EP0711442A1 - Active ir intrusion detector - Google Patents

Active ir intrusion detector

Info

Publication number
EP0711442A1
EP0711442A1 EP95917879A EP95917879A EP0711442A1 EP 0711442 A1 EP0711442 A1 EP 0711442A1 EP 95917879 A EP95917879 A EP 95917879A EP 95917879 A EP95917879 A EP 95917879A EP 0711442 A1 EP0711442 A1 EP 0711442A1
Authority
EP
European Patent Office
Prior art keywords
signal
detector according
infrared detector
infrared
controller
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
EP95917879A
Other languages
German (de)
French (fr)
Other versions
EP0711442B1 (en
Inventor
Peter Kunz
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Siemens Building Technologies AG
Original Assignee
Cerberus AG
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Cerberus AG filed Critical Cerberus AG
Priority to EP95917879A priority Critical patent/EP0711442B1/en
Publication of EP0711442A1 publication Critical patent/EP0711442A1/en
Application granted granted Critical
Publication of EP0711442B1 publication Critical patent/EP0711442B1/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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Classifications

    • G—PHYSICS
    • G08—SIGNALLING
    • G08B—SIGNALLING OR CALLING SYSTEMS; ORDER TELEGRAPHS; ALARM SYSTEMS
    • G08B29/00—Checking or monitoring of signalling or alarm systems; Prevention or correction of operating errors, e.g. preventing unauthorised operation
    • G08B29/18—Prevention or correction of operating errors
    • G08B29/183—Single detectors using dual technologies
    • 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
    • G08B13/181—Actuation by interference with heat, light, or radiation of shorter wavelength; Actuation by intruding sources of heat, light, or radiation of shorter wavelength using active radiation detection systems
    • G08B13/187—Actuation by interference with heat, light, or radiation of shorter wavelength; Actuation by intruding sources of heat, light, or radiation of shorter wavelength using active radiation detection systems by interference of a radiation field

