给出了基于CO2激光器（中心波长λ1=9.3 μm 和λ2=10.6 μm）的连续可变扩束比激光扩束系统的设计实例。系统镜片全部采用硫系玻璃材料Ge20Sb15Se65，此材料便于模压以降低成本。以经典二组元变焦设计为出发点，在理想光学系统的基本目标参数上加入具体的波长、入射直径和材料等光学参数，利用Zemax软件优化校正像差，设计得到了一种光束准直性好、结构简单且成本低廉的CO2激光器连续可变高扩束比激光扩束系统。此系统最大入射光束直径为6 mm，两中心波长带宽均设计为100 nm，扩束比在2~7之间连续可调，最大波像差小于1/4中心波长。

In this paper, a CO2 laser (λ1=9.3 μm and λ2=10.6 μm) beam expanding system with high variable expanding ratio is presented. The system lens is designed as a combination of four singlet lenses fabricated with chalcogenide glass material Ge20Sb15Se65, the advantage of the superior property of chalcogenide glasses is molding preparation of surfaces. The laser beam expander is designed as start point of two component zoom design idea, with the specific wavelength, incident diameter, material and other optical parameters on the basic parameters of the ideal target optical system. By using Zemax optical design software, the optical structural parameters of the system are optimized. This optical design of CO2 laser beam expanding system with high variable expanding ratio is good beam collimation, simple structure and also has low cost. The results show that this optical system has a maximum diameter of the incident beam is 6 mm, the bandwidth is 100 nm, variable beam expanding ratio is between 2 to 7 and the maximum wavefront aberration is less than 1/4 of central wavelength. Thus, it can be applied in all kinds of opto-electrical fields.