Patent ID: 8684588
Filing Date: 2014-04-01
Classification: G02B

Abstract:
1. A light guide element comprising: a light-emitting section including a light-emitting surface by which to perform surface emission of light coming from a light source having a shape similar to a dot; a light guide section arranged to guide the light coming from the light source to the light-emitting section, the light guide section being configured so that a light-emitting section of another light guide element is placed on the light guide section; and a diffusing device arranged to diffuse incident light, the diffusing device being provided in the light guide section only within a region extending from (i) a boundary between the light-emitting section and the light guide section to (ii) a point halfway between the boundary and that end of the light guide section which is closer to the light source; wherein the light guide element has a thickness direction perpendicular to a plane of extension of a substrate on which the light source is provided and a length direction orthogonal to the thickness direction of the light guide element and extending from the light guide section to the light-emitting section; a first plane passing through the halfway point perpendicularly to the length direction, the region is represented by Z falling within a range of: where Z is a distance from the boundary to the first plane; θ is an angle of inclination formed between the plane of extension of the substrate and a rear surface of the light guide section, the rear surface of the light guide section continuing into a rear surface of the light-emitting section opposite the light-emitting surface; Φ is a total reflection critical angle of the light guide element, and h is a thickness of that end of the light guide section which is closer to the light source; and the light-emitting surface is constituted by (i) a horizontal surface facing an object to be irradiated and (ii) an inclined surface provided between the horizontal surface and the light guide section and inclined at continuously varying angles to the horizontal surface to define a curved surface at which the inclined surface is connected to the horizontal surface.