Journal of Electron Microscopy
Asymmetry of Electron Interference Fringes Produced by an Electron Biprism
Akinori Ohshita, Yasuhiro NUMATA, Yukihiro Mametani, Hiroshi Tomita
Abstract
The intensity distributions of electron interference fringes produced by an electron biprism are usually asymmetric with respect to the central fringe. In order to investigate the effect of the noncircular cross-section of the central electrode of the electron biprism on this asymmetry, the intensity distributions of interference fringes were numerically calculated under the condition of the nonuniform radius of curvature of the central electrode. The calculated results were compared with the experimental ones. It was found that the asymmetry of interference fringes can be caused by the nonuniformity of the radius of curvature of the central electrode. Furthermore it was found that the average visibility of the central and adjacent fringes gives a good approximation to the degree of coherence of electron beam also for the asymmetric interference fringes.