GB2223841A - Parameter measurement using refractive index change - Google Patents
Parameter measurement using refractive index change Download PDFInfo
- Publication number
- GB2223841A GB2223841A GB8820537A GB8820537A GB2223841A GB 2223841 A GB2223841 A GB 2223841A GB 8820537 A GB8820537 A GB 8820537A GB 8820537 A GB8820537 A GB 8820537A GB 2223841 A GB2223841 A GB 2223841A
- Authority
- GB
- United Kingdom
- Prior art keywords
- parameter
- refractive index
- temperature
- transducer
- changes
- 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- Withdrawn
Links
- 238000005259 measurement Methods 0.000 title abstract description 6
- 239000000463 material Substances 0.000 claims abstract description 31
- 230000003287 optical effect Effects 0.000 claims abstract description 21
- 230000005540 biological transmission Effects 0.000 claims abstract description 6
- 238000009529 body temperature measurement Methods 0.000 abstract description 2
- 239000012925 reference material Substances 0.000 abstract 3
- 238000009530 blood pressure measurement Methods 0.000 abstract 1
- 239000000523 sample Substances 0.000 description 18
- 239000012530 fluid Substances 0.000 description 15
- 239000007788 liquid Substances 0.000 description 7
- 239000011248 coating agent Substances 0.000 description 5
- 238000000576 coating method Methods 0.000 description 5
- 239000013307 optical fiber Substances 0.000 description 5
- 238000005253 cladding Methods 0.000 description 4
- 239000011521 glass Substances 0.000 description 3
- 239000007787 solid Substances 0.000 description 2
- WQZGKKKJIJFFOK-GASJEMHNSA-N Glucose Natural products OC[C@H]1OC(O)[C@H](O)[C@@H](O)[C@@H]1O WQZGKKKJIJFFOK-GASJEMHNSA-N 0.000 description 1
- 239000004411 aluminium Substances 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- 239000008280 blood Substances 0.000 description 1
- 210000004369 blood Anatomy 0.000 description 1
- 239000004568 cement Substances 0.000 description 1
- 239000000470 constituent Substances 0.000 description 1
- 230000001419 dependent effect Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 239000000835 fiber Substances 0.000 description 1
- 239000008103 glucose Substances 0.000 description 1
- 239000004033 plastic Substances 0.000 description 1
- 229920003023 plastic Polymers 0.000 description 1
- 239000000843 powder Substances 0.000 description 1
- 239000012254 powdered material Substances 0.000 description 1
- 239000004332 silver Substances 0.000 description 1
- 229910052709 silver Inorganic materials 0.000 description 1
- 239000012780 transparent material Substances 0.000 description 1
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
- G01L11/00—Measuring steady or quasi-steady pressure of a fluid or a fluent solid material by means not provided for in group G01L7/00 or G01L9/00
- G01L11/02—Measuring steady or quasi-steady pressure of a fluid or a fluent solid material by means not provided for in group G01L7/00 or G01L9/00 by optical means
-
- 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
- G01D5/268—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 using optical fibres
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01K—MEASURING TEMPERATURE; MEASURING QUANTITY OF HEAT; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR
- G01K11/00—Measuring temperature based upon physical or chemical changes not covered by groups G01K3/00, G01K5/00, G01K7/00 or G01K9/00
-
- 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
- G01N21/41—Refractivity; Phase-affecting properties, e.g. optical path length
- G01N21/43—Refractivity; Phase-affecting properties, e.g. optical path length by measuring critical angle
- G01N21/431—Dip refractometers, e.g. using optical fibres
Landscapes
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Health & Medical Sciences (AREA)
- Life Sciences & Earth Sciences (AREA)
- Chemical & Material Sciences (AREA)
- Analytical Chemistry (AREA)
- Biochemistry (AREA)
- General Health & Medical Sciences (AREA)
- Immunology (AREA)
- Pathology (AREA)
- Investigating Or Analysing Materials By Optical Means (AREA)
- Measuring Temperature Or Quantity Of Heat (AREA)
Abstract
The apparatus comprises a receptacle for holding a quantity of reference material having known variation of refractive index with changes in the test parameter (which may be temperature, pressure or the like); an elongate optical waveguide in contact with the reference material which is itself in thermal contact (in the case of temperature measurement) or under the same pressure (in the case of pressure measurement); and means for measuring the transmission of light passed along the optical waveguide, so as to provide a measurement depending on the value of the parameter of the reference material and thus of the test material.
