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EP0050751B1 - Optical arrangement for an infrared intrusion detector - Google Patents

Optical arrangement for an infrared intrusion detector Download PDF

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Publication number
EP0050751B1
EP0050751B1 EP81107844A EP81107844A EP0050751B1 EP 0050751 B1 EP0050751 B1 EP 0050751B1 EP 81107844 A EP81107844 A EP 81107844A EP 81107844 A EP81107844 A EP 81107844A EP 0050751 B1 EP0050751 B1 EP 0050751B1
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EP
European Patent Office
Prior art keywords
radiation
optical arrangement
reflectors
infrared
intrusion detector
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Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired
Application number
EP81107844A
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German (de)
French (fr)
Other versions
EP0050751A1 (en
Inventor
Peter Wägli
Alois Zetting
Gustav Pfister
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Cerberus AG
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Cerberus AG
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Publication date
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Priority to AT81107844T priority Critical patent/ATE24786T1/en
Publication of EP0050751A1 publication Critical patent/EP0050751A1/en
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Publication of EP0050751B1 publication Critical patent/EP0050751B1/en
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    • G—PHYSICS
    • G08—SIGNALLING
    • G08B—SIGNALLING OR CALLING SYSTEMS; ORDER TELEGRAPHS; ALARM SYSTEMS
    • G08B13/00—Burglar, theft or intruder alarms
    • G08B13/18—Actuation by interference with heat, light, or radiation of shorter wavelength; Actuation by intruding sources of heat, light, or radiation of shorter wavelength
    • G08B13/189—Actuation by interference with heat, light, or radiation of shorter wavelength; Actuation by intruding sources of heat, light, or radiation of shorter wavelength using passive radiation detection systems
    • G08B13/19—Actuation by interference with heat, light, or radiation of shorter wavelength; Actuation by intruding sources of heat, light, or radiation of shorter wavelength using passive radiation detection systems using infrared-radiation detection systems
    • G08B13/193—Actuation by interference with heat, light, or radiation of shorter wavelength; Actuation by intruding sources of heat, light, or radiation of shorter wavelength using passive radiation detection systems using infrared-radiation detection systems using focusing means
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10S250/00—Radiant energy
    • Y10S250/01—Passive intrusion detectors

