Output methods for an associative operation of programmable artificial retinas

The introduction of intelligence near each photosensitive element in focal plane arrays (FPA) leads to sensory devices-called artificial retinas-which may no longer output raw images but, rather, much more concentrated forms of information. In particular, when the on-sensor image processing facilities are powerful enough to allow some structural pattern recognition, lists of pixels of interest become an output format of choice from retina to microprocessor. This implies the development of specific output techniques and operators to be integrated in the focal plane. After an in-depth presentation of the motivations in the context of programmable artificial retinas (PAR) for robot vision, two original solutions to the problem are presented, corresponding to two different trade-offs between efficiency and VLSI implementation cost. The first one is a compact hardware solution, which allows to sense pixels of interest from the sides of the 2D pixel array. The second one, a mainly software technique, exploits the mathematical concept of de Bruijn arrays for a distributed encoding of pixel addresses on the PAR.