Angular color uniformity enhancement of phosphor converted white LEDs integrated with compact modified freeform TIR components

Abstract

Total Internal Reflection (TIR) lenses are optical components which are used to collimate the light. Desired uniform illumination within a limited beam angle is easy to be achieved by integrating LEDs with TIR lenses. However, most TIR designs do not pay attention to the color uniformity, an increasing important issue for the quality of lighting, and have a considerable dimension, which also limits their applications. In this study, a compact phosphor converted white LED module integrated with a modified freeform TIR component was presented and optimized to achieve compact size and high angular color uniformity (ACU). Optimal results of modified TIR components indicated that modified LED packages could achieve a smaller size in vertical height (~0.52) within the same horizontal radius, compared with LEDs integrated with classic TIR lenses. Meanwhile, the enhancement of ACU with an optimum appropriate divergence half angle (65 degrees) reached as high as 84% in terms of normalized standard deviation (NSD) of yellow-blue ratio (YBR), from 0.888 to 0.429. Phosphor converted white LEDs integrated with this modified TIR components can provide high quality lighting within a compact optical system.