EP0186226B1 - Intrusion detection system with an anti-masking device - Google Patents

Intrusion detection system with an anti-masking device Download PDF

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Publication number
EP0186226B1
EP0186226B1 EP85201873A EP85201873A EP0186226B1 EP 0186226 B1 EP0186226 B1 EP 0186226B1 EP 85201873 A EP85201873 A EP 85201873A EP 85201873 A EP85201873 A EP 85201873A EP 0186226 B1 EP0186226 B1 EP 0186226B1
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EP
European Patent Office
Prior art keywords
detector
wavelength
detecting intruders
obscuring
emitter
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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.)
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EP85201873A
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German (de)
French (fr)
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EP0186226A1 (en
Inventor
Michel Steers
Jean-Pierre Hazan
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Laboratoires dElectronique Philips SAS
Koninklijke Philips NV
Original Assignee
Laboratoires dElectronique Philips SAS
Philips Gloeilampenfabrieken NV
Koninklijke Philips Electronics NV
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    • 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
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10S250/00—Radiant energy
    • Y10S250/01—Passive intrusion detectors

Definitions

  • the invention relates to an intruder detection device comprising, in a housing provided with at least one window, a passive infrared detector D1 detecting the radiation emitted by an intruder around a wavelength ⁇ 1 , and an anti-masking device detecting, using infrared radiation of wavelength ⁇ 2, the existence of masking of the intruder detection device, and electronic means intended to trigger an alarm when the presence an intruder or a masking has been detected.
  • An invention of this kind is known from GB-1 603 306.
  • a device for detecting intruders with passive infrared includes a pyroelectric detector, which detects the infrared emission produced by a living being and in particular that produced by an intruder entering an unauthorized space placed under surveillance.
  • the principle of such a device is to detect the variations in infrared emission which is obtained by segmenting the scanning of the area under surveillance using a network of mirrors which focus on the pyroelectric detector the infrared emission emitted. This emission has a maximum for wavelengths from 8 to 10 ⁇ m.
  • the drawback of a passive detection device is that it is possible to partially or totally mask such a device.
  • the patent GB-1 603 306 uses a system detecting a masking operation by using a second infrared radiation having a wavelength of 0.9 ⁇ m emitted by a transmitter and received by a receiver.
  • This 0.9 ⁇ m transmitter and receiver are placed in the same housing as the pyroelectric detector and use the same input window to operate.
  • the principle of this anti-masking is to use the reflection coefficient presented by the masking element. This can be a sheet of paper or metal, a rigid obstacle, a projection of a powdery product or others. In all these cases the light emitted at 0.9 ⁇ m by the emitter is reflected by the masking element and returned to the detector at 0.9 ⁇ m located nearby. When such a masking action is detected, electronic means activate an alarm.
  • the masking element may not have a sufficient reflection coefficient, that is to say absorb the radiation at 0.9 ⁇ m. It may for example be black paint. In this case the 0.9 ⁇ m detector will receive little or no light and will not detect the presence of the masking element.
  • the fixed arrangement of the transmitter and receiver at 0.9 ⁇ m, relative to each other means that, even in the case of a sufficient reflection coefficient, it is sufficient for the masking element is tilted to reflect light out of the direction of the detector. If the masking element is very close to the device, the chances that it will detect the masking are not zero. But if the masking element is placed at a significant distance, in the form of an obstruction, then it is unlikely that the reflected light will reach the detector at 0.9 ⁇ m. However, it is very easy to imagine situations where obstacles can be installed during a period when the device was inoperative. This is the case for public or semi-public places in which an intruder can enter during the day to perform a masking operation, when the system is stopped, and then return when the system has been restarted to monitor places then deserts.
  • the device will detect an absence of masking when no radiation at 0.9 ⁇ m has been detected by the detector at 0.9 ⁇ m. Now it is quite obvious that if either the transmitter or the detector breaks down, no signal will appear which will be interpreted as a non-masking situation.
  • the device according to this patent is therefore either unreliable or ineffective in a large number of conventional situations.
  • Document FR-2 520 123 also discloses a self-testing device intended for testing an optronic system. It comprises in a separate housing, which can be placed remotely, a light emitter which emits radiation which is transmitted by an optical fiber to a light detector either directly or through an optic. Additional optical test elements allow the light beam to be deflected. Test signals are used to check the operation of the optronic system.
  • the aims of the present invention are therefore to ensure that the device is reliable and operates for a high number of situations including the few cases which have just been mentioned.
  • the passive infrared detector D1, the emitter E2 and the detector D2 at the wavelength ⁇ 2, for example around 0.9 ⁇ m, are arranged in a box placed at a certain height, for example around the ceiling on a wall of an area under surveillance, and opposite the housing, at another end of the area under surveillance is arranged a reflector, for example a mirror M, so that the light emitted by the emitter E2, is reflected on the mirror M and returns to the detector D2.
  • the arrangement of these elements is adjusted at the start so that the light flux F received by the detector D2 is very precisely defined.
  • a masking element absorbing or deflecting the radiation ⁇ 2 so that the detector D2 receives a zero luminous flux, therefore different from the expected luminous flux F. It may also be a masking element reflecting the radiation ⁇ 2 to the detector D2 in which case the detector D2 receives a light flux greater than the expected light flux F.
  • a comparison device C2 is connected which determines whether the light flux received is equal or not to the expected light flux F. For this, an electronic window is defined formed by two reference values V1 and V2 between which the value of the received signal must lie.
  • the signal from the comparison device C2 is stored in a storage element, for example a flip-flop.
  • the signal emitted by the detector D2 is inside the electronic window, it changes the output of the flip-flop to a certain logical state. If, on the contrary, this signal is not understood inside the electronic window, the output of the flip-flop goes to the reverse logic state of the previous one. In the latter case, the scale operates, for example using a loop circuit, on an alarm center which then activates an audible or visual alarm.
  • the radiation ⁇ 2 which has a shorter wavelength than the radiation ⁇ :, is used for this anti-masking system because it is possible to obtain a directive beam which is detectable by the detector D2 after reflection on the mirror M.
  • the focusing of the beam is obtained for example using lenses, either molded plastic or glass.
  • a masking which may be at short or long distance from the housing.
  • This masking can be carried out in the form of a spraying of a product, or of an obstacle reflecting or obscuring the beam.
  • the transmitter E2 and the detector D2 are placed very close to the detector D1, so that a masking operation of the detector D1 also creates a masking of the detector D2 and the transmitter E2. It is of course obvious that the intruder will be tempted to mask only the detector D1 and to leave in operation the anti-masking system consisting of the transmitter E2 and the detector D2.
  • the window is produced in a material which constitutes a filter by stopping the visible part of the spectrum while letting the order lengths ⁇ and ⁇ : pass .
  • selective masking of the detector D1 becomes more difficult.
  • the intruder detection device has short-distance masking detection means consisting of an infrared emitter E1 operating at around the wavelength ⁇ 1 , this emitter being located very close to and in front of the window outside the box.
  • This emitter E1 is very small compared to the field of observation of the detector D1, so that it does not obscure the infrared beam which is emitted by the intruder.
  • This transmitter E1 tests at a very short distance the operation of the detector D1 and detects a masking of the window.
  • This emitter E1 is for example made up of a resistor deposited by screen printing on a very small alumina substrate, for example of dimensions 5 mm ⁇ 5 mm.
  • the transmitter E1 is put into operation for a limited time each time the intruder detection device is restarted. This start-up can be validated by the result of the comparison carried out by the comparison device C2.
  • the result of the comparison is stored in a storage element, and when the signal emitted by the detector D2 is inside the electronic window already defined, the storage element validates the activation of the transmitter E1. The output of the detector D1 can then validate in a central alarm the correct operating state of the masking detection means.
  • the transmitter E1 by simulating the existence of an intruder, could act to make the alarm of the alarm center work.
  • This therefore has means which modify the normal operation of the alarm center so that during the limited start-up period the alarm center interprets the existence of radiation at wavelength ⁇ :, as concerning a procedure for test and not as characterizing the presence of an intruder.
  • the description of the masking detection means which have just been described shows that a zero luminous flux received by the detectors D1 or D2 corresponds to a masking action of the device. This requires that all the constituent elements of the intruder detection device are in a correct operating state.
  • the intrusion detection device is provided with AUTOVER i fication means that tests the correct state of operation of transmitters E1 and E2 and detectors D1 and D2.
