A hyperacute optical position sensor based on biomimetic retinal micro-scanning

Abstract

Here we describe an active visual process whereby biomimetic micro-movements applied to an artificial retina improve the performances of a visual sensor in terms of both its detection sensitivity and its acuity. The elementary visual scanning sensor described here can detect a thin contrasting bar placed 2.5 m ahead, giving a minimum visibile (i.e., the smallest object width distinctly perceivable by the sensor) which is about 8-fold finer than the pixel angular pitch. In addition, the visual sensor is endowed with hyperacuity as it can locate a contrasting edge with a resolution which is 70-fold greater than its static resolution (i.e., the resolution without scanning). This high-resolution position sensing performance is based on encoding an angular position by an angular speed. The latter is then measured by a motion sensor inspired by those of the housefly. The retinal scanning process is generated by a piezo bender actuator driven at a frequency of 10 Hz by a tiny 1.5-g piezo driver. The small size, small mass and low power consumption of our visual scanning sensor make it well suited for a number of applications in fields ranging from mobile robotics to metrology and space technology, where the high-resolution contactless position sensing of naturally contrasting features is of prime importance.