The Design of Diffuse Reflective Free-Form Surface for Indirect Illumination With High Efficiency and Uniformity

Indirect illumination with light-emitting diodes (LEDs) and a diffuse reflector is widely applied in various fields that require uniform illumination, whereas the high uniformity obtained is always at the cost of sacrificing the light efficiency. Hence, in this paper, the energy conservation is implemented to greatly compensate for an inefficient design. A mathematical model of a free-form reflective surface based on the Lambertian characteristic of LED, ideal diffuse surface, and energy conservation is established. The diffuse free-form surface is constructed by solving a series of equations numerically. Furthermore, several array configurations are used to illustrate the advantages of the free-form surface. Finally, not only in the far-field simulation but in the near-field simulation as well, the results show better uniformity and higher efficiency compared with traditional design methods (direct illumination and diffuse illumination with a hemispherical inner surface).