  • a generator delivers an electrical signal of limited duration which, as part of a start-up procedure, operates the transmitter E2 and the detector D2 on the one hand, then the transmitter E1 and the detector D1 of somewhere else.
  • the self-checking means comprise the masking detection means which have just been described, to which is added an element for validating the start-up procedure.
  • This validation element is for example a flip-flop which stores in the form of a logic state, the result of the start-up procedure operating on the channels ⁇ 1 and ⁇ 2 . Indeed, when the detector D2 has detected the X 2 radiation and when the detector D1 has detected the ⁇ 1 radiation, the alarm center receives information that no masking has been detected and that all of the components making up the two channels are in a correct operating state. The validation element stores this information and validates the following period corresponding to the permanent operation of the intruder detection device.
  • the operating principle is as follows. After a period of shutdown, the intruder detection device is restarted by the user.
  • the alarm center connected for example by a loop circuit to various intruder detection devices, sends a start signal to the generator which delivers a pulse of duration T.
  • This generator activates the transmitter E2 which supplies the radiation ⁇ 2 received by the detector D2.
  • the comparison device C2 compares the signal emitted by the detector D2 with the values of the electronic window. The result of the comparison is stored in a flip-flop during period T. If the signal sent is not included in the electronic window, the flip-flop acts on the alarm center which activates an alarm.
  • the flip-flop validates the activation of the transmitter E1 which supplies the radiation ⁇ 1 received by the detector D1.
  • the signal emitted by the detector D1 is stored in the validation element located in the alarm center. At the end of the period of duration T, depending on the logic state stored by the validation element, this validates the permanent operation of the detector D1 if the two channels ⁇ 1 and ⁇ 2 have operated correctly or, on the contrary, puts in operation the alarm of the alarm center if the operation of the two channels ⁇ 1 or ⁇ 2 has been disturbed.
  • the light beam of wavelength ⁇ 2 which is reflected by the mirror thus constitutes an optical barrier.
  • the masking and self-monitoring detection sequences are adapted to the number of infrared barriers thus arranged. This sequencing can be carried out in the generator of periodic electrical signals.
  • N the number
  • the generator delivers N signals of duration T consecutively. These signals actuate for example a counter or a shift register, which has N outputs each connected to a transmitter. Thus each transmitter is operated separately.
  • the comparison device C2 placed at the output of the single detector D2, detects as beforehand that each optical barrier has delivered its information.
  • the signal, at the output of the comparison device C2, representative of a value included within the limits of the electronic window, is used to actuate, for example a shift register with N stages, which in this way accounts for the N correct operating states. N optical barriers. By the logic state which appears at the end of the N periods at the output of the Nth register, the latter provides the information concerning the correct operating state of the N light barriers, and acts on the validation element of the alarm center.
  • N transmitters E2 and N detectors D2 it is also possible to use simultaneously N transmitters E2 and N detectors D2 in which case the validation element of the alarm center is activated only if the N light barriers have delivered information of a correct operating state.
  • the intruder detection device which has just been described is designed to make it difficult for an intruder to selectively mask the passive infrared detector D1.
  • the beams at ⁇ 2 and at ⁇ 1 must pass through the entry window so that the sections of the beams through the window are substantially superimposed.
  • the path of the two beams merge at the input of the intruder detection device so that it is impossible to mask one without masking the other.
  • the two beams are separated inside the housing using a dichroic mirror which returns one of the two beams and transmits the other beam.
  • the beam at 0.9 ⁇ m after being reflected by the mirror M placed at the end of the area under surveillance, arrives at the entry of the intruder detection device on a dichroic mirror inclined relative to the beam direction at 0.9 ⁇ m. This is thus diverted to the detector D2 placed for example in the housing.
  • the same self-checking means of the transmitter E2 and of the detector D2 exist as before.
  • a transmitter E3, analogous to the transmitter E1, and substituting for it, can be placed after the dichroic mirror inside the housing very close to the detector D1 so as to ensure only the means of self-checking. .
  • the masking detection means comprise the generator of electrical signals, the transmitter E2, the detector D2 and the comparison device C2.
  • the self-checking means include these masking detection means as well as the emitter E3, the detector D1 and the validation element.
  • the output signal from the comparison device C2 is stored in a flip-flop which controls the operation of the transmitter E3.
  • the detector D1 can be provided with a filter which stops low wavelengths, for example less than 5 ⁇ m, in order to reduce the electrical fluctuations constituting a noise which would appear at the output of detector D1.
  • the emitter E2 and the detector D2 can operate at other wavelengths situated in the infrared, for example 1.3 ⁇ m or 1.5 ⁇ m without departing from the scope of the invention.
  • the reflector preferably consists of a mirror. But it is also possible to use the reflecting power of other elements, for example the walls of the area under surveillance.
  • the mirror 20 is shown near the housing 10 but in reality it is located at a much more distant distance, that is to say at the end of the area placed under surveillance.
  • the directional beam 22 reflected by the mirror 20 arrives at the detector 13 through a focusing lens 14.
  • the detector D1 15 is located inside the housing 10 at the focus of a faceted mirror 16 which focuses the infrared beam coming from the intruder.
  • the detector D1 15 therefore receives by each element of the faceted mirror a beam similar to the beam 23.
  • the movement of the intruder allows this generation of different beams 23. It is these variations in received flux which allow the detector D1 to detect the presence of an intruder.
  • a high-pass filter 17 which cuts the wavelengths less than 5 ⁇ m for example. This allows the detector D1 to output an electrical signal where the noise component has been attenuated.
  • the emitter E1 18 which emits radiation at around the wavelength ⁇ t according to the beam 24. This is reflected on the faceted mirror 16 to reach the detector D1 15.
  • the emitter E1 18 is fixed integrally to the housing 10 using a fixing arm 25 which also carries the connection wires for the electrical signals.
  • the emitter E1 is small in size so as not to obscure the observation field of the detector D1 too much.
  • each reflected directive beam 22 arrives either on a single D2 detector 13, or on several identical D2 detectors according to the layout of the premises.
  • FIG. 2 an electrical block diagram of the intruder detection device is shown.
  • a generator 30 of an electrical signal of duration T actuates the emitter E2 12, the emitted radiation of which is detected by the detector D2 13.
  • the latter is connected at the output to a comparison device C2 32.
  • the comparison device C2 32 receives the output signal from detector D2 and compares it to two reference values V1 and V2. When the output signal of the detector D2 is between these two values, the comparison device C2 delivers a signal corresponding for example to the logic signal "1". Likewise, when the output signal of the detector D2 is outside this window of values, then the comparison device C2 delivers a signal corresponding to the reverse logic state of the previous state, ie "0" in the example.
  • FIG. 3 The time diagram for these different signals is represented in FIG. 3.
  • the signals present on the connections 35 and 36 of FIG. 2 are represented in FIG. 3 respectively under the reference 1 and under marks 2 and 3 depending on whether a masking action has not been or has been detected.
  • Signal 1 indicates that for a limited time T the transmitter E2 is operating.
  • the signal 2 of FIG. 3 appears, that is to say that the signal 1 was emitted by C2.
  • the signal 3 of FIG. 3 it is a lack of detection, that is to say a failure of E2 or D2, or of the fact that an action masking has been detected.
  • the output of flip-flop 37 activates the alarm of the central alarm 40 using the validation element 38.
  • flip-flop 37 activates the emitter E1 41 which supplies infrared radiation ⁇ 1 detected by the detector D1 42.
  • the output signal from the latter arrives at the validation element 38. If a signal has not been detected by the detector D1 42 , the validation element triggers the alarm of the alarm center. If on the contrary a signal has been detected the validation element 38 validates the end of the period of limited duration T which has the effect of giving back to the alarm center has autonomy to intervene in the event of detection of radiation at wavelength ⁇ 1 by the detector D1.
  • the intruder detection device is then in its permanent operating state to detect an intruder.
  • FIG. 4 represents a second variant of the intruder detection device. It differs from the previous one by the dichroic mirror 50 placed behind the entry window 11.
  • the reflected light beam 22 coming from the emitter E2 12 is reflected by the dichroic mirror 50 according to the beam 51 which arrives at the detector D2 13 of which the entry face has been directed towards the beam 51.
  • the beam 23 coming from the intruder crosses the dichroic mirror 50 to come to the detector D1 15 after having been reflected by the faceted mirror 16.
  • the two beams are therefore dissociated according to their wavelength.
  • the beams 22 and 23 passing through substantially the same part of the input window 11 any masking of the window will affect the two beams.
  • an E3 52 transmitter is placed inside the housing and only performs a self-checking function. The electrical operation remains the same.
  • the faceted mirror which segments the scanning of the area under surveillance can be replaced by a Fresnel lens.
  • the Fresnel lens is arranged, after the high-pass filter 17, substantially perpendicular to the beam 23, the detector D1 15 then facing the direction of arrival of the beam 23.

