Time-domain correlation image sensor: CMOS design and integration of demodulator pixels

We describe CMOS pixel design and fabrication results of the time-domain correlation image sensor, which has been proposed and studied in our laboratory, This sensor can essentially be regarded as an array of demodulators-it computes temporal correlation between incident light intensity and a global reference signal every frame. The correlation detection allows sensitivity to high frequency illumination: and makes various applications possible by using this sensor together with active sensing methods such as modulated illumination and camera motion. The prototype pixel, based on a transconductance multiplier with a photodiode current source and a pair of capacitive loads, is designed as a MOS pair with its common source and drains extended to form a phododiode and capacitors, respectively. Based on this design, 64 times 64-pixel sensors were fabricated with a 1.2-micron CMOS process. Experiments under sinusoidally modulated illumination confirmed temporal correlation performance of the fabricated sensors. Application examples such as lock-in photometry and vibrometry are also presented.