Discriminator threshold selection logic to improve signal to noise ratio in photon counting

Abstract

The discriminator threshold plays a vital role in photon counting technique used with low level light detection in lidars and bio-medical instruments. A low discriminator threshold gives high counts due to secondary emitted electrons and ground level (electrical) noise, while high threshold skips the photon pulses having lower amplitude. In both the cases the signal to noise ratio of photon counting system deteriorates. In this article the impact of improper selection of discriminator threshold on photon counting has been described. Here we introduce a simple technique by which the system (micro pulse lidar) selects the discriminator threshold at the set PMT voltage and assigns this value to the multi-channel scaler. The technique is applicable in diverse fields employing photon counting system.