摘要
本文从理想均匀静电场偏转系统三级几何象差的公式出发,导出了由两对互相垂直的偏转板组成的平行平板偏转系统的三级几何象差公式。这些公式不但可用来快速估算偏转象差,还可用来作为校验数字计算程序的理论模型。从水平和垂直方向偏转象散和场曲的影响应相同这一要求出发,提出了一种优化设计方法。在给定偏转区总长度和两对偏转板之间的距离后,可以计算出每对偏转板的最佳长度。文中给出了设计数表,并比较了平行平板偏转系统和八极偏转系统的优缺点。
Formulae of the third order geometric aberrations caused by the pirallcl planar deflection systems consisting of two planar deflectors disposed sequentially and orthogonally have been derived. These formulae can be used as an analytic solution for quickly estimating the geometric aberrations of a known deflection system and checking the related computer program. In view of attaining minimum and equal deflection aberration on the horizontal and vertical sides of a square scanning area, a method of optimum design is proposed. When the total length of the deflection region and the distance between the two deflecrors are given, the optimum length of each of the two deflectors can be calculated by this method:
关键词
几何象差
优化设计
静电偏转
Electrostatic deflection
Geometric aberration
optimum design