Definitions

  • the present invention is in the field of infrared detectors, which are detectors that monitor a room for unauthorized entry and for this purpose evaluate infrared radiation received by the detector.
  • infrared detectors There are two types of such infrared detectors, the passive and the active.
  • the detector waits until a radiation source that emits radiation that differs from the surroundings, that is to say has a different temperature than its surroundings, penetrates into the visual field.
  • the passive infrared detectors which are relatively inexpensive and widely used today, can in principle only detect radiating objects and reach a limit as soon as objects, for example valuables, are to be monitored that can be removed by mechanical, non-detectable means.
  • special measures against so-called masking that is the unnoticed changing or covering of the detector's field of view, must be taken with passive infrared detectors.
  • the active infrared detectors do not process the thermal radiation emitted by objects in the visual field, but rather actively irradiate the space to be monitored and react to changes in the reflected infrared radiation. As a result, they can also detect movements of "dead", ie non-radiating objects. In addition, they are very difficult to mask because they notice any approach. For this, the active infrared detectors have certain difficulties in terms of sensitivity and false alarm security because the reflected infrared radiation can be overlaid by such strong interference that a reliable detection of movements is almost impossible.
  • the invention relates to an active infrared detector for the detection of movements in a surveillance room, with a transmitter for transmitting modulated infrared radiation into the surveillance room, with a receiver for the infrared radiation reflected from the surveillance room, and with one connected to the receiver and means for obtaining an evaluation circuit containing a useful signal.
  • the evaluation circuit contains an operational amplifier designed as a synchronous amplifier, from. which only those receive signals that are in phase with the transmitted signal are amplified. These signals are integrated in two integrators with different time constants, both integrators generating the same voltage in the undisturbed state, and a difference between these voltages indicates an intruder.
  • This infrared detector cannot be satisfactory in terms of responsiveness, because the integration of the received signal with two different time constants does not offer a sufficient guarantee that every object movement in the surveillance space is actually recognized.
  • the detector is also not false alarm-proof, because it cannot be ruled out that a difference between the signals of the integrators is caused by causes other than an object movement.
  • the invention is now intended to improve this known active infrared detector with regard to sensitivity, reliability and insensitivity to external influences.
  • the active infrared detector according to the invention for solving the problem is characterized in that the evaluation circuit has a controller which is acted upon on the one hand with the useful signal and on the other hand connected to the output of the receiver for emitting a compensation signal which is superimposed on the receiver signal, and that the compensation signal is selected such that that the useful signal is adjusted to the value zero.
  • the adjustment of the useful signal to the value zero has the advantage that the maximum sensitivity is always retained; the receiver acts like a self-balancing scale. This immediately results in an undesired interference signal, provided that it has the same frequency and phase as the emitted infrared radiation, is compensated for to zero and does not lead to a throttling of the receiver to minimal sensitivity. Interference signals from other frequencies are not so critical because they can be easily filtered out.
  • a first preferred embodiment of the infrared detector according to the invention is characterized in that common optics are provided for the transmitter and receiver.
  • the use of a common optic enables a massive reduction in manufacturing costs and dimensions, as well as the achievement of a maximum range with low power consumption.
  • a second preferred embodiment of the infrared detector according to the invention is characterized in that the evaluation circuit has an analog / digital converter connected downstream of the controller, at one output of which the digitized controller signal is available and the other output with a digital / analog converter for generation a voltage corresponding to the respective digital signal value is connected, and that this voltage is used to generate the compensation signal.
  • the digitization of the controller signal has the advantage that a signal evaluation that is more differentiated and intelligent than before is possible.
  • the one output of the analog / digital converter is connected to a microprocessor.
  • the microprocessor enables an increase in the resolution and, on the other hand, it creates the prerequisite for copying the sensor present in the infrared detector with a second to couple another sensor principle and to evaluate the signals of both sensors together.
  • Fig. 1 is a schematic sectional view of an infrared detector according to the invention
  • Fig. 2 is a block diagram of a first embodiment of the evaluation circuit of the
  • FIG. 4 shows a block diagram of a second exemplary embodiment of the evaluation circuit of the
  • the active infrared motion detector 1 shown in FIG. 1 essentially consists of a transmitter S which irradiates the room to be monitored with pulsating infrared light, a receiver E for the infrared radiation reflected from the monitoring room, and evaluation and control electronics 2 and from a power supply 3.
  • the transmitter S is formed by an infrared light-emitting diode (IRED) 4 and the receiver E by a photodiode 5.
  • Transmitter S, receiver E, electronics 2 and power supply 3 are arranged in a common housing 6, which is mounted in a suitable location in the room to be monitored, for example on a wall or on the ceiling.
  • the power supply 3 is connected to an external supply and contains a fixed voltage regulator (not shown).
  • the housing 6 contains an infrared-transmissive window 7 in the area of the transmitter S and the receiver E.
  • suitable optics 8 are provided, which of course do not have to be arranged between the window 7 on the one hand and the transmitter and receiver S or E on the other hand, but can also be integrated into the window 7.
  • the optics 8 can be a lens or a mirror optics. It is essential that common optics are provided for transmitter S and receiver E. In other words, this means that the receiver E "sees" exactly those areas of the monitoring room that the transmitter S is currently applying infrared radiation to. And this enables a multiple range with the same power consumption or a massively reduced power consumption with the same range.
  • a shield 9 is arranged between the transmitter S and the receiver E to prevent a direct light connection between these two elements.
  • the electronics 2 has an alarm output 10 for the alarm signals obtained during the signal evaluation. These can activate an internal and / or an external alarm display built into the respective detector 1.
  • a first modulator 11 is connected upstream of the infrared light-emitting diode 4, through which a suitable modulation of the radiation emitted by the infrared light-emitting diode 4 takes place.
  • This radiation preferably consists of a continuous sequence of pulses and pulse pauses, so that the room to be monitored is irradiated with pulsating infrared light. It can also make sense to insert a longer, predetermined transmission pause after a sequence of a certain number of pulses and pulse pauses. In this case, the monitoring room is irradiated by pulse trains or pulse packets which are emitted intermittently and are interrupted by pauses in transmission.
  • the transmission pauses to the pulse trains can be in a fixed or in a variable time ratio.
  • the first modulator 11 is controlled by a control stage 12, which receives its clock from a clock generator 13.
  • the control stage 12 determines in particular the time sequence and the length of the signals emitted to the infrared light-emitting diode 4.
  • the infrared radiation emitted by the infrared light-emitting diode 4 is bundled by the optics 8 (FIG. 1) and directed into a defined area of the monitoring room.
  • the infrared radiation reflected from this area is collected by the optics 8 and thrown onto the light-sensitive diode 5.
  • the received infrared radiation is converted by the diode 5 into a proportional current (receiver signal) I e , which a the current / voltage converter 14 connected downstream of the diode 5 and converted into a voltage (received signal) U e by the latter.
  • the transducer 14 also acts as a type of filter for uniform light by suppressing light from the sun and room lighting.
  • a frequency filter 15 connected downstream of the current / voltage converter 14, undesired frequencies are filtered out from the received signal U e , as a result of which interference caused by incandescent, fluorescent and discharge lamps is suppressed.
  • the output of the frequency filter 15 is connected to a switch 16 controlled by the control stage 12 in time with the modulation of the infrared light-emitting diode 4.
  • the output signal of the frequency filter 15, which is largely free of interference, is alternately fed to one of two integrators 17, 17 'via the switch 16.
  • the switch 16 is controlled by the control stage 12 in such a way that the received signal U e is sent to one integrator, for example to the integrator 17, during the duration of the pulse transmission and to the other integrator, for example to the integrator, for the duration of the pulse pauses 17 '.
  • the switch 16 remains in a neutral position in which neither of the two integrators 17 or 17 'is acted upon by the received signal.
  • the switch 16 is preferably formed by a controlled switch.
  • the integrator 17 receives exclusively the reflected infrared transmission signal including any remnants of the filtered interference signal from the time of the transmission pulses, and the integrator 17 'receives only possible residues of the filtered interference signal from the time of the pulse pauses. so that the reflected infrared transmission signal can be obtained by simply forming the difference between the output signals of the two integrators 17 and 17 '.
  • the aforementioned difference formation takes place in a stage 18 connected downstream of the two integrators 17, 17 '. Its output signal is the infrared transmission signal U n , largely cleaned of interference and reflected from the monitoring room, which forms the useful signal for the signal evaluation.
  • the reflected infrared transmission signal will also remain constant. However, if an object moves in the monitoring room, regardless of whether it is a living being, a machine or any object, the reflected infrared transmission signal changes accordingly. Gaseous substances only influence the reflected signal if the reflection behavior of the space or section of the space containing the substance changes. The latter means that mere air movements, such as warm air rising from a radiator, are not detected by the detector and therefore cannot trigger a false alarm, whereas the sudden occurrence of vapors or smoke and the like alters the reflection behavior and therefore changes Detector is detected.
  • the useful signal U n is supplied on the one hand to a controller 19 and on the other hand to two comparators 20 and 20 '.
  • the output of the controller 19 is connected to the one input of a second modulator 21, the second input of which is connected to the control stage 12 and the output of which is connected to the input of the current / voltage converter 14.
  • the second modulator 21 superimposes a compensation current Ik on the signal of the photodiode 5, the time conditions for the superimposition of this compensation current being determined by the control stage 12.
  • the controller 19 changes the compensation current I ⁇ until the output signal of stage 18, ie the useful signal U n, becomes zero. This means that the maximum sensitivity is always maintained.
  • the control loop can be compared with a self-balancing scale or with a bridge circuit, the value zero of the useful signal representing the rest position.
  • Each received infrared signal, including the unwanted basic signal, is compensated for to zero.
  • This is the only way to use a common optic 8 for the transmitter and receiver S or E (FIG. 1). This is because reflections of lenses, mirrors and / or infrared windows caused on the transmitter side, which will usually exceed the reflection signal of a possible object in the surveillance space by potencies suppressed by the control loop.
  • a strongly reflecting object in the field of view of the detector does not lead to a loss in sensitivity, but is compensated for, and the maximum sensitivity is retained.
  • the comparators 20 and 20 ' are used for signal evaluation. They compare the useful signal U n with an upper limit value (comparator 20) and a lower limit value (comparator 20 ') and deliver an alarm signal to the alarm output 10 when it is exceeded or undershot. This signal evaluation can take place in spite of the described compensation of the useful signal, because the whole control process is so slow that the infrared signal received by the photodiode 5 is not immediately corrected to zero even with very careful and slow penetration into the monitoring space, so that the Both comparators 20, 20 'have sufficient time for a detection.
  • the controller 19 Because of the considerable size of the interference reflections caused by imperfect optics 8 or windows 9 (FIG. 1), the controller 19 has to compensate for a very large amount, as a rule over 90% of the total reflections, the interference reflections being caused by the geometry and material of the optics and windows have a fixed value. It would be desirable to compensate for this fixed value by means of an additional, fixed compensation current Ij ⁇ ', as a result of which the amount of total reflections to be compensated by the controller 19 would decrease sharply and the resolution would increase considerably. In this case, the controller 19 would have to accept not only the reflections from the monitoring room, but also any deviations caused by manufacturing tolerances and / or specimen variations of the infrared light-emitting diode 4.
  • a third modulator 22 which is also controlled by the control stage 12, is provided to generate the compensation current ty.
  • This is either set to a fixed value of the compensation current 1 ⁇ 'or, as shown in the figure, it is adjustable.
  • the compensation ström Ik ' are adjusted so that not only the above-mentioned interference reflections, but also the deviations caused by the infrared light emitting diode 4 are compensated.
  • the controller 19 has an approximately logarithmic behavior. If it takes a certain time t to regulate a small change in the useful signal, then regulating a change ten times as large only requires twice the time 2t. This behavior is particularly advantageous when the detector is switched on, where the change in the useful signal is 100% and still does not waste an unnecessarily long time for the regulation.
  • the alarm signal at alarm output 10 can be further evaluated, for example checked for plausibility, what can take place in the detector or in a control center, or it is passed on to a control center without further processing, where an alarm is then triggered.
  • the alarm signal can additionally or alternatively activate a light-emitting diode 23 arranged in the detector.
  • a relay 24 is also provided, the contacts of which enable potential-free evaluation of the alarm signal.
  • the photodiode 5 forming the actual motion detector is connected in parallel with a second photodiode 5 'with preferably identical data with reversed polarity.
  • the geometry of the arrangement is selected such that the one photodiode 5 is arranged at the focal point of the optics 8 (FIG. 1) and the second photodiode 5 'outside of it.
  • the one photodiode 5 receives the radiation reflected from the interstitial space plus any interference reflections
  • the second photodiode 5 ' only receives the interference reflections. So the difference corresponds the photocurrents of the two photodiodes 5 and 5 'the signal sought from the monitoring room, which may at most be superimposed by interference signals such as solar radiation or room lighting.
  • the temperature coefficients of the photosensitivity are mutually compensated for the common received signals.
  • all those influences and potential sources of interference that have an effect on both photodiodes remain ineffective. Influences or disturbances of this type are in particular specimen scatter and temperature drifts of the infrared light-emitting diode 4, as well as specimen scatter and changes over time in the reflection constants of the relevant mechanical components, such as varying colors and surface structures.
  • the controller 19 and the second modulator 21 thus only have the compensation of the infrared signals reflected from the monitoring room, whereas around 95% of the total reflections and photo currents are compensated by the second photo diode 5 '.
  • the influence of the controller 19 can be reduced to around ⁇ 5%, as a result of which.
  • Resolution of the useful signal U n rises to about ten times, which corresponds to approximately ten times the sensitivity for constant limits of the comparators 20, 20 '.
  • Known dual passive infrared motion detectors of this type combine the passive infrared radiation with ultrasound or with microwaves.
  • active infrared motion detector a combination of active / passive infrared is conceivable.
  • Such a combination would be preferable to the known combinations of infrared ultrasound and infrared / microwaves not least because the infrared radiation behaves exactly the same as the visible light and can therefore be controlled with the optical means known from visible light.
  • Infrared radiation is particularly important when protecting easily penetrable areas with an infrared curtain, for example when protecting pictures or sculptures in galleries or museums, or when protecting entire window areas.
  • the evaluation circuit 2 'shown in FIG. 4 differs from the evaluation circuit 2 of FIG. 2 essentially in that another controller is used and in that the controller signal is converted analog / digital and thus for the evaluation in digitized form is available.
  • the first modulator 11 is controlled by a program control stage 26, which has a counter 27, among other things.
  • the program control stage 26 receives its clock from a clock generator 13 and determines the chronological sequence and the length of the signals emitted to the infrared light-emitting diode 4.
  • the reference numeral 28 denotes a temperature sensor assigned to the first modulator 11 for compensating the temperature response of the control circuit containing the infrared light-emitting diode 4 and the photodiode 5.
  • stage 18 downstream of the two integrators 17 and 17 ' the signal processing proceeds analogously to that in the evaluation circuit shown in FIG. 2.
  • the output signal U n of stage 18, which forms the useful signal for the signal evaluation is fed to a controller 29, which is preferably a so-called PID controller, that is to say a controller with a proportional, integral and differential component, and arrives from it a voltage / pulse width converter 30.
  • PID controller a controller with a proportional, integral and differential component
  • the pulse-shaped signal from the converter 30 reaches the program control stage 26, the counter 27 of which counts the clock clocks per width of each of the pulses of this signal. Because of the proportionality between the pulse width and the output signal of the controller 29, the number of clock cycles determined by the counter 27 per pulse width represents a digital image of the analog output signal of the PID controller 29.
  • the constant pulse + pulse pause length is determined by the program control stage 26 and is approximately 1 ms at a clock frequency of 4 MHz and when using a 12-bit counter. This means that 1,000 results per second of a maximum of 12 bits, that is 4,096 pieces of information, are available with an accuracy of ⁇ 1d plus the possible error of the converter 30.
  • the differential component of the signal supplied to the PID controller 29 can lead to a certain instability of the digital signal, it is advantageous to supply this signal component to a differential controller 31.
  • the differential component can be divided between the two controllers 29 and 31, or the entire differential component can be routed to the differential controller 31, or the differential controller can be omitted and only the PID controller 29 can be used. Decisive for which of these solutions one chooses will be the ratio between effort on the one hand and sensitivity and reliability on the other hand. However, it should be emphasized that all three solutions are fully functional and deliver satisfactory results.
  • the values of the clock clocks determined by the counter 27 pass from the program control stage 26 into a pulse width / voltage converter 32, in which a voltage corresponding to the respective counter value is generated with reference to a reference voltage obtained from the reference voltage source 25, which voltage corresponds to the compensation current Ik determined.
  • An accuracy of ⁇ 0.001% can easily be achieved here, so that the compensation current corresponds exactly to the level of the counter 27.
  • the output of the differential controller 31 is also connected to the pulse width / voltage converter 32 and supplies it with the higher-frequency components of the useful signal U n .
  • the output of converter 32 is connected to one input of second modulator 21 (FIG. 2), the second input of which is connected to program control stage 26 and the output of which is connected to the input of current / voltage converter 14.
  • the second modulator 21 superimposes the compensation current Ik on the signal of the photodiode 5 in the opposite phase, the time conditions for this superimposition being determined by the program control stage 26.
  • the PID controller 29 changes its output signal and thus the pulse / pause ratio in such a way that the output signal of the stage 18, that is to say the useful signal U n , becomes zero.
  • the state of the counter 27 thus corresponds to the infrared deviation of the monitored room except for the already mentioned possible deviation of ⁇ 1d.
  • the accuracy can be further increased by averaging from a large number of individual values.
  • averaging can be carried out, for example, by the counter 27 or by a microprocessor 33 connected downstream of the program control stage 26.
  • the microprocessor facilitates a sensible coupling of the measuring principle described with a second in a so-called dual detector.
  • the microprocessor 33 which transmits the alarm signal present as a result of the evaluation to the alarm output 10, can check the alarm signal for plausibility and thereby relieve the control center.
  • the compensating electronics make it possible to use a common transmitting / receiving optic. This is because reflections from lenses, mirrors and / or from the infrared window caused on the transmission side, which as a rule exceed the reflection signal of a possible object in the monitoring room by potencies, are suppressed by the control loop.
  • the digitization of the signal offers the possibility of acquiring absolute values of the infrared radiation and thereby enabling real presence detection, and it enables the use of a microprocessor with all of its advantages.
  • the detection of the absolute values of the infrared radiation enables the determination of their sign, that is to say whether there is a positive or negative change in the reflection and thus an object movement towards or away from the detector.
  • the proposed analog / digital converter is considerably cheaper than any commercially available A / D converter with the same resolution.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Computer Security & Cryptography (AREA)
  • Geophysics And Detection Of Objects (AREA)
  • Burglar Alarm Systems (AREA)
  • Photometry And Measurement Of Optical Pulse Characteristics (AREA)

Abstract

The IR intrusion detector proposed includes a transmitter (4), a receiver (5) and an evaluation circuit (2') with means (14 to 18) for producing a useful signal (Un). The evaluation circuit (2') includes a control unit (29) to which the useful signal (Un) is fed and which is connected to the receiver output, the control unit being designed to provide a compensation signal (Ik) superimposed on the receiver signal (Ie). The compensation signal is selected such that the useful signal (Un) is stabilized at zero in order to maintain the sensitivity at its maximum level. In a preferred embodiment of the invention, an analogue/digital converter (26, 30) is connected in series with the control unit (29), the converter digitizing the control signal and being connected to a digital/analogue converter (25, 32) designed to generate a voltage corresponding to the value of the digital signal. This voltage determines the compensation signal (Ik).

