Mitigating Effects of Uniform Fog on SPAD Lidars

The performance of light detection and ranging (LiDAR) degrades severely in adverse weather conditions of which fog is considered one of the worst. In this letter, fog effects on single-photon avalanche diode LiDAR are studied, and techniques to mitigate the effects caused by uniform fog are proposed. Fog mainly imposes two challenges to LiDAR in vehicular applications, namely, severe signal attenuation at long ranges and false alarms caused by fog at short ranges. Different strategies are needed to address these issues. A generalized likelihood ratio test with a constant false alarm rate threshold is proposed for target detection at low signal levels, while for reducing false alarms at short ranges, a defogging technique based on the fog-profile estimation is developed. The experimental and simulation results demonstrate the potentials and limitations of these techniques at combating fog.