普遍的电偏转三级象差系数及其与光栅图的关系

本文将电偏转三级象差的工作推广,使适合于入射处就有电场的情况,导出一个能在任意平面上求三级偏转象差的公式,对分离式电偏转系统及叠合式偏转系统(Deflection Yoke)均适用。并经过数学处理,使公式简洁,换算方便,还将象差系数积分公式中的轴上场E₀(z)的一、二级微商全部消除,以提高计算精度。为了和我们的前一工作相对应,符号的命名和计算格式也与文献1]相同,最后还描述了顶点在屏上的圆锥形细束在偏转后产生的光栅畸变、场曲、象散、彗差等图形与这套系数的对应关系。这种关系也完全适合于磁偏转三级象差的情况。 关键词：

A GENERALIZED FORMULA OF THE THIRD ORDER ELECTRICAL DEFLECTION ABERRATION COEFFICIENTS AND THEIR RELATION WITH THE RASTER PATTERN

This paper deals with the generalization of the theory of third order aberrations of an electrical deflection system under the situation as the electron beam is originally immersed in an electric field. The formulae of third order electrical deflection aberration coefficients in an arbitrary plane have been derived. It can be applied to either sequential deflection systems or superimposed deflection yokes. By means of mathematical manoeuvres, the formulae are simplified and made easy for calculation. In order to obtain high precision, the first and second order derivatives of the field E₀(z) have been eliminated. In accordance with our previous work, the nomenclature and calculating procedure are kept the same as before, so we can adopt the same computing scheme.Finally, we have described the relations between the patterns of the raster distortion, astigmatism, field curvature, coma, and the corresponding deflection aberration coefficients for a small electron beam which is initially point-focused on the image screen. These relations may also be applied to the third order magnetic deflection aberrations.