Self-calibration with varying focal length from two images obtained by a stereo head

The self-calibration approach based on the absolute conic or its dual, the absolute dual quadric, has the merit of allowing the intrinsic camera parameters to vary in image sequence. In this paper, we show that certain linear equations resulting from the in2nity homography can be added to a system of originally undetermined linear equations to 2nd the absolute dual quadric for a stereo head. The special stereo con2gurations considered here allow one camera to rotate around either one or two of the coordinate axes de2ned by another camera. Experiments with synthetic images show that satisfactory results can be obtained with only the proposed linear methods. For real images obtained with non-ideal stereo con2gurations, and possibly with measurement noises, results obtained from the proposed linear methods may serve as reasonable initial guesses for some non-linear optimization procedure.? 2002 Pattern Recognition Society. Published by Elsevier Science Ltd. All rights reserved.