EP1198702A4 - Apparatus and method for gas sensing - Google Patents

Apparatus and method for gas sensing

Info

Publication number
EP1198702A4
EP1198702A4 EP00942591A EP00942591A EP1198702A4 EP 1198702 A4 EP1198702 A4 EP 1198702A4 EP 00942591 A EP00942591 A EP 00942591A EP 00942591 A EP00942591 A EP 00942591A EP 1198702 A4 EP1198702 A4 EP 1198702A4
Authority
EP
European Patent Office
Prior art keywords
hght
gas
photodetector
source
optical fibre
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Withdrawn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
EP00942591A
Other languages
German (de)
French (fr)
Other versions
EP1198702A1 (en
Inventor
Andrew Wilson
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.)
Otago Innovation Ltd
Original Assignee
University of Otago
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 University of Otago filed Critical University of Otago
Publication of EP1198702A1 publication Critical patent/EP1198702A1/en
Publication of EP1198702A4 publication Critical patent/EP1198702A4/en
Withdrawn legal-status Critical Current

Links

Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
    • G01N21/25—Colour; Spectral properties, i.e. comparison of effect of material on the light at two or more different wavelengths or wavelength bands
    • G01N21/31—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry
    • G01N21/35—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry using infrared light
    • G01N21/3504—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry using infrared light for analysing gases, e.g. multi-gas analysis
    • G—PHYSICS
    • G08—SIGNALLING
    • G08B—SIGNALLING OR CALLING SYSTEMS; ORDER TELEGRAPHS; ALARM SYSTEMS
    • G08B17/00—Fire alarms; Alarms responsive to explosion
    • G08B17/10—Actuation by presence of smoke or gases, e.g. automatic alarm devices for analysing flowing fluid materials by the use of optical means
    • G08B17/103—Actuation by presence of smoke or gases, e.g. automatic alarm devices for analysing flowing fluid materials by the use of optical means using a light emitting and receiving device
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
    • G01N2021/1793—Remote sensing
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
    • G01N21/25—Colour; Spectral properties, i.e. comparison of effect of material on the light at two or more different wavelengths or wavelength bands
    • G01N21/31—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry
    • G01N21/39—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry using tunable lasers
    • G01N2021/391—Intracavity sample
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2201/00—Features of devices classified in G01N21/00
    • G01N2201/08—Optical fibres; light guides

