Process and device for qualitative and quantitative measurement of irregularities and impurities on and in transparent or semitransparent flexible sheet materials

摘要

Disclosed is a process for the qualitative and quantitative measurement of irregularities and impurities on and in transparent or semitransparent flexible sheet materials, comprising the steps of producing interference fringes by obliquely directing a light beam onto the surface of a sheet to be examined to produce two partial beams; placing the sheet to be examined on a reflecting reference surface and forming the partial beams by reflection from this reference surface and from the surface to be examined; superposing the two partial beams, whereby an interference field is obtained which is equivalent to the surface profile of the sheething to be examined; evaluating the interference field to determine the extension of the surface profile; additionally irradiating the sheet by a polarized light beam; passing the polarized light beam through a second polarizer; and evaluating the polarized light beam after passing through the second polarizer. Also disclosed is an apparatus for carrying out this process.