US5315673A
Expired / Lapsed
US
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Optical waveguide vapor sensor
Assignee: TRANSDUCER RESEARCH Inc OF MINNESOTA
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Filing: 1992-03-09
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Granted: 1994-05-24
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Expires: 2012-03-09
Abstract
Abstract An optical waveguide sensor for the detection of acid vapors comprises a chemically sensitive reagent coating of bromothymol blue or thymol blue indicator suspended in a Nafion polymer film. The sensor uses a 562-nm light-emitting diode source and a phototransistor detector. The response to HCl and H 2 S vapors is both rapid and reversible, with an estimated detection limit for H 2 S of less than 15 ppmv (parts per million by volume). The sensor exhibits generalized response to protonic acid vapors, but does not produce an indicator response to CO 2 , even at large concentrations (60 volume-%) in the presence of water vapor. The sensor exhibits a systematic interference from water vapor which may be corrected by a differential approach, either using a reference sensor (Nafion without an indicator) or by monitoring the sensor responses at two wavelengths.
Inventors
- 👤 Joseph R. Stetter
- 👤 G. Jordan Maclay
- 👤 David S. Ballantine, Jr.
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-28 20:34
CPC Classifications
G; G01; G01N; G01N21/00; G01N21/75; G01N21/77; G01N21/7703; G01N2021/7706; G01N2021/773; G01N21/78; G01N21/783; G01N21/81
Claims Analysis
Total Claims: 23
Claim 1
Independent Claim
134 words
A sensor for detecting a selected air constituent comprising: an optical waveguide having a front end and a rear end; a light source for transmitting light of a selected wavelength to one end of the waveguide; and means for measuring the intensity of light emitted from the other end of the waveguide, said waveguide comprising a film of material disposed on a substrate such that multiple internal light reflections occur at the interfaces between the film and the substrate and between the film and air, said material having optical properties that are susceptible to change in the presence of said air constituent, wherein said film comprises a reagent embedded in or forming a part of a polymer, said reagent yielding a substance having characteristic light-transmissive or light-adsorptive properties upon exposure to said air constituent.
Claim 2
Dependent Claim
134 words
A sensor for detecting a selected air constituent comprising: an optical waveguide having a front end and a rear end; a light source for transmitting light of a selected wavelength to one end of the waveguide; and means for measuring the intensity of light emitted from the other end of the waveguide, said waveguide comprising a film of material disposed on a substrate such that multiple internal light reflections occur at the interfaces between the film and the substrate and between the film and air, said material having optical properties that are susceptible to change in the presence of said air constituent, wherein said film comprises a reagent embedded in or forming a part of a polymer, said reagent yielding a substance having characteristic light-transmissive or light-adsorptive properties upon exposure to said air constituent.
Claim 3
Dependent Claim
25 words
The sensor of claim 1, wherein: said light source is a light-emitting diode; said photodetector is a phototransistor; and said reagent is a colorimetric reagent.
Claim 4
Dependent Claim
17 words
The sensor of claim 2, wherein said polymer comprises a fluorinated ethylene sulfonic acid compound or derivative.
Claim 5
Dependent Claim
35 words
The sensor of claim 3, comprising signal-processing means for detecting the presence of at least one air constituent, wherein the presence of water vapor is deduced from an increase in the transmissivity of said waveguide.
Claim 6
Dependent Claim
27 words
The sensor of claim 4, wherein the presence of an acidic constituent is deduced from a change in the absorption of light of a selected wavelength range.
Claim 7
Dependent Claim
12 words
The sensor of claim 5, wherein said reagent comprises a pH indicator.
Claim 8
Dependent Claim
15 words
The sensor of claim 6, wherein said pH indicator comprises bromothymol blue or thymol blue.
Claim 9
Dependent Claim
16 words
The sensor of claim 7, wherein the selected wavelength range comprises the wavelength of 562 nm.
Claim 10
Dependent Claim
41 words
The sensor of claim 2 for the detection of basic air constituents, wherein said polymer comprises polyvinylpyrrolidone and said reagent comprises bromcresol green, said film having been first treated with acid so as to turn the reagent to its yellow form.
Claim 11
Dependent Claim
31 words
The sensor of claim 2, wherein said light-emitting diode and phototransistor are controlled by an electric circuit, said circuit causing the diode to be turned on and off in repetitive cycles.
Claim 12
Dependent Claim
15 words
The sensor of claim 1, wherein said film is disposed on a thin transparent substrate.