Description
Parameter Measurement using Refractive Index Change Ihe present invention relates to the measurement of a parameter of a material using refractive index changes induced by changes in the aforementioned parameter.
It is known to measure and indicate or record the refractive index of various liquids by detecting the attenuation of internally reflected light passing through a transparent optical waveguide, such as a glass rod, an optical fibre or the like.
Optical fibres generally have a central core, entirely surrounded by a plastics or glass sheath (the cladding). In order for optical transmission along such a fibre to take place, the refractive index of the core must be greater than that of the cladding. It is well known that the relative refractive index of the core and cladding will determine the transmission characteristics of light along the optical fibre.
According to one aspect of the present invention, there is provided apparatus for measuring a parameter of a test material through changes in the refractive index thereof produced by or related to changes in said parameter, including an elongate optical waveguide along which light is passed by internal reflection, the waveguide having at least one portion in optical contact with said material and in which the transverse cross section of the said portion has a straight side.
Preferably the cross section of the said portion is polygonal and conveniently rectangular or square.
lhe straight sided or polygonal cross section may extend for substantially the whole length of the waveguide.
According to another aspect of the invention, there is provided apparatus for measuring a parameter of material, including a container holding a quantity of selected material having known variation of refractive index thereof with changes in said parameter, means for subjecting the selected material to the parameter or said material to be measured, an elongate optical waveguide at least partly immersed in said selected material, and means to measure the transmission of light passed along the optical waveguide, whereby to indicate the value of said parameter.
Where the parameter is temperature, the container is thermally conducting to ensure that said selected material is at substantially the same temperature as said material.
where the parameter is pressure, the container includes provision to allow the said selected material to be subject to the same pressure as said material.
According to a further aspect of the invention, there is provided apparatus for measuring the level of a liquid or fluid powdered material including an elongate optical waveguide along which light is passed by internal reflection, to be immersed vertically in the material, the waveguide having along the length thereof successive inwardly reflecting bands on the surface, with clear bands between the reflective bands, and means to measure the transmission of light passed along the optical waveguide, whereby to indicate the level of the said material in contact with the waveguide.
Various embodiments of the invention are described, by way of example only, with reference to the accompanying drawings, in which:
Figure 1 is a section in a vertical central plane of a temperature probe according to the invention;
Figure 2 shows part of the probe shown in Figure 1 at enlarged scale;
Figure 3 shows part of a pressure probe which is similar to the temperature probe in Figure 2, according to the invention;
Figure 4 shows part of a level measurement probe which is similar to the temperature probe of Figure 2, according to the invention; and
Figure 5 is a block diagram of a system for using the probes shown in Figures 1 to 4.
In Figure 1 a temperature probe, indicated generally at 10, is immersed in a fluid material 11, of which the temperature is to be measured. lhe probe 10 includes a thermally conducting elongate vessel 12 containing a fluid 13, and especially a liquid, of which the variation of optical refractive index with changes in temperature thereof is known.
An elongate optical transducer or optical waveguide 14 is immersed in the fluid 13 and is of a suitable high quality transparent material such as glass. Ihe cross section of the transducer 14 may be circular but is preferably polygonal, especially of rectangular or square cross section.
Ihe end and side faces of the transducer 14 are preferably polished to optical quality.
A photo-detector 15 is positioned against the bottom face of the transducer 14, to receive all the light emitting therefrom and to produce an electrical signal dependent on the intensity of that light.
Figure 2 shows the transducer 14 in more detail.
