用于扩展光源均匀照明的自由曲面反馈设计

A Feedback Design Method of Freeform Reflector for Uniform Illumination with Extended Sources

为克服点光源近似条件下设计得到的自由曲面应用于扩展光源系统时均匀度降低的缺点,基于偏微分方程法提出了一种反馈优化算法.建立了扩展光源辐射模型,在点光源近似条件下求解偏微分方程数值解得到初始曲面结构;讨论了光线传输方向经过轴线时该初始结构在应用于扩展光源均匀照明系统时的不足.提出以初始仿真结果中目标面上的照度分布作为反馈,通过重构目标面划分来实现曲面二次优化设计的方法,并利用TracePro进行了光线追迹仿真实验.模拟计算了500万条光线、直径3cm的扩展光源在距离30m、直径10m的照明区域内的照度分布,发现优化前后目标面上照度均匀度从60%提高到90%以上,证明了该反馈算法能够有效提高目标面上照度均匀性,对提高实际光学系统的照明效果具有一定的指导意义.

To overcome the disadvantage of the system uniformity reduction when a freeform surface constructed on the point source assumption is applied to the extended sources systems,a new feedback optimization algorithm based on the partial differential equation was proposed.Based on the point approximation,the initial surface structure were obtained through the numerical solution of the partial differential equation under the establishment of the radiation model of the extended light source.Then the shortcoming of the initial surface structure was analyzed when used for uniform illumination with extended sources under the circumstance that the rays transmission direction and the optical axis intersect.Therefore the proposed algorithm re-optimized the reflector to improve the uniformity by renewing the distribution of the target region,with the illuminance distribution in last simulation experiment as feedback.To illustrate the effectiveness of the proposed method,simulation experiments were carried out with TracePro.An extended light source with the size of 3cm in diameter was used in experiments,in which total five million rays were computed.The light tracing experiments show that the uniformity of the object region increases from 60% to more than 90%,which demonstrates that the feedback design method can improve the illumination uniformity of the target surface effectively and provide some theoretical guidance for the improvement of the realistic lighting systems.