EP0476397B2 - Intrusion detector - Google Patents

Abstract

In a combined infrared/ultrasonic intrusion detector, which simultaneously detects the body radiation and the movement of an intruder in order to raise the alarm, an attempt to render the infrared part of the detector ineffective by mounting a radiation screen in front of the radiation entry window (9) is detected by providing to the side of the window (9) an ultrasonic emitter (10) and an ultrasonic receiver (11), by means of which an ultrasound field is built up in front of the window (9). An interference signal is triggered in the event of a change in sound pressure or sound propagation time. This also makes it possible to recognise screens which are transparent to other radiations, for example light or microwaves, and cannot be detected therewith. In order to prevent the mounting of a screen such as a foil or spray layer directly on the window (9), the window (9) is mounted in a recess (8) on the front side (7) of the housing (1) and covered approximately in the plane of the front side (7) with a cover (14) which has very fine openings and is transparent both to ultrasound and to infrared radiation. An ultrasonic component (10) is located inside the recess (8), while another ultrasonic component (11) is located outside thereof, so that the cover (14) is transirradiated by ultrasound and it is possible to recognise a change in the permeability of the cover (14). <IMAGE>

Description

The invention relates to an intrusion detector according to the preamble of patent claim 1.

Such intrusion detectors are known for example from DE-A-22'16'236. They consist of one Combination of a passive infrared detector and an ultrasound detector, which are combined in an AND circuit are connected. The infrared part reacts to the body radiation of a person in the infrared Spectral range and the ultrasound part on the frequency shift caused by the Doppler effect of ultrasound reflected from a moving intruder. By combining both principles prevents an unwanted intrusion of a person into a protected area with greater security and detect selectivity as using only a single detection method. A faulty one In this way, alarm signaling can be avoided with greater certainty.

Passive infrared intrusion detectors are known for example from EP-A1-0'189'536. You serve an object that has entered a monitored area, e.g. an intruder, by means of this Detect emitted infrared radiation and trigger an alarm signal via an evaluation circuit. Here, through a number of reflector or mirror segments, via which the incoming radiation to Sensor is guided, a corresponding number of spatially distributed sensitivity areas is formed, when they are penetrated by an intruder, a change in radiation of the sensor and thus a Alarm signal is generated. The sensor can have a single sensor element, or it can be a Multiple or dual sensors can be designed with two or more separate sensor elements or flakes, whereby the number of sensitivity ranges is at least doubled.

To protect the sensor and the optical reflectors from damage and dust, as well as Camouflage of the detector, the housing of the detector is closed in the direction of irradiation by a window, that for the infrared radiation to be detected, e.g. for the body radiation of a person in the area from about 5 to 15 µm, preferably between 7 to 12 µm, permeable, but for shorter-wave radiation is largely impermeable. This window can in turn be optically bundled, e.g. as a Fresnel lens, which generates the desired sensitivity ranges, so that, if necessary, on mirror segments can be dispensed with.

On the other hand, ultrasonic intrusion detectors, e.g. from CH-A-556'070 or EP-A1-0'158'022, known. These have an ultrasound emitter that emits ultrasound at a frequency of over 20 kHz monitored area in front of the detector, as well as an ultrasound receiver, which from the room records reflected ultrasound and feeds it to an evaluation circuit. While fixed objects only ultrasound reflect with the transmit frequency, a moving intruder causes a frequency shift after the Doppler effect. The evaluation circuit triggers an alarm signal when this frequency shift corresponds to values that are typical of a moving person and if so at the same time an infrared radiation is received, which is characteristic of human intruders.

It is in the nature of things that intruders often try such intrusion detectors to make it inoperable. It would suffice to render only one of the two detection parts ineffective, because they are connected by an AND circuit. For decommissioning the ultrasonic part however, the entire detector would have to be covered, which would be immediately visible. Therefore, the Outsmarting the intrusion detector mostly by attaching a radiation shield in front of the detector or tried on the window itself, which keeps the incident radiation away from the sensor. It's relatively easy to make such interventions almost invisible, since most of the transparent materials in the visible spectral range, such as glass, household foils, hair lacquer spray, transparent protective lacquers etc., long-wave infrared radiation absorb. For intrusion and intrusion protection systems for objects with high risks, it is therefore desirable Such attempts to outsmart the individual detectors to determine and signal.

From EP-A1-0'189'536 or from GB-A-2'141'228 it is known that the window is transparent to infrared radiation through an infrared radiation source attached to the outside of the housing, which passes through the window radiates on the sensor to monitor. If this radiation is absent or reduced, a Fault signals. In this way, however, only a radiopaque one lying directly on the window can Layer can be detected, but no objects just in front of the detector or at a certain distance of this.