Definitions

  • the invention relates to an optical fibre delivery system for apparatus and method for sensing properties of a gas such as concentration or temperature by reference to the attenuation of light passing through the gas (trace gas sensing) .
  • the invention comprises apparatus for remote gas sensing comprising a photodetector and a gas cell containing a gas or zone through which the gas passes and through which light from a light source passes and is reflected back to the photodetector, wherein the light source and photodetector, and the gas cell, are connected by a single polarisation preserving optical fibre through which light from the source passes to the gas cell, with Hght reflected back from the cell passing back through the optical fibre with a different polarisation to the transmitted light.
  • the apparatus of the invention more specifically comprises a light source, a gas cell or zone, a photodetector to receive light reflected back from the gas cell, a single polarisation preserving optical fibre connecting the light source and photodetector to the gas cell, means to polarise return light exiting the gas so that it re-enters the optical fibre polarised orthogonal to the transmitted light, and means at the other end of the optical fibre to split the return light from the transmitted light and direct the return hght to the photodetector.
  • the invention comprises a method for remote gas sensing utilising a photodetector and a gas cell or zone containing the gas or through which the gas passes and through which light from a source passes and is reflected back to the photodetector, including passing light from the source to the gas cell and back to the photodetector via a single polarisation preserving optical fibre such that the return light passes through the optical fibre with a different polarisation to that of the transmitted light.
  • the light source and photodetector are connected to the gas cell or zone via an arrangement including a polarisation preserving optical fibre which carries the transmitted and reflected light with different polarisations, which enables the photodetector and gas cell or zone to be remotely positioned from one another.
  • the photodetector and associated electronics do not need to be positioned close to the gas cell or zone.
  • the use of different polarisation for transmitted and reflected hght eliminates unwanted optical interference, and enables separation of reflected from transmitted light for optical detection.
  • a polarising beam splitter 1 which is oriented to linearly polarise the Hght parallel to one of the two polarisation maintaining axis of a polarisation preserving single-mode optical fibre 2.
  • the Hght is launched into the polarisation preserving fibre by a lens 3, and propagates through the optical fibre rnaintaining its polarisation state.
  • the Hght Upon exiting the fibre, the Hght is colHmated by a second lens 4, and propagates through a gas sample region or ceU 5, in a double pass configuration using a quarter- wave retarder 6 and retro-reflecting mirror 7. Some of the Hght is absorbed by the gas as it propagates through the gas ample, and this is used to determine properties of the sample, such as concentration and temperature.
  • Quarter-wave retarder 6 is oriented to change the polarisation state of the transmitted Hght from linear to pure circular. After retro-reflection by the mirror 7, the return Hght then passes back through the quarter- wave retarder 6, which changes the polarisation state of the Hght from circular back to linear, but with an orientation perpendicular to that of the forward propagating (transmitted) Hght.
  • the mirror 7 is aHgned so that the reflected Hght is launched back into the fibre, but because it is linearly polarised perpendicular to the forward propagating Hght, the reflecte ⁇ Hght is polarised paraUel to the other polarisation preserving axis of the optical fibre. This means that the forward and retro-reflected Hght propagates simultaneously through the optical fibre, but they have orthogonal linear polarisation states.
  • the retro-reflected Hght Upon exiting the fibre, the retro-reflected Hght is separated from the forward propagating Hght by the polarising beam spHtter 1 , and directed to the photodetector where its intensity is measured.
  • iHustrated is described by way of example.
  • Alternative arrangements utiHsed in the concept of the invention are possible.
  • Hght exiting the optical fibre may be aUowed to diverge by removing the collimating lens 4, and then retro-reflected using a spherical mirror placed a small distance equal to the radius of curvature of the mirror.
  • separate optical components may be replaced by thin film or optical fibre based elements.
  • the gas sample region or ceU 5 may be positioned in a hostile environment (for example hot or toxic), a cramped environment (for example within a compact machine), or a very distant location (for example on top of a smoke stack).
  • a hostile environment for example hot or toxic
  • a cramped environment for example within a compact machine
  • a very distant location for example on top of a smoke stack

Landscapes

  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Analytical Chemistry (AREA)
  • Spectroscopy & Molecular Physics (AREA)
  • Chemical & Material Sciences (AREA)
  • Emergency Management (AREA)
  • Business, Economics & Management (AREA)
  • Health & Medical Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Biochemistry (AREA)
  • General Health & Medical Sciences (AREA)
  • Immunology (AREA)
  • Pathology (AREA)
  • Investigating Or Analysing Materials By Optical Means (AREA)

Abstract

An apparatus for remote gas sensing comprises a light source, a polarising beam splitter (1), a photodetector, a single polarisation preserving optical fibre (2), a gas cell (5) or a zone through which the gas passes, a quarter-wave plate (6) and a mirror (7). A light beam from the light source passes through the beam splitter (1) and is focused by a lens (3) into the fibre (2) where it travels maintaining its polarisation state. Upon exiting the fibre (2), the light is collimated by a second lens (4) and propagates through the gas cell (5) and the quarter-wave plate (6) in a double pass configuration being retro-reflected by the mirror (7). The light beams is then focused back into the fibre (2) where it propagates with a polarisation state which is perpendicular to that of the forward propagating light. When light emerges from the fibre (2), it is reflected by the beam splitter (1) onto the photodetector.

