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Advanced video extensometer for non-contact, real-time, high-accuracy strain measurement

OPTICS EXPRESS 2016年第17期24卷 19082-19093页

作者： Pan, Bing Tian, Long Beihang Univ Inst Solid Mech Beijing 100191 Peoples R China

We developed an advanced video extensometer for non-contact, real-time, high-accuracy strain measurement in material testing. In the established video extensometer, a "near perfect and ultra-stable" imaging system, combining the idea of active imaging with a high-quality bilateral telecentric lens, is constructed to acquire high-fidelity video images of the test sample surface, which is invariant to ambient lighting changes and small out-of-plane motions occurred between the object surface and image plane. In addition, an efficient and accurate inverse compositional Gauss-Newton algorithm incorporating a temporal initial guess transfer scheme and a high-accuracy interpolation method is employed to achieve real-time, high-accuracy displacement tracking with negligible bias error. Tensile tests of an aluminum sample and a carbon fiber filament sample were performed to demonstrate the efficiency, repeatability and accuracy of the developed advanced video extensometer. The results indicate that longitudinal and transversal strains can be estimated and plotted at a rate of 117 fps and with a maximum strain error less than 30 microstrains. (C) 2016 Optical Society of America

关键词： Digital image processing image processing algorithms image registration Optical imaging Speckle imaging Strain measurement

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Demonstration of a multichannel, multiresolution imaging system

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APPLIED OPTICS 2013年第24期52卷 6081-6089页

作者： Belay, Gebirie Y. Ottevaere, Heidi Meuret, Youri Vervaeke, Michael Van Erps, Jurgen Thienpont, Hugo Vrije Univ Brussel Dept Appl Phys & Photon TONA Fac Engn Brussels Photon Team B PHOT B-1050 Brussels Belgium

In conventional multichannel imaging systems, all channels have similar imaging properties [field-of-view (FOV) and angular resolution]. In our approach, channels are designed to have different imaging properties which add multiresolution capability to the system. We have experimentally demonstrated, for the first time to our knowledge, a three-channel imaging system which simultaneously captures multiple images having different magnifications and FOVs on an image sensor. Each channel consists of four aspherical lens surfaces fabricated from four PMMA plates by ultraprecision diamond tooling and of a baffle made from a titanium (Ti) and aluminum (Al) based metal alloy. The integrated imaging system is able to record a FOV of 7.6 degrees with the first channel and 73 degrees with the third channel while having a magnification ratio of about 6 between them. The experimental and simulation results, specifically the FOV and magnification ratios, are comparable, and this paves a way for low-cost, compact imaging systems which can embed smart imaging functionalities. (c) 2013 Optical Society of America

关键词： image processing image processing algorithms image quality Imaging systems Medical imaging Optical design

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Design and demonstration of a six-channel multiresolution imaging system

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APPLIED OPTICS 2022年第10期61卷 2683-2689页

作者： Belay, Gebirie Yizengaw Bollhorst, Rolf Vervaeke, Michael Thienpont, Hugo Van Erps, Juergen Vrije Univ Brussel & Flanders Make Fac Engn Dept Appl Phys & Photon TONA Brussels Photon B PHOT Pleinlaan 2 B-1050 Brussels Belgium Imaging Source Europe GmbH Uberseetor 18 D-28217 Bremen Germany

Multichannel imaging systems consist of multiple channels that have different imaging characteristics (fields-of-view and angular resolutions). We design and demonstrate a six-channel multiresolution imaging system that can achieve a relative magnification ratio of up to 10 times between the channels and, at the same time, result in different depths-of-field. The imaging system consists of two double-sided lens arrays made of PMMA material, a baffle to eliminate possible cross talk between neighboring channels, and a Sony full-frame image sensor. The imaging system was tested by capturing images of stationary and moving objects. The acquired images exhibit different resolutions, fields-of-view, and levels of blur proving our concept. (C) 2022 Optica Publishing Group

关键词： image processing algorithms image quality Imaging systems Lens arrays Medical imaging Three dimensional imaging

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Restoring a silhouette of the hand in the problem of recognizing gestures by adaptive morphological filtering of a binary image

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JOURNAL OF OPTICAL TECHNOLOGY 2013年第11期80卷 685-690页

作者： Malashin, R. O. Lutsiv, V. R. OAO SI Vavilov State Opt Inst St Petersburg Russia

algorithms are presented for the adaptive processing of binary images of silhouettes of the human hand obtained by means of color-brightness filters. These algorithms are based on the use of a combination of elementary morphological operations that take into account the direction of the fingers. algorithms are presented for removing noise on binary images that are adapted to the result of the operation of a color filter, and a method is presented for filling internal contours of a silhouette of the hand in order to remove grouped marking errors. The experimental results show that the proposed image-processing method increases the probability of successful detection, tracking of the hand, and recognition of gestures. (C) 2014 Optical Society of America.

