Design of secondary light source for reflectors with axisymmetric light guide

A reflector lamp is a type of electric lamp that is widely used in commercial, residential, and transportation illumination. A typical reflector surface, namely, one that is paraboloid, has a focus on which a light source of the reflector lamp should be placed. The light source approximates a point source, which enables light rays reflected by the reflector to form a parallel beam with a narrow light distribution angle. However, it is difficult to place a light-emitting diode (LED) at the focal point of the reflector because a heat dissipater attached thermally to the LED prevents the reflected light rays from emitting out. Thus, an axisymmetric light guide to produce a secondary light source that can be placed on a focus of a reflector is proposed here. The lighting efficiency of the light guide is about 83% with wide-angle distribution toward the reflector. A spotlight consisting of the light guide and a parabolic reflector is fabricated and shows that a parallel beam with a half-intensity angle of 9.0 deg can be realized with the reflector opening diameter of 69.0 mm using a secondary light source produced by the axisymmetric light guide.