Contrôle de l'épaisseur de couches minces.

摘要

A method is described for monitoring the thickness and uniformity of a transparent coating applied to a substrate in sheet form. The method comprises directing polychromatic light at the coating at a plurality of locations and measuring the intensity of light reflected from said coating. At each location, the intensity of reflected light is measured at at least two discrete monitoring wavelengths and said measurements are processed to generate an electrical signal which may be compared with one or more predetermined threshold values and with such electrical signals generated at other locations to yield indications of whether the thickness and uniformity of the coating lies within predetermined tolerance values.. The first discrete monitoring wavelength lies in the range 400 to 480 nm (blue) and the second discrete monitoring wavelength lies in the range 580 to 750 nm (red). A third discrete monitoring wavelength, which lies in the range 480 to 580 nm (green) may also be used. The monitoring results may be used to adjust the coating process.