US3723731A
Expired / Lapsed
US
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Absorption spectroscopy
Assignee: ERT Inc
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Filing: 1971-03-18
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Granted: 1973-03-27
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Expires: 1991-03-18
Abstract
Abstract Gas in a sample region is analyzed in a nondispersive system for the presence of a particular gas of interest by cross-correlating the absorption spectra of the sample and a specimen of the gas of interest. Radiation is directed through the sample region and a filter for isolating a narrow band of frequencies within the absorption band of the gas of interest, to a radiation detector. The radiation is passed through cells that provide the total energy transmitted at the line or lines of interest and a reference energy transmitted by a region adjacent to the lines of interest and unaffected by changes in absorption in the sample region. In one embodiment this is accomplished by passing the radiation from the filter in rapid succession through three cells typically containing, respectively, an inert gas, the gas of interest at a pressure of about one atmosphere and the gas of interest at approximately two atmospheres pressure, to produce three signals which are combined by a conventional electronic system to give the fractional absorption of the gas of interest in the sample region. an interferometer containing in one leg, a cell containing the gas of interest at a pressure of about two atmospheres, may be located in the radiation path between the cells and the detector.
Inventors
- 👤 H Blau
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 07:28
CPC Classifications
G; G01; G01N; G01N21/00; G01N21/17; G01N21/25; G01N21/31; G01N21/35; G01N21/3504; G01N21/3518; G01N21/314
Claims Analysis
Total Claims: 21
Claim 1
Independent Claim
191 words
In an optical, nondispersive absorption analyzer having a filter for passing radiation in a relatively narrow spectral region including absorption lines of a material of interest, a radiation detector sensitive in said region and means for directing a beam of radiation which has passed through a sample region containing material to be analyzed and thence through said filter to said detector, the improvement comprising, in combination: means for determining total energy flux F1 transmitted to said detector, within said lines of interest and for determining total energy flux F2 transmitted to said detector in regions immediately adjacent to said lines of interest and substantially invariant with changes in absorption at said lines of interest by said material in said sample region; said means for determining said total energies comprising: a first light-transmitting cell capable of substantially nonabsorptively transmitting radiation at said lines of interest; a second light-transmitting cell capable of substantially absorbing all of the radiation within only said lines of interest, and a third light-transmitting cell capable of substantially absorbing all of the radiation with said lines of interest and only selected regions immediately adjacent to said lines of interest.
Claim 2
Dependent Claim
191 words
In an optical, nondispersive absorption analyzer having a filter for passing radiation in a relatively narrow spectral region including absorption lines of a material of interest, a radiation detector sensitive in said region and means for directing a beam of radiation which has passed through a sample region containing material to be analyzed and thence through said filter to said detector, the improvement comprising, in combination: means for determining total energy flux F1 transmitted to said detector, within said lines of interest and for determining total energy flux F2 transmitted to said detector in regions immediately adjacent to said lines of interest and substantially invariant with changes in absorption at said lines of interest by said material in said sample region; said means for determining said total energies comprising: a first light-transmitting cell capable of substantially nonabsorptively transmitting radiation at said lines of interest; a second light-transmitting cell capable of substantially absorbing all of the radiation within only said lines of interest, and a third light-transmitting cell capable of substantially absorbing all of the radiation with said lines of interest and only selected regions immediately adjacent to said lines of interest.
Claim 3
Dependent Claim
99 words
An absorption analyzer as defined in claim 4 wherein said material in said sample region is a gas of interest, and said first light-transmitting cell contains a gas capable of substantially nonabsorptively transmitting radiation at said lines of interest; said second light-transmitting cell contains said gas of interest at at least a partial pressure sufficient to effect substantially complete absorption of said lines of interest in radiation passing through said second cell; and said third light-transmitting cell contains said gas of interest at a partial pressure substantially greater than the partial pressure of said gas in said second cell.
Claim 4
Dependent Claim
54 words
An absorption analyzer as defined in claim 5 wherein said gas of interest within said third cell is at a partial pressure such that the absorption lines of interest are broadened to substantially twice the width of the corresponding absorption lines of interest of said gas within the sample region and said second cell.
Claim 5
Dependent Claim
25 words
An absorption analyzer as defined in claim 5 wherein said first cell contains a gas which is nonabsorbent with respect to said lines of interest.
Claim 6
Dependent Claim
40 words
An absorption analyzer as defined in claim 1 including means for causing said beam of radiation to pass through said first, second and third cells so as to cause said detector to produce first, second and third transmission signals respectively.
Claim 7
Dependent Claim
45 words
An absorption analyzer as defined in claim 5 wherein the means for causing said beam to pass through said cells include means for rotating an array of said cells as a unit to position each of said cells successively in the path of said beam.
