Research On Camera Calibration Algorithm In Large-scale Volume Measurement

In order to solve the measurement problem of material pile for large volume, this thesis explores a volume measuring system bases on tri-vision and do research into camera calibration algorithm. This thesis designs a camera calibration with both highly accurate and convenient to applicability.The main contents of this thesis are listed as follows:(1) The device of the whole experiment measurement system was designed. The calibration board (26mmx26mm) and test board with a cubes module (10cm×10cm×10cm) are made. The projected grids and protecting lamp was install, then the camera to be installed to the pan-and-tilt stabilitily and the camera’s 3D position was ensured.(2) The argument of camera calibration parameter and distortion coefficients of camera lens were determined by analyzing the theory of camera calibration. Mathematical model based on the relationship among the different coordinate system was built.(3) The camera calibration by Zhang Zhengyou was accomplished. Zhang calibration algorithm was selected on the basis of studying on typical camera calibration camera calibration theory and algorithm and the comparing the advantages and disadvantages of these methods. First of all, the homography matrix of images can be found out according to the relationship between world coordinates and image coordinates of feature points. Two basic restricts by the homography matrix and the orthogonality of the rotation matrix can be worked out, then the camera internal parameters can be separated. Finally the camera external parameters can be obtained by the homography matrix and the camera internal parameters. All of camera parameters with the distortion coefficients of camera lens can be acquired by optimization search.(4) Zhang Zhengyou calibration algorithm was perfected according to the material stack. The camera calibration was divided into two parts. Firstly the camera internal parameters can be received from a group of images. Secondly the homography matrix of material stack image can be got, and then the camera external parameters of material stack image can be obtained.(5) Camera calibration algorithm was evaluated by the theory of recovering the world coordinates. The known world coordinates and the recovering world coordinates of test module by camera parameters are compared. The accuracy in experiment of this camera calibration algorithm meets the requirement of this subject.(6) Deflection correction for the 3D point of the material pile was conducted by using interpolation by the algorithm of radial basis interpolation function for the corrected material pile scatter points. This experiment achieved 3D reconstruction and the volume calculation of the material pile. It also assures the relative error of the material pile volume ranges meets the requirement of this subject.This thesis achieves the camera calibration, reaching the material pile measurement accuracy through modeling tests in lab.