Determination of the aspect ratio of a spheroidal particle by stereo observation

A geometrical analysis is presented for the aspect ratio determination of a spheroidal particle by stereo observation. Orthogonal projections of particle shape are obtained from images in electron micrographs. The aspect ratio of the spheroidal particle is expressed as a function of the changes in the shape and direction of the projected images caused by tilting. Although two different values of the aspect ratio are generally obtained from a pair of stereo micrographs, the ambiguity can be avoided if the particle is observed from three different directions. As an example, the results obtained are applied to the analysis for the shape change of liquid B2O3 particles induced by plastic deformation of a Cu matrix.