A camera calibration technique based on plane square

A technique for camera calibration based on plane square is proposed. It only requires the camera to observe a plane square which consists of four points at two (or more) different unknown orientations. Either the camera or the plane square can be freely moved and the motions need not be known. Only using, four points in the model plane and the proposed closed-form solution, the intrinsic and extrinsic parameters of camera can be calculated. At the last of the paper, real data is used to test the proposed technique. Compared with the classical techniques with expensive calibration pattern, the proposed technique is easy to understand and can be used where camera calibration is often needed. The speed of calculation is robust and fast for its fewer points.