A Fast 50 × 40-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
Matteo Perenzoni, Nicola Massari, Leonardo Gasparini, Manuel Moreno García, Daniele Perenzoni, David Stoppa
Abstract
A front-side illuminated array of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$50\times 40$ </tex-math></inline-formula> single-photon avalanche diode pixels for single-point distance measurement is implemented in a 0.15-mm CMOS technology, showing a pixel size of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$38.5\times 33.5\,\,\mu \text{m}^{2}$ </tex-math></inline-formula> 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 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$5\times 5$ </tex-math></inline-formula> 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 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{W}$ </tex-math></inline-formula> , 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.