A foveated AER imager chip [address event representation]

Abstract

We have developed a foveated imager chip with high resolution photo-cells (referred to as static pixels) in the center that are surrounded by more space consuming adaptive change detection pixels (referred to as dynamic pixels). Inspired by the neurons of biological nervous systems, they emit short voltage pulses, the static pixels with a frequency proportional to light intensity, the dynamic pixels whenever they detect a relative change in irradiance. The pulses are transmitted off-chip by the address event representation (AER) protocol, i.e. via a digital bus as the identifying address of the sending pixel. For the motion pixels, this read-out strategy has the advantage of low latency in the order of 100 ns after a change is encountered. (Whereas a scanning read-out strategy would on average suffer a delay of half of the frame scanning period.) Mounted on a pan-tilt system, the peripheral motion detectors could, for instance, be used to steer the imager such that the image of a moving object falls onto the central pixel array where it can then be examined in detail at a higher resolution. Or, if the imager is mounted statically, they can detect an intruder and cause the central pixels to be turned on for more detailed observation