Optical sensing of measurands

Abstract

A dome-shaped chemical sensing probe comprises an optical fiber or may be mounted on an optical fiber. The probe has a chemically sensitive measuring material which exhibits a change in volume and/or a change in refractive index in the presence of a given chemical. The change in volume and/or refractive index gives a change in an optical path length through the probe which can be measured interferometrically.

1 . An interferometric sensing probe comprising an optical fiber and a dome-shaped measuring material adapted to exhibit a change in volume and/or refractive index in response to a given measurand so as to produce an interferometrically measurable change in at least one optical path length through the probe. 
   
   
       2 . The probe as claimed in  claim 1 , wherein the measuring material is chemically responsive and is adapted to exhibit a change in volume and/or refractive index in the presence of a given chemical. 
   
   
       3 . The probe as claimed in  claim 1 , wherein said measuring material comprises a hydrogel. 
   
   
       4 . The probe as claimed in  claim 1  comprising an optical fiber and an intermediate substrate layer between the optical fiber and the measuring material. 
   
   
       5 . The probe as claimed in  claim 4  comprising an intermediate lens between said substrate and said fiber. 
   
   
       6 . An interferometric sensing probe comprising an optical fiber and a dome-shaped measuring material adapted to exhibit a change in volume and/or refractive index in response to a given measurand so as to produce an interferometrically measurable change in at least one optical path length through the probe, wherein said measuring material comprises a cross-linked polymer. 
   
   
       7 . The probe as claimed in  claim 6 , wherein the measuring material comprises a swollen cross-linked polymer. 
   
   
       8 . The probe as claimed in  claim 6  wherein said cross-linked polymer comprises a hydrogel. 
   
   
       9 . The probe as claimed in  claim 8 , wherein said hydrogel is an ionic hydrogel. 
   
   
       10 . The probe as claimed in  claim 6 , wherein the measuring material comprises a biomolecular recognition component. 
   
   
       11 . The probe as claimed in  claim 6 , wherein said polymer comprises polymer chains having cross links and wherein additional cross-links are formed between antibodies and antigens or peptide sequences immobilised on the polymer chains. 
   
   
       12 . The probe as claimed in  claim 6 , wherein said polymer comprises polymer chains having cross links and wherein additional cross-links are formed by peptides. 
   
   
       13 . The apparatus for sensing a measurand comprising a probe as claimed in  claim 1  and read out instrumentation for reading out a measurement of said measurand from said probe. 
   
   
       14 . The apparatus as claimed in  claim 13  comprising a scanning filter. 
   
   
       15 . An apparatus for sensing a chemical interferometrically comprising a substrate bearing a dome-shaped chemically responsive measuring material adapted to exhibit a change in volume and/or refractive index in the presence of a given chemical so as to produce an interferometrically measurable change in at least one optical path length through the apparatus, and at least one lens through which in use light traversing said optical path passes. 
   
   
       16 . The apparatus as claimed in  claim 15 , wherein the measuring material is a swollen cross-linked polymer. 
   
   
       17 . The apparatus as claimed in  claim 16 , wherein said swollen cross-linked polymer is an ionic hydrogel. 
   
   
       18 . The apparatus as claimed in  claim 16 , wherein said polymer comprises polymer chains having cross-links and wherein additional cross-links are formed by peptides. 
   
   
       19 . An interferometric chemical sensing probe comprising an optical fiber and a chemically responsive measuring material adapted to exhibit a change in volume and/or refractive index in the presence of a given chemical so as to produce an interferometrically measurable change in at least one optical path length through the probe, wherein said chemically responsive measuring material comprises a swollen cross-linked polymer network. 
   
   
       20 . The probe as claimed in  claim 19  wherein the measuring material comprises a hydrogel. 
   
   
       21 . An interferometric sensing probe comprising an optical fiber and a measuring material comprising a swollen cross-linked polymer network adapted to exhibit a change in volume and/or refractive index in response to a given measurand so as to produce an interferometrically measurable change in at least one optical path length through the probe. 
   
