General characteristics of detectors

Quantum and thermal detectors are the two main classes of detectors used to measure radiation. They differ widely in their noise and spectral range properties. We also distinguish between planar detectors and cavity detectors, which are classified differently on the basis of their reflection coefficient. A third distinction can be made between primary and transfer detectors. Numerous other characteristics, such as spectral selectivity, directivity and specialization for illuminance or luminance quantities, further enrich this family. This article will only describe two reference detectors, one thermal, the other quantum, both arranged in cavities to limit reflection of incident radiation.