针对LED单自由曲面透镜近场大角度照明均匀性不足和出光效率低等问题, 基于边缘光线理论和网格划分法, 设计了内曲面为椭圆型, 外曲面为自由曲面的LED双自由曲面大角度透镜.透镜内曲面对LED入射光线进行发散, 外曲面对出射光线方向进行控制, 实现大角度均匀照明, 并减少全反射损失, 提高出光效率.采用扩展光源文件对透镜模型进行光学仿真, 并利用反馈优化法对外曲面进行优化, 提高近场的照度均匀性.研究表明: 在相同近场距离条件下, 出光角度为143°、151.8°时, 单自由曲面透镜照度均匀性为0.55和0.40, 出光效率为92.0%和80%, 而所设计的双自由曲面透镜照度均匀性为0.84和0.85, 出光效率为98.8%和95.0%, 照明效果明显改善.

Aim at the lacks of uniformity for large view angle illumination in the near-field and low efficiency of single freeform-surface lens of LED, based on the edge-ray theory and grid partition method, a double freeform-lens with large view angle of LED was designed, the inner surface was elliptic and the outer surface was freeform. The incident rays of LED diverge from the inner surface of the lens, and the direction of the emergent rays were controlled by the outer surface, which realized large view angle uniform illumination and reduces losses of total reflection, thus, improving the luminous efficiency. The extended source ray-file was employed to do optical simulation for the lens model, the feedback optimization method was used to optimize the outer surface and improve uniformity of near-field illumination. The results show that under the condition of same near-field distance, with the beam angles at 143°and 151.8°, respectively, the corresponding illumination uniformity values of single freeform-surface lens are 0.55 and 0.40, and the efficiency values are 92.0% and 80%.While the proposed double freeform-surface lens greatly improve illumination effects, with 0.84 and 0.85 illumination uniformity and 98.8% and 95.0% efficiency.