大相对口径长焦距折射式光学系统设计

Design of refractive optical system with large relative aperture and long focal length

分析了大相对孔径、长焦距折射式光学系统的像差特点，针对一款口径300 mm，焦距540 mm ，波段范围500~850 nm ，视场角2°的折射式成像物镜进行了设计。首先根据系统的像差特点，针对二级光谱，选择了Petzval型作为初始结构，并进行了复杂化，形成大空气间隔的三组元形式，利于像差的校正和后组元件尺寸的减小；而后针对使用波段对玻璃材料的部分色散P和阿贝数V值进行了修正，并绘制了P-V图，从中选择了具有一定二级光谱校正能力并性能优良的玻璃材料。最终系统的二级光谱达到了0.06 mm ，表明具有较好的复消色差性能。设计结果系统在相机Nyquist频率（39 lp/mm ）处各视场MTF大于0.8，80%能量集中在直径为8μm的圆内，小于一个象元尺寸，最大畸变小于0.1%，各项指标均满足设计要求。

The aberration characteristics of refractive optical system with large relative aperture and long focal length were analyzed. And a lens with 300 mm diameter, 540 mm focal length, 500-850 nm operating wavelength range, and 2° field of view was designed. First, as the secondary spectrum was the most prominent aberration, the Petzval form was chose as the initial configuration, and after complication, the configuration with three components with large air space was used, which was good for aberration correction and element size reduction. Then the partial dispersion and abbe number of typical glasses were recalculated and modified for the used wavelength, and P-V map is draw, then the glasses with some secondary spectrum correction ability and fine optical performance were chose. Finally the secondary spectrum of the system is reduced to 0.06 mm, which show that the system is apochromat. The design results demonstrate that the MTF of all field of view at Nyquist frequency 39 lp/mm is higher than 0.8, and 80% energy of the system encircled in 8um, which is less than a pixel size, and the distortion is less than 0.1%. All indexes satisfy the commands of system.