等离子体诊断用Schwarzschild显微镜的光学设计

Optical design of Schwarzschild microscope for plasma diagnostics

基于三级像差理论设计了用于激光等离子体诊断的极紫外Schwarzschild显微镜光学系统。显微镜的工作波长为18.2 nm,数值孔径为0.1,放大倍数为10。光学设计得到中心视场空间分辨力达0.3μm,±1 mm视场内分辨力约0.4μm的结果。分析了Schwarzschild成像系统的物镜装配、系统装调及光学元件加工误差对像质的影响,结果显示光学元件局部面形误差是影响系统成像分辨力的主要因素。通过提高系统装调的精度,可以有效补偿像距误差、两镜间距误差及曲率半径误差对像质的影响。综合考虑实际加工和装调能力,制定了系统整体公差方案,考虑公差后光学系统能够在±1 mm视场内获得3μm的空间分辨力,达到了等离子体诊断的要求。

Based on the third order aberration theory,the optical system of an EUV Schwarzschild microscope is designed for laser plasma diagnostics.The microscope works at 18.2 nm with the numerical aperture of 0.1 and the magnification of 10.The optical system is optimized to achieve the spatial resolution of 0.3 μm in the center field and about 0.4 μm in the field of ±1 mm.The influences of Schwarzschild system tolerances are analyzed in the aspects of system assembly,alignment and components fabrication.The results show that the optics surface irregularity is the main factor affecting imaging resolution;by improving the accuracy of system alignment,the deterioration of resolution,resulting from imaging distance tolerance,and the spacing and the curvature radius tolerances of objectives,can be effectively compensated.The overall system tolerance is formulated with the comprehensive consideration of the current fabrication and alignment capabilities.With the addition of all the tolerance factors,the optical system obtains a spatial resolution of 3 μm in the field of ±1 mm,and can reach the requirements of laser plasma diagnosis.