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Correction of uneven illumination in color microscopic image based on fully convolutional network

OPTICS EXPRESS 2021年第18期29卷 28503-28520页

作者： Wang, Jianhang Wang, Xin Zhang, Ping Xie, Shiling Fu, Shujun Li, Yuliang Han, Hongbin Shandong Univ Sch Math Jinan 250100 Peoples R China Dongying Peoples Hosp Dept Neonatal Dongying 257091 Peoples R China Shandong Shtars Biol Ind Co Dept Technol Dev Jinan 250100 Peoples R China Shandong Univ Hosp 2 Dept Intervent Med Jinan 250033 Peoples R China Peking Univ Third Hosp Dept Radiol Beijing 100191 Peoples R China Beijing Key Lab Magnet Resonance Imaging Equipmen Beijing 100191 Peoples R China

The correction of uneven illumination in microscopic image is a basic task in medical imaging. Most of the existing methods are designed for monochrome images. An effective fully convolutional network (FCN) is proposed to directly process color microscopic image in this paper. The proposed method estimates the distribution of illumination information in input image, and then carry out the correction of the corresponding uneven illumination through a feature encoder module, a feature decoder module, and a detail supplement module. In this process, overlapping residual blocks are designed to better transfer the illumination information, and in particular a well-designed weighted loss function ensures that the network can not only correct the illumination but also preserve image details. The proposed method is compared with some related methods on real pathological cell images qualitatively and quantitatively. Experimental results show that our method achieves the excellent performance. The proposed method is also applied to the preprocessing of whole slide imaging (WSI) tiles, which greatly improves the effect of image mosaicking. (C) 2021 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

关键词： image enhancement image processing image processing algorithms image quality Medical image processing Medical imaging

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Flame analysis using a simple transmission digital holographic interferometer

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APPLIED OPTICS 2021年第19期60卷 5623-5628页

作者： De La Torre I, Manuel H. Frausto-Reyes, Claudio Moreno-H, David Salgado-Transito, Ivan Ctr Invest Opt Unidad Aguascalientes Prol Constituc 607 Aguascalientes 20200 Aguascalientes Mexico Ctr Invest Opt Loma Bosque 115 Leon Mexico

A digital holographic interferometer using a collimated beam in transmission mode to illuminate a flow coming from a diffusion flame is presented. The optical system proposes an indirect visualization of the flow to avoid saturation at the sensor. It can detect the intensity signal as a classical schlieren technique and the phase changes due to the presence of the flow. It is possible to retrieve a pseudo-3D flow's view and different gradient maps using the optical phase. According to the knife edge's position, these gradients could be observed in classical schlieren one at a time, but the proposed system could retrieve them all with a single image hologram. As proof of principle, a flame's flow is simultaneously observed with the optical system and a Z-type schlieren set up. A comparison of the visualized flows at different stages of the flame is presented and discussed. A temperature profile is obtained and validated with a thermocouple's point thermal measurements taking the resulting optical phase. Results from both optical techniques show a good agreement. (C) 2021 Optical Society of America

关键词： Diffraction gratings Fourier transforms Holographic interferometry image processing algorithms Inhomogeneous optical media White light

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Real-time noise reduction based on ground truth free deep learning for optical coherence tomography

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BIOMEDICAL OPTICS EXPRESS 2021年第4期12卷 2027-2040页

作者： Huang, Yong Zhang, Nan Hao, Qun Beijing Inst Technol Sch Opt & Photon 5 South Zhongguancun St Beijing 100081 Peoples R China

