SAE 2016-01-1407 : 2016

Retroreflective (RR) optical elements play a critical role in signaling, safety, and aesthetic/styling functionality of automotive lighting. The commonly-used inverted corner cube (ICC) RR structures with hexagonal aperture have several critical limitations that are primarily rooted in their manufacturing technique that involves complex assemblies/shapes of hexagonal pins and electroforms, particularly in case of freeform surfaces. This study introduces a novel RR micro-optical structure, namely: right triangular prism (RTP). The geometric model underlying this new geometry is defined as the intersection between a cube and a plane placed in a particular relative orientation with respect to each other. Following this, non-sequential optical simulation studies were performed analyzing the effect of incident light orientation. Advanced optical functionality of the RTP with a width of 450 μm was obtained as practically unattainable through conventional hexagonal pin-bundling technology. The study also shows that the use of RTPs can overcome the design/optical performance limitations associated with traditional ICC RR designs. Furthermore, the newly-developed single point inverted cutting technology was introduced as a feasible mean to fabricate functional optical prototypes and/or tooling inserts. In this regard, samples of functional RR areas were produced on flat PMMA plates and their preliminary validation has confirmed a 57% increase in the optical performance of the RTP compared with conventional ICC RRs. This supports the feasibility and/or potential of RTP as a new RR option for automotive lighting.

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