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. 18, 1981
Filed:
Oct. 18, 1979
David Appleby, Northampton, GB;
Plessey Handel und Investments A.G., Zug, CH;
Abstract
An intruder detector consists of an element of pyroelectric material having three defined regions; two being active to infra-red radiation and one being relatively inactive to infra-red radiation. The inactive region and one of the active regions are connected together in parallel and the other active region is connected in series with these two. The arrangement has full cancellation of environment effects while being partially unbalanced for infra-red detection so that isolated areas of infra-red radiation (such as an intruder) can be detected at long and short ranges. The element is used with a concave mirror for increased zonal coverage. Each of the regions of pyroelectric material has a substantially constant thickness and all of the three regions have the same thickness.