Patent ID: 8029167

Claim:
A light emitting device comprising: a point light source having a narrow distribution angle; a solid and transparent light guide having a circular, planar light receiving surface transverse to a light axis and receiving the light from the point light source, a reflecting side surface reflecting internally the light from the light receiving surface, and a light radiating surface radiating the light reflected on the reflecting side surface; a recess arranged at a center of the light receiving surface and facing the point light source; and a concave lens formed by a surface of the recess, wherein the reflecting side surface is a revolving surface determined by revolving a parabola around a center axis fitting to the light axis of the point light source, the parabola is a segment of a parabola passing through one point of peripheral border of the light receiving surface, and the other point of peripheral border of the light radiating surface; and having a focal point on the other point of peripheral border of the light receiving surface, obtained by assuming a plane containing the center axis and cutting off the light guide; two points of peripheral border of the light receiving surface; two point of peripheral border of the light radiating surface; and a coordinate system parallel to a straight line passing through one point of peripheral border of the light receiving surface and one point of peripheral border of the light radiating surface, and having a horizontal axis passing through the other point of peripheral border of the light receiving surface, the point light source is arranged apart from the light receiving surface and outside the light guide so as to divide the light from the point light source into light entering into the light guide through the surface of the recess and light entering into the light guide through some part of the light receiving surface other than the recess.