Abstract:

Single-photon lidar (SPL) measures the time delay between a laser pulse emission and a single9 photon detection. SPL typically uses a periodic sequence of illumination pulses to improve the10 accuracy of distance estimates, and the radial velocity of a moving target can also be determined11 from the Doppler shift in the pulse repetition frequency. Although increasing the repetition12 frequency increases the photon detection rate, it also decreases the unambiguous range. Several13 alternative pulsing modes have been proposed to break this tradeoff for SPL measurements of14 static scenes, e.g., using multiple repetition rates or random pulse trains to yield both high count15 rates and a long unambiguous range. In this work, we show that velocity can still be estimated16 despite the use of non-periodic range extension pulse patterns. We derive a general model for the17 photon acquisition process with a moving target and propose maximum likelihood estimators18 (MLEs) to recover the distance, velocity, and photon flux levels. Each range extension mode19 requires a tailored initialization scheme in order for our MLE solver to converge to the global20 optimum. We demonstrate through simulations and experiments that non-periodic SPL can21 simultaneously achieve long-range and high-accuracy distance and velocity estimates.