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Reliability of point source approximations in compact LED lens designs

Dept. of Physics and Nanotechnology, Aalborg University, Skjernvej 4A, DK-9220 Aalborg, Denmark.
Optics Express (Impact Factor: 3.49). 11/2011; 19 Suppl 6(23):A1190-5. DOI: 10.1364/OE.19.0A1190
Source: PubMed

ABSTRACT In many applications, compact concentrator lenses are used for collimating light from LEDs into high output beams. When optimizing lens designs, the LED is often approximated as a point source. At small lens-to-LED size ratios this is known to be inaccurate, but the performance compared to optimizations with more realistic models is rarely addressed. This paper examines the reliability of a point source model in compact lens design by comparing with optimisations that use a factory measured LED ray-file. The point source is shown to cause significant, unnecessary efficiency loss even at large lens sizes, while the use of a ray-file allows for a >55% reduction in the footprint area of the lens. The use of point source approximations in compact lens designs is therefore generally discouraged.

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