A CMOS 3-D imager based on single photon avalanche diode

A 64-pixel linear array aimed at 3-D vision applications is implemented in a high-voltage 0.8[micro]m CMOS technology. The detection of the incident light signals is performed using photodiodes biased above breakdown voltage so that an extremely high sensitivity can be achieved exploiting the intrinsic multiplication effect of the avalanche phenomenon. Each 38 x 180-[micro][m.sup.2] pixel includes, besides the single photon avalanche diode, a dedicated read-out circuit for the arrival-time estimation of incident light pulses. To increase the distance measurement resolution a multiple pulse measurement is used, extracting the mean value of the light pulse arrival-time directly in each pixel; this innovative approach dramatically reduces the dead-time of the pixel read-out, allowing a high frame rate imaging to be achieved. The sensor array provides a range map from 2 m to 5 m with a precision better than [+ or -] 0.75% without any external averaging operation. Moreover, with the same chip, we have explored for the first time the implementation of an indirect time-of-flight measurement by operating the proposed active pixel in the photon counting mode. Index Terms--Avalanche photodiode, laser radar, photon counting, range camera, three-dimensional (3-D) image sensor, time of flight (TOF).