SPAD LiDAR from Chinese Academy of Science

Acta Photonics Sinica publishes a paper "A 16×1 Pixels 180nm CMOS SPAD-based TOF Image Sensor for LiDAR Applications" by CAO Jing, ZHANG Zhao, QINan, LIU Li-yuan, and WU Nan-jian.

"The sensor integrates 16 structure-optimized single photon avalanche diode pixels and a dual-counter-based 13-bit time-to-digital converter. Each pixel unit has a novel active quench and recharge circuit. The dark noise of single photon avalanche diode is reduced by optimizing the guard ring of the device. The active quench and recharge circuit with a feedback loop is proposed to reduce the dead time. A dual-counter-based time-to-digital converter is designed to prevent counting errors caused by the metastability of the counter in the time-to-digital converter. The sensor is fabricated in 180 nm CMOS standard technology. The measurement results show the median dark count rate of the single photon avalanche diode is 8 kHz at 1 V excess voltage, the highest photon detection efficiency is 18% at 550 nm light wavelength. The novel active quench circuit effectively reduces the dead time down to 8 ns. The time-to-digital converter with 416 ps resolution makes the system achieve the centimeter-accuracy detection. A 320×160 depth image is captured at a distance of 0.5 m. The maximum depth measurement nonlinear error is 1.9% and the worst-case precision is 3.8%."