BRDF invariance and detector nonlinearity in photon-counting LiDAR measurements

Bidirectional reflectance distribution function (BRDF) measurements using photon-counting LiDAR provide an effective approach for characterizing weakly reflecting and long-range targets. A 1064 nm photon-counting LiDAR system was developed to investigate the influence of photon flux on BRDF measurements. A nonlinear response model of the single-photon detector was established, and a saturation limit of approximately 0.6 photons/pulse was experimentally confirmed. The results show that the measured BRDF remains unchanged when the peak return photon count is below half of the saturation threshold, while extremely low photon flux introduces slight deviations due to background noise. At higher photon fluxes, detector dead-time effects cause BRDF peak suppression without altering the peak position or width. These results establish the practical operating boundary for photon-counting BRDF measurements.