Description

L'invention concerne un dispositif de détection d'intrus comprenant, dans un boîtier muni d'au moins une fenêtre, un détecteur passif d'infrarouge D1 détectant le rayonnement émis par un intrus autour d'une longueur d'onde λ1, et un dispositif d'antimasquage détectant, à l'aide d'un rayonnement infrarouge de longueur d'onde λ2, l'existence d'un masquage du dispositif de détection d'intrus, et des moyens électroniques destinés à déclencher une alarme lorsque la présence d'un intrus ou d'un masquage a été détectée.The invention relates to an intruder detection device comprising, in a housing provided with at least one window, a passive infrared detector D1 detecting the radiation emitted by an intruder around a wavelength λ 1 , and an anti-masking device detecting, using infrared radiation of wavelength λ2, the existence of masking of the intruder detection device, and electronic means intended to trigger an alarm when the presence an intruder or a masking has been detected.

Une invention de ce genre est connue du brevet GB-1 603 306. Il y est décrit un dispositif de détection d'intrus à infrarouge passif. Il comporte un détecteur pyroélectrique, qui décèle l'émission infrarouge produite par un être vivant et en particulier celle produite par un intrus pénétrant dans un espace non-autorisé mis sous surveillance. Le principe d'un tel dispositif est de détecter les variations d'émission infrarouge ce qui est obtenu en segmentant la scrutation de la zone mise sous surveillance en utilisant un réseau de miroirs qui focalisent sur le détecteur pyroélectrique l'émission infrarouge émise. Cette émission présente un maximum pour des longueurs d'ondes de 8 à 10 µm.An invention of this kind is known from GB-1 603 306. There is described a device for detecting intruders with passive infrared. It includes a pyroelectric detector, which detects the infrared emission produced by a living being and in particular that produced by an intruder entering an unauthorized space placed under surveillance. The principle of such a device is to detect the variations in infrared emission which is obtained by segmenting the scanning of the area under surveillance using a network of mirrors which focus on the pyroelectric detector the infrared emission emitted. This emission has a maximum for wavelengths from 8 to 10 µm.

Mais l'inconvénient d'un dispositif de détection passif est qu'il est possible de masquer partiellement ou totalement un tel dispositif. Pour remédier à cet inconvénient, le brevet GB-1 603 306 utilise un système détectant une opération de masquage en utilisant un second rayonnement infrarouge ayant une longueur d'onde de 0,9 µm émis par un émetteur et reçu par un récepteur. Cet emétteur et ce récepteur à 0,9 µm sont placés dans le même boîtier que le détecteur pyroélectrique et utilisent, pour fonctionner, la même fenêtre d'entrée. Le principe de cet antimasquage est d'exploiter le coefficient de réflexion que présente l'élément masquant. Celui-ci peut être une feuille de papier ou de métal, un obstacle rigide, une projection d'un produit pulvérulent ou autres. Dans tous ces cas la lumière émise à 0,9 µm par l'émetteur se trouve réfléchie par l'élément masquant et renvoyée vers le détecteur à 0,9 µm situé à proximité. Lorsqu'une telle action de masquage est détectée des moyens électroniques mettent en fonctionnement une alarme.However, the drawback of a passive detection device is that it is possible to partially or totally mask such a device. To remedy this drawback, the patent GB-1 603 306 uses a system detecting a masking operation by using a second infrared radiation having a wavelength of 0.9 μm emitted by a transmitter and received by a receiver. This 0.9 µm transmitter and receiver are placed in the same housing as the pyroelectric detector and use the same input window to operate. The principle of this anti-masking is to use the reflection coefficient presented by the masking element. This can be a sheet of paper or metal, a rigid obstacle, a projection of a powdery product or others. In all these cases the light emitted at 0.9 µm by the emitter is reflected by the masking element and returned to the detector at 0.9 µm located nearby. When such a masking action is detected, electronic means activate an alarm.

Or les manières selon lesquelles une opération de masquage peut être effectuée sont multiples et beaucoup de ces manières ne sont nullement décelées par le dispositif décrit dans le brevet GB-1 603 306.However, the ways in which a masking operation can be carried out are multiple and many of these ways are in no way detected by the device described in patent GB-1,603,306.

En effet, l'élément masquant peut ne pas présenter un coefficient de réflexion suffisant, c'est-à-dire absorber le rayonnement à 0,9 µm. Il peut s'agir par exemple de peinture noire. Dans ce cas le détecteur à 0,9 µm ne recevra pas ou peu de lumière et ne détectera pas la présence de l'élément masquant.In fact, the masking element may not have a sufficient reflection coefficient, that is to say absorb the radiation at 0.9 μm. It may for example be black paint. In this case the 0.9 µm detector will receive little or no light and will not detect the presence of the masking element.

De même, la disposition fixe de l'émetteur et du récepteur à 0,9 µm, l'un par rapport à l'autre, fait que, même en cas d'un coefficient de réflexion suffisant, il suffit que l'élément masquant soit incliné pour réfléchir la lumière hors de la direction du détecteur. Si l'élément masquant est très près du dispositif les chances pour qu'il détecte le masquage ne sont pas nulles. Mais si l'élément masquant est disposé à une distance non négligeable, sous la forme d'un obstable, alors il est peu probable que la lumière réfléchie atteigne le détecteur à 0,9 µm. Or, il est très facile d'imaginer des situations où des obstacles peuvent être installés pendant une période où le dispositif était inopérant. Il en va ainsi de lieux publics ou semi-publics dans lesquels un intrus peut s'introduire dans la journée pour effectuer une opération de masquage, lorsque le système est arrêté, et revenir ensuite lorsque le système aura été remis en fonctionnement pour surveiller des lieux alors déserts.Likewise, the fixed arrangement of the transmitter and receiver at 0.9 µm, relative to each other, means that, even in the case of a sufficient reflection coefficient, it is sufficient for the masking element is tilted to reflect light out of the direction of the detector. If the masking element is very close to the device, the chances that it will detect the masking are not zero. But if the masking element is placed at a significant distance, in the form of an obstruction, then it is unlikely that the reflected light will reach the detector at 0.9 µm. However, it is very easy to imagine situations where obstacles can be installed during a period when the device was inoperative. This is the case for public or semi-public places in which an intruder can enter during the day to perform a masking operation, when the system is stopped, and then return when the system has been restarted to monitor places then deserts.

D'autre part, selon le brevet GB-1 603 306, le dispositif détectera une absence de masquage lorsqu'aucun rayonnement à 0,9 µm n'aura été détecté par le détecteur à 0,9 µm. Or il est bien évident que si, soit l'émetteur, soit le détecteur tombe en panne, aucun signal n'apparaîtra ce qui sera interprété comme une situation de non-masquage.On the other hand, according to patent GB-1 603 306, the device will detect an absence of masking when no radiation at 0.9 μm has been detected by the detector at 0.9 μm. Now it is quite obvious that if either the transmitter or the detector breaks down, no signal will appear which will be interpreted as a non-masking situation.

Le dispositif selon ce brevet est donc soit peu fiable soit inopérant dans un grand nombre de situations classiques.The device according to this patent is therefore either unreliable or ineffective in a large number of conventional situations.

On connaît également du document FR-2 520 123 un dispositif d'autest destiné à tester un système optronique. Il comporte dans un boîtier indépendant, qui peut être placé à distance, un émetteur de lumière qui émet un rayonnement qui est transmis par une fibre optique à un détecteur de lumière soit directement soit à travers une optique. Des éléments optiques additionnels de test permettent de dévier le faisceau lumineux. Des signaux de test permettent de vérifier le fonctionnement du système optronique.Document FR-2 520 123 also discloses a self-testing device intended for testing an optronic system. It comprises in a separate housing, which can be placed remotely, a light emitter which emits radiation which is transmitted by an optical fiber to a light detector either directly or through an optic. Additional optical test elements allow the light beam to be deflected. Test signals are used to check the operation of the optronic system.

