Dead time effects in the indirect time-of-flight measurement with SPADs

Indirect time-of-flight measurement with SPADs is performed by counting incident photons in several time windows. Since SPADs exhibit dead time not all incident photons can be counted within a given time window. This affects the expected values and, hence, the variance of the distance measurement. For photon detection rates close to the inverse of the dead time, which defines the maximum count rate of a SPAD, the probability of photon detection cannot be assumed constant within the window anymore. In this paper the effects of dead time on the photon counts are analyzed by employing statistical calculations. Based on these a model to correct such effects can be derived.