| 摘要 |
<p>When a diffractive device (2) is illuminated by a light source, it generates one or more diffraction images which are observable from particular ranges of viewing angles around the device. The device comprises a substrate (6), a diffractive structure (3) embossed into or adhered onto the substrate, a first substantially transparent layer (7) over the diffractive structure, light splitting means (8, 10, 11) over the first substantially transparent layer, and a second substantially transparent layer (9) over the light splitting means. The light splitting means protects the diffractive device against replication using near field or far field imaging procedures which require coherent light illumination.</p> |
