| 摘要 |
PURPOSE:To measure the thickness of a sheet-like object, by detecting the high or low intensity of the light owing to interference that appears in transmitted or reflected light when monochromatic light of variable wavelengths is irradiated to said object as a function of the wavelength. CONSTITUTION:The monochromatic light irradiated to a film 6 is conduced to a photosensor 19 by repeating the reflection at an angle theta and the transmission through the film 6 in reflection parts 17 and 18. When the monochromatic light is transmitted through the film 6, the light is reflected partly on the front and rear surfaces of the film 6 and the transmittance thereof is changed by the interference of the reflected light and the rectilinear light. If the wavelengths forming the adjacent crest and crest of the wave of the transmitted light when a prism 13 is rotated and the monochromatic light of continuously varying wavelengths is irradiated to the film 6 are designated as lambda1 and lambda2, the relation l=(1/2ncostheta).[1/(1-lambda1)-(1-lambda2)] holds, and if the refractive index (n) of the film and the incident angle theta of the light are beforehand determined, the thickness l of the film 6 is determined continuously from the output E3 of an arithmetic part 19. The above-mentioned E3 is calculated from the signals E1, E2 corresponding respectively to the wavelength lambda and the quantity of the light transmitted through the film 6. |
