离轴三镜系统光学元件间补偿关系研究

Study on Compensation Relationships Among the Elements in Off-axis Three-mirror System

分析了离轴三镜系统中光学元件调整变量间的补偿关系和面形误差与调整变量间的补偿关系.调整变量中偏心变量和倾斜变量的位置失调常常会产生同种像差,存在一定的相关性.从失调像差理论出发,通过平衡偏心变量和倾斜变量产生的初级像差,得到偏心变量和倾斜变量间的补偿关系.利用Zernike多项式模拟面形误差,建立面形误差与初级像差的关系,使面形误差与调整变量联系起来.通过计算机模拟,给定光学元件一定的面形误差,然后调整光学元件的偏心、倾斜和横向位移进行补偿,发现当次镜带有1λ像散的面形误差时,补偿后系统波前误差只下降了0.01λRMS.

The compensation relationships among the adjustable variables and those between surface errors and the adjustable variables in off-axis three-mirror system are analyzed. The decenter variable in the adjustable variables often brings the same kind of aberration as the position offset of the tilt variable does, so they are of considerable relativity. Based on the theory of offset aberration, the relationship between decenter variables and tilt variables is obtained by compensating the primary aberration caused by both the decenter variables and the tilt variables. The adjustable variables and surface errors are correlated by modeling the relationship between surface errors which is represented by Zernike polynomials and the primary aberration. The precondition of computer simulation for compensation is to adjust the decenter, tilt and transverse displacement of the optical elements when given a certain value of surface error. The result shows that the wave front performance degradation of compensated system is only 0. 01λ RMS, when compensating the secondary mirror with surface errors of 1λ P-V astigmatism.