Finite Section Thickness

Abstract

The classic applications of stereology and the principal rules which have been derived and applied are specific to the case of planar sections through three-dimensional solids. This is more-or-less the situation in metallographic microscopy, where polished sections cut through the material are examined. It is not so appropriate for many other fields. Light microscopy in biological and medical applications usually looks through a slice of material, for instance cut with a microtome, whose thickness is not negligible. Microscopy of particulates also looks through a thick layer, in which the matrix is transparent air. Confocal light microscopy images an optical section from within material, whose thickness is finite and depends on the numerical aperture of the optics, and whose boundaries are not sharp. Even electron microscopy, which uses much thinner sections than light microscopy, deals with finite sections (the lateral resolution of the images is improved along with the thinner sections so that features much smaller than the section thickness are detected). And in scanning electron microscopy although surfaces are imaged to negligible depth (at least with secondary electrons, if not backscattered electrons or X-rays), the surfaces are rarely flat.