Ire upper and lower lengths 16,17 of all the side faces of the transducer 14 and also the upper end face 18 are all provided with a mirror-like reflective coating, such as deposited silver or aluminium. The faces between the lengths 16,17 are left clear. An optical prism 19 is optically connected with one side face of the transducer by means of a cement or liquid layer 20 having substantially the same refractive index as the transducer 14 and prism 19. There is no reflective coating in the region of the layer 20, so that light 21 entering in the direction shown, will pass through the prism 19, the layer 20 and into the transducer 14, where it is reflected downwardly by the reflective coating.
On reaching the transducer faces which are devoid of reflective coating, the light will be partly reflected within the transducer and partly transmitted into the fluid 13. The ratio of the intensity of the reflected to the transmitted light depends on the refractive indices of the material of the transducer 14 and of the fluid 13. thus, the magnitude of the electrical signal from the photo-detector 15 will also depend on the refractive indices. More importantly, variations in the refractive index of the fluid 13 due to variations in a parameter thereof such as temperature or pressure, will produce a corresponding variation in the electrical signal.
Figures 1 and 2 show how the probe 10 can be used to measure temperature of the fluid 11 as a consequence of the changes in refractive index of the fluid 13 with temperature.
Figure 5 shows how the probe 10 is cpnnected optically and electrically. A light source, which is preferably a laser 22, emits light to a beam splitter 23, from which part of the beam is fed back through a loop comprising a photo-detector compensator 24 and a line 25 to the laser 22, to stabilize and regulate the light output thereof.
The remaining light from the beam splitter 23 enters the transducer of the probe 10, as described above.
The probe 10 emits an electrical signal from the photo-detector 15 along a line 26 to processing hardware 27 and hence to a display 28, which displays the temperature of the fluid 11.
Figure 3 shows a probe used to sense a different parameter of the fluid 11, in this case the pressure thereof, which is known to change the refractive index of certain fluids 13, which fluids are chosen appropriately to the application.
A transducer 14 is provided, as in Figure 2, but changes of refractive index due to temperature are compensated by an almost identical temperature probe.as in Figure 1, or other temperature measurement device thermally bonded to transducer 14. The transducer 14a is fed through a prism 19a with light from the laser 22. The signal from transducer 14a (carrying indication of temperature) is sent to the processing hardware 27, to compensate for the effect of temperature changes. If the refractive index of the material 13 is changed by changes of temperature and pressure, one of these parameters can be held constant and the probe 10 used to measure the other parameter. If temperature cannot be held constant, the embodiment of Figure 3 is used.
Figure 4 shows a level measurement probe which can be used to measure the level of a liquid, or possibly a powdered solid, in which the probe is partly immersed. In this embodiment of the invention, a transducer 14b is fed with light from the laser 22 through a prism 19b. However, a succession of short bands of reflective coating 29 are provided, with intermediate clear bands 30. The lengths and spacing of the bands 29,30 are chosen to provide the required resolution of the particular application and may be equi-spaced or change progressively to provide a non-linear output.
Light emerging from the bottom of the transducer 14b impinges on a photo-transducer 15, as before, and the display 27 shows the height of the liquid or powder material up the transducer 14b, which in this embodiment has no surrounding vessel 12 or fluid 13.
As the level of the material being measured rises up the transducer 14b, it absorbs more light through each clear band 30 which it reaches. Thus, the display 28 shows the changing level of the material up the transducer 14b.
Except for the embodiment of Figure 4, the invention is applicable to measuring suitable parameters of fluid 11 which could be solid, liquid, vapour or gaseous.
In addition to the use of a polygonal or flat-sided cross-section for the transducer or optical waveguide described in the embodiments above, it has been found that a polygonal or flat-sided cross-section is advantageous in transducers or optical waveguides of the optical fibre type.
This is especially so where the normal cladding of the optical fibre is removed from the core thereof, for use in measuring the refractive index of material in which the optical fibre is immersed.
Parameters other than temperature, pressure or level can be measured, such as, for example the concentration of a constituent which causes changes in the refractive index of the material. One such parameter is the glucose concentration in blood.
