The effect of textures of aspherical lenses on the performance of projection systems for automotive headlights

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The effect of textures of aspherical lenses on the performance of projection systems for automotive headlights

Schmidt, J. / Holtz, S.

The target of our research is to determine a correlation between different textures (frostings) on the surface of aspherical blank molded lenses and the photometric patterns of automotive projection systems. A common way to modify the photometric performance pi a projection headlight is the specific structuring of the aspherical lens surface by applying textures. The most cost efficient way to apply such textures is a transfer onto the aspherical surface during the molding process without any additional texturing step. Anyway, the choice of the texture is rather determined by the experience of the toolmakers that produce the mold than by analytical considerations. Our research will help manufacturers to choose and to specify unambiguously the right texture for their specific application and to save time by reducing iteration steps during the prototype phase. So the work will help to find the relations between theory and practice. The authors describe how they manufacture lenses with different types and grades of texture; adapt an appropriate method to determine glass surface roughness; describe the photometric performance of a projector system; determine the photometric properties of this system as a function of texture grade and type. This functional relationship will be the first step towards a mathematically well-founded fast and easy manipulation of photometric patterns of projection systems by selectively applying textures of different type, size and grade on the aspherical surface.