EP0501253A1 - Apparatus for detecting fires in a wide area, particularly forest fires - Google Patents

Apparatus for detecting fires in a wide area, particularly forest fires Download PDF

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Publication number
EP0501253A1
EP0501253A1 EP92102453A EP92102453A EP0501253A1 EP 0501253 A1 EP0501253 A1 EP 0501253A1 EP 92102453 A EP92102453 A EP 92102453A EP 92102453 A EP92102453 A EP 92102453A EP 0501253 A1 EP0501253 A1 EP 0501253A1
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EP
European Patent Office
Prior art keywords
sensor elements
arrangement according
sensitive
radiation
infrared radiation
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EP92102453A
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German (de)
French (fr)
Inventor
Kurt Albert Müller
Christoph Enderli
Peter Ryser
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Cerberus AG
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Cerberus AG
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    • G—PHYSICS
    • G08—SIGNALLING
    • G08B—SIGNALLING OR CALLING SYSTEMS; ORDER TELEGRAPHS; ALARM SYSTEMS
    • G08B17/00—Fire alarms; Alarms responsive to explosion
    • G08B17/005—Fire alarms; Alarms responsive to explosion for forest fires, e.g. detecting fires spread over a large or outdoors area
    • 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
    • G—PHYSICS
    • G08—SIGNALLING
    • G08B—SIGNALLING OR CALLING SYSTEMS; ORDER TELEGRAPHS; ALARM SYSTEMS
    • G08B17/00—Fire alarms; Alarms responsive to explosion
    • G08B17/12—Actuation by presence of radiation or particles, e.g. of infrared radiation or of ions
    • G08B17/125—Actuation by presence of radiation or particles, e.g. of infrared radiation or of ions by using a video camera to detect fire or smoke

Definitions

  • the invention relates to an arrangement for detecting fires in an extensive area, in particular forest fires, according to the preamble of patent claim 1.
  • Such arrangements are e.g. known from EP-A1-0'298'182. They are used to determine and localize infrared radiation from objects with a temperature in the range of approx. 300 to 1500 ° C in a surveillance area of a few kilometers. In particular, they are suitable for the detection of forest fires in an extensive forest area from central monitoring points. They have an azimuthally movable scanning device for detecting the infrared radiation emanating from a forest fire with an optical bundling device, e.g. a reflector, which directs the infrared radiation arriving from a number of reception fields to a corresponding number of sensor elements. These sensor elements are provided in close proximity to one another in a row perpendicular to the reflector axis.
  • a disadvantage of such known arrangements is that the detection sensitivity decreases with increasing distance, ie with decreasing elevation or inclination of the corresponding reception field with respect to the horizontal, ie that a fire which is farther away is more difficult to detect than a fire in the close range.
  • DE-A1-37'10'265 it is known to have this disadvantage to avoid that the detection arrangement not only executes an azimuthal movement, but that the elevation angle fluctuates periodically. With this vertical swivel movement, the focal length of the focusing optics is automatically controlled as a function of the elevation angle so that the resolution of the infrared sensor remains approximately constant for the entire monitoring range. This requires complicated and fault-prone control with additional moving components. This makes long-term operation in hard-to-reach locations almost impossible, as frequent maintenance of the systems is required.
  • the object of the invention is to eliminate the disadvantages mentioned of the forest fire detectors of the prior art and, in particular, to create an arrangement of the type mentioned at the beginning which enables a fire with low susceptibility to interference to parasitic radiation sources to detect a radiation maximum in a different spectral range and with little dependence of the detection sensitivity of the source of the fire on the distance in an extended range.
  • the sensor elements sensitive to infrared radiation are arranged in pairs in differential circuits, while to switch off direct solar radiation additional light-sensitive sensor elements in an inhibition circuit with the associated ones sensor elements sensitive to infrared radiation are provided.
  • the sensor elements are designed and arranged in such a way that the detection sensitivity does not decrease significantly with respect to the horizontal as the angle of inclination of the reception fields formed by the sensor element and optical bundling device decreases.
  • reception areas of the sensor elements are selected to be different sizes for reception areas of different elevation, i.e. for radiation detection from reception areas of different distances, or that a different number of sensor elements of the same area is provided for larger distances than for smaller distances.
  • a distance-independent sensitivity can be achieved in that the evaluation circuits for the different sensor elements are designed with a different degree of amplification depending on the respective elevation angle of the associated reception area.
  • several groups of sensor elements are provided in a common optical arrangement in a row perpendicular to the optical axis adjacent to one another on a common carrier, the groups adjacent to the optical axis for remote reception having a smaller vertical extension of the receiving surface or a smaller number of sensor elements than the sensor element groups at a greater distance from the optical axis, which are used for near detection.
  • the individual sensor elements which are preferably sensitive to infrared radiation with a wavelength in the range from 3 to 5 ⁇ m, are further sensor elements with a sensitivity, preferably to radiation in the range from 0.6 to 1 ⁇ m, ie in the range of visible light and the near infrared range, assigned in differential circuit, which are connected to the first-mentioned sensor elements by means of inhibition circuits, which block the fire alarm signal when the latter sensor elements receive radiation with at least a predetermined intensity, that is to say that intensive light radiation is not reported as a fire.
  • the arrangement shown in Figure 1 for the detection of forest fires in an extended area B with an extension of several kilometers has a scanning device 1, which is located on an elevated point of the surveillance area, e.g. is arranged on a mountain peak or on an observation tower 2 or a mast.
  • This scanning device 1 continuously carries out an azimuthal rotation or pivoting movement about its vertical axis and periodically sweeps over the entire surveillance area and in doing so picks up the infrared radiation arriving from the monitored area by means of an optical arrangement 3 and guides it to a sensor arrangement 4 which is equipped with a ( suitable evaluation circuit (not shown) is connected, which triggers an alarm signal as soon as the sensor arrangement 4 receives an infrared radiation characteristic of a forest fire from the monitored area B.
  • the optical arrangement 3 and the sensor arrangement 4, as can be seen for example from FIG. 2, are designed and arranged relative to one another in such a way that a number of separate, adjoining reception fields R1 which are concentric with respect to the installation location of the detection arrangement or the scanning device 1 , R2 ... R8 with different elevation angles b1, b2 ... b8 against the horizontal H, from which the incoming Infrared radiation is received and evaluated separately, so that the location F of a forest fire can be localized and signaled by azimuth a and distance d by means of the evaluation circuit.
  • the structure of the scanning device 1 is shown in greater detail in FIGS. 3 and 4.
  • it has a spherical or parabolic reflector 6 and a sensor carrier 7 arranged approximately in the focal surface of the reflector 6 for a number of sensor elements S1, S2 ... S8.
  • the axis A of the reflector 6 is oriented horizontally or slightly inclined to the horizontal H, corresponding to the maximum detection distance, i.e. the elevation angle b1 of the most distant reception field R1.
  • the sensor carrier 7 is arranged symmetrically with respect to the optical axis A and extends approximately from the axis A over a certain distance, so that practically only radiation from areas below the horizontal H is detected.
  • a number of sensor elements S1, S2 ... S8 in the form of separate radiation-sensitive zones or flakes are provided on the sensor carrier 7 radially from the inside, the output signals of which correspond to the radiation from the different reception fields R with different elevation angles and are evaluated separately from one another.
  • the sensor carrier 7 is closed to the outside with a window which is adapted to the temperature radiation of objects with a temperature of approximately 300 to 1500 ° C., so that the detection arrangement preferably only responds to radiation which is characteristic of a forest fire.
  • the window consists of an optical bandpass filter with a pass band for infrared radiation of preferably about 3 to 5 microns.
  • the spectral window mentioned has proven to be particularly favorable since the transparency of the air in this area is particularly good, which allows detection even over large distances, while in the range from 5 to 8 ⁇ m the absorption in air is considerable, so that the radiation received weakly from distant areas and can therefore only be evaluated to a very limited extent; ie the range of such detectors would be severely limited.
  • Radiation with an even longer wavelength could be parasitic radiation from objects which are only slightly elevated in temperature; she could for example, originate from vehicle engines or originate from terrain or forest areas that are heated up by intensive solar radiation.
  • Figure 5 shows the structure of the sensor element carrier on a larger scale and with further details.
  • the pyroelectric sensor elements S are arranged on the carrier 7 as flakes combined in groups and in pairs with increasing length one above the other and adjoining one another.
  • the lowest group or zone Z1 for remote reception comprises only two flakes S1 and S1 ', which, as shown in FIG. 6A, are connected differentially in a dual circuit to the input FET of the signal evaluation circuit, as do the subsequent groups Z2, Z3 and Z4.
  • Group Z5 on the other hand, has two such flake pairs, that is to say four sensor elements S, S ', S' 'and S' '' in the differential quad circuit shown in FIG.
  • the last near-reception group Z8, which has the greatest vertical extent, consists of fourteen flakes arranged in seven pairs, which are connected to one another in the differential circuit shown in FIG. 6D.
  • each zone Z corresponds to a reception area R of approximately the same size.
  • the different switching of the sensor elements of the individual zones that is to say the dual, quad, double quad switching, etc., has the effect that the detection sensitivity largely depends on the increasing stray capacitances of the circuits becomes independent of the distance or even increases somewhat with the distance, whereby the radiation absorption of the atmosphere, which increases with the distance, is compensated for.
  • These pairs of solar cells C are connected to the corresponding groups of sensor elements S in an inhibition circuit which blocks the fire alarm signal when the parasitic interference radiation picked up by the solar cells from the assigned reception field is sufficiently intense, i.e. exceeds a predetermined threshold. This ensures that the initiation of expensive fire fighting measures due to incorrect signaling can be prevented.
  • a swiveling television camera is provided at the observation site, which is controlled by the fire detection arrangement in such a way that when a fire is signaled it is directed to the location of the fire which is located by the signal evaluation circuit and permits visual control.
  • the invention described above specifically for the detection of forest fires is not limited to these, but can also be used to monitor other extensive areas or areas for the occurrence of infrared radiation. Examples of this include the monitoring of extensive fuel tank farms or car parking spaces.
  • Reference signs (do not belong to the description) Scanner 1 Scanning device Observation tower 2nd Observation tower Optical arrangement 3rd Optical assembly Sensor arrangement 4th Detector assembly reflector 6 Reflector Sensor carrier 7 Detector support axis A Axis azimuth a Azimuth (Surveillance) area B Area (for detection) Elevation angle b Elevation angle Solar cell C. Light-sensitive solar cells distance d Distance Forest fire site F (Location of) forest fire horizontal H Horizontal Reception fields R Detection area Sensor element S Detector elements Zone of sensor elements (group) Z Zone of sensor elements (group)

