Patent ID: 8807817

Claim:
A luminaire, comprising: a light guide having an optical axis and a first major surface, the first major surface having a plurality of diffractive surface features therein adapted to couple guided-mode light out of the light guide; and one or more light sources disposed to inject light into the light guide; wherein the plurality of diffractive surface features comprise diffractive surface features of different pitches; wherein the diffractive surface features extract guided-mode light from the light guide such that an ordinary user of the luminaire observes substantially different colors in different regions of the light guide at a viewing geometry; and wherein the diffractive surface features and the light source(s) in combination are tailored to provide illumination of a substantially uniform color at a reference surface of interest perpendicular to the optical axis and separated from the light guide by an intermediate distance D, and wherein the substantially uniform color is also substantially white.