The secondary optical lens of the light-emitting diode (LED) constructed with freeform surface plays more and more important role in common illumination. The reflective loss at the freeform interfaces is discussed in this work. To restrict the reflective loss of the rays with the large incident angle, the freeform surface design rule is proposed. In this rule, the maximum deflexion angle of the refractive surface is 25° for a single freeform interface when choose PMMA to be the lens material, and the total reflection surface is introduced to control the rays which cannot be dealt by the refractive surfaces. The lens examples based on this rule are constructed by multi-segment freeform surfaces and the results show that the reflective loss is controlled less than 10%.

Date Published: 5 November 2010
PDF: 6 pages
Proc. SPIE 7849, Optical Design and Testing IV, 784910 (5 November 2010); doi: 10.1117/12.869487

Published in SPIE Proceedings Vol. 7849:
Optical Design and Testing IV
Yongtian Wang; Julie Bentley; Chunlei Du; Kimio Tatsuno; Hendrik P. Urbach, Editor(s)