Self-calibration with varying focal length from two images obtained by a camera with small rotation and general translation

The stratified self-calibration approach based on the absolute conic or its dual, the absolute dual quadric, has the merit of allowing the intrinsic c amera parameters to vary while being retrieved from an image sequence. In t his paper, we show that for a camera with small rotation and general transl ation, a new linear equation resulted from the infinity homography can be a dded to a system of linear equations to compute the absolute dual quadric. Experiments with both synthetic and real images show that satisfactory resu lts can be obtained with the proposed linear approach. It is possible to fu rther improve the calibration result by adopting some nonlinear optimizatio n schemes, e.g., a suitable LM-like algorithm, to enforce the absolute dual quadric constraints using the linear solutions as an initial guess. (C) 20 01 Elsevier Science B.V. All rights reserved.