| 摘要 |
PURPOSE:To measure the thickness of a film even during the movement of an object of measurement by providing a photodetection part, a light projection part, and a parallel light generating means which collimates light from the light projection part into parallel light, and guiding the light from the parallel light generating means to a spectroscope. CONSTITUTION:Light from a white light source 1 is converged on a pinhole 3 by a lens group 2 and a collimator lens 4 collimates the light from the pinhole 4 into the parallel light. This parallel light illuminates a film thickness measurement point 14 at a constant angle through an incidence window 17 and is reflected by a surface to be measured. In this case, even if the direction of the reflection varies irregularly owing to wrinkles, etc., of the object of measurement, the reflected light is photodetected at any photodetection position with the same efficiency as long as the variation is within a range of + or -45 deg. abaut the the regular direction of reflection. This photodetected light is propagated in an optical fiber and projected from the end surface of the light projection part 19. When the parallel light is reflected by the measurement object surface, the light varies in spectral intensity. This variation depends upon the film thickness as long as the refractive index of the object of measurement is constant, so variation in the spectral intensity is detected to find the film thickness. |