Les buts de la présente invention sont donc de faire que le dispositif soit fiable et opère pour un nombre élevé de situations comprenant les quelques cas qui viennent d'être cités.The aims of the present invention are therefore to ensure that the device is reliable and operates for a high number of situations including the few cases which have just been mentioned.

Pour cela, l'invention telle que définie dans le préambule est remarquable en ce que le disposi- tif de détection d'intrus comprend:

  • - des moyens de détection de masquage situé à courte et à grande distance, masquage modifiant l'intensité des flux lumineux traversant la fenêtre,
  • - et des moyens d'autovérification.
For this, the invention as defined in the preamble is characterized in that the provi- t i f intruder detection comprises:
  • - masking detection means located at short and long distance, masking modifying the intensity of the light fluxes passing through the window,
  • - and means of Autover i fication.

Pour cela le détecteur passif d'infrarouge D1, l'émetteur E2 et le détecteur D2 à la longueur d'onde λ2, par exemple environ 0,9 µm, sont disposés dans un boîtier placé à une certaine hauteur, par exemple aux environs du plafond sur une paroi d'une zone mise sous surveillance, et en face du boîtier, à une autre extrémité de la zone mise sous surveillance est disposé un réflecteur, par exemple un miroir M, de telle sorte que la lumière émise par l'émetteur E2, se réfléchit sur le miroir M et revient sur le détecteur D2. La disposition de ces éléments est réglée au départ de sorte que le flux lumineux F reçu par le détecteur D2 se trouve très exactement défini.For this, the passive infrared detector D1, the emitter E2 and the detector D2 at the wavelength λ2, for example around 0.9 μm, are arranged in a box placed at a certain height, for example around the ceiling on a wall of an area under surveillance, and opposite the housing, at another end of the area under surveillance is arranged a reflector, for example a mirror M, so that the light emitted by the emitter E2, is reflected on the mirror M and returns to the detector D2. The arrangement of these elements is adjusted at the start so that the light flux F received by the detector D2 is very precisely defined.

Ainsi plusieurs situations de masquage peuvent être détectées. Il peut s'agir d'un élément masquant absorbant ou déviant le rayonnement λ2 de sorte que le détecteur D2 reçoit un flux lumineux nul, donc différent du flux lumineux F attendu. Il peut également s'agir d'un élément masquant réfléchissant le rayonnement λ2 vers le détecteur D2 auquel cas le détecteur D2 reçoit un flux lumineux supérieur au flux lumineux F attendu. A la sortie du détecteur D2, est connecté un dispositif de comparaison C2 qui détermine si le flux lumineux reçu est égal ou non au flux lumineux F attendu. On définit pour cela une fenêtre électronique formée de deux valeurs de référence V1 et V2 entre lesquelles doit se trouver la valeur du signal reçu. Le signal issu du dispositif de comparaison C2 est stocké dans un élément de stockage par exemple une bascule. Si le signal émis par le détecteur D2 est à l'intérieur de la fenêtre électronique, il fait passer la sortie de la bascule à un certain état logique. Si au contraire ce signal n'est pas compris à l'intérieur de la fenêtre électronique, la sortie de la bascule passe à l'état logique inverse du précédent. Dans ce dernier cas la bascule agit, par exemple à l'aide d'un circuit en boucle, sur une centrale d'alarme qui met alors en fonctionnement une alarme sonore ou visuelle.Thus, several masking situations can be detected. It may be a masking element absorbing or deflecting the radiation λ2 so that the detector D2 receives a zero luminous flux, therefore different from the expected luminous flux F. It may also be a masking element reflecting the radiation λ 2 to the detector D2 in which case the detector D2 receives a light flux greater than the expected light flux F. At the output of the detector D2, a comparison device C2 is connected which determines whether the light flux received is equal or not to the expected light flux F. For this, an electronic window is defined formed by two reference values V1 and V2 between which the value of the received signal must lie. The signal from the comparison device C2 is stored in a storage element, for example a flip-flop. If the signal emitted by the detector D2 is inside the electronic window, it changes the output of the flip-flop to a certain logical state. If, on the contrary, this signal is not understood inside the electronic window, the output of the flip-flop goes to the reverse logic state of the previous one. In the latter case, the scale operates, for example using a loop circuit, on an alarm center which then activates an audible or visual alarm.

Le rayonnement λ2, qui a une plus courte longueur d'onde que le rayonnement λ:, est utilisé pour ce système d'antimasquage car il est possible d'en obtenir un faisceau directif qui est détectable par le détecteur D2 après réflexion sur le miroir M. La focalisation du faisceau est obtenue par exemple à l'aide de lentilles, soit en plastique moulé, soit en verre.The radiation λ 2 , which has a shorter wavelength than the radiation λ :, is used for this anti-masking system because it is possible to obtain a directive beam which is detectable by the detector D2 after reflection on the mirror M. The focusing of the beam is obtained for example using lenses, either molded plastic or glass.

On dispose ainsi de moyens de détection d'un masquage qui peut être à courte ou à grande distance du boîtier. Ce masquage peut être réalisé sous la forme d'une pulvérisation d'un produit, ou d'un obstacle réfléchissant ou occultant le faisceau.There are thus means for detecting a masking which may be at short or long distance from the housing. This masking can be carried out in the form of a spraying of a product, or of an obstacle reflecting or obscuring the beam.

L'émetteur E2 et le détecteur D2 sont placés très près du détecteur D1, de sorte qu'une opération de masquage du détecteur D1 crée aussi un masquage du détecteur D2 et de l'émetteur E2. Il est bien sûr évident que l'intrus sera tenté de ne masquer que le détecteur D1 et de laisser en fonctionnement le système d'antimasquage constitué de l'émetteur E2 et du détecteur D2.The transmitter E2 and the detector D2 are placed very close to the detector D1, so that a masking operation of the detector D1 also creates a masking of the detector D2 and the transmitter E2. It is of course obvious that the intruder will be tempted to mask only the detector D1 and to leave in operation the anti-masking system consisting of the transmitter E2 and the detector D2.

Pour diminuer l'efficacité d'une telle intervention, selon l'invention, on réalise la fenêtre dans un matériau qui constitue un filtre en arrêtant la partie visible du spectre tout en laissant passer les longueurs d'ordes λ≥ et λ:. Ainsi un masquage sélectif du détecteur D1 devient plus difficile. Mais dans des conditions particulières, par exemple par la connaissance détaillée du matériel, l'intrus peut chercher à effectuer ce masquage sélectif. Selon l'invention, le dispositif de détection d'intrus présente des moyens de détection de masquage à courte distance constitués d'un émetteur d'infrarouge E1 opérant aux environs de la longueur d'onde λ1, cet émetteur étant situé très près et devant la fenêtre à l'extérieur du boîtier. Cet émetteur E1 est de très petites dimensions par rapport au champ d'observation du détecteur D1, de sorte qu'il n'occulte pas le faisceau d'infrarouge qui est émis par l'intrus. Cet émetteur E1 teste à très courte distance le fonctionnement du détecteur D1 et détecte un masquage de la fenêtre. Cet émetteur E1 est par exemple constitué d'une résistance déposée par sérigraphie sur un très petit substrat d'alumine par exemple de dimensions 5 mm x 5 mm. L'émetteur E1 est mis en fonctionnement pour une durée limitée à chaque remise en route du dispositif de détection d'intrus. Cette mise en fonctionnement peut être validée par le résultat de la comparaison effectuée par le dispositif de comparaison C2. Le résultat de la comparaison est stocké dans un élément de stockage, et lorsque le signal émis par le détecteur D2 est à l'intérieur de la fenêtre électronique déjà définie, l'élément de stockage valide la mise en fonctionnement de l'émetteur E1. La sortie du détecteur D1 peut alors valider dans une centrale d'alarme l'état de fonctionnement correct des moyens de détection du masquage.To reduce the effectiveness of such an intervention, according to the invention, the window is produced in a material which constitutes a filter by stopping the visible part of the spectrum while letting the order lengths λ≥ and λ : pass . Thus, selective masking of the detector D1 becomes more difficult. But under special conditions, for example by detailed knowledge of the material, the intruder may seek to effect this selective masking. According to the invention, the intruder detection device has short-distance masking detection means consisting of an infrared emitter E1 operating at around the wavelength λ 1 , this emitter being located very close to and in front of the window outside the box. This emitter E1 is very small compared to the field of observation of the detector D1, so that it does not obscure the infrared beam which is emitted by the intruder. This transmitter E1 tests at a very short distance the operation of the detector D1 and detects a masking of the window. This emitter E1 is for example made up of a resistor deposited by screen printing on a very small alumina substrate, for example of dimensions 5 mm × 5 mm. The transmitter E1 is put into operation for a limited time each time the intruder detection device is restarted. This start-up can be validated by the result of the comparison carried out by the comparison device C2. The result of the comparison is stored in a storage element, and when the signal emitted by the detector D2 is inside the electronic window already defined, the storage element validates the activation of the transmitter E1. The output of the detector D1 can then validate in a central alarm the correct operating state of the masking detection means.