Claims (6)
1. Apparatus for measuring a parameter of a test material
through changes in the refractive index thereof produced
by or related to changes in said parameter, including an
elongate optical waveguide along which light is passed by
internal reflection, the waveguide having at least one
portion in optical contact with said material and in which
the transverse cross section of the said portion has a
straight side.
2. Apparatus according to claim 1, wherein the cross-section
of said portion is polygonal.
3. Apparatus according to claim 2, wherein said polygonal
cross-section is rectangular or square.
4. Apparatus according to any of claims 1 to 3, which further
comprises a container holding a quantity of selected
material having known variation of refractive index
thereof with changes in said parameter, means for
subjecting the selected material to the parameter or said
material to be measured, at least said portion of said
waveguide being immersed in said selected material, said
apparatus also including means to measure the transmission
of light passed along the optical waveguide, whereby to
indicate the value of said parameter.
5. Apparatus according to claim 4, wherein said parameter is
temperature and said container is thermally conducting.
6. Apparatus according to claim 4, wherein said parameter is
pressure and said container includes means to ensure that
said selected material is subject to substantially the
same pressure as said test material.
Priority Applications (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB8820537A GB2223841A (en) | 1988-08-31 | 1988-08-31 | Parameter measurement using refractive index change |
| PCT/GB1989/001012 WO1990002322A1 (en) | 1988-08-31 | 1989-08-31 | Parameter measurement using refractive index change |
| AU41914/89A AU4191489A (en) | 1988-08-31 | 1989-08-31 | Parameter measurement using refractive index change |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB8820537A GB2223841A (en) | 1988-08-31 | 1988-08-31 | Parameter measurement using refractive index change |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| GB8820537D0 GB8820537D0 (en) | 1988-09-28 |
| GB2223841A true GB2223841A (en) | 1990-04-18 |
Family
ID=10642924
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB8820537A Withdrawn GB2223841A (en) | 1988-08-31 | 1988-08-31 | Parameter measurement using refractive index change |
Country Status (3)
| Country | Link |
|---|---|
| AU (1) | AU4191489A (en) |
| GB (1) | GB2223841A (en) |
| WO (1) | WO1990002322A1 (en) |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB9111776D0 (en) * | 1991-05-31 | 1991-07-24 | De Beers Ind Diamond | Determination of the condition of or change in state of an environment |
| CN107677341B (en) * | 2017-10-30 | 2023-04-07 | 吉林大学 | Optical fiber interference water level sensing device and method based on air refractive index |
Citations (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB1116560A (en) * | 1966-02-12 | 1968-06-06 | Gullick Ltd | Improvements in or relating to apparatus for the determination and/or control of the proportions of the constituents in a fluid mixture of emulsion |
| US3999857A (en) * | 1975-05-29 | 1976-12-28 | Monsanto Research Corporation | Refractive index detector |
| GB1514977A (en) * | 1975-12-02 | 1978-06-21 | Standard Telephones Cables Ltd | Detecting oil in water |
| GB1530997A (en) * | 1974-11-11 | 1978-11-01 | Monsanto Co | Optical analytical method and device |
| GB1543914A (en) * | 1976-02-06 | 1979-04-11 | Monsanto Co | Organic vapour detector |
| EP0074788A2 (en) * | 1981-09-10 | 1983-03-23 | The Board Of Trustees Of The Leland Stanford Junior University | Fiber coupler temperature tranducer |
