Improvement of detection probability and ranging performance of Gm-APD LiDAR with spatial correlation and adaptive adjustment of the aperture diameter

Abstract Gm-APD (Geiger-mode avalanche photodiode) is widely used in the LiDAR (Light detection and ranging) system for its excellent photon detection capability. The triggering probability of Gm-APD is closely dependent on the absolute intensity and the signal-to-noise ratio (SNR) of the echo, which limits the detection results in the daytime. In order to improve target's detection probability under a limited amount of statistics in the daytime, it proposed a detection scheme by using the spatial correlation and adaptive adjustment of the aperture diameter (AAAD) to achieve optimal target detection results in the daytime, besides, a MLE (Maximum Likelyhood Estimation) based ranging walk-error correction method was also put forward for the limited number of measurement. Firstly, considering the strategies of AAAD and spatial correlation, as well as the LiDAR ranging equation and Poisson triggering probability model, the detection probability model and ranging performance model of the scheme of spatial correlation and AAAD were built in this paper. Subsequently, the detection probability and ranging performance of the proposed scheme were theoretically analyzed, besides, a ranging walk-error correction strategy was put forward based on the MLE method. The theoretical analysis results showed that the proposed detection scheme could increase the utilization of echo photons and improve the amount of echo's triggering statistics; moreover, the Monte Carlo simulation results showed that in the case of a limited amount of statistics, the target detection scheme and ranging walk-error correction strategy could effectively improve the target detection probability and obtain a smaller ranging walk-error than the traditional detection scheme. Finally, the Gm-APD LiDAR was used to experimentally verify the proposed scheme, and the results showed that the scheme could effectively improve the echo's triggering probability with 400 measurements; the indoor experiment showed that the triggering probability could be improved by 7.54 times at most for white wall, and the white wall's target restoration ratio could reach 100% which was enhanced by more than 100%; besides, the outdoor experiment in the daytime showed that the target's restoration ratio could reach 75.54% and 99.45% for two investigated regions which were enhanced by 659.2% and 57.4%. Moreover, a high ranging accuracy could be maintained through ranging walk-error correction strategy, ranging walk-errors of -9mm, 12mm and 14mm under 400 measurements were achieved for white wall, concrete slab and black paper respectively. It effectively improved the ranging performance compared with the traditional detection scheme, and it completely satisfied the far-range detection. This paper can provide effective solutions for laser detection and ranging with Gm-APD in the daytime.