A CMOS Optical Sensor System Performing Image Sampling on a Hexagonal Grid

An integrated CMOS image acquisition system suitable for retinal information processing in bionic vision systems or product inspection has been developed and tested. It supports the readout of arbitrarily user-defined subregions. The test chip incorporates 32×32 random addressable active sensor cells arranged on a hexagonal grid and on-chip control and readout electronics. It has been designed and fabricated in a standard 1.5 ¿m n-well CMOS process. The size of a single sensor cell is 38.8 ¿m × 33.6 ¿m and the total chip area is 7 mm². The sensor cells show a logarithmic response in illumination and are capable of detecting illumination variations with frequencies well above 1 MHz.