This disadvantage, e.g. shown in US-A-4,752,768 by using a reflex light barrier can be eliminated with a reflector arranged remotely from the detector, with which the intermediate space between Detector and reflector on the application of radiation shields is monitored. The disadvantage is here that the reflector and detector must be precisely adjusted to one another, which complicates the system, is expensive, difficult to install and susceptible to faults In addition, only one field of vision can be used with an additional reflector be monitored. In addition, in such known systems, there are various reasons for shorter waves Radiation is used so that only objects can be recognized that are also in the short-wave infrared absorb at about 0.9 µm radiation.

Another, e.g. infrared intrusion detector known from EP-A2-0'274'889 is an infrared sensor combined with a microwave system in a logic circuit that only triggers an alarm signal, when both systems emit a signal at the same time. Here is the infrared sensor between the microwave transmitter and receivers arranged immediately adjacent to them behind the entrance window. One try, to cover the window or to provide it with a spray layer or to install a shield in front of the window, can be detected by the microwave part. However, this can only be used to identify objects reflect or absorb the microwaves, i.e. preferably metallic conductive materials, but straight not many films that are opaque to infrared radiation and often used for sabotage attempts or paints.

The object of the invention is to overcome the above-mentioned disadvantages of the prior art eliminate and in particular to create a combined intrusion detector of the type specified at the outset, an attempt to sabotage or reduce functionality by using a shield Can detect and signal with greater security and with less effort.

This object is achieved by those specified in the characterizing part of patent claim 1 Features resolved. Preferred embodiments of the invention and configurations are in the dependent claims defined.

Such a temporal change in the ultrasound field exists e.g. in a change in sound pressure or the duration of the ultrasound reflected by objects in the monitored room. As soon as such a measurand changed compared to an earlier point in time or to an average from previous measurements is an indication that a change has been made in the room, e.g. a shield in the room was placed. Such a temporal parameter change of the sound field can easily be done by the Doppler frequency evaluation processed separately.

Here the analogy of far infrared in the frequency domain, which has apparently not been recognized or taken into account so far human body radiation and ultrasound that is close to the listening area exploited their spread, especially the fact that this ultrasound is almost in air spreads unhindered, but is reflected or absorbed by practically all solid surfaces. Consequently shields that absorb radiation in the far infrared can also be identified by means of ultrasound, which are however permeable to microwaves or light and to radiation in the neighboring infrared.

Ultrasonic emitters and receivers are preferably arranged on different sides of the entrance window, so that the ultrasonic field covers the window area. Instead, it can be beneficial Ultrasound emitter and receiver to be placed adjacent to the same side of the window and the ultrasound by means of reflectors, which are arranged on one or different sides of the window, over the window to lead.

The exit surface of the ultrasonic emitter and the entry surface of the ultrasonic receiver are particularly advantageous on both sides of a plane formed by the front wall of the housing at the location of the window arranged so that at least one acoustically effective surface of the ultrasonic components, e.g. Emitter, Receiver or a reflector lies within the recess. It is of particular advantage, for example in the Level the front wall in front of the window with fine openings, at least for the most part cover that is permeable to infrared radiation and ultrasound, e.g. a fine-mesh grid or a perforated one Foil to be provided and arranged in such a way that the front surfaces of the ultrasound emitter and receiver lie on different sides of the cover and thus the cover from the ultrasound generated is irradiated. This will result in an attempt at impermeability, e.g. by spraying, supervised

Since the intrusion detector according to the invention has both an infrared part and an ultrasound part anyway it can advantageously be carried out without a significantly increased effort by means of a temporal ultrasound field evaluation, as well as an infrared window monitoring device known in principle, which optimizes security against sabotage and reduces the susceptibility to false alarms.

Figur 1

einen erfindungsgemäßen Intrusionsdetektor im Vertikalschnitt entlang der Symmetrieebene S-S (Figur 2),

Figur 2

einen erfindunasqemäßen Intrusionsdetektor in Frontansicht,

Figur 3a

einen Horizontalschnitt entlang der Ebene A-A.

Figur 3b

einen Diagonalschnitt entlang der Ebene B-B und

Figur 4

einen weiteren Intrusionsdetektor in Frontansicht.

The invention is explained in more detail on the basis of the exemplary embodiments shown in the figures. Show it:

Figure 1

an intrusion detector according to the invention in vertical section along the plane of symmetry SS (Figure 2),

Figure 2

a front view of an intrusion detector according to the invention,

Figure 3a

a horizontal section along the plane AA.

Figure 3b

a diagonal section along the plane BB and

Figure 4

another intrusion detector in front view.