关键词： algorithms Color spaces image processing image processing algorithms Imaging noise Metrological instrumentation

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Multidispersed bubble-size measurements by interferometric particle imaging at scattering angles of 90° and 45°

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APPLIED OPTICS 2018年第36期57卷 10496-10504页

作者： Zhang, Hongxia Wang, Xiaolei Sun, Jinlu Jia, Dagong Liu, Tiegen Tianjin Univ Coll Precis Instrument & Optoelect Engn Tianjin 300072 Peoples R China Tianjin Univ Key Lab Optoelect Informat Technol Minist Educ Tianjin 300072 Peoples R China

Measurements of multidispersed bubble diameter are important in hydraulics, biology, and other such fields. Interferometric particle imaging (IPI) systems are used to measure the bubble diameter. In geometric approximation, the scattering angle cannot be greater than 2 arccos m. We propose a universal method for calculating the bubble diameter at wide scattering angles and use an IPI system to measure the bubble-size distribution at 90 degrees and 45 degrees. The particle size distributions measured at two angles are consistent with each other. The results of this study indicate that this method is suitable for measuring the bubble-size distribution. (C) 2018 Optical Society of America

关键词： Fourier transforms High power lasers image processing algorithms Particle scattering Scattering Spatial frequency

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Automatic production of synthetic labelled OCT images using an active shape model

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IET image processing 2020年第15期14卷 3812-3818页

作者： Danesh, Hajar Maghooli, Keivan Dehghani, Alireza Kafieh, Rahele Islamic Azad Univ Sci & Res Branch Dept Biomed Engn Tehran Iran Isfahan Univ Med Sci Med Image & Signal Proc Res Ctr Sch Adv Technol Med Esfahan Iran Isfahan Univ Med Sci Sch Med Dept Ophthalmol Esfahan Iran

Limited labelled data is a challenge in the field of medical imaging and the need for a large number of them is paramount for the training of machine learning algorithms, as well as measuring the performance of image processing algorithms. The purpose of this study is to construct synthetic and labelled optical coherence tomography (OCT) data to solve the problems of having access to accurately labelled data and evaluating the processing algorithms. In this study, a modified active shape model is used which considers the anatomical features of available images such as the number and thickness of the layers as well as their associated brightness, the location of retinal blood vessels and shadow information with respect to speckle noise. The algorithm is also able to provide different data sets with the varying noise level. The validity of the proposed method for the synthesis of retinal images is measured by two methods (qualitative assessment and quantitative analysis).

关键词： blood vessels biomedical optical imaging optical tomography image segmentation image processing medical image processing learning (artificial intelligence) eye speckle modified active shape model available images retinal blood vessels retinal images automatic production synthetic labelled OCT images medical imaging machine learning algorithms image processing algorithms synthetic coherence tomography labelled optical coherence tomography accurately labelled data

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Automatic glaucoma classification using color fundus images based on convolutional neural networks and transfer learning

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BIOMEDICAL OPTICS EXPRESS 2019年第2期10卷 892-913页

作者： Gomez-Valverde, Juan J. Anton, Alfonso Fatti, Gianluca Liefers, Bart Herranz, Alejandra Santos, Andres Sanchez, Clara, I Ledesma-Carbay, Maria J. Univ Politecn Madrid Biomed Image Technol Lab BIT ETSI Telecomunicac E-28040 Madrid Spain Biomed Res Ctr Bioengn Biomat & Nanomed CIBER BBN Madrid Spain Parc Salut Mar Barcelona Spain Univ Int Catalunya Barcelona Spain Inst Catala Retina Barcelona Spain Radboud Univ Nijmegen Dept Radiol & Nucl Med Diagnost Image Anal Grp Med Ctr Nijmegen Netherlands

Glaucoma detection in color fundus images is a challenging task that requires expertise and years of practice. In this study we exploited the application of different Convolutional Neural Networks (CNN) schemes to show the influence in the performance of relevant factors like the data set size, the architecture and the use of transfer learning vs newly defined architectures. We also compared the performance of the CNN based system with respect to human evaluators and explored the influence of the integration of images and data collected from the clinical history of the patients. We accomplished the best performance using a transfer learning scheme with VGG19 achieving an AUC of 0.94 with sensitivity and specificity ratios similar to the expert evaluators of the study. The experimental results using three different data sets with 2313 images indicate that this solution can be a valuable option for the design of a computer aid system for the detection of glaucoma in large-scale screening programs. (C) 2019 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

