A foveated silicon retina for two-dimensional tracking

A silicon retina chip with a central foveal region for smooth-pursuit tracking and a peripheral region for saccadic target acquisition is presented. The foveal region contains a 9 x 9 dense array of large dynamic range photoreceptors and edge detectors. Two-dimensional direction of foveal motion is computed outside the imaging array. The peripheral region contains a sparse array of 19 x 17 similar, but larger, photoreceptors with in-pixel edge and temporal ON-set detection. The coordinates of moving or flashing targets are computed with two one-dimensional centroid localization circuits located on the outskirts of the peripheral region. The chip is operational for ambient intensities ranging over six orders of magnitude, targets contrast as low as 10%, foveal speed ranging from 1.5 to 10K pixels/s, and peripheral ON-set frequencies from <0.1 to 800 kHz. The chip is implemented in 2-mu m N well CMOS process and consumes 15 mW (V dd = 4 V) in normal indoor light (25 mu W/cm(2)). It has been used as a person tracker in a smart surveillance system and a road follower in an autonomous navigation system.