Description

APPARATUS AND METHOD FOR GAS SENSING
FIELD OF INVENTION
The invention relates to an optical fibre delivery system for apparatus and method for sensing properties of a gas such as concentration or temperature by reference to the attenuation of light passing through the gas (trace gas sensing) .
SUMMARY OF INVENTION
In broad terms in one aspect the invention comprises apparatus for remote gas sensing comprising a photodetector and a gas cell containing a gas or zone through which the gas passes and through which light from a light source passes and is reflected back to the photodetector, wherein the light source and photodetector, and the gas cell, are connected by a single polarisation preserving optical fibre through which light from the source passes to the gas cell, with Hght reflected back from the cell passing back through the optical fibre with a different polarisation to the transmitted light.
In one form the apparatus of the invention more specifically comprises a light source, a gas cell or zone, a photodetector to receive light reflected back from the gas cell, a single polarisation preserving optical fibre connecting the light source and photodetector to the gas cell, means to polarise return light exiting the gas so that it re-enters the optical fibre polarised orthogonal to the transmitted light, and means at the other end of the optical fibre to split the return light from the transmitted light and direct the return hght to the photodetector.
In broad terms in another aspect the invention comprises a method for remote gas sensing utilising a photodetector and a gas cell or zone containing the gas or through which the gas passes and through which light from a source passes and is reflected back to the photodetector, including passing light from the source to the gas cell and back to the photodetector via a single polarisation preserving optical fibre such that the return light passes through the optical fibre with a different polarisation to that of the transmitted light. In the apparatus and method of the invention the light source and photodetector are connected to the gas cell or zone via an arrangement including a polarisation preserving optical fibre which carries the transmitted and reflected light with different polarisations, which enables the photodetector and gas cell or zone to be remotely positioned from one another. The photodetector and associated electronics do not need to be positioned close to the gas cell or zone. The use of different polarisation for transmitted and reflected hght eliminates unwanted optical interference, and enables separation of reflected from transmitted light for optical detection.
BRIEF DESCRIPTION OF THE DRAWING
The accompanying drawing schematically illustrates one preferred arrangement of gas sensing apparatus, by way of example.
DETAILED DESCRIPTION OF PREFERRED FORM
Light from a source such as a laser passes through a polarising beam splitter 1 which is oriented to linearly polarise the Hght parallel to one of the two polarisation maintaining axis of a polarisation preserving single-mode optical fibre 2. The Hght is launched into the polarisation preserving fibre by a lens 3, and propagates through the optical fibre rnaintaining its polarisation state.
Upon exiting the fibre, the Hght is colHmated by a second lens 4, and propagates through a gas sample region or ceU 5, in a double pass configuration using a quarter- wave retarder 6 and retro-reflecting mirror 7. Some of the Hght is absorbed by the gas as it propagates through the gas ample, and this is used to determine properties of the sample, such as concentration and temperature.
Quarter-wave retarder 6 is oriented to change the polarisation state of the transmitted Hght from linear to pure circular. After retro-reflection by the mirror 7, the return Hght then passes back through the quarter- wave retarder 6, which changes the polarisation state of the Hght from circular back to linear, but with an orientation perpendicular to that of the forward propagating (transmitted) Hght. The mirror 7 is aHgned so that the reflected Hght is launched back into the fibre, but because it is linearly polarised perpendicular to the forward propagating Hght, the reflecteα Hght is polarised paraUel to the other polarisation preserving axis of the optical fibre. This means that the forward and retro-reflected Hght propagates simultaneously through the optical fibre, but they have orthogonal linear polarisation states.
Upon exiting the fibre, the retro-reflected Hght is separated from the forward propagating Hght by the polarising beam spHtter 1 , and directed to the photodetector where its intensity is measured.
The preferred form iHustrated is described by way of example. Alternative arrangements utiHsed in the concept of the invention are possible. For example in an alternative arrangement Hght exiting the optical fibre may be aUowed to diverge by removing the collimating lens 4, and then retro-reflected using a spherical mirror placed a small distance equal to the radius of curvature of the mirror. In addition, separate optical components may be replaced by thin film or optical fibre based elements.
The gas sample region or ceU 5 may be positioned in a hostile environment (for example hot or toxic), a cramped environment (for example within a compact machine), or a very distant location (for example on top of a smoke stack).
The foregoing describes the invention including a preferred form thereof. Alterations and modifications as wul be obvious to those skilled in the art are intended to be incorporated within the scope hereof as defined in the accompanying claims.

