IMPLICIT AND EXPLICIT CAMERA CALIBRATION - THEORY AND EXPERIMENTS

By implicit camera calibration, we mean the process of calibrating a c amera without explicitly computing its physical parameters. Implicit c alibration can be used for both three-dimensional (3-D) measurement an d generation of image coordinates. In this paper, we present a new imp licit model based on the generalized projective mappings between the i mage plane and two calibration planes. The back-projection and project ion processes are modelled separately to ease the computation of disto rted image coordinates from known world points. A set of constraints o f perspectivity is derived to relate the transformation parameters of the two calibration planes. Under the assumption of the radial distort ion model, we present a computationally efficient method for explicitl y correcting the distortion of image coordinates in frame buffer witho ut involving the computation of camera position and orientation. By co mbining with any linear calibration techniques, this method makes expl icit the camera physical parameters. Extensive experimental comparison of our methods with the classic photogrammetric method and Tsai's met hod in the aspects of 3-D measurement (both absolute and relative erro rs), the prediction of image coordinates, and the effect of the number of calibration points, is made using real images from 15 different de pth values.