Correction method for walk error based on the shape of reflective surface in LiDAR

Abstract

Walk error produced in light detection and ranging (LiDAR) based on the time-of-flight (TOF) leads to loss of ranging accuracy. Walk error, which is systematic and correctable, is mainly attributed to the distance to the target, reflectance, the shape of reflective surface, and so on. In particular, various shapes of received pulse based on the shape of reflective surface have a considerable effect on the ranging accuracy. In this paper an incoherent pulsed laser echo equation for different shapes of reflective surface is established and it is found that parameters that can represent various shapes of received pulse involve received pulse width and slew rate. A measurement method of pulse width and slew rate combining a constant fraction discriminator (CFD) principle with a time over threshold (TOT) is proposed. It is also found that the proposed method is more efficient in walk error correction than the TOT by obtaining walk error corrections corresponding to pulse width and slew rate and determining the corresponding 2D surface polynomial coefficients. The obtained polynomial coefficients are used to ensure the ranging accuracy of the LiDAR within ± 3 cm.