Optical coherence tomography (OCT) is a high-resolution non-invasive 3D imaging modality, which has been widely used for biomedical research and clinical studies. The presence of noise on OCT images is inevitable which will cause problems for post-image processing and diagnosis. The frame-averaging technique that acquires multiple OCT images at the same or adjacent locations can enhance the image quality significantly. Both conventional frame averaging methods and deep learning-based methods using averaged frames as ground truth have been reported. However, conventional averaging methods suffer from the limitation of long image acquisition time, while deep learning-based methods require complicated and tedious ground truth label preparation. In this work, we report a deep learning-based noise reduction method that does not require clean images as ground truth for model training. Three network structures, including Unet, super-resolution residual network (SRResNet), and our modified asymmetric convolution-SRResNet (AC-SRResNet), were trained and evaluated using signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), edge preservation index (EPI) and computation time (CT). The effectiveness of these three trained models on OCT images of different samples and different systems was also investigated and confirmed. The SNR improvement for different sample images for L2-loss-trained Unet, SRResNet, and AC-SRResNet are 20.83 dB, 24.88 dB, and 22.19 dB, respectively. The SNR improvement for public images from different system for L1-loss-trained Unet, SRResNet, and AC-SRResNet are 19.36 dB, 20.11 dB, and 22.15 dB, respectively. AC-SRResNet and SRResNet demonstrate better denoising effect than Unet with longer computation time. AC-SRResNet demonstrates better edge preservation capability than SRResNet while Unet is close to AC-SRResNet. Eventually, we incorporated Unet, SRResNet, and AC-SRResNet into our graphic processing unit accelerated OCT imaging system for online n

关键词： image metrics image processing image processing algorithms image quality Noise reduction Three dimensional imaging

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Simultaneous measurements of foveal and peripheral aberrations with accommodation in myopic and emmetropic eyes

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BIOMEDICAL OPTICS EXPRESS 2021年第12期12卷 7422-7433页

作者： Romashchenko, Dmitry Papadogiannis, Petros Unsbo, Peter Lundstrom, Linda Royal Inst Technol Dept Appl Phys S-11421 Stockholm Sweden Johnson & Johnson Vis R&D NL-9728 NX Groningen Netherlands

The difference in peripheral retinal image quality between myopic and emmetropic eyes plays a major role in the design of the optical myopia interventions. Knowing this difference under accommodation can help to understand the limitations of the currently available optical solutions for myopia control. A newly developed dual-angle open-field sensor was used to assess the simultaneous foveal and peripheral (20 degrees nasal visual field) wavefront aberrations for five target vergences from -0.31 D to -4.0 D in six myopic and five emmetropic participants. With accommodation, the myopic eyes showed myopic shifts, and the emmetropic eyes showed no change in RPR. Furthermore, RPR calculated from simultaneous measurements showed lower infra-subject variability compared to the RPR calculated from peripheral measurements and target vergence. Other aberrations, as well as modulation transfer functions for natural pupils, were similar between the groups and the accommodation levels, foveally and peripherally. Results from viewing the same nearby target with and without spectacles by myopic participants suggest that the accommodative response is not the leading factor controlling the amplitude of accommodation microfluctuations. Published by The Optical Society under the terms of the Creative Commons Attribution 4.0 License.

关键词： Contact lenses image processing algorithms image quality Refractive anomalies Visual accommodation Wavefront aberrations

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Enhancing the performance of optical camera communication via accumulative sampling

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OPTICS EXPRESS 2021年第12期29卷 19015-19023页

作者： Zhang, Pinpin Wang, Qiuyu Yang, Yanbing Wang, Yunfeng Sun, Yimao Xu, Wenzheng Luo, Jun Chen, Liangyin Sichuan Univ Coll Comp Sci Chengdu 610065 Peoples R China Sichuan Univ Inst Ind Internet Res Chengdu 610065 Peoples R China Nanyang Mchnol Univ Sch Comp Sci & Engn 50 Nanyang Ave Singapore 639798 Singapore

Deemed as a practical approach to realize Visible Light Communication on commercial-off-the-shelf devices, the Optical Camera Communication (OCC) is attracting increasing attention, thanks to its readiness to be built purely upon ubiquitous LED illuminating infrastructure and handy smartphones. However, limited by the low sampling ability of the built-in camera on a smartphone, the performance of existing OCC systems is still far away from the requirements of practical applications. To this end, we further investigate the reception ability of the smartphone's camera and propose an accumulative sampling scheme to improve the performance of the OCC system. Essentially, the proposed scheme can use all the grayscale information of the pixels projected by the LED transmitter, whereas the conventional ones normally use single row (or column) pixels for demodulating. By implementing the lightweight demodulation algorithm with accumulative sampling, we experimentally verify its effectiveness for supporting higher transmission frequency hence better performance in terms of data rate. Extensive evaluations have shown the BERs of the proposed method are over 87% and 96% lower than that provided by the baselines at a maximum transmission frequency of 5 kHz for the Samsung S8 and iPhone 8 Plus receivers, respectively. (C) 2021 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

