| 摘要 |
PCT No. PCT/EP93/01437 Sec. 371 Date Dec. 8, 1994 Sec. 102(e) Date Dec. 8, 1994 PCT Filed Jun. 8, 1993 PCT Pub. No. WO93/25941 PCT Pub. Date Dec. 23, 1993Holograms 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 are provided such that at a predetermined angle a reference beam of incident white-light illuminating the hologram or diffraction grating composition will cause the observer to see the color "Magenta" which is to be used as a reference "key-colour".
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