US4187026A
Expired / Lapsed
US
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Photoacoustic method and apparatus for measuring intensity of electromagnetic radiation
Assignee: Phillips Petroleum Co
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Filing: 1977-09-29
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Granted: 1980-02-05
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Expires: 1997-09-29
Abstract
Abstract Electromagnetic radiation is detected, using a photoacoustic cell employing a uniform absorber of radiation which absorbs independently of wavelength.
Inventors
- 👤 Arnold M. Schaffer
- 👤 John A. Favre
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-04 07:39
CPC Classifications
G; G01; G01J; G01J5/00; G01J5/38; G01J5/42
Claims Analysis
Total Claims: 15
Claim 1
Independent Claim
293 words
A method of measuring the intensity of a beam of electromagnetic radiation, said method comprising: (a) passing said beam of electromagnetic radiation into a monochromator and into a chopper in either possible order, thereby producing a periodically pulsed monochromatic beam of electromagnetic radiation having a chopping frequency f; (b) passing said periodically pulsed monochromatic beam of electromagnetic radiation into a cell which contains carbon black and a gas, at least one wall of said cell being made of a material which transmits electromagnetic radiation substantially independently of wavelength of incident electromagnetic radiation, and said pulsed monochromatic beam of electromagnetic radiation being directed so that it impinges upon said carbon black, thereby producing changes in pressure of said gas located within said cell; (c) detecting said changes in pressure of said gas located within said cell with a microphone which operates in cooperation with said cell and which has a diaphragm that forms a flexible wall of said cell, said microphone producing electrical signals which are representative of said changes in pressure of said gas located within said cell, each of said electrical signals having a component which is out of phase with said pulsed monochromatic beam of electromagnetic radiation and having a component which is in phase with said pulsed monochromatic beam of electromagnetic radiation; (d) amplifying said component which is in phase with said pulsed monochromatic beam of electromagnetic radiation with use of a lock-in amplifier which is locked in to the chopping frequency f, thereby producing an amplified signal; and (e) recording said amplified signal, said carbon black being such that it has a specific surface area (SSA, which is measured in M 2 /g per CTAB absorption test) within the range from about 20 to about 700 m 2 /g.
Claim 2
Independent Claim
293 words
A method of measuring the intensity of a beam of electromagnetic radiation, said method comprising: (a) passing said beam of electromagnetic radiation into a monochromator and into a chopper in either possible order, thereby producing a periodically pulsed monochromatic beam of electromagnetic radiation having a chopping frequency f; (b) passing said periodically pulsed monochromatic beam of electromagnetic radiation into a cell which contains carbon black and a gas, at least one wall of said cell being made of a material which transmits electromagnetic radiation substantially independently of wavelength of incident electromagnetic radiation, and said pulsed monochromatic beam of electromagnetic radiation being directed so that it impinges upon said carbon black, thereby producing changes in pressure of said gas located within said cell; (c) detecting said changes in pressure of said gas located within said cell with a microphone which operates in cooperation with said cell and which has a diaphragm that forms a flexible wall of said cell, said microphone producing electrical signals which are representative of said changes in pressure of said gas located within said cell, each of said electrical signals having a component which is out of phase with said pulsed monochromatic beam of electromagnetic radiation and having a component which is in phase with said pulsed monochromatic beam of electromagnetic radiation; (d) amplifying said component which is in phase with said pulsed monochromatic beam of electromagnetic radiation with use of a lock-in amplifier which is locked in to the chopping frequency f, thereby producing an amplified signal; and (e) recording said amplified signal, said carbon black being such that it has a specific surface area (SSA, which is measured in M 2 /g per CTAB absorption test) within the range from about 20 to about 700 m 2 /g.
Claim 3
Dependent Claim
12 words
A method according to claim 1, wherein said cell contains helium gas.
Claim 4
Dependent Claim
49 words
A method according to claim 2, wherein said wavelengths of said electromagnetic radiation beam are in the wavelength range from vacuum UV to far IR and wherein said material which transmits electromagnetic radiation substantially independently of wavelengths of radiation which is passed into said closed cell is lithium fluoride.
