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Inverse synthetic aperture ladar autofocus imaging algorithm for micro-vibrating satellites based on two prominent points

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APPLIED OPTICS 2019年第25期58卷 6775-6783页

作者： Song, Zi-Qi Mo, Di Wang, Ning Li, Bing-Chen Shao, Yong-She Tan, Rong-Qing Univ Chinese Acad Sci Sch Elect Elect & Commun Engn Beijing 100049 Peoples R China Chinese Acad Sci Inst Elect Beijing 100190 Peoples R China

As an important imaging method for long-range satellite targets, inverse synthetic aperture ladar (ISAL) has the characteristics of high-resolution imaging and competitive detectability. Since the working wavelength of the ISAL is comparable to the micro-vibrations generated by mechanical moving components of satellites, which will cause image defocusing, motion compensation is of great significance. In this paper, an autofocus algorithm is proposed for estimating and compensating the phase error relating to both translational and rotational micro-vibrations. Comparing with non-parametric algorithms like phase gradient autofocus and parametric algorithms like contrast-based autofocus and entropy-based autofocus, the proposed one, which is based on two prominent points, is especially effective for the rotational phase error oscillating numbers of cycles. Simulations and experiments are conducted to validate the feasibility of the proposed algorithm. (C) 2019 Optical Society of America

关键词： Aperture synthesis image processing algorithms image quality Imaging techniques Power spectral density Synthetic aperture radar

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Interferometric particle imaging of ice particles using a multi-view optical system

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APPLIED OPTICS 2018年第21期57卷 6188-6197页

作者： Talbi, M. Grehan, G. Brunel, M. UMR CNRS 6614 CORIA Ave UnivBP 12 F-76801 St Etienne Du Rouvray France

Interferometric particle imaging enables particle size estimation in a wide range [from 10 mu m to a few millimeters] depending on the optical system design. With a multi-view optical system, it is possible to extract more information about the 3D morphology of the particle. In this study, multi-view interferometric out-of-focus imaging of ice particles is performed in a backward-scattering configuration. It is used to estimate ice particle volume and thus to reduce uncertainty concerning particle size estimation. It is further used to better analyze the presence of nearby particles whose images overlap. (C) 2018 Optical Society of America

关键词： Charge coupled devices Fourier transforms image processing algorithms Shape analysis Speckle patterns Three dimensional measurement

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Automated multimodal spectral histopathology for quantitative diagnosis of residual tumour during basal cell carcinoma surgery

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BIOMEDICAL OPTICS EXPRESS 2017年第12期8卷 5749-5766页

作者： Boitor, Radu Kong, Kenny Shipp, Dustin Varma, Sandeep Koloydenko, Alexey Kulkarni, Kusum Elsheikh, Somaia Schut, Tom Bakker Caspers, Peter Puppels, Gerwin van der Wolf, Martin Sokolova, Elena Nijsten, T. E. C. Salence, Brogan Williams, Hywel Notingher, Ioan Univ Nottingham Sch Phys & Astron Univ Pk Nottingham NG7 2RD England Circle Nottingham Ltd NHS Treatment Ctr Lister Rd Nottingham NG7 2FT England Royal Holloway Univ London Math Dept Egham TW20 OFX Surrey England Nottingham Univ Hosp NHS Trust Dept Pathol QMC CampusDerby Rd Nottingham NG7 2117 England Erasmus Univ Med Ctr Rotterdam Dept Dermatol Rotterdam Netherlands RiverD Int Marconistr 16 NL-3029 AK Rotterdam Netherlands East Surrey Hosp Canada Ave Redhill RH1 5RH Surrey England Nottingham Univ Hosp NHS Trust Ctr Evidence Based Dermatol QMC CampusDerby Rd Nottingham NG7 2UH England

Multimodal spectral histopathology (MSH), an optical technique combining tissue auto-fluorescence (AF) imaging and Raman micro-spectroscopy (RMS), was previously proposed for detection of residual basal cell carcinoma (BCC) at the surface of surgically-resected skin tissue. Here we report the development of a fully-automated prototype instrument based on MSH designed to be used in the clinic and operated by a non-specialist spectroscopy user. The algorithms for the AF image processing and Raman spectroscopy classification had been first optimised on a manually-operated laboratory instrument and then validated on the automated prototype using skin samples from independent patients. We present results on a range of skin samples excised during Mohs micrographic surgery, and demonstrate consistent diagnosis obtained in repeat test measurement, in agreement with the reference histopathology diagnosis. We also show that the prototype instrument can be operated by clinical users (a skin surgeon and a core medical trainee, after only 1-8 hours of training) to obtain consistent results in agreement with histopathology . The development of the new automated prototype and demonstration of inter-instrument transferability of the diagnosis models are important steps on the clinical translation path: it allows the testing of the MSH technology' in a relevant clinical environment in order to evaluate its performance on a sufficiently large number of patients.