Claim 8
Dependent Claim
26 words
An absorption analyzer as defined in claim 5 wherein said first, second, and third cells are stationary and the last mentioned means include movable light-deviating means.
Claim 9
Dependent Claim
48 words
An absorption analyzer as defined in claim 5 wherein said means for causing said beam to pass through said cells cause said cell and beam to move with respect to each other at a frequency substantially exceeding the frequency of substantial fluctuations in the intensity of said source.
Claim 10
Dependent Claim
80 words
An absorption analyzer as defined in claim 1 further including interference means for transmitting substantially only at the center of a spectral line corresponding to a predetermined absorption line of interest, said interference means being located to transmit said beam from said cells to said detector and including a fourth light-transmitting cell capable of substantially absorbing all of the radiation with said predetermined absorption line, and means for passing at least a part of said beam through said fourth cell.
Claim 11
Dependent Claim
27 words
An absorption analyzer as defined in claim 9 wherein said interference means include an interferometer and said fourth cell is located in one leg of said interferometer.
Claim 12
Dependent Claim
40 words
An absorption gas analyzer as defined in claim 9 wherein said material in said sample region is a gas of interest, and said fourth cell, and said third cell, both contain said gas of interest at substantially the same pressure.
Claim 13
Dependent Claim
40 words
An absorption analyzer as defined in claim 2 further including an interferometer for transmitting said beam from said cells to said detector and a fourth light transmitting cell containing said gas of interest located in a leg of said interferometer.
Claim 14
Dependent Claim
32 words
An absorption analyzer as defined in claim 12 wherein said interferometer is balanced to transmit relatively little radiation except at a wavelength corresponding to an absorption line of said gas of interest.
Claim 15
Dependent Claim
29 words
An absorption analyzer as defined in claim 12 wherein said interferometer is balanced to give destructive interference at the wavelengths at the center of the spectral region of interest.
Claim 16
Dependent Claim
32 words
An absorption analyzer as defined in claim 12 wherein said gas of interest in said fourth cell is at substantially the same pressure as said gas of interest in said third cell.
Claim 17
Dependent Claim
53 words
An absorption analyzer as defined in claim 15 wherein said gas in said third and fourth cells is at a pressure sufficient to broaden the width of said absorption line to substantially twice the absorption line width at the pressure of said gas of interest in said sample region and said second cell.
Claim 18
Dependent Claim
68 words
An absorption analyzer as defined in claim 2 further including means for so combining said signals as to obtain the fractional absorption of the gas of interest in the sample region as expressed by the ratio wherein said detector is adapted to generate signals X, Y, and Z corresponding respectively to the total radiation flux transmitted respectively by said first, second, and third cells from said sample region.
Claim 19
Dependent Claim
111 words
An absorption analyzer aS defined in claim 1 wherein said material in said sample region is a gas of interest; said first cell contains a gas capable of substantially nonabsorptively transmitting radiation at said lines of interest; said second cell contains the gas of interest at a partial pressure at least sufficient to effect substantially complete absorption of said lines of interest in radiation passing through said second cell; and said third cell contains another gas having absorption characteristics in at least one region closely adjacent to a corresponding line of interest and being at a partial pressure approximately the partial pressure of the gas of interest in said second cell.
Claim 20
Dependent Claim
68 words
An absorption analyzer as defined in claim 18 wherein said detector is adapted to generate signals X, Y, and Z corresponding respectively to the total radiation flux transmitted by said first, second, and third cells from said sample region, and further including means for so combining said signals as to obtain the fractional absorption of the gas of interest in the sample region as expressed by the ratio
Claim 21
Dependent Claim
186 words
An absorption analyzer as defined in claim 1 wherein said material in said sample region is a gas of interest and wherein said means for determining said total energies comprises a first light-transmitting cell capable of substantially nonabsorptively transmitting radiation as said lines of interest; a second light-transmitting cell containing said gas of interest, means for selectively and uniformly attenuating, over substantially said spectral region, radiation transmitted by said first and second cells, said detector being adapted to generate signals V, Y and S corresponding respectively to the total radiation flux transmitted by respectively a combination of said first cell and said attenuating means, said second cell, and a combination of said second cell and said attenuating means, and further including means for so combining said signals as to obtain the fractional absorption of the gas of interest in the sample region as expressed by the ratio (V-Y)/(Y-S), the attenuation provided by said attenuating means being such that the combination of said first cell and said attenuator passes the same flux as said second cell along when no gas of interest is in said sample region.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1976-03-26 | 1976-09-25 | 1977-03-27 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-03-26 | 1980-09-25 | 1981-03-27 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-03-26 | 1984-09-25 | 1985-03-27 | $7700.00 | Window Closed / Lapsed |