Patent ID: 8118457
Filing Date: 2012-02-21
Classification: F21V,F21Y,G02B,H01L

Abstract:
1. An illuminating device comprising a light source and an optical element including a light receiving surface faced to a light emitting surface of the light source, a first light exit surface located opposite to the end of the optical element from the light receiving surface and a second light exit surface connecting the light receiving surface and the first light exit surface, wherein when the center of the light emitting surface is designated as a first point, a point at the edge of the light emitting surface is designated as a second point and an axis which passes through the first point and is perpendicular to the light emitting surface is designated as an optical axis, the first light exit surface of the optical element has a hollow around the optical axis with respect to the edge and in a cross section of the optical element including the optical axis and the second point, when a point on the first exit surface at which angle of view from the first point with respect to the optical axis is 15 degrees is designated as a third point, an intersection of a ray which has been emitted at the second point and travels in parallel to the optical axis and the first light exit surface is designated as a fourth point, the first point is designated as the origin and an axis connecting the first point and the second point is designated as x axis, the first light exit surface is formed in such a way that x coordinate of a point which is the most distant from the optical axis on the first light exit surface is 1.5 times or more than x coordinate of the second point, that in 80% or more of an area in which x coordinate of a point is equal to or greater than x coordinate of the third point, an angle of incidence of light emitted at the first point is equal to or greater than the critical angle and that in 80% or more of an area in which x coordinate of a point is equal to or smaller than x coordinate of the fourth point, an angle of incidence of light emitted at the second point is smaller than the critical angle.