A single-photon-avalanche-diode 3D imager

This paper describes the design and characterization of a 64-pixel array exploiting the high sensitivity offered by single photon avalanche diodes, fabricated in a conventional high-voltage 0.8μm CMOS technology, and aimed at three dimensional measurements using the time-of-flight technique. The detection of the incident light signals is performed using a photodiode biased above its breakdown voltage so that an extremely high sensitivity can be achieved exploiting the intrinsic multiplication effect of the avalanche phenomenon. A single photon avalanche diode and dedicated read-out electronics for the arrival-time estimation of incident light pulses have been implemented in a 38×180-μm² pixel. 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 2m to 5m with a precision better than μm 0.75% without any external averaging operation.