Depth perception in an anthropomorphic robot that replicates human eye movements

In the eyes of many species, the optical nodal points of the cornea and lens do not lie on the axes of rotation of the eye. During eye movements, this lack of alignment produces depth information in the form of an oculomotor parallax. That is, 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 of the eye, but also on the distance of the object with respect to the observer. Species as diverse as the chameleon and the sandlance critically rely on this depth cue to estimate distance. An oculomotor parallax is present also in the human eye and, during natural eye movements, it produces retinal shifts that are well within the range of sensitivity of the human visual system. We have developed an anthropomorphic robot equipped with a pan/tilt head specifically designed to reproduce the oculomotor parallax present in the human eye. We show that replication of sequences of human eye movements with this robot produces accurate estimation of distance. In robotic vision it is often debated whether the dynamic analysis of a visual scene by means or a mobile camera presents advantages with respect to the static analysis provided by a stationary camera with a wide field of view. This study shows that by generating depth information, replication of the dynamic strategy by which humans scan a visual scene greatly facilitates the processes of figure/ground segregation and image segmentation, two of the hardest tasks of machine vision.