Freeform lens for white LEDs with high angular color uniformity

Angular color uniformity (ACU) is essential for LED general lighting. We demonstrated a freeform lens to enhance the ACU of white light-emitting diodes (LEDs) whose phosphor layers were coated by freely dispersed coating processes. The design method of the freeform lens was introduced briefly. Accurate optical models of white LEDs were built. Monte Carlo ray tracing simulation results indicated that ACU of the modified LED integrated with the freeform lens significantly increased from 0.334 to 0.957 compared with the traditional LED. Enhancement of ACU reached as high as 186.5%. In addition, ACU of the modified LED was not only at a high level but also stable when the shape of the phosphor layer changed. The freeform lens provided an effective way to achieve white LEDs with high ACU and at low costs.