| 摘要 |
An illuminating device includes a light source (101) and an optical element including a light receiving surface (203), first and second light exit surfaces (205, 207). When the center of a light emitting surface (201) is designated as P1, a point at the edge of the light emitting surface is designated as P2 and an axis which passes through P1 and is perpendicular to the light emitting surface is designated as an optical axis, the optical element has a hollow around the optical axis with respect to the edge. In a cross section of the optical element, when a point on the first exit surface at which angle of view from P1 with respect to the optical axis is 15 degrees is designated as P3, an intersection of a ray which has been emitted at P2 and travels in parallel to the optical axis and the first light exit surface is designated as P4, and an axis connecting P1 and P2 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 P2, that in 80% or more of an area in which x coordinate of a point is equal to or greater than x coordinate of P3, an angle of incidence of light emitted at P1 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 P4, an angle of incidence of light emitted at P2 is smaller than the critical angle.
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