Research And Implementation Of Key Technologies For Three-Dimensional Measurement Of Grating Projection Structured Light

Structured light three-dimensional shape measurement system based on grating projection has a wide application prospect in many fields,such as human body and face measurement,product design,rapid manufacturing system,virtual realization and heritage protection.Phase measurement profilometry is one of the widely used structured light three-dimensional shape measurement technologies.However,there are many shortcomings in its system,such as low accuracy,poor robustness and harsh use conditions,which limit the popularization and application of this technology.In this paper,the key problems of digital grating projection are studied systematically and deeply,including phase calculation,phase error compensation,camera and projector parameter calibration,absolute phase to three-dimensional coordinate conversion,etc.The calibration of camera and projector parameters is the basic work of structured light three-dimensional measurement technique.In this paper,Zhang Zhengyou's camera calibration method is used to calibrate the camera in the experimental system at first;then the projector is calibrated as a reverse camera using projection chessboard lattice and camera aperture imaging principle;finally,the camera and projector are estimated separately,and the whole process is realized by C/C++ programming language.Phase measurement profilometry is one of the key technologies in three-dimensional shape measurement based on structured light,and its main steps include wrapped phase calculation and phase unwrapping.In this paper,the wrapped phase of the fringe is calculated by four-step phase-shifting method,and the absolute phase value is obtained by phase unwrapping based on the multi-frequency heterodyne principle.In the process of phase unwrapping,the jumping of fringe series is found to be the source of phase unwrapping error through actual measurement and analysis.On this basis,a multi-frequency heterodyne phase unwrapping error compensation method is proposed.The experimental results show that the proposed algorithm can effectively eliminatethe fringe series jumping error.