US3854044A
Expired / Lapsed
US
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A method and apparatus for measuring a transmission spectrum of a film
Assignee: Imperial Chemical Industries Ltd
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Filing: 1973-03-12
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Granted: 1974-12-10
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Expires: 1993-03-12
Abstract
Abstract A method for measuring a transmission spectrum of a film having a thickness which is of a similar order of magnitude to the wavelengths of the radiation used in the measurements, comprises directing the radiation onto the film thereby dividing the radiation into a transmitted beam and a returned beam, each beam individually having interference fringes caused by internal reflection within the film, and measuring at said wavelengths the total intensity of substantially all of both of the beams or substantially equal portions thereof, so as to mutually cancel the intensity variations with wavelength due to the interference fringes of the individual beams. The method enables precise measurements to be made because a narrow band width can be used without producing the interference errors previously associated with high resolution measurements of absorption by thin films.
Inventors
- 👤 B Stay
- 👤 H Willis
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-24 07:57
CPC Classifications
G; G01; G01N; G01N21/00; G01N21/84; G01N21/86
Claims Analysis
Total Claims: 17
Claim 1
Independent Claim
103 words
A method for measuring a transmission spectrum of a film having a thickness which is of a similar order of magnitude to the wavelengths of the radiation used in the measurement, which method comprises directing the radiation onto the film thereby dividing the radiation into a transmitted beam and a returned beam, each beam individually having interference fringes caused by internal reflection within the film, and measuring at said wavelengths the total intensity of at least substantially equal portions of both of said beams, so as to mutually cancel the intensity variations with wavelength due to the interference fringes of the individual beams.
Claim 2
Independent Claim
103 words
A method for measuring a transmission spectrum of a film having a thickness which is of a similar order of magnitude to the wavelengths of the radiation used in the measurement, which method comprises directing the radiation onto the film thereby dividing the radiation into a transmitted beam and a returned beam, each beam individually having interference fringes caused by internal reflection within the film, and measuring at said wavelengths the total intensity of at least substantially equal portions of both of said beams, so as to mutually cancel the intensity variations with wavelength due to the interference fringes of the individual beams.
Claim 3
Dependent Claim
27 words
A method according to claim 1 which comprises separately detecting and measuring the intensities of the two beams, and combining the measurements to provide the required measurement.
Claim 4
Dependent Claim
29 words
A method according to claim 1 which comprises combining at least substantially equal portions of both the transmitted and returned beams and measuring the intensity of the combined beams.
Claim 5
Dependent Claim
88 words
A method according to claim 1 for determining the absorption by the film at selected wavebands, which comprises directing onto the film, at least two wavebands of radiation including one waveband at which absorption is to be measured and a reference waveband at which there is substantially no selective absorption by the film, and measuring at both wavebands the total intensity of at least substantially equal portions of both of the beams, and determining the ratio of the measurements in respect of the absorbed waveband and reference waveband.
Claim 6
Dependent Claim
44 words
A method according to claim 1 for measuring during the continuous production of a film, a parameter of the film determined from the transmission spectrum, the method comprising feeding back details of the parameter to means for controlling the parameter during the film production.
Claim 7
Dependent Claim
89 words
Apparatus for measuring a transmission spectrum of a film having a thickness which is of a similar order of magnitude to the wavelength of the radiation used in the measurements, which apparatus comprises a source of radiation, means for providing a sufficiently narrow bandwidth to produce interference fringes in both returned and transmitted beams taken individually, means for detecting the radiation, means for directing at least substantially equal portions of both of the beams to the detecting means, and means for measuring the total output from the detecting means.
Claim 8
Dependent Claim
89 words
Apparatus for measuring a transmission spectrum of a film having a thickness which is of a similar order of magnitude to the wavelength of the radiation used in the measurements, which apparatus comprises a source of radiation, means for providing a sufficiently narrow bandwidth to produce interference fringes in both returned and transmitted beams taken individually, means for detecting the radiation, means for directing at least substantially equal portions of both of the beams to the detecting means, and means for measuring the total output from the detecting means.
Claim 9
Dependent Claim
23 words
Apparatus according to claim 6 in which all reflecting surfaces of the means directing the beams to the detecting means, are specular reflectors.
Claim 10
Dependent Claim
42 words
Apparatus according to claim 6 which comprises means for directing at least substantially equal portions of both the traNsmitted and returned beams to a common detector, whereby the output from the detector represents the sum of the intensities of the directed beams.
Claim 11
Dependent Claim
45 words
Apparatus according to claim 8 having on one side of the film the common detector positioned to receive one of the beams, and on the other side of the film a specular reflector aligned to direct the other beam through the film to the detector.
Claim 12
Dependent Claim
35 words
Apparatus according to claim 6 having means for selecting and directing onto the film at least two wavebands of the radiation, including a reference waveband and a waveband at which absorption is to be measured.
Claim 13
Dependent Claim
38 words
Apparatus according to claim 10 in which the radiation of each of the wavebands travels along substantially the same paths as that of the other bands, the radiation of different bands being sequentially detected by a common detector.
Claim 14
Dependent Claim
31 words
Apparatus according to claim 6 having means for attenuating the intensity of one of the beams whereby the intensity of the fringes of the two beams may be made substantially equal.
Claim 15
Dependent Claim
21 words
Apparatus according to claim 6 having means for directly supporting the film immediately under the part of the film being viewed.
Claim 16
Dependent Claim
27 words
Apparatus according to claim 13 in which the support means comprises a roller which is rotatable in synchronism with the movement of the film contacting its surface.
Claim 17
Dependent Claim
45 words
Apparatus according to claim 6 for measuring during the continuous production of a film, a parameter of the film determinable from the transmission spectrum, the apparatus being adapted to feed back details of the parameter to means for controlling the parameter during the film production.
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) | 1977-12-09 | 1978-06-10 | 1978-12-10 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-12-09 | 1982-06-10 | 1982-12-10 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-12-09 | 1986-06-10 | 1986-12-10 | $7700.00 | Window Closed / Lapsed |