EP0219954A1 - Infrarot-Detektorsystem - Google Patents

Infrarot-Detektorsystem Download PDF

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Publication number
EP0219954A1
EP0219954A1 EP86306815A EP86306815A EP0219954A1 EP 0219954 A1 EP0219954 A1 EP 0219954A1 EP 86306815 A EP86306815 A EP 86306815A EP 86306815 A EP86306815 A EP 86306815A EP 0219954 A1 EP0219954 A1 EP 0219954A1
Authority
EP
European Patent Office
Prior art keywords
infra
lens
sensor
view
red
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP86306815A
Other languages
English (en)
French (fr)
Inventor
John T. Grant
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
MAXIMAL ELECTRICAL ENGINEERS Ltd
Original Assignee
MAXIMAL ELECTRICAL ENGINEERS Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by MAXIMAL ELECTRICAL ENGINEERS Ltd filed Critical MAXIMAL ELECTRICAL ENGINEERS Ltd
Publication of EP0219954A1 publication Critical patent/EP0219954A1/de
Withdrawn legal-status Critical Current

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Classifications

    • 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

Definitions

  • the invention relates to a motion detection system mainly used as an intruder sensor in burglar alarm systems.
  • the invention herein described detects changes in infra- red (7-12 micron wavelength) energy collected by a plurality of optical fields-of-view, each focussing on a common infra-red sensing device such that when an intruder moves across the field-of-view the instantaneous infra-red energy level falling on the detector will fluctuate and thus provide a fluctuating electrical signal.
  • intruder detectors using these techniques have been in use in the security industry for many years.
  • the means of achieving a plurality of fields-of-view in currently available intruder sensors fall broadly into two types.
  • One type uses a number of reflective elements such as spherical, parabolic or other conic-section mirrors or mirror segments, located radially around a common infra-red detector such that the detector is at the focus of each mirror.
  • the axis of each mirror is arranged to radiate from the unit radially so that the room or area to be protected is covered by a fan shaped series of fields-of-view. It is common practice to have a further series of mirror segments similarly sharing the common detector, but arranged to provide a further fan-shaped array of fields of view angled below the first set to prevent an intruder moving below then and thus avoiding detection.
  • the other common type of intruder sensor uses a plurality of refractive elements, typically an array of Fresnel lenses, sharing an infra-red detector located at the common focus of the lenses, which are radially disposed to provide a fan-shaped series of fields of view. Again, further ranks of lenses may be used to provide additional downward-pointing fields of view to prevent an intruder avoiding detection.
  • refractive elements typically an array of Fresnel lenses, sharing an infra-red detector located at the common focus of the lenses, which are radially disposed to provide a fan-shaped series of fields of view.
  • further ranks of lenses may be used to provide additional downward-pointing fields of view to prevent an intruder avoiding detection.
  • the infra-red detecting device is typically a commercially available pyro-electric device having two sensing elements electrically connected in opposition, such that changes in infra-red energy falling upon both detectors simultaneously will cause cancellation of signals, whereas energy falling on one or other element will cause an electrical output.
  • the infra-red detecting device is typically a commercially available pyro-electric device having two sensing elements electrically connected in opposition, such that changes in infra-red energy falling upon both detectors simultaneously will cause cancellation of signals, whereas energy falling on one or other element will cause an electrical output.
  • both detector elements are located on the focal plane of the focussing mirrors or lenses, each mirror or lens axis provides in effect two fields of view, one for each element.
  • each lens segment should be flat, with the bending only occurring at the gaps between the segments, in practice the lens segments take on the general curvature of the array, and thus cause considerable abberation and loss of focus of the intruder's infra-red energy falling upon the detector.
  • the present invention seeks to overcome the disadvantages shown above by providing a means wherein a plurality of fields of view . are obtained without the need for a plurality of mirror or lens segments thus giving a considerable space saving in the vulnerable frontal area of a complete intruder sensor.
  • United Kingdom Patent No. 1 3?5 410 describes an intruder alarm using a concave mirror divided into separate segments. Such an arrangement can only achieve a good resolving power if the mirror segments have a long focal length and large individual dimensions, for the reasons described above. Furthermore, such an arrangement has a large number of components which require to be accurately positioned, and leads to a complicated and expensive construction.
  • the arrangement of the present invention in contrast, is simpler, cheaper and easier to construct and adjust.
