Calibrating central catadioptric cameras based on spatial line projection constraint

Catadioptric imaging systems are widely used in many applications such as robot navigation, surveillance or 3D reconstruction due to their large field of view. However, the catadioptric image has a larger deformation than the perspective image, which makes catadioptric camera calibration more difficult. Previous approaches using lines need conic fitting, which is a hard work for catadioptric images. This paper proposes a nonlinear method based on the constraint from the projection of a space line. A simple and intuitive estimate of the initial camera parameters is also presented, which can be used in some applications without requirement for high accuracy. The proposed method needs no conic fitting that highly affects the calibration accuracy. The validity of the proposed approach is shown by experiments.