“…The intrinsic parameters describe the camera's imaging geometric characteristics, and the extrinsic parameters represent the camera's orientation and position with respect to the world coordinate system. Many approaches to camera calibration have been proposed and they can be classified into two categories: using calibration objects [6,13,16,11,1,2,8,12,14,15], and self-calibration [7,5,9]. As we know, the occluding contour of a sphere is projected to a conic in the perspective image [1,2,5,12,14].…”