Il est bien évident que l'émetteur E1, en simulant l'existence d'un intrus, pourrait agir pour faire fonctionner l'alarme de la centrale d'alarme. Celle-ci possède donc des moyens qui modifient la fonctionnement normal de la centrale d'alarme afin que pendant la période limitée de démarrage la centrale d'alarme interprète l'existence du rayonnement à longueur d'onde λ:, comme concernant une procédure de test et non comme caractérisant la présence d'un intrus.It is obvious that the transmitter E1, by simulating the existence of an intruder, could act to make the alarm of the alarm center work. This therefore has means which modify the normal operation of the alarm center so that during the limited start-up period the alarm center interprets the existence of radiation at wavelength λ :, as concerning a procedure for test and not as characterizing the presence of an intruder.

La description des moyens de détection de masquage qui viennent d'être décrits montre qu'un flux lumineux nul reçu par les détecteurs D1 ou D2 correspond à une action de masquage du dispositif. Ceci nécessite que tous les éléments constitutifs du dispositif de détection d'intrus soient dans un état correct de fonctionnement.The description of the masking detection means which have just been described shows that a zero luminous flux received by the detectors D1 or D2 corresponds to a masking action of the device. This requires that all the constituent elements of the intruder detection device are in a correct operating state.

Pour cela, le dispositif de détection d'intrus est muni de moyens d'autovérification qui teste l'état correct de fonctionnement des émetteurs E1 et E2 et des détecteurs D1 et D2. Pour cela, un générateur délivre un signal électrique de durée limitée qui, dans le cadre d'une procédure de démarrage, fait fonctionner l'émetteur E2 et le détecteur D2 d'une part, puis l'émetteur E1 et le détecteur D1 d'autre part.For this, the intrusion detection device is provided with AUTOVER i fication means that tests the correct state of operation of transmitters E1 and E2 and detectors D1 and D2. For this, a generator delivers an electrical signal of limited duration which, as part of a start-up procedure, operates the transmitter E2 and the detector D2 on the one hand, then the transmitter E1 and the detector D1 of somewhere else.

Selon un premier mode préférentiel de réalisation les moyens d'autovérification comprennent les moyens de détection de masquage qui viennent d'être décrits auxquels s'ajoutent un élément de validation de la procédure de démarrage. Cet élément de validation est par exemple une bascule qui stocke sous la forme d'un état logique, le résultat de la procédure de démarrage opérant sur les voies λ1 et λ2. En effet, lorsque le détecteur D2 a détecté le rayonnement X2 et lorsque le détecteur D1 a détecté le rayonnement λ1, la centrale d'alarme reçoit l'information qu'aucun masquage n'a été détecté et que l'ensemble des composants constituant les deux voies sont dans un état de fonctionnement correct. L'élément de validation stocke cette information et valide la période suivante correspondant au fonctionnement permanent du dispositif de détection d'intrus.According to a first preferred embodiment, the self-checking means comprise the masking detection means which have just been described, to which is added an element for validating the start-up procedure. This validation element is for example a flip-flop which stores in the form of a logic state, the result of the start-up procedure operating on the channels λ 1 and λ 2 . Indeed, when the detector D2 has detected the X 2 radiation and when the detector D1 has detected the λ 1 radiation, the alarm center receives information that no masking has been detected and that all of the components making up the two channels are in a correct operating state. The validation element stores this information and validates the following period corresponding to the permanent operation of the intruder detection device.

Le principe de fonctionnement est le suivant. Après une période d'arrêt, le dispositif de détection d'intrus est remis en fonctionnement par l'utilisateur. La centrale d'alarme, reliée par exemple par un circuit en boucle à différents dispositifs de détection d'intrus, envoie un signal de démarrage au générateur qui délivre une impulsion de durée T. Ce générateur met en fonctionnement l'émetteur E2 qui fournit le rayonnement λ2 reçu par le détecteur D2. Le dispositif de comparaison C2 compare le signal émis par le détecteur D2 aux valeurs de la fenêtre électronique. Le résultat de la comparaison est stocké dans une bascule durant la période T. Si le signal émis n'est pas compris dans la fenêtre électronique, la bascule agit sur la centrale d'alarme qui met en fonctionnement une alarme. Si le signal émis est compris dans la fenêtre électronique la bascule valide la mise en fonctionnement de l'émetteur E1 qui fournit le rayonnement λ1 reçu par le détecteur D1. Le signal émis par le détecteur D1 est stocké dans l'élément de validation situé dans la centrale d'alarme. A l'issue de la période de durée T, selon l'état logique stocké par l'élément de validation celui-ci valide la mise en fonctionnement permanent du détecteur D1 si les deux voies λ1 et λ2 ont opéré correctement ou au contraire met en fonctionnement l'alarme de la centrale d'alarme si le fonctionnement des deux voies λ1 ou λ2 a été perturbé.The operating principle is as follows. After a period of shutdown, the intruder detection device is restarted by the user. The alarm center, connected for example by a loop circuit to various intruder detection devices, sends a start signal to the generator which delivers a pulse of duration T. This generator activates the transmitter E2 which supplies the radiation λ 2 received by the detector D2. The comparison device C2 compares the signal emitted by the detector D2 with the values of the electronic window. The result of the comparison is stored in a flip-flop during period T. If the signal sent is not included in the electronic window, the flip-flop acts on the alarm center which activates an alarm. If the transmitted signal is included in the electronic window, the flip-flop validates the activation of the transmitter E1 which supplies the radiation λ 1 received by the detector D1. The signal emitted by the detector D1 is stored in the validation element located in the alarm center. At the end of the period of duration T, depending on the logic state stored by the validation element, this validates the permanent operation of the detector D1 if the two channels λ 1 and λ2 have operated correctly or, on the contrary, puts in operation the alarm of the alarm center if the operation of the two channels λ 1 or λ2 has been disturbed.

Le faisceau lumineux de longueur d'onde λ2 qui est réfléchi par le miroir constitue ainsi une barrière optique. Selon la topologie des lieux à surveiller et pour accroître l'efficacité de la surveillance il est possible de disposer plusieurs miroirs, remplissant des fonctions identiques, placés à différentes extrémités et à différentes hauteurs dans la zone mise sous surveillance. Dans ce cas les séquences de détection de masquage et d'autosurveillance sont adaptées au nombre de barrières infrarouge ainsi disposées. Ce séquencement peut être effectué dans le générateur de signaux électriques périodiques.The light beam of wavelength λ 2 which is reflected by the mirror thus constitutes an optical barrier. Depending on the topology of the places to be monitored and to increase the effectiveness of the surveillance, it is possible to have several mirrors, fulfilling identical functions, placed at different ends and at different heights in the area under surveillance. In this case, the masking and self-monitoring detection sequences are adapted to the number of infrared barriers thus arranged. This sequencing can be carried out in the generator of periodic electrical signals.

