  Single-Photon Avalanche Detector (SPAD) arrays are a rapidly emerging
technology. These multi-pixel sensors have single-photon sensitivities and
pico-second temporal resolutions thus they can rapidly generate depth images
with millimeter precision. Such sensors are a key enabling technology for
future autonomous systems as they provide guidance and situational awareness.
However, to fully exploit the capabilities of SPAD array sensors, it is crucial
to establish the quality of depth images they are able to generate in a wide
range of scenarios. Given a particular optical system and a finite image
acquisition time, what is the best-case depth resolution and what are realistic
images generated by SPAD arrays? In this work, we establish a robust yet simple
numerical procedure that rapidly establishes the fundamental limits to depth
imaging with SPAD arrays under real world conditions. Our approach accurately
generates realistic depth images in a wide range of scenarios, allowing the
performance of an optical depth imaging system to be established without the
need for costly and laborious field testing. This procedure has applications in
object detection and tracking for autonomous systems and could be easily
extended to systems for underwater imaging or for imaging around corners.
