Authentication of articles by white light interferometry and birefringence

摘要

The present invention provides a method of authenticating the provenance of an article marked with a removable transparent polymer film comprising measuring the thickness of the removable transparent film while still located on the article or of a layer within the film while still located on the article by white light interferometry. Alternatively, or in addition, the method comprises measuring the birefringence of the removable transparent polymer film while still located on the article or of a layer within the film while still located on the article.