Earlier lamp concepts using light guides are mostly characterized by placing the light pipe in a plain surface, normal or close to normal to the out-coupling direction. Lighting engineers have used quasi static out-coupling 42inch-prism structures, according to the angle of TIR (Total Internal Reflection) within a transparent material having a refractive index of 1,5. As modern design continues to determine further challenging shapes for automotive signal lights, light guides have to follow their geometry e.g. the oval contours of a tail-lamp lens. Being the proper solution for other applications, the 42inch-prism concept can be applied to a structure bent along an oval car body with just a limited success. To solve this problem by keeping the light guide structure simple and the number of LEDs down, to reducing costs, in parallel with fulfilling legal requirements, a novel approach is described in the paper. Applying a novel functional controlled shaping in light guide out-coupling structures and weighted luminous flux, luminous intensity and luminance based criterions within a complex merit function has made possible achieving luminance distribution homogeneity within the range of 1:2, simultaneously to complying with standard ECE, SAE and further customer requirements. The basic idea behind, is to modify simultaneously and continuously side angles, prism heights and even edge radiuses by controlling them along the light guide according to certain mathematical functions. Those functions can be established using a small number of parameters, which reduces the size of the optimization task significantly, in comparison to controlling each individual prism by its own parameter set. Having a light guide length in the range of e.g. 50mm up to more than 400mm the number of control parameters for optimizing the structure geometry remains the same and reduces significantly the amount of iterations required for finding an optimal solution.
Improved light guide design for automotive signal lamps
Verbesserte Lichtleitergestaltung für Fahrzeugsignalleuchten
2005
11 Seiten, 5 Bilder, 4 Quellen
Aufsatz (Konferenz)
Englisch
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