A small-sized panoramic scanning visual sensor inspired by the fly's compound eye

In this paper we investigate the feasibility of the design of a small artificial compound eye that comprises micro-optical, micro-mechanical components and additional electronics for visual processing. The hybrid integration of this "mini-sensor" addresses important issues such as mechanic scale-effect, assembly of small parts and functional testing. It was recently discovered that the fly's retina undergoes repetitive scanning vergence movements([1]). The use of retinal scanning for the perception of visual motion is highlighted in the design of a small-sized horizontal array with a scanning retina of 2x30 photoreceptor elements (R-eye= 30 mm). The scanning motion is achieved by actuating the photodiode arrays with a piezoelectric bimorph cantilever beam coupled to a plate spring: the system can be brought to a resonant mode at 100 Hz (scanning amplitude > 80 mu m) under low voltage (Delta V =30V). The mini-compound eye, equipped with analogue Motion Detecting circuits, is able to guide the steps of a small mobile platform and perform multi-task visual processing for obstacle avoidance, tracking and pursuit of visual target. The visual sensor is a first step in the evaluation of the design and development of a micro-visual system whose size will eventually approach the size of the fly's compound eye (facet, phi =30 mu m, R-eye = 500 mu m).