Obstruction detection device
US7807970B2 · kind B2 · utility
Assignee
Inventor
Key dates
| Filing date | Feb 20, 2006 |
| Grant date | Oct 5, 2010 |
| Priority date | — |
| Expiry date | Feb 20, 2026 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG08B29/046
- WIPO fieldControl
- WIPO sectorInstruments
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.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.