Stigmator algebra - a new approach to the theoretical study of astigmatism

An algebra has been devised in which axial asymmetries, such as those causing astigmatism in electron lenses, may be treated directly. The extent to which the algebra has been developed is indicated. Although originally devised for use in electron microscopy, the algebra can be generalized and then shows a similarity to existing aberration theories and aberration correction systems. The nature and extent of this relationship is under consideration.