, taper, and tooth height are 0.0051 mm, 0.6055 mm/m, and 0.0071 mm, respectively. Combined with the vision measurement time of 0.5 s for the three parameters, the above results comprehensively verify the high accuracy and high efficiency of the vision-based system.(c) 2022 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement

关键词： Bandpass filters Camera calibration image processing algorithms Optical elements Systems design X ray computed tomography

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Improved one-dimensional dilation-based top-hat algorithm for star segmentation under complicated background conditions

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APPLIED OPTICS 2022年第27期61卷 8006-8016页

作者： Ding, Jianqun Dai, Dongkai Tan, Wenfeng Wang, Xingshu Qin, Shiqiao Natl Univ Def Technol Coll Adv Interdisciplinary Studies Changsha 410073 Peoples R China Huaihua Univ Sch Elect & Informat Engn Huaihua 418000 Peoples R China

The white top-hat transformation has been widely used in small bright target extraction. It usually applies an erosion operation to remove the target and then a dilation operation to recover the intensity of the processed image. A bright target will be extracted by subtracting the opening operation (erosion followed by dilation) from the raw image. The drawback of this method is that its denoising ability is poor because the estimated background threshold by an opening operation is smaller than the raw image. This study puts forward the viewpoint that by use of a proposed one-dimensional (1D) symmetrical line-shaped structuring element a bright target can also be removed by the dilation operation. Consequently, the white top-hat transformation can be implemented by subtracting only the dilation operation from the raw image. To the best knowledge of the authors, it is the first time to use this method to achieve the top-hat transformation. The simulation experiment shows that the proposed 1D top-hat algorithm has excellent performance in denoising ability and detection ability. Moreover, real night experiments demonstrate that our proposed algorithm can work reliably under both complicated background conditions and good weather conditions. It is noticeable that the performance of computational efficiency and resource consumption have been considerably improved because a 1D structuring element is employed and the erosion operation is not included. (C) 2022 Optica Publishing Group

关键词： Edge detection image enhancement image processing image processing algorithms Medical image processing Point spread function

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