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  • General Physics & Mathematics (AREA)
  • Business, Economics & Management (AREA)
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  • Life Sciences & Earth Sciences (AREA)
  • Biodiversity & Conservation Biology (AREA)
  • Engineering & Computer Science (AREA)
  • Multimedia (AREA)
  • Photometry And Measurement Of Optical Pulse Characteristics (AREA)
  • Fire-Detection Mechanisms (AREA)

Abstract

A fire-detection apparatus for monitoring wide areas consists of an azimuthally movable scanning device (1), which is mounted in an elevated position and has a reflector (6) in whose focal plane there are provided on a common support (7) a series of adjacent pairs (S, S') of sensor elements which are sensitive to infrared radiation, have an extent which increases upwards starting from the optical axis (A), and are connected to one another in an increasingly insensitive circuit. As a result, an area of virtually the same size is covered in the reception fields (R) of different elevation (b), and a sensitivity of detection is achieved which is independent of distance. In order to eliminate false alarms due to intensive insolation, light-sensitive solar cells (C) are provided parallel to the infrared sensor elements (S) in an inhibition circuit therewith. …<IMAGE>…

Description

Die Erfindung betrifft eine Anordnung zur Detektion von Bränden in einem ausgedehnten Bereich, insbesondere von Waldbränden, gemäß dem Oberbegriff des Patentanspruchs 1.The invention relates to an arrangement for detecting fires in an extensive area, in particular forest fires, according to the preamble of patent claim 1.

