Diffractive indicia for a surface (1) comprising a plurality of small separate diffractive elements (2) and means for a adhering the diffractive elements to the surface. Each diffractive element has a diffractive surface relief structure and is not separately resolvable to the human eye. The appearance...http://www.google.ca/patents/US5912767?utm_source=gb-gplus-sharePatent US5912767 - Diffractive indicia for a surface