Dans le cas où il existe plusieurs miroirs (soit N le nombre), disposés à des endroits différents de la zone mise sous surveillance, il est avantageux d'utiliser N émetteurs E2 associés au même détecteur D2. Ceci est possible dans la mesure où les N faisceaux directifs émis par les N émetteurs E2 peuvent atteindre le même détecteur D2. Dans ce cas le générateur délivre consécutivement N signaux de durée T. Ces signaux actionnent par exemple un compteur ou un registre à décalage, qui présente N sorties reliées chacune à un émetteur. Ainsi chaque émetteur est mis en fonctionnement séparément. Le dispositif de comparaison C2, placé à la sortie du détecteur D2 unique, détecte comme préalablement que chaque barrière optique a délivré son information. Le signal, en sortie du dispositif de comparaison C2, représentatif d'une valeur comprise dans les limites de la fenêtre électronique, sert à actionner, par exemple un registre à décalage à N étages, qui de la sorte comptabilise les N états corrects de fonctionnement des N barrières optiques. Par l'état logique qui apparaît à l'issue des N périodes à la sortie du Nième registre, celui-ci fournit l'information concernant l'état de fonctionnement correct des N barrières optiques, et agit sur l'élément de validation de la centrale d'alarme.In the case where there are several mirrors (ie N the number), placed at different places in the area under surveillance, it is advantageous to use N emitters E2 associated with the same detector D2. This is possible insofar as the N directional beams emitted by the N emitters E2 can reach the same detector D2. In this case, the generator delivers N signals of duration T consecutively. These signals actuate for example a counter or a shift register, which has N outputs each connected to a transmitter. Thus each transmitter is operated separately. The comparison device C2, placed at the output of the single detector D2, detects as beforehand that each optical barrier has delivered its information. The signal, at the output of the comparison device C2, representative of a value included within the limits of the electronic window, is used to actuate, for example a shift register with N stages, which in this way accounts for the N correct operating states. N optical barriers. By the logic state which appears at the end of the N periods at the output of the Nth register, the latter provides the information concerning the correct operating state of the N light barriers, and acts on the validation element of the alarm center.

Il est également possible d'utiliser simultanément N émetteurs E2 et N détecteurs D2 auquel cas l'élément de validation de la centrale d'alarme n'est activé que si les N barrières optiques ont délivré une information d'un état correct de fonctionnement.It is also possible to use simultaneously N transmitters E2 and N detectors D2 in which case the validation element of the alarm center is activated only if the N light barriers have delivered information of a correct operating state.

Le dispositif de détection d'intrus qui vient d'être décrit est conçu pour rendre difficile à un intrus la possibilité de masquer sélectivement le détecteur D1 à infrarouge passif. Selon un autre mode de réalisation, pour atteindre respectivement les détecteurs D2 et D1, les faisceaux à λ2 et à λ1 doivent traverser la fenêtre d'entrée de tel le sorte que les sections des faisceaux par la fenêtre soient sensiblement superposées.The intruder detection device which has just been described is designed to make it difficult for an intruder to selectively mask the passive infrared detector D1. According to another embodiment, to reach the detectors D2 and D1 respectively, the beams at λ 2 and at λ 1 must pass through the entry window so that the sections of the beams through the window are substantially superimposed.

Ainsi le trajet des deux faisceaux se confondent en entrée du dispositif de détection d'intrus de sorte qu'il est impossible de masquer l'un sans masquer l'autre. Les deux faisceaux sont séparés à l'intérieur du boîtier à l'aide d'un miroir dichroïque qui renvoie l'un des deux faisceaux et transmet l'autre faisceau.Thus the path of the two beams merge at the input of the intruder detection device so that it is impossible to mask one without masking the other. The two beams are separated inside the housing using a dichroic mirror which returns one of the two beams and transmits the other beam.

Par exemple le faisceau à 0,9 p m, après avoir été réfléchi par le miroir M placé à l'extrémité de la zone mise sous surveillance, arrive à l'entrée du dispositif de détection d'intrus sur un miroir dichroïque incliné par rapport à la direction du faisceau à 0,9 pm. Celui-ci est ainsi dévié vers le détecteur D2 placé par exemple dans le boîtier. Les mêmes moyens d'autovérification de l'émetteur E2 et du détecteur D2 existent comme précédemment. Selon cette autre variante un émetteur E3, analogue à l'émetteur E1, et se substituant à lui, peut être placé après le miroir dichroïque à l'intérieur du boîtier très près du détecteur D1 pour n'assurer alors que les moyens d'autovérification.For example, the beam at 0.9 μm, after being reflected by the mirror M placed at the end of the area under surveillance, arrives at the entry of the intruder detection device on a dichroic mirror inclined relative to the beam direction at 0.9 µm. This is thus diverted to the detector D2 placed for example in the housing. The same self-checking means of the transmitter E2 and of the detector D2 exist as before. According to this other variant, a transmitter E3, analogous to the transmitter E1, and substituting for it, can be placed after the dichroic mirror inside the housing very close to the detector D1 so as to ensure only the means of self-checking. .

Selon cette seconde variante les moyens de détection de masquage comprennent le générateur de signaux électriques, l'émetteur E2, le détecteur D2 et le dispositif de comparaison C2. Les moyens d'autovérification comprennent ces moyens de détection de masquage ainsi que l'émetteur E3, le détecteur D1 et l'élément de validation. Le signal de sortie du dispositif de comparaison C2 est stocké dans une bascule qui contrôle le fonctionnement de l'émetteur E3.According to this second variant, the masking detection means comprise the generator of electrical signals, the transmitter E2, the detector D2 and the comparison device C2. The self-checking means include these masking detection means as well as the emitter E3, the detector D1 and the validation element. The output signal from the comparison device C2 is stored in a flip-flop which controls the operation of the transmitter E3.

Bien évidemment, selon des principes connus de l'homme de l'art, le détecteur D1 peut être muni d'un filtre qui arrête les longueurs d'ondes basses, par exemple inférieures à 5 um, afin de diminuer les fluctuations électriques constituant un bruit qui apparaîtraient en sortie du détecteur D1.Obviously, according to principles known to those skilled in the art, the detector D1 can be provided with a filter which stops low wavelengths, for example less than 5 μm, in order to reduce the electrical fluctuations constituting a noise which would appear at the output of detector D1.

De méme, la segmentation des zones mises sous surveillance a précédemment été indiquée comme étant effectuée à l'aide de miroirs à facettes. Il est bien sûr possible d'opérer une fonction analogue à l'aide de lentilles de Fresnel.Likewise, the segmentation of the areas under surveillance has previously been indicated as being carried out using faceted mirrors. It is of course possible to operate a similar function using Fresnel lenses.

L'émetteur E2 et le détecteur D2 peuvent opérer à d'autres longueurs d'ondes situées dans l'infrarouge, par exemple 1,3 µm ou 1,5 µm sans sortir du cadre de l'invention.The emitter E2 and the detector D2 can operate at other wavelengths situated in the infrared, for example 1.3 μm or 1.5 μm without departing from the scope of the invention.

De même, il a été indiqué que le réflecteur était constitué préférentiellement d'un miroir. Mais il est également possible d'utiliser le pouvoir réfléchissant d'autres éléments, par exemple les murs de la zone mise sous surveillance.Likewise, it has been indicated that the reflector preferably consists of a mirror. But it is also possible to use the reflecting power of other elements, for example the walls of the area under surveillance.

L'invention sera mieux comprise à l'aide des figures suivantes, données à titre d'exemples non limitatifs qui représentent:

  • - figure 1: une représentation schématique d'un dispositif de détection d'intrus selon l'invention,
  • - figure 2: un schéma-bloc électrique du dispositif de détection d'intrus,
  • - figure 3: un diagramme des temps pour les signaux détectés avec ou sans masquage,
  • - figure 4: une autre variante du dispositif de détection d'intrus comportant un miroir di- chrdique.

Sur la figure 1 est représenté un dispositif de détection d'intrus comprenant un boîtier 10 muni d'une fenêtre 11. A l'intérieur du boîtier 10 sont disposés un émetteur E2 12 et un détecteur D2 13 d'un rayonnement à un longueur d'onde X2 = 0,9 um. Devant l'émetteur E2 12 et le détecteur D2 13 se trouvent des lentilles de focalisation 14 destinées à focaliser les faisceaux. L'émetteur E2 12 émet un faisceau directif 21 vers le miroir 20 placé à l'extrémité de la zone mise sous surveillance.The invention will be better understood using the following figures, given by way of non-limiting examples which represent:
  • FIG. 1: a schematic representation of an intruder detection device according to the invention,
  • - Figure 2: an electrical block diagram of the intruder detection device,
  • - Figure 3: a time diagram for the signals detected with or without masking,
  • - Figure 4: another variant of the intruder detection device comprising a digital mirror.