Solche Anordnungen sind z.B. aus der EP-A1-0'298'182 bekannt. Sie dienen dazu, Infrarotstrahlung von Objekten mit einer Temperatur im Bereich von ca. 300 bis 1500°C in einem Überwachungsbereich von einigen Kilometern Ausdehnung festzustellen und zu lokalisieren. Insbesondere sind sie zur Erkennung von Waldbränden in einem ausgedehnten Waldgebiet von zentralen Überwachungsstellen aus geeignet. Sie weisen eine azimutal bewegliche Abtasteinrichtung zur Erfassung der von einem Waldbrand ausgehenden Infrarotstrahlung mit einer optischen Bündelungseinrichtung, z.B. einem Reflektor, auf, welche die aus einer Anzahl von Empfangsfeldern eintreffende Infrarotstrahlung auf eine entsprechende Anzahl von Sensorelementen leitet. Diese Sensorelemente sind eng benachbart zueinander in einer Reihe senkrecht zur Reflektorachse vorgesehen. Bei azimutaler Rotation oder Schwenkung der Strahlungsempfangseinrichtung in etwa horizontaler Richtung um eine annähernd vertikale Achse entsteht eine Anzahl von konzentrischen Empfangsfeldern mit unterschiedlicher Elevation oder Neigung gegen die Horizontale, die periodisch bei jedem Umlauf abgetastet werden. Bei Anbringung der Detektionsanordnung an einem erhöhten Punkt, z.B. auf einem Berggipfel oder auf einem hohen Mast, kann ein Areal von mehreren Kilometern Erstreckung von einer einzigen Detektionsanordnung auf das Auftreten einer von einem Waldbrand herrührenden Infrarotstrahlung überwacht werden; mit einer geeigneten Auswerteschaltung kann ein Brandherd lokalisiert und gemeldet werden.Such arrangements are e.g. known from EP-A1-0'298'182. They are used to determine and localize infrared radiation from objects with a temperature in the range of approx. 300 to 1500 ° C in a surveillance area of a few kilometers. In particular, they are suitable for the detection of forest fires in an extensive forest area from central monitoring points. They have an azimuthally movable scanning device for detecting the infrared radiation emanating from a forest fire with an optical bundling device, e.g. a reflector, which directs the infrared radiation arriving from a number of reception fields to a corresponding number of sensor elements. These sensor elements are provided in close proximity to one another in a row perpendicular to the reflector axis. With azimuthal rotation or swiveling of the radiation receiving device in an approximately horizontal direction about an approximately vertical axis, a number of concentric reception fields with different elevation or inclination to the horizontal arise, which are scanned periodically with each revolution. If the detection arrangement is mounted at an elevated point, e.g. on a mountain peak or on a high mast, an area of several kilometers can be monitored by a single detection arrangement for the occurrence of infrared radiation from a forest fire; With a suitable evaluation circuit, a source of fire can be localized and reported.

Nachteilig ist bei solchen bekannten Anordnungen, daß die Nachweisempfindlichkeit mit zunehmender Entfernung also mit abnehmender Elevation oder Neigung des entsprechenden Empfangsfeldes gegen die Horizontale, abnimmt, d.h. daß ein weiter entfernter Brand schwieriger detektiert werden kann als ein Brand im Nahbereich. Gemäß DE-A1-37'10'265 ist es zwar bekannt, diesen Nachteil dadurch zu vermeiden, daß die Detektionsanordnung nicht nur eine azimutale Bewegung ausführt, sondern daß der Elevationswinkel periodisch schwankt. Bei dieser vertikalen Schwenkbewegung wird die Brenweite der Bündelungsoptik in Abhängigkeit vom Elevationswinkel automatisch so gesteuert, daß das Auflösungsvermögen des Infrarotsensors für den ganzen Überwachungsbereich annähernd konstant bleibt. Das erfordert eine komplizierte und störanfällige Steuerung mit zusätzlichen beweglichen Komponenten. Dadurch wird ein langdauernder Betrieb an schwer zugänglichen Aufstellungsorten fast unmöglich gemacht, da eine häufige Wartung der Anlagen erforderlich ist.A disadvantage of such known arrangements is that the detection sensitivity decreases with increasing distance, ie with decreasing elevation or inclination of the corresponding reception field with respect to the horizontal, ie that a fire which is farther away is more difficult to detect than a fire in the close range. According to DE-A1-37'10'265 it is known to have this disadvantage to avoid that the detection arrangement not only executes an azimuthal movement, but that the elevation angle fluctuates periodically. With this vertical swivel movement, the focal length of the focusing optics is automatically controlled as a function of the elevation angle so that the resolution of the infrared sensor remains approximately constant for the entire monitoring range. This requires complicated and fault-prone control with additional moving components. This makes long-term operation in hard-to-reach locations almost impossible, as frequent maintenance of the systems is required.

Ein weiterer Nachteil solcher bekannter Waldbranddetektoren ist ihre Störanfälligkeit gegenüber parasitärer Infrarotstrahlung anderer Herkunft, insbesondere gegenüber direkter oder reflektierter Sonnenstrahlung. Das Sonnenlicht hat zwar sein Maximum im Bereich des sichtbaren Lichts; seine Intensität im infraroten Bereich, d.h. im Bereich der Temperaturstrahlung eines Waldbrandes, kann jedoch so groß sein, daR ein fehlerhaftes Brandsignal ausgelöst werden kann. Auch in diffusem Licht kann der Infrarotanteil so groß sein, daß ein Fehlalarm ausgelöst werden kann.Another disadvantage of such known forest fire detectors is their susceptibility to interference from parasitic infrared radiation from other sources, in particular direct or reflected solar radiation. Sunlight has its maximum in the range of visible light; its intensity in the infrared range, i.e. in the area of the thermal radiation of a forest fire, however, can be so large that a faulty fire signal can be triggered. Even in diffuse light, the infrared portion can be so large that a false alarm can be triggered.

Von der diesem Stand der Technik ausgehend hat sich die Erfindung die Aufgabe gestellt, die genannten Nachteile der Waldbranddetektoren des Standes der Technik zu beseitigen und insbesondere eine Anordnung der eingangs genannten Art zu schaffen, die es ermöglicht, einen Brand mit geringer Störanfälligkeit gegen parasitäre Strahlungsquellen mit einem Strahlungsmaximum in einem anderen Spektralbereich und mit geringer Abhängigkeit der Nachweisempfindlichkeit des Brandherdes von der Entfernung in einem ausgedehnten Bereich zu detektieren.Starting from this prior art, the object of the invention is to eliminate the disadvantages mentioned of the forest fire detectors of the prior art and, in particular, to create an arrangement of the type mentioned at the beginning which enables a fire with low susceptibility to interference to parasitic radiation sources to detect a radiation maximum in a different spectral range and with little dependence of the detection sensitivity of the source of the fire on the distance in an extended range.