Description

Aktiver Infrarotmelder Active infrared detector
Die vorliegende Erfindung liegt auf dem Gebiet der Infrarotmelder, das sind Detektoren, die einen Raum auf unbefugtes Eindringen überwachen und zu diesem Zweck eine vom Detektor empfangene Infrarotstrahlung auswerten. Es gibt zwei Arten derartiger Infrarot¬ melder, die passiven und die aktiven.The present invention is in the field of infrared detectors, which are detectors that monitor a room for unauthorized entry and for this purpose evaluate infrared radiation received by the detector. There are two types of such infrared detectors, the passive and the active.
Bei den passiven IiLfrarotmeldern wartet der Melder bis eine Strahlungsquelle, die eine von der Umgebung unterschiedliche Strahlung aussendet, also eine andere Temperatur als ihre Umgebung aufweist, in das Gesichtsfeld eindringt. Die passiven Infrarotmelder, die relativ preisgünstig und heute weit verbreitet sind, können vom Prinzip her nur strahlende Objekte detektieren und stossen an eine Grenze, sobald Objekte, beispielweise Wertge¬ genstände, überwacht werden sollen, die mit mechanischen, nicht detektierbaren Mitteln entfernbar sind. Ausserdem müssen bei den passiven Infrarotmeldern spezielle Massnah- men gegen das sogenannte Maskieren, das ist das unbemerkte Verändern oder Abdecken des Gesichtsfeldes des Melders, getroffen werden.In the case of passive infrared detectors, the detector waits until a radiation source that emits radiation that differs from the surroundings, that is to say has a different temperature than its surroundings, penetrates into the visual field. The passive infrared detectors, which are relatively inexpensive and widely used today, can in principle only detect radiating objects and reach a limit as soon as objects, for example valuables, are to be monitored that can be removed by mechanical, non-detectable means. In addition, special measures against so-called masking, that is the unnoticed changing or covering of the detector's field of view, must be taken with passive infrared detectors.
Im Unterschied zu den passiven verarbeiten die aktiven Infrarotmelder nicht die von im Gesichtsfeld befindlichen Objekten abgegebene Wärmestrahlung, sondern sie bestrahlen den zu überwachenden Raum aktiv und reagieren auf Veränderungen der reflektierten In¬ frarotstrahlung. Dadurch können sie auch Bewegungen von "toten", also nicht strahlen¬ den Gegenständen detektieren. Ausserdem sind sie nur sehr schwer zu maskieren, weil sie jede Annäherung bemerken. Dafür haben die aktiven Infrarotmelder gewisse Schwierig¬ keiten bei der Empfindlichkeit und bei der Fehlalarmsicherheit, weil die reflektierte Infra¬ rotstrahlung von so starken Störungen überlagert sein kann, dass eine sichere Detektion von Bewegungen nahezu unmöglich wird. Die Erfindung betrifft einen aktiven Infrarotmelder zur Detektion von Bewegungen in einem Überwachungsraum, mit einem Sender zur Aussendung einer modulierten Infra¬ rotstrahlung in den Überwachungsraum, mit einem Empfänger für die aus dem Überwa¬ chungsraum reflektierte Infrarotstrahlung, und mit einer an den Empfänger angeschlos¬ senen und Mittel zur Gewinnung eines Nutzsignals enthaltenden Auswerteschaltung.In contrast to the passive ones, the active infrared detectors do not process the thermal radiation emitted by objects in the visual field, but rather actively irradiate the space to be monitored and react to changes in the reflected infrared radiation. As a result, they can also detect movements of "dead", ie non-radiating objects. In addition, they are very difficult to mask because they notice any approach. For this, the active infrared detectors have certain difficulties in terms of sensitivity and false alarm security because the reflected infrared radiation can be overlaid by such strong interference that a reliable detection of movements is almost impossible. The invention relates to an active infrared detector for the detection of movements in a surveillance room, with a transmitter for transmitting modulated infrared radiation into the surveillance room, with a receiver for the infrared radiation reflected from the surveillance room, and with one connected to the receiver and means for obtaining an evaluation circuit containing a useful signal.
Bei einem in der GB-A-2 187 825 beschriebenen Melder dieser Art enthält die Aus¬ werteschaltung einen als Synchronverstärker ausgebildeten Operationsverstärker, von . dem nur diejenigen Empfangssignale verstärkt werden, die mit dem ausgesandten Signal in Phase sind. Diese Signale werden in zwei Integratoren mit verschiedenen Zeitkonstan¬ ten integriert, wobei im ungestörten Zustand beide Integratoren die gleiche Spannung erzeugen, und eine Differenz zwischen diesen Spannungen auf einen Eindringling hin¬ weist. Dieser Infrarotmelder kann bezüglich Ansprechsicherheit nicht befriedigen, weil die Integration des Empfangssignals mit zwei verschiedenen Zeitkonstanten keine aus¬ reichende Gewähr dafür bietet, dass jede Objektbewegung im Überwachungsraum auch tatsächlich erkannt wird. Der Melder ist auch nicht fehlalarmsicher, weil nicht ausge¬ schlossen werden kann, dass eine Differenz zwischen den Signalen der Integratoren durch andere Ursachen als durch eine Objektbewegung verursacht wird.In the case of a detector of this type described in GB-A-2 187 825, the evaluation circuit contains an operational amplifier designed as a synchronous amplifier, from. which only those receive signals that are in phase with the transmitted signal are amplified. These signals are integrated in two integrators with different time constants, both integrators generating the same voltage in the undisturbed state, and a difference between these voltages indicates an intruder. This infrared detector cannot be satisfactory in terms of responsiveness, because the integration of the received signal with two different time constants does not offer a sufficient guarantee that every object movement in the surveillance space is actually recognized. The detector is also not false alarm-proof, because it cannot be ruled out that a difference between the signals of the integrators is caused by causes other than an object movement.
Durch die Erfindung soll nun dieser bekannte aktive Infrarotmelder hinsichtlich Empfind¬ lichkeit, Zuverlässigkeit und Unempfindlichkeit gegenüber Fremdeinflüssen verbessert werden.The invention is now intended to improve this known active infrared detector with regard to sensitivity, reliability and insensitivity to external influences.
Der erfindungsgemässe aktive Infrarotmelder zur Lösung der gestellten Aufgabe ist da¬ durch gekennzeichnet, dass die Auswerteschaltung einen einerseits mit dem Nutzsignal beaufschlagten und andererseits mit dem Ausgang des Empfängers verbundenen Regler zur Abgabe eines dem Empfängersignal überlagerten Kompensationssignals aufweist, und dass das Kompensationssignal so gewählt ist, dass eine Ausregelung des Nutzsignals auf den Wert null erfolgt. Die Ausregelung des Nutzsignals auf den Wert null hat den Vorteil, dass immer die maxi¬ male Empfindlichkeit erhalten bleibt; der Empfänger wirkt also gleichsam wie eine sich selbst austarierende Waage. Daraus ergibt sich unmittelbar, dass auch ein unerwünschtes Störsignal, sofern dieses die gleiche Frequenz und Phase wie die ausgesandte Infrarot¬ strahlung hat, auf null kompensiert wird und nicht etwa zu einer Drosselung des Empfän¬ gers auf minimale Empfindlichkeit führt. Störsignale anderer Frequenzen sind nicht so kritisch, weil sie einfach ausgefiltert werden können.The active infrared detector according to the invention for solving the problem is characterized in that the evaluation circuit has a controller which is acted upon on the one hand with the useful signal and on the other hand connected to the output of the receiver for emitting a compensation signal which is superimposed on the receiver signal, and that the compensation signal is selected such that that the useful signal is adjusted to the value zero. The adjustment of the useful signal to the value zero has the advantage that the maximum sensitivity is always retained; the receiver acts like a self-balancing scale. This immediately results in an undesired interference signal, provided that it has the same frequency and phase as the emitted infrared radiation, is compensated for to zero and does not lead to a throttling of the receiver to minimal sensitivity. Interference signals from other frequencies are not so critical because they can be easily filtered out.
Eine erste bevorzugte Ausfuhrungsform des erfmdungsgemässen Infrarotmelders ist da¬ durch gekennzeichnet, dass für Sender und Empfänger eine gemeinsame Optik vorgese¬ hen ist. Die Verwendung einer gemeinsamen Optik ermöglicht eine massive Reduktion der Herstellkosten und der Abmessungen, sowie die Erzielung einer maximalen Reich¬ weite bei geringem Stromverbrauch.A first preferred embodiment of the infrared detector according to the invention is characterized in that common optics are provided for the transmitter and receiver. The use of a common optic enables a massive reduction in manufacturing costs and dimensions, as well as the achievement of a maximum range with low power consumption.
Eine zweite bevorzugte Ausfuhrungsform des erfmdungsgemässen Infrarotmelders ist dadurch gekennzeichnet, dass die Auswerteschaltung einen dem Regler nachgeschalteten Analog/Digital-Wandler aufweist, an dessen einem Ausgang das digitalisierte Reglersi¬ gnal erhältlich und dessen anderer Ausgang mit einem Digital/Analog-Wandler zur Er¬ zeugung einer dem jeweiligen digitalen Signalwert entsprechenden Spannung verbunden ist, und dass diese Spannung zur Erzeugung des Kompensationssignals verwendet wird. Die Digitalisierung des Reglersignals hat den Vorteil, dass eine gegenüber bisher diffe¬ renziertere und intelligentere Signalauswertung möglich wird.A second preferred embodiment of the infrared detector according to the invention is characterized in that the evaluation circuit has an analog / digital converter connected downstream of the controller, at one output of which the digitized controller signal is available and the other output with a digital / analog converter for generation a voltage corresponding to the respective digital signal value is connected, and that this voltage is used to generate the compensation signal. The digitization of the controller signal has the advantage that a signal evaluation that is more differentiated and intelligent than before is possible.
Eine solche Signalauswertung ist besonders dann möglich, wenn so wie bei einer weite¬ ren bevorzugten Ausführungsform des erfmdungsgemässen Infrarotmelders der eine Aus¬ gang des Analog/Digital-Wandlers mit einem Mikroprozessor verbunden ist. Der Mikro¬ prozessor ermöglicht einerseits eine Erhöhung der Auflösung und er schafft andererseits die Voraussetzung, den im Infrarotmelder vorhandenen Sensor mit einem zweiten, nach einem anderen Detekrionsprinzip arbeitenden Sensor zu koppeln und die Signale beider Sensoren gemeinsam auszuwerten.Such a signal evaluation is particularly possible if, as in a further preferred embodiment of the infrared detector according to the invention, the one output of the analog / digital converter is connected to a microprocessor. On the one hand, the microprocessor enables an increase in the resolution and, on the other hand, it creates the prerequisite for copying the sensor present in the infrared detector with a second to couple another sensor principle and to evaluate the signals of both sensors together.
