| 摘要 |
PURPOSE:To enable measurement of a relatively thin film and a double-layer film using a normal spectrophotometer, by measuring a transmission or reflection spectrum of a sample existing on the surface of a film to be measured. CONSTITUTION:First, a transmission or reflection spectrum of a material 20 existing on the surface of a film to be measured is measured with a spectrophotometer 100 to be stored 40 over a fixed range of wave number. Then, an interference graphic is calculated 49 by Fourier cosine transform of the spectrum 41. Then, optical distance is determined between the main maximum 52 and the submaximum 53 of the interference graphic to compute 50 the thickness of the film being measured. Then, when a double-layer film is to be measured, two sub signals and a main signal that would be obtained in the use of a relative thin film are multiplied by a third coefficient and moreover, two sub signals obtained by positively or negatively shifting the sub signals by a fixed optical path difference added to by a first constant are added to the results to obtain a synthetic interference graphic. Then, coincidence is calculated between a calculated interference graphic 51 and the synthetic interference graphic and an optical path difference at which the coincidence reaches its max. is determined as optical distance thereby enabling measurement of the thickness of the film being measured.
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