Diese Aufgabe wird bei einer Anordnung der eingangs genannten Art durch die kennzeichnenden Merkmale des Patentanspruchs 1 gelöst. Bevorzugte Ausführungsformen der Erfindung und Ausgestaltungen sind in den abhängigen Patentansprüchen definiert.This object is achieved in an arrangement of the type mentioned by the characterizing features of claim 1. Preferred embodiments of the invention and refinements are defined in the dependent claims.

Zur Eliminierung parasitärer Störstrahlung sind die auf Infrarotstrahlung empfindlichen Sensorelemente paarweise in differentiellen Schaltungen angeordnet, während zur Ausschaltung direkter Sonnenstrahlung zusätzliche lichtempfindliche Sensorelemente in einer Inhibitionsschaltung mit den zugeordneten auf Infrarotstrahlung emfindlichen Sensorelementen vorgesehen sind.In order to eliminate parasitic interference radiation, the sensor elements sensitive to infrared radiation are arranged in pairs in differential circuits, while to switch off direct solar radiation additional light-sensitive sensor elements in an inhibition circuit with the associated ones sensor elements sensitive to infrared radiation are provided.

Dabei sind die Sensorelemente derart ausgebildet und angeordnet, daß die Detektionsempfindlichkeit mit abnehmendem Neigungswinkel der durch Sensorelement und optische Bündelungseinrichtung gebildeten Empfangsfelder gegen die Horizontale nicht wesentlich abnimmt.The sensor elements are designed and arranged in such a way that the detection sensitivity does not decrease significantly with respect to the horizontal as the angle of inclination of the reception fields formed by the sensor element and optical bundling device decreases.

Mit besonderem Vorteil kann eine zunehmende Detektionsempfindlichkeit mit abnehmendem Elevationswinkel dadurch erreicht werden, daß für Empfangsbereiche verschiedener Elevation, also zur Strahlungsdetektion aus Empfangsbereichen unterschiedlicher Distanz, die Empfangsflächen der Sensorelemente verschieden groß gewählt werden oder daß für größere Distanzen eine unterschiedliche Anzahl von Sensorelementen gleicher Fläche vorgesehen ist als für kleinere Distanzen. Zusätzlich kann eine distanzunabhängige Empfindlichkeit dadurch erreicht werden, daß die Auswerteschaltungen für die verschiedenen Sensorelemente in Abhängigkeit vom jeweiligen Elevationswinkel des zugehörigen Empfangsbereichs mit einem unterschiedlichen Verstärkungsgrad ausgebildet werden.It is particularly advantageous to achieve an increasing detection sensitivity with a decreasing elevation angle in that the reception areas of the sensor elements are selected to be different sizes for reception areas of different elevation, i.e. for radiation detection from reception areas of different distances, or that a different number of sensor elements of the same area is provided for larger distances than for smaller distances. In addition, a distance-independent sensitivity can be achieved in that the evaluation circuits for the different sensor elements are designed with a different degree of amplification depending on the respective elevation angle of the associated reception area.

Mit Vorteil sind mehrere Gruppen von Sensorelementen in einer gemeinsamen optischen Anordnung in einer Reihe senkrecht zur optischen Achse benachbart zueinander auf einem gemeinsamen Träger vorgesehen, wobei die der optischen Achse benachbarten Gruppen für den Fernempfang eine kleinere vertikale Erstreckung der Empfangsfläche oder eine kleinere Anzahl von Sensorelementen aufweisen als die Sensorelementgruppen in größerem Abstand von der optischen Achse, die der Nahdetektion dienen.Advantageously, several groups of sensor elements are provided in a common optical arrangement in a row perpendicular to the optical axis adjacent to one another on a common carrier, the groups adjacent to the optical axis for remote reception having a smaller vertical extension of the receiving surface or a smaller number of sensor elements than the sensor element groups at a greater distance from the optical axis, which are used for near detection.

Zur Ausblendung der Sonnenstrahlung sind den einzelnen Sensorelementen, die vorzugsweise für Infrarotstrahlung mit einer Wellenlänge im Bereich von 3 bis 5 µm empfindlich sind, weitere Sensorelemente mit einer Empfindlichkeit vorzugsweise für Strahlung im Bereich von 0,6 bis 1 µm, d.h. im Bereich des sichtbaren Lichts und des nahen Infrarotbereichs, in differentieller Schaltung zugeordnet, die mit den erstgenannten Sensorelementen mittels Inhibitionsschaltungen verbunden sind, welche die Brandalarmsignalgabe blockieren, wenn die zuletztgenannten Sensorelemente eine Strahlung mit mindestens einer vorbestimmten Intensität erhalten, d.h. daß intensive Lichtstrahlung nicht als Brand gemeldet wird.To suppress the solar radiation, the individual sensor elements, which are preferably sensitive to infrared radiation with a wavelength in the range from 3 to 5 μm, are further sensor elements with a sensitivity, preferably to radiation in the range from 0.6 to 1 μm, ie in the range of visible light and the near infrared range, assigned in differential circuit, which are connected to the first-mentioned sensor elements by means of inhibition circuits, which block the fire alarm signal when the latter sensor elements receive radiation with at least a predetermined intensity, that is to say that intensive light radiation is not reported as a fire.

Die Erfindung wird im folgenden an Hand der in den Figuren dargestellten bevorzugten Ausführungsformen näher erläutert. Es zeigen:

Figur 1
eine schematische Seitenansicht einer bevorzugten Ausführungsform einer erfindungsgemäßen Branddetektionsanordnung,
Figur 2
eine schematische Draufsicht auf die Anordnung gemäß Figur 1 und ihre Empfangsbereiche,
Figur 3
eine schematische Vorderansicht einer Abtasteinrichtung einer bevorzugten Ausführungsform einer erfindungsgemäßen Branddetektionsanordnung,
Figur 4
einen Querschnitt durch die Abtasteinrichtung gemäß Figur 3,
Figur 5
eine Vorderansicht einer Sensorelementanordnung einer Branddetektionsanordnung gemäß Figuren 1 und 2 und
Figur 6A bis 6D
Schaltungsanordnungen einer Branddetektionsanordnung gemäß Figur 5.
The invention is explained in more detail below with reference to the preferred embodiments shown in the figures. Show it:
Figure 1
2 shows a schematic side view of a preferred embodiment of a fire detection arrangement according to the invention,
Figure 2
2 shows a schematic top view of the arrangement according to FIG. 1 and its reception areas,
Figure 3
1 shows a schematic front view of a scanning device of a preferred embodiment of a fire detection arrangement according to the invention,
Figure 4
3 shows a cross section through the scanning device according to FIG. 3,
Figure 5
a front view of a sensor element arrangement of a fire detection arrangement according to Figures 1 and 2 and
Figure 6A to 6D
Circuit arrangements of a fire detection arrangement according to FIG. 5.

