Passive infrared alarm device
First Claim
1. Passive infrared alarm device, containing:
- (a) an infrared radiation detector;
(b) an optical device with at least one reflecting element, which directs the infrared radiation from one or several room angles to be monitored onto the detector;
(c) an evaluating device, which processes an output signal delivered by the detector and, where applicable, releases an alarm signal;
(d) a radiation filter which is placed between the optical device and detector, which radiation filter keeps undesired radiation up to a critical boundary wavelength away from the detector;
characterized by the feature;
(e) said reflecting element having a reflecting surface area and including filter means for the prevention of a heating of said radiation filter by keeping rays up to its critical boundary wavelength away from it.
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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.
22 Citations
15 Claims
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1. Passive infrared alarm device, containing:
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(a) an infrared radiation detector; (b) an optical device with at least one reflecting element, which directs the infrared radiation from one or several room angles to be monitored onto the detector; (c) an evaluating device, which processes an output signal delivered by the detector and, where applicable, releases an alarm signal; (d) a radiation filter which is placed between the optical device and detector, which radiation filter keeps undesired radiation up to a critical boundary wavelength away from the detector;
characterized by the feature;(e) said reflecting element having a reflecting surface area and including filter means for the prevention of a heating of said radiation filter by keeping rays up to its critical boundary wavelength away from it. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15)
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Specification
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- Resources
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Current AssigneeHeimann GmbH
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Original AssigneeHeimann GmbH
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InventorsSteinhage, Peter-Wilhelm
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Primary Examiner(s)Caldwell, Sr., John W.
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Assistant Examiner(s)Nowicki, Joseph E.
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Application NumberUS05/924,163Time in Patent Office915 DaysField of Search340/552, 340/555, 340/556, 350/1.6, 350/290, 250/339, 250/340, 250/347, 250/352, 250/353, 250/510, 250/346US Class Current340/555CPC Class CodesG02B 5/281 designed for the infrared l...G03B 7/085 for control of apertureG08B 13/193 using focusing meansY10S 250/01 Passive intrusion detectors
