1 September 1996 Low-density diffractive optical memories for document security
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A low-density diffractive optical write-once, read multiple times memory (WORM) is demonstrated that authenticates and secures documents. Furthermore, by encoding the machine-readable optical code, information can be linked to the document. The proposed solution leads to a reliable, high security machine-readable information carrier that is fully compatible with the requirements of typical security documents, such as payment substrates, fiduciary papers, passports, and identity cards. The information carrier is a juxtaposition of diffractive structures. Data are written permanently in an optical memory; the diffractive structure is changed irreversibly through the interaction of a diffractive surface with a beam of laser light. A prototype low-density optical memory based on diffractive structures that are resilient against copying or reorigination is realized for use in securing official travel documents.
Wayne Robert Tompkin, Rene Staub, "Low-density diffractive optical memories for document security," Optical Engineering 35(9), (1 September 1996). https://doi.org/10.1117/1.600855


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