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

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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Reconstruction of high-resolution 6 x 6-mm OCT angiograms using deep learning

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BIOMEDICAL OPTICS EXPRESS 2020年第7期11卷 3585-3600页

作者： Gao, Min Guo, Yukun Hormel, Tristan T. Sun, Jiande Hwang, Thomas S. Jia, Yali Oregon Hlth & Sci Univ Casey Eye Inst Portland OR 97239 USA Shandong Normal Univ Sch Informat Sci & Engn Jinan 250358 Peoples R China Oregon Hlth & Sci Univ Dept Biomed Engn Portland OR 97239 USA

Typical optical coherence tomographic angiography (OCTA) acquisition areas on commercial devices are 3x3- or 6x6-mm. Compared to 3x3-mm angiograms with proper sampling density, 6x6-mm angiograms have significantly lower scan quality, with reduced signal-to-noise ratio and worse shadow artifacts due to undersampling. Here, we propose a deep-learning-based high-resolution angiogram reconstruction network (HARNet) to generate enhanced 6x6-mm superficial vascular complex (SVC) angiograms. The network was trained on data from 3x3-mm and 6x6-mm angiograms from the same eyes. The reconstructed 6x6-mm angiograms have significantly lower noise intensity, stronger contrast and better vascular connectivity than the original images. The algorithm did not generate false flow signal at the noise level presented by the original angiograms. The image enhancement produced by our algorithm may improve biomarker measurements and qualitative clinical assessment of 6x 6-mm OCTA. (C) 2020 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 image reconstruction Retinal nerve fiber layer

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Sun backward gazing method for measuring optomechanical errors of solar concentrators: experimental results

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APPLIED OPTICS 2020年第31期59卷 9861-9877页

作者： Henault, F. Caliot, C. Coquand, M. Defieux, P-H Guillot, E. Univ Grenoble Alpes IPAG CNRS Inst Planetol & Astrophys Grenoble F-38041 Grenoble France PROMES CNRS Proc Mat & Solar Energy Lab 7 Rue Four Solaire F-66120 Font Romeu Odeillo Via France Univ Pau & Pays Adour Lab Math & Leurs Applicat E2S UPPA CNRSLMAP Allee Parc Montaury F-64600 Anglet France

This paper presents the first experimental results obtained with the four cameras backward gazing method for measuring the optomechanical errors of solar concentrating surfaces in operation. It consists in combining the images simultaneously acquired by four cameras placed near the solar receiver in order to reconstruct the slope errors of the mirrors digitally. New algorithms adapted to real acquired images are described. The experiment has been conducted on a sun-tracking heliostat of the experimental solar tower THEWS with canting error measurement accuracy estimated as 0.2 mrad. The main experimental error sources are analyzed, and possible ways of mitigation are proposed, giving reasonable hope of reaching an ultimate measurement accuracy of 0.1 mrad. (C) 2020 Optical Society of America

关键词： image processing image processing algorithms Reconstruction algorithms Solar concentrators Solar energy Stray light

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Reducing the light scattering impact in liquid-crystal-based imaging systems

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APPLIED OPTICS 2020年第16期59卷 4780-4789页

作者： Pusenkova, Anastasiia Galstian, Tigran Univ Laval Dept Phys Engn Phys & Opt Ctr Opt Photon & Lasers 2325 Rue Terrasse Quebec City PQ G1V 0A6 Canada LensVector Inc 6203 San Ignacio AveSuite 110 San Jose CA 95119 USA

We show an experimental method of quantifying the effect of light scattering by liquid crystals (LCs) and then apply rather simple image processing algorithms (Wiener deconvolution and contrast-limited adaptive histogram equalization) to improve the quality of obtained images when using electrically tunable LC lenses (TLCLs). Better contrast and color reproduction have been achieved. We think that this approach will allow the use of thicker LC cells and thus increase the maximum achievable optical power of the TLCL without a noticeable reduction of image quality. This eliminates one of the key limitations for their use in various adaptive imaging applications requiring larger apertures. (C) 2020 Optical Society of America

关键词： Effective refractive index image processing algorithms image quality Imaging systems Liquid crystals Tunable lenses

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Optimizing an LED array for an infrared illumination source using the near field for venous pattern detection

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APPLIED OPTICS 2020年第9期59卷 2858-2865页

