Patent ID: 6456437
Filing Date: 2002-09-24
Classification: F21V,F21Y,G02B

Abstract:
An optical sheet suitable for spreading light, in which a first major surface of the sheet is a structured surface comprising an array of prisms such that, if the second major surface of the sheet is substantially smooth, a normally-incident beam of light that enters the sheet through the second major surface and leaves through the array of prisms will be spread by the latter;wherein the array comprises: (a) a plurality of reflection prisms selected to deviate the normally-incident light through different angles and a plurality of refraction prisms selected to deviate the normally-incident light through different angles, in which successive reflection prisms are separated by at least one refraction prism; or (b) a non-ordered arrangement of a plurality of reflection prisms selected to deviate the normally-incident light through different angles; or (c) a non-ordered arrangement of a plurality of refraction prisms selected to deviate the normally-incident light through different angles; in which each refraction prism deviates the normally-incident light only by refraction at a prism facet as the light leaves the sheet through the first major surface and each reflection prism deviates the normally-incident light by total internal reflection within the prism before the light leaves the sheet through the first major surface.