Time-of-flight chip in standard CMOS technology with in-pixel adaptive number of accumulations

摘要

This paper introduces a Time-of-Flight sensor of 50 × 60 pixels in standard CMOS 0.18 μm technology with in-pixel adaptive number of accumulations and background suppression. Background suppression is carried out through two mechanisms, namely, the increase of signal to background ratio, and background subtraction. The pixel features a fill factor of 77% with an nwell over p-substrate diode of 50 × 50 μm2. The pixel senses the photocurrent through a transimpedance amplifier. Adaptive accumulations are performed with an in-pixel comparator that is also used for per-column A/D conversion as part of an 8-bit single-slope ADC. The sensor works with 4 square pulses of 50 ns. Simulations show that the chip could measure distances up to 7.5 m without optical filters for background levels up to 20 klux at video frame rate.