HOLLOW LIGHT GUIDES: 50 YEARS OF RESEARCH, DEVELOPMENT, MANUFACTURE AND APPLICATION - A RETROSPECTIVE AND LOOKING TO THE FUTURE

The paper provides a historical overview of key emergence and development stages of a new branch of lighting science and technology. The paper covers developments from mirror slit hollow light guides with reflective internal surfaces, through to prismatic light guides, and then to the creation of installations like "Heliobus" and "Arthelio", where natural sky and sunlight, as well as light from artificial sources enters and disperses within buildings. In recent years short hollow end-to-end light guides are widely applied for channelling natural light. The paper explores new prospects and directions for further development of hollow light guides, which offer efficient and effective avenues for improvement for lighting installations. Hollow light guides present an important opportunity to increase the safety and efficiency of lighting installations, giving them new aesthetic forms. The production of hollow light guides is a complex technological effort. It involves the development of new metric methodologies, alternative photometric devices, new optical systems, materials and light sources, as well as the creation of completely new efficient lighting installations. This developing branch of science accounts for over one hundred patents, several hundred peer reviewed articles, two books, eight PhD theses, and two CIE publications developed within Division 3.