| WO1985003360A2 (en) * | 1984-01-20 | 1985-08-01 | Hughes Aircraft Company | Fiber optic structure and method for making |
| GB2173296A (en) * | 1985-03-15 | 1986-10-08 | Sharp Kk | Optical pressure sensor |
Family Cites Families (15)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB1582768A (en) * | 1977-08-26 | 1981-01-14 | Standard Telephones Cables Ltd | Temperature sensitive optical fibre |
| US4151747A (en) * | 1978-06-21 | 1979-05-01 | Electric Power Research Institute, Inc. | Monitoring arrangement utilizing fiber optics |
| US4201446A (en) * | 1978-10-20 | 1980-05-06 | Honeywell Inc. | Fiber optic temperature sensor using liquid component fiber |
| US4203326A (en) * | 1979-01-26 | 1980-05-20 | Electric Power Research Institute, Inc. | Method and means for improved optical temperature sensor |
| US4316388A (en) * | 1979-02-22 | 1982-02-23 | Westinghouse Electric Corp. | Temperature detection using the refractive indices of light guides |
| SE7903175L (en) * | 1979-04-10 | 1980-10-11 | Asea Ab | FIBEROPTICAL METDON |
| DE3045085C2 (en) * | 1980-11-29 | 1986-01-23 | Dornier System Gmbh, 7990 Friedrichshafen | Temperature sensor |
| EP0061884A1 (en) * | 1981-03-30 | 1982-10-06 | Imperial Chemical Industries Plc | Optical fibre sensor |
| AU557816B2 (en) * | 1981-09-18 | 1987-01-08 | Prutec Ltd. | Method for the determination of species in solution with an optical wave-guide |
| IT1158799B (en) * | 1982-11-18 | 1987-02-25 | Consiglio Nazionale Ricerche | OPTICAL FIBER THERMOMETER |
| DE3321203A1 (en) * | 1983-06-11 | 1984-12-13 | Phönix Armaturen-Werke Bregel GmbH, 6000 Frankfurt | REFRACTOMETER |
| US4756627A (en) * | 1984-08-17 | 1988-07-12 | Sperry Corporation | Optical temperature sensor using photoelastic waveguides |
| US4689483A (en) * | 1985-04-25 | 1987-08-25 | Advanced Fiberoptic Technologies Corporation | Fiber optical temperature measuring apparatus |
| GB2186073B (en) * | 1986-02-03 | 1989-10-25 | Spectran Corp | Fiber optic pressure sensor |
| AU579041B2 (en) * | 1986-05-09 | 1988-11-10 | Thomas & Betts Corporation | Method of and apparatus for fiber optic sensing |
-
1988
- 1988-08-31 GB GB8820537A patent/GB2223841A/en not_active Withdrawn
-
1989
- 1989-08-31 WO PCT/GB1989/001012 patent/WO1990002322A1/en active Application Filing
- 1989-08-31 AU AU41914/89A patent/AU4191489A/en not_active Abandoned
Patent Citations (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB1116560A (en) * | 1966-02-12 | 1968-06-06 | Gullick Ltd | Improvements in or relating to apparatus for the determination and/or control of the proportions of the constituents in a fluid mixture of emulsion |
| GB1530997A (en) * | 1974-11-11 | 1978-11-01 | Monsanto Co | Optical analytical method and device |
| US3999857A (en) * | 1975-05-29 | 1976-12-28 | Monsanto Research Corporation | Refractive index detector |
| GB1514977A (en) * | 1975-12-02 | 1978-06-21 | Standard Telephones Cables Ltd | Detecting oil in water |
| GB1543914A (en) * | 1976-02-06 | 1979-04-11 | Monsanto Co | Organic vapour detector |
| EP0074788A2 (en) * | 1981-09-10 | 1983-03-23 | The Board Of Trustees Of The Leland Stanford Junior University | Fiber coupler temperature tranducer |
| WO1985003360A2 (en) * | 1984-01-20 | 1985-08-01 | Hughes Aircraft Company | Fiber optic structure and method for making |
| GB2173296A (en) * | 1985-03-15 | 1986-10-08 | Sharp Kk | Optical pressure sensor |
Also Published As
| Publication number | Publication date |
|---|---|
| WO1990002322A1 (en) | 1990-03-08 |
| GB8820537D0 (en) | 1988-09-28 |
| AU4191489A (en) | 1990-03-23 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| WAP | Application withdrawn, taken to be withdrawn or refused ** after publication under section 16(1) |