Infrared multilayer film thickness measuring method and apparatus
First Claim
1. An infrared multilayered film thickness measuring method comprising the steps of:
- projecting an infrared ray including a plurality of sample wavelengths and at least one reference wavelength onto a composite multilayer film or sheet composed of a plurality of film layers of different synthetic resins, the infrared absorption wavelengths of each of the film layers coinciding with at least one of the sample wavelengths and the reference wavelength being selected not to coincide with the infrared absorption wavelength of each film layer;
obtaining ratios between the amounts of infrared rays of the respective sample wavelengths transmitted through the multilayer film and the amount of infrared rays of the reference wavelength transmitted through the multilayer film;
performing an operation for solving a simultaneous equation including the ratios and the infrared absorption coefficients of the film layers at the sample and reference wavelengths as coefficients and the thicknesses of the film layers as unknowns, thereby obtaining the thicknesses of the film layers.
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Abstract
A method and an apparatus for measuring the thicknesses of film layers of different synthetic resins forming a composite multilayer film or sheet by utilizing infrared rays. Infrared rays of sample wavelengths, each equal to the infrared absorption wavelength of each film layer, and at least one reference wavelength different from the infrared absorption wavelength of each film layer are projected onto the multilayer film to be measured. Ratios are obtained between the amounts of infrared lights of the sample and reference wavelengths transmitted through the multilayer film. An operation is achieved for solving a simultaneous equation including the ratios and the infrared absorption coefficients of the film layers at the sample and reference wavelengths as coefficients and the thicknesses of the film layers as unknowns, thereby obtaining the thicknesses of the film layers.
36 Citations
21 Claims
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1. An infrared multilayered film thickness measuring method comprising the steps of:
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projecting an infrared ray including a plurality of sample wavelengths and at least one reference wavelength onto a composite multilayer film or sheet composed of a plurality of film layers of different synthetic resins, the infrared absorption wavelengths of each of the film layers coinciding with at least one of the sample wavelengths and the reference wavelength being selected not to coincide with the infrared absorption wavelength of each film layer; obtaining ratios between the amounts of infrared rays of the respective sample wavelengths transmitted through the multilayer film and the amount of infrared rays of the reference wavelength transmitted through the multilayer film; performing an operation for solving a simultaneous equation including the ratios and the infrared absorption coefficients of the film layers at the sample and reference wavelengths as coefficients and the thicknesses of the film layers as unknowns, thereby obtaining the thicknesses of the film layers. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. An infrared multilayer film thickness measuring apparatus comprising:
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a projector unit for projecting an infrared ray including a plurality of sample wavelengths and at least one reference wavelength onto a composite multilayer film layers of different synthetic resins, the infrared absorption wavelength of each of the film layers coinciding with at least one of the sample wavelengths and the reference wavelength being selected not to coincide with the infrared absorption wavelength of each film layer; a photo detector unit for receiving an infrared ray transmitted through the multilayer film at least once to detect the intensity of transmitted infrared light; and an electrical processing unit for separating a light-intensity signal from the photo detector unit into sample signals indicating the intensity of infrared lights of the sample wavelengths and a reference signal indicating the intensity of the infrared light of the reference wavelength, obtaining ratios between the sample signals and the reference signal and solving a simultaneous equation including the ratios and the infrared absorption coefficients of the film layers at the sample and reference wavelengths as coefficients and the thicknesses of the film layers as unknowns, thereby obtaining the thicknesses of the film layers. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18, 19, 20, 21)
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Specification