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&oarr;, using a variety of techniques. One such technique, known as “subspace methods, generates constraints which are perpendicular to T&oarr;, so that two distinct constraints allow a solution for T&oarr;. In practice many constraints are used in a least-squares solution, but it has been observed that the recovered estimates for T&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