作者： Vargas-Trevino, Marciano Gutierrez-Gutierrez, Jaime Rodriguez-Lelis, J. M. Lopez Apreza, Edmundo Univ Autonoma Benito Juarez Oaxaca Escuela Sistemas Biol & Innovac Tecnol Av Univ S-N Ex Hacienda 5 Senores Oaxaca 68120 Oaxaca Mexico Ctr Nacl Invest & Desarrollo Tecnol Grp Tribol Interior Internado Palmira S-N Cuernavaca 62490 Morelos Mexico

Accuracy in vein detection is important for intravenous applications such as venipuncture and other medical procedures. The near-infrared (NIR) imaging technique is used to visualize veins based on the difference of absorption of the infrared light by the oxyhemoglobin present in the blood and surrounding tissue. A problem commonly found during the visualization of veins is attributed to the source of light, saturation, low contrast, and dispersion, which are causes of inhomogeneous illumination. In this work, the design and implementation of a light source with LEDs in the range of 750-860 nm are presented. To obtain the design, a numerical simulation was made using the near-field diffraction theory to obtain homogeneous illumination at 40 cm of the sample, with a radial arrangement of three concentric LED rings. With the developed light source, an experimental scheme for the acquisition of vein patterns was implemented. Using a basic algorithm for the identification of intravenous patterns, a prototype was obtained that we believe can be used in intravenous applications and other medical procedures. (C) 2020 Optical Society of America

关键词： Diffraction theory Fresnel diffraction image processing algorithms image quality Infrared radiation Numerical simulation

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Method to eliminate thermal disturbance errors in digital image correlation measurement based on projection speckle

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APPLIED OPTICS 2020年第33期59卷 10474-10482页

作者： Wang, Huanqing Wang, Yonghong Zhu, Yilei Sun, Fangyuan Wu, Shuangle Zhao, Qihan Hefei Univ Technol Sch Instrument Sci & Optoelect Engn Hefei 230009 Peoples R China

Digital image correlation (DIC) technology is an optical measurement method of material strain displacement based on visible light illumination. With the increasing application of DIC technology in the field of high-temperature measurement, however, the effect of thermal disturbance on measurement accuracy becomes more and more serious. To solve this problem, a method to eliminate thermal disturbance in material measurements based on projection speckle is proposed. First, the gray surface information of two different colors is assigned to the surface of the test piece by artificial splashing and projector projection. The pictures are collected using a color camera, and the channels are separated for each frame of the picture. After that, the displacement field recorded by different channels can be obtained by DIC calculation so the thermal disturbance error can be separated from the real displacement and eliminated. Subsequently, an experimental system is built. Finally, the corrected results are compared with the true displacement value of the stage. The results show that the two sets of values are highly consistent, which verifies the feasibility and accuracy of the proposed method. (C) 2020 Optical Society of America

关键词： Digital image correlation image processing image processing algorithms Optical imaging Speckle patterns Visible light

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Detection of visual defects on rotationally symmetric objects

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JOURNAL OF THE OPTICAL SOCIETY OF AMERICA A-OPTICS image SCIENCE AND VISION 2020年第10期37卷 1583-1594页

作者： Smid, Petr Havranek, Vitezslav Ivanov, Georgi Palacky Univ FZU Inst Phys Joint Lab Opt Czech Acad Sci 17 Listopadu 12 Olomouc 77146 Czech Republic Acad Sci Czech Republ Inst Phys 17 Listopadu 12 Olomouc 77146 Czech Republic Palacky Univ Joint Lab Opt 17 Listopadu 12 Olomouc 77146 Czech Republic Palacky Univ Olomouc Inst Phys Acad Sci Czech Republ Fac Sci 17 Listopadu 12 Olomouc 77146 Czech Republic

The paper describes a method using digital image processing in the detection of vaguely defined visual defects on objects symmetric with respect to a rotation axis. Automotive wheels and hubcaps, fans, turbines, symmetrical ceramic goods, merchandise, etc., are examples of such objects. The method uses the object's surface symmetry to identify areas that do not meet the requirement for the symmetry. The method is based on the brightness comparison of areas of the object's surface under test corresponding to each other with respect to the object's rotational symmetry. The area containing a defect is located through the difference between its brightness and average brightness of the all symmetric areas. The reliability of the method requires opaque and not too broken surfaces with solitary defects that do not overlap when the object is rotated. The method is advantageous for larger defects. Minimum defect size is limited by segmentation of the object and its production tolerances. Uniform illumination is another prerequisite for the reliable detection of the defects. This work focuses on testing the method and determination of the optimum brightness difference characterizing the defect. Next, limitations of the method are analyzed, especially the relationship between the uncertainty of the object shape, the camera resolution, and the minimum size of the detected defect. (C) 2020 Optical Society of America

