Interferometric Method for Determining the Thickness of Multilayered Structures in Production Applications, 1990 Polymers, Laminations & Coatings Conference Proceedings

The presentation describes an interferometric method for determining the thickness distribution of multilayered plastic films, sheets and coatings. The method is based on the Michelson white light interferometer and utilizes the fact that the interfaces between the layers cause light reflection.

In addition to accuracy and reliability the advantage of the interferometric principle is its capability of measuring separately the layers of the same materials in the A-B-C-B-A constructions. The principle can also be used for multilayered coatings.

The major limitations are the requirements of transparent or semi-transparent structures and stationary test samples.

A practical off-line application of the interferometric principle is described thoroughly. The measurement and reporting are automated. A strip of film can be analyzed in seconds, with detailed report printed within less than a minute.

User examples and different applications are listed. During the past few years the principle has been successfully used for packaging coextrusions, laminations and coated products in both production and R&D environments. Among the reference users better layer thickness control has resulted time savings, material savings and better quality.