  A new method for document watermarking based on the digital Fourier hologram
is proposed. It applies the methods of digital image watermarking based on
holographic principle presented previously in several papers into printed
documents. Experimental results show that the proposed method can not only meet
the demand on invisibility, robustness and non-reproducibility of the document
watermark, and but also has other advantages compared with the conventional
methods for document securities such as embossed hologram, Lippmann photograph
and halftone modulation.
