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GB2056672A - Optical fibre sensor - Google Patents

Optical fibre sensor Download PDF

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Publication number
GB2056672A
GB2056672A GB8025194A GB8025194A GB2056672A GB 2056672 A GB2056672 A GB 2056672A GB 8025194 A GB8025194 A GB 8025194A GB 8025194 A GB8025194 A GB 8025194A GB 2056672 A GB2056672 A GB 2056672A
Authority
GB
United Kingdom
Prior art keywords
fibre
light
detection means
equipment according
cable
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
GB8025194A
Other versions
GB2056672B (en
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.)
GEC TRAFFIC AUTOMATION
Original Assignee
GEC TRAFFIC AUTOMATION
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 GEC TRAFFIC AUTOMATION filed Critical GEC TRAFFIC AUTOMATION
Priority to GB8025194A priority Critical patent/GB2056672B/en
Publication of GB2056672A publication Critical patent/GB2056672A/en
Application granted granted Critical
Publication of GB2056672B publication Critical patent/GB2056672B/en
Expired legal-status Critical Current

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Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01P—MEASURING LINEAR OR ANGULAR SPEED, ACCELERATION, DECELERATION, OR SHOCK; INDICATING PRESENCE, ABSENCE, OR DIRECTION, OF MOVEMENT
    • G01P13/00—Indicating or recording presence, absence, or direction, of movement
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
    • G01D5/00—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable
    • G01D5/26—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light
    • G01D5/32—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light
    • G01D5/34—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells
    • G01D5/353—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells influencing the transmission properties of an optical fibre
    • G01D5/35338—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells influencing the transmission properties of an optical fibre using other arrangements than interferometer arrangements
    • G01D5/35354—Sensor working in reflection
    • G01D5/35367—Sensor working in reflection using reflected light other than backscattered to detect the measured quantity
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01G—WEIGHING
    • G01G19/00—Weighing apparatus or methods adapted for special purposes not provided for in the preceding groups
    • G01G19/02—Weighing apparatus or methods adapted for special purposes not provided for in the preceding groups for weighing wheeled or rolling bodies, e.g. vehicles
    • G01G19/022—Weighing apparatus or methods adapted for special purposes not provided for in the preceding groups for weighing wheeled or rolling bodies, e.g. vehicles for weighing wheeled or rolling bodies in motion
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01G—WEIGHING
    • G01G3/00—Weighing apparatus characterised by the use of elastically-deformable members, e.g. spring balances
    • G01G3/12—Weighing apparatus characterised by the use of elastically-deformable members, e.g. spring balances wherein the weighing element is in the form of a solid body stressed by pressure or tension during weighing
    • G01G3/125—Weighing apparatus characterised by the use of elastically-deformable members, e.g. spring balances wherein the weighing element is in the form of a solid body stressed by pressure or tension during weighing wherein the weighing element is an optical member
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
    • G01L1/00—Measuring force or stress, in general
    • G01L1/24—Measuring force or stress, in general by measuring variations of optical properties of material when it is stressed, e.g. by photoelastic stress analysis using infrared, visible light, ultraviolet
    • G01L1/242—Measuring force or stress, in general by measuring variations of optical properties of material when it is stressed, e.g. by photoelastic stress analysis using infrared, visible light, ultraviolet the material being an optical fibre
    • G01L1/243—Measuring force or stress, in general by measuring variations of optical properties of material when it is stressed, e.g. by photoelastic stress analysis using infrared, visible light, ultraviolet the material being an optical fibre using means for applying force perpendicular to the fibre axis
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01P—MEASURING LINEAR OR ANGULAR SPEED, ACCELERATION, DECELERATION, OR SHOCK; INDICATING PRESENCE, ABSENCE, OR DIRECTION, OF MOVEMENT
    • G01P3/00—Measuring linear or angular speed; Measuring differences of linear or angular speeds
    • G01P3/64—Devices characterised by the determination of the time taken to traverse a fixed distance
    • G01P3/68—Devices characterised by the determination of the time taken to traverse a fixed distance using optical means, i.e. using infrared, visible, or ultraviolet light
    • G—PHYSICS
    • G08—SIGNALLING
    • G08G—TRAFFIC CONTROL SYSTEMS
    • G08G1/00—Traffic control systems for road vehicles
    • G08G1/01—Detecting movement of traffic to be counted or controlled
    • G08G1/015—Detecting movement of traffic to be counted or controlled with provision for distinguishing between two or more types of vehicles, e.g. between motor-cars and cycles
    • G—PHYSICS
    • G08—SIGNALLING
    • G08G—TRAFFIC CONTROL SYSTEMS
    • G08G1/00—Traffic control systems for road vehicles
    • G08G1/01—Detecting movement of traffic to be counted or controlled
    • G08G1/04—Detecting movement of traffic to be counted or controlled using optical or ultrasonic detectors
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
    • B65C—LABELLING OR TAGGING MACHINES, APPARATUS, OR PROCESSES
    • B65C2210/00—Details of manually controlled or manually operable label dispensers
    • B65C2210/0037—Printing equipment
    • B65C2210/004—Printing equipment using printing heads
    • B65C2210/0059—Printing equipment using printing heads using several printing heads