Die in Figur 1 dargestellte Anordnung zur Detektion von Waldbränden in einem ausgedehnten Bereich B mit einer Erstreckung von mehreren Kilometern weist eine Abtasteinrichtung 1 auf, die auf einer erhöhten Stelle des Überwachungsgebietes, z.B. auf einem Berggipfel oder auf einem Beobachtungsturm 2 oder einem Mast angeordnet ist. Diese Abtasteinrichtung 1 führt fortwährend eine azimutale Rotation oder Schwenkbewegung um ihre vertikale Achse aus und überstreicht dabei periodisch das gesamte Überwachungsgebiet und nimmt dabei die aus dem überwachten Areal eintreffende Infrarotstrahlung mittels einer optischen Anordnung 3 auf und leitet sie auf eine Sensoranordnung 4, welche mit einer (nicht dargestellten) geeigneten Auswerteschaltung verbunden ist, die ein Alarmsignal auslöst, sobald die Sensoranordnung 4 aus dem überwachten Bereich B eine für einen Waldbrand charakteristische Infrarotstrahlung empfängt.The arrangement shown in Figure 1 for the detection of forest fires in an extended area B with an extension of several kilometers has a scanning device 1, which is located on an elevated point of the surveillance area, e.g. is arranged on a mountain peak or on an observation tower 2 or a mast. This scanning device 1 continuously carries out an azimuthal rotation or pivoting movement about its vertical axis and periodically sweeps over the entire surveillance area and in doing so picks up the infrared radiation arriving from the monitored area by means of an optical arrangement 3 and guides it to a sensor arrangement 4 which is equipped with a ( suitable evaluation circuit (not shown) is connected, which triggers an alarm signal as soon as the sensor arrangement 4 receives an infrared radiation characteristic of a forest fire from the monitored area B.

Die optische Anordnung 3 und die Sensoranordnung 4 sind, wie z.B. aus der Figur 2 zu ersehen ist, derart ausgeführt und relativ zueinander angeordnet, daß eine Anzahl von getrennten, aneinander anschließenden, bezüglich des Aufstellungsortes der Detektionsanordnung, bzw. der Abtasteinrichtung 1 konzentrischen Empfangsfeldern R1, R2 ... R8 mit unterschiedlichen Elevationswinkeln b1, b2 ... b8 gegen die Horizontale H entsteht, aus denen die eintreffende Infrarotstrahlung getrennt voneinander empfangen und ausgewertet wird, so daß mittels der Auswerteschaltung der Ort F eines Waldbrandes nach Azimut a und Distanz d lokalisiert und signalisiert werden kann.The optical arrangement 3 and the sensor arrangement 4, as can be seen for example from FIG. 2, are designed and arranged relative to one another in such a way that a number of separate, adjoining reception fields R1 which are concentric with respect to the installation location of the detection arrangement or the scanning device 1 , R2 ... R8 with different elevation angles b1, b2 ... b8 against the horizontal H, from which the incoming Infrared radiation is received and evaluated separately, so that the location F of a forest fire can be localized and signaled by azimuth a and distance d by means of the evaluation circuit.

In den Figuren 3 und 4 ist der Aufbau der Abtasteinrichtung 1 in größerem Detail dargestellt. Sie weist zum Zwecke der Fokussierung der aus den Empfangsfeldern R eintreffenden Infrarotstrahlung einen sphärischen oder parabolischen Reflektor 6 auf und einen etwa in der Brennfläche des Reflektors 6 angeordneten Sensorträger 7 für eine Anzahl von Sensorelementen S1, S2 ... S8. Die Achse A des Reflektors 6 is horizontal orientiert oder leicht gegen die Horizontale H geneigt, entsprechend der maximalen Detektionsdistanz, d.h dem Elevationswinkel b1 des am weitesten entfernten Empfangsfeldes R1. Der Sensorträger 7 ist bezüglich der optischen Achse A symmetrisch angeornet und erstreckt sich etwa von der Achse A über eine gewisse Strecke nach oben, so daß praktisch nur Strahlung aus Bereichen unterhalb der Horizontalen H detektiert wird.The structure of the scanning device 1 is shown in greater detail in FIGS. 3 and 4. For the purpose of focusing the infrared radiation arriving from the reception fields R, it has a spherical or parabolic reflector 6 and a sensor carrier 7 arranged approximately in the focal surface of the reflector 6 for a number of sensor elements S1, S2 ... S8. The axis A of the reflector 6 is oriented horizontally or slightly inclined to the horizontal H, corresponding to the maximum detection distance, i.e. the elevation angle b1 of the most distant reception field R1. The sensor carrier 7 is arranged symmetrically with respect to the optical axis A and extends approximately from the axis A over a certain distance, so that practically only radiation from areas below the horizontal H is detected.

Auf dem Sensorträger 7 sind radial von innen nach außen eine Anzahl von Sensorelementen S1, S2 ... S8 in der Form separater strahlungsempfindlicher Zonen oder Flakes vorgesehen, deren Ausgangssignale der Strahlung aus den verschiedenen Empfangsfeldern R mit unterschiedlichen Elevationswinkeln entsprechen und getrennt voneinander ausgewertet werden. Der Sensorträger 7 ist nach außen mit einem Fenster abgeschlossen, das an die Temperaturstrahlung von Objekten mit einer Temperatur von etwa 300 bis 1500°C angepaßt ist, damit die Detektionsanordnung vorzugsweise nur auf Strahlung anspricht, wie sie für einen Waldbrand charakteristisch ist. Das Fenster besteht aus einem optischen Bandpaßfilter mit einem Durchlaßbereich für infrarote Strahlung von vorzugsweise etwa 3 bis 5 µm.A number of sensor elements S1, S2 ... S8 in the form of separate radiation-sensitive zones or flakes are provided on the sensor carrier 7 radially from the inside, the output signals of which correspond to the radiation from the different reception fields R with different elevation angles and are evaluated separately from one another. The sensor carrier 7 is closed to the outside with a window which is adapted to the temperature radiation of objects with a temperature of approximately 300 to 1500 ° C., so that the detection arrangement preferably only responds to radiation which is characteristic of a forest fire. The window consists of an optical bandpass filter with a pass band for infrared radiation of preferably about 3 to 5 microns.

