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Dual-pixel tracking of the fast-moving target based on window complementary modulation

OPTICS EXPRESS 2022年第22期30卷 39747-39761页

作者： Fu, Sheng Xing, Fei You, Zheng Tsinghua Univ Dept Precis Instrument Beijing 100084 Peoples R China Tsinghua Univ State Key Lab Precis Measurement Technol & Instru Beijing 100084 Peoples R China Tsinghua Univ Beijing Innovat Ctr Future Chips Beijing 100084 Peoples R China

Real-time tracking of fast-moving targets has been utilized in various fields. However, the tracking performance of image-based systems for fast-moving targets is still limited by the huge data throughput and computation. In this study, an image-free target tracking system utilizing a digital micromirror device (DMD) is proposed. The proposed system effectively combines the dual-pixel measurement and windowcomplementary modulation, and the alternating interpolation Kalman filter is implemented to fully use the performance of the DMD and maximize the update rate of the system. The accuracy of the proposed system at the maximum update rate of 22.2 kHz can achieve 0.1 pixels according to the experimental results. Meanwhile, we experimentally demonstrated that the accuracy of the proposed image-free target tracking system is within 0.3 pixels at a maximal velocity of 2 x 10(4) pixel/s at 22.2 kHz by evaluating the performance of the proposed image-free target tracking system when tracking fast-moving targets with different maximal velocity. (c) 2022 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement

关键词： Digital micromirror devices High speed photography image processing algorithms Spatial light modulators Target tracking Temporal resolution

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Height measurement of microbumps using a white-light triangulation method

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APPLIED OPTICS 2022年第8期61卷 2036-2044页

作者： Meng, Fanchang Zhang, Zili Kang, Yanhui Li, Yao Wang, Peng Cui, Chengjun Wang, Shan Zhou, Weihu Chinese Acad Sci Inst Microelect Beijing 100029 Peoples R China Univ Chinese Acad Sci Beijing 100029 Peoples R China Natl Inst Metrol Div Dimens Metrol 18 Beisanhuandonglu Beijing 100029 Peoples R China Sanming Univ Sanming 353004 Fujian Peoples R China

As the electronic interconnection between chips, microbumps are crucial components in advanced packaging for the demand of better performance and higher packaging density. The height and coplanarity of microbumps are critical to ensure the reliability of connections. The poor uniformity in bump height will lead to disconnect or insufficient contact, which will directly result in the failure of the chip's function and a lower yield rate. In this paper, we proposed a height measurement method of microbumps using white-light triangulation combined with geometrical characteristics of bumps. A linear light projection module composed of a lens group and LED light source was set up as well as a high-quality imaging module consisting of a CCD camera and microscope objective group. The projection and imaging model of microbumps illuminated by the light plane at different positions during the scanning process was analyzed. The microbump height is computed from a simple formula based on the geometry of the specimen and the system configuration. The measurement results are compared with that obtained from a commercial optical profiler, and the measurement uncertainty is analyzed in detail. (C) 2022 Optica Publishing Group

关键词： CCD cameras Digital image processing image processing algorithms Phase matching Phase unwrapping White light interferometry

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Lens magnification affects the estimates of refractive error obtained using eccentric infrared photorefraction

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JOURNAL OF THE OPTICAL SOCIETY OF AMERICA A-OPTICS image SCIENCE AND VISION 2018年第6期35卷 908-915页

作者： Bharadwaj, Shrikant R. Bandela, Praveen K. Nilagiri, Vinay Kumar LV Prasad Eye Inst Brien Holden Inst Optometry & Vis Sci Rd 2Banjara Hills Hyderabad 500034 Andhra Prades India LV Prasad Eye Inst Hyderabad Eye Res Fdn Prof Brien Holden Eye Res Ctr Rd 2Banjara Hills Hyderabad 500034 Andhra Prades India

Positive- and negative-powered ophthalmic lenses are used in eccentric infrared photorefraction to calibrate the device, correct the subject's baseline refractive error before an experimental manipulation, or stimulate blur-driven accommodation. Through theoretical modeling of luminance gradients formed across the pupil and empirical measurements of the eye's refractive error using a commercial photorefractor, this study shows that image magnification by positive lenses and image minification by negative lenses under- and overestimates the refractive error, respectively, all independent of image defocus. The impact of image magnification/minification therefore appears non-trivial in experimental paradigms involving ophthalmic lenses to manipulate the eye's optics during photorefraction. (c) 2018 Optical Society of America

关键词： Contact lenses Eye movements image processing algorithms Refractive anomalies Visual accommodation Visual acuity