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Geophysics And Detection Of Objects (AREA)

Abstract

For sensing a moving body, including vehicles and personnel, a fibre- optic cable 1 is laid across the path of the moving body and light transmitted through the cable. Pressure of the body on the cable causes variations in the light transmission which can be detected. Different bodies or vehicles may be distinguished by their characteristic transmission loss patterns, axle weights may be measured, or speeds measured if the cable comprises a loop to produce two signals. In the latter case the light is not reflected back down the fibre by a mirror 9, as shown, but the detector is placed at the end of the fibre opposite the end by the source 7. The light may be chopped or modulated sinusoidally. <IMAGE>

Description

SPECIFICATION Moving body sensing This invention relates to moving body sensing equipment and systems incorporating such equipment.
An object of the present invention is to provide a simple, durable, pressure sensitive body detector operative in response to the weight of a body.
According to the present invention, moving-body sensing equipment comprises an optical fibre encased in a protective sheath, source means arranged to transmit light into an end of the fibre, and detection means responsive to the amount of light emerging from an end ofthe fibre to give an indication of a significant change in light transmission through the fibre when the fibre is subjected to a change in pressure due to the imposition or removal of a body compressing the fibre.
It will be appreciated that the term "light" as used in this specification includes all electromagnetic radiation which is transmissible in optical fibres.
The transmission of light through an optical fibre is impeded at any point in the fibre which is mechanically stressed, such as by compression due to the weight of a vehicle or other body bearing upon the cable. Moreover the degree of impedance to light transmission varies with the mechanical stress so that a measurement of the light transmission provides a measure of the mechanical load.
The detection means is preferably responsive to the amount of light that emerges from the fibre in relation to the amount of light that is transmitted into it.
The source means and the detection means may be at opposite ends or at the same end of the fibre, there being provided in the latter case reflecting means at the other end to reflect light emerging from the fibre back into the fibre towards the detection means.
The source means may include means for modulating the light transmitted into the fibre, the detection means then including filter means adapted to select light having this particular modulation.
The optical fibre may be one of a plurality in a cable providing parallel light transmission between the source means and the detection means.
The detection means may include means for distinguishing between different types of vehicles, and means for counting and recording vehicle numbers.
Where the optical fibre is laid in or on a vehicle carriageway transversely to the carriageway the source means and the detection means may be positioned at the side of the carriageway.
In a road vehicle sensing system according to the invention the detection means may include means for indicating and/or recording axle weights.
One embodiment of moving body sensing equipment in accordance with the invention will now be described, by way of example, with reference to the accompanying schematic diagram showing an application to a road vehicle detection system.
In the example shown schematically in the drawing, the fibre cable 1 comprises a single fibre 2 encased in a sheath 3, the sheath 3 being sufficiently tough to withstand the repeated passage of the wheels of road vehicles. Alternatively, the cable may have an inner sheath of conventional form and an outer sheath having the necessary toughness qualities. Clearly, different degrees of durability may be provided according to the nature, number and thickness of the sheaths. The strength of the sheathing must not, however, be such as to prevent any deformation of the optical fibre when subject to typical axle loads.
The cable is laid across a carriageway, preferably located in a groove or slot cut in the surface, or in a groove formed in a mat or pad laid on or fixed to the road surface. The cable must of course protrude sufficiently to permit deformation by a vehicle passing over it, or, alternatively, the walls of the groove may be of such sufficiently soft material that the cable takes the brunt of any load.
One end of the fibre 2 is coupledto a beam splitting device 5 to permit light passing in and out of the fibres to take different paths outside the cable. A source of light, preferably a laser 7, is arranged to transmit a beam of light through the beam splitting device and into the fibre at this end of the cable. The remote end of the cable is coupled to a reflector 9 which reflects any emergent light back down the cable to the source end. On passing through the beam splitting device the emergent light diverges from the path of the source beam and is intercepted by an optical detector 11.
A second beam splitting device 13 in the path of the source beam filters off a fraction of the beam to a second optical detector 15 the output of which provides a reference against which the beam returning from transit of the cable is compared in a comparator circuit 17.
The relation between the two detector outputs, in particular their ratio, can be quantified into a number of bands to provide group indications of axle loadings. For this purpose the comparator circuit 17 imposes various degrees of amplification on the main detector (11, output signal, the amplified signals then being compared with the reference detector (15) output in respective comparator circuits. The lowest-gain circuit to trigger its comparator then indicates the appropriate band in which the main detector(11) output falls.
Since the magnitude of the output signal from detector 11 will vary inversely with the mechanical load on the cable, the lightest load will be indicated by 'tripping' of the comparator in the minimum-gain circuit. This comparator can also be used as a threshold detector for the indication of the passage of any significant vehicle.
A general traffic count can be made by a counter in the circuit 17 operated by this 'lightest-load' threshold detector.
It may be desirable to provide a positive identification between the output signal of the optical detector 11 and the original beam entering the fibre, by modulating the beam and filtering the modulated signal at the detector 11, which then constitutes part of a receiver. Thus the beam source may be chopped, or modulated sinusoidally, and a tuned circuit in the receiver arranged to select only the modulated component of the received light.
In use, the equipment may be operated continuously, e.g. on a public highway, the cable being partially buried in a slot in the road surface. The transmitting and receiving equipment may be mounted by the side of the road together with automatic recording and/or visuai indication equipment.
Alternatively, the equipment may be used in a testing station where a vehicle may be directed over the cable and a record made of the loadings on the various axles.
In a modification of the equipment described above, the light source and sensor may be at opposite ends of the cable with no reflector employed. Higher levels of received signal will of course be obtained with this arrangement for the same length of cable. However, active equipment is required at both ends of the cable and access may be difficult.
An alternative arrangement uses a loop of cable crossing the carriageway twice, the source and receiver equipment again being at the same location but at opposite ends of the cable. With this arrangement, if the 'go' and 'return' lengths of the cable are parallel and spaced a predetermined distance apart, a speed indication can be obtained by timing the pulses of light suppression.
Alternative forms of cable may be employed, for example using multi-fibre cores. A less definite result may be obtained in this way since there will be a range of deformation of the fibres and an averaging effect. There is also an increased risk of damage to the fibres in a multi-fibre cable by close engagement with each other.
Fibres used in this invention preferably have large cores with low minimal aperture.
In an alternative vehicle sensing system, a fibre is supported between adhesive tapes one of which has a rough surface engaging the fibre to accentuate the attenuation effect of mechanical load. The outer faces of the tapes may be coloured to indicate the 'road' and 'face up' surfaces.
In the embodiment mentioned above employing a mat incorporating the fibre, the mat may be of similar form and construction to that described in our Patent No. 1292595.
The cable employed in this invention may be of a form described in co-pending patent application No.
7930093.
In an alternative application of the invention an optical fibre cable is disposed across a pedestrian path to detect their passage. A typical such application would employ a cable extending across a pedestrian crossing in a mat or groove in the road.
The cable would of course have to cross and re-cross at intervals smaller than the length of a 'minimum' footstep to ensure that a footstep could not be missed, and at a sufficient number of intervals to ensure that the cable could not be stepped over completely.