  • the circuit of Figure 1 shows an infra-red sensor comprising two detectors connected back to back in the input circuit of a band pass amplifier. The output of this amplifier is applied to a threshhold device and when the signal level exceeds the threshhold, an alarm relay is activated.
  • FIG. 2 is an exploded view of the optical components of the invention.
  • a Fresnel lens plate 1 is focussed on the surface of an infra-red sensor 5, the sensor 5 has two detecting elements connected in opposition behind a filter window which allows transmission of infra-red energy of more than 6 microns wavelength.
  • a pair of vertical mirrors 2 and 3 inclined at a small angle preferably about 6 degrees, to the optic axis of the Fresnel lens plate 1.
  • a further reflector 4 inclined to the horizontal similarly at a small angle.
  • Figure 3 shows diagrammatically in plan view some of the fields of view generated by this arrangement. As shown in Figure 3, five diverging fields of view are generated, only three of which are shown in the diagram for clarity.
  • a first field of view indicated by dashed lines with single arrows corresponds to an infra-red beam falling normally onto the surface of the lens plate 1 and focussed by it onto the detector 5.
  • a second field of view indicated by the dashed lines with double arrows corresponds to a beam focussed by the lens 1 and reflected by the mirror surface 2 onto the detector 5.
  • a similar field of view not shown in the diagram correspond to a beam symmetrically disposed on the other side of the axis and reflected by the mirror 3.
  • a further field corresponds to a beam indicated by the triple headed arrows which after refraction by the lens 1 is reflected twice, once at the mirror 3 and a second time at the mirror 2 before reaching the detector 5.
  • a similar field not shown in the diagram exists on the other side of the axis corresponding to reflection first at the mirror 2 and then at the mirror 3.
  • Figure 4 is a diagrammatic sectional elevation showing how the top mirror 4 provides a lower set of fields of view corresponding to those in Figure 3.
  • the dashed lines with single arrow heads correspond to the upper fields while those with double arrow heads show fields corresponding to reflection by the mirror 4 and inclined downwards in order to detect an intruder below the main fields.
  • Figure 5 shows how the apparent images of the detector caused by reflectors 2 and 3 determine the positions of the fields of view.
  • Figure 6 shows a typical electrical signal resulting from an intruder crossing through all fields of view.
  • the positive-going signals result from detector element A receiving energy, and the negative-going signal results from detector element B receiving energy.
  • the relative spacing and angles of the plane reflectors may be changed to give different positions of the fields of view.
  • Infra-red energy may enter the system from angles wider than those shown by means of further internal reflections D etween reflectors 2 and 3 before finally reaching the detecting elements.
  • this energy will be unfocussed, due to the excessive path length, and also may arrive at the detector front filter window at or above the angle of incidence or cone of acceptance.
  • the detector 5 is located closer to the lens than the ideal focal length, and the resulting loss of focus compensated for by a lower f number than would be required for an ideally placed detector.
  • energy arriving at the detector via one or both plane reflectors 2 and 3 will be in focus and all arrive at the detecting element, thereby compensating for reflective losses.
  • plane reflector 4 ensures that energy arriving from locations vertically below fields of view, Al, B1 to A5, B5, and within the lower angled fields of view, will arrive at the detector elements A or B.
  • Figure 4 shows the path by which energy from an intruder entering angled fields of view A6 would reach detector element A via plane reflector 4.
  • energy entering the other angled fields of view would arrive via reflectors 2 or 3 and 4.
  • an intruder sensor would preferably be located about 7ft. (2.1 metres) above the floor and angled such that the main rank of fields of view would be angled at about 10° downwards.
  • the lower angled fields of view angled at about 40° downwards would therefore reach the floor at a distance of some 12 feet (3.6 metres).
  • the de-focussed and therefore wider field of view would still gather sufficient energy from the relatively close intruder. Note: (provided the intruder full fills the field of view, the energy collected will remain constant with his distance from the sensor).
  • two positive focus lenses A and B are located in relation to two plane reflectors.
  • the lenses are off-axis segments.
  • Figure 8 shows the electrical signal from detector 5 for movement of an intruder across the fields of view.
  • a further embodiment, shown in Figure 9, shows the axis for lens A going through the lens segment, whereas the axis for lens B is outside the lens segment.
  • This arrangement may also provide means whereby the fields of view may be interleaved or interspaced.
  • Fresnel type lenses but normal refractive lenses made from germanium, or other material offering a low loss to 7 - 12 micron infra-red energy, may also be used.

