Authentication of articles

Abstract

Authentication apparatus (1, 100) and methods which authenticate an item (4, 110) responsive to the detection that a portion of the item has one or more predetermined characteristics, the said predetermined characteristics comprising either or both the thickness of the said portion of the item, and the thickness of one or more layers within the said portion of the item, determined by optically-based thickness measuring apparatus (6, 102-108). The item may be a product and the portion of the item may be a sheet of packaging material. The item may be a security document and the portion of the item may be a sheet of security document substrate.

Dependencies are inferred from the claim text.