Signal and performance model for imaging systems with SPAD detectors

Single Photon Avalanche Diodes (SPAD) have shown great promise for use in Lidar and low light applications. Although staring arrays were initially developed for medical applications, recent Lidar sensor solution demands have fueled the development of large count staring sensors with quantum efficiencies extending in the NIR/SWIR and with exotic readout circuits. The same technology also enables low light systems with sensitivity below conventional CMOS. As the name implies, SPAD detectors are sensitive to single photons, behave as stochastic devices, and require special treatment for signal interpretation. In this paper, we describe a signal and noise model for both active and passive SPAD based imaging systems that includes the generation of readout events based on the SPAD detector stochastic model. The model presented here allows the evaluation of SPAD based systems under specific illumination conditions and enables the evaluation of SPAD and sensor parameter system sensitivity.