一种极低场曲复合聚焦偏转系统的设计

Design of Extremely Low Field Curvature Combined Focusing and Deflection Systems

本文提出了一种用系统本身预偏转和主偏转象差相抵消来消除电子光学场曲的方法。采用解析函数近似表示系统场分布和电子轨迹,对象差进行了理论分析和解析计算,表明在一定条件下,可以完全消除复合聚焦偏转系统的彗差和横向色差,并使场曲达到极小。由设计实例可见,该系统在10×10mm^2扫描范围内,场曲仅为0.013μm。

This paper proposes a method of eliminating the field curvature aberration in combined focusing and deflection systems, by means of canceling the pre-deflection aberration with the main-deflection aberration. A theoretical aberration analysis indicates that under certain conditions, both the coma and the transverse chromatic aberrations can be reduced to zero, and the field curvature can be restricted to extremely small. A practical system has been designed, and the maximum field curvature within the 10×10mm2 deflection field is only 0.013μm.