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Fast centre-surround contrast modification

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IET image processing 2008年第1期2卷 19-34页

作者： Vonikakis, V. Andreadis, I. Gasteratos, A. Democritus Univ Thrace Dept Elect & Comp Engn Elect Lab Sect Elect & Informat Syst Technol GR-67100 Xanthi Greece Democritus Univ Thrace Lab Robot & Automat Sect Prod Syst Dept Prod & Management GR-67100 Xanthi Greece

A new algorithm for fast contrast modification of standard dynamic range (SDR) images (8 bits/ channel) is presented. Its thrust is to enhance the contrast in the under-/over-exposed regions of SDR images, caused by the low dynamic range of the capturing device. It is motivated by the attributes of the shunting centre-surround cells of the human visual system. The main advantage of the proposed algorithm is its O(N) complexity which results in very fast execution, even when executed on a conventional personal computer (0.2 s/frame for a 640 x 480 pixel resolution on a 3 GHz Pentium 4). Thus, it moderately increases the computational burden if it is used as a pre-processing stage for other image processing algorithms. The proposed method is compared with other established algorithms, which can enhance the contrast in the under-/over-exposed regions of SDR images: the multi-scale Retinex with colour rendition, the McCann Retinex (McCann99), the rational mapping function and the automatic colour equalisation. The results obtained by this comparison indicate that the proposed algorithm exhibits at least comparable results in contrast modification tasks to the other algorithms, in significantly reduced execution times.

关键词： image resolution multiscale Retinex colour rendition standard dynamic range images automatic colour equalisation Computer vision and image processing techniques image processing algorithms conventional personal computer centre-surround contrast modification Optical, image and video signal processing image enhancement image colour analysis rational mapping function

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Fast path planning algorithm for large-aperture aspheric optical elements based on minimum object depth and a self-optimized overlap coefficient

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APPLIED OPTICS 2022年第11期61卷 3123-3133页

作者： Wang, Fanyi Yang, Yongying Lou, Weiming Zhejiang Univ Dept Opt Engn State Key Lab Modern Opt Instrumentat 38 Zheda Rd Hangzhou 310027 Peoples R China

In the procedure of surface defects detection of large-aperture aspheric optical elements, it is necessary to scan the surface of the element to achieve full coverage inspection. Since the curvature of the aspherical element is constantly changing from the center to the edge, it is of great difficulty to carry out efficient path planning. In addition, the machine vision system is a microscopic system with limited depth of field, and the sub-aperture imaging of aspherical elements has a visual depth along the object side. When the object depth is greater than the depth of field, out-of-focus blur will generate, so the object depth needs to be as small as possible. In response to these problems, this paper proposes a fast path planning algorithm based on the minimum object depth of a sub-aperture. To ensure minimum object depth, the machine vision system collects images along the normal direction of the sub-aperture plane. To address the problem of the surface curvatures of aspheric elements being different and the overlap coefficient difficult to determine, this paper proposes an image processing based overlap coefficient self-optimization algorithm. When scanning with full coverage of elements, there is only one connected domain in the horizontal projection image of all sub-apertures. According to this premise, the overlap coefficient is optimized through an image processing method to obtain a local optimal path planning strategy. According to the obtained path planning strategy, combining the component parameters and mechanical structure, the mapping matrix of the path planning algorithm transplanted to the detection system is calculated. Through computer programming, automatic sub-aperture acquisition is realized, and the self-edited sub-aperture stitching program is applied to reconstruct the collected sub-apertures. Our algorithm can complete path planning within 5 s, and the experimental results show that the maximum stitching misalignment error of the collecte

关键词： Digital image processing Digital imaging image processing image processing algorithms image quality Optical elements

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Miniaturized omnidirectional flexible side-view endoscope for rapid monitoring of thin tubular biostructures

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BIOMEDICAL OPTICS EXPRESS 2019年第5期10卷 2279-2289页

作者： Paulson, Bjorn Lee, SangHwa Kim, Youngkyu Moon, Youngjin Kim, Jun Ki Asan Med Ctr Biomed Engn Res Ctr Asan Inst Life Sci 88 Olymp Ro 43 Gil Seoul 05505 South Korea Univ Ulsan Coll Med Dept Convergence Med 88 Olymp Ro 43 Gil Seoul 05505 South Korea

