Research On Calibration Of 3D Vision Reconstruction System Based On Parallel Mechanism

3D reconstruction is one of the main contents of computer vision technology. The technology of 3D reconstruction based on structured light is one of the most widely used and relatively mature technologies and it is noncontact. Parallel mechanism research becomes a focus because of its merits. Therefore, the combine of 6-DOF parallel mechanism and structured light technology builds a 3D vision reconstruction system based on parallel mechanism in this paper. This system takes on special significance and application. How to calibrate the system with which to obtain the point cloud data of reconstruction object is the basal and pivotal issue. For the purpose of system calibration, every segment of calibration is researched in this paper.Firstly, aiming at the problem in the process of calibration of 3D reconstruction system based on optical triangle principle, a new calibration program is adopted. According to the calibration principle, the math-transform model among 2D image coordinates and 3D space coordinates is established. The position relationship of hardwares is configured and the flow of system is designed.Secondly, aiming at the limitations of current corner detecting algorithms, a novel algorithm is proposed for detecting both internal and external corners. Initial locations of corners are gained by introducing perpective projection transform. Internal corners are detected with SV operator and external corners are detected with Q operator which is defined in this paper.The sub-pixel locations of corners are achieved.Thirdly, founded on the in-depth analysis of the camera calibration methods, a linear approach for camera calibration based on parallel mechanism is introduced. First, the integrated expression of camera model of one order radial distortion is educed.Then a virtual 3D object is simulated by the moving platform of the 6-DOF parallel mechanism as the carrier of 2D coplanar planes. Last, the parameters of camera are computed one-off linearly using the foregoing camera model and the information of virtual 3D object.Finally, with a coded scheme of structured light based on De Bruijn sequence which is based on the thinking of space neighborhood, structured light-plane equations are calibrated using of cross-ratio invariance and the known information of calibration target. A calibration method of the whole structured light-plane based on parallel mechanism is introduced.