Claims

1. An apparatus for remote gas sensing comprising a Hght source, a photodetector, a gas ceU containing gas or a zone through which the gas passes and through which Hght from the Hght source passes and is reflected back to the photodetector, wherein the Hght source, photodetector and gas ceU are connected by a single polarisation preserving optical fibre through which Hght from the Hght source passes to the gas cell, which Hght reflected back from the ceU passes back through the optical fibre with a different polarisation to that to the Hght transmitted by the Hght source.
2. An apparatus according to claim 1 further comprising means to polarise the returned Hght exiting the gas so that it re-enters the optical fibre polarised orthogonal to the transmitted Hght.
3. An apparatus according to either one of claims 1 and 2 further comprising means between the Hght source and the optical fibre arranged to spHt the returned Hght from the transmitted Hght and direct the returned Hght to the photodetector.
4. An apparatus according to any one of claims 1 to 3 wherein the Hght source and photodetector are positioned remotely to the gas ceU or zone.
5. A method for remote gas sensing utiHsing a Hght source, a photodetector and a gas ceU or zone containing gas or through which gas passes and through which Hght from the Hght source passes and is reflected back to the photodetector, including passing Hght from the source to the gas ceU and back to the photodetector via a single polarisation preserving optical fibre such that the return Hght passes through the optical fibre with a different polarisation to that of the transmitted Hght.
6. A method according to claim 5 further comprising polarising the returned
Hght exiting the gas so that it re-enters the optical fibre polarised orthogonal to the transmitted Hght.
7. A method according to either one of claims 5 and 6 further comprising spHtting, between the Hght source and the optical fibre, the returned Hght from the transmitted Hght and directing the returned Hght to the photodetector.
8. A method according to any one of claims 5 to 7 wherein the Hght source and photodetector are positioned remotely to the gas ceU or zone.
9. An apparatus for remote gas sensing, substantiaHy as herein described with reference to the accompanying drawing.
10. A method for remote gas sensing, substantiaHy as herein described with reference to the accompany drawing.
EP00942591A 1999-07-02 2000-07-03 Apparatus and method for gas sensing Withdrawn EP1198702A4 (en)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
NZ33655299 1999-07-02
NZ33655299 1999-07-02
PCT/NZ2000/000118 WO2001002838A1 (en) 1999-07-02 2000-07-03 Apparatus and method for gas sensing

Publications (2)

Publication Number Publication Date
EP1198702A1 EP1198702A1 (en) 2002-04-24
EP1198702A4 true EP1198702A4 (en) 2005-02-02

Family

ID=19927362

Family Applications (1)

Application Number Title Priority Date Filing Date
EP00942591A Withdrawn EP1198702A4 (en) 1999-07-02 2000-07-03 Apparatus and method for gas sensing

Country Status (3)

Country Link
EP (1) EP1198702A4 (en)
AU (1) AU768639B2 (en)
WO (1) WO2001002838A1 (en)

Families Citing this family (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN100403347C (en) * 2004-09-18 2008-07-16 清华大学深圳研究生院 Interference photoelectric smoke and fire detecting method and its device
CN100465505C (en) * 2006-03-07 2009-03-04 南开大学 Watt-grade broadband super-fluorescence light source with ytterbium doped photonic crystal fiber
EP2571117A1 (en) 2011-09-15 2013-03-20 Axetris AG Laser unit with reduced back reflection
EP2720326A1 (en) 2013-03-12 2014-04-16 Axetris AG Gas detection laser light source with reduced optical feedback
EP3321907B1 (en) * 2016-11-11 2023-12-27 Kidde Technologies, Inc. Fiber optic based smoke and/or overheat detection and monitoring for aircraft
CN111815924B (en) * 2020-08-21 2022-06-07 中国民用航空飞行学院 Thermal disaster early warning system and method for power lithium battery of all-electric drive fire truck in airport

