Infrared de監 ectors can be divided into two types:lhose which depend upon heating ef驚 cts produced by the absorbed radiation ( ihermal detectors ) and those which make use of photoelectric effects ( photodete α ors ) . Infrared image sensors using photodetectors show high detectivities , but musI be cooled down fbr proper operation . Thermal detector sensors are slow responding and have relatively [ ow sensitivity , but can operate even at room temperature. In this