Patent ID: 8395127

Claim:
A photon counting radiation detector comprising: a Geiger mode detector configured to generate an electrical signal indicative of detection of a photon and dark current noise, the Geiger mode detector including an avalanche photodiode (APD) device biased in an avalanche breakdown region and an output transistor; and a bias circuit configured to bias the avalanche photodiode at a selectable detector bias voltage level including a lower level at which the detector generates an output with less dark current noise and has less gain and a higher level at which the detector generates an output with more dark current noise and has more gain; a user interface with which a user selects between an automatic mode and a manual mode, wherein: in the manual mode, selects among at least (1) the detector output with less dark current noise and less gain and (2) the detector output with more dark current noise and more gain; and in the automatic mode, the bias circuit automatically adjusts the detector bias voltage level in accordance with a measured detector temperature.