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Effect of the nonlinearity of the CCD in Fourier transform profilometry on spectrum overlapping and measurement accuracy

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Chinese Physics B 2013年第1期22卷 237-242页

作者：乔闹生邹北骥 School of Information Science and Engineering Central South University School of Physics and Electronics Hunan University of Arts and Science

In Fourier transform profilometry （FTP）, we must restrain spectrum overlapping caused by the nonlinearity of the charge coupled device （CCD） and increase the measurement accuracy of the object shape. Firstly, the causes of producing higher-order spectrum components and inducing spectrum overlapping are analysed theoretically, and a simple physical ex- planation and analytical deduction are given. Secondly, aiming to suppress spectrum overlapping and improve measurement accuracy, the influence of spatial carrier frequency of projection grating on them is analysed. A method of increasing the spatial carrier frequency of projection grating to restrain or reduce the spectrum overlapping significantly is proposed. We then analyze the mechanism of how the spectrum overlapping is reduced. Finally, the simulation results and experimental measurements verify the correction of the proposed theory and method.

关键词： spectra overlapping measurement accuracy nonlinearity of CCD Fourier transform profilometry

Research on measurement accuracy of the Double-Channel Microwave Power Sensors Based on an MEMS Cantilever Beam

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Chinese Journal of Electronics 2019年第5期28卷 916-919页

作者： WANG Debo WU Lele LI Longfei DAI Ruiping Nanjing University of Posts and Telecommunication

A thermopile-based microwave power sensor and a double-channel microwave power sensor are compared in order to research the measurement accuracy of microwave power. The relationship of the displacement of MEMS cantilever beam with the measured microwave power is researched, and the reason that the microwave power consumed by the MEMS cantilever cannot be ignored at low power level is *** ratio of microwave power consumed by the MEMS cantilever with the microwave frequency is obtained,and the measured results show that the percentage is 51.96%@8 GHz, 52.31%@10 GHz and 55.11%@12 GHz on the average, respectively. There is an important reference value to achieve the accurate microwave power measurement of the double-channel microwave power sensors.

关键词： Thermopile-based power sensor MEMS cantilever Double-channel measurement accuracy

Multiple measurement Models of Articulated Arm Coordinate Measuring Machines

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Chinese Journal of Mechanical Engineering 2015年第5期28卷 994-998页

作者： ZHENG Dateng XIAO Zhongyue XIA Xiang College of Mechanical & Electrical Engineering Jinggangshan University

The existing articulated arm coordinate measuring machines（AACMM） with one measurement model are easy to cause low measurement accuracy because the whole sampling space is much bigger than the result in the unstable calibration parameters. To compensate for the deficiency of one measurement model, the multiple measurement models are built by the Denavit-Hartenberg＇s notation, the homemade standard rod components are used as a calibration tool and the Levenberg-Marquardt calibration algorithm is applied to solve the structural parameters in the measurement models. During the tests of multiple measurement models, the sample areas are selected in two situations. It is found that the measurement errors＇ sigma value（0.083 4 ram） dealt with one measurement model is nearly two times larger than that of the multiple measurement models（0.043 1 ram） in the same sample area. While in the different sample area, the measurement errors＇ sigma value（0.054 0 ram） dealt with the multiple measurement models is about 40% of one measurement model（0.137 3 mm）. The preliminary results suggest that the measurement accuracy of AACMM dealt with multiple measurement models is superior to the accuracy of the existing machine with one measurement model. This paper proposes the multiple measurement models to improve the measurement accuracy of AACMM without increasing any hardware cost.

