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Scattering Phenomena in Thick Molded OpticsBrant Potter, Larry Boxler Valeo Lighting Systems North America, LLC Seymour, IN, US
Abstract
Automotive styling, safety, and efficiency requirements are driving the development of new lighting technologies. Recent advances in plastic injection molding now allow for very complex and large (‘massive’) optical lens elements to be made. Thick molded optics, coupled with high flux LED light sources, can provide high performance automotive lighting including low beam and ADB. These optical designs provide high styling aspect, high optical efficiency, and weight reduction, but also present new challenges to the optical design in terms of light scatter.
For functions were parasitic light is critical such as low beam, the consideration of different light scatter phenomena from thick molded optics is critical to ensure customer and legal limits are met. Scatter phenomena must be considered during part design, simulation, and tolerancing studies. Surface scatter can occur due to periodic micro-structures created from the machining process (a diffractive effect). Light deviation can occur due to local surface slope errors caused by part processing. This becomes more problematic as part size and complexity increases. Volume scattering within the plastic occurs at small levels, and can become significant for high flux densities over long optical path lengths.
This paper explores the different scatter phenomena associated with thick molded lens parts and their effect on the overall beam pattern. A correlation study of simulation versus measured part is presented. Results show that using appropriate scatter models greatly improves correlation, and is critical for creating a robust design.
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