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Learning Siamese networks for laser vision seam tracking

JOURNAL OF THE OPTICAL SOCIETY OF AMERICA A-OPTICS image SCIENCE AND VISION 2018年第11期35卷 1805-1813页

作者： Zou, Yanbiao Li, Jinchao Chen, Xiangzhi Lan, Rui South China Univ Technol Sch Mech & Automot Engn Guangzhou 510640 Guangdong Peoples R China

To design a stable laser vision seam-tracking system, an advanced weld image processing algorithm based on Siamese networks is investigated and proposed to resist the interference of arc and spatter in the welding process. This specially designed neural network, combined with powerful feature expression capabilities of deep learning, takes two welding images with different sizes as inputs and generates a target confidence map in a single forward pass by using the cross-correlation algorithm. To prevent the error accumulation and model drift, an online update strategy via local cosine similarity is developed. The use of metal inert-gas welding can realize real-time and precious tracking under the condition that the strong arc continuously shields the welding seam feature points. (C) 2018 Optical Society of America.

关键词： image processing image processing algorithms image quality Joint transform correlators Laser beams Laser sensors

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

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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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Three-dimensional measuring technique for surface topography using a light-sectioning microscope

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APPLIED OPTICS 2012年第8期51卷 1162-1170页

作者： Xia, Linglin Chen, Peifeng Wang, Ying Zhou, Le Luo, Xi Huazhong Univ Sci & Technol Sch Optoelect Sci & Engn Wuhan Natl Lab Optoelect Wuhan 430074 Peoples R China Nanchang Univ Sch Software Nanchang 330029 Jiangxi Peoples R China

Three-dimensional (3D) surface topographic analysis, measurement, and assessment techniques have raised great interest not only among researchers but also among industrial users. Many industrial processes and applications are directly influenced by the small-scale roughness of surface finishes. This paper describes the development and implementation of a noncontact, three-dimensional, microtopography measuring system. The instrument is formed by combining a modified light-sectioning microscope subsystem with a computer subsystem. In particular, optical system characteristics of the light-sectioning microscope are investigated, and a textured steel sheet is measured to demonstrate good practical outcomes. Details of measuring processes and image processing algorithms are provided, such as procedures for measurement, image edge extraction, and 3D topography reconstruction. After the 3D topography of the measured surface has been reconstructed, the topography field description parameters are calculated. A standard roughness block was used for calibration of the surface microtopography measuring system. Results obtained showed the measurement method output has good agreement with the actual asperity (unevenness or roughness) of the surface. The computer subsystem is used to process and control asperity measurements and image generation, and for image acquisition and presentation. (C) 2012 Optical Society of America

关键词： image processing algorithms Light scattering Scanning electron microscopy Scanning tunneling microscopy Three dimensional reconstruction White light interferometry

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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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Femtosecond laser micro-machining enabled all-fiber mode selective converter

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OPTICS LETTERS 2019年第24期44卷 5941-5944页

作者： Zhang, Cong Li, Zhuoying Fu, Songnian Tang, Ming Liu, Deming Huazhong Univ Sci & Technol Wuhan Natl Lab Optoelect Wuhan 430074 Peoples R China Huazhong Univ Sci & Technol Sch Opt & Elect Informat Wuhan 430074 Peoples R China

We demonstrate a compact all-fiber mode selective converter enabled by femtosecond laser micro-machining on the few-mode fiber (FMF) facet. By introducing a micro-structure into the FMF core, we can achieve a pi spatial phase difference to the fundamental mode of light to be converted. Theoretical optimization reveals that various high-order modes, including LP11, LP02, and LP21 modes, can be selectively converted by various micro-structures on the FMF facet, with a mode extinction ratio of more than 25 dB and mode coupling efficiency of better than 45% over the C-band. Finally, a proof-of-concept experiment is conducted by inscribing a micro-slot on the two-mode fiber facet for the LP01 to LP11 mode conversion. A micro-slot with a width of 6.7 mu m and a depth of 5.4 mu m is fabricated under the optimal femtosecond laser parameters. A LP01 to LP11 mode conversion with an average insert ion loss of 2.7 dB is realized over the C-band, together with a mode intensity profile correlation efficient of more than 65%. Efficient higher-order mode conversion is feasible with a precise femtosecond laser micro-machining. (C) 2019 Optical Society of America

关键词： Extinction ratios Femtosecond lasers image processing algorithms Mode conversion Spatial light modulators Tunable lasers

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Hemodynamic measurements from individual blood cells in early mammalian embryos with Doppler swept source OCT

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OPTICS LETTERS 2009年第7期34卷 986-988页

作者： Larina, Irina V. Ivers, Steven Syed, Saba Dickinson, Mary E. Larin, Kirill V. Univ Houston Biomed Engn Program Houston TX 77204 USA Baylor Coll Med Houston TX 77584 USA

The most common and lethal birth defects affect the cardiovascular (CV) system. The mouse is a superior model for identifying and understanding mammalian CV birth defects, but there is a great need for tools that can detect early and subtle deficiencies in cardiac function in mouse embryos. We combined swept source optical coherence tomography (SS-OCT) with live mouse embryo culture protocols to generate structural two-dimensional and three-dimensional imaging and hemodynamic measurements in a live 8.5 day embryo just a few hours after the beginning of a heartbeat. Our data show that individual circulating blood cells can be visualized with structural SS-OCT, and using Doppler SS-OCT the velocity of single moving blood cells were measured during different phases of the heartbeat cycle. These results demonstrate that Doppler SS-OCT is an extremely useful tool for structural and hemodynamic analysis at the earliest stages of mammalian blood circulation. (C) 2009 Optical Society of America

关键词： Blood Doppler effect image processing algorithms Optical coherence tomography Swept sources Three dimensional imaging

