Design of freeform optics for the realization of application adapted intensity distributions with small extents

Freeform optics have become a versatile tool for flexible illumination in various lighting applications including laser beam shaping for materials processing. For such non-imaging freeform optics, a broad range of design algorithms have been developed. However, when the target intensity distributions become very small, which is especially important for laser materials processing, the thickness and curvature of the designed freeform optics increase resulting in numerical instabilities during the design or in manufacturing challenges. Therefore, we present a design method based on a conventional mapping approach which is adapted to combine a comparatively flat freeform optic with a secondary standard focusing lens to create small intensity distributions. We present design examples for laser materials processing applications. In addition to obtaining a flat, easy-to-manufacture design with a high reliability, the approach also has the advantage that the intensity distribution size is scalable by variation of the focusing lens' focal length.