Modelling and Removing Radial and Tangential Distortions in Spherical Lenses

Spherical cameras are variable-resolution imaging systems and promising devices for autonomous navigation purposes, mainly because of their wide viewing angle which increases the capabilities of vision-based obstacle avoidance schemes. In addition, spherical lenses resemble the primate eye in their projective models and are biologically relevant. However, the calibration of spherical lenses for Computer Vision is a recent research topic and current procedures for pinhole camera calibration are inadequate when applied to spherical lenses. We present a novel method for spherical-lens camera calibration which models the lens radial and tangential distortions and determines the optical center and the angular deviations of the CCD sensor array within a unified numerical procedure. Contrary to other methods, there is no need for special equipment such as low-power laser beams or non-standard numerical procedures for finding the optical center. Numerical experiments, convergence and robustness analyses are presented.