Das genannte Spektralfenster hat sich als besonders günstig erwiesen, da die Transparenz der Luft in diesem Bereich besonders gut ist, was eine Detektion auch über große Distanzen erlaubt, während im Bereich von 5 bis 8 µm die Absorption in Luft beträchtlich ist, so daß die Strahlung aus entfernten Gebieten nur geschwächt empfangen und daher nur sehr beschränkt ausgewertet werden kann; d.h. die Reichweite solcher Detektoren wäre stark eingeschränkt. Strahlung mit noch größerer Wellenlänge könnte parasitäre Strahlung von Objekten sein, die eine nur leicht erhöhte Temperatur aufweisen; sie könnte beispielsweise von Fahrzeugmotoren herrühren oder von Gelände- oder Waldpartien ausgehen, die durch intensive Sonnenstrahlung aufgeheizt werden.The spectral window mentioned has proven to be particularly favorable since the transparency of the air in this area is particularly good, which allows detection even over large distances, while in the range from 5 to 8 μm the absorption in air is considerable, so that the radiation received weakly from distant areas and can therefore only be evaluated to a very limited extent; ie the range of such detectors would be severely limited. Radiation with an even longer wavelength could be parasitic radiation from objects which are only slightly elevated in temperature; she could for example, originate from vehicle engines or originate from terrain or forest areas that are heated up by intensive solar radiation.

Figur 5 zeigt den Aufbau des Sensorelement-Trägers in größerem Maßstab und mit weiteren Details. Auf dem Träger 7 sind die pyroelektrischen Sensorelemente S als gruppenweise und paarweise mit zunehmender Länge zusammengefaßte Flakes übereinander und aneinander anschließend angeordnet. Die unterste Gruppe oder Zone Z1 für den Fernempfang umfaßt nur zwei Flakes S1 und S1', welche gemäß der Darstellung in Figur 6A differentiell in einer Dualschaltung an den Eingang FET der Signalauswerteschaltung angeschlossen sind, desgleichen die anschließenden Gruppen Z2, Z3 und Z4. Die Gruppe Z5 weist dagegen zwei derartige Flake-Paare, also vier Sensorelemente S, S', S'' und S''' in der in Figur 6B gezeigten differentiellen Quadschaltung auf, während die weiteren Gruppen Z6 und Z7 acht Sensorelemente in der in Figur 6C wiedergegebenen differentiellen Doppelquadschaltung aufweisen. Die letzte, dem Nahempfang dienende Gruppe Z8, welche die größte vertikale Erstreckung aufweist, besteht aus vierzehn in sieben Paaren angeordneten Flakes, die in der in Figur 6D wiedergegebenen Differentialschaltung miteinander verbunden sind.Figure 5 shows the structure of the sensor element carrier on a larger scale and with further details. The pyroelectric sensor elements S are arranged on the carrier 7 as flakes combined in groups and in pairs with increasing length one above the other and adjoining one another. The lowest group or zone Z1 for remote reception comprises only two flakes S1 and S1 ', which, as shown in FIG. 6A, are connected differentially in a dual circuit to the input FET of the signal evaluation circuit, as do the subsequent groups Z2, Z3 and Z4. Group Z5, on the other hand, has two such flake pairs, that is to say four sensor elements S, S ', S' 'and S' '' in the differential quad circuit shown in FIG. 6B, while the other groups Z6 and Z7 have eight sensor elements in the one in FIG 6C reproduced differential double quad circuit. The last near-reception group Z8, which has the greatest vertical extent, consists of fourteen flakes arranged in seven pairs, which are connected to one another in the differential circuit shown in FIG. 6D.

Mit diesen differentiellen Paar- oder Dualschaltungen wird zunächst die Elimination von Umwelteinflüssen erreicht, die gleichmäßig auf beide Sensorelemente eines Paares einwirken. Dies gilt auch für intensives Umgebungslicht, das mit einem nicht zu vernachlässigenden Anteil an der Strahlung im Durchlaßbereich des optischen Bandpaßfilters von beispielsweise 3 bis 5 µm auf den breitbandigen pyroelektrischen Sensor auftrifft und das jeweils beide Sensorelemente nahezu gleich beaufschlagt, während ein begrenzter Brandherd bei jedem Durchlauf der Schwenkbewegung zeitverschoben nacheinander von beiden Sensorelementen aufgenommen wird und mittels der differentiellen Schaltung in ein zeitlich gestaffeltes Paar eines positiven und eines negativen Impulssignals umgewandelt wird (Dauersignal = Null).With these differential pair or dual circuits, the elimination of environmental influences, which act equally on both sensor elements of a pair, is initially achieved. This also applies to intense ambient light, which strikes the broadband pyroelectric sensor with a not insignificant proportion of the radiation in the pass band of the optical bandpass filter, for example 3 to 5 µm, and which acts on both sensor elements almost equally, while a limited source of fire during each pass the pivoting movement is recorded in a time-shifted manner by both sensor elements and is converted into a staggered pair of a positive and a negative pulse signal by means of the differential circuit (permanent signal = zero).

Die nach oben zunehmende Länge der Sensorelement-Zonen Z1, Z2 ... Z8 in der gemeinsamen optischen Anordnung 3 hat in grober Näherung zur Folge, daß jede Zone Z etwa einem gleich großen Empfangsbereich R entspricht. Zudem bewirkt die unterschiedliche Schaltung der Sensorelemente der einzelnen Zonen, d.h. die Dual-, Quad-, Doppelquadschaltung etc., daß infolge der zunehmenden Streukapazitäten der Schaltungen die Detektionsempfindlichkeit weitgehend von der Distanz unabhängig wird oder sogar mit der Distanz etwas zunimmt, wodurch die mit der Distanz zunehmende Strahlungsabsorption der Atmosphäre kompensiert wird.The increasing length of the sensor element zones Z1, Z2 ... Z8 in the common optical arrangement 3 has a rough approximation that each zone Z corresponds to a reception area R of approximately the same size. In addition, the different switching of the sensor elements of the individual zones, that is to say the dual, quad, double quad switching, etc., has the effect that the detection sensitivity largely depends on the increasing stray capacitances of the circuits becomes independent of the distance or even increases somewhat with the distance, whereby the radiation absorption of the atmosphere, which increases with the distance, is compensated for.