Im folgenden wird die Erfindung anhand von in den Zeichnungen dargestellten Ausfüh¬ rungsbeispielen näher erläutert; dabei zeigt:The invention is explained in more detail below with reference to exemplary embodiments shown in the drawings; shows:
Fig. 1 eine schematische Schnittdarstellung eines erfmdungsgemässen Infrarotmelders, Fig. 2 ein Blockschaltbild eines ersten Ausfuhrungsbeispiels der Auswerteschaltung desFig. 1 is a schematic sectional view of an infrared detector according to the invention, Fig. 2 is a block diagram of a first embodiment of the evaluation circuit of the
Infrarotmelders von Fig. 1, Fig. 3 eine Detailvariante der Schaltung von Fig. 2; und Fig. 4 ein Blockschaltbild eines zweiten Ausfuhrungsbeispiels der Auswerteschaltung desInfrared detector of Fig. 1, Fig. 3 shows a detailed variant of the circuit of Fig. 2; and FIG. 4 shows a block diagram of a second exemplary embodiment of the evaluation circuit of the
Infrarotmelders von Fig. 1.Infrared detector of Fig. 1st
Der in Fig. 1 dargestellte aktive Infrarotbewegungsmelder 1 besteht im wesentlichen aus einem Sender S, der den zu überwachenden Raum mit pulsierendem Infrarotlicht be¬ strahlt, aus einem Empfänger E für die aus dem Überwachungsraum reflektierte Infrarot¬ strahlung, aus einer Auswerte- und Steuerelektronik 2 und aus einer Stromversorgung 3. Gemäss den Fig. 2 und 4 ist der Sender S durch eine Infrarotleuchtdiode (IRED) 4 und der Empfänger E durch eine Fotodiode 5 gebildet. Sender S, Empfänger E, Elektronik 2 und Stromversorgung 3 sind in einem gemeinsamen Gehäuse 6 angeordnet, das in dem zu überwachenden Raum an geeigneter Stelle, beispielsweise an einer Wand oder an der Decke montiert wird.The active infrared motion detector 1 shown in FIG. 1 essentially consists of a transmitter S which irradiates the room to be monitored with pulsating infrared light, a receiver E for the infrared radiation reflected from the monitoring room, and evaluation and control electronics 2 and from a power supply 3. According to FIGS. 2 and 4, the transmitter S is formed by an infrared light-emitting diode (IRED) 4 and the receiver E by a photodiode 5. Transmitter S, receiver E, electronics 2 and power supply 3 are arranged in a common housing 6, which is mounted in a suitable location in the room to be monitored, for example on a wall or on the ceiling.
Die Stromversorgung 3 ist an eine externe Speisung angeschlossen und enthält einen Fix¬ spannungsregler (nicht dargestellt). Das Gehäuse 6 enthält im Bereich des Senders S und des Empfängers E ein infrarot-durchlässiges Fenster 7. Ausserdem ist eine geeignete Op¬ tik 8 vorgesehen, die selbstverständlich nicht zwischen Fenster 7 einerseits und Sender und Empfänger S bzw. E andererseits angeordnet sein muss, sondern auch in das Fenster 7 integriert sein kann. Die Optik 8 kann eine Linsen- oder eine Spiegeloptik sein. Wesentlich ist, dass für Sender S und Empfänger E eine gemeinsame Optik vorgesehen ist. Dies bedeutet mit anderen Worten, dass der Empfänger E genau in diejenigen Berei¬ che des Überwachungsraums "sieht", die der Sender S gerade mit Infrarotstrahlung beauf¬ schlagt. Und das ermöglicht bei gleichem Stromverbrauch eine vervielfachte Reichweite oder bei gleicher Reichweite einen massiv reduzierten Stromverbrauch. Zwischen Sender S und Empfänger E ist eine Abschirmung 9 zur Verhinderung einer direkten Lichtverbin¬ dung zwischen diesen beiden Elementen angeordnet. Wie Fig. 1 weiter zu entnehmen ist, weist die Elektronik 2 einen Alarmausgang 10 für die bei der Signalauswertung gewonne¬ nen Alarmsignale auf. Diese können eine im jeweiligen Melder 1 eingebaute interne und/oder eine externe Alarmanzeige aktivieren.The power supply 3 is connected to an external supply and contains a fixed voltage regulator (not shown). The housing 6 contains an infrared-transmissive window 7 in the area of the transmitter S and the receiver E. In addition, suitable optics 8 are provided, which of course do not have to be arranged between the window 7 on the one hand and the transmitter and receiver S or E on the other hand, but can also be integrated into the window 7. The optics 8 can be a lens or a mirror optics. It is essential that common optics are provided for transmitter S and receiver E. In other words, this means that the receiver E "sees" exactly those areas of the monitoring room that the transmitter S is currently applying infrared radiation to. And this enables a multiple range with the same power consumption or a massively reduced power consumption with the same range. A shield 9 is arranged between the transmitter S and the receiver E to prevent a direct light connection between these two elements. As can also be seen in FIG. 1, the electronics 2 has an alarm output 10 for the alarm signals obtained during the signal evaluation. These can activate an internal and / or an external alarm display built into the respective detector 1.
Gemäss Fig. 2 ist der Infrarotleuchtdiode 4 ein erster Modulator 11 vorgeschaltet, durch den eine geeignete Modulation der von der Infrarotleuchtdiode 4 ausgesandten Strahlung erfolgt. Vorzugsweise besteht diese Strahlung aus einer fortlaufenden Folge von Pulsen und Pulspausen, so dass der zu überwachende Raum mit pulsierendem Infrarotlicht be¬ strahlt wird. Es kann auch sinnvoll sein, nach einer Folge von einer bestimmten Anzahl von Pulsen und Pulspausen eine längere, vorbestimmte Sendepause einzufügen. In diesem Fall erfolgt die Bestrahlung des Überwachungsraums durch intermittierend ausgesandte und von Sendepausen unterbrochene Impulszüge oder Impulspakete. Dabei können die Sendepausen zu den Impulszügen in einem festen oder in einem variablen zeitlichen Ver¬ hältnis stehen. Die Steuerung des ersten Modulators 11 erfolgt durch eine Steuerstufe 12, die ihren Takt von einem Taktgeber 13 erhält. Die Steuerstufe 12 bestimmt insbesondere die zeitliche Folge und die Länge der an die Infrarotleuchtdiode 4 abgegebenen Signale.2, a first modulator 11 is connected upstream of the infrared light-emitting diode 4, through which a suitable modulation of the radiation emitted by the infrared light-emitting diode 4 takes place. This radiation preferably consists of a continuous sequence of pulses and pulse pauses, so that the room to be monitored is irradiated with pulsating infrared light. It can also make sense to insert a longer, predetermined transmission pause after a sequence of a certain number of pulses and pulse pauses. In this case, the monitoring room is irradiated by pulse trains or pulse packets which are emitted intermittently and are interrupted by pauses in transmission. The transmission pauses to the pulse trains can be in a fixed or in a variable time ratio. The first modulator 11 is controlled by a control stage 12, which receives its clock from a clock generator 13. The control stage 12 determines in particular the time sequence and the length of the signals emitted to the infrared light-emitting diode 4.
Die von der Infrarotleuchtdiode 4 ausgesandte Infrarotstrahlung wird durch die Optik 8 (Fig. 1) gebündelt und in einen definierten Bereich des Überwachungsraums gerichtet. Die aus diesem Bereich reflektierte li-frarotstrahlung wird von der Optik 8 gesammelt und auf die lichtempfindliche Diode 5 geworfen. Von der Diode 5 wird die empfangene Infra¬ rotstrahlung in einen proportionalen Strom (Empfängersignal) Ie ungewandelt, der einem der Diode 5 nachgeschalteten Strom/Spannungswandler 14 zugeführt und von diesem in eine Spannung (Empfangssignal) Ue umgewandelt wird. Der Wandler 14 wirkt zusätzlich als eine Art von Filter für gleichförmiges Licht, indem er von der Sonne und von der Raumbeleuchtung herrührendes Licht unterdrückt. In einem dem Strom/Spannungswand¬ ler 14 nachgeschalteten Frequenzfilter 15 werden aus dem Empfangssignal Ue uner¬ wünschte Frequenzen herausgefiltert, wodurch insbesondere durch Glüh-, Fluoreszenz- und Entladungslampen verursachte Störungen unterdrückt werden. Der Ausgang des Fre¬ quenzfilters 15 ist mit einer von der Steuerstufe 12 im Takt der Modulation der Infrarot¬ leuchtdiode 4 gesteuerten Weiche 16 verbunden.The infrared radiation emitted by the infrared light-emitting diode 4 is bundled by the optics 8 (FIG. 1) and directed into a defined area of the monitoring room. The infrared radiation reflected from this area is collected by the optics 8 and thrown onto the light-sensitive diode 5. The received infrared radiation is converted by the diode 5 into a proportional current (receiver signal) I e , which a the current / voltage converter 14 connected downstream of the diode 5 and converted into a voltage (received signal) U e by the latter. The transducer 14 also acts as a type of filter for uniform light by suppressing light from the sun and room lighting. In a frequency filter 15 connected downstream of the current / voltage converter 14, undesired frequencies are filtered out from the received signal U e , as a result of which interference caused by incandescent, fluorescent and discharge lamps is suppressed. The output of the frequency filter 15 is connected to a switch 16 controlled by the control stage 12 in time with the modulation of the infrared light-emitting diode 4.
Das von Störungen weitgehend befreite Ausgangssignal des Frequenzfilters 15 wird über die Weiche 16 abwechselnd einem von zwei Integratoren 17, 17' zugeführt. Dabei ist die Weiche 16 von der Steuerstufe 12 so gesteuert, das das Empfangssignal Ue während der Sendedauer der Impulse an den einen Integrator, beispielsweise an den Integrator 17, und während der Dauer der Pulspausen an den anderen Integrator, beispielsweise an den Inte¬ grator 17', geleitet wird. Während allfälliger Sendepausen zwischen den Impulszügen oder Impulspaketen verharrt die Weiche 16 in einer neutralen Stellung, in der keiner der beiden Integratoren 17 oder 17' mit dem Empfangssignal beaufschlagt ist. Die Weiche 16 ist vorzugsweise durch einen gesteuerten Schalter gebildet.The output signal of the frequency filter 15, which is largely free of interference, is alternately fed to one of two integrators 17, 17 'via the switch 16. The switch 16 is controlled by the control stage 12 in such a way that the received signal U e is sent to one integrator, for example to the integrator 17, during the duration of the pulse transmission and to the other integrator, for example to the integrator, for the duration of the pulse pauses 17 '. During any pauses in transmission between the pulse trains or pulse packets, the switch 16 remains in a neutral position in which neither of the two integrators 17 or 17 'is acted upon by the received signal. The switch 16 is preferably formed by a controlled switch.
