Ceiling mounted passive infrared intrusion detector with prismatic window

摘要

A ceiling mounted passive infrared intrusion detector includes a window which has an exterior surface with ridges formed of intersecting planes, which are arranged to provide internal reflection of radiation received from selected angles with respect to the optical axis of the device and to deflect such radiation into a direction parallel to the optical axis. Focusing means arranged as part of the detector focuses the parallel infrared radiation onto a detecting element within the device.