Color-coded pattern for non metric camera calibration

Non-metric camera calibration is the art of modeling the geometry of the image formation process using only qualitative constraints rather than the metric knowledge of the scene. In this paper we present a new color-coded calibration pattern, specifically designed for non-metric calibration. It embeds two bundles of orthogonal lines in two different color channels granting a two major advantages. Each image containing such a pattern naturally carries all the geometrical constraints needed for the calibration process, while the complexity of the pattern detection is reduced by decoupling the recovery of the two line bundles in two independent processing phases. Furthermore, we present an analysis of the displacement between corresponding lines detected in the color channels and in the grayscale image and propose a simple technique, based on a revised version of the Inverse Compositional Algorithm (ICA), as a solution for this issue. The performance of the proposed pattern was evaluated using the datasets, captured with a wide angle lens camera. The results suggest, that the use of a color-coded calibration pattern not only significantly reduces the amount of required user interaction, but also helps to achieve a high accuracy camera calibration, providing an important contribution to the integration of a fully automatic camera calibration tool.