Passive infrared alarm device
US4245217A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Jul 13, 1978 |
| Grant date | Jan 13, 1981 |
| Priority date | — |
| Expiry date | Jul 13, 1998 |
Classification
- Technology area (CPC Y)Emerging Cross-Sectional Technologies
- CPC primaryY10S250/01
- WIPO fieldOptics
- WIPO sectorInstruments
Abstract
A passive infrared alarm device evaluates the changes in infrared radiation level of a monitored room or a monitored portion of a room for alarm purposes. In accordance with the invention, an infrared sensing element is employed toward which an optical reflector directs infrared radiation emanating from one or more angles in a room to be monitored. An infrared filter is mounted in the path of the reflected infrared radiation before such radiation reaches the sensing element. The infrared filter is designed to absorb infrared radiation below a predetermined minimum wavelength, and additional means is provided for partially absorbing infrared radiation below the predetermined minimum at the reflector.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.