Flat light guide - A sustainable and creative light source

Abstract

Light has always been used as a means of communication. As early as in the 4^th century B.C. a hydraulic telegraph that was used in combination with fires has been developed by the Greeks. In 1821 Carl Friedrich Gauss invented heliotrope – an instrument that uses a mirror to reflect sunlight over great distances. Nowadays, light impulses travel on the principle of total reflection between materials of different density, inside round cross-section acrylic fibers—light guides—and are protected from inclement weather conditions and other disturbances from the surroundings. The result of such light "transportation" can be indirect – a transmission of data, or direct – a transmission of light with the purpose of illumination. Light that exits at the end of an optic fiber is usually formed as a point, as a line or, in our case, as a luminous surface. Light can also be intercepted on its way through a flat light guide, through a special surface treatment. Textures on the surface of sheets of acrylic glass form panels of either uniform or various brightness. Such panels can assume the role of the elements of an architectural luminous ambience. Transmission and reflectivity is also investigated, theoretical and practical, using light measurements on a physical model in order to show that luminous panels can also be used as floors/ceilings in multi-storey buildings in order to improve natural illumination and thus to reduce the cost of electrical lighting. Findings in the paper can bring useful information for architects, lighting designers and structural engineers.