A Three-Phase, One-Tap High Background Light Subtraction Time-of-Flight Camera

Abstract

In this paper, a time-of-flight 3-D camera is presented for indoor/outdoor high-speed applications. A three-phase algorithm is proposed using one-tap/capacitor in-pixel background light subtraction. By integrating the background light only once, the standard four-phase time-of-flight operation is done in three-phases. The use of a single tap in the proposed pixel provides background light subtraction with lower mismatch and additionally, increases the camera speed. A $24 \times 24 $ pixel array image sensor, fabricated in AMS 0.35- $\mu \text{m}$ CMOS process is characterized in 2-D and 3-D mode for background light subtraction and distance estimation. The pixel pitch is $48~\mu \text{m}$ with 17.36% fill-factor. The sensor subtracts 125-klx background light with 8.2-cm distance offset at 80-cm object distance, without using an optical filter. The background-to-signal-ratio is 32.04 dB while frame-rate of the camera is 207 and 100 fps in 2-D and 3-D mode, respectively.