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Investigations on the potential application of machine vision lenses for depth measurement by exploiting chromatic aberrations

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Measurement: Sensors 2022年 23卷

作者： Horn, Robin Rosenberger, Maik Golomoz, Andrei Fütterer, Richard Dittrich, Paul-Gerald Nestler, Rico Notni, Gunther Technische Universität Ilmenau Department of Mechanical Engineering Group for Quality Assurance and Industrial Image Processing Ilmenau Germany Fraunhofer Institute for Applied Optics and Precision Engineering Jena Germany

Chromatic (spectral) aberrations are image imperfections that are disadvantageous for standard image processing tasks and are typically compensated through the application of different types of glass during lens design. The longitudinal chromatic aberration causes a relative unsharpness over different spectral channels. Since this error is corrected in most multi-chromatic lenses, this paper investigates to which extent the shift of the focal planes in a standard lens can be used specifically for image processing applications. Theoretical investigations of the longitudinal chromatic aberration are carried out. Based on this, conditions and a method to generate a 3D depth reconstruction out of different spectral channels are presented. © 2022 The Authors

关键词： Aberrations

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Role of microfluctuations in accommodation: a novel approach to reduce non-accommodative noise

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International Journal of Ophthalmology(English edition) 2019年第4期12卷 681-684页

作者： Núria Lupón Joan Gispets Genis Cardona Alba Tàpia Hector Abril Department of Optics and Optometry Universitat Politècnica de Catalunya Applied Optics and Image Processing Research Group Universitat Politècnica de Catalunya

Accommodative response and its possible role in myopia development has been explored through the study of the microfluctuations(MFs) of accommodation, which are commonly divided in high(1.0 to 2.3 Hz) and low(0.1 to 0.6 Hz) frequency components. Previous research efforts have evidenced that a certain percentage of the amplitude of MFs seems not to originate in the accommodative response. We aimed to develop and test a new approach to reduce this non-accommodative noise. For this purpose, ten healthy participants were enrolled to determine the difference between the amplitude of MFs at near and distance for each range of frequencies, which was defined as the relative amplitude of MFs. The findings support the exploration of the relative rather than absolute values of the amplitude of MFs to better understand the contribution of both accommodative and non-accommodative factors to MFs.

关键词： accommodation cycloplegia microfluctuations myopia photorefraction

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1D quasi-bound states in the continuum with large operation bandwidth in theω~k space for nonlinear optical applications

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Photonics research 2022年第7期10卷 1575-1581页

作者： KAILI SUN HUI JIANG DMITRY ABYKOV VIEN VAN URIEL LEVY YANGJIAN CAI ZHANGHUA HAN Shandong Provincial Key Laboratory of Optics and Photonic Devices Center of Light Manipulation and ApplicationsSchool of Physics and ElectronicsShandong Normal UniversityJinan 250358China Image Processing Systems Institute—Branch of the Federal Scientific Research Centre“Crystallography and Photonics”of Russian Academy of Sciences Samara 443001Russia Department of Electrical and Computer Engineering University of AlbertaEdmontonAlberta T6G 2V4Canada Department of Applied Physics and Center for Nanoscience and NanotechnologyThe Hebrew University of JerusalemJerusalemIsrael

The phenomenon of bound state in the continuum(BIC)with an infinite quality factor and lifetime has emerged in recent years in photonics as a new tool to manipulate light-matter ***,most of the investigated structures only support BIC resonances at very few discrete points in theω~k *** when the BIC is switched to a quasi-BIC(QBIC)resonance through perturbation,its frequency will still be located within a narrow spectral band close to that of the original BIC,restricting their applications in many fields where random or multiple input frequencies beyond the narrow band are *** this work,we demonstrate that a new set of QBIC resonances can be supported by using a special binary grating consisting of two alternatingly aligned ridge arrays with the same period and zero-approaching ridge width difference on a slab *** QBIC resonances are distributed continuously over a broad band along a line in theω~k space and can thus be considered as 1 D *** the Q factors generally affected by the ridge difference,it is now possible to arbitrarily choose any frequencies on the dispersion line to achieve significantly enhanced light-matter interactions,facilitating many applications where multiple input wavelengths are required;e.g.,sum or difference frequency generations in nonlinear optics.