Landscapes

  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Geophysics And Detection Of Objects (AREA)
  • Burglar Alarm Systems (AREA)
EP86306815A 1985-09-05 1986-09-03 Infrarot-Detektorsystem Withdrawn EP0219954A1 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB8522086 1985-09-05
GB858522086A GB8522086D0 (en) 1985-09-05 1985-09-05 Infra-red detector system

Publications (1)

Publication Number Publication Date
EP0219954A1 true EP0219954A1 (de) 1987-04-29

Family

ID=10584784

Family Applications (1)

Application Number Title Priority Date Filing Date
EP86306815A Withdrawn EP0219954A1 (de) 1985-09-05 1986-09-03 Infrarot-Detektorsystem

Country Status (2)

Country Link
EP (1) EP0219954A1 (de)
GB (1) GB8522086D0 (de)

Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2199659A (en) * 1986-12-01 1988-07-13 Floorplan Electrica Ltd Occupancy sensing device
EP0321051A2 (de) * 1987-12-18 1989-06-21 Philips Electronics Uk Limited Pyroelektrische Infrarotsensoren
GB2221984A (en) * 1988-05-11 1990-02-21 Graham Wild Optical detector
EP0435120A2 (de) * 1989-12-23 1991-07-03 Asea Brown Boveri Aktiengesellschaft Passiv-Infrarot-Bewegungsmelder
DE4218151A1 (de) * 1991-06-03 1992-12-10 Murata Manufacturing Co System und verfahren zum erfassen einer waermequellenbewegung
EP0537024A1 (de) * 1991-10-10 1993-04-14 Security Enclosures Limited Infrarote-Detektierungsvorrichtung
US5414255A (en) * 1993-11-08 1995-05-09 Scantronic Limited Intrusion detector having a generally planar fresnel lens provided on a planar mirror surface
GB2286042A (en) * 1994-01-27 1995-08-02 Security Enclosures Ltd Wide angle passive infra-red intruder detector
DE4430778A1 (de) * 1994-08-30 1996-03-07 Sick Optik Elektronik Erwin Tubus

Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3703718A (en) * 1971-01-07 1972-11-21 Optical Coating Laboratory Inc Infrared intrusion detector system
US4087688A (en) * 1976-06-16 1978-05-02 Cerberus Ag Infrared radiation-burglary detector
DE2836462A1 (de) * 1978-08-21 1980-03-06 Woerl Alarm August Woerl Inhab Raumueberwachungs-empfangseinrichtung
EP0065159A2 (de) * 1981-05-18 1982-11-24 Richard Hirschmann Radiotechnisches Werk Bewegungsmelder zur Raumüberwachung
US4442359A (en) * 1982-03-01 1984-04-10 Detection Systems, Inc. Multiple field-of-view optical system
DE3424135A1 (de) * 1984-06-30 1986-01-09 Richard Hirschmann Radiotechnisches Werk, 7300 Esslingen Meldeeinrichtung zur raumueberwachung
EP0177130B1 (de) * 1984-09-25 1989-03-08 Matsushita Electric Works, Ltd. Passiver Infrarotstrahlungsdetektor

