The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Aug. 24, 1999
Filed:
Nov. 01, 1996
Dieter Wieser, Zurich, CH;
Kurt Albert Muller, Mannedorf, CH;
Martin Allemann, Wetzikon, CH;
Michael Thomas Gale, Wettswil a. Albis, CH;
Thomas Hessler, Zurich, CH;
Cerberus AG, , CH;
Abstract
A passive infrared intrusion detector for the detection of infrared body radiation includes a sabotage detector, in particular for detecting spraying of the entrance window of the intrusion detector. The sabotage detector includes a light source, a corresponding light sensor, and an optical diffraction grating structure on the outside of the entrance window. The light source and the light sensor can be on the same or on opposite sides of the entrance window. By first- or higher-order diffraction, light from the light source is focused onto the sensor, and a resulting electrical signal from the sensor is evaluated by an evaluation circuit. In case of sabotage, the focusing effect of the optical diffraction grating structure vanishes, so that the light intensity at the detector is reduced. The drop in light intensity triggers a sabotage alarm signal.