关键词： quasi nonlinear narrow

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One-dimensional quasi bound states in the continuum with large operation bandwidth in the ω~k space for nonlinear optical applications

arXiv

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arXiv 2022年

作者： Sun, Kaili Jiang, Hui Bykov, Dmitry A. Van, Vien Levy, Uriel Cai, Yangjian Han, Zhanghua Shandong Provincial Key Laboratory of Optics and Photonic Devices Center of Light Manipulation and Applications School of Physics and Electronics Shandong Normal University Jinan250358 China Image Processing Systems Institute Branch of the Federal Scientific Research Centre "Crystallography and Photonics" Russian Academy of Sciences 151 Molodogvardeyskaya st. Samara443001 Russia Department of Electrical and Computer Engineering University of Alberta EdmontonT6G 2V4 Canada Department of Applied Physics The center for Nanoscience and Nanotechnology The Hebrew University of Jerusalem Jerusalem Israel

The phenomenon of bound state in the continuum (BIC) with infinite quality factor and lifetime has emerged in recent years in photonics as a new tool of manipulating light-matter interactions. However, most of the investigated structures only support BIC resonances at very few discrete points in the ω~k space. Even when the BIC is switched to a quasi-BIC(QBIC) resonance through perturbation, its frequency will still be located within a narrow spectral band close to that of the original BIC, restricting their applications in many fields where random or multiple input frequencies beyond the narrow band are required. In this work, we demonstrate that a new set of QBIC resonances can be supported by making use of a special binary grating consisting of two alternatingly aligned ridge arrays with the same period and zero-approaching ridge width difference on a slab waveguide. These QBIC resonances are distributed continuously over a broad band along a line in the ω~k space and can thus be considered as one-dimensional QBICs. With the Q factors generally affected by the ridge difference, it is now possible to choose arbitrarily any frequencies on the dispersion line to achieve significantly enhanced light-matter interactions, facilitating many applications where multiple input wavelengths are required, e.g. sum or difference frequency generations in nonlinear optics. Copyright © 2022, The Authors. All rights reserved.

关键词： Resonance

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Characterisation of a FPGA-based multi-view stereo system with linear measuring arrangement

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Measurement: Sensors 2021年 18卷

作者： Christina Junger Richard Fütterer Maik Rosenberger Gunther Notni Technische Universität Ilmenau (Department of Mechanical Engineering Group for Quality Assurance and Industrial Image Processing) Ilmenau Germany Fraunhofer Institute for Applied Optics and Precision Engineering Jena Germany

In recent years, stereoscopic image processing algorithms have gained importance for a variety of applications. To capture larger measurement volumes, multiple stereo systems are combined into a multi-view stereo system (MVS). To reduce the amount of data and the data rate, calculation steps close to the sensors are outsourced to field programmable gate arrays (FPGAs) as upstream computing units. In this paper a FPGA-based MVS system with linear camera arrangement and part overlapping field of view is presented. The system consists of four FPGA-based passive stereoscopic systems and a downstream processing unit (Zynq Ultrascale ZU9EG SoC). This synchronizes the pre-processing modules and receives the disparity maps via HDMI. A subsequent computing unit calculates a coherent 3d point cloud. Basic investigation of the system is shown to use this system for road damage detection in the future.

关键词： Multi-view stereo system FPGA Calibration Asphalt cracks Reflection

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Impact of scanner variability on lymph node segmentation in computational pathology

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Journal of Pathology Informatics 2022年 13卷 100127-100127页

作者： Khan, Amjad Janowczyk, Andrew Müller, Felix Blank, Annika Nguyen, Huu Giao Abbet, Christian Studer, Linda Lugli, Alessandro Dawson, Heather Thiran, Jean-Philippe Zlobec, Inti Institute of Pathology University of Bern Murtenstrasse 31 Bern CH-3008 Switzerland Case Western Reserve University Department of Biomedical Engineering Cleveland 44106 OH United States Department of Oncology Lausanne University Hospital and Lausanne University Lausanne Switzerland Swiss Federal Institute of Technology Lausanne (EPFL) Signal Processing Laboratory (LTS5) Lausanne Switzerland Institute of Complex Systems (iCoSyS) University of Applied Sciences and Arts Western Switzerland Delémont Switzerland Document Image and Video Analysis (DIVA) Research Group Department of Informatics University of Fribourg Fribourg Switzerland Department of Radiology Lausanne University Hospital Lausanne University Centre d'Imagerie Biomédicale (CIBM) Lausanne Switzerland Institute of Pathology City Hospital Triemli Zürich Switzerland

