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 detector of the type specified in the preamble of claim 1.
• Such passive infrared motion detectors are mainly used as intrusion detection systems, but also serve other purposes, such as for switching on of lighting.
• the infrared radiation emitted by a person or another heat source is bundled by optics and directed at a single detector.
• the smallest changes in radiation flow that is to say changes over time in the temperature difference between the ambient temperature and the respective surface temperature of the person / object, can be detected.
• the monitoring range of passive infrared motion detectors is divided into multiple fields of view with intervening dark fields by multiple Fresnel lens arrangements or mirror optics, which are imaged on a sensor element.
• the size of the passive infrared motion detector concerned is mainly determined by the Fresnel lens arrangements or mirror optics used, which do not allow miniaturization of the devices. These devices are usually housed in relatively large box-shaped housings which are attached to the ceiling or a wall and thus enable the unrestricted detection of movements in the monitored area. It is disadvantageous - in addition to the large construction volume - that the motion detectors can be recognized as such without any problems and that unauthorized persons can obtain information about the installed security measures at any time without further knowledge.
• a motion detector is described in DE-OS 39 00 605, the shape of which is modeled on that of a conventional incandescent lamp.
• An infrared motion detector is also known from DE-OS 29 20 217, the outer contours of which have the shape and dimensions of a flush-mounted box of a standard power supply network system.
• the infrared motion detector is thus sufficiently camouflaged as such - but the possible installation locations are limited to the locations customary for flush-mounted boxes.
• the combination of a travel alarm clock with a motion detector is proposed in DE-PS 34 47 350.
• the camouflage of the motion detector is an advantage of this solution, but the application is also very limited.
• the invention is based on the object of specifying a passive infrared motion detector which ensures the unrestricted detection of the area to be monitored and, despite a sufficient monitoring area, has a construction which is so small compared to the previous embodiments that it is not readily known as Motion detector can be recognized and therefore requires no special camouflage - increasing the manufacturing effort.
• the invention includes the finding that in the case of motion detectors, by providing a passive infrared detector which is arranged as a multi-element sensor in the form of one or more lines behind a converging lens, the field of view of the passive infrared motion detector thus formed in front of the converging lens, according to the number, geometry and arrangement of the multi-element sensors, is divided into several smaller fields of view with dark fields in between, the evaluation circuit triggers an alarm when movement of people / objects is registered in the field of view of the device according to the invention, a substantial miniaturization of the size can be achieved.
• the multi-element sensors represent radiation receivers for recording the thermal radiation emitted by people and / or objects. Pyroelectric sensors which are inexpensive to manufacture and can be operated without additional cooling are particularly suitable for this purpose.
• the converging lens enables the incident heat radiation to be focused on the multi-element sensors and thus an essential miniaturization of the device according to the invention in comparison to known devices.
• the evaluable sensor area is significantly enlarged.
• the geometric size of the optical arrangement, which depicts the detection area on the detector is thus significantly reduced.
• the previously necessary chambers, which served to separate the images of different detection areas on the common sensor element are no longer required.
• the central arrangement of a pinhole in front of the collective lens also avoids the incidence of flat rays and scattered light on the lens and also total reflections within the lens, so that the sensitivity to comparable devices of conventional size is even increased .
• the field of view sectors of the miniaturized passive infrared motion detector can be dimensioned such that persons and / or objects to be detected can be reliably detected.
• the signals occurring at the multi-element sensors are amplified in the associated preamplifiers, digitized in the A / D converter and processed in the evaluation circuit. This triggers an alarm if a movement is registered in the visual fields of the device according to the invention.
• an interface renzfilter in front of the converging lens prevents interference radiation, such as sun or car headlight light, from falling onto the multi-element sensors.
• the output signals of the various pyroelectric sensor elements are combined electrically and fed to a common amplifier. Since the elements each have a high-resistance output, they can be combined with an OR effect without any further logic combination elements, so that every change in an individual sensor element triggers an output signal indicating a movement.
• the detector formed by a multi-element sensor is provided in a housing which is light-tight except for a window provided with a rear panel with a converging lens, the preferably plan-convex lens hermetically sealing the opening.
