大视场大相对孔径斜轴离轴三反望远镜的光学设计

Optical Design of Wide Field View and Large Relative Aperture Off-axis Three-mirror Reflective System with Tilted Optical Axis

推导了离轴三反光学系统的线性像散平衡条件,在此基础上采用倾斜母镜光轴的方法设计了大相对孔径时大视场像散校正的斜轴离轴三反光学系统.系统视场为5°×5°,相对口径为1/3.1,口径为250mm,波段为400～2 500nm.将该系统与相同光学参数的共轴二次非球面离轴三反系统和共轴高阶偶次非球面离轴三反系统进行对比.结果表明斜轴离轴三反光学系统所有视场的光学传递函数在17lp/mm处均大于0.73,由于反射面采用圆锥曲面,其在偏轴视场成像质量方面有明显优势.对斜轴离轴三反光学系统的加工与装调进行了分析,其公差较为宽松,验证了其结构实现的可行性.

The linear astigmatism balance condition of the off-axis three-mirror optical system was deduced, on that base the off-axis three-mirror reflective system for astigmatism correction with large relative aperture and large field of view was proposed by tilting the optical axis. The field of view is 5°×5°, relative aperture is 1/3.1, entrance pupil diameter is 250 mm and spectral range is 400~2 500 nm. The proposed system was compared with the off-axis three-mirror reflective system of coaxial quadratic aspheric surface and the off-axis three-mirror reflective system of coaxial high-order even aspheric surface with the same optical parameters. The results show that the optical transfer function of off-axis three-mirror reflective system with tilted optical axis is greater than 0.73 at 17 lp/mm in all field of view. It uses conical surfaces and shows obvious advantages in imaging quality. In addition, the processing and adjustment of off-axis three-mirror reflective system with tilted optical axis are analyzed, the tolerance is relatively loose and the structure can be realized.