| 摘要 |
PURPOSE:To perform the on line measurement by a simple measuring system in the measurement of the thickness of the surface film, by utilizing the correlation between the wavelength of irradiated light and light absorption rate, and performing computation. CONSTITUTION:The film of hydrated chromium oxide and the like is applied to a galvanized steel plate 10 by a film forming device 12, and the film coated steel plate 14 is continuously manufactured. Light beams, which have different light absorbing characteristics for the surface films and have two wavelength lambda1 and lambda2 are simultaneously irradiated to the corresponding points before and after the formation of the film on the materials to be measured 10 and 14 from light sources 20 and 40, respectively. The components lambda1 and lambda2 of the reflected light beams are separated by semi-transparent mirrors 22 and 42 and filters 24, 26, 44, and 46. The intensities of the reflected light beams corresponding to the components are detected by detectors 28, 30, 48, and 50. In an operator 52, a ratio R between a reflected light intensity ratio -Ilambda2/-Ilambda1 from the galvanized steel plate and the reflected light intensity ratio Ilambda<2>/Ilambda1 from the film coated steel plate is obtained, and the film thickness is obtained by using the correlation between the ratio and the film thickness (d). |
