A Far-Range Off-line Camera Calibration Method for Stereo Lane Detection Systems

A far-range camera calibration method for vision sensors used in automatic lane detection systems is investigated. Autonomous vehicle guidance based on stereo image acquisition requires the knowledge of the camera parameters, such as camera position, orientation, lens distortion, focal length etc. with high precision. Calibration is performed by placing markers in known positions in front of the vehicle holding the camera(s) and by detecting the location of their images in the acquired snapshots. The parameters are then estimated by minimizing the geometric error in the image. Most of the methods discovered in the literature do not consider errors in the measurement of marker locations. However, a precise marker arrangement for far-range calibration might be expensive to set up. This paper shows that imprecision in the 3D location of the markers can not be tolerated in some practical situations and in such cases, a different optimization is proposed in the calibration of the extrinsic camera parameters (camera position and orientation). A position estimation method is also shown to extract marker positions from far-range laser distance meter measurements. The estimated marker positions are corrected by considering aiming errors, as well. Parameter errors are also estimated. It will be shown that our new calibration and optimization method is expected to result a good accuracy compared to commercial methods.