提出了基于能量映射关系和易加工性约束的照度偏离量累加反馈优化算法, 并设计了一款可实现照度均匀分布的基于板上芯片(COB)型发光二极管(LED)光源的自由曲面透镜。本算法将每次迭代反馈优化后的仿真光分布与目标光分布的照度偏离量, 累加到预设目标光分布进行修正, 并利用修正后的目标光分布结合能量映射关系重构自由曲面透镜模型; 同时, 从易加工性的角度提出在反馈优化过程中将透镜外曲面下半部分约束为竖直面。以Cree CXA1816 COB LED为光源设计了相应的自由曲面透镜, 结果表明, 经过3次反馈优化后即可在距离光源1000 mm、半径为1480 mm的圆形区域实现均匀照度分布。根据设计结果加工了相应的透镜并进行照明效果的测试, 实测的照度分布与仿真结果比较吻合。

A cumulative feedback optimization algorithm based on illumination deviation restrained by energy mapping relationship and easy processability is proposed, and a freeform surface lens with uniform illumination distribution and light emitting diode (LED) of chip on board (COB) as light source is designed. In this approach, the new target light distribution is modified by accumulating the illumination deviation after each iterative feedback optimization between the simulation light distribution and the target light distribution to the presupposed target light distribution. The target light distribution after modification is then used to reconstruct the model of the freeform lens by combining the energy mapping relationship. Meanwhile, to make the designed lens easier to be molded and processed, the structure of the lens is modified by restraining concave plane of the lower half of lens into vertical plane in the feedback optimization progress. With this method, the corresponding freeform lens is designed with Cree CXA1816 COB LED as light source. The results show that the uniform illumination distribution in a circular region with a distance of 1000 mm from light source and a radius of 1480 mm can be achieved after 3 times feedback optimization. Finally, according to the design results, the corresponding lens is fabricated, and the illumination effect is tested. Actual measured illumination of the lens is consistent with the simulation results.