   
       22 . An optical sensing probe comprising:
 a measuring material said measuring material undergoing a change in volume in response to a given measurand; and   a reflector coupled to the measuring material so as to be moved by the measuring material as the measuring material changes in volume, thereby changing the length of a light path through the apparatus, wherein said measuring material comprises a swollen cross-linked polymer network.   
   
   
       23 . The probe as claimed in  claim 22  wherein:
 said reflector has a first side and a second side;   said first side has a first region and a second region;   said first region is coupled to said measuring material; and   said probe is arranged such that in use a beam of light for measuring said measurand is incident upon the reflector on said second region of said first side.   
   
   
       24 . The probe as claimed in  claim 23  wherein the measuring material is arranged in the form of a hollow cylinder having a central space and wherein said light beam is arranged to pass through said central space to said reflector. 
   
   
       25 . The probe as claimed in  claim 23  wherein:
 said reflector has a first side and a second side;   said first side is coupled to said measuring material; and   said probe is arranged such that in use a beam of light for measuring said measurand is incident upon the second side of said reflector.   
   
   
       26 . The probe as claimed in  claim 19  arranged such that said optical path through the probe does not include the measuring material. 
   
   
       27 . The probe as claimed in  claim 19  comprising compensation means for compensating for environmental parameters. 
   
   
       28 . The probe as claimed in  claim 21  comprising compensation means for compensating for environmental parameters. 
   
   
       29 . The probe as claimed in  claim 27  comprising an optical fiber having a fiber Bragg grating written into the optical fiber. 
   
   
       30 . The probe as claimed in  claim 27  wherein said compensation means comprises a Fabry-Perot interferometer. 
   
   
       31 . The probe as claimed in  claim 30  wherein said Fabry-Perot interferometer is provided in parallel with an interferometer for measuring a target analyte. 
   
   
       32 . The probe as claimed in  claim 31  comprising measurement and compensation cavities adjacent one another on a common support. 
   
   
       33 . The probe as claimed in  claim 32  comprising separate optical fibers for interrogating said cavities. 
   
   
       34 . The probe as claimed in  claim 27  wherein the swollen cross-linked polymer network is a first cross-linked polymer and wherein the compensation means comprises a second cross-linked polymer with a different response to a target measurand than the first. 
   
   
       35 . The probe as claimed in  claim 27  comprising an optical fiber having an end and an intermediate substrate layer between the measuring material and the end of the optical fiber. 
   
   
       36 . The probe as claimed in  claim 35  wherein said substrate layer is provided with means, such as a suitable indent, to locate the optical fiber. 
   
   
       37 . An interferometric chemical sensing probe comprising an optical fiber and a first chemically responsive measuring material adapted to exhibit a change in volume and/or refractive index in the presence of a given chemical so as to produce an interferometrically measurable change in at least a first optical path length through the probe; and a second chemically responsive measuring material adapted to exhibit a change in volume and/or refractive index in the presence of a given environmental parameter so as to produce an interferometrically measurable change in a second optical path length through the probe; wherein said first and second measuring materials are substantially the same and wherein said probe is arranged such that in use said second measuring material does not come into contact with a target analyte. 
   
   
       38 . The probe as claimed in  claim 37  wherein said first and second measuring materials provided at a distal end of an optical fiber separated by a layer which act to reflect a proportion of light incident on said reflector. 
   
   
       39 . The probe as claimed in  claim 37  comprising a membrane for blocking access of said target analyte to said second measuring material. 
   
   
       40 . The probe as claimed in  claim 27  wherein said compensation means is provided in series with a measurement part of the probe. 
   
   
       41 . The probe as claimed in  claim 27  having the measuring material and a compensation material provided coaxially at a distal end of an optical fiber. 
   
   
       42 . The probe as claimed in  claim 41  wherein said measuring and compensation materials are covered by a membrane sleeve or a capillary tube. 
   
