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Proceedings Paper

Diffractive optical variable image devices generated by maskless interferometric lithography for optical security
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Paper Abstract

In optical security (protection against forgery and counterfeit of products and documents) the problem is not exact reproduction but the production of something sufficiently similar to the original. Currently, Diffractive Optically Variable Image Devices (DOVID), that create dynamic chromatic effects which may be easily recognized but are difficult to reproduce, are often used to protect important products and documents. Well known examples of DOVID for security are 3D or 2D/3D holograms in identity documents and credit cards. Others are composed of shapes with different types of microstructures yielding by diffraction to chromatic dynamic effects. A maskless interferometric lithography technique to generate DOVIDs for optical security is presented and compared to traditional techniques. The approach can be considered as a self-masking focused holography on planes tilted with respect to the reference optical axes of the system, and is based on the Scheimpflug and Hinge rules. No physical masks are needed to ensure optimum exposure of the photosensitive film. The system built to demonstrate the technique relies on the digital mirrors device MOEMS technology from Texas Instruments' Digital Light Processing. The technique is linear on the number of specified colors and does not depend either on the area of the device or the number of pixels, factors that drive the complexity of dot-matrix based systems. The results confirmed the technique innovation and capabilities in the creation of diffractive optical elements for security against counterfeiting and forgery.

Paper Details

Date Published: 26 July 2011
PDF: 8 pages
Proc. SPIE 8001, International Conference on Applications of Optics and Photonics, 800121 (26 July 2011); doi: 10.1117/12.890750
Show Author Affiliations
Alexandre Cabral, Univ. de Lisboa (Portugal)
José M. Rebordão, Univ. de Lisboa (Portugal)

Published in SPIE Proceedings Vol. 8001:
International Conference on Applications of Optics and Photonics
Manuel Filipe Costa, Editor(s)

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