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Single-spot two-dimensional displacement measurement based on self-mixing interferometry

OPTICA 2017年第7期4卷 729-735页

作者： Zhu, Kaiyi Guo, Bo Lu, Yueyue Zhang, Shulian Tan, Yidong Tsinghua Univ State Key Lab Precis Measurement Technol & Instru Dept Precis Instrument Beijing 100084 Peoples R China

The simultaneous and independent measurements of in-plane and out-of-plane displacements are significant issues to be solved in research. Here a novel system to realize single-spot two-dimensional (2D) displacement measurement of a noncooperative target is reported. The performance of the system is tested in the displacement measurement of an aluminum target with a rough surface. 2D random movement and 2D movement with different parameters of Lissajous figures are measured by the system. The ranges of the 2D displacement measurement reach 500 mu m and the accuracies reach the submicron scale. The resolutions of the two dimensions are all better than 5 nm. The measurement system is based on laser heterodyne self-mixing interferometry with frequency multiplexing, which has advantages such as noncontact, nondestruction, nanometer-scale resolution and high sensitivity. The method is promising to be applied in 2D deformation tests of materials, 2D rotor vibration measurement, 2D positioning of particles, thermal expansion coefficient measurement, and other applications. (C) 2017 Optical Society of America

关键词： image processing algorithms Laser beams Laser interferometry Laser sensors Speckle interferometry Three dimensional measurement

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Spectral and temporal multiplexing for multispectral fluorescence and reflectance imaging using two color sensors

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OPTICS EXPRESS 2017年第11期25卷 12812-12829页

作者： Dimitriadis, Nikolas Grychtol, Bartlomiej Theuring, Martin Behr, Tobias Sippel, Christian Deliolanis, Nikolaos C. Fraunhofer Inst Mfg Engn & Automat Project Grp Automat Med & Biotechnol Theodor Kutzer Ufer 1-3 D-68167 Mannheim Germany Heidelberg Univ Dept Phys & Astron Neuenheimer Feld 226 D-69120 Heidelberg Germany Heidelberg Univ Med Fac Mannheim Theodor Kutzer Ufer 1-3 D-68167 Mannheim Germany

Fluorescence imaging can reveal functional, anatomical or pathological features of high interest in medical interventions. We present a novel method to record and display in video rate multispectral color and fluorescence images over the visible and near infrared range. The fast acquisition in multiple channels is achieved through a combination of spectral and temporal multiplexing in a system with two standard color sensors. Accurate color reproduction and high fluorescence unmixing performance are experimentally demonstrated with a prototype system in a challenging imaging scenario. Through spectral simulation and optimization we show that the system is sensitive to all dyes emitting in the visible and near infrared region without changing filters and that the SNR of multiple unmixed components can be kept high if parameters are chosen well. We propose a sensitive per-pixel metric of unmixing quality in a single image based on noise propagation and present a method to visualize the high-dimensional data in a 2D graph, where up to three fluorescent components can be distinguished and segmented. (C) 2017 Optical Society of America

关键词： image processing image processing algorithms image quality Imaging systems Imaging techniques Spectroscopy

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Ballistic imaging through an intense scattering medium using a supercontinuum with a roundabout spatial gate

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OPTICS EXPRESS 2017年第17期25卷 20431-20436页

作者： Zheng, Yipeng Tan, Wenjiang Liu, Xiaojing Tong, Junyi Xi An Jiao Tong Univ Key Lab Phys Elect & Devices Sch Elect & Informat Engn Minist EducShannxi Key Lab InformatPhoton Tech Xianning Xilu 28 Xian 710049 Shaanxi Peoples R China Xian Univ Technol Dept Appl Phys Xian 710048 Shaanxi Peoples R China

We propose a new ballistic imaging method that is capable of imaging an object through an intense scattering medium. In this method, a femtosecond supercontinuum and a roundabout spatial gate were used to suppress speckles and filter background noise, respectively. The roundabout spatial gate extracts ballistic light and avoids low- pass spatial filtering to ensure the high resolution of images. The experimental results showed that even when the optical depth of the scattering medium reached 17, the images extracted by the method had improved identifiability and contrast. (C) 2017 Optical Society of America

关键词： Digital image processing image processing algorithms image quality Imaging systems Spatial frequency Speckle patterns

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Microsphere-based super-resolution scanning optical microscope

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OPTICS EXPRESS 2017年第13期25卷 15079-15092页

作者： Huszka, Gergely Yang, Hui Gijs, Martin A. M. Ecole Polytech Fed Lausanne Lab Microsyst CH-1015 Lausanne Switzerland

