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Objective speckle pattern-based surface roughness measurement using matrix factorization

APPLIED OPTICS 2022年第32期61卷 9674-9684页

作者： Patil, Shanta Hardas Kulkarni, Rishikesh Indian Inst Technol Guwahati Dept Elect & Elect Engn Gauhati Assam India

A method for the measurement of profile parameters of both isotropic and anisotropic surfaces is presented using the objective laser speckle imaging technique. The surface parameters are characterized in terms of a singular value decomposition method-based metric derived from the initial key contributing singular values of the speckle pat-tern. A simulation study is performed with random Gaussian anisotropic surfaces generated as a function of the correlation lengths in both x and y directions. In the experimental demonstration, the proposed method is verified with metallic samples having distinct surface roughness processed through widely used machining operations viz., vertical milling, and grinding. A brief discussion about the extent to which the minimum number of singular values that are sufficient to evaluate the profile parameters in the context of experimental results is provided. The method supports the measurement of profile parameters of higher magnitude in the realm of non-contact topo-graphic measurement techniques. The experimental results substantiate the practical applicability of the proposed method.(c) 2022 Optica Publishing Group

关键词： Digital image correlation Digital image processing image processing algorithms Laser imaging Scanning electron microscopy Surface roughness measurement

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Programmable liquid crystal display based noise reduced dynamic synthetic coded aperture imaging camera (NoRDS-CAIC)

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OPTICS EXPRESS 2020年第4期28卷 5221-5238页

作者： Jiang, Zhilong Yang, Shuwei Huang, Huachuan He, Xiaoliang Kong, Yan Gao, Aihua Liu, Cheng Yan, Keding Wang, Shouyu Jiangnan Univ Sch Sci Computat Opt Lab Wuxi 214122 Jiangsu Peoples R China Xian Technol Univ Sch Optoelect Engn Xian 710032 Shaanxi Peoples R China Xian Technol Univ Sch Elect Informat Engn Xian 710032 Shaanxi Peoples R China Southwest Univ Sci & Technol Minstry Educ Sch Manufacture Sci & Engn Key Lab Testing Technol Mfg Proc Mianyang 621010 Sichuan Peoples R China Nanjing Agr Univ Single Mol Nanometry Lab Sinmolab Nanjing 210095 Jiangsu Peoples R China

Besides traditional lens-based imaging techniques, coded aperture imaging (CAI) can also provide target images but without using any optical lenses, therefore it is another solution in imaging applications. Most CAI methods reconstruct target image only from a single-shot coded image using a fixed coding mask;however, the collected partial information inevitably deteriorates the reconstruction quality. Though multi-exposure CAI methods are designed, these existed algorithms can hardly improve reconstruction signal-to-noise ratio (SNR) and spatial resolution simultaneously;additionally, dynamic coding mask display still requires expensive devices and complicated systems. In order to reconstruct target image with both enhanced spatial resolution and SNR but using cost-effective devices and a simple system, we design a noise reduced dynamic synthetic coded aperture imaging camera (NoRDS-CAIC) in this paper. The NoRDS-CAIC only consists of a programmable liquid crystal display (LCD) and an image recorder, and both of them are integrated with a three-dimensional printed shell with the compact size of 19 cm x 15 cm x 16 cm and controlled by our designed software to automatically realize coding mask display, coded image recording and target image reconstruction. When using the NoRDS-CAIC, the optimized coding mask is first sent to the programmable LCD and displayed, then the corresponding coded image is automatically captured using the image recorder. Next, cycle the above procedures to capture enough coded images with previously known coding masks and measured point spread functions (PSFs), and the target image can be finally reconstructed using our designed NoRDS-CAIC decoding algorithm, which is shown with better noise suppression capability and higher reconstruction resolution compared to other classical CAI algorithms. According to the experimental verifications, the NoRDS-CAIC can reach the high resolution of 99.2 mu m and the high SNR of 19.43 dB, proving that the d

