为了满足在某些照明场合下随时改变光束视场角以及能量密度分布的实际需要，提出一种可变视场角LED照明光学系统的设计方法。针对传统可变视角照明光学系统的不足，在全反射式透镜结构的基础上，依据出射光束准直设计透射面，依据远场目标面照度均匀的特定光强分布形式设计全反射面。当LED的位置在规定范围内连续变化时，出射光束的视场角以及能量密度分布亦随之变化。设计了一种视场角变化范围为8°~20°的新型全反射式透镜，模拟结果表明，相比于传统结构，系统的平均光能利用率提高约13%，目标面辐照度平均均匀度提高约17%，体积约减小为传统结构的1/5。

In order to satisfy the practical requirements that the view angle and the energy density distribution of the light beam should be adjustable in some specific lighting applications, an effective method to design LED illumination system with adjustable view angle is proposed. Considering the shortage of the traditional structure, a novel total internal reflection (TIR) lens is designed. The refractive surface is designed according to that the output light rays are parallel to the light axis. The TIR surface is designed according to that the total output light rays can realize the uniform illuminance on the remote target plane. A polycarb (PC) TIR lens with the view angle from 8° to 20° is designed as an example with this method. The simulation results show that, compared with the traditional structure, the average optical efficiency is increased by 13% and the average irradiance uniformity is increased by 17%. The volume of the novel TIR lens is decreased to about 1/5 of that of the traditional structure.