Patent ID: 7768593
Filing Date: 2010-08-03
Classification: G02F

Abstract:
1. A surface emission device comprising: a plurality of light sources respectively shaped into a columnar form extending in a predetermined direction and disposed on the same plane as being extended in the same direction; an optical element having transparency and having, as formed therein, a luminance distribution generating layer suppressing variation, in a direction of optical axes, in luminance of light emitted from the plurality of light sources; and a reflective surface positioned as being opposed to the optical element across the plurality of light sources, while keeping an air layer between the optical element and itself, and reflecting light emitted from the light sources, wherein the luminance distribution generating layer of the optical element being composed of a plurality of structural portions extending in a longitudinal direction of the light sources and projecting in the direction of optical axes, the surface emission device characterized by: having the optical element containing the maximum tangential angle a which satisfies x>L/2−D/2 and configured such that a component in an arrangement direction of the structural portions as viewed in a sectional profile thereof at an outer surface section in the sectional profile of a structural portion having a tangential angle Ψ that is larger than or equal to a tangential angle b of 56° has a percentage of 10% to 30% with respect to a component in the arrangement direction of the structural portions as viewed in the sectional profile thereof at an outer surface in the sectional profile of a structural portion included in the luminance distribution generating layer, when travel range x of a split image of the light sources in the direction normal to the optical axes is calculated using conditional equation (1) to conditional equation (3) below: distance between centers of every adjacent light sources as L; refractive index of the optical element as n; thickness of the optical element as d; distance from the center of the light sources to the optical element in the direction of optical axes as W; refractive index of air in the air layer as n angle of incidence of light emitted from the light sources and coming into the optical element, relative to the direction of optical axes, as θ angle of refraction of light, incident on the optical element, in the optical element as θ diameter of each light source as D; angles formed between a tangential line in contact with an outer surface of the luminance distribution generating layer and a plane orthogonal to the optical axes, as viewed in the sectional profile orthogonal to the longitudinal direction of the structural portions of the luminance distribution generating layer, as tangential angles Ψ; a tangential angle largest of all tangential angles Ψ as a maximum tangential angle a; a tangential angle, out of all the tangential angles Ψ, under which the split image of the light source reaches L/2 as b; and L/W is 1.9 to 3.5.