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A Biologically-Motivated Gaze Control System

A gaze control system is being designed for tracking a target in three-dimensional space by a foveated active vision system modelled on human smooth pursuit and saccadic eye movements. The system consists of a fixed focal length video camera capable of pan and tilt movements. A transformation is applied to the video image to produce a foveated image having (i) a high-resolution fovea and (ii) a low-resolution peripheral area. Fixation points are then determined by computing a symmetry function on the foveated image. Real-time control of the active vision system will involve shifting the focus of attention to the point of highest symmetry. The control algorithm will consist of a single gaze-error-control loop as opposed to the usual velocity and positional error driven systems. The objective of the gaze control system is to keep the desired target centered in the image. The control law used is similar to a proportional controller having two specific gain settings. This is achieved by adding a feedforward loop known as the burst pathway containing an additional gain. When the error in position is above a predefined threshold, the burst pathway is switched on, thereby increasing the overall loop gain. When the error is below the threshold, the burst pathway is switched off, hence decreasing the loop gain. This scheme allows us to reproduce the saccadic and smooth pursuit eye movements of the human visual system.

C. Rizzuto, M.D. Levine, H. Galiana

Thierry Baron
Mon Nov 13 10:43:02 EST 1995