关键词： articulated arm coordinate measuring machine multiple measurement models sample area measurement accuracy

Research on inter-satellite measurement technique in high dynamic environment

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Journal of Beijing Institute of Technology 2015年第2期24卷 233-239页

作者：王永庆孙立达杨丽云姜洪伟吴嗣亮 School of Information and Electronics Beijing Institute of Technology

An improved measurement algorithm, based upon the theory of two-way time transfer （ TWTT）, is proposed to measure satellites with high speeds. The algorithm makes theoretical analyses and corresponding deductions on a relative motion model of two satellites, and eliminates the measurement error caused by the equipment delay when a satellite moves at a high speed. Theoretical analysis and simulation results demonstrate that in comparison with the conventional TWTT algorithm, the proposed algorithm can significantly enhance the measurement accuracy of the inter-satellite ranging and time synchronization, and the algorithm is more effective with the relative velocity between the satellites and transmitting delay becoming larger.

关键词： two-way time transfer ranging time synchronization measurement accuracy

THE ESTIMATE AND measurement OF TRANSVERSE WAVE INTENSITY

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Acta Mechanica Solida Sinica 1997年第3期10卷 235-245页

作者： Ming Ruisen, Department of Architecture, Zhejiang University, Hangzhou 310027, China Department of Architecture Zhejiang University Hangzhou 310027 China

Transverse waves are a type of structural waves and should be considered in the analysis of high frequency vibration because the energy carried by transverse waves increases with the increase of frequency and becomes important at high frequencies. This paper studies the estimate theory and measuring technique of the transverse wave intensity in two-dimensional homogeneous structures. In general, the intensity vector is the sum of the effective intensity vector and the intensity variation vector. Each axial intensity component is proportional to two imaginary parts of cross spectral densities and its estimate is complicated. For the special case where transverse waves propagate in one direction, the intensity variation is zero and the estimate of the intensity is simplified. The intensity technique is formed based on the finite difference principle. Transverse wave intensity can be measured using a pair of two-transducer arrays lying in the orthogonal direction for the general case or a two-transducer array lying in the propagating direction for the special case. In order to assess the measurement accuracy of transverse wave intensify, the coupling loss factors from bending to transverse waves in building structures were measured using the intensity technique and compared with the results predicted and measured using the conventional method. It is shown that the agreement between the results measured using the intensity technique and that by the conventional method is good.

关键词： transverse wave intensity estimate theory measurement accuracy

In-situ 3D contour measurement for laser powder bed fusion based on phase guidance

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Theoretical & Applied Mechanics Letters 2023年第2期13卷 113-119页

作者： Yuze Zhang Pan Zhang Xin Jiang Siyuan Zhang Kai Zhong Zhongwei Li State Key Lab of Materials Processing and Die&Mould Technology Huazhong University of Science and TechnologyWuhan430074China Research Institute of Huazhong University of Science and Technology in Shenzhen Shenzhen51800China

In-situ layerwise imaging measurement of laser powder bed fusion(LPBF)provides a wealth of forming and defect data which enables monitoring of components quality and powder bed *** high-resolution camera layerwise imaging and image processing algorithms to monitor fusion area and powder bed geometric defects has been studied by many researchers,which successfully monitored the contours of components and evaluated their ***,research for the methods of in-situ 3D contour measurement or component edge warping identification is *** this study,a 3D contour mea-surement method combining gray intensity and phase difference is proposed,and its accuracy is verified by designed *** results show that the high-precision of the 3D contours can be achieved by the constructed energy minimization *** method can detect the deviations of common ge-ometric features as well as warpage at LPBF component edges,and provides fundamental data for in-situ quality monitoring tools.

关键词： Laser powder bed fusion In-situ measurement Active contours 3D contour measurement accuracy

A light field measurement system through PSF estimation by a morphology-based method

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International Journal of Extreme Manufacturing 2021年第4期3卷 113-124页

作者： Lingbao Kong Panyu Zhou Shanghai Engineering Research Center of Ultra-precision Optical Manufacturing Fudan UniversityShanghai 200433People’s Republic of China