关键词： image processing algorithms Imaging techniques Optical imaging Phase imaging Wave front sensing X ray imaging

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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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Accelerating multi-emitter localization in super-resolution localization microscopy with FPGA-GPU cooperative computation

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OPTICS EXPRESS 2021年第22期29卷 35247-35260页

作者： Gui, Dan Chen, Yunjiu Kuang, Weibing Shang, Mingtao Wang, Zhengxia Huang, Zhen-Li Huazhong Univ Sci & Technol Britton Chance Ctr Sch Engn Sci Wuhan Natl Lab Optoelect Wuhan 430074 Peoples R China Huazhong Univ Sci & Technol Sch Engn Sci MoE Key Lab Biomed Photon Wuhan Natl Lab Optoelect Wuhan 430074 Peoples R China Wuhan Vocat Coll Software & Engn Sch Elect Engn Wuhan 430205 Peoples R China Hainan Univ Sch Comp Sci & Technol Haikou 570228 Hainan Peoples R China Hainan Univ Sch Biomed Engn Key Lab Biomed Engn Hainan Prov Haikou 570228 Hainan Peoples R China

The real-time multi-emitter localization method is essential for advancing high-throughput super-resolution localization microscopy (HT-SRLM). In the past decade, the graphics processing unit (GPU) computation has been dominantly used to accelerate the execution speed of the multi-emitter localization method. However, if HT-SRLM is combined with a scientific complementary metal-oxide-semiconductor (sCMOS) camera working at full frame rate, real-time image processing is still difficult to achieve using this acceleration approach, thus resulting in a massive data storage challenge and even system crash. Here we take advantage of the cooperative acceleration power of field programming gate array (FPGA) computation and GPU computation, and propose a method called HCP-STORM to enable real-time multi-emitter localization. Using simulated images, we verified that HCP-STORM is capable of providing real-time image processing for raw images from a representative Hamamatsu Flash 4 V3 sCMOS camera working at full frame rate (that is, 2048x2048 pixels @ 10 ms exposure time). Using experimental images, we prove that HCP-STORM is 25 times faster than QC-STORM and 295 times faster than ThunderSTORM, with a small but acceptable degradation in image quality. This study shows the potential of FPGA-GPU cooperative computation in accelerating multi-emitter localization, and pushes a significant step toward the maturity of HT-SRLM technology. (C) 2021 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

关键词： High throughput optics image processing image processing algorithms image quality Neural networks Spatial resolution

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Super- resolution reconstruction algorithm for optical- resolution photoacoustic microscopy images based on sparsity and deconvolution

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OPTICS EXPRESS 2023年第1期31卷 598-609页

作者： Zhang, Xi Li, Zhongliang Nan, Nan Wang, Xiangzhao Chinese Acad Sci Shanghai Inst Opt & Fine Mech Lab Informat Opt & Optoelect Technol Shanghai 201800 Peoples R China Univ Chinese Acad Sci Ctr Mat Sci & Optoelect Engn Beijing 100049 Peoples R China

The lateral resolution of the optical-resolution photoacoustic microscopy (OR-PAM) system depends on the focusing diameter of the probe beam. By increasing the numerical aperture (NA) of optical focusing, the lateral resolution of OR-PAM can be improved. However, the increase in NA results in smaller working distances, and the entire imaging system becomes very sensitive to small optical imperfections. The existing deconvolution-based algorithms are limited by the image signal-to-noise ratio when improving the resolution of OR-PAM images. In this paper, a super-resolution reconstruction algorithm for OR-PAM images based on sparsity and deconvolution is proposed. The OR-PAM image is sparsely reconstructed according to the constructed loss function, which utilizes the sparsity of the image to combat the decrease in the resolution. The gradient accelerated Landweber iterative algorithm is used to deconvolve to obtain high-resolution OR-PAM images. Experimental results show that the proposed algorithm can improve the resolution of mouse retinal images by approximately 1.7 times without increasing the NA of the imaging system. In addition, compared to the Richardson-Lucy algorithm, the proposed algorithm can further improve the image resolution and maintain better imaging quality, which provides a foundation for the development of OR-PAM in clinical research. (c) 2022 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement

关键词： Blind deconvolution image processing algorithms image quality Imaging techniques Medical imaging Reconstruction algorithms

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High-precision camera distortion measurements with a "calibration harp"

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JOURNAL OF THE OPTICAL SOCIETY OF AMERICA A-OPTICS image SCIENCE AND VISION 2012年第10期29卷 2134-2143页

作者： Tang, Zhongwei von Gioi, Rafael Grompone Monasse, Pascal Morel, Jean-Michel Univ Minnesota Minneapolis MN 55455 USA Ecole Normale Super Ctr Math & Leurs Applicat F-94230 Cachan France Univ Paris Est Ecole Ponts ParisTech LIGM IMAGINE F-77455 Champs Sur Marne France

This paper addresses the high-precision measurement of the distortion of a digital camera from photographs. Traditionally, this distortion is measured from photographs of a flat pattern that contains aligned elements. Nevertheless, it is nearly impossible to fabricate a very flat pattern and to validate its flatness. This fact limits the attainable measurable precisions. In contrast, it is much easier to obtain physically very precise straight lines by tightly stretching good quality strings on a frame. Taking literally "plumb-line methods," we built a "calibration harp" instead of the classic flat patterns to obtain a high-precision measurement tool, demonstrably reaching 2 /100 pixel precisions. The harp is complemented with the algorithms computing automatically from harp photographs two different and complementary lens distortion measurements. The precision of the method is evaluated on images corrected by state-of-the-art distortion correction algorithms, and by popular software. Three applications are shown: first an objective and reliable measurement of the result of any distortion correction. Second, the harp permits us to control state-of-the art global camera calibration algorithms: it permits us to select the right distortion model, thus avoiding internal compensation errors inherent to these methods. Third, the method replaces manual procedures in other distortion correction methods, makes them fully automatic, and increases their reliability and precision. (c) 2012 Optical Society of America

关键词： Camera calibration Distortion image processing image processing algorithms Remote sensing Three dimensional imaging

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Depth-based defocus map estimation using off-axis apertures

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OPTICS EXPRESS 2015年第17期23卷 21958-21971页

作者： Lee, Eunsung Chae, Eunjung Cheong, Hejin Jeon, Semi Paik, Joonki Chung Ang Univ Grad Sch Adv Imaging Sci Multimedia & Film Image Proc & Intelligent Syst Lab Seoul 156756 South Korea

This paper presents a depth-based defocus map estimation method from a single camera with multiple off-axis apertures. The proposed estimation algorithm consists of two steps: (i) object distance estimation using off-axis apertures and (ii) defocus map estimation based on the object distance. The proposed method can accurately estimate the defocus map using object distances that are well-characterized in a color shift model-based computational camera. Experimental results show that the proposed method outperforms the state-of-the-art defocus estimation methods in the sense of both accuracy and the estimation range. The proposed defocus map estimation method is suitable for multifocusing, refocusing, and extended depth of field (EDoF) systems. (C) 2015 Optical Society of America

关键词： Extended depth of field image enhancement image processing image processing algorithms image registration Imaging systems

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Correction of satellite imagery over mountainous terrain

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APPLIED OPTICS 1998年第18期37卷 4004-4015页

