Range accuracy of SPAD-based time-of-flight sensors

This communication addresses the range accuracy of SPAD-based time-of-flight (TOF) sensors that employ laser pulse modulation. Two basic approaches are considered: indirect and direct TOF. We investigate confidence intervals and derive formulas for standard errors of the relative distance error for both approaches based on photon statistics.

I. Introduction

For many applications the acquisition of distance of objects in certain environment is required, which can yield 3D images. One feasible approach to determine an object distance is the time-of-flight (TOF) method which relies on determination of the travel time of a modulated laser beam. The beam is emitted by a laser, usually collocated with a light sensor, and reflected back from the object to the sensor: the elapsed time and the light velocity yield the distance information. The beam modulation can be either based on continuous-wave (CW) or pulse modulation (PM).