Intruder detector with anti-obscuring means
First Claim
1. An apparatus for detecting an intruder in a zone to be supervised, said apparatus comprising:
- a housing having a window, said housing being arranged at the first end of the zone to be supervised;
a passive infrared detector arranged in the housing to receive infrared radiation passing through the window, said passive detector detecting radiation around a wavelength λ
1 and generating an output signal in response thereto;
an emitter for emitting infrared radiation around a wavelength λ
2, λ
2 being different from λ
1 ;
a second infrared detector arranged in the housing to receive infrared radiation passing through the window, said second detector detecting radiation around a wavelength λ
2 and generating an output signal in response thereto;
a reflector arranged at an end of the zone to be supervised opposite the housing;
said reflector being arranged to receive infrared radiation from the emitter and to reflect said infrared radiation onto the second infrared detector;
means for causing the emitter to emit infrared radiation of wavelength λ
2 ; and
means for comparing the output signal of the second detector with first and second reference values, the first reference value being less than the second reference value, said comparison means activating an alarm if the output signal is less than the first reference value or if the output signal is greater than the second reference value.
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Accused Products
Abstract
An apparatus for detecting intruders comprising a housing provided with at least one window, a passive infrared detector (for detecting the radiation emitted by an intruder around a wavelength λ1), and an anti-obscuring device (detecting by infrared radiation having a wavelength λ2 the presence of an obscuring of the appparatus for detecting intruders). The apparatus further includes an electronic circuit intended to operate an alarm when the presence of an intruder or an obscuring element has been detected. The apparatus for detecting intruders has a detector for detecting an obscuring element arranged at small and at large distances. It further includes a self-verification circuit. An obscuring element is detected, inter alia, by a mirror arranged at the end of the zone to be supervised, which returns radiation λ2 emitted by an emitter to a detector, both being situated very close to the detector of radiation having a wavelength λ1.
53 Citations
6 Claims
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1. An apparatus for detecting an intruder in a zone to be supervised, said apparatus comprising:
-
a housing having a window, said housing being arranged at the first end of the zone to be supervised; a passive infrared detector arranged in the housing to receive infrared radiation passing through the window, said passive detector detecting radiation around a wavelength λ
1 and generating an output signal in response thereto;an emitter for emitting infrared radiation around a wavelength λ
2, λ
2 being different from λ
1 ;a second infrared detector arranged in the housing to receive infrared radiation passing through the window, said second detector detecting radiation around a wavelength λ
2 and generating an output signal in response thereto;a reflector arranged at an end of the zone to be supervised opposite the housing;
said reflector being arranged to receive infrared radiation from the emitter and to reflect said infrared radiation onto the second infrared detector;means for causing the emitter to emit infrared radiation of wavelength λ
2 ; andmeans for comparing the output signal of the second detector with first and second reference values, the first reference value being less than the second reference value, said comparison means activating an alarm if the output signal is less than the first reference value or if the output signal is greater than the second reference value. - View Dependent Claims (2, 3, 4, 5, 6)
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Specification
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- Resources
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Current AssigneeUS Philips Corporation (Koninklijke Philips N.V.)
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Original AssigneeUS Philips Corporation (Koninklijke Philips N.V.)
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InventorsHazan, Jean-Pierre, Steers, Michel
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Primary Examiner(s)Orsino, Joseph A.
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Assistant Examiner(s)TUMM, BRIAN
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Application NumberUS06/800,889Time in Patent Office942 DaysField of Search340/567, 340/565, 340/552, 340/555, 340/600, 340/550, 250/338, 250/495.1, 250/504 R, 250/342, 250/353, 250/221US Class Current340/567CPC Class CodesG08B 13/19 using infrared-radiation de...G08B 29/046 prevention of tampering wit...Y10S 250/01 Passive intrusion detectors
