Passive infrared detectors

• US 7,875,852 B2
• Filed: 07/26/2007
• Issued: 01/25/2011
• Est. Priority Date: 07/27/2006
• Status: Active Grant

• Current Assignee: Tyco Fire & Security GmbH (Johnson Controls International plc)
• Original Assignee: Visonic Incorporated (Johnson Controls International plc)
• Inventors: Zhevelev, Boris, Kotlicki, Yaacov
• Primary Examiner(s): Porta; David P
• Assistant Examiner(s): Gaworecki; Mark R
• Application Number:
  US12/227,274
• Publication Number:
  US 20090302222A1
• Time in Patent Office: 1,279 Days
• Field of Search: 250/332, 250/339.12, 250/352, 250/353, 250/DIG.1
• US Class Current: 250/332
• CPC Class Codes: G01J 5/0022 for sensing the radiation of moving bodies
• CPC Class Codes: G01J 5/0025 Living bodies ear thermometers G01J5/0011; detecting, measuring or recording for diagnostic purposes A61B5/00
• CPC Class Codes: G01J 5/046 Materials; Selection of thermal materials
• CPC Class Codes: G01J 5/08 Optical arrangements
• CPC Class Codes: G01J 5/0802 Optical filters
• CPC Class Codes: G01J 5/0808 Convex mirrors
• CPC Class Codes: G01J 5/0893 Arrangements to attach devices to a pyrometer, i.e. attaching an optical interface; Spatial relative arrangement of optical elements, e.g. folded beam path G01J5/049 takes precedence
• CPC Class Codes: G02B 5/208 for use with infrared or ultraviolet radiation, e.g. for separating visible light from infrared and/or ultraviolet radiation
• CPC Class Codes: G02B 5/22 Absorbing filters G02B5/201 - G02B5/208 take precedence
• CPC Class Codes: G08B 13/193 using focusing means

Abstract

A passive infrared detector assembly including a detector housing comprising a window transparent to far infrared radiation, at least one sensor sensitive to the far infrared radiation and disposed within the detector housing and an anti-masking subassembly, including at least one light guide having a serrated light aperture, the light aperture defining a plurality of teeth like portions and a plurality of grooves and being disposed close to the outside of the window, at least one infrared light emitter operative to emit near infrared radiation via the light aperture of the at least one light guide and a near infrared radiation receiver operative to receive radiation emitted by the at least one near infrared light emitter and to measure the level of received near infrared radiation and to provide a masking alarm signal upon detection of a predetermined change in the level of the received near infrared radiation.

Claims

1. A passive infrared detector assembly comprising:

a detector housing comprising a window transparent to far infrared radiation;

at least one sensor sensitive to said far infrared radiation and disposed within said detector housing; and

an anti-masking subassembly, including;

at least one light guide having at least one serrated light aperture, said light aperture defining a plurality of teeth like portions and a plurality of grooves and being disposed close to the outside of said window;

at least one infrared light emitter operative to emit near infrared radiation, via said light aperture of said at least one light guide, outside of said at least one light guide; and

a near infrared radiation receiver operative to receive said near infrared radiation emitted by said at least one near infrared light emitter via said light aperture and to measure the level of received near infrared radiation and to provide a masking alarm signal upon detection of a predetermined change in the level of said received near infrared radiation,

wherein masking agents accumulating in said plurality of grooves change the level of said received near infrared radiation by a degree which exceeds a predetermined alarm threshold thereby causing the provision of a masking alarm signal, and

wherein water accumulating in said plurality of grooves change the level of said received near infrared radiation by a degree which does not exceed said predetermined alarm threshold thereby not causing the provision of a masking alarm signal.

2. A passive infrared detector assembly according to claim 1 and wherein said at least one sensor is a pyroelectric sensor.

3. A passive infrared detector assembly according to claim 1 and wherein said at least one sensor is sensitive to radiation having wavelengths in the range of 5-14 μ

m.

4. A passive infrared detector assembly according to claim 1 and wherein the at least one infrared light emitter is operative to emit radiation having wavelengths in the range of 0.7-1 μ

m.

5. A passive infrared detector assembly according to claim 1 and wherein said infrared radiation receiver is operative to receive radiation reflected back from the near vicinity of said passive infrared detector.

6. A passive infrared detector assembly according to claim 1 and wherein said near infrared radiation receiver is located within said detector housing.

7. A passive infrared detector assembly according to claim 1 and wherein said at least one infrared light emitter is located within said detector housing.

8. A passive infrared detector assembly according to claim 1 and wherein at least one of pitch, height, curvature and finish of said plurality of teeth like portions is configured to cause said near infrared radiation receiver to differentiate between different liquids.

9. A method for detecting masking of a passive infrared detector, the method comprising:

providing a detector housing comprising a window transparent to far infrared radiation;

disposing within said detector housing at least one sensor sensitive to said far infrared radiation; and

providing an anti-masking subassembly, including;

at least one light guide having at least one serrated light aperture, said light aperture defining a plurality of teeth like portions and a plurality of grooves and being disposed close to the outside of said window;

at least one infrared light emitter operative to emit near infrared radiation, via said light aperture of said at least one light guide, outside of said at least one light guide; and

a near infrared radiation receiver operative to receive said near infrared radiation emitted by said at least one near infrared light emitter via said light aperture and to measure the level of received near infrared radiation and to provide a masking alarm signal upon detection of a predetermined change in the level of said received near infrared radiation,

wherein masking agents accumulating in said plurality of grooves change the level of said received near infrared radiation by a degree which exceeds a predetermined alarm threshold thereby causing the provision of a masking alarm signal, and

wherein water accumulating in said plurality of grooves change the level of said received near infrared radiation by a degree which does not exceed said predetermined alarm threshold thereby not causing the provision of a masking alarm signal.

10. A method according to claim 9 and wherein said disposing at least one sensor comprises disposing a pyroelectric sensor within said housing.

11. A method according to claim 9 and wherein said disposing at least one sensor comprises disposing at least one sensor which is sensitive to radiation having wavelengths in the range of 5-14 μ

m.

12. A method according to claim 9 and wherein the at least one infrared light emitter is operative to emit radiation having wavelengths in the range of 0.7-1 μ

m.

13. A method according to claim 9 and wherein said infrared radiation receiver is operative to receive radiation reflected back from the near vicinity of said passive infrared detector.

14. A method according to claim 9 and wherein said near infrared radiation receiver is located within said detector housing.

15. A method according to claim 9 and wherein said at least one infrared light emitter is located within said detector housing.

16. A method according to claim 9 and also comprising configuring at least one of pitch, height, curvature and finish of said plurality of teeth like portions to cause said near infrared radiation receiver to differentiate between different liquids.