Endoscopic imaging allows longitudinal observation of epithelial pathologies in tubular organs throughout the body. However, the imaging and optical diagnosis of tubular biostructures such as small animal models and small pediatric organs require appropriately miniaturized devices. A miniaturized catadioptric flexible side-view endoscope is proposed with omnidirectional field of view (FOV) in the transverse direction and sub-nun-scale feature resolution. The FOV in the longitudinal direction is 50 degrees. images are unwrapped and stitched together to form composite images of the target by two different algorithms, revealing a composite FOV of more than 3.5 cm x 360 degrees. The endoscope is well suited for minimally invasive rapid monitoring of thin tubular organs in pediatric patients, as well as for imaging of small animal disease models at near-cellular resolution. (C) 2019 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

关键词： Brain imaging Gastrointestinal imaging image metrics image processing algorithms image quality Modulation transfer function

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OCT skin image enhancement through attenuation compensation

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APPLIED OPTICS 2012年第21期51卷 4927-4935页

作者： Hojjatoleslami, Ali Avanaki, Mohammad R. N. Univ Kent Sch Biosci Ctr Res & Dev Canterbury CT2 7PD Kent England

The enhancement of optical coherence tomography (OCT) skin images can help dermatologists investigate the morphologic information of the images more effectively. In this paper, we propose an enhancement algorithm with the stages that includes speckle reduction, skin layer detection, and attenuation compensation. A weighted median filter is designed to reduce the level of speckle while preserving the contrast. A novel skin layer detection technique is then applied to outline the main skin layers: stratum corneum, epidermis, and dermis. The skin layer detection algorithm does not make any assumption about the structure of the skin. A model of the light attenuation is then used to estimate the attenuation coefficient of the stratum corneum, epidermis, and dermis layers. The performance of the algorithm has been evaluated qualitatively based on visual evaluation and quantitatively using two no-reference quality metrics: signal-to-noise ratio and contrast-to-noise ratio. The enhancement algorithm is tested on 35 different skin OCT images, which show significant improvements in the quality of the images, especially in the structures at deeper levels. (C) 2012 Optical Society of America

关键词： image processing image processing algorithms Medical image processing Phase modulation Spatial frequency Speckle reduction

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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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Flame spectra-temperature estimation based on a color imaging camera and a spectral reconstruction technique

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APPLIED OPTICS 2014年第28期53卷 6351-6361页

作者： Carlos, Toro N. Luis, Arias P. Torres, Sergio Sbarbaro, Daniel Univ Concepcion Dept Elect Engn Concepcion Chile Univ Concepcion Ctr Opt & Photon Concepcion Chile

In this paper a low-cost, practical pixel-based flame spectrum and temperature estimation system based on flame color images is proposed. A spectral resolution of similar to 0.4 nm is achieved with an optical system formed by a color camera, a linear model, a flame's spectral training data, and a spectral reconstruction procedure. As a proof of concept, the estimated spectra are compared to local measurements performed with a commercial spectrometer. In order to estimate the absolute flame-temperature maps, two radiometric images at different wavelengths are reconstructed and the two-color pyrometry method is applied. Experiments show errors of about 2.0% over the estimated temperature, making this system a practical tool for flame sensing in combustion-process monitoring. (C) 2014 Optical Society of America

关键词： CCD cameras Color imaging image processing algorithms Multispectral imaging Optical components Optical systems

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Autofocus methods based on laser illumination

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OPTICS EXPRESS 2023年第18期31卷 29465-29479页

作者： Hua, Zhijie Zhang, Xu Tu, Dawei Shanghai Univ Sch Mechatron Engn & Automat Shanghai 200444 Peoples R China Huazhong Univ Sci & Technol Wuxi Res Inst Wuxi 214000 Jiangsu Peoples R China

Autofocusing system plays an important role in microscopic measurement. However, natural-image-based autofocus methods encounter difficulties in improving focusing accuracy and robustness due to the diversity of detection objects. In this paper, a high-precision autofocus method with laser illumination was proposed, termed laser split-image autofocus (LSA), which actively endows the detection scene with image features. The common non-learning-based and learning-based methods for LSA were quantitatively analyzed and evaluated. Furthermore, a lightweight comparative framework model for LSA, termed split-image comparison model (SCM), was proposed to further improve the focusing accuracy and robustness, and a realistic split-image dataset of sufficient size was made to train all models. The experiment showed LSA has better focusing performance than natural-image-based method. In addition, SCM has a great improvement in accuracy and robustness compared with previous learning and non-learning methods, with a mean focusing error of 0.317 mu m in complex scenes. Therefore, SCM is more suitable for industrial measurement.(c) 2023 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement

关键词： Fourier transforms image metrics image processing algorithms Laser beams Neural networks Real time imaging

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