High efficiency 90° elbow for light guides

Abstract

Transmission of light through a 90 degrees elbow in a hollow light guide is an important step in the development of natural lighting applications. In this paper we present a new design that has more than 260% higher efficiency in flux transfer than a standard bending system for hollow and aluminum light guides. The clue of this new system is to minimize the light angle at the output of the elbow, in such way that it is possible to guide light at higher distances because of the fewer reflections in the light guide. The system works properly for prismatic light guides but is also suitable for aluminum guides where the reduction of reflections permit the use of cheaper aluminum or the increase in length maintaining flux transfer. Also this reduction of reflections in aluminum light guide derives in less change of chromatic coordinates.