关键词： image analysis image processing algorithms Micro Raman spectroscopy Optical coherence tomography Raman microscopy Raman spectroscopy

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Compressive SD-OCT: the application of compressed sensing in spectral domain optical coherence tomography

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OPTICS EXPRESS 2010年第21期18卷 22010-22019页

作者： Liu, Xuan Kang, Jin U. Johns Hopkins Univ Dept Elect & Comp Engn Baltimore MD 21218 USA

We applied compressed sensing (CS) to spectral domain optical coherence tomography (SD OCT) and studied its effectiveness. We tested the CS reconstruction by randomly undersampling the k-space SD OCT signal. We achieved this by applying pseudo-random masks to sample 62.5%, 50%, and 37.5% of the CCD camera pixels. OCT images are reconstructed by solving an optimization problem that minimizes the l(1) norm of a transformed image to enforce sparsity, subject to data consistency constraints. CS could allow an array detector with fewer pixels to reconstruct high resolution OCT images while reducing the total amount of data required to process the images. (C) 2010 Optical Society of America

关键词： High speed imaging image processing image processing algorithms Medical imaging Photoacoustic tomography Spectral domain optical coherence tomography

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Influence of lenslet number on performance of image restoration algorithms for the TOMBO imaging system

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OPTICS EXPRESS 2014年第7期22卷 8298-8308页

作者： Gao, Yuan Dong, Lizhi Yang, Ping Tang, Guomao Xu, Bing Chinese Acad Sci Inst Opt & Elect Lab Adapt Opt Chengdu 610209 Peoples R China Chinese Acad Sci Key Lab Adapt Opt Chengdu 610209 Peoples R China Univ Chinese Acad Sci Beijing 100049 Peoples R China

In this paper the influence of the number of lenslets on the performance of image restoration algorithms for the thin observation module by bound optics (TOMBO) imaging system was investigated, and the lenslet number was optimized to achieve thin system and high imaging performance. Subimages with different numbers of lenslets were generated following the TOMBO observation model, and image restoration algorithms were applied to evaluate the imaging performance of the TOMBO system. The optimal lenslet number was determined via theoretical performance optimization and verified via experimental comparisons of angular resolutions of two TOMBO systems and a conventional single-lens system. (C) 2014 Optical Society of America

关键词： image processing image processing algorithms image quality image quality assessment image restoration Imaging systems

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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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Polarized image near-natural color fusion algorithm for target detection

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APPLIED OPTICS 2022年第6期61卷 1323-1330页

作者： Meng, Jin Cao, Tianxing Peng, Jianyu Wang, Zhida Wang, Shifeng Changchun Univ Sci & Technol Sch Optoelect Engn 7089 Weixing Rd Changchun 130022 Jilin Peoples R China Changchun Univ Sci & Technol Zhongshan Inst Zhongshan Guangdong Peoples R China

In some automatic systems, target detection is a common task, and visible images are common sources of raw data. Researchers have confirmed that polarization information highlights man made targets. We propose an algorithm that fuses polarized and visible images to improve detection accuracy. First, the polarization parameter and visible images are simultaneously converted to the HSV color space. The initial fused image after adjusting the hue and saturation will be transformed into the lab color space. Then, the bisecting k-means algorithm is employed to segment the visible image. The visible and initial images are divided into three types of regions for color transfer in lab color space. Finally, the fused image is transformed back to the RGB color space, and the PolarLITIS data set is applied. The experimental results show that the gradient and contrast of the fused image are improved by 115% and 235.3%, respectively, compared with the visible image, and the final fused image is suitable to view with the naked eye. The proposed algorithm significantly improves accuracy. (C) 2022 Optica Publishing Group

关键词： Camera calibration Color spaces image fusion image processing algorithms Low light levels Polarimetric imaging

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Modified two-dimensional digital image correlation method with capability of merging of data distributed in time

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APPLIED OPTICS 2012年第36期51卷 8641-8655页

作者： Malesa, Marcin Kujawinska, Malgorzata Warsaw Univ Technol Inst Micromech & Photon PL-02525 Warsaw Poland

