GB2219656A - Sensor for sensing the light absorption of a gas - Google Patents
Sensor for sensing the light absorption of a gas Download PDFInfo
- Publication number
- GB2219656A GB2219656A GB8813775A GB8813775A GB2219656A GB 2219656 A GB2219656 A GB 2219656A GB 8813775 A GB8813775 A GB 8813775A GB 8813775 A GB8813775 A GB 8813775A GB 2219656 A GB2219656 A GB 2219656A
- Authority
- GB
- United Kingdom
- Prior art keywords
- light
- gas
- sensor
- sensing
- 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.)
- Granted
Links
- 230000031700 light absorption Effects 0.000 title claims abstract description 16
- 239000013307 optical fiber Substances 0.000 claims abstract description 23
- 230000003287 optical effect Effects 0.000 claims abstract description 11
- 239000000835 fiber Substances 0.000 claims description 3
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 abstract description 4
- 239000007789 gas Substances 0.000 description 18
- 238000000034 method Methods 0.000 description 4
- 238000005259 measurement Methods 0.000 description 3
- 238000010521 absorption reaction Methods 0.000 description 1
- 230000001419 dependent effect Effects 0.000 description 1
- 238000009792 diffusion process Methods 0.000 description 1
- 239000011521 glass Substances 0.000 description 1
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
- 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
- G01N21/01—Arrangements or apparatus for facilitating the optical investigation
- G01N21/03—Cuvette constructions
- G01N21/031—Multipass arrangements
- G01N2021/0314—Double pass, autocollimated path
-
- 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
- G01N2021/3513—Open path with an instrumental source
-
- 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
- G01N21/84—Systems specially adapted for particular applications
- G01N21/85—Investigating moving fluids or granular solids
- G01N2021/8578—Gaseous flow
-
- 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
- G01N2201/0833—Fibre array at detector, resolving
-
- 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
- G01N2201/084—Fibres for remote transmission
Abstract
A sensor for sensing the light absorption of a gas, the sensor comprising a light source 2 and a light detector 4 both of which are optically coupled to an optical fibre 20 along which light is to be transmitted and received. The optical fibre is optically coupled by means of a collimating lens 8 to an optical path extending through a region 12 of the gas, the optical path extending between the collimating lens and a retroreflector 10. A plurality of the sensors may be optically coupled to a common optical fibre to enable sensing of a plurality of regions using, e.g. time-division multiplexing. The sensor may sense the concentration of methane. <IMAGE>
Description
SENSORS
The present invention relates to a sensor and more particularly to a sensor for sensing the light absorption of a gas.
A known sensor is illustrated in Figure 1. The sensor comprises a light source 2 and a light detector 4 both of which are optically coupled by a beamsplitter 6 to a collimating lens assembly 8. The collimating lens assembly 8 provides a parallel beam of light to a retroreflector 10, the space between the collimating lens assembly 8 and the retroreflector 10 defining a region 12 for the gas. This arrangement has the disadvantage that the light source 2 and the light detector 4 have to be very precisely located in terms of not only
the distance from the collimating lens 8 but also in their lateral positions.
One of the objectives of the present invention is to provide a
sensor in which the locations of the light source and the light
detector are not dependent on their distance from the collimating
lens.
According to the present invention there is provided a sensor
for sensing the light absorption of a gas, the sensor comprising a light
source and a light detector both of which are optically coupled to an
optical fibre along which light is to be transmitted and received, the
optical fibre being optically coupled by means of a collimating lens to
an optical path extending through a region for the gas, the optical
path extending between the collimating lens and a retro- reflector.
In one embodiment the light source and the light detector are
optically coupled to the optical fibre by means of a fibre coupler. In another embodiment the light source and the light detector are optically coupled to the optical fibre by means of a beam splitter and a lens assembly.
There is also provided a system for sensing the light absorption of a gas, the system incorporating a sensor in accordance with embodiments of the present invention. The system comprises a plurality of gas sensing regions each of which is optically coupled to the optical fibre, and processing means provided for receiving the output from the light detector to provide output signals representative of light absorption in each of the gas sensing regions.
The invention will be described further, by way of examples, with reference to the accompanying drawings in which:
Figure 2 is a schematic illustration of a sensor according to one embodiment of the present invention,
Figure 3 is a schematic illustration of a sensor according to a second embodiment, and
Figure 4 is a schematic illustration of a system for sensing the light absorption of gases at different regions.
Features illustrated in Figures 2 and 3 which are the same as features already described above with reference to Figure 1 have been designated by identical reference numerals.
Referring to Figure 2 the light source 2 and the light detector 4 are each connected by respective optical fibres 14 and 16 to an end of a standard fibre directional coupler 18 having a 3dB splitting ratio.
