The air-gap RXI lens efficiently produces a very narrow beam from high-powered LEDs. This design has an aspect ratio of 5, with both front surface and reflecting back surface designed simultaneously from periphery inwards, as profiles of circular symmetry, via applying the edge-ray principle to the chip geometry. The light source is a Lambertian-glowing cube 1.2 mm square and 0.15 mm high, as viewed through its clear (n=1.54) package dome, with emission down to 95° from the symmetry axis. A given exit-aperture diameter defines a minimum, etendue-limited collimation angle, α=arcsin(chip-width/diameter). At the center of the back surface is a tailored quasi-hemispheric cavity surrounding the source and serving to uniformly distribute the source flux over the front surface. The front surface reflects that source flux to the back surface, which reflects it back forward again, accomplishing the optical folding thereby. The back surface is shaped so that the light it reflects forward will be refracted out the front surface to become the collimated output beam.

Date Published: 8 January 2004
PDF: 12 pages
Proc. SPIE 5185, Nonimaging Optics: Maximum Efficiency Light Transfer VII, (8 January 2004); doi: 10.1117/12.507641

Published in SPIE Proceedings Vol. 5185:
Nonimaging Optics: Maximum Efficiency Light Transfer VII
Roland Winston, Editor(s)