Irradiance tailoring for extended sources using a point-source freeform design algorithms

The advent and rapid development of efficient high power LED sources with their unique emission characteristics enables the development of illumination systems that meet very strict requirements concerning light distribution and efficiency. Most of the algorithms used to design the necessary optical freeform surfaces rely on the point source assumption. As long as the distance between LED and those surfaces is sufficiently large, this is a good approximation. One further important design goal is to make the optical components as small as possible, which makes the point source assumption less accurate. The existing design algorithms thus have to be accompanied by methods to treat the finite-sized LED sources. We examine the limits that are set by the finite size of the light sources and present algorithms to optimize optical freeform surfaces up to these limits. Point source results are iteratively improved to get the desired illumination pattern employing finite sized LEDs. At each iteration step the illumination pattern used in the point source computations is adapted so that the real illumination pattern of an LED approximates the originally desired pattern.