Infrared human detector not barred by an intervening obstruction

摘要

An intruder detection system for senses infrared radiated by an intruder through a window-pane and detecting the intrusion through the reception of an output from the infrared sensors. The system includes a light emitter for projecting infrared rays toward a detection area and a light acceptor for receiving at least part of the infrared rays projected by the light emitter through an obstruction detection optical path. The light emitter and the light acceptor are located on opposite sides of the window-pane.