Free-form glass reflectors for non-trivial illumination applications with extended sources

The field of illumination optics has an increasing demand for free-form optics that produce arbitrary light distributions. In various applications an asymmetric, e.g. rectangular illumination can be beneficial, such as street lights, shop lights or architectural lighting. Yet there are only very few construction methods for free-form surfaces, especially using extended sources. One such method utilizes a manifold of conic sections to derive a source-target mapping for a particular source and target distribution. Although it relies on the assumption of a point source it can be adapted to work with real, extended sources. We implemented the algorithm to construct glass reflectors for almost arbitrary light distributions, either prescribed in the near- or far-field. Starting with a point source, an initial surface is optimized in a second process with a feedback loop to produce the desired result with the actual extended source. Our method is quite robust and was used to design for example an asymmetrical street light reflector. It was manufactured at Auer Lighting GmbH out of borosilicate glass. Measured target distributions are in excellent agreement with the simulations. These promising results show that this particular design method can be applied to real world applications. It is a powerful tool whenever a highly optimized reflector for a non-trivial illumination is required.