High-refractive index dielectric microspheres positioned within the field of view of a microscope objective in a dielectric medium can focus the light into a so-called photonic nanojet. A sample placed in such nanojet can be imaged by the objective with super-resolution, i.e. with a resolution beyond the classical diffraction limit. However, when imaging nanostructures on a substrate, the propagation distance of a light wave in the dielectric medium in between the substrate and the microsphere must be small enough to reveal the sample's nanometric features. Therefore, only the central part of an image obtained through a microsphere shows super-resolution details, which are typically similar to 100 nm using white light (peak at lambda = 600 nm). We have performed finite element simulations of the role of this critical distance in the super-resolution effect. Super-resolution imaging of a sample placed beneath the microsphere is only possible within a very restricted central area of -10 mu m(2), where the separation distance between the substrate and the microsphere surface is very small (-1 mu m). To generate super-resolution images over larger areas of the sample, we have fixed a microsphere on a frame attached to the microscope objective, which is automatically scanned over the sample in a step-by-step fashion. This generates a set of image tiles, which are subsequently stitched into a single super-resolution image (with resolution of lambda/4-lambda/5) of a sample area of up to -10(4) mu m(2). Scanning a standard optical microscope objective with microsphere therefore enables super-resolution microscopy over the complete field-of-view of the objective. (C) 2017 Optical Society of America

关键词： image processing image processing algorithms Imaging systems Scanning electron microscopy Scanning tunneling microscopy Structured illumination microscopy

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Fundamental uncertainty limit for speckle displacement measurements

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APPLIED OPTICS 2017年第25期56卷 7013-7019页

作者： Fischer, Andreas Univ Bremen Bremen Inst Metrol Automat & Qual Sci Linzer Str 13 D-28359 Bremen Germany

The basic metrological task in speckle photography is to quantify displacements of speckle patterns, allowing for instance the investigation of the mechanical load and modification of objects with rough surfaces. However, the fundamental limit of the measurement uncertainty due to photon shot noise is unknown. For this reason, the Cramer-Rao bound (CRB) is derived for speckle displacement measurements, representing the squared minimal achievable measurement uncertainty. As result, the CRB for speckle patterns is only two times the CRB for an ideal point light source. Hence, speckle photography is an optimal measurement approach for contactless displacement measurements on rough surfaces. In agreement with a derivation from Heisenberg's uncertainty principle, the CRB depends on the number of detected photons and the diffraction limit of the imaging system described by the speckle size. The theoretical results are verified and validated, demonstrating the capability for displacement measurements with nanometer resolution. (C) 2017 Optical Society of America

关键词： Diffraction limit image processing algorithms Laser triangulation Speckle noise Speckle patterns Speckle photography

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Fitting-free algorithm for efficient quantification of collagen fiber alignment in SHG imaging applications

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BIOMEDICAL OPTICS EXPRESS 2017年第10期8卷 4609-4620页

作者： Hall, Gunnsteinn Liang, Wenxuan Li, Xingde Johns Hopkins Univ Dept Biomed Engn Baltimore MD 21205 USA

Collagen fiber alignment derived from second harmonic generation (SHG) microscopy images can be important for disease diagnostics. image processing algorithms are needed to robustly quantify the alignment in images with high sensitivity and reliability. Fourier transform (FT) magnitude, 2D power spectrum, and image autocorrelation have previously been used to extract fiber information from images by assuming a certain mathematical model (e.g. Gaussian distribution of the fiber-related parameters) and fitting. The fitting process is slow and fails to converge when the data is not Gaussian. Herein we present an efficient constant-time deterministic algorithm which characterizes the symmetricity of the FT magnitude image in terms of a single parameter, named the fiber alignment anisotropy R ranging from 0 (randomized fibers) to 1 (perfect alignment). This represents an important improvement of the technology and may bring us one step closer to utilizing the technology for various applications in real time. In addition, we present a digital image phantom-based framework for characterizing and validating the algorithm, as well as assessing the robustness of the algorithm against different perturbations. (C) 2017 Optical Society of America

关键词： Biological imaging Digital imaging Fourier transforms image processing image processing algorithms Power spectra

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Automated surface inspection for steel products using computer vision approach

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APPLIED OPTICS 2017年第2期56卷 184-192页

作者： Xi, Jiaqi Shentu, Lifeng Hu, Jikang Li, Mian Baosteel Res Inst Dept Automat 885 Fu Jin Rd Shanghai 201900 Peoples R China Shanghai Jiao Tong Univ Univ Michigan Shanghai Jiao Tong Univ Joint Inst Shanghai 200240 Peoples R China