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Optical coherence tomography-based design for a real-time motion corrected scanning microscope

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OPTICS LETTERS 2023年第14期48卷 3805-3808页

作者： Tucker, Stephen S. Giblin, John T. Kilic, Kivilcim Chen, Anderson Tang, Jianbo Boas, David A. Boston Univ Dept Biomed Engn 44 Cummington Mall Boston MA 02215 USA Southern Univ Sci & Technol Dept Biomed Engn Shenzhen 518055 Guangdong Peoples R China

While two-photon fluorescence microscopy is a powerful platform for the study of functional dynamics in living cells and tissues, the bulk motion inherent to these applications causes distortions. We have designed a motion tracking module based on spectral domain optical coherence tomography which compliments a laser scanning two-photon microscope with real-time corrective feedback. The module can be added to fluorescent imaging microscopes using a single dichroic and without additional contrast agents. We demonstrate that the system can track lateral displacements as large as 10 & mu;m at 5 Hz with latency under 14 ms and propose a scheme to extend the system to 3D correction with the addition of a remote focusing module. We also propose several ways to improve the module's performance by reducing the feedback latency. We anticipate that this design can be adapted to other imaging modalities, enabling the study of samples subject to motion artifacts at higher resolution.& COPY;2023 Optica Publishing Group

关键词： Coherence image processing image processing algorithms Laser scanning Scanning microscopy Spectral domain optical coherence tomography

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Direct period measurement for fiber Bragg grating using an optical imaging technique

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APPLIED OPTICS 2013年第22期52卷 5393-5397页

作者： Ali, M. M. Lim, K. S. Yang, H. Z. Chong, W. Y. Lim, W. S. Ahmad, H. Univ Malaya Fac Sci Dept Phys Photon Res Ctr Kuala Lumpur 50603 Malaysia NW Univ Xian Dept Phys Xian 710069 Shaanxi Peoples R China

This paper proposes an approach based on an optical imaging technique for the period measurement of fiber Bragg gratings (FBG). The simple, direct technique involves a differential interface contrast (DIC) microscope and a high-resolution CCD camera. image processing is performed on the microscope images to obtain low-noise grating profiles and then the grating periods. Adopting a large image sample size in the image processing can reduce uncertainty. During the investigation, FBGs of different grating periods are fabricated by prestraining the photosensitive fibers during the UV-writing process. A good linearity between the measured Bragg wavelengths and grating periods is observed and the measured strain-optics coefficient was found to be in agreement with reported literature. (C) 2013 Optical Society of America

关键词： Digital image processing Effective refractive index image processing image processing algorithms Optical imaging Refractive index

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Wide-band high-resolution synthetic imaging of a segmented large-scaled lightweight diffractive telescope

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OPTICS LETTERS 2020年第7期45卷 1790-1793页

作者： Liu, Yang Xie, Zongliang Ma, Haotong Chu, Junqiu Ma, Xiafei Tan, Yufeng Dun, Liu Bian, Jiang Hu, Hongyi Fan, Bin Qi, Bo Chinese Acad Sci Key Lab Opt Engn Chengdu 610209 Peoples R China Chinese Acad Sci Inst Opt & Elect Chengdu 610209 Peoples R China Univ Chinese Acad Sci Beijing 100039 Peoples R China

In this Letter, we report a segmented large-scaled lightweight diffractive telescope testbed newly built in our laboratory. The telescope, consisting of one 710-mm-diameter element in the center surrounded by eight 352-mm-diameter elements and a smaller eyepiece of achromatic lenses, can realize wide-band high-resolution imaging of 0.55-0.65 mu m. The stitching errors are coarsely corrected by adjusting the motion stage mounted on each element. In particular, an optical synthesis system inserted. behind the eyepiece is designed to compensate the residual tip-tilt-piston errors. We present the experimental imaging result of two stitched elements, which is the first successful experimental verification obtained by a practical segmented diffractive telescope to enhance the resolution. Moreover, spatial modulation diversity technology is used to restore the synthetic image so as to improve its quality and contrast. (C) 2020 Optical Society of America

关键词： Diffractive optical elements image processing algorithms image quality Optical imaging Stochastic gradient descent Stray light

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Visibility-enhanced reconstruction of three-dimensional objects under a heavily scattering medium through combined use of intermediate view reconstruction, multipixel extraction, and histogram equalization methods in the conventional integral imaging system

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APPLIED OPTICS 2011年第28期50卷 5369-5381页

作者： Zhang, Miao Piao, Yongri Kim, Eun-Soo Kwangwoon Univ Dept Elect Engn Display Res Ctr 3D Seoul 139701 South Korea

In this paper, we propose an effective approach for reconstructing visibility-enhanced three-dimensional (3D) objects under the heavily scattering medium of dense fog in the conventional integral imaging system through the combined use of the intermediate view reconstruction (IVR), multipixel extraction (MPE), and histogram equalization (HE) methods. In the proposed system, the limited number of elemental images (EIs) picked up from the 3D objects under the dense fog is increased by as many as required by using the IVR technique. The increased number of EIs is transformed into the sub-images (SIs) in which the resolution of the transformed SIs has been also improved as much as possible with the MPE method. Subsequently, by using the HE algorithm, the histogram of the resolution-enhanced SIs is uniformly redistributed over the entire range of discrete pixel levels of the image in a way that the subimage contrast can be much enhanced. Then, these equalized SIs are converted back into the newly modified EIs, and consequently a visibility-enhanced 3D object image can be reconstructed. Successful experimental results with the test object confirmed the feasibility of the proposed method. (C) 2011 Optical Society of America

关键词： image processing image processing algorithms image quality Imaging techniques Optical devices Three dimensional imaging

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