HOLOGRAMS HAVING A STANDARD REFERENCE COLOUR

摘要

Holograms and diffraction gratings are described wherein the presence of a "key-colour" (Magenta) permits an observer to identify the position where all the other colours of the hologram in question can be univocally determined. Two set of spectra (60 and 70) are provided such that at a predetermined angle (13) a reference beam of incident white-light (10) illuminating the hologram or diffractin grating composition will cause the observer (11) to see the color "Magenta" which is to be used as a reference "key-colour".