In this article an analysis of two-dimensional (2D) digital image correlation (DIC) data captured over a long period of time is presented, where the case of a 2D DIC setup is not fixed in the same position between consecutive measurements. An implementation of the data merging procedure is described and a proof of concept is provided using example measurements for both: a numerical model and a physical model. An evaluation of the accuracy of the method and main sources of errors are also presented. The developed method can be used for long-term monitoring of different kinds of objects, which is particularly important for the use of DIC technique in application, e.g., building engineering, building control, or power engineering. (C) 2012 Optical Society of America

关键词： Camera calibration Digital image correlation image processing image processing algorithms Optical sensing Speckle patterns

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Optimization of prism-based stereoscopic imaging systems at the optical design stage with respect to required 3D measurement accuracy

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OPTICS EXPRESS 2020年第17期28卷 24418-24430页

作者： Gorevoy, Alexey, V Machikhin, Alexander S. Khokhlov, Demid D. Batshev, Vladislav, I Russian Acad Sci Lab Acoustoopt Spect Sci & Technol Ctr Unique Instrumentat 15 Butlerova Str Moscow 117342 Russia Bauman Moscow State Tech Univ Dept Radioelect & Laser Technol 5 2 Ya Baumanskaya Str Moscow 105005 Russia

We address the optical design procedure of prism-based stereoscopic imaging systems. Conventional approach includes two sequential stages: selection of the hardware and development of the proper digital image processing algorithms. At each of these stages, specific techniques are applied, which are almost unrelated to each other. The main requirements to the imaging system include only the key parameters and the image quality. Therefore, the insufficient measurement accuracy may be revealed only after the prototype is assembled and tested. In this case, even applying complex time-consuming image processing and calibration procedures does not ensure the necessary precision. A radical solution of this issue is to include the measurement error estimation into the optical design stage. In this research, we discuss a simplified implementation of this approach and demonstrate the capabilities of optical design software for this purpose. We demonstrate the effectiveness of this approach by the analysis and optimization of a prism-based stereoscopic imager with respect to required 3D measurement accuracy. The results are meaningful for the development of 3D imaging techniques for machine vision, endoscopic and measurement systems. (C) 2020 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

关键词： Digital image processing image processing image processing algorithms image quality Imaging systems Three dimensional imaging

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High-accuracy calibration method for an underwater one-mirror galvanometric laser scanner

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OPTICS EXPRESS 2023年第4期31卷 5973-5989页

作者： Li, Xiao Chen, Xingpei Li, Wei Yin, Xiaokang Yuan, Xin'an Chen, Huaiyuan Zhou, Jingyu Ma, Xin China Univ Petr East China Dept Mech & Elect Engn Qingdao 266580 Shandong Peoples R China CUHK Dept Mech & Automat Engn Hong Kong Peoples R China

Three-dimensional (3D) perception of deep-sea targets is the key to autonomous op-eration of underwater equipment (e.g., underwater robots). Underwater one-mir ror galvanometric line-laser scanner has advantages for short-range measurement, but it is difficult to achieve high calibration accuracy due to installation errors and refraction effects. For this reason, in this paper, a high-accuracy refraction-considered and installation-error-independent calibration method is proposed for the vision system. Firstly, to address the difficulty of aligning the incident light plane with the galvanometer shaft, a high-accuracy land-based installation-error-independent model is proposed, which avoids the influence of the installation errors and allows the real shaft axis and the light-plane cluster poses to be calculated using only three light planes. Subsequently, considering the underwater refraction, a 3D model is established for simulating refractive behaviors of the light-plane cluster, and then a par tition-based method is proposed for calibrating the underwater light-plane cluster, which further improves the calibration accuracy of the scanner in underwater measurement scenarios. Finally, a one-mir ror galvanometric laser scanner is developed in the laboratory to verify the calibration accuracy and to perform the 3D measurement experiments of underwater targets. The results show that the calibration accuracy of the proposed land-based installation-error-independent model is improved 2 times more compared with the traditional installation-error-dependent model. Additionally, the measurement accuracy of the scanner for the standard sphere is 11.98 mu m and 12.75 mu m in the air and underwater measurement scenarios, and the two measurements are in good agreement. The above results comprehensively verify the high accuracy of the calibration method proposed in this paper. (c) 2023 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement

关键词： Calibration Cylindrical lenses image processing algorithms Laser scanning Planar lenses Spherical lenses

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