Tailored freeform surfaces for illumination with extended sources

Julius Muschaweck

doi:10.1117/12.2632439

3 October 2022 Tailored freeform surfaces for illumination with extended sources

Julius Muschaweck

Proceedings Volume 12220, Nonimaging Optics: Efficient Design for Illumination and Solar Concentration XVIII; 1222004 (2022) https://doi.org/10.1117/12.2632439
Event: SPIE Optical Engineering + Applications, 2022, San Diego, California, United States

Abstract

Tailoring freeform surfaces for illumination with point sources is an established method to generate near-arbitrary illuminance distributions with high detail using a single freeform surface. Real, non-laser sources are not point sources, however. Replacing a point source in a tailored freeform system with an extended source blurs the point-source distribution. Accordingly, extended sources are often treated as a perturbation within a pointsource tailoring algorithm, which may work well for small sources. However, important applications like street lighting, wall-washing and automotive front lighting require some peak intensity in certain directions, which can only be achieved with a given source luminance when nearly the whole aperture contributes to that peak intensity. Then, the tenet of point source tailoring – a one-to-one relation of surface points to target points – breaks down. In this paper, we embrace extended sources instead of treating them as a perturbation: Illuminance at several target points is computed by integrating the luminance of the virtual source image over its finite projected solid angle in a noise-free, non-Monte-Carlo way. The freeform surface is parametrized; the shape of the distorted virtual source image, and thus the illuminance at the target points, becomes a function of the freeform surface parameters, leading to a system of nonlinear equations, which we solve iteratively. Using a solved-example problem, we also give first answers to whether solutions exist and are unique.

Conference Presentation

Citation Download Citation

Julius Muschaweck "Tailored freeform surfaces for illumination with extended sources", Proc. SPIE 12220, Nonimaging Optics: Efficient Design for Illumination and Solar Concentration XVIII, 1222004 (3 October 2022); https://doi.org/10.1117/12.2632439

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