Claims (11)

i CLAIMS
1. - Moving-body sensing equipment comprising an optical fibre encased in a protective sheath, source means arranged to transmit light into an end of the fibre, and detection means responsive to the amount of light emerging from an end of the fibre to give an indication of a significant change in light transmission through the fibre when the fibre is subjected to a change in pressure due to the imposition or removal of a body compressing the fibre.
2. Equipment according to Claim 1, wherein said detection means is responsive to the amount of light that emerges from the fibre in relation to the amount of light that is transmitted into it.
3. Equipment according to Claim 1 or Claim 2, wherein said source means and said detection means are at opposite ends of the fibre.
4. Equipment according to Claim 1 or Claim 2, wherein said source means and said detection means are at the same end of the fibre, there being provided reflecting means at the other end to reflect light emerging from the fibre back into the fibre towards said detection means.
5. Equipment according to any preceding claim wherein said source means includes means for modulating the light transmitted into the fibre and said detection means includes filter means adapted to select light having this particular modulation.
6. Equipment according to any preceding claim wherein said optical fibre may be one of a plurality in a cable providing parallel light transmission be tween said source means and said detection means.
7. Equipment according to any preceding claim, wherein said detection means includes means for distinguishing between different vehicle types.
8. Equipment according to any preceding claim, wherein said detection means includes means for counting and recording vehicle numbers.
9. Avehiclesensing system including equipment according to any preceding claim, wherein said optical fibre is laid in or on a vehicle carriageway transversely to the carriageway said source means and said detection means being positioned at the side of the carriageway.
10. A road vehicle sensing system according to Claim 9, wherein said detection means includes means for indicating and or recording axle weights.
11. A road vehicle sensing system substantially as hereinbefore described with reference to the accompanying drawing.
GB8025194A 1979-08-01 1980-08-01 Optical fibre sensor Expired GB2056672B (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
GB8025194A GB2056672B (en) 1979-08-01 1980-08-01 Optical fibre sensor

