Design of a coaxial light guide producing a wide-angle light distribution

A compact light-emitting diode (LED) lighting module with a coaxial light guide that can produce a wide-angle light distribution is proposed. The structure of the coaxial light guide has a scattering area inside it and a tapered outer surface that is able to concentrate all of the rays on the scattering area owing to the total internal reflection. The rays diffused and reflected by the scattering area are refracted by the tapered outer surface and emitted in a wide-angle light distribution. A prototype of the LED lighting module was able to produce a point-like compact light source that radiates rays with half-intensity angle of 274° and lighting efficiency of 91%.