Calibrating a paracatadioptric camera by the property of the polar of a point at infinity with respect to a circle.

Two methods are presented for calibrating a paracatadioptric camera. A sphere in 3D space is projected to two parallel circles on which two tangents of a point and its antipode are parallel on the unit viewing sphere and intersect at the point at infinity. The direction of the polar of the point at infinity is orthogonal to the direction of the point at infinity with respect to the circle. The imaged circular points and orthogonal vanishing points can be obtained to solve the intrinsic camera parameters. Simulations and real data were used to demonstrate the effectiveness of the two algorithms.