| 摘要 |
T I T L E IMPROVED METHOD FOR ON-LINE THICKNESS MONITORING OF A TRANSPARENT FILM An optical system is described for monitoring the thickness of a translucent film either free-standing or coated on a reflective substrate. A polychromatic light beam is projected onto the surface of the sheet, and the transmitted light is detected at, at least, three wavelengths of which only one corresponds to an absorption band of the film material. By properly processing the three or more detected signals, an accurate evaluation of the film thickness is obtained irrespective of the presence of colored pigments in the material or of wavelength-dependent attenuation due to scattering at the film interfaces. Optical configurations are also described which avoid errors produced by interference fringes or front-surface reflections while simplifying the scanning of the sheet surface. |
