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Detection of visual defects on rotationally symmetric objects

JOURNAL OF THE OPTICAL SOCIETY OF AMERICA A-OPTICS image SCIENCE AND VISION 2020年第10期37卷 1583-1594页

作者： Smid, Petr Havranek, Vitezslav Ivanov, Georgi Palacky Univ FZU Inst Phys Joint Lab Opt Czech Acad Sci 17 Listopadu 12 Olomouc 77146 Czech Republic Acad Sci Czech Republ Inst Phys 17 Listopadu 12 Olomouc 77146 Czech Republic Palacky Univ Joint Lab Opt 17 Listopadu 12 Olomouc 77146 Czech Republic Palacky Univ Olomouc Inst Phys Acad Sci Czech Republ Fac Sci 17 Listopadu 12 Olomouc 77146 Czech Republic

The paper describes a method using digital image processing in the detection of vaguely defined visual defects on objects symmetric with respect to a rotation axis. Automotive wheels and hubcaps, fans, turbines, symmetrical ceramic goods, merchandise, etc., are examples of such objects. The method uses the object's surface symmetry to identify areas that do not meet the requirement for the symmetry. The method is based on the brightness comparison of areas of the object's surface under test corresponding to each other with respect to the object's rotational symmetry. The area containing a defect is located through the difference between its brightness and average brightness of the all symmetric areas. The reliability of the method requires opaque and not too broken surfaces with solitary defects that do not overlap when the object is rotated. The method is advantageous for larger defects. Minimum defect size is limited by segmentation of the object and its production tolerances. Uniform illumination is another prerequisite for the reliable detection of the defects. This work focuses on testing the method and determination of the optimum brightness difference characterizing the defect. Next, limitations of the method are analyzed, especially the relationship between the uncertainty of the object shape, the camera resolution, and the minimum size of the detected defect. (C) 2020 Optical Society of America

关键词： Digital image processing Holographic interferometry image processing algorithms Laser beams LED lenses Phase shift

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Method to eliminate thermal disturbance errors in digital image correlation measurement based on projection speckle

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APPLIED OPTICS 2020年第33期59卷 10474-10482页

作者： Wang, Huanqing Wang, Yonghong Zhu, Yilei Sun, Fangyuan Wu, Shuangle Zhao, Qihan Hefei Univ Technol Sch Instrument Sci & Optoelect Engn Hefei 230009 Peoples R China

Digital image correlation (DIC) technology is an optical measurement method of material strain displacement based on visible light illumination. With the increasing application of DIC technology in the field of high-temperature measurement, however, the effect of thermal disturbance on measurement accuracy becomes more and more serious. To solve this problem, a method to eliminate thermal disturbance in material measurements based on projection speckle is proposed. First, the gray surface information of two different colors is assigned to the surface of the test piece by artificial splashing and projector projection. The pictures are collected using a color camera, and the channels are separated for each frame of the picture. After that, the displacement field recorded by different channels can be obtained by DIC calculation so the thermal disturbance error can be separated from the real displacement and eliminated. Subsequently, an experimental system is built. Finally, the corrected results are compared with the true displacement value of the stage. The results show that the two sets of values are highly consistent, which verifies the feasibility and accuracy of the proposed method. (C) 2020 Optical Society of America

关键词： Digital image correlation image processing image processing algorithms Optical imaging Speckle patterns Visible light

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Optimizing an LED array for an infrared illumination source using the near field for venous pattern detection

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APPLIED OPTICS 2020年第9期59卷 2858-2865页

作者： Vargas-Trevino, Marciano Gutierrez-Gutierrez, Jaime Rodriguez-Lelis, J. M. Lopez Apreza, Edmundo Univ Autonoma Benito Juarez Oaxaca Escuela Sistemas Biol & Innovac Tecnol Av Univ S-N Ex Hacienda 5 Senores Oaxaca 68120 Oaxaca Mexico Ctr Nacl Invest & Desarrollo Tecnol Grp Tribol Interior Internado Palmira S-N Cuernavaca 62490 Morelos Mexico

Accuracy in vein detection is important for intravenous applications such as venipuncture and other medical procedures. The near-infrared (NIR) imaging technique is used to visualize veins based on the difference of absorption of the infrared light by the oxyhemoglobin present in the blood and surrounding tissue. A problem commonly found during the visualization of veins is attributed to the source of light, saturation, low contrast, and dispersion, which are causes of inhomogeneous illumination. In this work, the design and implementation of a light source with LEDs in the range of 750-860 nm are presented. To obtain the design, a numerical simulation was made using the near-field diffraction theory to obtain homogeneous illumination at 40 cm of the sample, with a radial arrangement of three concentric LED rings. With the developed light source, an experimental scheme for the acquisition of vein patterns was implemented. Using a basic algorithm for the identification of intravenous patterns, a prototype was obtained that we believe can be used in intravenous applications and other medical procedures. (C) 2020 Optical Society of America

