EP0005352A1 - Einrichtung zur Meldung von Einbruch durch Strahlungsdetektion - Google Patents

Einrichtung zur Meldung von Einbruch durch Strahlungsdetektion Download PDF

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Publication number
EP0005352A1
EP0005352A1 EP79300724A EP79300724A EP0005352A1 EP 0005352 A1 EP0005352 A1 EP 0005352A1 EP 79300724 A EP79300724 A EP 79300724A EP 79300724 A EP79300724 A EP 79300724A EP 0005352 A1 EP0005352 A1 EP 0005352A1
Authority
EP
European Patent Office
Prior art keywords
radiation
wavelength
signal
detecting
detecting means
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP79300724A
Other languages
English (en)
French (fr)
Inventor
David William Crick
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
BA Security Systems Ltd
Original Assignee
BA Security Systems Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by BA Security Systems Ltd filed Critical BA Security Systems Ltd
Publication of EP0005352A1 publication Critical patent/EP0005352A1/de
Withdrawn legal-status Critical Current

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Classifications

    • G—PHYSICS
    • G08—SIGNALLING
    • G08B—SIGNALLING OR CALLING SYSTEMS; ORDER TELEGRAPHS; ALARM SYSTEMS
    • G08B29/00—Checking or monitoring of signalling or alarm systems; Prevention or correction of operating errors, e.g. preventing unauthorised operation
    • G08B29/02—Monitoring continuously signalling or alarm systems
    • G08B29/04—Monitoring of the detection circuits
    • G08B29/046—Monitoring of the detection circuits prevention of tampering with detection circuits
    • G—PHYSICS
    • G08—SIGNALLING
    • G08B—SIGNALLING OR CALLING SYSTEMS; ORDER TELEGRAPHS; ALARM SYSTEMS
    • G08B13/00—Burglar, theft or intruder alarms
    • G08B13/18—Actuation by interference with heat, light, or radiation of shorter wavelength; Actuation by intruding sources of heat, light, or radiation of shorter wavelength
    • G08B13/189—Actuation by interference with heat, light, or radiation of shorter wavelength; Actuation by intruding sources of heat, light, or radiation of shorter wavelength using passive radiation detection systems
    • G08B13/19—Actuation by interference with heat, light, or radiation of shorter wavelength; Actuation by intruding sources of heat, light, or radiation of shorter wavelength using passive radiation detection systems using infrared-radiation detection systems
    • G08B13/193—Actuation by interference with heat, light, or radiation of shorter wavelength; Actuation by intruding sources of heat, light, or radiation of shorter wavelength using passive radiation detection systems using infrared-radiation detection systems using focusing means