Family Cites Families (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4516432A (en) * 1983-10-13 1985-05-14 Nihon Kagaku Kogyo Co., Ltd. Apparatus for measuring two-phase flow
US4824251A (en) * 1987-09-25 1989-04-25 Digital Signal Corporation Optical position sensor using coherent detection and polarization preserving optical fiber
FR2666163B1 (en) * 1990-08-22 1995-03-17 Bertin & Cie OPTO-ELECTRONIC DEVICE FOR DETECTING SMOKE OR GAS SUSPENDED IN AIR.
JPH09282577A (en) * 1996-04-11 1997-10-31 Tokyo Gas Co Ltd Gas detector
US6050656A (en) * 1997-10-23 2000-04-18 University Of North Carolina At Charlotte Optical based opacity and flow monitoring system and method of monitoring opacity and flow

Non-Patent Citations (2)

* Cited by examiner, † Cited by third party
Title
No further relevant documents disclosed *
See also references of WO0102838A1 *

Also Published As

Publication number Publication date
AU768639B2 (en) 2003-12-18
WO2001002838A1 (en) 2001-01-11
AU5719400A (en) 2001-01-22
EP1198702A1 (en) 2002-04-24

Similar Documents

Publication Publication Date Title
US5648848A (en) Beam delivery apparatus and method for interferometry using rotatable polarization chucks
US6819432B2 (en) Coherent detecting receiver using a time delay interferometer and adaptive beam combiner
EP0137966B1 (en) Optical device for detecting coded symbols
US7356207B2 (en) Method and system for adjusting the sensitivity of optical sensors
US7498561B2 (en) Arrangement for the detection of illumination radiation in a laser scanning microscope
CN103411919A (en) System and method for simultaneously monitoring multiple components of building fire early-stage characteristic gases
KR20090104812A (en) Multi Mode Fibre Perturber
JPH09325005A (en) Device for measuring deflection
CN112484648A (en) Displacement measurement system and method for heterodyne optical fiber interferometer
EP0431792A2 (en) Laser interferometer
WO2001002838A1 (en) Apparatus and method for gas sensing
JPH0329802A (en) Interferometer
US6181429B1 (en) Interferometer for measurements of optical properties in bulk samples
US7173706B2 (en) Apparatus and method for gas sensing
KR102280189B1 (en) Lidar apparatus
US4832492A (en) Heterodyne michelson interferometer for polarization measurements
US20030043467A1 (en) Polarization delay unit
EP0924507A1 (en) Interferometer for measurements of optical properties in bulk samples
JP2592254B2 (en) Measuring device for displacement and displacement speed
CA2257034A1 (en) Interferometer for measurements of optical properties in bulk samples
GB2233087A (en) Apparatus for monitoring a gas or a flame
SU1075814A1 (en) Method of measuring linear velocity of object and fibre-optical meter of linear velocity
CN104976966A (en) Laser three-dimensional scanning system
JPH11101608A (en) Laser-interfered length measuring machine
KR20140029237A (en) Sensor for capturing a moving material web

Legal Events

Date Code Title Description
PUAI Public reference made under article 153(3) epc to a published international application that has entered the european phase

Free format text: ORIGINAL CODE: 0009012

17P Request for examination filed

Effective date: 20020131

AK Designated contracting states

Kind code of ref document: A1

Designated state(s): AT BE CH CY DE DK ES FI FR GB GR IE IT LI LU MC NL PT SE

AX Request for extension of the european patent

Free format text: AL;LT;LV;MK;RO;SI

A4 Supplementary search report drawn up and despatched

Effective date: 20041221

RAP1 Party data changed (applicant data changed or rights of an application transferred)

Owner name: OTAGO INNOVATION LIMITED

STAA Information on the status of an ep patent application or granted ep patent

Free format text: STATUS: THE APPLICATION IS DEEMED TO BE WITHDRAWN

18D Application deemed to be withdrawn

Effective date: 20060915