In order to get the entire data in the optical measurement, a multi-view three-dimensional(3D) measurement method based on turntable is proposed. In the method, a turntable is used to rotate the object and obtain mult...In order to get the entire data in the optical measurement, a multi-view three-dimensional(3D) measurement method based on turntable is proposed. In the method, a turntable is used to rotate the object and obtain multi-view point cloud data, and then multi-view point cloud data are registered and integrated into a 3D model. The measurement results are compared with that of the sticking marked point method. Experimental results show that the measurement process of the proposed method is simpler, and the scanning speed and accuracy are improved.展开更多
The point spread function（PSF） is investigated in order to study the centroids algorithm in a reverse Hartmann test（RHT） system. Instead of the diffractive Airy disk in previous researches, the intensity of PSF be...The point spread function（PSF） is investigated in order to study the centroids algorithm in a reverse Hartmann test（RHT） system. Instead of the diffractive Airy disk in previous researches, the intensity of PSF behaves as a circle of confusion（CoC） and is evaluated in terms of the Lommel function in this paper. The fitting of a single spot with the Gaussian profile to identify its centroid forms the basis of the proposed centroid algorithm. In the implementation process, gray compensation is performed to obtain an intensity distribution in the form of a two-dimensional（2D） Gauss function while the center of the peak is derived as a centroid value. The segmental fringe is also fitted row by row with the one-dimensional（1D） Gauss function and reconstituted by averaged parameter values. The condition used for the proposed method is determined by the strength of linear dependence evaluated by Pearson＇s correlation coefficient between profiles of Airy disk and CoC. The accuracies of CoC fitting and centroid computation are theoretically and experimentally demonstrated by simulation and RHTs. The simulation results show that when the correlation coefficient value is more than 0.9999, the proposed centroid algorithm reduces the root-mean-square error（RMSE） by nearly one order of magnitude, thus achieving an accuracy of - 0.01 pixel or better performance in experiment. In addition, the 2D and 1D Gaussian fittings for the segmental fringe achieve almost the same centroid results, which further confirm the feasibility and advantage of the theory and method.展开更多
A method for isochromatic determination in three-fringe photoelasticity is presented. It combines the phaseshifting method with cubic polynomial curve-fitting technology to eliminate the errors caused by color repetit...A method for isochromatic determination in three-fringe photoelasticity is presented. It combines the phaseshifting method with cubic polynomial curve-fitting technology to eliminate the errors caused by color repetition.We perform a demonstration of the method on a circular disc subjected to compressive loading and an injectionmolded cover with residual stresses. The test results compare well with the theoretical results.展开更多
基金supported by the National Natural Science Foundation of China(Nos.60808020 and 61078041)the Natural Science Foundation of Tianjin City(Nos.15JCYBJC51700 and 16JCYBJC15400)the National Science and Technology Support(No.2014BAH03F01)
文摘In order to get the entire data in the optical measurement, a multi-view three-dimensional(3D) measurement method based on turntable is proposed. In the method, a turntable is used to rotate the object and obtain multi-view point cloud data, and then multi-view point cloud data are registered and integrated into a 3D model. The measurement results are compared with that of the sticking marked point method. Experimental results show that the measurement process of the proposed method is simpler, and the scanning speed and accuracy are improved.
基金Project supported by the National Natural Science Foundation of China(Grant No.61475018)
文摘The point spread function（PSF） is investigated in order to study the centroids algorithm in a reverse Hartmann test（RHT） system. Instead of the diffractive Airy disk in previous researches, the intensity of PSF behaves as a circle of confusion（CoC） and is evaluated in terms of the Lommel function in this paper. The fitting of a single spot with the Gaussian profile to identify its centroid forms the basis of the proposed centroid algorithm. In the implementation process, gray compensation is performed to obtain an intensity distribution in the form of a two-dimensional（2D） Gauss function while the center of the peak is derived as a centroid value. The segmental fringe is also fitted row by row with the one-dimensional（1D） Gauss function and reconstituted by averaged parameter values. The condition used for the proposed method is determined by the strength of linear dependence evaluated by Pearson＇s correlation coefficient between profiles of Airy disk and CoC. The accuracies of CoC fitting and centroid computation are theoretically and experimentally demonstrated by simulation and RHTs. The simulation results show that when the correlation coefficient value is more than 0.9999, the proposed centroid algorithm reduces the root-mean-square error（RMSE） by nearly one order of magnitude, thus achieving an accuracy of - 0.01 pixel or better performance in experiment. In addition, the 2D and 1D Gaussian fittings for the segmental fringe achieve almost the same centroid results, which further confirm the feasibility and advantage of the theory and method.
基金supported by the Innovation Fund Project for Graduate Students of Shanghai under Grant No. JWCXSL1301
文摘A method for isochromatic determination in three-fringe photoelasticity is presented. It combines the phaseshifting method with cubic polynomial curve-fitting technology to eliminate the errors caused by color repetition.We perform a demonstration of the method on a circular disc subjected to compressive loading and an injectionmolded cover with residual stresses. The test results compare well with the theoretical results.
