Polarisation-modulated photon-counting 3D imaging based on a negative parabolic pulse model.

Abstract

Indirect methods based on intensity for time-of-flight measurement have attracted considerable research interest in recent years because they can provide high spatial resolution in 3D imaging. However, the majority of indirect methods are inapplicable when echo signals are small (e.g., less than one photon). We propose a novel polarisation-modulated photon-counting 3D imaging method based on a negative parabolic pulse model (NPPM) to solve this problem. We measure weak signals using the number of received photons after repetitive pulsed laser emission. We establish a computational method by exploring the relationship between photon flight time that corresponds to the polarisation-modulated state of photons controlled by phase shift and calculated photon rates from received photon-counting values based on Poisson negative log-likelihood function to calculate the distance. We specifically utilise the NPPM to estimate distribution of echo signals and reduce ranging error given that echo signals are constantly time-varying. We build the first experimental system for polarisation-modulated photon-counting 3D imaging for verification by integrating it with a dual-axis galvo scanning device. Experimental results demonstrate that the proposed method can achieve ranging accuracy at the millimeter-level and exhibit superior 3D imaging performance even when the average received number of echo signals per pulsed laser emission is smaller than 0.05.