Effect of optical-scattering characteristics with modified kernel-based model on the triggering probability of Gm-APD

Abstract

It is not feasible to use the Geiger-mode avalanche photodiode (Gm-APD) detection model to guide detection quantitatively during daytime, because of the incompletely built echo intensity model. In this study, because the background noise and the signal light are both modulated by the target's optical-scattering characteristics (OSCs), a hybrid light-scattering model (the modified kernel-based bidirectional reflection distribution function (BRDF) model) is substituted in the laser detection and ranging (LADAR) ranging equation. In such a BRDF model, the Li-Liang-BRDF model is taken as the kernel, and the background noise equivalent intensity coefficient is employed to link the background noise part to the laser echo part. According to the results of a Gm-APD outdoor experiment, the proposed LADAR ranging equation is applicable to detection during daytime, and the noise scaling factor d(θs) is not a constant with the variation of solar zenith angle; the signal intensities in the theoretical and experimental results only exhibit a difference of 5%. The effects of various factors (e.g., solar zenith angle, LADAR observation angle, and different target materials) on the echo signal-to-noise ratio and triggering probability are analyzed by the proposed LADAR ranging equation. Moreover, a maximum-likelihood estimation-based theoretical method is proposed to calculate the maximum detection range during daytime. Subsequently, the change law of the detection range in daytime is analyzed, and the calculated detection range of the developed Gm-APD LADAR reaches 3.5 km under an actual daytime background. This study can provide theoretical support and formulates several strategies for Gm-APD detection in daytime. Furthermore, novel ideas can be proposed to calculate theoretically the effective detection range of Gm-APD LADAR.