基于轴向梯度折射率校正镜的折反式光学系统设计

A Two-Mirror Catadioptric Optical System with an Axial Gradient-Index Correction Lens

传统的两镜折反式光学系统通常采用两片或多片均匀材料的球面校正镜校正同轴两反系统的剩余像差,为了减少校正镜组镜片数量甚至要引入带有非球面的透镜。采用的单片轴向梯度折射率校正镜即可以校正同轴两反系统的剩余像差,又可以减少校正镜片数。总结了轴向梯度折射率透镜和带有无光焦度校正元件光学系统的初级像差理论,研究了轴向梯度折射率透镜作为两镜折反式光学系统校正镜的设计方法。并且给出了采用单片轴向梯度折射率透镜作为校正镜,焦距为3000 mm,相对孔径为1/8,视场角为1°的两镜折反式光学系统设计。设计结果表明,系统最大视场波前RMS值小于0.07 l,系统弥散圆半径接近艾里斑半径,在50 lp/mm时的传递函数高于0.35,系统的最大畸变小于0.5,最大场曲小于0.2,系统像质接近衍射极限。

Traditional strategy of designing a two-mirror catadioptric optical system employs zero-power correcting elements to balance the residual aberrations, which usually contains two or three refracted, even asphere, lenses. The use of an axial gradient-index （AGRIN） lens can achieve the same goal of aberration correction, as well as a compact and light weight system which employs only one correction element. This paper summarizes primary aberrations theory of the two-mirror catadioptric optical system and the AGRIN lens. A method of designing a two- mirror catadioptric system with an AGRIN lens instead of homogeneous lenses is presented. As an example, a two- mirror catadioptricsystem, whose focal length is 3000 mm, F-number is 8, and the field of view is 1°, is promoted. The design result shows that the wavefront aberration is less than 0.07 λ, the system dispersion radius is close to the radius of Airy, the transfer function at 50 lp/mm is higher than 0.35, the maximum distortion of the system is less than 0.5, the maximum field is less than 0.2, and the image quality almost reaches the diffraction limit.