US3700890A
Expired / Lapsed
US
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Measurement of gas impurity concentration by infrared absorption spectroscopy
Assignee: AT&T Inc
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Filing: 1970-11-02
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Granted: 1972-10-24
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Expires: 1990-11-02
Abstract
Abstract An impurity in a gas medium is detected and its concentration measured by an infrared absorption spectroscopy technique. An infrared laser beam, whose wavelength is at or near an absorption line of the suspected impurity, is amplitude modulated at a fundamental acoustic frequency; and the modulated beam is incident upon the gas medium. The amplitude of the second harmonic acoustic frequency component of the resulting induced pressure (or temperature) variation of the gas medium is indicative, with great sensitivity, of the presence and concentration of the impurity.
Inventors
- 👤 Lloyd Barton Kruezer
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 03:19
CPC Classifications
G; G01; G01N; G01N21/00; G01N21/17; G01N21/1702; G01N2021/1704
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
106 words
In combination: a. an absorption cell containing a gas medium to be analyzed for a gaseous impurity; b. means forming a beam of electromagnetic radiation containing a wavelength corresponding to an absorption line of the impurity, the intensity of said beam being modulated at a fundamental frequency whereby the beam induces a time varying pressure response in the medium, said pressure response containing at least one harmonic component of a frequency which is a harmonic relative to the frequency of the fundamental frequency at which the beam is being modulated; and c. means for detecting the said harmonic component response of the medium to the beam.
Claim 2
Dependent Claim
106 words
In combination: a. an absorption cell containing a gas medium to be analyzed for a gaseous impurity; b. means forming a beam of electromagnetic radiation containing a wavelength corresponding to an absorption line of the impurity, the intensity of said beam being modulated at a fundamental frequency whereby the beam induces a time varying pressure response in the medium, said pressure response containing at least one harmonic component of a frequency which is a harmonic relative to the frequency of the fundamental frequency at which the beam is being modulated; and c. means for detecting the said harmonic component response of the medium to the beam.
Claim 3
Dependent Claim
25 words
The combination recited in claim 1 in which the beam of electromagnetic radiation is characterized by a maximum of intensity at an infrared frequency component.
Claim 4
Dependent Claim
18 words
The combination recited in claim 1 in which the harmonic frequency is equal to twice the fundamental frequency.
Claim 5
Dependent Claim
19 words
The combination recited in claim 3 in which the infrared frequency component is supplied by an optical parametric device.
Claim 6
Dependent Claim
16 words
The combination recited in claim 3 in which the fundamental frequency is in the acoustic range.
Claim 7
Dependent Claim
15 words
The combination recited in claim 5 in which the means for detecting includes a microphone.
Claim 8
Dependent Claim
27 words
The combination recited in claim 3 in which the infrared frequency is at least approximately equal to the frequency of an absorption line of the gaseous impurity.
Claim 9
Independent Claim
93 words
A method for detecting an impurity in a medium which comprises the steps of: a. directing upon the medium a beam of electromagnetic radiation which includes a wavelength corresponding to an absorption line of the impurity and which is modulated in intensity at a fundamental frequency whereby the beam induces a time varying pressure response in the medium, said pressure response containing at least one harmonic component relative to the frequency of the fundamental frequency at which the beam is being modulated; and b. monitoring the said harmonic component response of the medium.
Claim 10
Independent Claim
93 words
A method for detecting an impurity in a medium which comprises the steps of: a. directing upon the medium a beam of electromagnetic radiation which includes a wavelength corresponding to an absorption line of the impurity and which is modulated in intensity at a fundamental frequency whereby the beam induces a time varying pressure response in the medium, said pressure response containing at least one harmonic component relative to the frequency of the fundamental frequency at which the beam is being modulated; and b. monitoring the said harmonic component response of the medium.
Claim 11
Dependent Claim
46 words
The method recited in claim 8 in which the beaM comprises an infrared beam having a maximum of intensity at a frequency at least approximately equal to the frequency of an absorption line of the impurity, and the harmonic is equal to twice the fundamental frequency.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1975-10-24 | 1976-04-24 | 1976-10-24 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1979-10-24 | 1980-04-24 | 1980-10-24 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1983-10-24 | 1984-04-24 | 1984-10-24 | $7700.00 | Window Closed / Lapsed |