Defocussing of charged particle beams transmitted through meshes
Abstract A mesh that separates two regions of different electrostatic field strength exerts a “micro-lensing” effect on charged particles that are transmitted through the mesh, causing the directions of the particles to change. A computational study has been carried out to establish magnitudes of the directional changes for four types of mesh that are commonly used, square holes in thin and thick plates, welded and woven.
An optimal microscope is useful for observing various kinds of samples. However, precise observation of an extended region in depth is difficult, because of the narrow range of depth of focus. To overcome this problem, this paper proposes a method of obtaining a pan-focused stereoscopic image. By using image processing, in-focus areas are extracted from multiple images focused on slightly different depths, and a stereoscopic image is composed with these in-focus areas. The proposed method is applied to the observation of three-dimensional distributions of soil particles, a common problem in the field of civil engineering, and the usefulness of the proposed method is demonstrated.