Robust Lidar against Environment Variation

Kyihwan Park
Gwangju Inst. of Science and Technology, South Korea

Keywords: Lidar, avalanche photodetecor, temperature variation, time-of-flight sensor, distnace accuracy improvement

Recently, a time-of-flight based 2D and 3D LiDAR expands their applications to several industries thanks to high-precision measurement over a long distance at outdoor environments. Avalanche photodetectors (APDs) are commonly used for LiDARs because of the high internal gain which amplifies significantly a measured signal. However, the magnitude of the measured signal changes severely against temperature variation due to temperature dependent characteristics of the APD. One method is to maintain a constant temperature of a photodetector by using a thermoelectric cooler. Although this is the most fundamental method to solve the problem, it has a disadvantage of complex hardware configuration. Another method is to maintain a constant SNR of a photodetector by adjusting its reverse bias voltage using a pre-determined relation between the reverse bias voltage and temperature. However, since this method is feed-forward control, the temperature compensation cannot be perfect due to the uncertainty error between the reverse bias voltage and temperature relation.In this paper, a temperature compensation method using signal-to-noise ratio (SNR) feed-back control is proposed to solve the problem, in which a proper bias voltage of the APD is adjusted for temperature change. This method has an advantage of a simple configuration of hardware.