Fisheye Lenses Calibration Using Straight-Line Spherical Perspective Projection Constraint

Fisheye lenses are often used to enlarge the field of view (FOV) of a conventional camera. But the images taken with fisheye lenses have severe distortions. This paper proposes a novel calibration method for fisheye lenses using images of space lines in a single fisheye image. Since some fisheye cameras’ FOV are around 180 degrees, the spherical perspective projection model is employed. It is well known that under spherical perspective projection, straight lines in space have to be projected into great circles in the spherical perspective image. That is called straight-line spherical perspective projection constraint (SLSPPC). In this paper, we use SLSPPC to determine the mapping between a fisheye image and its corresponding spherical perspective image. Once the mapping is obtained, the fisheye lenses is calibrated. The parameters to be calibrated include principal point, aspect ratio, skew factor, anddistortion parameters. Experimental results for synthetic data and real images are presented to demonstrate the performances of our calibration algorithm.