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Optical measurement of high-temperature melt flow rate

APPLIED OPTICS 2018年第15期57卷 4202-4210页

作者： Bizjan, Benjamin Sirok, Brane Chen, Jinpeng Univ Ljubljana Fac Mech Engn Askeroeva 6 Ljubljana 1000 Slovenia Abelium Doo Res & Dev Kajuhova 90 Ljubljana 1119 Slovenia Guangdong Univ Petrochem Technol 139 Guandu Erlu Maoming 525000 Guangdong Peoples R China

This paper presents an optical method and system for contactless measurement of the mass flow rate of melts by digital cameras. The proposed method is based on reconstruction of melt stream geometry and flow velocity calculation by cross correlation, and is very cost-effective due its modest hardware requirements. Using a laboratory test rig with a small inductive melting pot and reference mass flow rate measurement by weighing, the proposed method was demonstrated to have an excellent dynamic response (0.1 s order of magnitude) while producing deviations from the reference of about 5% in the steady-state flow regime. Similar results were obtained in an industrial stone wool production line for two repeated measurements. Our method was tested in a wide range of melt flow rates (0.05-1.2 kg/s) and did not require very fast cameras (120 frames per second would be sufficient for most industrial applications). (C) 2018 Optical Society of America

关键词： Edge detection image processing algorithms image resolution Laser beams Laser velocimetry Optical measurement

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Learning Siamese networks for laser vision seam tracking

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JOURNAL OF THE OPTICAL SOCIETY OF AMERICA A-OPTICS image SCIENCE AND VISION 2018年第11期35卷 1805-1813页

作者： Zou, Yanbiao Li, Jinchao Chen, Xiangzhi Lan, Rui South China Univ Technol Sch Mech & Automot Engn Guangzhou 510640 Guangdong Peoples R China

To design a stable laser vision seam-tracking system, an advanced weld image processing algorithm based on Siamese networks is investigated and proposed to resist the interference of arc and spatter in the welding process. This specially designed neural network, combined with powerful feature expression capabilities of deep learning, takes two welding images with different sizes as inputs and generates a target confidence map in a single forward pass by using the cross-correlation algorithm. To prevent the error accumulation and model drift, an online update strategy via local cosine similarity is developed. The use of metal inert-gas welding can realize real-time and precious tracking under the condition that the strong arc continuously shields the welding seam feature points. (C) 2018 Optical Society of America.

关键词： image processing image processing algorithms image quality Joint transform correlators Laser beams Laser sensors

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Influence of ambient temperature on the modulation transfer function of an infrared membrane diffraction optical system

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APPLIED OPTICS 2018年第30期57卷 9096-9105页

作者： Wang, Dawei Zhi, Xiyang Zhang, Wei Yin, Zhongke Jiang, Shikai Niu, Ruize Harbin Inst Technol Res Ctr Space Opt Engn Harbin 150001 Heilongjiang Peoples R China Inst Remote Sensing Informat Beijing 100192 Peoples R China

In this paper, we present a model that analyzes the influence of the temperature on the modulation transfer function (MTF) of an infrared membrane diffraction optical system. Based on the physical imaging mechanism of diffractive optical systems, the imaging characteristics of the diffraction optical system are characterized by using diffraction efficiency. Then we establish the corresponding calculation model and MTF analysis model based on scalar diffraction theory. In particular, considering the material properties of flexible membrane optical elements and thermal environment effect, the Zernike polynomials are used to establish the thickness distribution model of the membrane diffractive optical components combined with the finite element analysis. After that, we modify the MTF calculation model of diffraction optical system and accordingly propose the model of the infrared membrane diffraction optical system. Finally, we present some experimental results for a 2-m infrared membrane diffraction optical system. The results show that when the temperature is -40 degrees C and wavelength band is 80 nm at the center field of view, the diffraction efficiency is reduced to 81%, and MTF at 751 p/mm is reduced to 0.12. And when the temperature is -40 degrees C at edge field of view, the efficiency at center wavelength is reduced to 71%, and MTF at 751 p/mm is reduced to 0.02. The established model and method can be used to estimate the imaging performance of a space infrared membrane diffractive telescope and provide theoretical guidance for the processing algorithm and imaging system design. (C) 2018 Optical Society of America

