A 256 x 256 compact cmos image sensor with on-chip motion detection function

A 256×256 CMOS passive pixel image sensor with especially equipped simple switches, which enables motion detection, is implemented. Each pixel consists of a simple combination of a photodiode and an address switch. Photocharge generated at each pixel is converted to voltage by means of a column charge amplifier array, and motion detection has been realized with utilizing the photodiode as a frame memory. Its output is transformed to a digital value with a 128 array 8-bit analog-to-digital (A/D) converter. Simultaneously, fixed pattern noise is suppressed by utilizing A/D conversion as the CDS circuit. Due to its simple structure, more than 70% fill factor ratio has been realized. The extracted motion detection results can be displayed digitally at 128 frames per second by means of 128 A/D converter arrays.