Definitions

  • the invention relates to an optical arrangement for an infrared intrusion detector.
  • Such arrangements pick up the infrared radiation emanating from a person in the monitored area and direct it to a sensor element. If the monitored area is divided into several separate reception areas with dark fields in between, each movement of a person causes a modulation of the infrared radiation received by the sensor element, which can be evaluated by means of a known upgrading circuit to indicate an intruder and to give an alarm signal.
  • US-A-4 052 616 shows an arrangement with a hemispherical reflector or a Fresnel lens for all reception areas and light guides which give the infrared radiation to a sensor.
  • the number of light guides is limited by the size of the sensor surface, so that the amount of radiation incident on the sensor is insufficient. Furthermore, the attachment of the ends of the light guides on the focal surface and on the sensor surface is difficult.
  • US-A-3 702 937 describes a motion detector which, instead of reflectors, uses a lens arrangement which divides the image of the monitored area into two parts and places them on two photocells which are integrated in a bridge circuit. If the monitored area is illuminated differently, the electrical bridge circuit is imbalanced and an alarm is generated. The amount of radiation reaching a photocell is low.
  • the object of the invention is to eliminate the essential disadvantage of the prior art, which, despite the different lens and reflector arrangement, is the low absorption of the radiation amount, in order to increase the sensitivity of the intrusion detector.
  • the intrusion detector should have small spatial dimensions so that it can be attached inconspicuously at its place of use.
  • Another purpose of the invention is the simple construction of the optical arrangement.
  • a collecting lens 1 is provided as the first focusing means, which is designed as a Fresnel lens.
  • Such stepped lenses can be easily produced from a suitable transparent material by pressing or casting. It is particularly expedient to choose a material, for example a suitable plastic material which is preferably transparent in the region of long-wave infrared radiation, for example polyethylene, or As 2 S 3 , Se, or As / Se glasses, these glasses also can be evaporated as a filter on the polyethylene lens.
  • a material for example a suitable plastic material which is preferably transparent in the region of long-wave infrared radiation, for example polyethylene, or As 2 S 3 , Se, or As / Se glasses, these glasses also can be evaporated as a filter on the polyethylene lens.
  • a plurality of individual reflectors 2, 3,... 6 are arranged behind this Fresnel lens in the direction of irradiation. These reflectors can be concave or convex spherical, paraboloid or ellipsoid segments or be designed as a plane mirror inclined to one another.
  • a detector element 7 is provided in the center of the Fresnel lens 1, the sensitivity of which is matched to the infrared radiation to be received, for example lithium tantalate (LiTaO a ).
  • the focal length of the Fresnel lens 1, the curvature, the alignment and the spacing of the reflectors 2, 3,... 6 can be chosen so that the infrared radiation arriving from certain desired directions is imaged as well as possible.
  • the individual reception areas become reception directions with a relatively small opening angle, which depends on the accuracy of the optical components and their adjustment, as well as on the dimensions of the sensor element. If a different shape of reception areas is desired, for example a rectangular or strip shape, the reflectors can be aspherical.
  • incident infrared radiation from the first focusing means i.e. is recorded by the Fresnel lens 1 with its full area and is only then fed to the individual mirror segments assigned to the different reception areas.
  • Each mirror segment 2, 3,... 6 receives radiation from the full surface of the Fresnel lens 1 and then bundles this radiation onto the sensor element 7.
  • the sensitivity of an infrared intrusion detector equipped with such an arrangement is therefore considerably increased.
  • the dimensions of the reflectors do not play a decisive role, so that small device dimensions are possible even with a large number of reception areas.
  • Figure 2 shows a similar arrangement, which differs from the first embodiment in that the sensor element 7 peripherally, i. H. is arranged on the edge of the Fresnel lens 1.
  • the entire opening of the Fresnel lens is thus available for receiving infrared radiation and there are no losses through the sensor element.
  • FIG. 3 shows an infrared intrusion detector with a housing 10 which has a front plate 11 and a rear side 12.
  • the front plate 11 carries a Fresnel lens 1 and below this a sensor element 7 on the edge, which is connected to an integrated evaluation circuit 8, which can be designed, for example, in accordance with US Pat. No. 4,179,691 or US Pat. No. 4,166,955.
  • the output signal of this evaluation circuit 8 is taken from the output terminals 9.
  • the rear side 12 carries a facet mirror 13, the individual facets of which correspond to the reflector 2, 3,... 6.
  • the formation and alignment of the individual facets is such that, in cooperation with the Fresnel lens 1, a bundle of many reception directions or areas with a small opening angle is created.
  • a plurality of sensor elements (7, 7 ', 7 ") arranged next to one another can be provided.
  • Each element receives radiation from a plurality of reception areas.
  • the number of possible reception areas can thus be multiplied according to the number of sensor elements , with no significant loss in intensity or sensitivity, since each sensor element receives a large part of the radiation from the common bundling means.
  • the individual reception areas are each split into a bundle of several reception areas lying on one level, making it easy to create a number of radiation curtains to be passed by an intruder.
  • FIG. 4 shows a particularly flat embodiment of an infrared intrusion detector, in which the entire front side 11 is occupied by a segment of a Fresnel lens 1, in the center of which the sensor element 7 is attached. Individual reflectors 2, 3,... 6 are provided in a row on the rear side 12.
  • the evaluation circuit 8 is attached to the base plate 14. With this arrangement, a fan of reception areas lying on one level or a protective curtain can be formed. Thanks to its flat design, the detector can be arranged inconspicuously in a narrow gap, the front surface 11 being optimally used for receiving infrared radiation from the reception areas.
  • one or more prisms can be provided in front of or behind parts of the converging lens 1, through which the individual reception beams can each be split into a plurality of beams.
  • the number of radiation receiving areas can be multiplied if a certain intensity weakening of the individual areas can be accepted.
  • prisms 15, 15 ' can be arranged in front of both sides of the Fresnel lens, for example. These have the effect that the radiation impinging on the prisms is deflected by a certain angle, while the radiation impinging directly on the lens remains unaffected. Each reception area is therefore split into three separate areas.
  • the prism element can also be combined with and integrated into the converging lens in that it is designed as a multi-zone lens with zones of different optical axes.
  • the sides of the Fresnel lens 1 has on its front or back the shape of wedges 16, 16 'which replace the prisms 15, 15' and show the same optical effect.
  • Such an optical element is particularly easy to manufacture and requires no special adjustment.
  • the infrared intrusion detector shown has an optimal sensitivity and, moreover, has a particularly simple and interference-free construction. It is particularly suitable for applications where an infrared protective curtain with closely spaced reception areas is desired.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Burglar Alarm Systems (AREA)
  • Photometry And Measurement Of Optical Pulse Characteristics (AREA)
  • Geophysics And Detection Of Objects (AREA)
  • Vessels And Coating Films For Discharge Lamps (AREA)

