Importance

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Abstract

Extended area lighting devices include a light guide and diffractive surface features on a major surface thereof. The diffractive surface features include diffractive features of different pitches in non-overlapping regions of the major surface tailored to extract guided-mode light of different colors from the light guide in different directions. The diffractive features extract light such that an ordinary user observes substantially different colors in different regions of the light guide, providing a colorful appearance. Notwithstanding this, the diffractive features also extract light such that the lighting device illuminates a reference surface, disposed at an intermediate distance from the light guide, with illumination light that is substantially uniform in color and substantially white. Optical films having diffractive features that can be used to construct such devices and light guides are also disclosed. The concept can also be extended to embodiments in which the uniform color illumination light is not substantially white.

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First Claim