Patent US4752768A successfully refreshed from Google Patents.
US4752768A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Intruder detector with anti-obscuring means
Assignee: US Philips Corp
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Filing: 1985-11-22
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Granted: 1988-06-21
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Expires: 2005-11-22
Abstract
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 λ 1 ), and an anti-obscuring device (detecting by infrared radiation having a wavelength λ 2 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 λ 2 emitted by an emitter to a detector, both being situated very close to the detector of radiation having a wavelength λ 1 .
Inventors
- 👤 Michel Steers
- 👤 Jean-Pierre Hazan
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-03 21:40
CPC Classifications
G; G08; G08B; G08B29/00; G08B29/02; G08B29/04; G08B29/046; G08B13/00; G08B13/18; G08B13/189; G08B13/19; Y; Y10; Y10S; Y10S250/00; Y10S250/01
Claims Analysis
Total Claims: 7
Claim 1
Independent Claim
230 words
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.
Claim 2
Independent Claim
230 words
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.
Claim 3
Dependent Claim
83 words
An apparatus as claimed in claim 1, further comprising: a second light emitter for emitting infrared radiation around a wavelength λ 1 , said second light emitter being arranged in front of the window outside the housing to radiate infrared radiation onto the passive detector; means for momentarily energizing the second light emitter one time only when the apparatus is turned on; and means for activating an alarm if the passive detector produces no output signal when the second light emitter is energized.
Claim 4
Dependent Claim
40 words
An apparatus as claimed in claim 2, characterized in that the means for causing the first emitter to emit infrared radiation of wavelength λ 2 momentarily energizes the first light emitter one time only when the apparatus is turned on.
Claim 5
Dependent Claim
54 words
An apparatus as claimed in claim 1, further comprising a dichroic mirror arranged in the housing to receive infrared radiation of wavelength λ 1 and λ 2 passing through the window, said dichroic mirror transmitting infrared radiation of one wavelength λ 1 or λ 2 , and reflecting infrared radiation of the other wavelength.
Claim 6
Dependent Claim
40 words
An apparatus as claimed in claim 4, characterized in that the means for causing the first emitter to emit infrared radiation of wavelength λ 2 momentarily energizes the first light emitter one time only when the apparatus is turned on.
Claim 7
Dependent Claim
40 words
An apparatus as claimed in claim 1, characterized in that the means for causing the first emitter to emit infrared radiation of wavelength λ 2 momentarily energizes the first light emitter one time only when the apparatus is turned on.
References Cited (Backward Citations)
US3858043A
Cited
US4119949A
Cited
GB1603306A
Cited
US4242669A
Cited
GB2141228A
Cited
US4656462A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1991-06-21 | 1991-12-21 | 1992-06-21 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1995-06-21 | 1995-12-21 | 1996-06-21 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1999-06-21 | 1999-12-21 | 2000-06-21 | $7700.00 | Window Closed / Lapsed |