Abstract

The optical arrangement for an infrared intrusion detector containing a plurality of separate radiation receiving regions or fields of view is provided with a first focussing optic or optical system, for instance a Fresnel lense which receives with its entire surface or area the infrared radiation which arrives from all of the receiving regions and delivers such received radiation to a multiplicity of further focussing means, for instance to individual reflectors. These reflectors are correlated in each instance to one of the receiving regions or fields of view and focus the radiation arriving from such receiving region upon a sensor element. In this way there is attained the beneficial result of optimum utilization of the infrared radiation which is available and the sensitivity of the infrared intrusion detector can be increased. The dimensions of the optical arrangement and the intrusion detector can be maintained small and relatively imperceptible.

Description

Die Erfindung betrifft eine optische Anordnung für einen Infrarot-Einbruchdetektor.The invention relates to an optical arrangement for an infrared intrusion detector.

Solche Anordnungen nehmen die von einer Person im überwachten Bereich ausgehende Infrarot- Strahlung auf und leiten sie auf ein Sensorelement. Wenn der überwachte Bereich in mehrere getrennte Empfangsbereiche mit dazwischenliegenden Dunkelfeldern aufgeteilt ist, so bewirkt jede Bewegung einer Person eine Modulation der vom Sensorelement empfangenen Infrarot-Strahlung, welche mittels einer bekannten Aufwerteschaltung zur Anzeige eines Eindringlings und zur Alarmsignalgabe ausgewertet werden kann.Such arrangements pick up the infrared radiation emanating from a person in the monitored area and direct it to a sensor element. If the monitored area is divided into several separate reception areas with dark fields in between, each movement of a person causes a modulation of the infrared radiation received by the sensor element, which can be evaluated by means of a known upgrading circuit to indicate an intruder and to give an alarm signal.

Zur Schaffung der erforderlichen getrennten Empfangsbereiche ist es beispielsweise aus US 3 703 718, US 4 058 726 oder US 4 081 680 bekannt, mehrere Reflektoren vorzusehen, die in verschiedene Richtungen ausgerichtet sind und die die aus verschiedenen Empfangsbereichen eintreffende Strahlung auf das gleiche Sensorelement fokussieren. Dabei ist jeder Reflektor einem anderen Empfangsbereich zugeordnet und bündelt nur Strahlung aus diesem Empfangsbereich auf das Sensorelement. Nachteilig ist hierbei, dass die gesamte Empfangsfläche in viele kleine Segmente aufgeteilt ist. Aus den einzelnen Empfangsbereichen wird daher jeweils nur eine kleine Strahlungsmenge aufgenommen, so dass die Empfindlichkeit solcher Infrarot-Einbruchdetektoren häufig unzureichend ist, besonders wenn viele Empfangsbereiche vorgesehen sind.To create the required separate reception areas, it is known, for example from US Pat. No. 3,703,718, US Pat. No. 4,058,726 or US Pat. No. 4,081,680, to provide a plurality of reflectors which are oriented in different directions and which focus the radiation arriving from different reception areas onto the same sensor element. Each reflector is assigned to a different reception area and only bundles radiation from this reception area onto the sensor element. The disadvantage here is that the entire reception area is divided into many small segments. Therefore, only a small amount of radiation is picked up from the individual reception areas, so that the sensitivity of such infrared intrusion detectors is often inadequate, especially if many reception areas are provided.

Dieser Nachteil lässt sich zwar mit den in US 3 760 399, US 3 829 693 oder US 3958118 beschriebenen Anordnungen vermeiden, bei denen ein einziger Reflektor für alle Empfangsbereiche vorgesehen ist und die Aufteilung in die einzelnen Bereiche mittels mehrerer nebeneinander angeordneter Sensorelemente erfolgt. Damit steht zwar für alle Empfangsbereiche eine gemeinsame, relativ grosse Reflektoroberfläche zur Verfügung, jedoch erfordern die vielen Sensorelemente eine komplizierte und störanfällige Schaltung, wobei zudem die Zahl der möglichen Sensorelemente und damit der Empfangsbereiche stark eingeschränkt ist.This disadvantage can be avoided with the arrangements described in US Pat. No. 3,760,399, US Pat. No. 3,829,693 or US Pat. No. 3958118, in which a single reflector is provided for all reception areas and the division into the individual areas takes place by means of a plurality of sensor elements arranged next to one another. This means that a common, relatively large reflector surface is available for all reception areas, but the many sensor elements require a complicated and fault-prone circuit, and the number of possible sensor elements and thus the reception areas is also greatly restricted.

