Journal of Computer Applications (计算机应用) 2013/33:12 PP.3555-3558
To carry out lens distortion correction of unknown camera parameters, a method calibrating distortion center first and distortion coefficient second was proposed. First, with target imaged at two different focal lengths, distortion center could be positioned using relative position relation of the same target points in two pictures; then according to the invariance of line perspective projection, distortion coefficient could be searched by variable step optimization method. The simulation experiment showed that the average error of distortion center was (0.224 3,0.163 6) pixel, and the distortion coefficient error was 0.28% when target point number was 25, the noise level was 0.2 pixel. Real image experiment shows that distortion center and distortion coefficient obtained by the proposed method can correct the image well. The method is easy to implement, the calibration of camera's internal and external parameters and the knowledge of line grid's world coordinates can be neglected.