Wide-angle camera distortions and non-uniform illumination in mobile robot tracking,” Int.pdf

Robotics and Autonomous Systems 46 (2004) 125–133 Wide-angle camera distortions and non-uniform illumination in mobile robot tracking Gregor Klanc?ar ? , Matej Kristan, Rihard Karba Laboratory of Modelling, Simulation and Control, Faculty of Electrical Engineering, University of Ljubljana, Tr?a?ka 25, SI-1000 Ljubljana, Slovenia Received 15 January 2003; received in revised form 15 May 2003 Abstract In this paper some fundamentals and solutions to accompanying problems in vision system design for mobile robot tracking are presented. The main topics are correction of camera lens distortion and compensation of non-uniform illumination. Both correction methods contribute to vision system performance if implemented in the appropriate manner. Their applicability is demonstrated by applying them to vision for robot soccer. The lens correction method successfully corrects the distortion caused by the camera lens, thus achieving a more accurate and precise estimation of object position. The illumination compensation improves robustness to irregular and non-uniform illumination that is nearly always present in real conditions. ? 2003 Elsevier B.V. All rights reserved. Keywords: Computer vision; Camera calibration; Non-uniform illumination correction; Mobile robots tracking 1. Introduction Many possible ways exist of detecting moving objects using colour cameras. Sargent et al. [13] de- veloped a fast real-time vision system with the aid of a special hardware accelerated system, which only makes sense when software optimisations or acceler- ations are not possible. More reliable vision tracking of moving objects can be achieved by using robust statistics and probability distributions. A good ex- ample of the latter is given in the colour-based face tracking implemented by Bradski [2]. Bruce et al. [3] suggested a fast vision system for mobile robots by means of efficient colour segmentation and a two-pass connected region determination algorithm. ? Corresponding author. Tel.: