Ultrathin free-form micro-optical elements for direct-lit applications with a large distance-height ratio

In this study, we present a smart design concept for extremely thin free-form (FF) micro-optical elements (MOEs) for uniform illumination in direct-lit LED luminaire systems with a large distance to height ratio (DHR). A design example for a FF-MOE with a height of only 50 µm that allows for a DHR value of more than 3 is presented. In particular, it is also shown that the arrangement of the FF-MOE with respect to the substrate (bottom side or top side) is of essential relevance in order to achieve large DHR values. The applicability of these FF-MOEs is demonstrated by comparing the simulation and experimental results of a demonstrator box mimicking a thin direct-lit luminaire.