A single-chip CMOS visual orientation sensor

We present a single-chip, low-power vision sensor capable of measuring local edge orientation across a wide field of view. The sensor was fabricated in a 0.5-μm CMOS process. Quadratic spatial filters were implemented using differential pairs and an "antibump" circuit to give a current-mode output signal. Small spatial filters requiring only nearest-neighbor connectivity were used for edge detection. The sensor is able to detect its orientation relative to the dominant horizontal and vertical edges in indoor, man-made environments. This sensor consumes only 120 μW of power and could be used to control the attitude of an autonomous agent in an indoor environment.