A Fast 50x40-Pixels Single Point DTOF SPAD Sensor with Photon Counting and Programmable ROI TDCs, with σ<4 mm at 3 m up to 18 klux of Background Light

A front-side illuminated array of 50×40 single-photon avalanche diode pixels for single-point distance measurement is implemented in a 0.15-mm CMOS technology, showing a pixel size of 38.5×33.5μm2 with variable fill factor from 4.8% to 15.3%. In order to improve the signal to background ratio, the sensor embeds a procedure for on-the-fly identification of the laser spot position in the active area. A programmable 5×5 region-of-interest can be connected, through a reconfigurable switching matrix, to 25 time to digital converters (TDCs) with 11-bit and 48-ps resolution for timing measurement. Thanks to the adopted approach, the detector, working with a 650-nm pulsed laser with an average power of just 40 μW , can reliably measure up to 7.5 m achieving a best precision lower than 1.6 mm at 3 m and working under 7 klux background at 1-kHz rate. The sensor is shown to work up to 18 klux of background light with best precision lower than 4 mm at 3 m.