Surface inspection is a critical step in ensuring product quality in the steel-making industry. In order to relieve inspectors of laborious work and improve the consistency of inspection, much effort has been dedicated to the automated inspection using computer vision approaches over the past decades. However, due to non-uniform illumination conditions and similarity between the surface textures and defects, the present methods are usually applicable to very specific cases. In this paper a new framework for surface inspection has been proposed to overcome these limitations. By investigating the image formation process, a quantitative model characterizing the impact of illumination on the image quality is developed, based on which the non-uniform brightness in the image can be effectively removed. Then a simple classifier is designed to identify the defects among the surface textures. The significance of this approach lies in its robustness to illumination changes and wide applicability to different inspection scenarios. The proposed approach has been successfully applied to the real-time surface inspection of round billets in real manufacturing. Implemented on a conventional industrial PC, the algorithm can proceed at 12.5 frames per second with the successful detection rate being over 90% for turned and skinned billets. (C) 2017 Optical Society of America

关键词： Fourier transforms image processing image processing algorithms image quality Machine vision Real time implementation

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Blind multi-frame deconvolution by tangential iterative projections (TIP)

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OPTICS EXPRESS 2017年第26期25卷 32305-32322页

作者： Wilding, Dean Soloviev, Oleg Pozzi, Paolo Vdovin, Gleb Verhaegen, Michel Delft Univ Technol Delft Ctr Syst & Control Mekelweg 2 NL-2628 CD Delft Netherlands ITMO Univ Kronverksky 49 St Petersburg 197101 Russia Flexible Opt BV Polakweg 10-11 NL-2288 GG Rijswijk Netherlands

A methodology for retrieving the unknown object distribution and point-spread functions (PSFs) from a set of images acquired in the presence of temporal phase aberrations is presented in this paper. The method works by finding optimal complimentary linear filters for multi-frame deconvolution. The algorithm uses undemanding computational operations and few a priori, making it simple, fast and robust even at low signal-to-noise ratios. Results of numerical simulations and experimental tests are given as empirical proof, alongside comparisons with other algorithms found in the literature. (C) 2017 Optical Society of America

关键词： Blind deconvolution Diffraction limit Discrete Fourier transforms image processing algorithms Imaging systems Phase retrieval

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Full-reference quality assessment of stereoscopic images by learning binocular visual properties

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APPLIED OPTICS 2017年第29期56卷 8291-8302页

作者： Ma, Jian An, Ping Shen, Liquan Li, Kai Minist Educ Key Lab Adv Displays & Syst Applicat Shanghai 200072 Peoples R China Shanghai Univ Sch Commun & Informat Engn Shanghai 200072 Peoples R China

Stereoscopic imaging technology has been growingly prevalent driven by both the entertainment industry and scientific applications in today's world. But objective quality assessment of stereoscopic images is a challenging task. In this paper, we propose a novel stereoscopic image quality assessment (SIQA) method by jointly considering monocular perception and binocular interaction. As the most significant contribution of this study, binocular perceptual properties of simple and complex cells are considered for full-reference (FR) SIQA. Specifically, the proposed scheme first simulates the receptive fields of simple cells (one class of V1 neurons) using a push-pull combination of receptive fields response, which is used to represent a monocular cue. Further, the receptive fields of complex cells (the other class of V1 neurons) are simulated by using binocular energy response and binocular rivalry response, which are used to represent a binocular cue. Subsequently, various quality-aware features are extracted from the response of area V1 by calculating the self-weighted histogram of the local binary pattern on four types of feature maps of similarity measurement that will change in the presence of distortions. Finally, kernel ridge regression is used to simulate a nonlinear relationship between the quality-aware features and objective quality scores. The performance of our method is evaluated over popular stereoscopic image databases and shown to be competitive with the state-of-the-art FR SIQA algorithms. (C) 2017 Optical Society of America

关键词： image processing algorithms image quality image quality assessment Signal processing Three dimensional image processing Three dimensional imaging

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Continuous digital zooming using local self-similarity-based super-resolution for an asymmetric dual camera system

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JOURNAL OF THE OPTICAL SOCIETY OF AMERICA A-OPTICS image SCIENCE AND VISION 2017年第6期34卷 991-1003页

作者： Moon, Byeongho Yu, Soohwan Ko, Seungyong Park, Seonhee Paik, Joonki Chung Ang Univ Dept Image 84 Heukseok Ro Seoul 06975 South Korea

This paper presents a digital zooming method using a super-resolution (SR) algorithm based on the local self-similarity between the wide-and tele-view images acquired by an asymmetric dual camera system. The proposed SR algorithm consists of four steps: (i) registration of an optically zoomed image to the wide-view image, (ii) restoration of the central region of the zoomed wide-view image, (iii) restoration of the boundary region of the zoomed wideview image, and (iv) fusion of the results from steps (ii) and (iii). Since an asymmetric dual camera system acquires different-resolution images on the same scene due to the different optical specifications, the proposed method can restore the low-resolution wide-view image using the ideal high-frequency component estimated from the optically zoomed image. Experimental results demonstrate that the proposed method can provide significantly improved high-resolution wide-view images compared to existing single-image- based SR methods. (C) 2017 Optical Society of America

关键词： Digital image processing image processing image processing algorithms image quality image restoration Point spread function

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