Is a
Patent attributes
Current Assignee
Patent Jurisdiction
Patent Number
Patent Inventor Names
Matthieu Richard0
Date of Patent
October 5, 2010
0Patent Application Number
119137900
Date Filed
February 20, 2006
0Patent Citations Received
Patent Primary Examiner
Patent abstract
The obstruction detection device for an infrared intruder detection system comprises at least one transparent facet having a roughened surface; a light emitter arranged for emitting light towards the roughened surface; a light detector arranged for detecting the intensity of light, which is transmitted or reflected or diffracted by the roughened surface into a specific direction of space; and an output device for outputting an alarm-signal, when an absolute difference between the intensity of the detected light and a reference value exceeds a threshold value. A liquid or spray applied onto the roughened surface changes its scattering patterns. This change triggers the alarm-signal.
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