Removal of translation bias when using subspace methods

Given estimates of the motion field (optic flow) from an image sequence, it is possible to recover translational direction, T/spl I.oarr/, using a variety of techniques. One such technique, known as "subspace methods, generates constraints which are perpendicular to T/spl I.oarr/, so that two distinct constraints allow a solution for T/spl I.oarr/. In practice many constraints are used in a least-squares solution, but it has been observed that the recovered estimates for T/spl I.oarr/ are biased towards the optical axis. While the cause of the bias is well known, previous attempts to remove it have been flawed. This paper outlines a new method which removes the bias. The technique is simple to apply and computationally efficient.