In Figure 1 is shown an intruder detection device comprising a housing 10 provided with a window 11. Inside the housing 10 are arranged an emitter E2 12 and a detector D2 13 of radiation at a length d wave X 2 = 0.9 µm. In front of the transmitter E2 12 and the detector D2 13 there are focusing lenses 14 intended to focus the beams. The transmitter E2 12 emits a directional beam 21 towards the mirror 20 placed at the end of the zone placed under surveillance.

Pour des raisons de commodité de présentation de la figure, le miroir 20 est représenté près du boîtier 10 mais dans la réalité il est situé à une distance beaucoup plus éloignée, c'est-à-dire à l'extrémité de la zone mise sous surveillance. Le faisceau directif 22 réfléchi par le miroir 20 arrive sur le détecteur 13 à travers une lentille de focalisation 14.For reasons of convenience of presentation of the figure, the mirror 20 is shown near the housing 10 but in reality it is located at a much more distant distance, that is to say at the end of the area placed under surveillance. The directional beam 22 reflected by the mirror 20 arrives at the detector 13 through a focusing lens 14.

Le détecteur D1 15 se trouve à l'intérieur du boîtier 10 au foyer d'un miroir à facettes 16 qui focalise le faisceau infrarouge issu de l'intrus. Le détecteur D1 15 reçoit donc par chaque élément du miroir à facettes un faisceau analogue au faisceau 23. Le mouvement de l'intrus permet cette génération de faisceaux 23 différants. Ce sont ces variations de flux reçu qui permettent au détecteur D1 de déceler la présence d'un intrus. Devant le détecteur D1 est disposé un filtre passe-haut 17 qui coupe les longueurs d'ondes inférieures par exemple à 5 µm. Ceci permet au détecteur D1 de fournir en sortie un signal électrique où la composante de bruit a été atténuée.The detector D1 15 is located inside the housing 10 at the focus of a faceted mirror 16 which focuses the infrared beam coming from the intruder. The detector D1 15 therefore receives by each element of the faceted mirror a beam similar to the beam 23. The movement of the intruder allows this generation of different beams 23. It is these variations in received flux which allow the detector D1 to detect the presence of an intruder. In front of the detector D1 is placed a high-pass filter 17 which cuts the wavelengths less than 5 μm for example. This allows the detector D1 to output an electrical signal where the noise component has been attenuated.

A l'extérieur du boîtier 10 et très près de la fenêtre 11 est disposé l'émetteur E1 18 qui émet un rayonnement aux environs de la longueur d'onde λt selon le faisceau 24. Celui-ci se réfléchit sur le miroir à facettes 16 pour atteindre le détecteur D1 15. L'émetteur E1 18 est fixé solidairement au boîtier 10 à l'aide d'un bras de fixation 25 qui porte également les fils de connexion pour les signaux électriques. L'émetteur E1 est de petites dimensions pour ne pas trop occulter le champ d'observation du détecteur D1.Outside the box 10 and very close to the window 11 is placed the emitter E1 18 which emits radiation at around the wavelength λt according to the beam 24. This is reflected on the faceted mirror 16 to reach the detector D1 15. The emitter E1 18 is fixed integrally to the housing 10 using a fixing arm 25 which also carries the connection wires for the electrical signals. The emitter E1 is small in size so as not to obscure the observation field of the detector D1 too much.

Dans une installation à plusieurs miroirs 20 ceux-ci sont disposés aux différentes extrémités de la zone mise sous surveillance, et orientés de telle sorte que différents émetteurs E2 12 fournissent un faisceau directif 21 sur chaque miroir 20. Chaque faisceau directif réfléchi 22 arrive soit sur un détecteur D2 13 unique, soit sur plusieurs détecteurs D2 identiques selon la disposition des lieux.In an installation with several mirrors 20, these are arranged at the different ends of the area under surveillance, and oriented so that different emitters E2 12 provide a directive beam 21 on each mirror 20. Each reflected directive beam 22 arrives either on a single D2 detector 13, or on several identical D2 detectors according to the layout of the premises.

Sur la figure 2, est représenté un schéma-bloc électrique du dispositif de détection d'intrus. Un générateur 30 d'un signal électrique de durée T actionne l'émetteur E2 12 dont le rayonnement émis est détecté par le détecteur D2 13. Celui-ci est réuni en sortie à un dispositif de comparaison C2 32. Le dispositif de comparaison C2 32 reçoit le signal de sortie du détecteur D2 et le compare à deux valeurs de référence V1 et V2. Lorsque le signal de sortie du détecteur D2 est compris entre ces deux valeurs, le dispositif de comparaison C2 délivre un signal correspondant par exemple au signal logique "1". De même, lorsque le signal de sortie du détecteur D2 est hors de cette fenêtre de valeurs, alors le dispositif de comparaison C2 délivre un signal correspondant à l'état logique inverse de l'état précédent soit "0" dans l'exemple. Ce test est effectué pour une période limitée T. Le diagramme des temps pour ces différents signaux est représenté sur la figure 3. Les signaux présents sur les connexions 35 et 36 de la figure 2 sont représentés sur la figure 3 respectivement sous le repère 1 et sous les repères 2 et 3 selon qu'une action de masquage n'a pas ou a été détectée. Le signal 1 indique que pendant une durée limitée T l'émetteur E2 fonctionne. Sur la connexion 36 s'il n'y a pas eu de masquage apparaît le signal 2 de la figure 3, c'est-à-dire que le signal 1 a été émis par C2. Si au contraire sur la connexion 36 apparaît le signal 3 de la figure 3 il s'agit d'une absence de détection, c'est-à-dire d'une panne de E2 ou de D2, ou du fait qu'une action de masquage a été détectée. Dans ce dernier cas la sortie de la bascule 37 met en action l'alarme de la centrale d'alarme 40 à l'aide de l'élément de validation 38. Lorsqu'aucun masquage n'a été détecté la bascule 37 met en fonctionnement l'émetteur E1 41 qui fournit un rayonnement infrarouge λ1 détecté par le détecteur D1 42. Le signal de sortie de celui-ci arrive à l'élément de validation 38. Si un signal n'a pas été détecté par le détecteur D1 42, l'élément de validation déclenche l'alarme de la centrale d'alarme. Si au contraire un signal a été détecté l'élément de validation 38 valide la fin de la période de durée limitée T ce qui a pour effet de redonner à la centrale d'alarme son autonomie pour intervenir en cas de détection d'un rayonnement à longueur d'onde λ1 par le détecteur D1. Le dispositif de détection d'intrus est alors dans son état de fonctionnement permanent pour déceler un intrus.In Figure 2, an electrical block diagram of the intruder detection device is shown. A generator 30 of an electrical signal of duration T actuates the emitter E2 12, the emitted radiation of which is detected by the detector D2 13. The latter is connected at the output to a comparison device C2 32. The comparison device C2 32 receives the output signal from detector D2 and compares it to two reference values V1 and V2. When the output signal of the detector D2 is between these two values, the comparison device C2 delivers a signal corresponding for example to the logic signal "1". Likewise, when the output signal of the detector D2 is outside this window of values, then the comparison device C2 delivers a signal corresponding to the reverse logic state of the previous state, ie "0" in the example. This test is carried out for a limited period T. The time diagram for these different signals is represented in FIG. 3. The signals present on the connections 35 and 36 of FIG. 2 are represented in FIG. 3 respectively under the reference 1 and under marks 2 and 3 depending on whether a masking action has not been or has been detected. Signal 1 indicates that for a limited time T the transmitter E2 is operating. On the connection 36, if there has been no masking, the signal 2 of FIG. 3 appears, that is to say that the signal 1 was emitted by C2. If on the contrary on the connection 36 appears the signal 3 of FIG. 3 it is a lack of detection, that is to say a failure of E2 or D2, or of the fact that an action masking has been detected. In the latter case, the output of flip-flop 37 activates the alarm of the central alarm 40 using the validation element 38. When no masking has been detected flip-flop 37 activates the emitter E1 41 which supplies infrared radiation λ 1 detected by the detector D1 42. The output signal from the latter arrives at the validation element 38. If a signal has not been detected by the detector D1 42 , the validation element triggers the alarm of the alarm center. If on the contrary a signal has been detected the validation element 38 validates the end of the period of limited duration T which has the effect of giving back to the alarm center has autonomy to intervene in the event of detection of radiation at wavelength λ 1 by the detector D1. The intruder detection device is then in its permanent operating state to detect an intruder.

