Studies on light extraction design of white LEDs with high luminous efficiency and uniformity

摘要

In this paper a new planar optical system with patterned phosphor-layer structures is demonstrated. The phosphor film herein acts as a wavelength converter and a light diffuser simultaneously. The patterned structures can increase the depth of blue ray intrude into phosphor film. The absorption rate of blue ray and the utilization efficiency of phosphors are increased. So the luminous efficiency is improved. Given different patterns on the phosphor layer surface, the optical properties of the proposed optical system, light-emitting efficiency and uniformity, are studied. Eventually, an average irradiance of 58.372 W/m~2 and a more appropriate color temperature of the lighting source for high quality optical system were achieved. Phosphor layer of flat and part-etched pattern were compared in irradiance. The result validates part-etched phosphor-layer produce 2.57% higher average irradiance than flat phosphor-layer. The patterned area on phosphor-layer can increase the extraction efficiency of blue rays at periphery part, the uniformity of correlated color temperature (CCT) at periphery area is significantly improved, the light candela distribution of output light are adjusted by the patterns, so the illumination uniformity of planar optical system is adjusted. Finally, the yellow circle phenomenon of planar optical system is effectively improved by the given patterns. Then it will be utilized in high quality planar optical system.