关键词： CMOS cameras image processing algorithms Machine vision Motion detection Optical wireless communication Visible light communications

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Phase imaging microscopy under the Gabor regime in a minimally modified regular bright-field microscope

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OPTICS EXPRESS 2021年第26期29卷 42738-42750页

作者： Mico, Vicente Trindade, Karina Angel Picazo-Bueno, Jose Univ Valencia Dept Opt & Optometria & Ciencias Vis C Doctor Moliner 50 Burjassot 46100 Spain

Quantitative phase imaging (QPI) is nowadays a powerful tool for visualization and analysis of biological processes. QPI is usually attained from specifically designed optical microscopes retrieving phase information in a quantitative way. In this paper we report on an extremely simple, low cost and compact way to update a standard bright-field microscope with coherent sensing capabilities. It is based on the in-line Gabor holography concept and only needs to replace the illumination broadband source of the regular microscope with a coherent one. The proposed methodology is completed by the recording of a digital in-line Gabor hologram instead of regular imaging conditions and by the numerical processing of the recorded hologram to finally achieve QPI. The selection of the defocus distance is critical to finally achieve high quality phase imaging, so calibration considering phase and amplitude test targets is presented for the proper definition of such defocus distance. In addition, the selected configuration is experimentally validated using different samples (microbeads, cheek cells and alive spermatozoa). All the experiments are implemented in a regular Olympus BX-60 upright microscope using a 20X 0.46NA objective lens. The proposed method shows how to convert a regular microscope into a holographic one with probably the minimum needed modifications and with the main limitation coming from the Gabor imaging conditions (weak diffractive samples and twin image presence). (C) 2021 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement

关键词： Digital image processing image processing algorithms image quality Imaging systems Optical microscopy Wave front sensing

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Label-free non-invasive subwavelength-resolution imaging using yeast cells as biological lenses

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BIOMEDICAL OPTICS EXPRESS 2021年第11期12卷 7113-7121页

作者： Jiang, Chunlei Yue, Hangyu Yan, Bing Dong, Taiji Cui, Xiangyu Chen, Peng Wang, Zengbo Northeast Petr Univ Coll Elect & Informat Engn Daqing 163318 Peoples R China Bangor Univ Sch Comp Sci & Elect Engn Dean St Bangor LL57 1UT Gwynedd Wales Chinese Acad Sci Ctr Opt Hlth Suzhou Inst Biomed Engn & Technol 88 Keling St Suzhou 215163 Jiangsu Peoples R China Northeast Petr Univ Coll Comp & Informat Technol Daqing 163318 Peoples R China

There is a growing interest to use live cells to replace the widely used non-biological microsphere lenses. In this work, we demonstrate the use of yeast cells for such imaging purpose. Using fiber-based optical trapping technique, we trap a chain of three yeast cells and bring them to the vicinity of imaging objects. These yeast cells work as near-field magnifying lenses and simultaneously pick up the sub-diffraction information of the nanoscale objects under each cell and project them into the far-field. The experimental results demonstrated that Blu-ray disc of 100 nm feature can be clearly resolved in a parallel manner by each cell. (c) 2021 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

关键词： image processing algorithms image quality Imaging techniques Optical imaging Scanning electron microscopy White light

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Algorithm for real-time defect detection of micro pipe inner surface

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APPLIED OPTICS 2021年第29期60卷 9167-9179页

作者： Zhao, Xinyu Wu, Bin Tianjin Univ State Key Lab Precis Measuring Technol & Instrume Tianjin 300072 Peoples R China

