| 摘要 |
PCT No. PCT/EP96/05114 Sec. 371 Date Apr. 29, 1998 Sec. 102(e) Date Apr. 29, 1998 PCT Filed Nov. 20, 1996 PCT Pub. No. WO97/19821 PCT Pub. Date Jun. 5, 1997An optically variable surface pattern includes at least one graphic representation producing an achromatic impression when viewed in visible light over a certain angular range without noticeable color fringes occurring in the adjoining angular ranges. A plane surface portion includes a grating structure which disperses incident light with comparable intensity into a cone within a predetermined angle range regardless of differing wavelength. An overlap of several successive high orders of diffraction results in a recombination of the dispersed light to white light at any diffraction angle within the cone. The surface portion viewed from a direction within the cone reflects white light, in contrast to a simple flat mirror which has a very narrow range of specular reflection. At viewing angles outside the cone, the surface portion is dim or dark grey. The shape of the surface portion is then recognized as an area white lit or dark depending upon a particular viewing angle relative to incident light. |