The infrared intrusion detector shown in Figure 1 has a housing 1, preferably made of plastic, on. Inside the housing 1 there is infrared radiation in the evaluated spectral range from 5 to 15 μm, in particular from 7 to 12 µm, highly reflective, preferably made of metal, mirror or reflector 2 arranged, for example, as described in EP-A1-0'189'536 or in another suitable manner can be designed as a segment mirror to cover a number of spatial sensitivity ranges form. The part 3 adjoining the mirror segments is used to shield electromagnetic fields from the circuit board 4 arranged in front with the components of the evaluation circuit mounted thereon. This is set up so that one moves an intruder through a range of sensitivity generated radiation change of the sensor, i.e. with a predetermined change in the infrared radiation striking the sensor, triggers an output signal. On the lower part of the board 4 is the infrared sensor 5 is attached, which is designed, for example, as a pyroelectric sensor and at least in the spectral range is sensitive to human body radiation This sensor 5 can be a single radiation-sensitive Have element or as a multiple or dual sensor with at least two neighboring Sensor elements are designed. In front of the circuit board 4 there is another electromagnetic one Shield 6, e.g. from a suitable metal sheet.

On the front wall of the housing 1, an entry window 9 is provided in a recess 8 through which infrared radiation incident on the detector and pass through the reflector 2 onto the sensor 5 can reach. In order to keep interference radiation of other wavelengths away from the sensor 5, the window 9 is off made of a material that is preferably for human body radiation, i.e. in the wavelength range of 5 to 15 µm, especially 7 to 12 µm, is permeable, e.g. from a suitable plastic such as polyethylene, Special glass or silicon. The window also protects the inside of the detector, especially the optical one Reflectors 2 and the sensor 5 from damage and dust. The window can also be used as an optical effective element, e.g. as a Fresnel lens in order to concentrate and generate radiation from separate sensitivity areas.

To prevent the detector from becoming ineffective in that a radiation-absorbing Shield is attached, which incoming infrared radiation from the entrance window 9 keeps away, the detector is equipped with a device for detecting and signaling such a function-reducing Shield equipped

As shown in FIG. 2, this consists of one provided on one side of the radiation entrance window 9 Ultrasound emitter 10 and an ultrasound receiver lying on the opposite side of the window 9 11. The emitter 10 sends ultrasound in the frequency range slightly above the hearing range off, for example in the frequency range around 25 kHz. Immediately in front of window 9 and throughout: room area An ultrasound field US1 is thus formed in front of the detector, which is present during the attachment a sound-shielding wall in front of the detector changes The receiver 11 is connected to a suitable one Evaluation circuit connected, which triggers a fault signal when the one registered by the receiver 11 Ultrasound changes in a predetermined manner, as is the case for applying a shield in front of the detector is characteristic. In particular, the intensity of the received ultrasound and its time course with the measurement results obtained at an earlier point in time or formed from previous measurements Averages were compared and deviations identified for changes in the monitored room are typical of the detector.

Since an ultrasonic field in the frequency range mentioned practically from all fixed interfaces, i.e. all Surfaces are affected, but spreads almost unhindered in air, are in this way Ultrasound also detects and reports shielding materials that absorb radiation in the far infrared, however, are practically transparent to light and microwaves, which was previously the case with infrared intrusion detectors with tamper protection devices working on infrared or microwave basis was not possible.

Since the intrusion detector contains an ultrasound device anyway, this can be surprising Advantages and without special additional effort for function monitoring of the infrared part of the intrusion detector be used. It is only necessary to do this on the front side 7 of the housing, as in Figure 2 and 3a shown to arrange the ultrasonic emitter 10, 12 so that the in the room in front of the detector emitted ultrasound forms an ultrasound field in front of the infrared window 9. The evaluation circuit is then trained so that it triggers an alarm signal when the ultrasound reflected from a moving object a predetermined frequency shift corresponding to the moving speed of the object shows and at the same time the infrared part emits an output signal and a fault signal when the received Ultrasound shows a certain change compared to earlier times The required for this Circuit can be integrated easily and without great effort into the existing evaluation circuit.

The described device is capable of providing an infrared shield in front of the detector in one determine large distance range with great certainty, a shield applied directly to the window 9 cannot be grasped easily. To make such an attempt at sabotage more difficult, is the entrance window 9 in a recess 8 of the housing front wall 7, which is the attachment of a suitable shielding film hindered. The window could still be reached with a spray. To protect against such an attempt, it is advantageous, for example in the plane of the front wall 7 of the housing 1 in front of the window 9 to provide a cover 14 provided with fine openings, which at least is largely transparent to ultrasound and infrared radiation. This can e.g. around a fine mesh Act as it is used to protect screens or as an insect screen, or a film with fine holes, e.g. made of polyethylene. The openings should be one size have at most in the range of tenths of a millimeter, so that they are closed by spraying and this makes the cover impermeable. If now, as shown in Figure 3b, the sound exit surface of the Ultrasonic emitter 10 is mounted inside the recess 8 behind the cover 14, the surface of the receiver 11, however, on the front 7 outside the cover 14, the ultrasound normally penetrates the cover 14 through the openings. However, it is sprayed on when the openings are closed Paint blocked so that a sabotage attempt is recognized and reported here too.