关键词： Diffractive optical elements image processing image processing algorithms Optical components Systems design Thermal effects

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Study of an image autofocus method based on power threshold function wavelet reconstruction and a quality evaluation algorithm

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APPLIED OPTICS 2018年第33期57卷 9714-9721页

作者： Yan, Zhidan Chen, Guo Xu, Wenyi Yang, Chunmei Lu, Yang China Univ Petr East China Coll Informat & Control Engn Changjiangxi Rd 66 Qingdao 266580 Shandong Peoples R China Tianjin Univ State Key Lab Precis Measuring Technol & Instrume Univ Weijin Rd 92 Tianjin 300072 Peoples R China

As a key component in optical microscopy imaging systems, autofocus technology has a significant effect on imaging quality. In this paper, an optical microscopy autofocus method that includes a wavelet denoising algorithm based on a power threshold function and a Brenner image quality evaluation algorithm is presented. Experimental results show that the power threshold function wavelet denoising algorithm, which can be adopted to obtain more realistic optical images, is superior to the traditional soft, hard, hyperbolic, and exponential threshold functions in terms of peak signal-to-noise ratio, signal-to-noise ratio, mean squared error, and histogram indicators;moreover, compared to the Roberts, sum modulus difference (SMD), and energy gradient functions, the Brenner image quality evaluation algorithm can be used to quickly and accurately lock onto the focal plane. By integrating and applying these two core algorithms in the autofocus image acquisition system of a microscope, the image sharpness and focusing quality are greatly improved, which benefits the further evaluation of images. (C) 2018 Optical Society of America

关键词： image processing image processing algorithms image quality image resolution Imaging systems Signal processing

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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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Do EnChroma glasses improve color vision for colorblind subjects?

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OPTICS EXPRESS 2018年第22期26卷 28693-28703页

作者： Gomez-Robledo, L. Valero, E. M. Huertas, R. Martinez-Domingo, M. A. Hernandez-Andres, J. Univ Granada Dept Opt Granada Spain

The commercialization of EnChroma glasses has generated great expectations for people to be able to see new colors or even correct color vision deficiency (CVD). We evaluate the effectiveness of these glasses using two complementary strategies for the first time. The first consists of using the three classical types of tests - recognition, arrangement and discrimination - with and without glasses, with a high number of individuals. In the second, we use the spectral transmittance of the glasses to simulate the appearance of stimuli in a set of scenes for normal observers and observers with CVD. The results show that the glasses introduce a variation of the perceived color, but neither improve results in the diagnosis tests nor allow the observers with CVD to have a more normal color vision. (C) 2018 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

关键词： Color blindness Color spaces Color vision image processing algorithms Standard observers Visible light

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Research of the three-dimensional tracking and registration method based on multiobjective constraints in an AR system

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APPLIED OPTICS 2018年第32期57卷 9625-9634页

作者： An, Zhe Xu, Xiping Yang, Jinhua Liu, Yang Yan, Yuxuan Changchun Univ Sci & Technol Sch Optoelect Engn Changchun 130022 Jilin Peoples R China Changchun Univ Sci & Technol State Key Lab High Power Semicond Lasers Changchun 130022 Jilin Peoples R China

To match the virtual image and actual environment in an augmented reality (AR) system, it is necessary to complete the task of three-dimensional (3D) tracking registration. This paper proposes a new method for 3D tracking registration. Previous methods extract feature points in images to realize tracking registration. In this paper, the objects are extracted from the deep convolution neural network in the scene, and the camera pose is estimated by establishing the constraint relation of the objects. Then, 3D tracking and registration of the virtual object are realized. We design an improved single-shot multibox detector semantic segmentation network to identify and segment the scene and extract the pixel classification results of the objects in the scene. The effect of classification with this method is better. The depth of the extracted object is estimated based on the data from the left and right cameras, and the 2D image is converted into a 3D point cloud. A camera pose estimation method, combined with multiobjective information, is proposed. The camera transformation matrix is directly estimated by establishing a mathematical model. This method avoids the effect on the accuracy of the camera pose estimation when the feature points are not sufficient. Moreover, by assigning different weights to the point clouds of different objects, errors caused by the model can be reduced. The experimental results showed that the 3D registration method proposed in this paper is less than 2.5 pixels in the application scene of an augmented reality head-up display. This method had a better effect compared with that of existing methods and also improved driving safety. (C) 2018 Optical Society of America