Aufgrund der Steuerung der Weiche 16 im Takt der Modulation erhält der Integrator 17 ausschliesslich das reflektierte Infrarotsendesignal einschliesslich eventueller Reste des gefilterten Störsignals aus der Zeit der Sendepulse, und der Integrator 17' erhält nur even¬ tuelle Reste des gefilterten Störsignals aus der Zeit der Pulspausen, so dass durch eine einfache Differenzbildung der Ausgangssignale der beiden Integratoren 17 und 17' das reflektierte Infrarotsendesignal gewonnen werden kann. Die genannte Differenzbildung erfolgt in einer den beiden Integratoren 17, 17' nachgeschalteten Stufe 18. Deren Aus¬ gangssignal ist das von Störungen weitgehend gereinigte, aus dem Überwachungsraum re¬ flektierte Infrarotsendesignal Un, welches das Nutzsignal für die Signalauswertung bildet. Solange sich die Bedingungen im Überwachungsraum nicht ändern, wird auch das reflek¬ tierte Infrarotsendesignal konstant bleiben. Erfolgt jedoch im Überwachungsraum eine Bewegung eines Objekts, gleichgültig ob es sich dabei um ein Lebewesen, eine Maschine oder um irgendeinen Gegenstand handelt, dann kommt es zu einer entsprechenden Ände¬ rung des reflektierten Infrarotsendesignals. Gasförmige Stoffe beeinflussen das reflektier¬ te Signal nur dann, wenn sich das Reflexionsverhalten des den betreffenden Stoff enthal¬ tenden Raums oder Raumabschnitts ändert. Letzteres bedeutet, dass blosse Luftbewegun¬ gen, wie beispielsweise von einem Heizkörper aufsteigende warme Luft, vom Melder nicht detektiert werden und daher auch keinen Fehlalarm auslösen können, wogegen das plötzliche Auftreten von Dämpfen oder von Rauch und dergleichen das Reflexionsverhal¬ ten verändert und daher vom Melder detektiert wird.Due to the control of the switch 16 in time with the modulation, the integrator 17 receives exclusively the reflected infrared transmission signal including any remnants of the filtered interference signal from the time of the transmission pulses, and the integrator 17 'receives only possible residues of the filtered interference signal from the time of the pulse pauses. so that the reflected infrared transmission signal can be obtained by simply forming the difference between the output signals of the two integrators 17 and 17 '. The aforementioned difference formation takes place in a stage 18 connected downstream of the two integrators 17, 17 '. Its output signal is the infrared transmission signal U n , largely cleaned of interference and reflected from the monitoring room, which forms the useful signal for the signal evaluation. As long as the conditions in the monitoring room do not change, the reflected infrared transmission signal will also remain constant. However, if an object moves in the monitoring room, regardless of whether it is a living being, a machine or any object, the reflected infrared transmission signal changes accordingly. Gaseous substances only influence the reflected signal if the reflection behavior of the space or section of the space containing the substance changes. The latter means that mere air movements, such as warm air rising from a radiator, are not detected by the detector and therefore cannot trigger a false alarm, whereas the sudden occurrence of vapors or smoke and the like alters the reflection behavior and therefore changes Detector is detected.
Das Nutzsignal Un wird einerseits einem Regler 19 und andererseits zwei Komparatoren 20 und 20' zugeführt. Der Ausgang des Reglers 19 ist mit dem einen Eingang eines zwei¬ ten Modulators 21 verbunden, dessen zweiter Eingang mit der Steuerstufe 12 und dessen Ausgang mit dem Eingang des Strom/Spannungswandlers 14 verbunden ist. Der zweite Modulator 21 überlagert dem Signal der Photodiode 5 im Gegentakt einen Kompensati¬ onsstrom Ik, wobei die zeitlichen Bedingungen für die Überlagerung dieses Kompensati¬ onsstroms durch die Steuerstufe 12 bestimmt werden. Der Regler 19 ändert den Kompen¬ sationsstrom I^ so lange, bis das Ausgangssignal der Stufe 18, also das Nutzsignal Un null wird. Damit bleibt immer die maximale Empfindlichkeit erhalten.The useful signal U n is supplied on the one hand to a controller 19 and on the other hand to two comparators 20 and 20 '. The output of the controller 19 is connected to the one input of a second modulator 21, the second input of which is connected to the control stage 12 and the output of which is connected to the input of the current / voltage converter 14. The second modulator 21 superimposes a compensation current Ik on the signal of the photodiode 5, the time conditions for the superimposition of this compensation current being determined by the control stage 12. The controller 19 changes the compensation current I ^ until the output signal of stage 18, ie the useful signal U n, becomes zero. This means that the maximum sensitivity is always maintained.
Der Regelkreis kann mit einer selbst abgleichenden Waage oder mit einer Brückenschal¬ tung verglichen werden, wobei der Wert null des Nutzsignals die Ruhelage darstellt. Je¬ des empfangene Infrarotsignal, auch das unerwünschte Grundsignal, wird auf null kom¬ pensiert. Erst dadurch eröffnet sich die Möglichkeit, für Sender und Empfänger S bzw. E (Fig. 1) eine gemeinsame Optik 8 zu verwenden. Denn senderseitig verursachte Reflexi¬ onen von Linsen, Spiegeln und/oder Infrarotfenster, die das Reflexionssignal eines mög¬ lichen Objekts im Überwachungsraum in der Regel um Potenzen übertreffen, werden durch den Regelkreis unterdrückt. Ein stark reflektierendes Objekt im Blickfeld des Mel¬ ders führt nicht zu einer Empfindlichkeitseinbusse, sondern wird wegkompensiert, und die maximale Empfindlichkeit bleibt erhalten.The control loop can be compared with a self-balancing scale or with a bridge circuit, the value zero of the useful signal representing the rest position. Each received infrared signal, including the unwanted basic signal, is compensated for to zero. This is the only way to use a common optic 8 for the transmitter and receiver S or E (FIG. 1). This is because reflections of lenses, mirrors and / or infrared windows caused on the transmitter side, which will usually exceed the reflection signal of a possible object in the surveillance space by potencies suppressed by the control loop. A strongly reflecting object in the field of view of the detector does not lead to a loss in sensitivity, but is compensated for, and the maximum sensitivity is retained.
Die Komparatoren 20 und 20' dienen zur Signalauswertung. Sie vergleichen das Nutzsi¬ gnal Un mit einem oberen Grenzwert (Komparator 20) und einem unteren Grenzwert (Komparator 20') und liefern bei dessen Über- bzw. Unterschreitung an den Alarmaus¬ gang 10 ein Alarmsignal. Diese Signalauswertung kann trotz der beschriebenen Kompen¬ sation des Nutzsignals erfolgen, weil nämlich der ganze Regelvorgang so langsam ist, dass auch bei sehr vorsichtigem und langsamem Eindringen in den Überwachungsraum das von der Fotodiode 5 empfangene Infrarotsignal nicht sofort auf null ausgeregelt wird, so dass den beiden Komparatoren 20, 20' ausreichend Zeit für eine Detektion verbleibt.The comparators 20 and 20 'are used for signal evaluation. They compare the useful signal U n with an upper limit value (comparator 20) and a lower limit value (comparator 20 ') and deliver an alarm signal to the alarm output 10 when it is exceeded or undershot. This signal evaluation can take place in spite of the described compensation of the useful signal, because the whole control process is so slow that the infrared signal received by the photodiode 5 is not immediately corrected to zero even with very careful and slow penetration into the monitoring space, so that the Both comparators 20, 20 'have sufficient time for a detection.
Wegen der beachtlichen Grosse der durch nicht perfekte Optik 8 oder Fenster 9 (Fig. 1) verursachten Störreflexionen muss der Regler 19 einen sehr grossen Betrag von in der Regel über 90% der gesamten Reflexionen kompensieren, wobei die Störreflexionen einen durch Geometrie und Material von Optik und Fenster bedingten fixen Wert haben. Es wäre wünschenswert, diesen fixen Wert durch einen zusätzlichen, fixen Kompensati¬ onsstrom Ij^' auszugleichen, wodurch der Betrag der vom Regler 19 zu kompensierenden Gesamtreflexionen stark sinken und die Auflösung beträchtlich steigen würde. Der Regler 19 hätte in diesem Fall neben den Reflexionen aus dem Überwachungsraum allenfalls noch durch Fabrikationstoleranzen und/oder Exemplarstreuungen der Infrarotleuchtdiode 4 bedingte Abweichungen zu übernehmen.Because of the considerable size of the interference reflections caused by imperfect optics 8 or windows 9 (FIG. 1), the controller 19 has to compensate for a very large amount, as a rule over 90% of the total reflections, the interference reflections being caused by the geometry and material of the optics and windows have a fixed value. It would be desirable to compensate for this fixed value by means of an additional, fixed compensation current Ij ^ ', as a result of which the amount of total reflections to be compensated by the controller 19 would decrease sharply and the resolution would increase considerably. In this case, the controller 19 would have to accept not only the reflections from the monitoring room, but also any deviations caused by manufacturing tolerances and / or specimen variations of the infrared light-emitting diode 4.
Wie Fig. 2 zu entnehmen ist, ist zur Erzeugung des Kompensationsstroms ty ein eben¬ falls von der Steuerstufe 12 gesteuerter dritter Modulator 22 vorgesehen. Dieser ist ent¬ weder auf einen fixen Wert des Kompensationsstroms 1^' eingestellt, oder er ist, so wie in der Figur dargestellt, einstellbar ausgebildet. Im letzteren Fall kann der Kompensations- ström Ik' so justiert werden, dass nicht nur die genannten Störreflexionen, sondern auch die durch die Infrarotleuchtdiode 4 bedingten Abweichungen kompensiert werden.As can be seen in FIG. 2, a third modulator 22, which is also controlled by the control stage 12, is provided to generate the compensation current ty. This is either set to a fixed value of the compensation current 1 ^ 'or, as shown in the figure, it is adjustable. In the latter case, the compensation ström Ik 'are adjusted so that not only the above-mentioned interference reflections, but also the deviations caused by the infrared light emitting diode 4 are compensated.
Der Regler 19 hat ein annähernd logarithmisches Verhalten. Wenn er zur Ausregelung einer kleinen Änderung des Nutzsignals eine bestimmte Zeit t benötigt, dann erfordert die Ausregelung einer zehnmal so grossen Änderung nur die doppelte Zeit 2t. Dieses Verhal¬ ten ist besonders beim Einschalten des Melders vorteilhaft, wo die Änderung des Nutzsi¬ gnals 100% beträgt und für die Ausregelung trotzdem nicht unnötig viel Zeit verstreicht.The controller 19 has an approximately logarithmic behavior. If it takes a certain time t to regulate a small change in the useful signal, then regulating a change ten times as large only requires twice the time 2t. This behavior is particularly advantageous when the detector is switched on, where the change in the useful signal is 100% and still does not waste an unnecessarily long time for the regulation.