Aus der GB-A 2 012 045 und der EP-A 0 014 825 sind bereits Anordnungen bekannt geworden, bei denen die Bündelung der Infrarot-Strahlung auf ein gemeinsames Sensorelement durch mehrfache Reflexion erfolgt. Dabei erfolgt die erste Reflexion jedoch wiederum an einzelnen Spiegelsegmenten, von denen jedes einem anderen Empfangsbereich zugeordnet ist. Solche Anordnungen weisen daher ebenfalls den Nachteil auf, dass aus den einzelnen Empfangsbereichen nur eine geringe Strahlungsmenge aufgenommen wird und die Empfindlichkeit daher häufig unzureichend ist. Um trotzdem eine gute Empfindlichkeit zu erreichen, war es daher bei solchen vorbekannten Infrarot-Einbruchdetektoren erforderlich, relativ grosse Spiegelsegmente zu verwenden, so dass die Abmessungen solcher Detektoren verhältnismässig gross gewählt werden mussten, so dass eine unauffällige Anbringung, wie sie bei Einbruchschutzeinrichtungen häufig erwünscht und erforderlich ist, kaum möglich war.Arrangements are already known from GB-A 2 012 045 and EP-A 0 014 825 in which the infrared radiation is focused on a common sensor element by multiple reflections. In this case, however, the first reflection again takes place at individual mirror segments, each of which is assigned to a different reception area. Such arrangements therefore also have the disadvantage that only a small amount of radiation is picked up from the individual reception areas and the sensitivity is therefore often inadequate. In order to achieve good sensitivity, it was therefore necessary to use relatively large mirror segments in such known infrared intrusion detectors, so that the dimensions of such detectors had to be selected to be relatively large, so that an inconspicuous attachment, as is often desired and desirable in intrusion protection devices is required was hardly possible.

Die US-A-4 052 616 zeigt eine Anordnung mit einem halbkugelförmigen Reflektor bzw. einer Fresnel-Linse für sämtliche Empfangsbereiche sowie Lichtleiter, welche die Infrarot-Strahlung auf einen Sensor geben. Die Anzahl der Lichtleiter ist durch die Grösse der Sensorfläche beschränkt, sodass die auf den Sensor auftreffende Strahlungsmenge unzureichend ist. Ferner ist das Befestigen der Enden der Lichtleiter auf der Brennfläche und auf der Sensorfläche schwierig.US-A-4 052 616 shows an arrangement with a hemispherical reflector or a Fresnel lens for all reception areas and light guides which give the infrared radiation to a sensor. The number of light guides is limited by the size of the sensor surface, so that the amount of radiation incident on the sensor is insufficient. Furthermore, the attachment of the ends of the light guides on the focal surface and on the sensor surface is difficult.

Die US-A-3 702 937 beschreibt einen Bewegungsmelder, der anstelle von Reflektoren eine Linsenanordnung benutzt, die das Bild des überwachten Gebietes in zwei Teile zerlegt und auf zwei Fotozellen gibt, welche in eine Brückenschaltung integriert sind. Bei unterschiedlicher Beleuchtung des überwachten Gebietes wird die elektrische Brückenschaltung ins Ungleichgewicht gebracht, und ein Alarm erzeugt. Die auf eine Fotozelle gelangende Strahlungsmenge ist gering.US-A-3 702 937 describes a motion detector which, instead of reflectors, uses a lens arrangement which divides the image of the monitored area into two parts and places them on two photocells which are integrated in a bridge circuit. If the monitored area is illuminated differently, the electrical bridge circuit is imbalanced and an alarm is generated. The amount of radiation reaching a photocell is low.

Die Erfindung hat die Aufgabe, den wesentlichen Nachteil des Standes der Technik, der trotz verschiedener Linsen- und Reflektoranordnung in der geringen Aufnahme der Strahlungsmenge liegt, zu beseitigen, um die Empfindlichkeit des Einbruch-Detektors zu erhöhen. Ferner soll der Einbruch-Detektor kleine räumliche Abmessungen haben, damit er unauffällig an seinem Einsatzort angebracht werden kann. Ein weiterer Zweck der Erfindung liegt in der einfachen Konstruktion der optischen Anordnung.The object of the invention is to eliminate the essential disadvantage of the prior art, which, despite the different lens and reflector arrangement, is the low absorption of the radiation amount, in order to increase the sensitivity of the intrusion detector. In addition, the intrusion detector should have small spatial dimensions so that it can be attached inconspicuously at its place of use. Another purpose of the invention is the simple construction of the optical arrangement.

