Infrared intrusion detector
US4740701A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | May 19, 1986 |
| Grant date | Apr 26, 1988 |
| Priority date | — |
| Expiry date | May 19, 2006 |
Classification
- Technology area (CPC Y)Emerging Cross-Sectional Technologies
- CPC primaryY10S250/01
- WIPO fieldControl
- WIPO sectorInstruments
Abstract
An intrusion detector evaluates the infrared radiation emitted by an intruder within a closely defined zone or area by means of a virtual protective curtain. Uniform sensitivity independent of incident angle of the radiation is provided by a cylindrical Fresnel lens of small thickness, which divides the field of reception into sharply defined strips or elongate zones of substantially uniform sensitivity. The longitudinal axis of this Fresnel lens defines an arcuate sector of a circle whose radius is determined by the focal length in perpendicular direction, and an infrared sensor is arranged at the circular center point, i.e., the focal point of the curved Fresnel lens. One particularly advantageous embodiment of the intrusion detector includes a double sensor configuration, equipped with several sensor elements cooperating with one or more cylindrical Fresnel lenses, thus covering a number of separate zones for simultaneous radiation detection.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.