Definitions

  • This invention relates to radiation detection apparatus and will be described particularly with reference to pyroelectric passive infra-red intruder detection apparatus, that is, to apparatus responsive to infra-red radiation emitted by an unauthorised entrant into a space at a time when the space should be empty.
  • Such apparatus works on the principle that a change in infra-red radiation within its field of view is detected by the apparatus.
  • the change in detected radiation produces an electrical signal which is amplified and filtered before being applied to a level detector circuit which operates an alarm.
  • the detecting element may be at the focal point of a concave parabolic or spherical mirror which will provide a single zone a sensitivity having strongly directional characteristics.
  • the detecting element may be located at the focal point of an array of mirrors which can conveniently be arranged to produce a number of widely spaced radial zones of sensitivity. If these zones are arranged suitably, a large space can be covered by one detecting elements
  • a disadvantage of both these systems is that their zones of sensitivity can be partially or totally obscured by placing thermally opaque material over their apertures. Such material severely attenuates radiation in the range of wavelengths of interest, which range is typically between 4 and 20 microns and so approximately centred on 10 microns wavelength. If this is done, any change in radiation caused by an intruder will not be detected and the alarm will not be activated. This aspect places a serious limitation on the use of passive infra-red detectors for security purposes.
  • the present invention provides radiation detection apparatus comprising first detecting means for detecting radiation at a first wavelength, first indicating means responsive to said first detecting means, characterised in that means for sensing the presence of an obturating element preventing the operation of said first detecting means are provided, said sensing means comprising transmitting means for transmitting a signal at a second wavelength, second detecting means responsive to the signal at the second wavelength in the presence of the obturating element, and second indicating means responsive to said second detecting means.
  • the first detecting means is arranged to be sensitive to infra-red radiation at between 4 and 20 microns.
  • the transmitting and second detecting means are so disposed that the detecting means will only detect the transmitted signal if the signal is reflected from an obturating element.
  • this is achieved using a single concave spherical or parabolic mirror for not only the transmitted signal but also for the detected radiation.
  • a different wavelength is chosen for the second detecting means which falls outside the range of sensitivity of the first detecting means but which preferably is also within the infra-red region.
  • the transmitted signal at the second wavelength is pulsed at a certain frequency and the apparatus is arranged to reject detected radiation not pulsed at that frequency.
  • the two indicating means may include separate alarm devices one to form the conventional intrusion alarm, and the other an anti-tamper alarm.
  • both the detecting circuits may be connected to a single alarm device for operation in either circumstance.
  • An alternative to the single mirror arrangement is to use an array of mirrors for producing a number of zones of sensitivity, and in this case the array may be used for focussing both the transmitted signal and the detected radiation in a similar fashion to that described above.
  • a housing 1 of an infra-red detector which substan- tially encloses and protects the internal apparatus from exterior stimuli except through an opening or window 2.
  • the window 2 is covered by an infra-red transparent material 3, shown partially cut-away which is conveniently made of a polymer film to provide physical protection to the apparatus yet allow transmission of radiation at the wavelengths of interest.
  • a screening mesh 4 also shown partially cut-away.
  • a concave mirror 5 arranged to focus substantially parallel radiation entering through the opening 2 and impingeing thereupon.
  • the mirror 5 may be of parabolic or spherical configuration according to convenience.
  • Figure 3 shows a circuit which may be used with the above-described detector.
  • the detecting element 6 converts a change of incident radiation into an electrical signal which is fed t.o the input of a high impedance amplifier 70
  • the amplified signal is fed through a low frequency amplifier 8 to a voltage level detector 9.
  • a sufficiently large change in incident radiation of the correct wavelength will cause the level detector 9 to activate the alarm relay 10, so producing a warning of intrusion.
  • an obturating element such as a screen of thermally opaque material 11 will drastically reduce or totally obscure the radiation incident on the infra-red detecting element, and thus an alarm indication may not be obtained.
  • a pulse generator 12 produces pulses of a fixed frequency which are amplified by a pulse amplifier 13 and fed to a radiation emitting diode 14.
  • This diode 14 is chosen to emit radiation of a different wavelength to that at which the detecting element 6 is sensitive.
  • a gallium arsenide diode, emitting radiation of about 0.9 microns wavelength is suitable as wavelengths emitted by the human body and hence at which the detecting element 6 is chosen to be sensitive are centred on about 10 microns.
  • the diode 14 emits radiation into the environment in a series of pulses according to the frequency of the generator 12, and this radiation has no further effect on the apparatuso
  • a proportion of the pulsed radiation 14 is reflected from the screen 11 and on to a second detecting element which may conveniently be a radiation sensitive diode 15.
  • This radiation gives rise to a pulsed electrical signal which is amplified by a pulse amplifier 16.
  • the pulse amplifier 16 is preferably arranged to have strong rejection of frequencies below that of the pulse frequency thus minimising interaction arising from the sensitivity of the detecting element 15 to ather spurious radiation.
  • the output of the amplifier 16 is fed to a second level detector 17, which upon receiving a sufficiently strong signal, activates the alarm relay 10 to produce a warning of attempted obscuring of the detector.
  • the electrical apparatus is conveniently positioned on printed circuit boards 18 within the housing 1.
  • the infra-red emitting diode i4 is positioned close to the detecting element 6. This means that since it is very close to the focal point of the mirror 5, its pulsed radiation will be reflected back by the mirror through the opening 2 as an approximately parallel straight beam. If a thermally opaque screen is positioned in front of the opening 2 , a proportion of this pulsed radiation will be reflected back and on to the second detecting element 15.
  • the detecting element 15 is conveniently positi- oned on the screening mesh 4 and has a shield 19 surrounding each side of it to prevent pulsed radiation being reflected spuriously, possibly from the interior of the housing, on to the element and providing a false alarm indication.
  • Figure 3 shows the two voltage level detectors 9 and 17 of each infra-red circuit connected to one alarm relay 10. However, if preferred, these may be connected to separate relays to provide one main alarm with a separate anti-tamper alarm having a separate circuit.
  • the use of the low frequency amplifier 8 sensitive to slow changes in incident infra-red radiation, in combination with the pulse amplifier 16 sensitive to frequencies above that of the pulse generator 12 minimises the possibility of any interaction between the two systems which may arise, for example, as a result of the detecting element 6 reacting to the pulsed radiation from the diode 14.
  • the interaction is also reduced by using a wavelength (e.g. 0.9 microns as above) of pulsed radiation suitably different to the wavelengths likely to be produced by an intruder (centred on 10 microns) to which the detecting element 6 is chosen to be sensitive.
  • the radiation should be pulsed and the detecting circuit arranged to be sensitive at that pulse frequency.
  • the apparatus described above utilises a concave mirror for both focussing the radiation emitted from the exterior on to the first detecting element and also for reflecting the pulsed radiation into the zone to be protected.
  • a concave mirror for both focussing the radiation emitted from the exterior on to the first detecting element and also for reflecting the pulsed radiation into the zone to be protected.
  • the same principle of operation can be used whereby the pulsed radiation is emitted into the number of zones by reflection from the array of mirrors.
  • a suitably mounted detecting element will then response to pulsed radiation reflected from a thermally opqaue screen in a similar manner to that described above.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Computer Security & Cryptography (AREA)
  • Burglar Alarm Systems (AREA)
EP79300724A 1978-04-27 1979-04-27 Einrichtung zur Meldung von Einbruch durch Strahlungsdetektion Withdrawn EP0005352A1 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB1683278A GB1603306A (en) 1978-04-27 1978-04-27 Intruder alarms
GB1683278 1978-04-27

