Prismatic film light guides: Performance and recent developments

Abstract

Prism light guides are hollow structures which pipe light by means of total internal reflection (TIR). These devices are unique in their ability to combine the efficiency of TIR with the relatively low cost of a hollow structure. An important application stems from their ability to transform a point source of light such as an incandescent or discharge lamp into a linear or area source of light or illumination. This paper reviews the theory, advantages, and application of prism light guides based on the newly-developed 3M “optical lighting film”, an economical, flexible prismatic film for fabricating the light guide wall. We also report the results of measurements of the film's optical performance and properties. Results include the total reflectance at various incident angles, transmission, angular distribution of reflected energy and light pipe efficiency. Some current applications of “TIR film” (TIRF, trade name Scotch™ optical lighting film, SOLF) are described in the final section.