Weitere Maßnahmen dienen der Ausschaltung direkter oder indirekter Sonnenbestrahlung. Diese ist in waldbrandgefährdeten Gebieten oft beträchtlich und kann zeitweise hunderttausend Lux übersteigen. Die Sonnenstrahlung im Bereich der zur Branddetektion ausgewerteten Infrarotstrahlung, z.B. zwischen 3 und 5 um, kann derart intensiv sein, daß ein fehlerhaftes Alarmsignal ausgelöst wird, ohne daß ein Brand vorliegt; es ist daher erforderlich, die Auslösung solcher Fehlalarme durch parasitäres Sonnenlicht zu verhindern. Dazu sind auf dem Träger 7 parallel neben den für Infrarotstrahlung empfindlichen Sensorelementen S eine Reihe von lichtempfindlichen Sonnenzellen C vorgesehen und zwar ebenfalls in Paaren C1, C1' ... C8, C8' differentiell geschaltet, mit einem spektralen Empfindlichkeitsmaximum zwischen 0,6 und 1 µm. Mit den entsprechenden Gruppen von Sensorelementen S sind diese Sonnenzellenpaare C in einer Inhibitionsschaltung verbunden, welche die Brandalarmsignalgabe blokkiert, wenn die von den Sonnenzellen aus dem zugeordneten Empfangsfeld aufgenommene parasitäre Störstrahlung hinreichend intensiv ist, d.h. eine vorgegebene Schwelle überschreitet. Somit wird erreicht, daß die Einleitung von kostspieligen Brandbekämpfungsmaßnahmen infolge fehlerhafter Signalgabe verhindert werden kann.Further measures are used to switch off direct or indirect solar radiation. This is often considerable in areas prone to forest fires and can sometimes exceed 100,000 lux. The solar radiation in the area of the infrared radiation evaluated for fire detection, e.g. between 3 and 5 µm, can be so intense that an erroneous alarm is triggered without a fire; it is therefore necessary to prevent such false alarms from being triggered by parasitic sunlight. For this purpose, a number of light-sensitive solar cells C are provided in parallel on the carrier 7 in addition to the sensor elements S sensitive to infrared radiation, and also switched differentially in pairs C1, C1 '... C8, C8', with a spectral sensitivity maximum between 0.6 and 1 µm. These pairs of solar cells C are connected to the corresponding groups of sensor elements S in an inhibition circuit which blocks the fire alarm signal when the parasitic interference radiation picked up by the solar cells from the assigned reception field is sufficiently intense, i.e. exceeds a predetermined threshold. This ensures that the initiation of expensive fire fighting measures due to incorrect signaling can be prevented.

Eine noch größere Sicherheit wird erreicht, wenn zusätzlich am Beobachtungsort eine schwenkbare Fernsehkamera vorgesehen wird, die durch die Branddetektionsanordnung derart gesteuert wird, daß sie bei Signalisation eines Brandes auf den von der Signalauswerteschaltung lokalisierten Brandort gerichtet wird und eine visuelle Kontrolle gestattet.An even greater security is achieved if, in addition, a swiveling television camera is provided at the observation site, which is controlled by the fire detection arrangement in such a way that when a fire is signaled it is directed to the location of the fire which is located by the signal evaluation circuit and permits visual control.

Die vorstehend speziell für die Detektion von Waldbränden beschriebene Erfindung ist nicht auf diese beschränkt, sondern kann auch zur Überwachung anderer ausgedehnter Bereiche oder Areale auf das Auftreten von Infrarotstrahlung benutzt werden. Beispiele hierfür sind etwa die Überwachung ausgedehnter Brennstofftanklager oder Automobilabstellplätze. Bezugszeichen (gehören nicht zur Beschreibung) Abtasteinrichtung 1 Scanning device Beobachtungsturm 2 Observation tower Optische Anordnung 3 Optical assembly Sensoranordnung 4 Detector assembly Reflektor 6 Reflector Sensorträger 7 Detector support Achse A Axis Azimut a Azimuth (Überwachungs-)Bereich B Area (for detection) Elevationswinkel b Elevation angle Sonnenzelle C Light-sensitive solar cells Distanz d Distance Waldbrandort F (Location of) forest fire Horizontale H Horizontal Empfangsfelder R Detection area Sensorelement S Detector elements Zone von Sensorelementen (Gruppe) Z Zone of sensor elements (group) The invention described above specifically for the detection of forest fires is not limited to these, but can also be used to monitor other extensive areas or areas for the occurrence of infrared radiation. Examples of this include the monitoring of extensive fuel tank farms or car parking spaces. Reference signs (do not belong to the description) Scanner 1 Scanning device Observation tower 2nd Observation tower Optical arrangement 3rd Optical assembly Sensor arrangement 4th Detector assembly reflector 6 Reflector Sensor carrier 7 Detector support axis A Axis azimuth a Azimuth (Surveillance) area B Area (for detection) Elevation angle b Elevation angle Solar cell C. Light-sensitive solar cells distance d Distance Forest fire site F (Location of) forest fire horizontal H Horizontal Reception fields R Detection area Sensor element S Detector elements Zone of sensor elements (group) Z Zone of sensor elements (group)

Claims (10)