Publications (1)

Publication Number Publication Date
EP0005352A1 true EP0005352A1 (de) 1979-11-14

Family

ID=10084489

Family Applications (1)

Application Number Title Priority Date Filing Date
EP79300724A Withdrawn EP0005352A1 (de) 1978-04-27 1979-04-27 Einrichtung zur Meldung von Einbruch durch Strahlungsdetektion

Country Status (2)

Country Link
EP (1) EP0005352A1 (de)
GB (1) GB1603306A (de)

Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2542116A1 (fr) * 1983-02-25 1984-09-07 Verdon Roger Dispositif d'elimination des fausses alarmes
EP0189536A1 (de) * 1985-01-08 1986-08-06 Cerberus Ag Infrarot-Einbruchdetektor
EP0240657A1 (de) * 1986-03-24 1987-10-14 Fritz Fuss GmbH & Co. Verfahren zum Betreiben eines Bewegungsmelders
EP0274889A2 (de) * 1987-01-15 1988-07-20 Racal-Guardall (Scotland) Limited Sicherheitssensoren
EP0289621A1 (de) * 1986-10-31 1988-11-09 Takenaka Engineering Co. Ltd. Passives infrarot-einbruchmessfühler, ausgerüstet mit sichtfeldunterbrechungsüberwachungsmechanismus
EP0337964A1 (de) * 1988-04-13 1989-10-18 ELKRON S.p.A. Kombinierte Infrarot- und Mikrowellendetektorvorrichtung, insbesondere für Antiintrusionsanlagen
EP0375270A2 (de) * 1988-12-22 1990-06-27 Guardall Limited Einrichtung und Verfahren zur Strahlungserfassung
EP0499177A1 (de) * 1991-02-11 1992-08-19 BITRON VIDEO S.r.l. Eindringmeldealarm
DE102006019941A1 (de) * 2006-04-28 2007-10-31 Pepperl + Fuchs Gmbh Vorrichtung und Verfahren zum Nachweis von Personen, Tieren oder Gegenständen