Die Aufgabe der Erfindung wird durch die Merkmale des Patentanspruchs 1 gelöst.The object of the invention is achieved by the features of patent claim 1.

Die Erfindung wird an Hand der in den Figuren dargestellten Ausführungsbeispiele beschrieben.

  • Figur 1 zeigt eine erste optische Anordnung mit zentral angebrachtem Sensorelement.
  • Figur 2 zeigt eine zweite optische Anordnung mit peripher angebrachtem Sensorelement.
  • Figur 3 zeigt eine weitere optische Anordnung mit peripher angebrachtem Sensorelement.
  • Figur 4 zeigt einen Infrarot-Einbruchdetektor mit linearer Reflektoranordnung.
The invention is described on the basis of the exemplary embodiments shown in the figures.
  • Figure 1 shows a first optical arrangement with a centrally attached sensor element.
  • Figure 2 shows a second optical arrangement with a peripherally attached sensor element.
  • FIG. 3 shows a further optical arrangement with a peripherally attached sensor element.
  • FIG. 4 shows an infrared intrusion detector with a linear reflector arrangement.

Bei der in Figur 1 dargestellten optischen Anordnung ist als erstes Bündelungsmittel eine Sammellinse 1 vorgesehen, die als Fresnel-Linse ausgebildet ist.In the optical arrangement shown in FIG. 1, a collecting lens 1 is provided as the first focusing means, which is designed as a Fresnel lens.

Solche Stufenlinsen können auf einfache Weise aus einem geeigneten Transparent-Material durch Pressen oder Giessen hergestellt werden. Besonders zweckmässig ist es dazu ein Material zu wählen, z.B. ein geeignetes Plastikmaterial, welches vorzugsweise im Bereich der langwelligen Infrarot-Strahlung durchlässig ist, beispielsweise Polyäthylen, oder As2S3 , Se-, oder As/Se-Gläser, wobei diese Gläser auch als Filter auf der Polyäthylen-Linse aufgedampft sein können.Such stepped lenses can be easily produced from a suitable transparent material by pressing or casting. It is particularly expedient to choose a material, for example a suitable plastic material which is preferably transparent in the region of long-wave infrared radiation, for example polyethylene, or As 2 S 3 , Se, or As / Se glasses, these glasses also can be evaporated as a filter on the polyethylene lens.

In Einstrahlungsrichtung hinter dieser Fresnel-Linse ist eine Mehrzahl von einzelnen Reflektoren 2, 3, ... 6 angeordnet. Diese Reflektoren können als konkave oder konvexe Kugel-, Paraboloid-oder Ellipsoid-Segmente oder als gegeneinander geneigte Planspiegel ausgebildet sein. Im Zentrum der Fresnel-Linse 1 ist ein Detektorelement 7 vorgesehen, dessen Empfindlichkeit auf die zu empfangende Infrarot-Strahlung abgestimmt ist, beispielsweise Lithiumtantalat (LiTaOa). Polyvinyldifluorid (PVF2), Bleizirkonattitanat (PZT) oder ein anderer geeigneter pyroelektrischer Sensor.A plurality of individual reflectors 2, 3,... 6 are arranged behind this Fresnel lens in the direction of irradiation. These reflectors can be concave or convex spherical, paraboloid or ellipsoid segments or be designed as a plane mirror inclined to one another. A detector element 7 is provided in the center of the Fresnel lens 1, the sensitivity of which is matched to the infrared radiation to be received, for example lithium tantalate (LiTaO a ). Polyvinyl difluoride (PVF 2 ), lead zirconate titanate (PZT) or another suitable pyroelectric sensor.

Die Brennweite der Fresnel-Linse 1, die Krümmung, die Ausrichtung und der Abstand der Reflektoren 2, 3, ... 6 können dabei so gewählt sein, dass eine möglichst gute Abbildung der aus bestimmten gewünschten Richtungen eintreffenden Infrarot-Strahlung stattfindet. Die einzelnen Empfangsbereiche werden hierbei zu Empfangsrichtungen mit relativ kleinem Öffnungswinkel, der von der Genauigkeit der optischen Bauteile und deren Justierung, sowie von den Abmessungen des Sensorelementes abhängt. Falls eine andere Form von Empfangsbereichen gewünscht ist, beispielsweise Rechteck- oder Streifenform, können die Reflektoren asphärisch ausgebildet sein.The focal length of the Fresnel lens 1, the curvature, the alignment and the spacing of the reflectors 2, 3,... 6 can be chosen so that the infrared radiation arriving from certain desired directions is imaged as well as possible. The individual reception areas become reception directions with a relatively small opening angle, which depends on the accuracy of the optical components and their adjustment, as well as on the dimensions of the sensor element. If a different shape of reception areas is desired, for example a rectangular or strip shape, the reflectors can be aspherical.

