Planar Optical Light Guides for Light Collection and Collimation
Planar optical light guides are making a rapid entry into many light management and energy applications. With the advent of low-cost optical materials and microreplication technologies, edge-lit light guides became commonplace in smartphones, computers and TVs displays and are now being tried for general lighting and solar energy.
In edge-lit LED illumination devices and LCD displays, the angular distribution of the light beam light emitted by a light guiding panel (LGP) is defined by the technology used to extract light from the light guiding panel (LGP). The conventional features such as microgrooves or white paint dots distributed over the surface area can provide good brightness uniformity but lack the ability to form a directional light beam. Achieving high collimation and custom angular patterns is particularly challenging.
In solar energy applications, lightguides can condense sunlight to a high degree similarly to concentrating mirrors or lenses while also providing the benefit of a thin form factor. For example, the direct sunlight can be collected by a large surface area of the LGP and focused onto to its edge where it can be converted into electricity by a small solar cell or into heat by a thermal absorber. However, such devices require solving the problems of efficiently injecting light into LGP and delivering the injected light to a prescribed location.