大视场大相对孔径自由曲面成像系统设计

Design of the freeform imaging system with large field of view and large relative aperture

近年来,自由曲面在高性能离轴反射成像系统中应用越来越广泛。文中基于矢量像差理论和遗传算法求解初始结构,采用视场离轴和孔径离轴相结合的方式,利用XY多项式描述的自由曲面增大自由度校正离轴像差,设计了一个大视场大相对孔径的制冷型离轴反射光学系统。系统工作波段为长波红外8~12μm,焦距400 mm,F数为2,视场角为8°×5°,平均RMS波像差为0.037054λ(λ=9μm)。探测器冷光阑和光学系统出瞳相匹配,实现100%冷光阑效率,系统能量集中度较高,成像质量良好。

In recent years,freeform surfaces have been used increasingly in off-axis reflective imaging systems with high performance levels.In this paper,the cooled off-axis reflection optical system with both a large FOV(field-of-view)and a large relative aperture was designed based on the initial structure from vector aberration theory and genetic algorithm,by using a biased input field and an offset aperture stop,utilizing freeform surfaces described by XY polynomials to increase degrees of freedom to correct off-axis aberrations.The working band of the system was LWIR(long wavelength infrared)8-12μm,the focal length was 400 mm,the F-number was 2,the8°×5°,and the average root mean square(RMS)wavefront error of the system was 0.037054λ(λ=9μm).The detector’s cold stop matches the exit pupil of the optical system which ensure a 100%efficiency of the cold diaphragm.The system has a high energy concentration and a good image quality.