Anordnung zur Detektion von Bränden in einem ausgedehnten Bereich (B), insbesondere von Waldbränden, mit einer azimutal beweglichen Abtasteinrichtung (1) zur periodischen Erfassung der von einem Brand erzeugten Infrarotstrahlung, welche eine optische Bündelungseinrichtung (6) und eine Anzahl von Sensorelementen (S) aufweist, welche so angeordnet und ausgebildet sind, daß sie Infrarotstrahlung aus Empfangsfeldern (R1, R2 ... R8) unterschiedlicher Elevationswinkel (b1, b2 ... b8) detektieren, dadurch gekennzeichnet, daß die für Infrarotstrahlung empfindlichen Sensorelemente (S, S') paarweise horizontal nebeneinander angeordnet und in differentiellen Schaltungen miteinander verbunden sind und daß den für Infrarotstrahlung empfindlichen Sensorelementen (S, S') weitere, geometrisch gleich gestaltete und angeordnete, vorzugsweise für sichtbares Licht empfindliche Sensorelemente (C) zugeordnet sind, welche in analoger Weise in differentieller Schaltung miteinander verbunden sind und welche die Signalgabe der für Infrarotstrahlung empfindlichen Sensorelemente (S, S') blockieren, wenn sie mit Strahlung beaufschlagt werden, deren Intensität eine vorgegebene Schwelle übersteigt.Arrangement for the detection of fires in an extensive area (B), in particular forest fires, with an azimuthally movable scanning device (1) for periodic detection of the infrared radiation generated by a fire, which comprises an optical focusing device (6) and a number of sensor elements (S) which are arranged and designed such that they detect infrared radiation from reception fields (R1, R2 ... R8) of different elevation angles (b1, b2 ... b8), characterized in that the sensor elements (S, S ') which are sensitive to infrared radiation ) are arranged horizontally next to each other in pairs and are connected to each other in differential circuits and that the sensor elements (S, S ') sensitive to infrared radiation are assigned further, geometrically identically designed and arranged, preferably sensitive to visible light sensor elements (C), which are analogously used in differential circuit are interconnected and which block the signaling of the sensor elements sensitive to infrared radiation (S, S ') when they are exposed to radiation, the intensity of which exceeds a predetermined threshold. Anordnung gemäß Patentanspruch 1, dadurch gekennzeichnet, daß die Paare von Sensorelementen (S, S') vertikal aneinander anschließend wenigstens angenähert in der Brennebene der optischen Bündelungseinrichtung (6) angeordnet sind.Arrangement according to claim 1, characterized in that the pairs of sensor elements (S, S ') are arranged vertically next to one another at least approximately in the focal plane of the optical focusing device (6). Anordnung gemäß Patentanspruch 2, dadurch gekennzeichnet, daß die Sensorelemente (S, S') sich auf einem gemeinsamen Träger (7) von etwa der optischen Achse (A) der Bündelungseinrichtung (6) ausgehend nach oben hin erstrecken.Arrangement according to claim 2, characterized in that the sensor elements (S, S ') extend upwards on a common support (7) from approximately the optical axis (A) of the bundling device (6). Anordnung gemäß Patentanspruch 3, dadurch gekennzeichnet, daß die vertikale Erstreckung, die Empfangsfläche und/oder die Anzahl der Sensorelemente (S) mit dem Abstand von der optischen Achse (A) zunimmt.Arrangement according to claim 3, characterized in that the vertical extension, the receiving surface and / or the number of sensor elements (S) increases with the distance from the optical axis (A). Anordnung gemäß Patentanspruch 4, dadurch gekennzeichnet, daß die Zunahme der Erstreckung, Empfangsfläche und/oder Anzahl der Sensorelemente (S) derart gewählt ist, daß die Empfindlichkeit der Empfgangsfelder (R1, R2 ... R8) wenigstens in grober Näherung unabhängig vom Elevationswinkel (b1, b2 ... b8) sind.Arrangement according to claim 4, characterized in that the increase in extension, receiving area and / or number of sensor elements (S) is selected such that the sensitivity of the receiving fields (R1, R2 ... R8) is at least roughly independent of the elevation angle ( b1, b2 ... b8). Anordnung gemäß Patentanspruch 5, dadurch gekennzeichnet, daß die Sensorelement-Paare (S1, S1') mit geringerem Abstand von der optischen Achse (A) in einer Schaltung miteinader verbunden sind, die ein größeres Ausgangssignal liefert als die Schaltungen für Sensorelementpaare (S8, S8') mit größerem Abstand von der Achse (A).Arrangement according to claim 5, characterized in that the sensor element pairs (S1, S1 ') are connected to one another at a smaller distance from the optical axis (A) in a circuit which supplies a larger output signal than the circuits for sensor element pairs (S8, S8 ') at a greater distance from the axis (A). Anordnung gemäß Patentanspruch 6, dadurch gekennzeichnet, daß die Schaltungen derart ausgebildet und angeordnet sind, daß die Detektionsempfindlichkeit mit abnehmendem Elevationswinkel (b1, b2 ... b8) der durch Sensorelement (S) und optische Bündelungseinrichtung (6) gebildeten Empfangsfelder (R) gegen die Horizontale (H) nicht wesentlich abnimmt.Arrangement according to claim 6, characterized in that the circuits are designed and arranged such that the detection sensitivity with decreasing elevation angle (b1, b2 ... b8) of the receiving fields (R) formed by sensor element (S) and optical bundling device (6) the horizontal (H) does not decrease significantly. Anordnung gemäß Patentanspruch 7, dadurch gekennzeichnet, daß die weiteren Sensorelemente (C) auf demselben Träger (7) jeweils neben den zugeordneten für Infrarotstrahlung empfindlichen Sensorelementen (S) angeordnet sind.Arrangement according to claim 7, characterized in that the further sensor elements (C) are arranged on the same carrier (7) next to the associated sensor elements (S) sensitive to infrared radiation. Anordnung gemäß einem der Patentansprüche 1 bis 8, dadurch gekennzeichnet, daß die auf die Sensorelemente (S, S') fallende Strahlung durch ein optisches Bandpaßfilter mit einem Spektralbereich von 3 bis 5 µm gefiltert wird.Arrangement according to one of Claims 1 to 8, characterized in that the radiation falling on the sensor elements (S, S ') is filtered by an optical bandpass filter with a spectral range of 3 to 5 µm. Anordnung gemäß einem der Patentansprüche 1 bis 9, dadurch gekennzeichnet, daß die weiteren Sensorelemente (C) vorzugsweise für Strahlung im Bereich von 0,6 bis 1 µm empfindlich sind.Arrangement according to one of Claims 1 to 9, characterized in that the further sensor elements (C) are preferably sensitive to radiation in the range from 0.6 to 1 µm.
EP92102453A 1991-03-01 1992-02-14 Apparatus for detecting fires in a wide area, particularly forest fires Withdrawn EP0501253A1 (en)

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NO920526L (en) 1992-09-02
NO920526D0 (en) 1992-02-10
CH681574A5 (en) 1993-04-15
US5218345A (en) 1993-06-08

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