Mit der beschriebenen optischen Anordnung wird erreicht, dass einfallende Infrarot-Strahlung vom ersten Bündelungsmittel, d.h. von der Fresnel-Linse 1 mit ihrer vollen Fläche aufgenommen wird und erst danach den einzelnen, den verschiedenen Empfangsbereichen zugeordneten Spiegel-Segmenten zugeleitet wird. Jedes Spiegel-Segment 2, 3, ... 6 erhält dabei Strahlung von der vollen Fläche der Fresnel-Linse 1 und bündelt diese Strahlung dann auf das Sensorelement 7. Damit wird also die grösstmögliche Menge einfallender Infrarot-Strahlung erfasst und detektiert. Die Empfindlichkeit eines mit einer solchen Anordnung ausgerüsteten Infrarot-Einbruchdetektors ist daher erheblich vergrössert. Dabei spielen die Abmessungen der Reflektoren keine entscheidende Rolle, so dass auch bei einer Vielzahl von Empfangsbereichen kleine Geräteabmessungen möglich sind.With the optical arrangement described it is achieved that incident infrared radiation from the first focusing means, i.e. is recorded by the Fresnel lens 1 with its full area and is only then fed to the individual mirror segments assigned to the different reception areas. Each mirror segment 2, 3,... 6 receives radiation from the full surface of the Fresnel lens 1 and then bundles this radiation onto the sensor element 7. Thus, the greatest possible amount of incident infrared radiation is detected and detected. The sensitivity of an infrared intrusion detector equipped with such an arrangement is therefore considerably increased. The dimensions of the reflectors do not play a decisive role, so that small device dimensions are possible even with a large number of reception areas.

Figur 2 zeigt eine ähnliche Anordnung, die sich von der ersten Ausführung dadurch unterscheidet, dass das Sensorelement 7 peripher, d. h. am Rande der Fresnel-Linse 1 angeordnet ist. Damit steht die gesamte Öffnung der Fresnel-Linse zur Aufnahme von lnfrarot-Strahlung zur Verfügung und durch das Sensorelement entstehen keine Verluste. In diesem Beispiel ist es zweckmässig, die Reflektoren 2, und 4 nur schwach gekrümmt oder plan auszubilden, um Abbildungsfehler infolge schiefen Strahlungseinfalles möglichst klein zu halten.Figure 2 shows a similar arrangement, which differs from the first embodiment in that the sensor element 7 peripherally, i. H. is arranged on the edge of the Fresnel lens 1. The entire opening of the Fresnel lens is thus available for receiving infrared radiation and there are no losses through the sensor element. In this example, it is expedient to design the reflectors 2 and 4 to be only slightly curved or flat in order to keep imaging errors due to oblique radiation incidence as small as possible.

Figur 3 zeigt einen Infrarot-Einbruchdetektor mit einem Gehäuse 10, das eine Frontplatte 11 und eine Rückseite 12 aufweist. Die Frontplatte 11 trägt eine Fresnel-Linse 1 und unter dieser am Rand ein Sensorelement 7, das an eine integrierte Auswerteschaltung 8 angeschlossen ist, die beispielsweise entsprechend US 4179 691 oder US 4166 955 ausgebildet sein kann. Das Ausgangssignal dieser Auswerteschaltung 8 wird an den Ausgangsklemmen 9 abgenommen. Die Rückseite 12 trägt einen Facetten-Spiegel 13, dessen einzelne Facetten den Reflektor 2, 3, ... 6 entsprechen. Die Ausbildung und Ausrichtung der einzelnen Facetten ist dabei so, dass in Zusammenwirkung mit der Fresnel-Linse 1 ein Bündel vieler Empfangsrichtungen oder Bereiche mit kleinem Öffnungswinkel entsteht.FIG. 3 shows an infrared intrusion detector with a housing 10 which has a front plate 11 and a rear side 12. The front plate 11 carries a Fresnel lens 1 and below this a sensor element 7 on the edge, which is connected to an integrated evaluation circuit 8, which can be designed, for example, in accordance with US Pat. No. 4,179,691 or US Pat. No. 4,166,955. The output signal of this evaluation circuit 8 is taken from the output terminals 9. The rear side 12 carries a facet mirror 13, the individual facets of which correspond to the reflector 2, 3,... 6. The formation and alignment of the individual facets is such that, in cooperation with the Fresnel lens 1, a bundle of many reception directions or areas with a small opening angle is created.

