Determination of Beam Pattern Movement for Engineering Thermoplastic Complex Reflectors 950830

Complex reflectors -- also known as faceted or optics-in reflectors -- are becoming a popular forward lighting option on passenger vehicles. When optics are located in the reflector, changes in the shape of the reflector due to thermal expansion, stress relaxation, and creep become more critical than with conventional lenses because changes in reflector shape shift the optics, causing beam patterns to move.
To assess such movement, complex reflectors molded of injection molded thermoplastics were photometered using an LMT GO1200 gonio-photometer. Isocandela plots were generated at several points in time, and amount of beam pattern movement and pattern brightness changes were calculated.
While the results of the study showed that the complex reflectors molded of engineering thermoplastic experienced more beam pattern shift than would be seen with a BMC reflector, a combination of proper material selection and optics design can overcome this movement. This paper will discuss the testing that was performed, and how these test results can be used to assist in the design of thermoplastic complex reflectors. Use of engineering thermoplastics gives the advantages of recyclability, weight reduction, and the possibility of lowering total system cost for standard and complex reflectors.


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