Design of maskless micro-optical automotive low-beam

Recently the first automotive vehicles with micro-optical headlights entered the market as series production models. Besides aesthetics, multi aperture micro-optics bring the advantage of a reduced axial length of the system due to the much shorter focal length of each channel. However, the currently implemented low-beam systems suffer from low transmission and notable cost for the micro-optics elements. Both problems can be traced back to the buried micro-slides within the micro lens arrays, (MLA) which shape the distribution. To overcome these issues, we developed a micro-optical solution for a low-beam without mask layers, thereby significantly increasing transmission to a very competitive level and enabling more cost-effective manufacturing processes. Our design follows the general principle of a fly's eye condenser (FEC) but comprises of a multitude of differently shaped lenslets, which form the beam collectively. The design process includes the generation of the overall distribution as well as detailed features such as the sharp and specially shaped cut-off and a smooth distribution within the beam. Particular effort is necessary to control stray light which is caused by imperfect manufacturing of the MLAs. A first LED-illuminated demonstrator showed that the shape and the required sharpness of the cut-off can be achieved even without the use of absorbing masks with a single optical module. Stray light control and fine tuning of the distribution makes it possible to manufacture a maskless polymer-on-glass micro-optical component and generate a beam pattern in accordance with UNECE safety regulations.