Signal Processing Based Pile-up Compensation for Gated Single-Photon Avalanche Diodes

TL;DR

This paper introduces a post-processing signal technique to correct pile-up effects in SPAD-based transient imaging, allowing higher laser power use without sacrificing data quality, validated through real experiments.

Contribution

It presents a novel signal processing method for pile-up compensation in SPAD imaging, enabling high-power illumination and improved transient measurement accuracy.

Findings

The method effectively reduces pile-up bias in real data.

The approach approaches the theoretical limit set by the Cramer-Rao bound.

Experimental results confirm improved transient imaging performance.

Abstract

Single-photon avalanche diode (SPAD) based transient imaging suffers from an aberration called pile-up. When multiple photons arrive within a single repetition period of the illuminating laser, the SPAD records only the arrival of the first photon; this leads to a bias in the recorded light transient wherein the transient response at later time-instants are under-estimated. An unfortunate consequence of this is the need to operate the illumination at low-power levels to reduce the probability of multiple photons returning in a single period. Operating the laser at low power results in either low signal-to-noise ratio (SNR) in the measured transients or reduced frame rate due to longer exposure durations to achieve a high SNR. In this paper, we propose a signal processing-based approach to compensate pile-up in post-processing, thereby enabling high power operation of the illuminating laser. While increasing illumination does cause a fundamental information loss in the data captured by SPAD, we quantify this information loss using Cramer-Rao bound and show that the errors in our framework are only limited to this information loss. We experimentally validate our hypotheses using real data from a lab prototype.