关键词： image processing algorithms image quality assessment Medical image processing Medical imaging Retinal ganglion cells Retinal nerve fiber layer

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MicroHikari3D: an automated DIY digital microscopy platform with deep learning capabilities

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BIOMEDICAL OPTICS EXPRESS 2021年第11期12卷 7223-7243页

作者： Salido, J. Toledano, P. Vallez, N. Deniz, O. Ruiz-santaquiteria, J. Cristobal, G. Bueno, G. Univ Castilla La Mancha VISILAB Grp Ciudad Real 13005 Spain CSIC Inst Opt Serrano 121 Madrid Spain

A microscope is an essential tool in biosciences and production quality laboratories for unveiling the secrets of microworlds. This paper describes the development of MicroHikari3D, an affordable DIY optical microscopy platform with automated sample positioning, autofocus and several illumination modalities to provide a high-quality flexible microscopy tool for labs with a short budget. This proposed optical microscope design aims to achieve high customization capabilities to allow whole 2D slide imaging and observation of 3D live specimens. The MicroHikari3D motion control system is based on the entry level 3D printer kit Tronxy X1 controlled from a server running in a Raspberry Pi 4. The server provides services to a client mobile app for video/image acquisition, processing, and a high level classification task by applying deep learning models.

关键词： Digital image processing image processing algorithms image quality Near field scanning optical microscopy Optical microscopy Three dimensional imaging

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Oblique astigmatism and field curvature measured with light-field imaging

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APPLIED OPTICS 2020年第31期59卷 9710-9714页

作者： Ferreira, Flavio P. Sousa, Marco A. Duarte, Moises A. S. Bret, Boris P. J. Nunes-Pereira, Eduardo J. Univ Minho Ctr Fis Univ Minho & Porto Campus Gualtar P-4710057 Braga Portugal Bosch Secur Syst Sistemas Seguranca SA Estr Nacl 109 IC 1 P-3880728 Aveiro Portugal Bosch Car Multimedia Portugal SA Rua Max Grunding 35 P-4705820 Braga Portugal Univ Minho Dept Fis Campus Gualtar P-4710057 Braga Portugal

The testing of astigmatism and field curvature of an optical system with light-field imaging is proposed. The method consists in measuring the depth map, obtained with a plenoptic camera, of the image of a test pattern formed by the optical system. To demonstrate the accuracy of the method, the virtual image formed by a piano-convex lens was tested. The resulting depth map was compared with the sagittal and tangential foci distances calculated with the Coddington theory. The proposed method could be applied to the quality testing of ocular optics, including eyeglasses, eyepieces, virtual reality goggles, and augmented reality devices. (C) 2020 Optical Society of America

关键词： Augmented reality image processing algorithms Optical aberrations Optical design Optical testing Virtual reality

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image-free real-time 3-D tracking of a fast-moving object using dual-pixel detection

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OPTICS LETTERS 2020年第17期45卷 4734-4737页

作者： Deng, Qiwen Zhang, Zibang Zhong, Jingang Jinan Univ Dept Optoelect Engn Guangzhou 510632 Peoples R China

Real-time 3-D tracking of a fast-moving object has found important applications in industry, traffic control, sports, biomedicine, defense, etc. However, it is difficult to adopt typical image-based object tracking systems in a fast-moving object tracking in real time and for a long duration, because reliable and robust image processing and analysis algorithms are often computationally exhausted, and limited storage and bandwidth can hardly fulfill the great demand of high-speed photography. Here we report an image-free 3-D tracking approach. The approach uses only two single-pixel detectors and a high-speed spatial light modulator for data acquisition. By illuminating the target moving object with six single-period Fourier basis patterns, the approach is able to analytically calculate the position of the object with the corresponding single-pixel measurements. The approach is low-cost, and data- and computation-efficient. We experimentally demonstrate that the proposed approach can detect and track a fast-moving object at a frame rate of 1666 frames per second by using a 10,000 Hz digital micromirror device. Benefiting from the wide working spectrum of single-pixel detectors, the reported approach might be applicable for hidden fast-moving object tracking. (C) 2020 Optical Society of America

关键词： Digital micromirror devices High speed photography image processing algorithms Spatial frequency Spatial light modulators Structured illumination microscopy

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