Active estimation of distance in a robotic system that replicates human eye movement

In a moving agent, the different apparent motion of objects located at various distances provides an important source of depth information. While motion parallax is evident for large translations of the agent, a small parallax also occurs in most head/eye systems during rotations of the cameras. A similar parallax is also present in the human eye, so that a redirection of gaze shifts the projection of an object on the retina by an amount that depends not only on the amplitude of the rotation, but also on the distance of the object with respect to the observer. This study examines the accuracy of distance estimation on the basis of the parallax produced by camera rotations. Sequences of human eye movements were used to control the motion of a pan/tilt system specifically designed to reproduce the oculomotor parallax present in the human eye. We show that the oculomotor strategies by which humans scan visual scenes produce parallaxes that provide accurate estimation of distance. This information simplifies challenging visual tasks such as image segmentation and figure/ground segregation. c © 2006 Elsevier B.V. All rights reserved.