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US 4,734,585 AGranted
Passive infra-red sensor
AssigneeRacal-Guardall (Scotland) Limited
InventorIan A. Owers
Life of this patent
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Abstract
A passive infra-red sensor includes a window in a housing which also houses an infra-red detector. The window defines a plurality of infra-red transmitting strips which are separated by Fresnel lens segments or infra-red opaque strips. The infra-red transmitting strips provide short range sensitivity. The Fresnel lens segments where provided give longer range sensitivity.
Claims6
A passive infra-red sensor including
- a housing
- a window defined in said housing, and
- an infra-red detector mounted within said housing behind said window,
- said window defining an alternating sequence of infra-red transmitting strips which allow infra-red radiation to pass unfocused onto the detector, and lens segments positioned for focusing infra-red radiation onto said detector.
1 more element
Dependencies are inferred from the claim text.