Abstract
The electron-optical properties of the parallel plate analyser are studied by calculating spectrometer functions for high resolutions in cases of different focusing. The spectrometer function is calculated as the convolution product of the partial energy distributions arising from the angular divergence, the width of the slits and the length and shape of the slits. The cases of first order focusing, second order focusing and minimum trace width are considered. The calculations show that by the use of minimum trace width and by optical choice of the contributions from the angular divergence and slit width, some advantages can be gained over second order focusing, but these are smaller than can be expected on the basis of base width considerations for point sources.