La procédure qui vient d'être décrite est effectuée à chaque remise en route du dispositif. Il est possible de répéter cette procédure séquentielle- ment afin d'effectuer les opérations d'autovérifica- tion qui se déroulent selon une procédure semblable mettant en évidence une panne dont l'apparition ne peut être détectée par le détecteur D1.The procedure which has just been described is carried out each time the device is restarted. It is possible to repeat this procedure sequentially in order to carry out the self-checking operations which take place according to a similar procedure highlighting a fault whose appearance cannot be detected by the detector D1.

La figure 4 représente une seconde variante du dispositif de détection d'intrus. Il diffère de la précédente par le miroir dichroïque 50 placé derrière la fenêtre d'entrée 11. Le faisceau lumineux réfléchi 22 issu de l'émetteur E2 12 est réfléchi par le miroir dichroïque 50 selon le faisceau 51 qui arrive sur le détecteur D2 13 dont la face d'entrée a été dirigée en direction du faisceau 51. Par contre, le faisceau 23 issu de l'intrus traverse le miroir dichroïque 50 pour venir sur le détecteur D1 15 après avoir été réfléchi par le miroir à facettes 16. Les deux faisceaux sont donc dissociés en fonction de leur longueur d'onde. Les faisceaux 22 et 23 traversant sensiblement la même partie de la fenêtre d'entrée 11 tout masquage de la fenêtre se répercutera sur les deux faisceaux. Dans ce cas un émetteur E3 52 est disposé à l'intérieur du boîtier et assure seulement une fonction d'autovérification. Le fonctionnement électrique reste le même.FIG. 4 represents a second variant of the intruder detection device. It differs from the previous one by the dichroic mirror 50 placed behind the entry window 11. The reflected light beam 22 coming from the emitter E2 12 is reflected by the dichroic mirror 50 according to the beam 51 which arrives at the detector D2 13 of which the entry face has been directed towards the beam 51. On the other hand, the beam 23 coming from the intruder crosses the dichroic mirror 50 to come to the detector D1 15 after having been reflected by the faceted mirror 16. The two beams are therefore dissociated according to their wavelength. The beams 22 and 23 passing through substantially the same part of the input window 11 any masking of the window will affect the two beams. In this case an E3 52 transmitter is placed inside the housing and only performs a self-checking function. The electrical operation remains the same.

Selon des dispositions connues de l'homme de l'art le miroir à facettes qui segmente la scrutation de la zone mise sous surveillance peut être remplacé par une lentille de Fresnel. Dans ce cas la lentille de Fresnel est disposée, après le filtre passe-haut 17, sensiblement perpendiculairement au faisceau 23, le détecteur D1 15 faisant alors face à la direction d'arrivée du faisceau 23.According to arrangements known to those skilled in the art, the faceted mirror which segments the scanning of the area under surveillance can be replaced by a Fresnel lens. In this case, the Fresnel lens is arranged, after the high-pass filter 17, substantially perpendicular to the beam 23, the detector D1 15 then facing the direction of arrival of the beam 23.

Claims (14)

1. An apparatus for detecting intruders comprising in a housing (10) provided with at least one window (11) a passive infrared detector D1 (15) detecting the radiation emitted by an intruder around a wavelength λ: and an anti-obscuring means detecting by means of an infrared radiation having a wavelength λ2 the presence of an obscuring of the apparatus for detecting intruders, as well as electronic means intended to operate an alarm when the presence of an intruder or of an obscuring has been detected, characterized in that the apparatus for detecting intruders comprises:
- means for detection of an obscuring situated at a small and at a large distance, this obscuring modifying the intensity of the luminous fluxes traversing the window;
- and self-verification means.
2. An apparatus for detecting intruders as claimed in Claim 1, characterized in that the means for detection of an obscuring comprise an emitter E2 (12) and a detector D2 (13) operating at the wavelength X2 and at least one reflector, the at least one reflector (20) being situated at an end of the zone to be supervised and reflecting the light emitting by the emitter E2 to the detector D2.
3. An apparatus for detecting intruders as claimed in Claim 2, characterized in that the means for detection of an obscuring comprise:
- a generator (30) supplying an electric signal of a duration T causing the emitter E2 (12) to become operative;
- and a comparison device C2 (32) arranged at the output of the detector D2 (13), the comparison device C2 comparing the value of the signal emitted by the detector D2 with two reference values constituting an electronic window.
4. An apparatus for detecting intruders as claimed in Claim 3, characterized in that the comparison device C2 (32) is combined with a storage element (37) acting upon a validation element (38) of an alarm station (40) when the signal emitted by the detector D2 (13) is outside the electronic window.
5. An apparatus for detecting intruders as claimed in any one of Claims 1 to 3, characterized in that the means for detection of an obscuring comprise a light emitter E1 (18) operating in the proximity of the wavelength λ1 situated very close to and in front of the window (11) outside the housing (10).
6. An apparatus for detecting intruders as claimed in Claim 5, characterized in that the comparison device C2 (32) is combined with a storage element (37) connected to the emitter E1 (18) which is made operative when the signal emitted by the detector D2 (12) is inside the electronic window, the detector D1 (15) being connected to the validation element of the alarm station (40).
7. An apparatus for detecting intruders as claimed in Claims 1 or 6, characterized in that the setf-verification means are constituted by the means for detection of an obscuring.
8. An apparatus for detecting intruders as claimed in Claim 4, characterized in that besides the at least one reflector (20) arranged at the end of the zone to be supervised there is present a dichroic mirror (50) which returns the light beam having the wavelength X2 reflected by the reflector (20) arranged at the end of the zone to be supervised to the detector D2 (13) and transmits the light having the wavelength λ1 to the detector D1 (15).
9. An apparatus for detecting intruders as claimed in Claim 4, characterized in that besides the at least one reflector (20) arranged at the end of the zone to be supervised, there is present a dichroic mirror (50) which transmits the light beam having the wavelength X2 reflected by the reflector (20) arranged at the end of the zone to be supervised to the detector D2 (13) and returns the light having the wavelength λ1 to the detector D1 (15).
10. An apparatus for detecting intruders as claimed in Claims 8 or 9, characterized in that the dichroic mirror (50) is arranged very close to the detector D1 (15).
11. An apparatus for detecting intruders as claimed in Claim 10, characterized in that the self-verification means comprise an emitter E3 (52) having a radiation in the proximity of the wavelength λ: situated inside the housing (10) close to the detector D1 (15).
12. An apparatus for detecting intruders as claimed in Claim 11, characterized in that the comparison element C2 (32) is combined with the storage element (37), which activates the emitter E3 (52), which is made operative when the signal emitted by the detector D2 (13) is inside the electronic window, the detector D1 (15) being connected to the validation element (38) of the alarm station (40).
13. An apparatus for detecting intruders as claimed in any one of Claims 2 to 12, characterized in that the reflectors (20) exclusive of the dichroic mirror (50) are disposed at distinct areas arranged at the ends of the zone to be supervised.
14. An apparatus for detecting intruders as claimed in any one of Claims 1 to 13, characterized in that the window(s) (11) constitute(s) a filter which stops the visible wavelengths and transmits the wavelengths λ2 and those in the proximity of λ1.
EP85201873A 1984-11-30 1985-11-14 Intrusion detection system with an anti-masking device Expired - Lifetime EP0186226B1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR8418288 1984-11-30
FR8418288A FR2574200B1 (en) 1984-11-30 1984-11-30 DEVICE FOR DETECTING AN INTRUDER PROVIDED WITH AN ANTI-MASKING DEVICE

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EP0186226A1 EP0186226A1 (en) 1986-07-02
EP0186226B1 true EP0186226B1 (en) 1990-02-28

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US (1) US4752768A (en)
EP (1) EP0186226B1 (en)
JP (1) JPS61131198A (en)
DE (1) DE3576231D1 (en)
FR (1) FR2574200B1 (en)

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Also Published As

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FR2574200B1 (en) 1987-01-23
DE3576231D1 (en) 1990-04-05
US4752768A (en) 1988-06-21
FR2574200A1 (en) 1986-06-06
JPS61131198A (en) 1986-06-18
EP0186226A1 (en) 1986-07-02

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