Reliability of point source approximations in compact LED lens designs.

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.