Vision Sensor Calibration Method based on Flexible 3d Target and Invariance of Cross Ratio

A vision sensor calibration method based on flexible three-dimensional (3d) target and invariance of cross ratio is proposed. Flexible 3d target is obtained by moving planar target to different positions. According to the relative position relationship of planar targets in the different positions, unify target points to the base coordinate frame of the flexible 3d target. Using the invariance of cross ratio, the coordinates of the points in the light plane are obtained, then converted to sensor measurement coordinate system. Finally, vision sensor calibration parameters are obtained by the nonlinear optimization algorithm. The experimental results demonstrate that the proposed method can obtain higher calibration accuracy, reduce the calibration cost. In addition, the proposed method can adapt to field calibration for vision system.