Vision Chip 2: Foveated Silicon Retina
This chip contains a 51X39 array composed of logarithmic photoreceptors and edge-detection circuits. Direction of Motion detection circuits and ON-set detection circuits are also included in each pixel instead of outside the imaging array. Centroid is computed using the On-set detectors. We have horizontal and vertical scanners to scan direction direction of motion pixel-by-pixel or group of pixels. Scanners are also used to scan the image out from each pixel.
For phototransduction, we use parasitic PNP transistors in an N-well CMOS process. The edge detection circuits uses the natural filtering properties of resistive networks to implement the Difference of Gaussian Operator.
Motion is detected using temporal differentiators(RC transient detection circuit) and correlators(AND gates). A resistive grid is used to compute the centroid by associating the position of a column(row) with an analog voltage.
The chip was fabricated in 1.2 micron technology throught MOSIS.