Bei der zweckmässigen Weiterbildung können statt eines einzigen Sensorelementes mehrere nebeneinander angeordnete Sensorelemente (7, 7', 7") vorgesehen sein. Jedes Element erhält dabei Strahlung aus einer Mehrzahl von Empfangsbereichen. Die Anzahl der möglichen Empfangsbereiche kann damit entsprechend der Anzahl der Sensorelemente vervielfacht werden, wobei kein wesentlicher Intensitäts- oder Empfindlichkeitsverlust eintritt, da jedes Sensorelement einen Grossteil der Strahlung vom gemeinsamen Bündelungsmittel erhält. Zweckmässig kann es sein, als Sensorelement ein «Sensor-Array» zu verwenden, bei dem die einzelnen Elemente in einer Linie nebeneinander angeordnet sind. Die einzelnen Empfangsbereiche werden dabei jeweils in ein in einer Ebene liegendes Bündel mehrerer Empfangsbereiche aufgespaltet. Damit lassen sich auf einfache Weise eine Anzahl von einem Eindringling zu passierende Strahlungsvorhänge schaffen.In the expedient development, instead of a single sensor element, a plurality of sensor elements (7, 7 ', 7 ") arranged next to one another can be provided. Each element receives radiation from a plurality of reception areas. The number of possible reception areas can thus be multiplied according to the number of sensor elements , with no significant loss in intensity or sensitivity, since each sensor element receives a large part of the radiation from the common bundling means. It can be expedient to use a "sensor array" as sensor element, in which the individual elements are arranged in a line next to one another. The individual reception areas are each split into a bundle of several reception areas lying on one level, making it easy to create a number of radiation curtains to be passed by an intruder.

Figur 4 zeigt eine besonders flache Ausführungsform eines Infrarot-Einbruchdetektors, bei welchem die gesamte Vorderseite 11 von einem Segment einer Fresnel-Linse 1 eingenommen wird, in deren Zentrum das.Sensorelement 7 angebracht ist. An der Rückseite 12 sind in einer Reihe nebeneinander einzelne Reflektoren 2, 3, ... 6 vorgesehen. Auf der Grundplatte 14 ist die Auswerteschaltung 8 angebracht. Mit dieser Anordnung lässt sich ein Fächer von in einer Ebene liegenden Empfangsbereichen, oder ein Schutzvorhang bilden. Der Detektor kann Dank seiner flachen Ausführung unauffällig in einem schmalen Spalt angeordnet sein, wobei die Vorderfläche 11 optimal zur Aufnahme von Infrarot-Strahlung aus den Empfangsbereichen ausgenützt wird.FIG. 4 shows a particularly flat embodiment of an infrared intrusion detector, in which the entire front side 11 is occupied by a segment of a Fresnel lens 1, in the center of which the sensor element 7 is attached. Individual reflectors 2, 3,... 6 are provided in a row on the rear side 12. The evaluation circuit 8 is attached to the base plate 14. With this arrangement, a fan of reception areas lying on one level or a protective curtain can be formed. Thanks to its flat design, the detector can be arranged inconspicuously in a narrow gap, the front surface 11 being optimally used for receiving infrared radiation from the reception areas.

In einer vorteilhaften Weiterbildung können vor oder hinter Teilen der Sammellinse 1 ein oder mehrere Prismen vorgesehen sein, durch die die einzelnen Empfangsstrahlen jeweils in mehrere Strahlen aufgespaltet werden können. Dadurch kann die Anzahl der Strahlungsempfangsbereiche vervielfacht werden, falls eine gewisse Intensitätsschwächung der einzelnen Bereiche in Kauf genommen werden kann.In an advantageous development, one or more prisms can be provided in front of or behind parts of the converging lens 1, through which the individual reception beams can each be split into a plurality of beams. As a result, the number of radiation receiving areas can be multiplied if a certain intensity weakening of the individual areas can be accepted.

Bei dem in Figur 4 dargestellten Infrarot-Einbruchdetektor können beispielsweise vor beiden Seiten der Fresnel-Linse 1 Prismen 15, 15' angeordnet sein. Diese bewirken, dass die auf die Prismen auftreffende Strahlung um einen bestimmten Winkel abgelenkt wird, während die auf die Linse direkt auftreffende Strahlung unbeeinflusst bleibt. Jeder Empfangsbereich wird daher in drei getrennte Bereiche aufgespaltet.In the infrared intrusion detector shown in FIG. 4, prisms 15, 15 'can be arranged in front of both sides of the Fresnel lens, for example. These have the effect that the radiation impinging on the prisms is deflected by a certain angle, while the radiation impinging directly on the lens remains unaffected. Each reception area is therefore split into three separate areas.

