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A CMOS SPAD Imager with Collision Detection and 128 Dynamically Reallocating TDCs for Single-Photon Counting and 3D Time-of-Flight Imaging

1
Quantum and Computer Engineering, Delft University of Technology, Mekelweg 4, 2628CD Delft, The Netherlands
2
Biomedical Optics Research Laboratory, University of Zurich, Rämistrasse 71, 8006 Zürich, Switzerland
3
Advanced Quantum Architecture Laboratory, École Polytechnique Fédérale de Lausanne (EPFL), Route Cantonale, 1015 Lausanne, Switzerland
4
Kavli Institute of Nanoscience, 2628CJ Delft, The Netherlands
*
Author to whom correspondence should be addressed.
These authors contributed equally to this work.
Sensors 2018, 18(11), 4016; https://doi.org/10.3390/s18114016
Received: 5 October 2018 / Revised: 14 November 2018 / Accepted: 15 November 2018 / Published: 17 November 2018
(This article belongs to the Special Issue The International SPAD Sensor Workshop)
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Abstract

Per-pixel time-to-digital converter (TDC) architectures have been exploited by single-photon avalanche diode (SPAD) sensors to achieve high photon throughput, but at the expense of fill factor, pixel pitch and readout efficiency. In contrast, TDC sharing architecture usually features high fill factor at small pixel pitch and energy efficient event-driven readout. While the photon throughput is not necessarily lower than that of per-pixel TDC architectures, since the throughput is not only decided by the TDC number but also the readout bandwidth. In this paper, a SPAD sensor with 32 × 32 pixels fabricated with a 180 nm CMOS image sensor technology is presented, where dynamically reallocating TDCs were implemented to achieve the same photon throughput as that of per-pixel TDCs. Each 4 TDCs are shared by 32 pixels via a collision detection bus, which enables a fill factor of 28% with a pixel pitch of 28.5 μm. The TDCs were characterized, obtaining the peak-to-peak differential and integral non-linearity of −0.07/+0.08 LSB and −0.38/+0.75 LSB, respectively. The sensor was demonstrated in a scanning light-detection-and-ranging (LiDAR) system equipped with an ultra-low power laser, achieving depth imaging up to 10 m at 6 frames/s with a resolution of 64 × 64 with 50 lux background light. View Full-Text
Keywords: single-photon avalanche diode; SPAD; time-of-flight; dynamic reallocation; time-to-digital converter; collision detection bus; image sensor; light detection and ranging; LiDAR single-photon avalanche diode; SPAD; time-of-flight; dynamic reallocation; time-to-digital converter; collision detection bus; image sensor; light detection and ranging; LiDAR
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).
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Zhang, C.; Lindner, S.; Antolovic, I.M.; Wolf, M.; Charbon, E. A CMOS SPAD Imager with Collision Detection and 128 Dynamically Reallocating TDCs for Single-Photon Counting and 3D Time-of-Flight Imaging. Sensors 2018, 18, 4016.

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