Apparatus and method for generating diffractive element using liquid crystal display

摘要

The invention relates to an authentication structure comprising: a layer of material; a diffractive structure formed within said layer of material; and a non-diffractive micro-graphical feature providing security information embedded within said diffractive structure formed within said layer of material; said diffractive structure and said non-diffractive micro-graphical feature being integrally formed within substantially disjoint non-overlapping regions of said layer of material, said micro-graphical feature comprising a plurality of non-diffractive graphical structures including at least one alpha-numerical or symbolic character embedded in a surround of said diffractive structure, said non-diffractive micro-graphical feature not overlying or underlying said diffractive structure; said diffractive structure generating an optical characteristic which is dependent upon either or both of a direction of irradiation of said diffractive structure and a direction of sensing a transmission or reflection of said irradiation through or from said diffractive structure; and said non-diffractive micro-graphical feature having a substantially constant optical characteristic substantially independent of either or both of said direction of said irradiation and said direction of sensing said transmission or reflection of said irradiation through or from said non-diffractive structure.