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Proceedings Paper

CPLgram: an advanced machine-readable OVD that is obtained by combining diffraction gratings and liquid crystals
Author(s): Itsuo Takeuchi; Kenji Yamamotoya; Tsugutaka Sugahara; Hidekazu Hoshino; Hiroyuki Matsumoto; Tsutomu Matsumoto
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Paper Abstract

Diffraction gratings and liquid crystals are use4d as security features for document protection. We have studied the combination of these two features and have developed an optically variable device which is called 'CPLgram'. CPLgram is made of thin film of high polymer cholesteric liquid crystals which exhibit diffraction of light. The combination of diffraction gratings and cholesteric liquid crystals provides light diffraction, wavelength selectivity, color- shifting of reflection and circular polarization selectivity, for the deice. These characteristics make it vary difficult to counterfeit the devices. In our understanding, it is a new approach to combine these security features. The most striking characteristic of the combination is significant aspect of the combination is that customers can choose a device verification method from three types of methods depending on security requirements and/or cost demands; to examine the device (a) with the naked eye, (b) with a simple inspection tool, and (c) by verification equipment.

Paper Details

Date Published: 7 April 2000
PDF: 9 pages
Proc. SPIE 3973, Optical Security and Counterfeit Deterrence Techniques III, (7 April 2000); doi: 10.1117/12.382193
Show Author Affiliations
Itsuo Takeuchi, NHK Spring Co., Ltd. (Japan)
Kenji Yamamotoya, NHK Spring Co., Ltd. (Japan)
Tsugutaka Sugahara, NHK Spring Co., Ltd. (Japan)
Hidekazu Hoshino, NHK Spring Co., Ltd. (Japan)
Hiroyuki Matsumoto, NHK Spring Co., Ltd. (Japan) and Yokohama National Univ. (Japan)
Tsutomu Matsumoto, Yokohama National Univ. (Japan)


Published in SPIE Proceedings Vol. 3973:
Optical Security and Counterfeit Deterrence Techniques III
Rudolf L. van Renesse; Willem A. Vliegenthart, Editor(s)

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