Das Alarmsignal am Alarmausgang 10 kann weiter ausgewertet, beispielsweise auf Plau- sibilität überprüft werden, was im Melder oder in einer Zentrale erfolgen kann, oder es wird ohne Weiterverarbeitung an eine Zentrale geleitet, wo dann Alarm ausgelöst wird. Das Alarmsignal kann zusätzlich oder alternativ eine im Melder angeordnete Leuchtdiode 23 aktivieren. Darstellungsgemäss ist ausserdem ein Relais 24 vorgesehen, dessen Kon¬ takte eine potentialfreie Auswertung des Alarmsignals ermöglichen. Durch separate Un¬ tersuchung der Ausgangssignale der beiden Komparatoren 20 und 20' auf ihr Vorzeichen, also durch Auswertung der positiven oder negativen Änderungen der Reflexionen, kann die Bewegungsrichtung eines Objekts im Überwachungsraum, auf den Melder zu oder von diesem weg, festgestellt werden.The alarm signal at alarm output 10 can be further evaluated, for example checked for plausibility, what can take place in the detector or in a control center, or it is passed on to a control center without further processing, where an alarm is then triggered. The alarm signal can additionally or alternatively activate a light-emitting diode 23 arranged in the detector. According to the illustration, a relay 24 is also provided, the contacts of which enable potential-free evaluation of the alarm signal. By separately examining the output signals of the two comparators 20 and 20 'for their sign, that is to say by evaluating the positive or negative changes in the reflections, the direction of movement of an object in the monitoring space, towards or away from the detector, can be determined.
In Fig. 3 ist eine weitere Möglichkeit zur Unterdrückung oder Kompensation von uner¬ wünschten Reflexionen dargestellt. Bei dieser Variante, bei der kein dritter Modulator 22 (Fig. 2) erforderlich ist, wird der den eigentlichen Bewegungsdetektor bildenden Fotodi¬ ode 5 eine zweite Fotodiode 5' mit vorzugsweise identischen Daten mit umgekehrter Po¬ larität parallelgeschaltet. Dabei ist die Geometrie der Anordnung so gewählt, dass die eine Fotodiode 5 im Brennpunkt der Optik 8 (Fig. 1) und die zweite Fotodiode 5' ausser- halb von diesem angeordnet ist. Dadurch empfängt die eine Fotodiode 5 die aus dem Überwachungsraum reflektierte Strahlung plus die allfälligen Störreflexionen, wogegen die zweite Fotodiode 5' nur die Störreflexionen empfängt. Somit entspricht die Differenz der Fotoströme der beiden Fotodioden 5 und 5' dem gesuchten Signal aus dem Überwa¬ chungsraum, welches allenfalls noch von Störsignalen wie Sonneneinstrahlung oder Raumbeleuchtung überlagert sein kann.3 shows a further possibility for suppressing or compensating undesired reflections. In this variant, in which no third modulator 22 (FIG. 2) is required, the photodiode 5 forming the actual motion detector is connected in parallel with a second photodiode 5 'with preferably identical data with reversed polarity. The geometry of the arrangement is selected such that the one photodiode 5 is arranged at the focal point of the optics 8 (FIG. 1) and the second photodiode 5 'outside of it. As a result, the one photodiode 5 receives the radiation reflected from the interstitial space plus any interference reflections, whereas the second photodiode 5 'only receives the interference reflections. So the difference corresponds the photocurrents of the two photodiodes 5 and 5 'the signal sought from the monitoring room, which may at most be superimposed by interference signals such as solar radiation or room lighting.
Bei Verwendung von zwei gleichen Fotodioden 5, 5' werden hinsichtlich der gemeinsa¬ men Empfangssignale die Temperaturbeiwerte der Fotoempfindlichkeit gegenseitig kom¬ pensiert. Ausserdem bleiben alle diejenigen Einflüsse und potentiellen Störquellen ohne Wirkung, die sich auf beide Fotodioden auswirken. Einflüsse oder Störungen dieser Art sind insbesondere Exemplarstreuungen und Temperaturdriften der Infrarotleuchtdiode 4 sowie Exemplarstreuungen und zeitliche Änderungen der Reflexionskonstanten der rele¬ vanten mechanischen Bauteile, wie variierende Einfärbungen und Oberflächenstrukturen. Somit verbleibt dem Regler 19 und dem zweiten Modulator 21 nur noch die Kompensati¬ on der aus dem Überwachungsraum reflektierten Infrarotsignale, wogegen rund 95% der Gesamtreflexionen und Fotoströme durch die zweite Fotodiode 5' kompensiert werden. Dadurch kann die Einflussnahme des Reglers 19 auf rund ±5% reduziert werden, wo¬ durch die. Auflösung des Nutzsignals Un auf das etwa Zehnfache ansteigt, was für kon¬ stante Grenzen der Komparatoren 20, 20' einer rund zehnfachen Ansprechempfindlichkeit entspricht.If two identical photodiodes 5, 5 'are used, the temperature coefficients of the photosensitivity are mutually compensated for the common received signals. In addition, all those influences and potential sources of interference that have an effect on both photodiodes remain ineffective. Influences or disturbances of this type are in particular specimen scatter and temperature drifts of the infrared light-emitting diode 4, as well as specimen scatter and changes over time in the reflection constants of the relevant mechanical components, such as varying colors and surface structures. The controller 19 and the second modulator 21 thus only have the compensation of the infrared signals reflected from the monitoring room, whereas around 95% of the total reflections and photo currents are compensated by the second photo diode 5 '. As a result, the influence of the controller 19 can be reduced to around ± 5%, as a result of which. Resolution of the useful signal U n rises to about ten times, which corresponds to approximately ten times the sensitivity for constant limits of the comparators 20, 20 '.
Die erwähnte Überprüfung des Alarmsignals auf Plausibilität, die eine möglichst vollstän¬ dige Unterdrückung von Fehlalarmen ermöglichen soll, ist besonders bei sogenannten dualen Meldern, das sind Melder mit zwei nach verschiedenen Prinzipien arbeitenden Sensoren, sinnvoll. Bekannte derartige duale passive Infrarotbewegungsmelder kombinie¬ ren die passive Infrarotstrahlung mit Ultraschall oder mit Mikrowellen. Beim vorliegen¬ den aktiven Infrarotbewegungsmelder ist eine Kombination aktiv/passiv Infrarot denkbar. Eine derartige Kombination wäre den bekannten Kombinationen Infrarot Ultraschall und Infrarot/Mikrowellen nicht zuletzt deswegen vorzuziehen, weil sich die Infrarotstrahlung exakt gleich wie das sichtbare Licht verhält und daher mit den vom sichtbaren Licht her bekannten optischen Mitteln beherrschbar ist. Die letztgenannte vorteilhafte Eigenschaft der Infrarotstrahlung ist insbesondere beim Schutz von leicht durchdringbaren Flächen mit einem Infrarotvorhang, beispielsweise beim Schutz von Bildern oder Skulpturen in Galerien oder Museen, oder beim Schutz ganzer Fensterflächen, besonders wichtig.The aforementioned checking of the alarm signal for plausibility, which should enable false alarms to be suppressed as completely as possible, is particularly useful in the case of so-called dual detectors, ie detectors with two sensors operating according to different principles. Known dual passive infrared motion detectors of this type combine the passive infrared radiation with ultrasound or with microwaves. In the present active infrared motion detector, a combination of active / passive infrared is conceivable. Such a combination would be preferable to the known combinations of infrared ultrasound and infrared / microwaves not least because the infrared radiation behaves exactly the same as the visible light and can therefore be controlled with the optical means known from visible light. The latter advantageous property Infrared radiation is particularly important when protecting easily penetrable areas with an infrared curtain, for example when protecting pictures or sculptures in galleries or museums, or when protecting entire window areas.
Die in Fig. 4 dargestellte Auswerteschaltung 2' unterscheidet sich von der Auswerteschal¬ tung 2 von Fig. 2 im wesentlichen dadurch, dass ein anderer Regler verwendet, und dass das Reglersignal analog/digital gewandelt wird und somit für die Auswertung in digitali¬ sierter Form zur Verfügung steht. Darstellungsgemäss erfolgt bei diesem Ausfuhrungsbei- spiel die Steuerung des ersten Modulators 11 durch eine Programmsteuerstufe 26, die unter anderem einen Zähler 27 aufweist. Die Programmsteuerstufe 26 erhält ihren Takt von einem Taktgeber 13 und bestimmt die zeitliche Folge und die Länge der an die Infra¬ rotleuchtdiode 4 abgegebenen Signale. Mit dem Bezugszeichen 28 ist ein dem ersten Mo¬ dulator 11 zugeordneter Temperaturfühler zur Kompensation des Temperaturgangs des die Infrarotleuchtdiode 4 und die Fotodiode 5 enthaltenden Regelkreises bezeichnet.The evaluation circuit 2 'shown in FIG. 4 differs from the evaluation circuit 2 of FIG. 2 essentially in that another controller is used and in that the controller signal is converted analog / digital and thus for the evaluation in digitized form is available. As shown, in this exemplary embodiment the first modulator 11 is controlled by a program control stage 26, which has a counter 27, among other things. The program control stage 26 receives its clock from a clock generator 13 and determines the chronological sequence and the length of the signals emitted to the infrared light-emitting diode 4. The reference numeral 28 denotes a temperature sensor assigned to the first modulator 11 for compensating the temperature response of the control circuit containing the infrared light-emitting diode 4 and the photodiode 5.
