Infrared Detectors and Detector Arrays
There are two general classes of detectors: photon (or quantum) and thermal detectors [1,2]. Photon detectors convert absorbed photon energy into released electrons (from their bound states to conduction states). The material band gap describes the energy necessary to transition a charge carrier from the valence band to the conduction band. The change in charge carrier state changes the electrical properties of the material. These electrical property variations are measured to determine the amount of incident optical power. Thermal detectors absorb energy over a broad band of wavelengths. The energy absorbed by a detector causes the temperature of the material to increase. Thermal detectors have at least one inherent electrical property that changes with temperature. This temperature-related property is measured electrically to determine the power on the detector. Commercial infrared imaging systems suitable for medical applications use both types of detectors. We begin by describing the physical mechanism employed by these two detector types.