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB7926847 1979-08-01
GB8025194A GB2056672B (en) 1979-08-01 1980-08-01 Optical fibre sensor

Publications (2)

Publication Number Publication Date
GB2056672A true GB2056672A (en) 1981-03-18
GB2056672B GB2056672B (en) 1983-07-06

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Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0210372A2 (en) * 1985-05-31 1987-02-04 Sumitomo Electric Industries Limited Optical deformation sensor
FR2585849A1 (en) * 1985-07-30 1987-02-06 Suisse Electro Microtech Centr FIBER OPTIC DETECTION SYSTEM INCORPORATING AN INTENSITY MODULATION SENSOR
GB2250813A (en) * 1990-12-15 1992-06-17 British Aerospace Weighing apparatus for vehicles
DE4423104A1 (en) * 1994-07-01 1996-01-04 Leon Helma Christina Pressure sensitive sensor system
WO2001027569A1 (en) * 1999-10-12 2001-04-19 Future Fibre Technologies Pty Ltd Vehicle weigh-in-motion method and system
EP2965052A4 (en) * 2013-03-04 2016-12-07 Int Road Dynamics Inc System and method for measuring moving vehicle information using electrical time domain reflectometry
WO2019033185A1 (en) 2017-08-16 2019-02-21 Velsis Sistemas E Tecnologia Viaria S/A Dynamic weighing and speed monitoring system for vehicles on a road
WO2022187922A1 (en) * 2021-03-10 2022-09-15 Velsis Sistemas E Tecnologia Viaria S.A. System for weighing moving motor vehicles based on flexible sensors and fibre optics

Cited By (15)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0210372A2 (en) * 1985-05-31 1987-02-04 Sumitomo Electric Industries Limited Optical deformation sensor
EP0210372A3 (en) * 1985-05-31 1989-01-25 Sumitomo Electric Industries Limited Optical deformation sensor
FR2585849A1 (en) * 1985-07-30 1987-02-06 Suisse Electro Microtech Centr FIBER OPTIC DETECTION SYSTEM INCORPORATING AN INTENSITY MODULATION SENSOR
EP0211804A1 (en) * 1985-07-30 1987-02-25 Centre Suisse D'electronique Et De Microtechnique S.A. Fibre-optical detection system incorporating an intensity modulation sensor
US4887901A (en) * 1985-07-30 1989-12-19 Centre Suisse D'electronique Et De Microtechnique S.A. Optical fiber detection system using an intensity-modulating sensor
GB2250813A (en) * 1990-12-15 1992-06-17 British Aerospace Weighing apparatus for vehicles
DE4423104A1 (en) * 1994-07-01 1996-01-04 Leon Helma Christina Pressure sensitive sensor system
WO2001027569A1 (en) * 1999-10-12 2001-04-19 Future Fibre Technologies Pty Ltd Vehicle weigh-in-motion method and system
EP2965052A4 (en) * 2013-03-04 2016-12-07 Int Road Dynamics Inc System and method for measuring moving vehicle information using electrical time domain reflectometry
EP2965300A4 (en) * 2013-03-04 2017-01-04 International Road Dynamics, Inc. Sensor including electrical transmission-line parameter that changes responsive to vehicular load
JP2018119992A (en) * 2013-03-04 2018-08-02 インターナショナル・ロード・ダイナミクス・インコーポレイテッドＩｎｔｅｒｎａｔｉｏｎａｌ Ｒｏａｄ Ｄｙｎａｍｉｃｓ Ｉｎｃ． System and method for measuring moving vehicle information using electrical time domain reflectometry
US10859430B2 (en) 2013-03-04 2020-12-08 International Road Dynamics Sensor including electrical transmission-line parameter that changes responsive to vehicular load
WO2019033185A1 (en) 2017-08-16 2019-02-21 Velsis Sistemas E Tecnologia Viaria S/A Dynamic weighing and speed monitoring system for vehicles on a road
US10861328B2 (en) 2017-08-16 2020-12-08 Velsis Sistemas E Tecnologia Viaria S/A System for monitoring dynamic weighing and speed of vehicles on lanes
WO2022187922A1 (en) * 2021-03-10 2022-09-15 Velsis Sistemas E Tecnologia Viaria S.A. System for weighing moving motor vehicles based on flexible sensors and fibre optics

Also Published As

Publication number Publication date
GB2056672B (en) 1983-07-06

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