Calibration Method for Misaligned Catadioptric Camera

This paper proposes a calibration method for catadioptric camera systems consisting of a surface of revolution mirror and a perspective camera, such as HyperOmni Vision. The proposed method is based on conventional camera calibration and mirror posture estimation. Many methods for camera calibration have been proposed. During the last decade, methods for catadioptric camera calibration have also been proposed. The main problem with catadioptric camera calibration is that the degree of freedom of mirror posture is limited or the accuracy of the estimated parameters is inadequate, owing to nonlinear optimization. On the other hand, our method can estimate the full degrees of freedom of mirror posture and is free from the volatility of nonlinear optimization. Our method uses the mirror boundary and can estimate up to four mirror postures. We apply an application of an extrinsic parameter calibration method based on conic fitting for this estimation method. Because an estimate of the mirror posture is not unique, we also propose a selection method for finding the best one. By using the conic-based analytical method, we can avoid the initial value problem arising from nonlinear optimization. We conducted experiments on synthesized images and real images to evaluate the performance of our method, and discuss its accuracy.