A new easy calibration algorithm for para-catadioptric cameras

In this paper, a new easy calibration method for para-catadioptric cameras is proposed. We derive a nonlinear constraint on all camera intrinsic parameters from the projections of any three collinear space points on the viewing sphere. With the principal point known, the constraint becomes linear on all other intrinsic parameters which are the effective focal length, the aspect ratio and the skew, so the three parameters can be estimated linearly by using SVD. The principal point can be well determined from the bounding ellipse of the catadioptric image in real applications. Unlike approaches using lines in literature, the proposed method needs no conic fitting, which is hard to accomplish and highly affects the accuracy of the calibration. Experiments on simulated and real data show this method is robust and effective.