Effective freeform TIR lens designed for LEDs with high angular color uniformity.

Most LED luminaires face the problem of color nonuniformity in illumination fields, which seriously degrades their lighting quality. To address this issue, we proposed a freeform TIR lens, which could be applied to the most widely adopted phosphor-converted LEDs and multicolor LED arrays. Based on light pattern overlap and energy mapping, the novel TIR lens comprised the freeform panel and the collimator. Analysis of angular color uniformity (ACU), based on a phosphor-converted white LED model, proved that the normalized standard deviation (NSD) of the LED integrated with the freeform TIR lens significantly decreased from 0.792 to 0.232, compared with the NSD of the traditional TIR lens. Moreover, the proposed TIR lens was also applied to a multiple LED array for color mixing. Both the theoretical analysis and simulation results demonstrated their capability to enhance the ACU. These results demonstrated the effectiveness of the proposed method to improve the uniformity of the LED sources regardless of single or multiple LEDs. The improved lighting quality guarantees good employment of LEDs, especially in the fields of entertainment and architectural lighting.