Calibration method for the relative orientation between the rotation axis and a camera using constrained global optimization

This paper proposes a novel method for calibrating the relative orientation of a camera fixed on a rotation axis using the constrained global optimization algorithm. Because the camera cannot directly 'see' the rotation axis, the calibration procedure uses two checkerboards and another camera with a large viewing-angle. One small checkerboard is rotated with the camera to determine the rotation axis; the other large checkerboard calibrates the relative orientation of the two cameras. The determined rotation axis and the obtained optical axis of the calibrated camera can be represented in the same camera coordinate system, so that we can calculate their relative orientation. In our experimental results, the mean squared error of the angle between the rotation axis and the optical axis of the calibrated camera was 0.027°. Under the given conditions, the two checkerboards and the camera can be randomly placed. Therefore, the proposed calibration method is flexible, effective, and very accurate. (paper)