Free-form illumination of a refractive surface using multiple-faceted refractors

We report a design method based on multiple-faceted refractors for free-form illumination of a refractive surface. The free-form surface is constructed as a set of primitive surface elements, which provide flexibility to satisfy the requirements of practical design problems. An extended light source can be considered, and a smooth free-form refractive surface can be established by adding feedback to the design process for a point source. Moreover, the performance can be improved by iterating this feedback process. Illumination systems with a point source and an extended source are designed and analyzed, resulting in uniform illuminance distribution, which demonstrates the validity of the method.