Infrared-type intrusion detector

摘要

An infrared-type intrusion detector for monitoring the presence of a person is disclosed. The detector has a plurality of concave reflector segments for defining separate fields of view. Infrared radiation emanating from the person in any of the fields of view is collected and focused upon a single sensing element to produce a cautionary signal representative of such detection. Plane mirrors are introduced in an optical reflection system of the detector to reflect the radiation from the reflector segments upon the sensing element, such as to reduce the spacing or dimension required for the optical system along the optical axis of the sensing element, whereby the detector is allowed to be made compact in size. Further, the optical system of the detector includes a device for selectively interrupting one or more paths between the respective reflector segments and the sensing element, such that the detector can receive the infrared radiation only from the selected or desired fields of view and ignore it from the undesired fields depending upon certain operating conditions, enhancing detection reliability.