Realization of uniform and collimated light distribution in a single freeform-Fresnel double surface LED lens.

In this work, a design method of a freeform-Fresnel composite surface lens is proposed, which can be applied on LED lighting optics to realize uniform and collimated light output in a single lens element. The lower lens surface is of freeform type, which transforms the light distribution from the LED sources to a uniform one, and the upper lens surface is of the Fresnel type, which further transforms the lights to a collimated beam. Through the optimization of lens parameters, the obtained lens has the advantages of compact volume, wide acceptance angle, high light extraction efficiency, and high design accuracy.