关键词： Digital image processing Holographic interferometry image processing algorithms Laser beams LED lenses Phase shift

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Adaptive exposure control for image-based visual-servo systems using local gradient information

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JOURNAL OF THE OPTICAL SOCIETY OF AMERICA A-OPTICS image SCIENCE AND VISION 2020年第1期37卷 56-62页

作者： Ding, Zhushun Chen, Xin Jiang, Zhe Tan, Cheng Natl Univ Def Technol Dept Aerospace & Engn Changsha 410073 Peoples R China Beijing Inst Aerosp Control Devices Beijing 100039 Peoples R China

We present anew method for automatic adjustment of camera exposure time for visual-servo systems. The proposed method can improve the robustness of image processing in a high-dynamic-range environment. In this paper, we evaluate an appropriate exposure time by computing the local gradient information of a target area, allowing a camera to capture images without losing target features under artificially adjusted illumination conditions. To validate the advantage of the proposed method, an evaluation is made using an off-the-shelf visual-servo system with a machine vision camera. The experimental results demonstrate the effectiveness of our method, which improves the performance of the target recognition algorithm. (C) 2019 Optical Society of America

关键词： image metrics image processing image processing algorithms image quality Liquid crystals Machine vision

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Classification of maize leaf diseases based on hyperspectral imaging technology

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JOURNAL OF OPTICAL TECHNOLOGY 2020年第4期87卷 212-217页

作者： Xu, Jing Miao, Teng Zhou, Yuncheng Xiao, Yang Deng, Hanbing Song, Ping Song, Kai Shenyang Agr Univ Coll Informat & Elect Engn Shenyang 110866 Peoples R China Shenyang Ligong Univ Shenyang 110159 Peoples R China

Curvularia lunata and Aureobasidium zeae are the main leaf diseases of maize in Northeast China. These two diseases are similar and difficult to distinguish. In order to diagnose diseases correctly, a diagnostic method based on hyperspectral imaging technology for Curvularia lunata and Aureobasidium zeae was proposed. The experimental leaves were inoculated in vivo, and a hyperspectral imaging system was used to collect hyperspectral image data of leaves with Curvularia lunata, leaves with Aureobasidium zeae, and normal leaves in the near-infrared band. By analyzing the spectral characteristics of chlorotic spots and normal leaves, it is found that there is a significant difference in the spectral information between chlorotic spots and normal leaves. Then, by means of confidence interval estimation and significance testing, the characteristic bands of Curvularia lunata and Aureobasidium zeae can be distinguished. Finally, the classification model of the support vector machine is established based on the characteristic bands. The results show that the 10 characteristic bands of 412.7, 416.3, 421.2, 465.1, 484.8, 580.9, 615, 640.5, 676.2, and 880.8 nm can be used to distinguish between the spectral characteristics of Curvularia lunata and Aureobasidiurn zeae , and the support vector machine classification model established by the above band is used for 288 samples. The accuracy rate was 96.7%. These results provide a theoretical basis and technical method for rapid and nondestructive diagnosis of Curvularia lunata and Aureobasidiurn zeae. (C) 2020 Optical Society of America

关键词： Absorption spectroscopy Hyperspectral imaging image processing algorithms Multispectral imaging Spectral imaging Spectroscopy

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Advanced Infrared Technology and Applications 2020: introduction to the feature issue

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APPLIED OPTICS 2020年第17期59卷 AIT1-AIT6页

作者： Strojnik, Marija D'Acunto, Mario Rogalski, Antoni Infrared Grp Opt Res Ctr AP 1-948 Leon 37000 Gto Mexico CNR Inst Biophys Via G Moruzzi 1 I-56124 Pisa Italy Mil Univ Technol Inst Appl Phys 2 Kaliskiego Str PL-00908 Warsaw Poland

The 2020 edition of the Applied Optics (AO) special issue on advanced infrared technology and applications (AITA) collects significantly expanded refereed papers presented at the conference of the same name, held in Florence, Italy, 16-19 September 2019. All authors who participated at the conference were contacted and invited to contribute to this special issue. The issue also was expanded to include contributions from other practitioners of IR through direct contact and a call for papers published inAO. (C) 2020 Optical Society of America

关键词： Fourier transform infrared spectroscopy image metrics image processing algorithms Metrological instrumentation Scanning electron microscopy Single mode fibers

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