Patent ID: 8254029

Claim:
A surface relief structure comprising: a recording medium configured to be structurally modified when exposed to interfering and non-interfering portions of radiation beams, the structurally modified recording medium including, when viewed in a two-dimensional cross-section along one of axes of the recording medium: a plurality of substantially equal height steps of fine-sized periodicity superimposed upon a plurality of deep depressions of substantially coarse-sized periodicity defined by a crossed grating, with steps of the plurality of substantially equal height steps being stepped in only two directions and including landing portions varying non-uniformly in at least one of the only two directions, the plurality of substantially equal height steps stepped in the only two directions in each of the plurality of deep depressions defining an asymmetric stepped profile, wherein the plurality of deep depressions of coarse-sized periodicity on which the plurality of substantially equal height steps are superimposed are skewed relative to edges of the two-dimensional cross-section view of the recording medium such that the deep depressions are not perpendicular to all of the edges of the two-dimensional cross-section view of the recording medium, the structurally modified recording medium defined using the crossed grating is configured to produce in reflection substantially a single color in a broad spectral range when illuminated by a source of light.