Computer-aided diagnostics in histopathology are based on the digitization of glass slides. However, heterogeneity between the images generated by different slide scanners can unfavorably affect the performance of computational algorithms. Here, we evaluate the impact of scanner variability on lymph node segmentation due to its clinical importance in colorectal cancer diagnosis. 100 slides containing 276 lymph nodes were digitized using 4 different slide scanners, and 50 of the lymph nodes containing metastatic cancer cells. These 400 scans were subsequently annotated by 2 experienced pathologists to precisely label lymph node boundary. Three different segmentation methods were then applied and compared: Hematoxylin-channel-based thresholding (HCT), Hematoxylin-based active contours (HAC), and a convolution neural network (U-Net). Evaluation of U-Net trained from both a single scanner and an ensemble of all scanners was completed. Mosaic images based on representative tiles from a scanner were used as a reference image to normalize the new data from different test scanners to evaluate the performance of a pre-trained model. Fine-tuning was carried out by using weights of a model trained on one scanner to initialize model weights for other scanners. To evaluate the domain generalization, domain adversarial learning and stain mix-up augmentation were also implemented. Results show that fine-tuning and domain adversarial learning decreased the impact of scanner variability and greatly improved segmentation across scanners. Overall, U-Net with stain mix-up (Matthews correlation coefficient (MCC) = 0.87), domain adversarial learning (MCC = 0.86), and HAC (MCC = 0.87) were shown to outperform HCT (MCC = 0.81) for segmentation of lymph nodes when compared against the ground truth. The findings of this study should be considered for future algorithms applied in diagnostic routines. © 2022 The Author(s)

关键词： Colorectal cancer Computational pathology Domain generalization Fine tuning Lymph node Lymph node segmentation Scanner variability Whole slide image

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Automated Exudates Detection in Retinal Fundus image Using Morphological Operator and Entropy Maximization Thresholding

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Journal of Biomedical Science and Engineering 2019年第3期12卷 212-224页

作者： G. H. Kom B. C. Wouantsa Tindo J. R. Mboupda Pone A. B. Tiedeu Research Unit of Automation and Applied Informatics (URAIA) Department of Electrical Engineering IUT-FV Bandjoun University of Dschang Bandjoun Cameroon Research Group on Medical Technologies Applied to the Tropics (GRETMAT) Laboratory of Electronics and Signal Processing (LETS) ENSP University of Yaoundé I Yaoundé Cameroon Research Unit for Condensed Matter Electronics and Signal Processing (LAMACETS) Department of Physics University of Dschang Dschang Cameroon Signal Image and Systems Laboratory Ebolowa Cameroon

Blindness which is considered as degrading disabling disease is the final stage that occurs when a certain threshold of visual acuity is overlapped. It happens with vision deficiencies that are pathologic states due to many ocular diseases. Among them, diabetic retinopathy is nowadays a chronic disease that attacks most of diabetic patients. Early detection through automatic screening programs reduces considerably expansion of the disease. Exudates are one of the earliest signs. This paper presents an automated method for exudates detection in digital retinal fundus image. The first step consists of image enhancement. It focuses on histogram expansion and median filter. The difference between filtered image and his inverse reduces noise and removes background while preserving features and patterns related to the exudates. The second step refers to blood vessel removal by using morphological operators. In the last step, we compute the result image with an algorithm based on Entropy Maximization Thresholding to obtain two segmented regions (optical disk and exudates) which were highlighted in the second step. Finally, according to size criteria, we eliminate the other regions obtain the regions of interest related to exudates. Evaluations were done with retinal fundus image DIARETDB1 database. DIARETDB1 gathers high-quality medical images which have been verified by experts. It consists of around 89 colour fundus images of which 84 contain at least mild non-proliferative signs of the diabetic retinopathy. This tool provides a unified framework for benchmarking the methods, but also points out clear deficiencies in the current practice in the method development. Comparing to other recent methods available in literature, we found that the proposed algorithm accomplished better result in terms of sensibility (94.27%) and specificity (97.63%).

关键词： Diabetic Retinopathy Retinal Fundus image Exudates Entropy Maximization Thresholding

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Benchmarking quality-dependent and cost-sensitive score-level multimodal biometric fusion algorithms

arXiv

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arXiv 2021年

作者： Poh, Norman Bourlai, Thirimachos Kittler, Josef Allano, Lorene Alonso-Fernandez, Fernando Ambekar, Onkar Baker, John Dorizzi, Bernadette Fatukasi, Omolara Fierrez, Julian Ganster, Harald Ortega-Garcia, Javier Maurer, Donald Salah, Albert Ali Scheidat, Tobias Vielhauer, Claus Centre for Vision Speech and Signal Processing School of Electronics and Physical Sciences University of Surrey Guildford SurreyGU2 7XH United Kingdom Biometrics Center Lane Department of Computer Science and Electrical Engineering College of Engineering and Mineral Resources West Virginia University MorgantownWV26506-6109 United States Institut Telecom Telecom and Management SudParis Evry91011 France Biometric Recognition Group – ATVS Escuela Politecnica Superior Universidad Autonoma de Madrid Madrid28049 Spain Amsterdam1098 XG Netherlands Applied Physics Laboratory Johns Hopkins University LaurelMD20723 United States Electronics and Physics Department Institut Telecom Telecom and Management SudParis Evry91011 France Institute of Digital Image Processing Joanneum Research Graz8010 Austria ISLA-ISIS University of Amsterdam Amsterdam1098 XG Netherlands Department of Informatics and Media Brandenburg University of Applied Sciences Brandenburg an der HavelD-14770 Germany Research Group Multimedia and Security Department of Technical and Business Information Systems Faculty of Computer Science Otto-von-Guericke-University of Magdeburg MagdeburgD-39106 Germany

