Research On Calibration Method Of 3D Measurement System Based On Grating Strip Projection

In recently years, the method of using fringe pattern projection surface profile research has become popular in the field of optical measurement. The technology of based on fringe pattern projection of high-speed real-time 3-D surface measurement has been widely used in the field of industry, medicine, scientific. And as the basis of 3-D measurement system, the system calibration is an essential part of 3-D measurement system before measuring steps, the accuracy and precision of the system calibration will directly affect the measurement accuracy and precision in the process of 3-D measurement system. And the execution and complexity of the 3-D measurement system calibration, will affect the trial conditions and the scope of 3-D measurement system directly. Therefore, this paper mainly studies calibration method based on fringe pattern projection high-speed real-time 3-D measurement system, in purpose to seek simple, high precision, high speed of system calibration method. In addition, in order to improve the speed of 3-D measurement system, this paper do some relevant research in absolute phase extraction method and lookup table algorithm. The main research content is as follows:Detailed analysis of principle of phase-shifting method and temporal, spatial phase unwrapping algorithm, and analyze bi-frequency phase shift algorithm which our group put forward based on three-step phase-shifting method and temporal phase unwrapping algorithm, this algorithm can effectively improve the speed of acquiring absolute phase. According to the relationship among the world coordinate system, camera coordinate system, image physical coordinate system and image pixels coordinate system which based on the camera mathematical model. On the basis of the principle of the pin-hole imaging, linear camera model is set up, at the same time, on this basis we pull-in the camera lens optical distortion, to build a more perfect nonlinear imaging model of camera. This paper improves the Zhang’s plane camera calibration method which is between the traditional calibration methods and self-calibration method, uses binocular calibration board and MATLAB calibration tool-box to solve the camera intrinsic, external parameters and distortion coefficients. Analysis two system calibration methods which are considering the projector calibration and does not consider projector calibration, and puts forward a new calibration method consider camera lens distortion used in high speed 3-D measurement system. Design the new calibration process, only through the camera calibration can simply quickly complete the system calibration. Established the phase look-up table and three-dimensional coordinate look-up table, reduce the amount of data processing, and improve the data processing speed, speed up reconstruction greatly.Prepared for experiments, the use of the presented method to complete the system calibration experiment, by analysis plane-off and plane-in coordinate precision and comparison of the real-time reconstruction result, verify the accuracy and feasibility of the presented method.