To achieve even greater security, as can be seen in FIG. 2, the shoulder of the recess can be used 8 an infrared radiation source 15 can be provided, which through the window 9 through an optical Reflector 16 irradiates the sensor 5. If this radiation is absent or reduced, in itself generates a disturbance signal in a known manner.

Different variants of the described exemplary embodiments are possible without the scope of the inventive concept to leave. Two ultrasound emitters and receivers can be provided However, as shown in FIG. 4, there can also be only a single ultrasound emitter 17 and a receiver 18 be attached to the same side of the window 9. The ultrasound is here from the emitter 17 via one or several acoustic reflectors 19, e.g. Sheet metal strips, fed through the window 9 to the receiver 9.

It is advantageous to switch the ultrasound receiver 11, 18 so that it alternates in normal operation during certain room surveillance phases, such as several seconds, the occurrence of frequencies shifted according to the Doppler effect, in between during the periodic control phases however, testing takes a few tenths of a second using short ultrasonic pulses or modulations the ultrasonic transmitter 10, 12, 17 takes place, with distinctive sound field changes compared to previous ones Control phases can be seen as signs of an attempt at sabotage.

It is even possible to use only a single ultrasonic emitter / receiver element. The element periodically alternately emits short control pulses and immediately returns to normal reception mode rearranged On the opposite side of the window acoustic reflectors ensure that in the undisturbed case, a well-known echo pulse returns to the receiver, but this occurs with everyone Change due to changed reflections in the space in front of the detector in its amplitude and in time History changes.

Claims (9)

1. Intrusion detector with a sensor (5) which is sensitive to infrared radiation and on which radiation from at least one spatial sensitivity area impinges, with at least one ultrasonic emitter (10, 12, 17) and at least one ultrasonic receiver (11, 18) and also with an evaluation circuit (4) for alarm signalling in the event of a simultaneous predetermined change in the infrared radiation impinging on the sensor (5) and a predetermined change in the ultrasound received by the ultrasonic receiver (11, 18), characterised in that the detector has a housing (1) with an entry window (9) which is fitted in a depression (8) of the housing (1), in that ultrasonic emitter (10, 12, 17) and ultrasonic receiver (11, 18) are arranged at the side of the window in such a way that an ultrasonic field is formed in front of the window, in that the evaluation circuit (4) is designed in such a way that, in the event of a predetermined temporal change in the ultrasonic field, it triggers a fault signal which indicates a sabotage attempt at the entry window (9), and in that in front of the window (9) there is provided approximately in the plane of the front wall (7) a covering which is provided with fine openings and is at least for the most part transparent to ultrasound and infrared radiation and which is passed by the ultrasound field.
2. Intrusion detector according to claim 1, characterised in that the ultrasonic emitter (10) and the ultrasonic receiver (11) are arranged on opposite sides of the window (9).
3. Intrusion detector according to claim 1, characterised in that the ultrasonic emitter (17) and the ultrasonic receiver (18) are arranged on the same side of the window (9) and in that at least one acoustic reflector (19) is provided on the other side of the window (9), in order to direct the ultrasound from the ultrasonic emitter (17) to the ultrasonic receiver.
4. Intrusion detector according to claim 3, characterised in that the ultrasonic receiver (18) serves at the same time as ultrasonic emitter and is periodically switched alternately as ultrasonic emitter and as ultrasonic receiver.
5. Intrusion detector according to one of claims 1 to 3, characterised in that at least one of the ultrasonic components comprising emitter (10, 12, 17), receiver (11, 18) and reflector (19) lies with its acoustically effective area within the depression (8) behind the plane formed by the front wall (7), and at least another ultrasonic component lies with its acoustically effective area outside the depression (8).
6. Intrusion detector according to claim 1, characterised in that the size of the openings of the covering (14) lies at most in the range of tenths of a millimetre.
7. Intrusion detector according to one of claims 1 to 6, characterised in that the evaluation circuit (4) to which the ultrasonic emitter (10, 12, 17) and the ultrasonic receiver (11, 17) are connected, triggers a fault signal in the event of a predetermined change in the sound pressure and/or in the event of a predetermined change in the echo time of the ultrasound in comparison with an earlier point in time.
8. Intrusion detector according to one of claims 1 to 7, characterised in that the evaluation circuit (4) is set up periodically to evaluate for signalling alternately a frequency shift of the received reflected ultrasound and a temporal change in the amplitude and/or the variation over time of the received reflected ultrasound.
9. Intrusion detector according to one of claims 1 to 8, characterised in that in front of the entry window (9) there is provided an infrared radiation source (15) which radiates through the window (9) onto the infrared sensor (15).

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