Research On Calibration Of 3D Reconstruction System Based On Phase Measurement Profilometry

The three-dimensional reconstruction technique based on phase measuring profilometry(PMP)has been widely used in high-end manufacturing because of its advantages such as non-contact,high sensitivity and high precision.Phase measurement profilometry mainly consists of fringe grating projection,phase unwrapping,phase-height mapping system calibration,etc.Each part has a great influence on the accuracy of 3D reconstruction.This paper focuses on phase-height mapping system calibration.The main research contents are as follows:(1)The camera calibration algorithm is used to achieve the distortion correction of the camera image.Through the mutual conversion between the image coordinate system,the world coordinate system and the camera coordinate system,the camera is calibrated based on the camera pinhole imaging model and the perspective projection matrix,a nonlinear distortion model is established,and finally the distortion correction of the camera image is achieved.(2)Establish a phase-height mapping model,study the phase-height mapping system calibration based on polynomial fitting(Hereinafter referred to as polynomial fitting calibration),and propose a segmented polynomial fitting calibration algorithm.By analyzing the effect of fitting order and fitting data on the accuracy and speed of the polynomial fitting calibration,it was found that when the fitting order is 2,the measuring range is 500?m,and the fitting interval is 90?m,not only can obtain higher calibration accuracy and speed,but also has good stability.Finally,a segmented polynomial fitting calibration algorithm is proposed on this basis,which makes the calibration accuracy of the system higher than the system calibration accuracy under each order.(3)A three-dimensional reconstruction of shadow compensation and texture-mapping algorithm is proposed,which makes the three-dimensional reconstruction more accurate and the three-dimensional reconstruction model more realistic.By comparing the images of the dual projectors,the shadow area is found out,and finally the shadow area is compensated by the three-dimensional reconstruction data.By extracting the color texture of the twodimensional color image of the object to be measured,a texture map of the three-dimensional reconstruction model is realized.(4)The camera position and path-planning algorithm is proposed,that improve the detection speed of the solder paste on the circuit board.In traditional inspections,full-print scanning and photographing of printed circuit boards reduces solder paste inspection speed.In response to this situation,a solution is proposed.Searching for the minimum number of camera views that satisfy all the solder pastes to be included in the camera field of view through the solder paste positioning data on the circuit board.Recording the center position of each field of view,and then calculating the shortest movement path between the center positions,and finally the path is used as the camera movement path.Experiments show that compared with the traditional method,the camera position and path-planning algorithm can avoid the shooting of the solder paste position and improve the solder paste inspect speed.