关键词： Feature extraction image processing algorithms image registration image restoration Neural networks Virtual reality

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Time-multiplexed multi-view three-dimensional display with projector array and steering screen

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OPTICS EXPRESS 2018年第12期26卷 15528-15538页

作者： Xia, Xinxing Zhang, Xiangyu Zhang, Lei Surman, Phil Zheng, Yuanjin Nanyang Technol Univ Sch Elect & Elect Engn 50 Nanvang Ave Singapore 639798 Singapore

A novel time-multiplexed multi-view three-dimensional (3D) display has been implemented using a projector array to provide the image source and an angular steering-screen module to generate multiple high density horizontal views. The liquid crystal (LC)-based steering screen was specially developed to deflect light beams over a small range and operate in synchronism with the projector array with the use of a customized FPGA driver. The prototype produces vivid color 3D scenes with smooth parallax to multiple viewers. The experimental results verify the proposed multi-projection time-multiplexed multi-view 3D display method that uses a steering screen to produce dense views. Displaying both static and dynamic 3D contents is achieved in our implemented 36-view 3D display prototype. The results of crosstalk measurements are given and analyzed to evaluate the display performance. (C) 2018 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

关键词： Flat panel displays Holographic displays image processing algorithms Optical systems Pico projectors Three dimensional television

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Super-resolution fluorescence blinking imaging using modified Fourier ptychography

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OPTICS EXPRESS 2018年第3期26卷 2740-2748页

作者： Wu, Jingjing Yu, Bin Zhang, Saiwen Li, Siwei Wang, Xuehua Chen, Danni Qu, Junle Shenzhen Univ Coll Optoelect Engn Minist Educ & Guangdong Prov Key Lab Optoelect Devices & Syst Shenzhen 518060 Peoples R China Shenzhen Univ Coll Optoelect Engn Shenzhen Key Lab Micro Nano Measuring & Imaging B Shenzhen 518060 Peoples R China

In this paper, we propose a new super-resolution imaging technique based on fluorescence blinking (SRFB). Contrary to structured illumination microscopy (SIM), SRFB considers the time-varying fluorescence distribution under a suitable density as the varying illuminated speckle pattern, and therefore, external speckle patterns or diffusers are not required. With several images recorded at different times, a super-resolution image can be obtained through an iterative algorithm modified from Fourier ptychography. Recorded image sequences in a microscopy imaging experiment based on photo switching or fluorescence blinking effects, such as STORM and SOFI, can be handled with SRFB and used to recover a super-resolution image. The simulation and experimental results confirm that the SRFB scheme can surpass the diffraction limit by a factor greater than two. (c) 2018 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

关键词： Diffraction limit image processing algorithms Imaging techniques Optical imaging Speckle patterns Structured illumination microscopy

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Integrated holographic waveguide display system with a common optical path for visible and infrared light

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OPTICS EXPRESS 2018年第25期26卷 32802-32811页

作者： Lv, Zhenlv Liu, Juan Xiao, Jiasheng Kuang, Ying Beijing Inst Technol Sch Opt & Photon Beijing Engn Res Ctr Mixed Real & Adv Display Beijing 100081 Peoples R China

We propose an integrated holographic waveguide display system. An infrared volume holographic grating (IVHG) and a visible light grating are recorded on the mine waveguide to achieve the purpose of a common light path for system miniaturization. Simulated and experimental results verify the feasibility of this method. The coupling efficiencies of the infrared module for eye tracking and the visible light module for augmented reality (AR) display are 40% and 45%. The holographic waveguide has a weight of only 4.3 grams. It is believed that this technique is a good way to achieve a light and thin eye tracking near-eye display. (C) 2018 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

关键词： Diffraction efficiency Diffractive optical elements Holographic displays Holographic recording materials image processing algorithms Total internal reflection

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