Ranging performance model considering the pulse pileup effect for PMT-based photon-counting lidars

Currently, the ranging performance model for a photomultiplier tube (PMT)-based photon-counting lidar assumes the dead time is a fixed value for simplicity. This assumption introduces a bias in evaluating the ranging performance for a given PMT-based lidar because the dead time of PMTs is actually changeably caused by the pulse pileup effect. In this paper, the changeable dead time is calculated by a new empirical equation based on the Monte Carlo simulation. The empirical equation of the dead time is then used to derive the ranging performance model for PMT-based PC lidar systems. The proposed model is verified by an experimental lidar system equipped with a PMT and utilized to quantitatively analyze the influence of factors, such as the noise rate, discrimination threshold, signal intensity, and receiving pulse width. The result indicates that the receiving pulse width has a major influence, and when it exceeds 10 ns, the pulse pileup effect will introduce biases of more than 5 cm if the conventional model (ignoring the pulse pileup effect) is used. For a spaceborne lidar at an altitude of several hundred kilometers, the receiving pulse width will be significantly stretched when lasers illuminate on sloping surfaces, e.g., for a sloping surface larger than 2 degrees, so the effect of pulse pileup effect will have to be taken into consideration.