Detection of falsification of security documents using white light interferometer

In order to verify the authenticity of security documents, we propose the measurement of the surface distortion of the cover film of security documents. Surface shapes of films of 31 genuine documents and 29 counterfeit documents were measured by using a white light interferometer. Differences between the surface features of a genuine security document and those of a counterfeit one were studied. Roughness and peak–valley density were the two features used to characterize the measured surface shape. Only 2 out of 29 counterfeit documents could not be distinguished from the genuine ones by film distortion analysis. The likelihood ratio of this method in the authentication of genuine documents was 14.5. This implies that the proposed method is useful for authentication of genuine documents.