   
       43 . The probe as claimed in  claim 27  comprising an optical fiber and an intermediate substrate layer between the optical fiber and the measuring material. 
   
   
       44 . The probe as claimed in  claim 43  comprising an intermediate lens between said substrate and said fiber. 
   
   
       45 . The apparatus for sensing a measurand comprising a probe as claimed in  claim 19  and read out instrumentation for reading out a measurement of said measurand from said probe. 
   
   
       46 . The apparatus for sensing a measurand comprising a probe as claimed in  claim 21  and read out instrumentation for reading out a measurement of said measurand from said probe. 
   
   
       47 . The apparatus as claimed in  claim 46  comprising a scanning filter. 
   
   
       48 . An apparatus for sensing a chemical interferometrically comprising a substrate bearing a chemically responsive measuring material adapted to exhibit a change in volume and/or refractive index in the presence of a given chemical so as to produce an interferometrically measurable change in at least one optical path length through the apparatus, and at least one lens through which in use light traversing said optical path passes. 
   
   
       49 . The probe as claimed in  claim 20  wherein said polymer comprises polymer chains having cross links and wherein additional cross-links are formed between antibodies and antigens or peptide sequences immobilised on the polymer chains. 
   
   
       50 . The probe as claimed in  claim 20  wherein said hydrogel comprises a biomolecular recognition component linked to the polymer chain. 
   
   
       51 . The method of measuring a measurand comprising using a probe as a or part of a laser cavity. 
   
   
       52 . An interferometric sensing probe comprising an optical fiber, and a measuring material comprising a cross-linked polymer adapted to exhibit a change in volume and/or refractive index in response to a given measurand so as to produce an interferometrically measurable change in at least one optical path length through the probe, wherein said measuring material comprises a biomolecular recognition component. 
   
   
       53 . The probe as claimed in  claim 52 , wherein said cross-linked polymer is a hydrogel. 
   
   
       54 . An interferometric sensing probe for use with an optical fiber, said probe comprising a dome-shaped measuring material adapted to exhibit a change in volume and/or refractive index in response to a given measurand so as to produce an interferometrically measurable change in at least one optical path length through the probe. 
   
   
       55 . An interferometric sensing probe for use with an optical fiber, said probe comprising a dome-shaped measuring material adapted to exhibit a change in volume and/or refractive index in response to a given measurand so as to produce an interferometrically measurable change in at least one optical path length through the probe, wherein said measuring material comprises a cross-linked polymer. 
   
   
       56 . An interferometric sensing probe for use with an optical fiber, said probe comprising a chemically responsive measuring material adapted to exhibit a change in volume and/or refractive index in the presence of a given chemical so as to produce an interferometrically measurable change in at least one optical path length through the probe, wherein said chemically responsive measuring material comprises a swollen cross-linked polymer network. 
   
   
       57 . An interferometric sensing probe for use with an optical fiber, said probe comprising a measuring material comprising a swollen cross-linked polymer network adapted to exhibit a change in volume and/or refractive index in response to a given measurand so as to produce an interferometrically measurable change in at least one optical path length through the probe. 
   
   
       58 . An interferometric sensing probe for use with an optical fiber, said probe comprising a first chemically responsive measuring material adapted to exhibit a change in volume and/or refractive index in the presence of a given chemical so as to produce an interferometrically measurable change in at least a first optical path length through the probe; and a second chemically responsive measuring material adapted to exhibit a change in volume and/or refractive index in the presence of a given environmental parameter so as to produce an interferometrically measurable change in a second optical path length through the probe; wherein said first and second measuring materials are substantially the same and wherein said probe is arranged such that in use said second measuring material does not come into contact with a target analyte. 
   
   
       59 . An interferometric sensing probe for use with an optical fiber, said probe comprising a measuring material comprising a cross-linked polymer adapted to exhibit a change in volume and/or refractive index in response to a given measurand so as to produce an interferometrically measurable change in at least one optical path length through the probe, wherein said measuring material comprises a biomolecular recognition component.