Iterative freeform lens design for extended light source

Freeform lens design for LED beam shaping is a difficult inverse problem which generally doesn't have a unique solution. Under point source approximation, we have proposed an iterative wavefront tailoring (IWT) method [Opt. Lett. 44, 2274-2277 (2019)] for manipulating the irradiance distribution on a planar or curved target. This method has the ability to generate a variety of freeform lens structures including plano-freeform, spherical freeform and double freeform lenses with high accuracy. However, such a point-source design method becomes less valid for a compact design where the LED size is no longer negligible. We integrate the IWT method with an adaptive over compensation to reduce the irradiance deformations caused by the extended LED source. The IWT designs are iteratively modified to approach the prescribed irradiance distributions with the help of an over compensation coefficients. The new composite method combines the advantages of both the IWT method and the over compensation method.