Automatically verifying the identity of a person by means of biometrics (e.g., face and fingerprint) is an important application in our day-to-day activities such as accessing banking services and security control in airports. To increase the system reliability, several biometric devices are often used. Such a combined system is known as a multimodal biometric system. This paper reports a benchmarking study carried out within the framework of the BioSecure DS2 (Access Control) evaluation campaign organized by the University of Surrey, involving face, fingerprint, and iris biometrics for person authentication, targeting the application of physical access control in a medium-size establishment with some 500 persons. While multimodal biometrics is a well-investigated subject in the literature, there exists no benchmark for a fusion algorithm comparison. Working towards this goal, we designed two sets of experiments: quality-dependent and cost-sensitive evaluation. The quality-dependent evaluation aims at assessing how well fusion algorithms can perform under changing quality of raw biometric images principally due to change of devices. The cost-sensitive evaluation, on the other hand, investigates how well a fusion algorithm can perform given restricted computation and in the presence of software and hardware failures, resulting in errors such as failure-to-acquire and failure-to-match. Since multiple capturing devices are available, a fusion algorithm should be able to handle this nonideal but nevertheless realistic scenario. In both evaluations, each fusion algorithm is provided with scores from each biometric comparison subsystem as well as the quality measures of both the template and the query data. The response to the call of the evaluation campaign proved very encouraging, with the submission of 22 fusion systems. To the best of our knowledge, this campaign is the first attempt to benchmark quality-based multimodal fusion algorithms. In the presence of changing

关键词： Benchmarking

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3D model based shading correction for the enhancement of multispectral colour measurement accuracy 22

3D model based shading correction for the enhancement of mul...

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22nd World Congress of the International Measurement Confederation, IMEKO 2018

作者： Zhang, C. Breitbarth, A. Rosenberger, M. Notni, G. Ilmenau University of Technology Group for Quality Assurance and Industrial Image Processing Gustav-Kirchhoff-Platz 2 Ilmenau98693 Germany Fraunhofer Institute for Applied Optics and Precision Engineering Albert-Einstein-Straße 7 Jena07745 Germany

Shading effects induced by illumination and local object surface orientation could strongly deteriorate the accuracy of colour imaging. Therefore, a shading correction is needed for high colour fidelity. In this work a 3D model based inverse rendering approach is proposed for a narrowband multispectral 3D colour imaging system with a calibrated extern broadband light source. The colourimetric evaluation with an X-Rite colour checker shows that the proposed method could ensure a mean colour difference value CIEDE2000 ΔE © Published under licence by IOP Publishing Ltd.

关键词： Color

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The spectral properties of vandermonde matrices with clustered nodes

arXiv

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arXiv 2019年

作者： Batenkov, Dmitry Diederichs, Benedikt Goldman, Gil Yomdin, Yosef Department of Applied Mathematics School of Mathematical Sciences Tel Aviv University P.O. Box 39040 Tel Aviv6997801 Israel University of Passau and Fraunhofer IIS Research Group Knowledge Based Image Processing Passau Germany Department of Mathematics Weizmann Institute of Science Rehovot76100 Israel

We study rectangular Vandermonde matrices V with N + 1 rows and s irregularly spaced nodes on the unit circle, in cases where some of the nodes are "clustered" together - the elements inside each cluster being separated by at most h ≤ 1/N, and the clusters being separated from each other by at least θ ≥ 1/N . We show that any pair of column subspaces corresponding to two different clusters are nearly orthogonal: the minimal principal angle between them is at most π/2 - c1/ Nθ - c2Nh, for some constants c1, c2 depending only on the multiplicities of the clusters. As a result, spectral analysis of VN is significantly simplified by reducing the problem to the analysis of each cluster individually. Consequently we derive accurate estimates for 1) all the singular values of V, and 2) componentwise condition numbers for the linear least squares problem. Importantly, these estimates are exponential only in the local cluster multiplicities, while changing at most linearly with *** Codes 15A18, 65T40, 65F20 Copyright © 2019, The Authors. All rights reserved.

关键词： Number theory

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