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NanoCODES: Nanofabrication of Cellular Optical Device Encryption Surfaces

Dr Robert Lee

Document Security Microtechnology, CSIRO Manufacturing & Infrastructure Technology

3.30pm, Friday 6 August 2004, AR103 Seminar Room, Graduate Research Centre

This talk describes a new approach to the design of optically variable devices for anti-counterfeiting applications. Using arrays of micro-mirror pixels of very small size instead of arrays of miniature diffraction gratings we show how the embossed hot stamping foil transfer step may be replaced by a much simpler transfer process involving only the use of reflective nanophase inks and an embossed printing process. This simpler step provides a means for reducing the OVD replication costs as well as providing for a more integrated process in producing the security document and is a result of the greatly increased microstructure depth characteristics of the NanoCODES structures.

The optical physics associated with NanoCODES is analysed and it is demonstrated that the reflective pixel ray equations are in isomorphic correspondence with the ray equations associated with diffractive devices. This mathematical analysis shows how the optical effects generated by diffractive devices can be mapped into a corresponding set of reflective optical effects. With the exception of colour effects all other characteristics of a diffractive OVD carry over into the reflective case.

The origination process for NanoCODES devices is also discussed, and while more complex than the process used for diffractive devices (because of the extra photolithography step) the test results confirm the viability of the process.

Finally the application of the technology to the design of generic classes of micro mirror OVD devices tuned to end user data encoding for ID applications is also discussed in the context of the rapid growth in ID fraud at the present time.

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