Research And Application Of The Wide-angle Camera Calibration Based On Concentric Circles

Camera calibration is one of the most important parts in application of computer vision.With the rapid development of industry, there has been an increasing demand for three-dimensional overall measurement of large sized objects. This thesis proposes a wide-angle camera calibration scheme based on the pattern of concentric circles and the registration template. The result of the wide-angle camera calibration scheme is applied to the overall measurement of the hoop-rid deployable antenna to demonstrate the feasibility.The main work includes the improvement of the camera's intrinsic parameters based on the pattern of concentric circles, the solution of distortion parameters based on high accuracy locating of the concentric circles, the design of the calibration template based on the registration templates and the measurement of the 3D object based on stereo vision.Firstly, this paper describes the basic theory of projective geometry and camera imaging system, including the ideal camera models and distortion camera models. Then the Meng's method of using circular points to solve the camera calibration is analyzed. Then an improved method to determine the camera intrinsic parameters based on the pattern of concentric circles is presented, and the solution of distortion parameters based on high accuracy locating of the concentric circles is also given. At last, the feasibility of the method is elaborated by means of the theoretical analysis and experimental results.Secondly, a calibration template scheme is presented corresponding to wide-angle camera calibration based on the template registration to meet the demand of large size. The problem which the large size calibration template is difficult to machine and transport is solved. After that the wide-angle camera calibration is done by use of camera calibration method mentioned above combined with the proposed calibration template.Finally, what is gained from the wide-angle calibration is applied to the actual measurement with large size, and the overall measurement is based on stereo vision. The images of the antenna with two different views are taken and the overall measurement is made by use of the calibration result based on stereo vision. First of all, the projection matrix of the camera is determined by the detecting and matching of coded points and the camera intrinsic parameters obtained before. And then undistorted of the marked points based on distortion parameters is made, furthermore the 3D coordinates of the marked points are obtained by stereo vision. At last, the measurement results are compared with the results obtained by the Tian Yuan photogrammetry system to prove the feasibility and practicability of the wide-angle camera calibration schemes.