Measurement of thickness of a thin film by means of laser interference at many incident angles |
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| Authors: | Kazuhiko Ishikawa Hitomi Yamano Ki-ichiro Kagawa Katsuhiko Asada Koichi Iwata Masahiro Ueda |
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| Institution: | a Department of Information Science, Faculty of Engineering, Fukui University, Bunkyo 3-9-1, Fukui 910-0017, Japan;b Faculty of Education and Regional Studies, Fukui University, Bunkyo 3-9-1, Fukui 910-0017, Japan;c Department of Mechanical System Engineering, Faculty of Engineering, University of Osaka Prefecture, Gakuen-cho 1-1, Sakai, 599-8531, Osaka, Japan |
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| Abstract: | An optical method for directly measuring the thickness of a thin transparent film has been proposed by means of multi-wave laser interference at many incident angles, and confirmed experimentally by means of equipment made on an experimental basis. Two methods are available: one can be used when an index of refraction of the film, a wavelength λ, and two successive angles of incidence at which the sinusoidal light intensity has minimum values, are known (Method I), and another can be used without an index of film refraction when three successive angles of incidence and a wavelength are known (Method II). The smallest measurable thickness is 1.43λ for Method I, and 2.5λ for Method II. The largest measurable thickness is about 100λ for both methods. The measurement error by means of numerical calculation is Δh/h−1.01×10−2, and that obtained experimentally with an angular resolution of incident light of 0.3° is Δh/h7×10−2 for Method I. The refractive index can also be measured by means of Method II. |
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| Keywords: | Laser interference Film thinckness Refractive index |
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