A vision sensor with on-pixel ADC and in-built light adaptation mechanism
In this paper we propose an on-pixel Analogue-to-Digital Converter (ADC) based on pulse frequency modulation (PFM) scheme. This PFM based converter presents a viable solution for pixel-level based ADC. It uses a simple and robust circuit that can be implemented in a compact area resulting in a 23% fill-factor for a digital vision sensor in 0.25?m CMOS technology. An in-built light adaptation mechanism has also been implemented which allows the sensor to better adapt to low-light intensity or to adjust the sensor saturation level. As a consequence, the proposed sensor features a programmable dynamic range. Image lag is eliminated since a reset of the photodetector is performed after the conversion period. A prototype comprising a 3232 pixel array has been implemented in CMOS 0.25?m technology. Each pixel occupies an area of 4545?m2 with an average power consumption of 85?W per pixel.
light adaptation pulse frequency modulation cmos vision sensors cmos imagers vlsi