Design of a freeform refractive surface with reflection loss for illumination

We have proposed a design method of a freeform refractive surface for illumination using multiple faceted refractors. The reflection loss on the refractive surface also has been considered during the design process. As an example, a smooth freeform lens with uniform illumination distribution is designed. Compared with the direct method without consideration of the loss of energy, the method achieved a great improvement in the uniformity of illumination distribution with no loss of output efficiency.