• the multi-element sensor is mounted on a circuit board together with the further electrical circuit elements, which is fastened parallel to the housing wall opposite the opening.
• the motion sensor according to the invention thus has the shape of a cuboid-shaped container the size of the housing of a highly integrated electronic circuit module, for example a conventional processor, and can thus be placed inconspicuously at any location.
• FIG. 1 shows a possible arrangement of the multi-element sensors in one line, as a detail of an exemplary embodiment as shown in FIG. 3,
• FIG. 2 shows a schematic sectional view of the exemplary embodiment with the associated visual field sectors
• FIG. 3 shows a more detailed sectional illustration of the exemplary embodiment, from which the arrangement of the various assemblies in a miniaturized housing can be seen.
• a multi-element detector consisting of eight individual pyroelectric sensor elements 1.1 to 1.8 arranged in a row, is initially shown enlarged in detail in the form of an array in plan view.
• the dash-dotted lines indicate the combination of two sensor elements to form a dual detection module.
• the individual, electrically separated sensor elements each have a surface area of the order of magnitude of 0.5 to 2 mm 2 in a square to rectangular configuration. There is a space between each of the elements arranged in a row, which forms a distance of the order of the edge length of the sensor elements.
• the desired geometry of the visual field of this multi-element sensor is determined by the shape and the refractive index of the lens and by the distance of the multi-element sensors from the lens. Due to the selected arrangement, each is assigned to a sensor element Partial image of the area to be monitored, the full sensitivity of the element surface is available, so that movements with high sensitivity can be detected.
• FIG. 2 shows a basic illustration of an exemplary embodiment of the motion detector according to the invention in section.
• the field of view 4 comprises a number of sectors 4.1 to 4.8, movements in the individual sectors each leading to a change in voltage in the associated pyroelectric element 1.1 to 1.8 according to FIG. 1.
• the number of sectors is larger by n-1 than the number of sensor elements, since a non-detected area is provided between the sectors assigned to the individual sensor elements.
• the entire visual field of the device according to the invention which comprises an angular range of 120 ° parallel to the line and an angular range of 8 ° perpendicular to the line, consists of eight smaller visual fields 4.1 to 4.8, all of which have an opening angle of 8 ° and the dark fields in between.
• the visual fields are lined up linearly in the illustrated embodiment. This allows monitoring of an elongated room or an entrance is preferably possible. Has the monitored object If there are also substantial transverse dimensions, a multi-row array can be used accordingly.
• the further electrical assemblies such as preamplifiers, multiplexers, analog / digital converters and evaluation circuits and the associated housing are shown in more detail in FIG.
• the lens 2 is embedded in an otherwise light-tight cuboid housing 5, the flat side of the plano-convex lens 2 being flush with the flat housing surface.
• the aperture 3 is also part of the housing, which has a recess into which the lens is embedded.
• a circuit board 7 which carries the sensor 1.
• the outputs of all sensor elements at the input of an amplifier 8 are combined, which is followed by an analog-digital converter 9, the output signal of which reaches an evaluation circuit 10.
• the output signal of the evaluation circuit is in turn available at contact pins 11 to 14, which are arranged in rows and also form the power supply connections.
• An assembly 15 is provided to stabilize the supply voltage.
• an amplifier can also be arranged downstream of each sensor element. be net, the output signals then being processed further via an additional multiplexer.
• the voltage changes of the pyroelectric elements are then interrogated one after the other by the analog-digital converter and, when an object is detected by a sensor element, a signal indicating an alarm state is emitted at the output.
• FIG. 3 The arrangement shown in FIG. 3 has approximately the size of the housing of a more complex integrated electronic circuit. If necessary, an interference filter 16 (shown in dashed lines) is provided in the area of the opening of the perforated diaphragm 3.
• the invention has created a device which, despite the large detection area, is substantially smaller than conventional passive infrared motion detectors provided with Fresnel lens arrangements or mirror optics and thus can neither be easily identified in the room nor by their installation worsens the aesthetic impression of space.
• the embodiment of the invention is not limited to the preferred exemplary embodiment specified above. Rather, a number of variants are conceivable which make use of the solution shown, even in the case of fundamentally different types.

Applications Claiming Priority (2)

Publications (1)

Family

ID=6420803

Family Applications (1)

Country Status (2)

Cited By (6)

Families Citing this family (3)

Citations (5)

• 1990
  • 1990-12-14 DE DE19904040812 patent/DE4040812A1/de not_active Withdrawn
• 1991
  • 1991-12-16 WO PCT/DE1991/000995 patent/WO1992010819A1/de unknown

Patent Citations (5)

Also Published As

Similar Documents

Legal Events