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2141228B (en) * 1983-06-09 1987-01-07 Shorrock Security Systems Ltd Infra-red intrusion detector
GB2152721A (en) * 1984-01-14 1985-08-07 John Michael Loftus Intruder alarm apparatus
FR2574200B1 (fr) * 1984-11-30 1987-01-23 Labo Electronique Physique Dispositif de detection d'intrus muni d'un dispositif d'antimasquage

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
PROCEEDINGS 1973 CARNAHAN CONFERENCE ON ELECTRONIC CRIME COUNTERMEASURES, April 25-27, 1973 Kentucky (US) F. SCHWARZ: "Design and application of a wide field, passive, infrared intrusion detector", pages 138-144 * page 140, left-hand column, line 7 to page 141, left-hand column, line 33; page 142, left-hand column, line 28 to right-hand column, last line * *

Cited By (13)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2542116A1 (fr) * 1983-02-25 1984-09-07 Verdon Roger Dispositif d'elimination des fausses alarmes
EP0189536A1 (de) * 1985-01-08 1986-08-06 Cerberus Ag Infrarot-Einbruchdetektor
EP0240657A1 (de) * 1986-03-24 1987-10-14 Fritz Fuss GmbH & Co. Verfahren zum Betreiben eines Bewegungsmelders
EP0289621A4 (de) * 1986-10-31 1990-07-03 Takenaka Eng Co Ltd Passives infrarot-einbruchmessfühler, ausgerüstet mit sichtfeldunterbrechungsüberwachungsmechanismus.
EP0289621A1 (de) * 1986-10-31 1988-11-09 Takenaka Engineering Co. Ltd. Passives infrarot-einbruchmessfühler, ausgerüstet mit sichtfeldunterbrechungsüberwachungsmechanismus
EP0274889A2 (de) * 1987-01-15 1988-07-20 Racal-Guardall (Scotland) Limited Sicherheitssensoren
EP0274889A3 (en) * 1987-01-15 1989-09-06 Racal-Guardall (Scotland) Limited Security sensors
EP0337964A1 (de) * 1988-04-13 1989-10-18 ELKRON S.p.A. Kombinierte Infrarot- und Mikrowellendetektorvorrichtung, insbesondere für Antiintrusionsanlagen
EP0375270A2 (de) * 1988-12-22 1990-06-27 Guardall Limited Einrichtung und Verfahren zur Strahlungserfassung
EP0375270A3 (de) * 1988-12-22 1991-07-10 Guardall Limited Einrichtung und Verfahren zur Strahlungserfassung
US5091648A (en) * 1988-12-22 1992-02-25 Racal-Guardall (Scotland) Limited Radiation detection arrangements and methods
EP0499177A1 (de) * 1991-02-11 1992-08-19 BITRON VIDEO S.r.l. Eindringmeldealarm
DE102006019941A1 (de) * 2006-04-28 2007-10-31 Pepperl + Fuchs Gmbh Vorrichtung und Verfahren zum Nachweis von Personen, Tieren oder Gegenständen

Also Published As

Publication number Publication date
GB1603306A (en) 1981-11-25

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PUAI Public reference made under article 153(3) epc to a published international application that has entered the european phase

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Inventor name: CRICK, DAVID WILLIAM