An optical device comprising a first surface with a plurality of micro sized facets, each facet having a respective orientation. Said plurality of facets having an optical axis which extends parallel to the normal vector to an average orientation of all said respective orientations. The plurality of facets comprising at least a first and a second group of facets, each group is formed by a respective number of at least twenty-five compactly arranged neighboring facets. Each group is arranged to generate during operation a respective, mutually identical whole pattern. Each facet in a respective group is arranged to display a sub-pattern of said respective whole pattern. The whole patterns are mutually superpositioned.