Aberrations of Magnetic Lens having Bell-shaped Field with various Degree of Asymmetry

Abstract

The object of this paper is the improvement of the resolution of the electron microscope by means of magnetic lens having bell-shaped field with various degree of asymmetry.
The author profoundly investigated the spherical constant and the chromatic aberration constant of this lens, and obtained that the desired degree of asymmetry are R₁/R₂1/4 and R₁/R₂=1/1⋅5, where R₁ R₂ are the half field strength distances in the front and rear direction respectively, and in this case the spherical aberration and the chromatic aberration are minimum respectively.
Hence, he obtained the results that the resolution can be made as small as 1 (mμ) by suitable choice of R₁/R₂.