Infrared detectors having front and rear fields of view

Abstract

A motion sensor having front and rear fields of view includes a housing containing an infrared sensor mounted on a surface which may be a circuit board containing associated electronics to form the motion detector which produces an output in response to the motion of a warm body passing through the sensor's field of view. A front part of the housing is provided with a forward looking optical system, preferably a multifaceted Fresnel lens, and a rear part of the housing is provided with at least one rearward looking optical system. A reflector is provided directly between the sensor and the forward looking optical system for reflecting infrared light entering the rearward looking optical system onto the detector. According to one embodiment of the invention, the rearward looking optical system includes a pair of Fresnel lenses and the reflector is a flat mirror. In another embodiment of the invention, the rearward looking optical system includes a pin hole and the reflector is a reflective surface on the inside of the forward looking optical system. In yet another embodiment of the invention, the rearward looking optical system is a window without any lens and the reflector is a focusing mirror. According to a preferred embodiment of the invention, the rearward field of view is directed downward.

Dependencies are inferred from the claim text.