Synthetic double-exposure method for security holograms: image estimation based on numerical simulation

Nobukazu Yoshikawa; Masahide Itoh; Toyohiko Yatagai

doi:10.1117/12.347733

7 May 1999 Synthetic double-exposure method for security holograms: image estimation based on numerical simulation

Nobukazu Yoshikawa, Masahide Itoh, Toyohiko Yatagai

Proceedings Volume 3740, Optical Engineering for Sensing and Nanotechnology (ICOSN '99); (1999) https://doi.org/10.1117/12.347733
Event: Optical Engineering for Sensing and Nanotechnology (ICOSN '99), 1999, Yokohama, Japan

Abstract

We have developed a synthetic double exposure (SDE) method of the computer-generated holograms (CGHs) for security applications. This method is based on incoherent multiplexing of two types of coding methods on binary CGHs: a cell-oriented and a point-oriented. The CGH synthesized by the SDE can have multiple image planes from the image region to the Fraunhofer region. In fabrication process of the SDE, the point-oriented CGH, that is, the image-type hologram is erased slightly by the cell-oriented CGH. We estimate here the image quality and the diffraction efficiency of the reconstructed image in the image-type hologram by the SDE using numerical simulations. In our simulations, the cell-oriented CGH occupied only 14% of the entire hologram area. The diffraction efficiency of the image-type hologram by the SDE was about 80%. Therefore, the information of the image-hologram was preserved sufficiently. The CGH including image-, Fresnel- and Fourier-type holograms was fabricated using the direct writing of electron-beam resist in electron-beam lithography. These reconstructed images were almost identical to the desired ones.

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Nobukazu Yoshikawa, Masahide Itoh, and Toyohiko Yatagai "Synthetic double-exposure method for security holograms: image estimation based on numerical simulation", Proc. SPIE 3740, Optical Engineering for Sensing and Nanotechnology (ICOSN '99), (7 May 1999); https://doi.org/10.1117/12.347733

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KEYWORDS

Holograms

3D image reconstruction

Computer generated holography

Computer security

Image quality

Light sources

Lithography

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