Characterization and mitigation of electronic crosstalk on InGaAs PIN 3D flash LiDAR imagers

Abstract

This research presents methods and results of characterizing and mitigating electronic crosstalk on InGaAs PIN photodiode 3D flash LiDAR imagers, with the goal of significantly simplifying and improving the calibration system design. 3D flash LiDAR detectors use time to digital conversion (TDC) circuits to estimate the time of flight of a pulse when a detection threshold is met. As the underlying TDC circuits require more space and power, these circuits will cause, in high bus loading events, electronic crosstalk. These events are more likely to occur in situations where many detectors simultaneously trigger, something that can occur when viewing a flat object head-on with uniform illumination, thus limiting these sensors to image a full frame due to this simultaneous ranging crosstalk noise (SRCN). Solutions previously devised to mitigate this electronic crosstalk included using a windowed region of interest to mitigate additional noise by preventing triggering on all of the focal plane array (FPA) except the windowed region and using a checkerboard pattern for imaging the full frame. Here the electronic crosstalk is characterized, and mitigated, using a physical checkerboard target, leading to a more compact system design using a spatial light modulator and direct illumination.