Bis zu der den beiden Integratoren 17 und 17' nachgeschalteten Stufe 18, verläuft die Signalverarbeitung analog wie in der in Fig. 2 dargestellten Auswerteschaltung. Das Aus¬ gangssignal Un der Stufe 18, welches das Nutzsignal für die Signalauswertung bildet, wird einem Regler 29 zugeführt, der vorzugsweise ein sogenannter PID-Regler, also ein Regler mit Proportional-, Integral- und Differentialanteil ist, und gelangt von diesem in einen Spannungs/Pulsbreiten-Wandler 30. Dieser erzeugt aus dem analogen Ausgangssi¬ gnal des Reglers 29 ein impulsförmiges Signal, bei dem die Summe Puls plus Pulspause konstant und die Breite (Dauer) der Pulse proportional zum Signal des Reglers 29 ist. Das impulsförmige Signal des Wandlers 30 gelangt in die Programmsteuerstufe 26, deren Zähler 27 jeweils die Clocktakte pro Breite jedes der Impulse dieses Signals zählt. Wegen der Proportionalität zwischen Pulsbreite und Ausgangssignal des Reglers 29 stellt die An¬ zahl der vom Zähler 27 ermittelten Clocktakte pro Pulsbreite ein digitales Abbild des ana¬ logen Ausgangssignals des PID-Reglers 29 dar. Die am Ausgang des Spannungs/Pulsbrei-ten-Wandlers 30 erhältliche Pulsbreite wird nur in seltenen Fällen genau mit einem Vielfachen des Clocktakts übereinstimmen und kann bis zu ±ld (d = kleinste Informationseinheit) daneben liegen. Die konstante Länge Puls + Pulspause ist durch die Programmsteuerstufe 26 festgelegt und beträgt bei einer Clockfre- quenz von 4 MHz und bei Verwendung eines 12 Bit-Zählers ca. 1 ms. Damit stehen pro Sekunde l'OOO Resultate von maximal 12 bit, das sind 4'096 Informationen, mit einer Ge¬ nauigkeit von ±ld plus dem eventuellen Fehler des Wandlers 30 zur Verfügung.Up to the stage 18 downstream of the two integrators 17 and 17 ', the signal processing proceeds analogously to that in the evaluation circuit shown in FIG. 2. The output signal U n of stage 18, which forms the useful signal for the signal evaluation, is fed to a controller 29, which is preferably a so-called PID controller, that is to say a controller with a proportional, integral and differential component, and arrives from it a voltage / pulse width converter 30. This generates a pulse-shaped signal from the analog output signal of the controller 29, in which the sum of the pulse plus the pulse pause is constant and the width (duration) of the pulses is proportional to the signal of the controller 29. The pulse-shaped signal from the converter 30 reaches the program control stage 26, the counter 27 of which counts the clock clocks per width of each of the pulses of this signal. Because of the proportionality between the pulse width and the output signal of the controller 29, the number of clock cycles determined by the counter 27 per pulse width represents a digital image of the analog output signal of the PID controller 29. The pulse width obtainable at the output of the voltage / pulse width converter 30 will only rarely exactly match a multiple of the clock cycle and can be up to ± ld (d = smallest information unit) next to it. The constant pulse + pulse pause length is determined by the program control stage 26 and is approximately 1 ms at a clock frequency of 4 MHz and when using a 12-bit counter. This means that 1,000 results per second of a maximum of 12 bits, that is 4,096 pieces of information, are available with an accuracy of ± 1d plus the possible error of the converter 30.
Da der Differentialanteil des dem PID-Regler 29 zugeführten Signals zu einer gewissen Unstabilität des digitalen Signals führen kann, ist es vorteilhaft, diesen Signalanteil einem Differential-Regler 31 zuzuführen. Man kann dabei eine Aufteilung des Differentialan¬ teils auf die beiden Regler 29 und 31 vornehmen, oder den gesamten Differentialanteil auf den Differential-Regler 31 führen, oder man kann auch den Differential-Regler weg¬ lassen und nur den PID-Regler 29 verwenden. Massgebend dafür, welche dieser Lösun¬ gen man wählt, wird nicht zuletzt das Verhältnis zwischen Aufwand einerseits und Emp¬ findlichkeit und Zuverlässigkeit andererseits sein. Es sei aber betont, dass alle drei Lösun¬ gen voll funktionsfähig sind und zufriedenstellende Resultate liefern.Since the differential component of the signal supplied to the PID controller 29 can lead to a certain instability of the digital signal, it is advantageous to supply this signal component to a differential controller 31. The differential component can be divided between the two controllers 29 and 31, or the entire differential component can be routed to the differential controller 31, or the differential controller can be omitted and only the PID controller 29 can be used. Decisive for which of these solutions one chooses will be the ratio between effort on the one hand and sensitivity and reliability on the other hand. However, it should be emphasized that all three solutions are fully functional and deliver satisfactory results.
Die Werte der vom Zähler 27 ermittelten Clocktakte gelangen von der Programmsteuer¬ stufe 26 in einen Pulsbreiten/Spannungs-Wandler 32, in dem mit Bezug auf eine von der Referenzspannungsquelle 25 bezogene Referenzspannung eine dem jeweiligen Zähler¬ wert entsprechende Spannung gebildet wird, die den Kompensationsstrom Ik bestimmt. Hier ist ohne weiteres eine Genauigkeit von ±0.001% erreichbar, so dass also der Kom- pensationsstrom genau dem Stand des Zählers 27 entspricht. Der Ausgang des Differenti¬ al-Reglers 31 ist ebenfalls an den Pulsbreiten-/Spannungswandler 32 angeschlossen und fuhrt diesem die höherfrequenten Anteile des Nutzsignals Un zu. Der Ausgang des Wand¬ lers 32 ist mit dem einen Eingang des zweiten Modulators 21 (Fig. 2) verbunden, dessen zweiter Eingang mit der Programmsteuerstufe 26 und dessen Ausgang mit dem Eingang des Strom/Spannungswandlers 14 verbunden ist. Der zweite Modulator 21 überlagert dem Signal der Fotodiode 5 in Gegenphase den Kompensationsstrom Ik, wobei die zeitlichen Bedingungen für diese Überlagerung durch die Programmsteuerstufe 26 bestimmt sind. Der PID-Regler 29 verändert sein Ausgangs¬ signal und damit das Puls-/Pausen-Verhältnis derart, dass das Ausgangssignal der Stufe 18, also das Nutzsignal Un, gleich null wird. Somit entspricht der Stand des Zählers 27 bis auf die schon erwähnte mögliche Abweichung von ±ld dem Infrarotbild des über¬ wachten Raumes.The values of the clock clocks determined by the counter 27 pass from the program control stage 26 into a pulse width / voltage converter 32, in which a voltage corresponding to the respective counter value is generated with reference to a reference voltage obtained from the reference voltage source 25, which voltage corresponds to the compensation current Ik determined. An accuracy of ± 0.001% can easily be achieved here, so that the compensation current corresponds exactly to the level of the counter 27. The output of the differential controller 31 is also connected to the pulse width / voltage converter 32 and supplies it with the higher-frequency components of the useful signal U n . The output of converter 32 is connected to one input of second modulator 21 (FIG. 2), the second input of which is connected to program control stage 26 and the output of which is connected to the input of current / voltage converter 14. The second modulator 21 superimposes the compensation current Ik on the signal of the photodiode 5 in the opposite phase, the time conditions for this superimposition being determined by the program control stage 26. The PID controller 29 changes its output signal and thus the pulse / pause ratio in such a way that the output signal of the stage 18, that is to say the useful signal U n , becomes zero. The state of the counter 27 thus corresponds to the infrared deviation of the monitored room except for the already mentioned possible deviation of ± 1d.
Obwohl diese Abweichung in der Praxis ohne Bedeutung sein wird, kann man die Genau¬ igkeit durch Mittelwertbildung aus einer Vielzahl von Einzelwerten weiter erhöhen. Eine derartige Mittelwertbildung kann beispielsweise durch den Zähler 27 oder durch einen der Programmsteuerstufe 26 nachgeschalteten Mikroprozessor 33 erfolgen. Mit diesem kann das in der Programmsteuerstufe 26 in digitaler Form vorhandene Infrarotsignal dif¬ ferenzierter und intelligenter ausgewertet werden, was zu einer höheren Auflösung und damit zu einer verbesserten Detektionssicherheit und zu einer verbesserten Sicherheit vor Falschmeldungen führt. Ausserdem erleichtert der Mikroprozessor eine sinnvolle Kopp¬ lung des beschriebenen Messprinzips mit einem zweiten in einem sogenannten dualen Melder. Der Mikroprozessor 33, der das als Ergebnis der Auswertung vorliegende Alarm¬ signal an den Alarmausgang 10 abgibt, kann das Alarmsignal auf Plausibilität überprüfen und dadurch die Zentrale entlasten.Although this deviation will be irrelevant in practice, the accuracy can be further increased by averaging from a large number of individual values. Such averaging can be carried out, for example, by the counter 27 or by a microprocessor 33 connected downstream of the program control stage 26. With this, the infrared signal present in the program control stage 26 in digital form can be evaluated in a more differentiated and intelligent manner, which leads to a higher resolution and thus to an improved detection reliability and to an improved security against false reports. In addition, the microprocessor facilitates a sensible coupling of the measuring principle described with a second in a so-called dual detector. The microprocessor 33, which transmits the alarm signal present as a result of the evaluation to the alarm output 10, can check the alarm signal for plausibility and thereby relieve the control center.
Die beschriebene Auswerteelektronik mit ihrem mit einer Brückenschaltung vergleichba¬ ren Regelkreis, bei dem der Wert null des Nutzsignals die Ruhelage darstellt, bietet eine Reihe von Vorteilen:The evaluation electronics described, with their control circuit comparable to a bridge circuit, in which the value zero of the useful signal represents the rest position, offer a number of advantages:
- Durch die kompensierende Elektronik wird der Einfluss stark reflektierender Objekte nahe beim Melder so weit zurückgedrängt, dass die Hintergrundstrahlung nach wie vor erkennbar ist. Stark reflektierende Objekte werden wegkompensiert und die maximale Empfindlichkeit bleibt erhalten. Durch die kompensierende Elektronik wird die Verwendung einer gemeinsamen Sen¬ de/Empfangsoptik ermöglicht. Denn sendeseitig verursachte Reflexionen von Linsen, Spiegeln und/oder vom Infrarotfenster, die das Reflexionssignal eines möglichen Ob¬ jekts im Überwachungsraum in der Regel um Potenzen übertreffen, werden durch den Regelkreis unterdrückt.- Due to the compensating electronics, the influence of strongly reflecting objects near the detector is suppressed so far that the background radiation can still be seen. Highly reflective objects are compensated for and the maximum sensitivity is retained. The compensating electronics make it possible to use a common transmitting / receiving optic. This is because reflections from lenses, mirrors and / or from the infrared window caused on the transmission side, which as a rule exceed the reflection signal of a possible object in the monitoring room by potencies, are suppressed by the control loop.
Die Digitalisierung des Signals bietet die Möglichkeit, Absolutwerte der Infrarotstrah¬ lung zu erfassen und dadurch eine echte Präsenzdetektion zu ermöglichen, und sie ermöglicht den Einsatz eines Mikroprozessors mit all seinen Vorteilen.The digitization of the signal offers the possibility of acquiring absolute values of the infrared radiation and thereby enabling real presence detection, and it enables the use of a microprocessor with all of its advantages.
Die Erfassung der Anbsolutwerte der Infrarotstrahlung ermöglicht die Bestimmung von deren Vorzeichen, also die Feststellung, ob eine positive oder negative Änderung der Reflexion und damit eine Objektbewegung auf den Melder zu oder von diesem weg stattfindet.The detection of the absolute values of the infrared radiation enables the determination of their sign, that is to say whether there is a positive or negative change in the reflection and thus an object movement towards or away from the detector.
Der vorgeschlagene Analog/Digital-Wandler ist wesentlich preisgünstiger als jeder käufliche A/D-Wandler gleicher Auflösung. The proposed analog / digital converter is considerably cheaper than any commercially available A / D converter with the same resolution.

