The question of accuracy in camera calibration and a novel technique for estimating camera geometry

Machine Vision is one of the leading technologies of the present era. The quest for the best solution to the geometrical camera calibration has been a research problem for many years in the Computer/Machine Vision communities. In the field of machine vision, camera calibration refers to the experimental determination of a set of parameters which describe the image formation process for a given analytical model of the machine vision system. A complete set of calibration parameters includes both the intrinsic parameters that describe the lens-camera-frame grabber combination as well as the extrinsic parameters that relate the position and orientation of the camera to a fixed reference frame. An accurate, reliable calibration procedure is essential for most industrial machine vision applications including mechanical metrology, robot assembly, reverse engineering, tracking, image fusion etc. One of the most systematic calibration procedures for 3-D machine vision applications was proposed by Heikkila in which a comprehensive set of camera parameters is automatically evaluated by observing a calibration target consisting of two perpendicular planes, each with 256 circular control points. Other similar techniques employ a checkerboard pattern as a target and use the vertices of the squares as control points. While these techniques are sound from a theoretical point of view, they do not adequately speak to the question of measurement accuracy. This study addresses the problems associated with geometric camera calibration using the Design of Experiments as well as the question of accuracy. The broad use of camera calibration in the field of machine vision and computer vision is the primary motivation for understanding the major factors that influence the accuracy of camera calibration as well as the accuracy that can be achieved within the practical limits of most research environments. Based on the results of this study, a new approach towards camera calibration is also proposed in which image center and focal length are calculated independently of the lens distortion