Patent ID: 8184236
Filing Date: 2012-05-22
Classification: G02B

Abstract:
1. A lighting device comprising: a light-guiding plate by which light entering from an edge surface is outputted in a thickness direction of the light-guiding plate; a plurality of light sources disposed near the edge surface of the light-guiding plate, aligned in a width direction of the light-guiding plate and configured to emit light in a length direction of the light-guiding plate; and a plurality of diffractive optical elements disposed in the edge surface of the light-guiding plate to face the light sources, respectively, wherein among the plurality of diffractive optical elements, the diffusion angle of the diffractive optical elements which are disposed near the center differs from the diffusion angle of the diffractive optical elements which are disposed near the edge, and wherein the diffractive optical elements are formed of a concave and convex pattern provided in the edge surface of the light-guiding plate and distributed in two-dimensional directions which consist of the width direction of the light-guiding plate and the thickness direction of the light-guiding plate, and level differences between an uppermost surface and a lowermost surface of the concave and convex pattern in the length direction of the light-guiding plate are uniform, and wherein the diffusion angle of the diffractive optical elements disposed near the center is smaller than the diffusion angle of the diffractive optical elements disposed near the edge.