Claims

Patentansprüche Claims
1. Aktiver Infrarotmelder zur Detektion von Bewegungen in einem Überwachungs¬ raum, mit einem Sender zur Aussendung einer modulierten Infrarotstrahlung in den Über¬ wachungsraum, mit einem Empfänger für die aus dem Überwachungsraum reflektierte In¬ frarotstrahlung, und mit einer an den Empfänger angeschlossenen und Mittel zur Gewin¬ nung eines Nutzsignals enthaltenden Auswerteschaltung, dadurch gekennzeichnet, dass die Auswerteschaltung (2, 2') einen einerseits mit dem Nutzsignal (Un) beaufschlagten und andererseits mit dem Ausgang des Empfängers (5) verbundenen Regler (19, 29) zur Abgabe eines dem Empfängersignal (Ie) überlagerten Kompensationssignals (Ik) auf¬ weist, und dass das Kompensationssignal so gewählt ist dass eine Ausregelung des Nutz¬ signals auf den Wert null erfolgt.1. Active infrared detector for the detection of movements in a surveillance room, with a transmitter for sending modulated infrared radiation into the surveillance room, with a receiver for the infrared radiation reflected from the surveillance room, and with a means connected to the receiver for obtaining an evaluation signal containing a useful signal, characterized in that the evaluation circuit (2, 2 ') has a controller (19, 29) to which a useful signal (Un) is applied on the one hand and on the other hand connected to the output of the receiver (5) compensation signal (Ik) superimposed on the receiver signal (I e ), and that the compensation signal is selected such that the useful signal is adjusted to the value zero.
2. Infrarotmelder nach Anspruch 1, dadurch gekennzeichnet, dass für Sender (S, 4) und Empfänger (E, 5) eine gemeinsame Optik (8) vorgesehen ist.2. Infrared detector according to claim 1, characterized in that a common optical system (8) is provided for the transmitter (S, 4) and receiver (E, 5).
3. Infrarotmelder nach Anspruch 2, dadurch gekennzeichnet, dass die Auswerteschal¬ tung (2, 2') einen an eine Steuerstufe (12, 26) angeschlossenen ersten Modulator (11) zur impulsförmigen Modulation des vom Sender (S, 4) ausgesandten Signals, eine an die Steuerstufe angeschlossene gesteuerte Weiche (16), zwei der Weiche nachgeschaltete In¬ tegratoren (17, 17') und ein Mittel (18) zur Bildung der Differenz der Ausgangssignale der Integratoren aufweist.3. Infrared detector according to claim 2, characterized in that the evaluation circuit (2, 2 ') has a first modulator (11) connected to a control stage (12, 26) for the pulse-shaped modulation of the signal emitted by the transmitter (S, 4), has a controlled switch (16) connected to the control stage, two integrators (17, 17 ') connected downstream of the switch and a means (18) for forming the difference between the output signals of the integrators.
4. Infrarotmelder nach Anspruch 3, dadurch gekennzeichnet, dass das Empfangssi¬ gnal (Ue) den Integratoren (17, 17') über die Weiche (16) im Takt der Modulation des Sendesignals zugeführt ist, so dass in dem einen Integrator (17) eine Integration des Emp¬ fangssignals über die Impulsdauer und in dem anderen (17') über die Impulslücken er¬ folgt. 4. Infrared detector according to claim 3, characterized in that the received signal (U e ) is fed to the integrators (17, 17 ') via the switch (16) in time with the modulation of the transmitted signal, so that in one integrator (17th ) the reception signal is integrated over the pulse duration and in the other (17 ') over the pulse gaps.
5. Infrarotmelder nach Anspruch 4, dadurch gekennzeichnet dass dem Mittel (18) zur Differenzbildung mindestens ein Komparator (20, 20') nachgeschaltet ist in dem ein Vergleich des Nutzsignals (Un) mit mindestens einem Grenzwert erfolgt.5. Infrared detector according to claim 4, characterized in that the means (18) for difference formation is followed by at least one comparator (20, 20 ') in which the useful signal (Un) is compared with at least one limit value.
6. Infrarotmelder nach Anspruch 5, dadurch gekennzeichnet dass zwei Komparato¬ ren (20, 20') vorgesehen sind, in denen ein Vergleich des Nutzsignals (Un) mit einem oberen beziehungsweise einem unteren Grenzwert erfolgt.6. Infrared detector according to claim 5, characterized in that two Komparato¬ ren (20, 20 ') are provided, in which a comparison of the useful signal (Un) is carried out with an upper or a lower limit.
7. Infrarotmelder nach Anspruch 6, dadurch gekennzeichnet, dass zur Feststellung der Bewegungsrichtung eines im Überwachungsraum detektierten Objekts eine Untersu¬ chung des Ausgangssignals der beiden Komparatoren (20, 20') auf ihr Vorzeichen erfolgt.7. Infrared detector according to claim 6, characterized in that in order to determine the direction of movement of an object detected in the monitoring space, the sign of the output signal of the two comparators (20, 20 ') is examined.
8. Infrarotmelder nach einem der Ansprüche 3 bis 7, dadurch gekennzeichnet, dass dem Regler (19) ein zweiter, von der Steuerstufe (12) gesteuerter Modulator (21) nachge¬ schaltet ist, welcher dem Empfängersignal (Ie) das Kompensationssignal (1 im Gegen¬ takt überlagert.8. Infrared detector according to one of claims 3 to 7, characterized in that the controller (19) is followed by a second modulator (21) controlled by the control stage (12) which gives the receiver signal (I e ) the compensation signal (1 superimposed in the counter clock.
9. Infrarotmelder nach Anspruch 8, dadurch gekennzeichnet, dass der Regler (19) ein annähernd logarithmisches Regelverhalten aufweist.9. Infrared detector according to claim 8, characterized in that the controller (19) has an approximately logarithmic control behavior.
10. Infrarotmelder nach Anspruch 8, gekennzeichnet durch einen dritten, vorzugsweise justierbar ausgebildeten, Modulator (22) zur Erzeugung eines zusätzlichen Kompensati¬ onssignals (I ') zur Kompensation von durch die Optik (8) oder durch ein infrarotdurch¬ lässiges Fenster (7) des Melders (1) verursachten Reflexionen.10. Infrared detector according to claim 8, characterized by a third, preferably adjustable, modulator (22) for generating an additional compensation signal (I ') for compensation by the optics (8) or by an infrared-permeable window (7) of the detector (1) caused reflections.
11. Infrarotmelder nach Anspruch 8, dadurch gekennzeichnet, dass eine zu der den Empfänger (E) bildenden ersten Diode (5) mit umgekehrter Polarität parallelgeschaltete zweite Diode (5') mit vorzugsweise identischen Daten vorgesehen ist, und dass die Diffe¬ renz der Fotoströme der beiden Dioden das Empfängersignal (Ie) bildet. 11. Infrared detector according to claim 8, characterized in that a second diode (5 ') connected in parallel with the first diode (5) forming the receiver (E) with reversed polarity is provided with preferably identical data, and that the difference in the photo currents of the two diodes forms the receiver signal (I e ).
12. Infrarotmelder nach Anspruch 11, dadurch gekennzeichnet, dass die erste Diode (5) von der aus dem Überwachungsraum reflektierten Infrarotstrahlung und mit der gege¬ benenfalls von der Optik (8) oder von einem infrarotdurchlässigen Fenster (7) des Mel¬ ders (1) reflektierten Störstrahlung, und dass die zweite Diode (51) nur von der genannten Störstrahlung beaufschlagt ist.12. Infrared detector according to claim 11, characterized in that the first diode (5) from the infrared radiation reflected from the monitoring room and, if appropriate, from the optics (8) or from an infrared-transparent window (7) of the detector (1 ) reflected interference, and that the second diode (5 1 ) is only exposed to the said interference.
13. Infrarotmelder nach Anspruch 12, dadurch gekennzeichnet dass die erste Diode (5) im Brennpunkt der gemeinsamen Optik (8) und die zweite Diode (5') ausserhalb von diesem angeordnet ist.13. Infrared detector according to claim 12, characterized in that the first diode (5) at the focal point of the common optics (8) and the second diode (5 ') is arranged outside of this.
14. Infrarotmelder nach einem der Ansprüche 1 bis 4, dadurch gekennzeichnet dass die Auswerteschaltung (2') einen dem Regler (29) nachgeschalteten Analog/Digital- Wandler (26, 30) aufweist an dessen einem Ausgang das digitalisierte Reglersignal er¬ hältlich und dessen anderer Ausgang mit einem Digital/Analog- Wandler (25, 32) zur Er¬ zeugung einer dem jeweiligen digitalen Signalwert entsprechenden Spannung verbunden ist und dass diese Spannung zur Erzeugung des Kompensationssignals (Ik) verwendet wird.14. Infrared detector according to one of Claims 1 to 4, characterized in that the evaluation circuit (2 ') has an analog / digital converter (26, 30) connected downstream of the controller (29) and the digitized controller signal is available at one of its outputs and the latter another output is connected to a digital / analog converter (25, 32) for generating a voltage corresponding to the respective digital signal value and that this voltage is used to generate the compensation signal (Ik).
15. Infrarotmelder nach Anspruch 14, dadurch gekennzeichnet dass der eine Ausgang des Analog/Digital-Wandlers (26, 30) mit einem Mikroprozessor (33) verbunden ist.15. Infrared detector according to claim 14, characterized in that the one output of the analog / digital converter (26, 30) is connected to a microprocessor (33).
16. Infrarotmelder nach Anspruch 15, dadurch gekennzeichnet dass der mit dem Nutzsignal Un) beaufschlagte Regler (29) durch einen PID-Regler gebildet ist.16. Infrared detector according to claim 15, characterized in that the controller (29) acted upon by the useful signal Un) is formed by a PID controller.
17. Infrarotmelder nach einem der Ansprüche 14 bis 16, dadurch gekennzeichnet, dass der Analog/Digital-Wandler durch einen Signal wandler (30) zur Umwandlung der Reg¬ lersignals in ein impulsförmiges Signal und durch eine dem Signalwandler nachgeschalte¬ te Stufe (26) *rur Gewinnung von der Grosse der einzelnen Impulse entsprechenden Zah¬ lenwerten gebildet ist. 17. Infrared detector according to one of claims 14 to 16, characterized in that the analog / digital converter by a signal converter (30) for converting the controller signal into a pulse-shaped signal and by a stage (26) downstream of the signal converter. * For the extraction of the values corresponding to the size of the individual pulses.
18. Infrarotwandler nach Anspruch 17, dadurch gekennzeichnet dass der Signalwand¬ ler (30) durch einen Spannungs/Pulsbreiten-Wandler gebildet ist, welcher aus dem analo¬ gen Ausgangssignal des Reglers ein impulsförmiges Signal erzeugt bei dem die Dauer Puls plus Pulspause konstant und die Breite der Pules proportional zum Signal des Reg¬ lers ist.18. Infrared converter according to claim 17, characterized in that the Signalwand¬ ler (30) is formed by a voltage / pulse width converter which generates a pulse-shaped signal from the analog output signal of the controller in which the duration pulse plus pulse pause constant and Width of the pulses is proportional to the signal of the controller.
19. Infrarotmelder nach Anspruch 18, dadurch gekennzeichnet dass die dem Signal¬ wandler (30) nachgeschaltete Stufe (26) einen Zähler (27) und einen Taktgeber (13) auf¬ weist, wobei durch den Zähler eine Zählung der der Breite der einzelnen Signalimpulse entsprechenden Taktimpulse erfolgt.19. Infrared detector according to Claim 18, characterized in that the stage (26) connected downstream of the signal converter (30) has a counter (27) and a clock generator (13), the counter counting the width of the individual signal pulses corresponding clock pulses.
20. Infrarotmelder nach Anspruch 19, dadurch gekennzeichnet, dass der Digital Ana- log-Wandler durch einen mit einer Referenzspannungsquelle (25) verbundenen Pulsbrei¬ ten/Spannungs-Wandler (32) gebildet ist, in welchem eine Umwandlung des jeweiligen Wertes des Zählers (27) in eine Spannung erfolgt.20. Infrared detector according to claim 19, characterized in that the digital analog converter is formed by a pulse width / voltage converter (32) connected to a reference voltage source (25), in which a conversion of the respective value of the counter ( 27) in a voltage.
21. Infrarotmelder nach Anspruch 20, dadurch gekennzeichnet, dass das Nutzsignal (U ) parallel zum PID-Regler (29) einem Differential-Regler (31) für den Differentialan¬ teil des Signals zugeführt, und dass der Ausgang des Differential-Reglers mit dem Puls¬ breiten/Spannungs-Wandler (32) verbunden ist. 21. Infrared detector according to claim 20, characterized in that the useful signal (U) parallel to the PID controller (29) is fed to a differential controller (31) for the differential part of the signal, and that the output of the differential controller with the Pulse width / voltage converter (32) is connected.
EP95917879A 1994-05-30 1995-05-19 Active ir intrusion detector Expired - Lifetime EP0711442B1 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
EP95917879A EP0711442B1 (en) 1994-05-30 1995-05-19 Active ir intrusion detector

Applications Claiming Priority (7)

Application Number Priority Date Filing Date Title
EP94108289 1994-05-30
EP94108289 1994-05-30
CH907/95 1995-03-31
CH90795 1995-03-31
CH90795 1995-03-31
PCT/CH1995/000112 WO1995033248A1 (en) 1994-05-30 1995-05-19 Active ir intrusion detector
EP95917879A EP0711442B1 (en) 1994-05-30 1995-05-19 Active ir intrusion detector

Publications (2)

Publication Number Publication Date
EP0711442A1 true EP0711442A1 (en) 1996-05-15
EP0711442B1 EP0711442B1 (en) 1999-09-22

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US (1) US5675150A (en)
EP (1) EP0711442B1 (en)
JP (1) JPH09501253A (en)
CN (1) CN1088225C (en)
CA (1) CA2166389C (en)
DE (1) DE59506883D1 (en)
IL (1) IL113653A (en)
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CN1129042A (en) 1996-08-14
CA2166389A1 (en) 1995-12-07
DE59506883D1 (en) 1999-10-28
US5675150A (en) 1997-10-07
WO1995033248A1 (en) 1995-12-07
IL113653A0 (en) 1995-08-31
CN1088225C (en) 2002-07-24
IL113653A (en) 1998-10-30
JPH09501253A (en) 1997-02-04
CA2166389C (en) 2004-07-13
EP0711442B1 (en) 1999-09-22

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