Claim 5
Dependent Claim
26 words
A method according to claim 3 wherein said carbon black has a "structure" within the range from about 0.3 to about 3 cm 3 /100 g.
Claim 6
Dependent Claim
26 words
A method according to claim 3 wherein said carbon black has a "structure" within the range from about 0.7 to about 1.2 cm 3 /100 g.
Claim 7
Dependent Claim
27 words
A method according to claim 4 wherein said carbon black has a specific surface area within the range from about 20 to about 120 m 2 /g.
Claim 8
Independent Claim
215 words
An apparatus comprising: (a) a chopper and a monochromator operating in cooperation with each other, through both of which a beam of electromagnetic radiation is passed in either possible order, thereby producing a pulsed beam of electromagnetic radiation; (b) a cell which contains carbon black and a gas, at least one wall of said cell being made of a material which transmits electromagnetic radiation substantially independently of the wavelength of incident radiation; (c) a microphone having a diaphragm which forms one wall of said cell, said microphone operating in cooperation with said cell so as to detect changes in pressure of said gas located within said cell and so as to produce electrical signals which are representative of changes in pressure of said gas located within said cell, each of said electrical signals having a component which is out of phase with the pulsed beam of electromagnetic radiation and having a component which is in phase with the pulsed beam of electromagnetic radiation; (d) a means for amplifying said components of said electrical signals which are in phase with said pulsed beam of electromagnetic radiation; and (e) a means for recording said amplified signal, said carbon black having a specific surface area (SSA) within the range from about 20 to about 700 m 2 /g.
Claim 9
Independent Claim
215 words
An apparatus comprising: (a) a chopper and a monochromator operating in cooperation with each other, through both of which a beam of electromagnetic radiation is passed in either possible order, thereby producing a pulsed beam of electromagnetic radiation; (b) a cell which contains carbon black and a gas, at least one wall of said cell being made of a material which transmits electromagnetic radiation substantially independently of the wavelength of incident radiation; (c) a microphone having a diaphragm which forms one wall of said cell, said microphone operating in cooperation with said cell so as to detect changes in pressure of said gas located within said cell and so as to produce electrical signals which are representative of changes in pressure of said gas located within said cell, each of said electrical signals having a component which is out of phase with the pulsed beam of electromagnetic radiation and having a component which is in phase with the pulsed beam of electromagnetic radiation; (d) a means for amplifying said components of said electrical signals which are in phase with said pulsed beam of electromagnetic radiation; and (e) a means for recording said amplified signal, said carbon black having a specific surface area (SSA) within the range from about 20 to about 700 m 2 /g.
Claim 10
Dependent Claim
12 words
An apparatus according to claim 7, wherein said cell contains helium gas.
Claim 11
Dependent Claim
24 words
An apparatus according to claim 8, wherein said material which transmits electromagnetic radiation substantially independently of the wavelength of incident radiation in lithium fluoride.
Claim 12
Dependent Claim
26 words
An apparatus according to claim 9 wherein said carbon black has a "structure" within the range from about 0.3 to about 3 cm 3 /100 g.
Claim 13
Dependent Claim
26 words
An apparatus according to claim 9 wherein said carbon black has a "structure" within the range from about 0.7 to about 1.2 cm 3 /100 g.
Claim 14
Dependent Claim
27 words
An apparatus according to claim 9 wherein said carbon black has a specific surface area within the range from about 20 to about 120 m 2 /g.
Claim 15
Dependent Claim
27 words
A method according to claim 5 wherein said carbon black has a specific surface area within the range from about 20 to about 120 m 2 /g.
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) | 1983-02-04 | 1983-08-06 | 1984-02-05 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1987-02-04 | 1987-08-06 | 1988-02-05 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1991-02-04 | 1991-08-06 | 1992-02-05 | $7700.00 | Window Closed / Lapsed |