关键词： Diffraction theory Fresnel diffraction image processing algorithms image quality Infrared radiation Numerical simulation

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On the development of an effective image acquisition system or diamond quality grading

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APPLIED OPTICS 2018年第33期57卷 9887-9897页

作者： Wang, Wenjing Cai, Lilong Hong Kong Univ Sci & Technol Dept Mech Engn Kowloon Hong Kong Peoples R China

In this paper, an effective diamond image acquisition system is proposed for capturing images of the diamond sample under inspection separately with transmitted and reflected light. The proposed system consists of two parts: a lighting system and an imaging system. The lighting system is a newly designed integrating sphere that can control the light distribution in the image plane and provide uniform illumination to the diamond sample while it is being inspected under white LED lamps with a specific spectral power distribution. The imaging system comprises industrial-grade lenses, cameras, and a sample loading plate. One set of lenses and a camera is installed at the port of the lower hemisphere. This arrangement ensures that all light rays illuminated to the image plane are transmitted light. On die other hand, all light captured by the other set of lenses and a camera installed on the upper hemisphere is reflected light. The proposed design utilizes the ray tracing processing method based on the physical properties of materials and adjusts the parameters of each optical component. When properly designed, the signal-to-noise ratio of captured diamond images is significantly improved, so that imperfections inside the diamond or on its surface can be clearly distinguished. The proposed image acquisition system is cost-effective and compact. The experimental results agree well with the theoretical analysis and verify the effectiveness of the proposed image acquisition system. The proposed system will facilitate, improve, and simplify automated diamond quality grading. (C) 2018 Optical Society of America

关键词： Edge detection image processing image processing algorithms image quality Material properties Optical components

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Reconstruction of three-dimensional chemiluminescence images with a maximum entropy deconvolution algorithm

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APPLIED OPTICS 2012年第11期51卷 1671-1680页

作者： Gosselin, Kathryn R. Renfro, Michael W. Univ Connecticut Dept Mech Engn Storrs CT 06269 USA

Three-dimensional (3D) images of flame emission are reported using a single direction of optical access. A Cassegrain system was designed with narrow depth of field. images from this system are dominated by emission from the focused object plane with defocused contributions from out-of-plane structures. Translation of one mirror in the system allows for scanning the object plane through the flame. images were taken at various depths to create a family of images. Reconstruction of the 3D flame structure was accomplished using a maximum entropy algorithm adapted for use with 3D imaging. Spatial resolution in the direction of imaging is examined using laminar flames with variable offset. (C) 2012 Optical Society of America

关键词： image processing algorithms Laser induced fluorescence Laser velocimetry Signal collection Three dimensional imaging Three dimensional reconstruction

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High-precision algorithms for critical angle refractive index measurement

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APPLIED OPTICS 2019年第22期58卷 6057-6062页

作者： Luo, Yun Guo, Wenping Yu, Long Xia, Min Li, Wei Yang, Kecheng Huazhong Univ Sci & Technol Sch Opt & Elect Informat Wuhan 430074 Hubei Peoples R China

The critical angle method for refractive index measurement has attracted considerable attention. Precisely obtaining the critical angle is vital to the measurement process. Two advanced algorithms capable of improving the resolution of critical angle refractive index measurement systems are demonstrated. It is experimentally verified that the two algorithms improve the measurement resolution and retain linearity in the entire measurement range. The algorithm analyzes the data near the critical angle to achieve high precision, and this approach provides a notable improvement over the traditional algorithm. We perform verification experiments using liquid samples with low concentration differences, and the RI changes of these samples cannot be identified by traditional algorithms. The proposed algorithm is superior to the traditional method, which yields a resolution of less than 10(-5) refractive index unit (RIU). The repeatability test shows that the uncertainty is 10(-5) RIU (99.7% confidence). (C) 2019 Optical Society of America

关键词： algorithms Edge detection image processing algorithms Light intensity Refractive index Surface plasmon resonance

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Cramer-Rao lower bounds on the estimation of the degree of polarization in coherent imaging systems

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JOURNAL OF THE OPTICAL SOCIETY OF AMERICA A-OPTICS image SCIENCE AND VISION 2005年第11期22卷 2532-2541页

作者： Roux, N Goudail, FO Réfrégier, P Ecole Generaliste Ingenieurs Marseille UMR 6133 Fresnel Inst Phys & Image Proc Grp F-13397 Marseille France

We analyze the estimation precision of the parameter of the orthogonal state contrast image (OSCI) under coherent illumination. This parameter represents the degree of polarization of the light if the materials that compose the scene are purely depolarizing. Two different estimation modes are considered, depending on the uniformity of the illumination of the scene. We first determine lower bounds on the estimation precision in both cases by computing the Cramer-Rao lower bounds (CRLBs) for unbiased estimation. This allows us to compare the potential precision that can be reached in each mode. We then consider the estimators based on empirical averaging of the data, and we show that there are cases where they are strongly biased. We thus propose and characterize another estimator based on the natural representation of the OSCI, which is asymptotically unbiased and whose variance is close to the unbiased CRLB. (c) 2005 Optical Society of America.

