Passive infrared room intrusion detector

• US 3,955,184 A
• Filed: 08/18/1975
• Issued: 05/04/1976
• Est. Priority Date: 08/18/1975
• Status: Expired due to Term

• Current Assignee: Hughes Aircraft Company (Rtx Corporation)
• Original Assignee: Hughes Aircraft Company (Rtx Corporation)
• Inventors: Cinzori, Robert J., Ledbetter, Daniel R.
• Primary Examiner(s): Swann, III, Glen R.
• Application Number:
  US05/605,495
• Time in Patent Office: 260 Days
• Field of Search: 340/258 B, 340/258 D, 340/258 R, 340/276, 250/221
• US Class Current: 340/567
• CPC Class Codes: G08B 13/193 using focusing means
• CPC Class Codes: Y10S 250/01 Passive intrusion detectors

Abstract

An intrusion system detects changes in background radiation received from a plurality of orthogonally arranged fields of view (FOV) which preferably are defined by thin polyhedrons coextensive with the walls of the room. These fields of view are generated by a plurality of orthogonally arranged optical reflectors located in certain corners of the room, and any changes in background radiation within these fields of view are detected by one or more thermopile detectors which are optically aligned with the above optical reflectors. The low level - low frequency output signal voltages form the thermopile detectors are converted to an AC signal and amplified for use as an intrusion alarm signal.

Claims

1. A system for monitoring entry through any one of a plurality of planar surfaces of a room, which system includes

a. one or more means for optically reflecting or refracting to a predetermined location any changes in radiation received from a plurality of polyhedrons, each having a plane adjacent a separate one of said surfaces,

b. a detection means at said location optically coupled to said reflecting or refracting means for generating a low level - low frequency signal voltage in response to radiation changes received from said polyhedrons, and

c. signal processing means coupled to said detection means for converting and amplifying said low level - low frequency signal voltage so as to be useful as an alarm signal indicating surreptitious entry through one of said surfaces.

2. The system defined in claim 1 wherein each said reflecting or refracting means is comprised of a plurality of mutually adjacent optical surfaces which are contoured and positioned to have a common focal point with respect to all radiation received from selected ones of said polyhedrons, whereby said optical surfaces may be positioned in a corner of a room and optically coupled to a single infrared detector at said common focal point and operative to detect all radiation changes from said polyhedrons defining mutually perpendicular fields-of-view adjacent said planar surfaces of said room.

3. A method for sensing intrusion into a space whose volume is defined as a polyhedron, which includes:

a. optically reflecting to a predetermined location or locations background infrared radiation received from a plurality of fields-of-view defined by solid angles adjacent, respectively, a plurality of planar surfaces of said polyhedron, and

b. electrically sensing changes in said background radiation to thereby generate a corresponding low level - low frequency signal voltage which may be converted and amplified for use as an output alarm signal.