Das Prismen-Element kann auch mit der Sammellinse vereint und in diese integriert sein, indem sie als Mehr-Zonen-Linse mit Zonen unterschiedlicher optischer Achse ausgeführt ist. In Figur 4 können beispielsweise die Seiten der Fresnel-Linse 1 auf ihrer Vorder- oder Rückseite die Form von Keilen 16, 16' aufweisen, die die Prismen 15, 15' ersetzen und die gleiche optische Wirkung zeigen. Ein solches optisches Element ist besonders einfach herstellbar und erfordert keine spezielle Justierung.The prism element can also be combined with and integrated into the converging lens in that it is designed as a multi-zone lens with zones of different optical axes. In Figure 4, for example, the sides of the Fresnel lens 1 has on its front or back the shape of wedges 16, 16 'which replace the prisms 15, 15' and show the same optical effect. Such an optical element is particularly easy to manufacture and requires no special adjustment.

Der dargestellte Infrarot-Einbruchdetektor besitzt trotz seiner flachen unauffälligen Form und seiner kleinen Abmessungen eine optimale Empfindlichkeit und weist zu dem eine besonders einfache und störunanfällige Konstruktion auf. Er eignet sich besonders für Verwendungen wo ein Infrarot-Schutzvorhang mit eng nebeneinander in einer Ebene liegenden Empfangsbereichen erwünscht ist.Despite its flat, inconspicuous shape and small dimensions, the infrared intrusion detector shown has an optimal sensitivity and, moreover, has a particularly simple and interference-free construction. It is particularly suitable for applications where an infrared protective curtain with closely spaced reception areas is desired.

Claims (5)

1. Optical arrangement for an infrared intrusion detector comprising
- a Fresnel lense (1) for focussing infrared radiation impinged from different regions of a surveillance area in different directions onto said lense into different regions being correlated to said regions,
- at least one sensor element (7; 7, 7'; 7") being sensible for infrared radiation,
- a plurality of radiation conducting elements (2-6; 13) being arranged rearwardly of said Fresnel lense for conducting the infrared radiation received from predetermined regions of the surveillance area being separated from each other onto each of the sensor elements, characterized in that
- the radiation conducting elements consist of reflectors (2-6; 13) and
- that each of the sensor elements (7; 7', 7") is formed by a pyroelectrical sensor element being arranged in the plane of the Fresnel lense (1).
2. Optical arrangement according to claim 1, characterized in that said reflectors (2-6) are structured as spherical mirror-segments.
3. Optical arrangement according to claim 1, characterized in that said reflectors (2-6) are structured as planar mirrors which are inclined relative to one another.
4. Optical arrangement according to claim 1, characterized in that said reflectors are combined to a faceted mirror (13).
5. Optical arrangement according to claim 1, characterized in that said reflectors (2-6) are arranged in a row adjacent to one another.
EP81107844A 1980-10-24 1981-10-02 Optical arrangement for an infrared intrusion detector Expired EP0050751B1 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AT81107844T ATE24786T1 (en) 1980-10-24 1981-10-02 OPTICAL ARRANGEMENT FOR AN INFRARED BREAKDOWN DETECTOR.

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
CH7925/80A CH650604A5 (en) 1980-10-24 1980-10-24 OPTICAL ARRANGEMENT FOR AN INFRARED BURGLAR DETECTOR.
CH7925/80 1980-10-24

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EP0050751A1 EP0050751A1 (en) 1982-05-05
EP0050751B1 true EP0050751B1 (en) 1987-01-07

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US (1) US4429224A (en)
EP (1) EP0050751B1 (en)
JP (1) JPS5797481A (en)
AT (1) ATE24786T1 (en)
AU (1) AU542797B2 (en)
CH (1) CH650604A5 (en)
DE (1) DE3175818D1 (en)

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Also Published As

Publication number Publication date
AU7669481A (en) 1982-04-29
US4429224A (en) 1984-01-31
AU542797B2 (en) 1985-03-14
JPS5797481A (en) 1982-06-17
ATE24786T1 (en) 1987-01-15
CH650604A5 (en) 1985-07-31
EP0050751A1 (en) 1982-05-05
DE3175818D1 (en) 1987-02-12

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