Light output losses of prism light guides

Abstract

Cylindrical prismatic hollow light guides are able to transmit daylight properly into the spaces of a building in which natural light has a difficult access. Transmission through the guide depends on the optical characteristics of the material, the shape of the guide and the fidelity of the geometry in prisms structure. It is important to analyse the micro-structure prism imperfections of the surfaces such as the existence of a curved area on peaks prism which modify the behaviour of the prism film; these imperfections, change the optical path and therefore the rays are directed to other directions instead of undergoing total internal reflections. In this paper, several cylindrical guides made of transparent dielectric material characterized with an absorption factor have been developed. A numerical analysis has been carried out by software tools to analyse the flux distribution in the light guidance system comparing its efficiency by optical analysis in different simulations. These simulations include high reproductively prism related to the light pipe’s material and optical properties including a study of the impact of imperfect geometry which is necessary to allow rigorous comparisons with the experimental simulations. The simulated results have been compared with experimental data obtained through real scale analysis. The experimental measurements have revealed effectiveness of 66.7 % in the aspect ratio of 30.