Light field imaging technology can obtain three-dimensional(3D)information of a test surface in a single *** light field reconstruction algorithms not only take a long time to trace back to the original image,but also require the exact parameters of the light field system,such as the position and posture of a microlens array(MLA),which will cause errors in the reconstructed image if these parameters cannot be precisely *** paper proposes a reconstruction algorithm for light field imaging based on the point spread function(PSF),which does not require prior knowledge of the *** accurate PSF derivation process of a light field system is presented,and modeling and simulation were conducted to obtain the relationship between the spatial distribution characteristics and the PSF of the light field system.A morphology-based method is proposed to analyze the overlapping area of the subimages of light field images to identify the accurate spatial location of the MLA used in the system,which is thereafter used to accurately refocus light field imaging.A light field system is built to verify the algorithm’s *** results show that the measurement accuracy is increased over 41.0%compared with the traditional method by measuring a step *** accuracy of parameters is also improved through a microstructure measurement with a peak-to-valley value of 25.4%and root mean square value of 23.5%*** further validates that the algorithm can effectively improve the refocusing efficiency and the accuracy of the light field imaging results with the superiority of refocusing light field imaging without prior knowledge of the *** proposed method provides a new solution for fast and accurate 3D measurement based on a light field.

关键词： light field deconvolution 3D measurement PSF estimation measurement accuracy MLA

Influence of sampling on three-dimensional surface shape measurement

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中国光学（中英文） 2024年第6期17卷 1512-1520页

作者： QIAO Nao-sheng Shang Xue International College Hunan University of Arts and ScienceChangde 415000China Mathematics and Physics Science College Hunan University of Arts and ScienceChangde 415000China

In order to accurately measure an object’s three-dimensional surface shape,the influence of sampling on it was ***,on the basis of deriving spectra expressions through the Fourier transform,the generation of CCD pixels was analyzed,and its expression was ***,based on the discrete expression of deformation fringes obtained after sampling,its Fourier spectrum expression was derived,resulting in an infinitely repeated"spectra island"in the frequency ***,on the basis of using a low-pass filter to remove high-order harmonic components and retaining only one fundamental frequency component,the inverse Fourier transform was used to reconstruct the signal strength.A method of reducing the sampling interval,i.e.,reducing the number of sampling points per fringe,was proposed to increase the ratio between the sampling frequency and the fundamental frequency of the *** was done to reconstruct the object’s surface shape more accurately under the condition of m>*** basic principle was verified through simulation and *** the simulation,the sampling intervals were 8 pixels,4 pixels,2 pixels,and 1 pixel,the maximum absolute error values obtained in the last three situations were 88.80%,38.38%,and 31.50%in the first situation,respectively,and the corresponding average absolute error values are 71.84%,43.27%,and 32.26%.It is demonstrated that the smaller the sampling interval,the better the recovery *** the same four sampling intervals in the experiment as in the simulation can also lead to the same *** simulated and experimental results show that reducing the sampling interval can improve the accuracy of object surface shape measurement and achieve better reconstruction results.

关键词： three-dimensional surface shape measurement sampling interval spectra overlapping measurement accuracy

Study on application potentiality of the first China's ocean satellite HY-1A

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Acta Oceanologica Sinica 2003年第4期22卷 503-510页

作者： Pan Delu1,He Xianqiang1,Li Shujing1,Gong Fang1 1.Laboratory of Ocean Dynamic Processes and Satellite Oceanography of State Oceanic Administration,Hangzhou 310012,China. Lab. of Ocean Dynamic Processes Hangzhou 310012 China

China has launched her first ocean color satellite HY-1A on May 15, 2002 since American ocean color satellite SeaSTAR was on the orbit in 1997. First, the properties and characteristics of HY-1A are briefly introduced; second, the quality and availability are evaluated by means of the complex signal noise ratio ( CSNR) which is simulated theoretically; third, the received HY-1A data are compared with SeaSTAR data to understand the accuracy of radiance measurement by the HY-1A; finally, the remote sensing products of ocean color and temperature are mapped to study the application potentiality of HY-1A. The results show that the HY-1A has its latent capability for the application of marine environment detection, the management and protection of marine resources, and the national rights and interests. Meanwhile some suggestions are proposed to modify the next ocean satellite.

关键词： ocean satellite availability measurement accuracy application potentiality