The other end of the coupler 18 is connected to an optical fibre 20 which is optically coupled to the collimating lens assembly 8. The light from the optical fibre 20 is collimated by the lens assembly 8 and travels through the region 12 to the retroreflector 10. The reflected light from the retroreflector 10 returns through the region 12 to the collimating lens assembly 8 and is focussed onto the end of the optical fibre 20. The use of the retroreflector 10 ensures that the beam deviation is small and that the returning light is therefore accurately focussed onto the end of the optical fibre 20. The only precise adjustment required is the focussing of the collimator lens assembly.
The ends of the optical fibre 20 can be anti-reflection coated or have anti-reflection coated glass plates bonded to them to reduce reflection at those interfaces.
The embodiment illustrated in Figure 3 differs from that of
Figure 2 in that the transmit/receive part of the arrangement is replaced by the beamsplitter 6 and a lens assembly 22. The lens assembly 22 serves to focus the transmitted light from the light transmitter 2 onto the end of the optical fibre 20 and focuses the received light from the optical fibre 20 onto the light detector 4.
The sensors described above are used for absorption measurements of gases. For example, the sensors can be employed for methane (or other) gas sensing, in which the absorption of light due to the gas enables its concentration to be monitored. A measurement cell for the gas is illustrated by the region 12 in the figures. The measurement cell may be an open cell as shown in the figures, operating across a-free-space sensing region or it may be enclosed by, for example a cylindrica] housing (not shown). Gas may, in the latter case, be pumped in via input and output nozzles in the cylindrical housing or may, if the housing is porous to gas, be allowed to enter via gas diffusion.
Whereas Figures 2 and 3 illustrate two embodiments of the present invention there are many other embodiments which would be understood by a person skilled in the art to fall within the scope of the invention. For example the corner cube retroreflector 10 could be replaced by a lens and focal plane reflector or a sphere-lens "catseye" type of reflector may be employed.
Figure 4 illustrates a system in which three gas sensing regions 24, 26, 28 can be scanned using a time division multiplexing technique. Each of the regions 24, 26, 28 are optically coupled by respective optical fibres to the single common optical fibre 20. The optical fibre 20 is connected via the 3dB coupler 18 to the pulsed light source 2 and the light detector 4. A scannable light filter 36 may be positioned in the optical path between the coupler 18 and either the light detector 4 or the light source 2 in order to attenuate the transmitted or received light in a predetermined manner.
The optical paths to each of the sensing regions 24, 26. 28 are of different lengths so the gas in each regions can be analysed by a variety of possible methods. In Figure 4 for example the output from the light detector 4 is fed to a processor 40 which includes a time domain demultiplexor. The processor 40 provides a plurality of signal outputs representative of the absorption of light in each of the three gas sensing regions 24, 26, 28.
It will be appreciated that alternative techniques may be adopted in the system of Figure 4. Other well known radar methods may be employed such as for example FMCW, Pseudo-random coding and chirped carrier signal.
Claims (7)
1. A sensor for sensing the light absorption of a gas, the sensor comprising a light source and a light detector both of which are optically coupled to an optical fibre along which light is to be transmitted and received, the optical fibre being optically coupled by means of a collimating lens to an optical path extending through a region for the gas, the optical path extending between the collimating lens and a retro-reflector.
2. A sensor for sensing the light absorption of a gas as claimed in claim 1 wherein the light source and the light detector are optically coupled to the optical fibre by a directional fibre coupler.
3. A sensor for sensing the light absorption of a gas as claimed in claim 1 wherein the light source and the light detector are optically coupled to the optical fibre by means of a beam splitter and a lens assembly.
4. A sensor for sensing the light absorption of a gas, the sensor being substantially as hereinbefore described with reference to and as illustrated in Figure 2 or Figure 3 of the accompanying drawings.
5. A system for sensing the light absorption of a gas and incorporating a sensor according to any one of claims 1 to 4 wherein the system comprises a plurality of gas sensing regions each of which is optically coupled to the optical fibre, and processing means provided for receiving the output from the light detector to provide output signals representative of the light absorption in each of the gas sensing regions.
6. A system as claimed in claim 5 wherein a scannable light filter is provided in the optical path between the optical fibre and either the light detector or the light source.
