An information bearing credit or identification card in which pieces of a diffraction grating, preferably an embossed hologram, are randomly distributed in a plastic or paper card so that light reflecting therefrom uniquely and visually differentiates the grating and hence the card. The pieces may be...http://www.google.fr/patents/US4547002?utm_source=gb-gplus-shareBrevet US4547002 - Credit and identification cards having pieces of diffraction grating therein
Credit and identification cards having pieces of diffraction grating therein
