THE ROLE OF FIXATION IN VISUAL-MOTION ANALYSIS

How does the ability of humans and primates to fixate at environmental points in the presence of relative motion help their visual systems i n solving various tasks? To state the question in a more formal settin g, we investigate in this article the following problem: Suppose that we have an active vision system, that is, a camera resting on a platfo rm and being controlled through motors by a computer that has access t o the images sensed by the camera in real time. The platform can move freely in the environment. If this machine can fixate on targets being in relative motion with it, can it solve visual tasks in an efficient and robust manner? By restricting our attention to a set of navigatio nal tasks, we find that such an active observer can solve the problems of 3-D motion estimation, egomotion recovery, and estimation of time- to-contact in a very efficient manner, using as input the spatiotempor al derivatives of the image-intensity function (or normal flow). Fixat ion over time changes the input (motion field) in a controlled way and from this change additional information is derived making the previou sly mentioned tasks easier to solve.