Quantitative analysis and identification of unknown shaped defects have always been difficult and challenging in the quality control of micro pipes. A series of algorithms for defect detection and feature recognition is presented in this study. A lightweight convolution neural network (LCNN) is introduced to realize defect discrimination. A shallow segmentation network is employed to cooperate with LCNN to obtain pixel-wise crack detection, and a feature recognition algorithm for quantitative measurement is presented. The experimental results show that the proposed algorithms can achieve defect detection with an accuracy of 98.5%, segmentation with mean intersection over union of 0.834, and latency of only 0.2 s. It can be used for online feature recognition and defect detection of the inner surface of a hole. (C) 2021 Optical Society of America

关键词： CMOS cameras image processing image processing algorithms Light intensity Neural networks Positioning equipment

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Design of a high-throughput telescope based on scanning an off-axis three-mirror anastigmat system

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APPLIED OPTICS 2021年第10期60卷 2817-2823页

作者： Ji, Huiru Zhu, Zhengbo Tan, Hao Shan, Yuefan Tan, Wei Ma, Donglin Huazhong Univ Sci & Technol Sch Opt & Elect Informat Wuhan 430074 Peoples R China Huazhong Univ Sci & Technol Wuhan Natl Lab Optoelect Wuhan 430074 Peoples R China Shenzhen Huazhong Univ Sci & Technol Shenzhen 518057 Peoples R China

A high-throughput optical system possesses a large field of view (FOV) and high resolution. However, it is a major challenge to design such a telescope with these two conflicting specifications. In this paper, we propose a method to design a high-throughput telescope based on the classical off-axis three-mirror anastigmat (TMA) configuration by introducing a scanning mechanism. We derive the optimum initial design for the TMA system with no primary aberrations through characteristic ray tracing. During the design process, a real exit pupil is necessitated to accommodate the scanning mirror. By gradually increasing the system's FOV during the optimization procedure, we finally obtained a high-throughput telescope design with an F-number of 6, a FOV of 60 degrees x 1.5 degrees, and a long focal length of 876 mm. In addition, a tolerance analysis is also conducted to demonstrate the instrumentation feasibility. We believe that this kind of large rectangle FOV telescope with high resolution has broad future applications in the optical remote sensing field. (C) 2021 Optical Society of America

关键词： image processing algorithms image quality Infrared telescopes Optical sensing Optical systems Systems design

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On the space-time statistics of motion pictures

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JOURNAL OF THE OPTICAL SOCIETY OF AMERICA A-OPTICS image SCIENCE AND VISION 2021年第7期38卷 908-923页

作者： Lee, Dae Yeol Ko, Hyunsuk Kim, Jongho Bovik, Alan C. Univ Texas Austin Dept Elect & Comp Engn Austin TX 78712 USA Hanyang Univ ERICA Div Elect Engn Ansan South Korea Elect & Telecommun Res Inst Media Coding Res Sect Daejeon South Korea

It is well known that natural images possess statistical regularities that can be captured by bandpass decomposition and divisive normalization processes that approximate early neural processing in the human visual system. We expand on these studies and present new findings on the properties of space-time natural statistics that are inherent in motion pictures. Our model relies on the concept of temporal bandpass (e.g., lag) filtering in lateral geniculate nucleus (LGN) and area V1, which is similar to smoothed frame differencing of video frames. Specifically, we model the statistics of the differences between adjacent or neighboring video frames that have been slightly spatially displaced relative to one another. We find that when these space-time differences are further subjected to locally pooled divisive normalization, statistical regularities (or lack thereof) arise that depend on the local motion trajectory. We find that bandpass and divisively normalized frame differences that are displaced along the motion direction exhibit stronger statistical regularities than for other displacements. Conversely, the direction-dependent regularities of displaced frame differences can be used to estimate the image motion (optical flow) by finding the space-time displacement paths that best preserve statistical regularity. (c) 2021 Optical Society of America

关键词： Eye movements image processing algorithms Motion estimation Motion perception Optical flow Visual system

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