After a brief description of the threats which face the issuers of documents and valuable papers, the concept of thin film anticounterfeiting coatings proposed by the NRCC is explained. The colorimetric considerations which govern the design of such devices are reviewed. Typical coating designs suitable for use in transmission and reflection are discussed. Reflection coatings can be constructed with and without an integral black absorber coating. The need for geometric patterns in the anticounterfeiting coating is explained. Various methods for producing such logos are proposed. Mention is made of the various numerical tools developed for the design and investigation of single films and multilayers, their desensitization to construction errors, and for the investigation of different process control strategies. During the duration of the project, experiments were performed on the optical constants and nonoptical properties of a number of metal and dielectric films considered for use in the anticounterfeiting coatings. These and some of the processes and equipment investigated during the development of a prototype production facility are reviewed. Finally, some security and economic aspects of the devices are considered.
© 1989 Optical Society of AmericaFull Article | PDF Article
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