Ghost secondary light source for LED collimated illumination

Collimated illumination using a light-emitting diode (LED) is widely used in the residential, commercial, and optical inspection fields. A typical collimator, namely, one that is a parabolic reflector, has a focal point on which a light source should be placed. The light source approximates a point source, which enables light rays reflected by the reflector to form a collimated beam with a narrow light distribution angle. However, it is difficult to place an LED at the focal point of the reflector because a heat dissipator attached thermally to the LED prevents the reflected light rays from emitting out. A curved light guide that can generate a secondary light source at a focal point of the reflector without disturbing reflected light, like a ghost, is proposed here. A spotlight consisting of the curved light guide and a parabolic reflector is fabricated and shows that a collimated beam with a half-intensity angle of less than 4.3 deg can be realized with the reflector opening diameter of 90.0 mm.