Claim 13
Dependent Claim
195 words
A sensor for detecting a selected air constituent comprising: an optical waveguide having a front end and a rear end; a light source for transmitting light of a selected wavelength to one end of the waveguide; means for measuring the intensity of light emitted from the other end of the waveguide; and signal-processing means for detecting the presence of at least one air constituent, wherein the presence of water vapor is deduced from an increase in the transmissivity of said waveguide and the presence of an acidic constituent is deduced from a change in the absorption of light of a selected wavelength range; said waveguide comprising a film of material that comprises a reagent embedded in or forming part of a polymer; said reagent yielding a substance having characteristic light-transmissive or light-adsorptive properties upon exposure to said air constituent; wherein: said light source is a light-emitting diode; said photodetector is a phototransistor; and said reagent is a colorimetric reagent; said polymer comprises a fluorinated ethylene sulfonic acid compound or derivative; and said reagent comprises a pH indicator; wherein said signal-processing means includes means for distinguishing between the effects of water vapor and of acidic constituents.
Claim 14
Dependent Claim
195 words
A sensor for detecting a selected air constituent comprising: an optical waveguide having a front end and a rear end; a light source for transmitting light of a selected wavelength to one end of the waveguide; means for measuring the intensity of light emitted from the other end of the waveguide; and signal-processing means for detecting the presence of at least one air constituent, wherein the presence of water vapor is deduced from an increase in the transmissivity of said waveguide and the presence of an acidic constituent is deduced from a change in the absorption of light of a selected wavelength range; said waveguide comprising a film of material that comprises a reagent embedded in or forming part of a polymer; said reagent yielding a substance having characteristic light-transmissive or light-adsorptive properties upon exposure to said air constituent; wherein: said light source is a light-emitting diode; said photodetector is a phototransistor; and said reagent is a colorimetric reagent; said polymer comprises a fluorinated ethylene sulfonic acid compound or derivative; and said reagent comprises a pH indicator; wherein said signal-processing means includes means for distinguishing between the effects of water vapor and of acidic constituents.
Claim 15
Dependent Claim
24 words
The sensor of claim 12, wherein said distinguishing means comprises a second light-emitting diode whose range of emitted wavelengths is outside said light-absorption range.
Claim 16
Dependent Claim
26 words
The sensor of claim 13, wherein said distinguishing means comprises a timing circuit that causes the two diodes to go on and off in alternating cycles.
Claim 17
Dependent Claim
24 words
The sensor of claim 13, wherein said distinguishing means comprises a second waveguide and a second phototransistor operating in conjunction with the second diode.
Claim 18
Dependent Claim
34 words
The sensor of claim 13, wherein: said pH-sensitive substance comprises bromothymol blue; said light-absorption range comprises the wavelength of 562 nm; and said second light-emitting diode emits at a wavelength of about 680 nm.
Claim 19
Dependent Claim
29 words
The sensor of claim 12, wherein said distinguishing means comprises a second waveguide and a second phototransistor, the film in said second waveguide being free of said pH indicator.
Claim 20
Dependent Claim
14 words
The sensor of claim 17, wherein said indicator is bromothymol blue or thymol blue.
Claim 21
Dependent Claim
119 words
A sensor for detecting a selected air constituent comprising: an optical waveguide having a front end and a rear end; a light source for transmitting light of a selected wavelength to one end of the waveguide; and a photodetector for measuring the intensity of light emitted from the other end of the waveguide; said waveguide comprising a film of material whose optical properties are susceptible to change in the presence of said air constituent; wherein said film comprises a reagent embedded in or forming part of a polymer, said reagent yielding a substance having characteristic light-transmissive or light-absorptive properties upon exposure to said air constituent; wherein said film is coating a substrate that is opaque to said selected wavelengths.
Claim 22
Dependent Claim
119 words
A sensor for detecting a selected air constituent comprising: an optical waveguide having a front end and a rear end; a light source for transmitting light of a selected wavelength to one end of the waveguide; and a photodetector for measuring the intensity of light emitted from the other end of the waveguide; said waveguide comprising a film of material whose optical properties are susceptible to change in the presence of said air constituent; wherein said film comprises a reagent embedded in or forming part of a polymer, said reagent yielding a substance having characteristic light-transmissive or light-absorptive properties upon exposure to said air constituent; wherein said film is coating a substrate that is opaque to said selected wavelengths.
Claim 23
Dependent Claim
32 words
The sensor of claim 19, wherein said substrate comprises a rod that is opaque to said selected wavelengths and has two end surfaces and transparent lenses affixed onto each of said surfaces.
References Cited (Backward Citations)
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| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
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| 3.5 Years (Year 4) | 1997-05-23 | 1997-11-22 | 1998-05-24 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2001-05-23 | 2001-11-22 | 2002-05-24 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2005-05-23 | 2005-11-22 | 2006-05-24 | $7700.00 | Window Closed / Lapsed |