Improvement of saturation characteristics of a frequency-demodulation CMOS image sensor

This paper demonstrates improvement of image quality in a frequency-demodulation CMOS image sensor. We have already demonstrated fundamental characteristics of a frequency-demodulation function but the sensor shows relatively poor saturation characteristics due to a crosstalk effect. By introducing sweeping out residual carriers in a photogate and discharging them into an overflow drain, a fabricated image sensor using a standard 0.6 mum CMOS technology exhibits better saturation characteristics. The output at the saturation region increases 30 times larger than the original one.