7. A system for sensing the light absorption of a gas, the system being substantially as hereinbefore particularly described with reference to Figure 4 of the accompanying drawings.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB8813775A GB2219656B (en) | 1988-06-10 | 1988-06-10 | Sensors |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB8813775A GB2219656B (en) | 1988-06-10 | 1988-06-10 | Sensors |
Publications (3)
| Publication Number | Publication Date |
|---|---|
| GB8813775D0 GB8813775D0 (en) | 1988-07-13 |
| GB2219656A true GB2219656A (en) | 1989-12-13 |
| GB2219656B GB2219656B (en) | 1992-01-29 |
Family
ID=10638423
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB8813775A Expired - Fee Related GB2219656B (en) | 1988-06-10 | 1988-06-10 | Sensors |
Country Status (1)
| Country | Link |
|---|---|
| GB (1) | GB2219656B (en) |
Cited By (11)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE4133131C1 (en) * | 1991-10-05 | 1993-02-18 | Ultrakust Electronic Gmbh, 8375 Gotteszell, De | Detecting chemical or physical parameters influencing light intensity - using reference and measurement receivers to detect reference and measurement light of respective wavelength components, in synchronism |
| GB2274163A (en) * | 1993-01-12 | 1994-07-13 | Pollution Monitor Syst Ltd | Gas analyser |
| US5572031A (en) * | 1994-11-23 | 1996-11-05 | Sri International | Pressure- and temperature-compensating oxygen sensor |
| WO1999044039A1 (en) * | 1998-02-26 | 1999-09-02 | Simrad Optronics Asa | Sensor system |
| GB2438724A (en) * | 2006-06-02 | 2007-12-05 | Tq Environmental Plc | Gas monitoring system |
| EP2065738A1 (en) * | 2007-12-01 | 2009-06-03 | Smiths Group PLC | Optical apparatus |
| DE102010062027A1 (en) * | 2010-11-26 | 2012-05-31 | Siemens Aktiengesellschaft | Measurement setup for optical absorption spectroscopy |
| CN108872615A (en) * | 2018-04-26 | 2018-11-23 | 迪瑞医疗科技股份有限公司 | A kind of manifold type blood coagulation test macro and method |
| WO2022266688A1 (en) * | 2021-06-25 | 2022-12-29 | Avl List Gmbh | Device for measuring at least one gaseous or solid material |
| WO2022266693A1 (en) * | 2021-06-25 | 2022-12-29 | Avl List Gmbh | Measuring unit for measuring a gaseous or solid material in a measurement volume |
| WO2022266690A1 (en) * | 2021-06-25 | 2022-12-29 | Avl List Gmbh | Measuring unit and method for measuring at least one gaseous or solid material |
-
1988
- 1988-06-10 GB GB8813775A patent/GB2219656B/en not_active Expired - Fee Related
Cited By (14)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE4133131C1 (en) * | 1991-10-05 | 1993-02-18 | Ultrakust Electronic Gmbh, 8375 Gotteszell, De | Detecting chemical or physical parameters influencing light intensity - using reference and measurement receivers to detect reference and measurement light of respective wavelength components, in synchronism |
| GB2274163A (en) * | 1993-01-12 | 1994-07-13 | Pollution Monitor Syst Ltd | Gas analyser |
| GB2274163B (en) * | 1993-01-12 | 1996-11-20 | Pollution Monitor Syst Ltd | Gas analyser |
| US5572031A (en) * | 1994-11-23 | 1996-11-05 | Sri International | Pressure- and temperature-compensating oxygen sensor |
| WO1999044039A1 (en) * | 1998-02-26 | 1999-09-02 | Simrad Optronics Asa | Sensor system |
| GB2438724B (en) * | 2006-06-02 | 2010-03-03 | Tq Environmental Plc | Gas monitoring system |
| GB2438724A (en) * | 2006-06-02 | 2007-12-05 | Tq Environmental Plc | Gas monitoring system |
| EP2065738A1 (en) * | 2007-12-01 | 2009-06-03 | Smiths Group PLC | Optical apparatus |
| DE102010062027A1 (en) * | 2010-11-26 | 2012-05-31 | Siemens Aktiengesellschaft | Measurement setup for optical absorption spectroscopy |
| CN108872615A (en) * | 2018-04-26 | 2018-11-23 | 迪瑞医疗科技股份有限公司 | A kind of manifold type blood coagulation test macro and method |
| CN108872615B (en) * | 2018-04-26 | 2021-08-06 | 迪瑞医疗科技股份有限公司 | Coupling type blood coagulation testing system and method |
| WO2022266688A1 (en) * | 2021-06-25 | 2022-12-29 | Avl List Gmbh | Device for measuring at least one gaseous or solid material |
| WO2022266693A1 (en) * | 2021-06-25 | 2022-12-29 | Avl List Gmbh | Measuring unit for measuring a gaseous or solid material in a measurement volume |
| WO2022266690A1 (en) * | 2021-06-25 | 2022-12-29 | Avl List Gmbh | Measuring unit and method for measuring at least one gaseous or solid material |
Also Published As
| Publication number | Publication date |
|---|---|
| GB2219656B (en) | 1992-01-29 |
| GB8813775D0 (en) | 1988-07-13 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| 732 | Registration of transactions, instruments or events in the register (sect. 32/1977) | ||
| PCNP | Patent ceased through non-payment of renewal fee |
Effective date: 19920610 |