Patent Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3703718A (en) * 1971-01-07 1972-11-21 Optical Coating Laboratory Inc Infrared intrusion detector system
US3703718B1 (de) * 1971-01-07 1982-04-13
US4087688A (en) * 1976-06-16 1978-05-02 Cerberus Ag Infrared radiation-burglary detector
DE2836462A1 (de) * 1978-08-21 1980-03-06 Woerl Alarm August Woerl Inhab Raumueberwachungs-empfangseinrichtung
EP0065159A2 (de) * 1981-05-18 1982-11-24 Richard Hirschmann Radiotechnisches Werk Bewegungsmelder zur Raumüberwachung
US4442359A (en) * 1982-03-01 1984-04-10 Detection Systems, Inc. Multiple field-of-view optical system
DE3424135A1 (de) * 1984-06-30 1986-01-09 Richard Hirschmann Radiotechnisches Werk, 7300 Esslingen Meldeeinrichtung zur raumueberwachung
EP0177130B1 (de) * 1984-09-25 1989-03-08 Matsushita Electric Works, Ltd. Passiver Infrarotstrahlungsdetektor

Cited By (18)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2199659A (en) * 1986-12-01 1988-07-13 Floorplan Electrica Ltd Occupancy sensing device
GB2199659B (en) * 1986-12-01 1991-08-14 Floorplan Electrica Ltd Occupancy detectors etc
EP0321051A2 (de) * 1987-12-18 1989-06-21 Philips Electronics Uk Limited Pyroelektrische Infrarotsensoren
GB2213927A (en) * 1987-12-18 1989-08-23 Philips Electronic Associated Pyroelectric infrared sensors
EP0321051A3 (de) * 1987-12-18 1990-05-23 Philips Electronics Uk Limited Pyroelektrische Infrarotsensoren
GB2221984A (en) * 1988-05-11 1990-02-21 Graham Wild Optical detector
EP0435120A2 (de) * 1989-12-23 1991-07-03 Asea Brown Boveri Aktiengesellschaft Passiv-Infrarot-Bewegungsmelder
EP0435120A3 (en) * 1989-12-23 1992-06-17 Asea Brown Boveri Aktiengesellschaft Passive infra-red movement detector
DE4218151A1 (de) * 1991-06-03 1992-12-10 Murata Manufacturing Co System und verfahren zum erfassen einer waermequellenbewegung
DE4218151C2 (de) * 1991-06-03 2003-05-28 Murata Manufacturing Co System zum Erfassen der Bewegung einer Wärmequelle
EP0537024A1 (de) * 1991-10-10 1993-04-14 Security Enclosures Limited Infrarote-Detektierungsvorrichtung
US5414255A (en) * 1993-11-08 1995-05-09 Scantronic Limited Intrusion detector having a generally planar fresnel lens provided on a planar mirror surface
GB2286042A (en) * 1994-01-27 1995-08-02 Security Enclosures Ltd Wide angle passive infra-red intruder detector
US5572033A (en) * 1994-01-27 1996-11-05 Security Enclosures Limited Wide-angle infra-red detection apparatus
GB2286042B (en) * 1994-01-27 1998-07-29 Security Enclosures Ltd Wide-angle infra-red detection apparatus
DE4430778A1 (de) * 1994-08-30 1996-03-07 Sick Optik Elektronik Erwin Tubus
US5748816A (en) * 1994-08-30 1998-05-05 Sick Ag Optical cavity for exclusively receiving light parallel to an optical axis
DE4430778C2 (de) * 1994-08-30 2000-01-27 Sick Ag Tubus

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Publication number Publication date
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