作者： Richter, R German Aerosp Ctr Inst Optoelect D-82234 Wessling Germany

A method for the radiometric correction of satellite imagery over mountainous terrain has been developed to remove atmospheric and topographic effects. The algorithm accounts for horizontally varying atmospheric conditions and also includes the height dependence of the atmospheric radiance and transmittance functions to simulate the simplified properties of a three-dimensional atmosphere. A database has been compiled that contains the results of radiative transfer calculations (atmospheric transmittance, path radiance, direct and diffuse solar flux) for a wide range of weather conditions. A digital elevation model is used to obtain information about surface elevation, slope, and orientation. Based on the Lambertian assumption the surface reflectance in rugged terrain is calculated for the specified atmospheric conditions. Regions with extreme illumination geometries sensitive to BRDF effects can be optionally processed separately. The method is restricted to high spatial resolution satellite sensors with a small swath angle such as the Landsat thematic mapper and Systeme pour l'Observation de la Terre high resolution visible, since some simplifying assumptions were made to reduce the required image processing time. (C) 1998 Optical Society of America.

关键词： Atmospheric correction Atmospheric scattering Atmospheric transmittance Cloud effects image processing algorithms Radiative transfer

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Modeling and optimization of a geometrical calibration procedure for stereoscopic video endoscopes

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JOURNAL OF THE OPTICAL SOCIETY OF AMERICA A-OPTICS image SCIENCE AND VISION 2019年第11期36卷 1871-1882页

作者： Gorevoy, Alexey, V Machikhin, Alexander S. Khokhlov, Demid D. Batshev, Vladislav, I Natl Res Univ Moscow Power Engn Univ Inst Automat & Comp Engn Dept Elect Engn & Introscopy 14 Krasnokazarmennaya St Moscow 111250 Russia Russian Acad Sci Lab Acoustoopt Spect Sci & Technol Ctr Unique Instrumentat 15 Butlerova St Moscow 117342 Russia Bauman Moscow State Tech Univ Dept Lasers & Optoelect Syst 5 2 Ya Baumanskaya St Moscow 105005 Russia

Stereoscopic video endoscopes are widely used for remote visual inspection and precise three-dimensional (3D) measurements in industrial and biomedical applications. The reconstruction of 3D points from the corresponding image points requires a geometrical calibration procedure, the accuracy of which affects the measurement uncertainty. We propose to perform an optimal choice of the calibration technique and the calibration target parameters using a computer simulation at the design stage. The effectiveness of this approach is demonstrated via the design of a self-developed miniature prism-based stereoscopic system. We simulated acquisition of calibration and measurement data using optical design software. The conventional calibration technique, requiring many positions of the flat target with arbitrary displacements and rotations, was compared with another one that uses the translation stage to provide pure translation of the target. We analyzed the impact of the translation uncertainty, the number of positions, the number of targets, and the uncertainty of image point coordinates on the uncertainty of calibration parameters and 3D measurements. We have shown that the second technique could provide acceptable measurement accuracy using only two images. The results of the computer simulation were confirmed experimentally using the prototype of the stereoscopic endoscope. The proposed approach may be used to optimize calibration techniques and reduce the cost of calibration equipment for various stereoscopic measurement systems. (C) 2019 Optical Society of America

关键词： Camera calibration Digital image processing image processing algorithms image quality Optical design software Three dimensional image processing

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Tracking objects outside the line of sight using laser Doppler coherent detection

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OPTICS EXPRESS 2022年第18期30卷 31577-31583页

作者： Lu, Zhenzhong Cao, Yuping Peng, Tao Han, Biao Dong, Qian Xidian Univ Sch Optoeletron Engn Xian 710071 Shaanxi Peoples R China

Based on the laser Doppler coherent detection method, a laser Doppler Non-Line-of Sight imaging technique (LD-NLOS) is proposed to obtain a series of effective information about the detected objects outside the line of sight. According to the analysis of the frequency and light intensity characteristics of the scattered signal, the information of the detected object hidden in the intermediate scattering surface is decoded. Without relying on complicated back-end algorithm processing and expensive experimental detection cost, the proposed LD-NLOS technique can detect the target vibration velocity and stably reconstruct its 2D shape. (C) 2022 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement

关键词： Heterodyne detection image processing algorithms Laser beams Light intensity Single photon avalanche diodes Single photon detectors

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