关键词： Atmospheric turbulence Coherent systems image processing algorithms Laser light Polarimetric imaging Speckle noise

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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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Non-invasive thermal imaging of cardiac remodeling in mice

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BIOMEDICAL OPTICS EXPRESS 2019年第12期10卷 6189-6203页

作者： Brzezinski, Rafael Y. Ovadia-Blechman, Zehava Lewis, Nir Rabin, Neta Zimmer, Yair Levin-Kotler, Lapaz Tepper-Shaihov, Olga Naftali-Shani, Nili Tsoref, Olga Grossman, Ehud Leor, Jonathan Hoffer, Oshrit Tel Aviv Univ Sackler Fac Med IL-6997801 Tel Aviv Israel Tel Aviv Univ Sackler Fac Med Neufeld Cardiac Res Inst Tel Aviv Israel Sheba Med Ctr Leviev Heart Ctr Tamman Cardiovasc Res Inst IL-52621 Tel Hashomer Israel Afeka Tel Aviv Acad Coll Engn Sch Med Engn IL-6910717 Tel Aviv Israel Tel Aviv Univ Dept Ind Engn IL-6997801 Tel Aviv Israel Sheba Med Ctr Internal Med Wing & Hypertens Unit IL-52621 Tel Hashomer Israel Afeka Tel Aviv Acad Coll Engn Sch Elect Engn IL-6910717 Tel Aviv Israel

Thermal infrared imaging has been suggested as a non-invasive alternative to monitor physiological processes and disease. However, the use of this technique to image internal organs, such as the heart, has not yet been investigated. We sought to determine the ability of our novel thermal image-processing algorithm to detect structural and functional changes in a mouse model of hypertension and cardiac remodeling. Twelve mice were randomly assigned to receive either the pro-inflammatory, hypertensive hormone angiotensin-II (2 mg/kg/day, n = 6) or saline (n = 6) infusion for 28 days. We performed weekly blood pressure measurements, together with serial trans-thoracic echocardiography studies and histopathological evaluation of the hearts. Thermal images were captured with a commercially available thermal camera, and images were processed by our novel algorithm which analyzes relative spatial temperature variation across the animal's thorax. We assessed cardiac inflammation by measuring inflammatory cell infiltration through flow cytometry. Angiotensin infusion increased blood pressure together with cardiac hypertrophy and fibrosis. Thermal imaging at day 28 of the experiment detected an increase in the fraction of the skin heated by the heart in angiotensin-treated mice. Thermal image findings were significantly correlated to left ventricular volume and mass parameters seen on echocardiography (r = 0.8, p < 0.01 and r = 0.6, p = 0.07). We also identified distinct changes in the spatial heat profiles of all angiotensin-treated hearts, possibly reflecting remodeling processes in the hypertensive heart. Finally, a machine learning based model using thermal imaging parameters predicted intervention status in 10 out of 11 mice similar to a model using echocardiographic measurements. Our findings suggest, for the first time, that a new thermal image-processing algorithm successfully correlates surface thermography with cardiac structural changes in mice with hypertensive he

关键词： Feature extraction image processing image processing algorithms Magnetic resonance imaging Thermal imaging Thermal infrared imaging

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Adaptive exposure control for image-based visual-servo systems using local gradient information

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JOURNAL OF THE OPTICAL SOCIETY OF AMERICA A-OPTICS image SCIENCE AND VISION 2020年第1期37卷 56-62页

作者： Ding, Zhushun Chen, Xin Jiang, Zhe Tan, Cheng Natl Univ Def Technol Dept Aerospace & Engn Changsha 410073 Peoples R China Beijing Inst Aerosp Control Devices Beijing 100039 Peoples R China

We present anew method for automatic adjustment of camera exposure time for visual-servo systems. The proposed method can improve the robustness of image processing in a high-dynamic-range environment. In this paper, we evaluate an appropriate exposure time by computing the local gradient information of a target area, allowing a camera to capture images without losing target features under artificially adjusted illumination conditions. To validate the advantage of the proposed method, an evaluation is made using an off-the-shelf visual-servo system with a machine vision camera. The experimental results demonstrate the effectiveness of our method, which improves the performance of the target recognition algorithm. (C) 2019 Optical Society of America

关键词： image metrics image processing image processing algorithms image quality Liquid crystals Machine vision

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