Sunlight-proof optical distance measurements with a dual-line lock-in time-of-flight sensor

This work describes time-of-flight distance measurements with a line sensor based on the correlation principle. It is capable of suppressing maximum bright sunlight and even more electronically in each pixel autonomously without using any optical filters. The optical fill factor of a pixel is 58% embodying a 100 × 100 μm2 photodiode. Working principle of the pixel circuit and the mechanism for suppression of ambient illumination as well as physical limitation of accuracy are discussed. Characterizations of the single-pixel performance with 650 nm laser and 850 nm LED sources with optical output powers of 1 mW and 900 mW, respectively, are presented. Finally, measured characteristics of the line sensor for distances up to 3.2 m are shown. The standard deviation is below 2 cm up to 1.2 m at a measurement time of 50 ms per distance point and the near-infrared LED illumination.