Geometrically Modified Einzel Lenses, From the Conventional Cylindrical Einzel Lens to Cubic and Continuous Einzel Lens

New geometrical counterparts to the conventional Einzel lens, cubic, and the continuous body electrostatic (CBE) lenses are introduced and their performances are investigated in terms of different aberrations and input beam properties. Design curves for the continuous body electrostatic lens are presented. Relative sensitivity is proposed as a figure of merit, based on which the focusing characteristics of the two new lenses are compared with that of a conventional Einzel, and a quadrupole lenses of the same size, as well. Moreover, performance and characteristics of the lenses are compared in terms of their corresponding sensitivities to the applied voltage and the incidence beam nonidealities. Electric field distributions of the lenses are studied, and different aberrations are discussed. It is shown that considering chromatic nonparaxial beams, the CBE lens outperforms the conventional Einzel lens in terms of the sensitivity and the absolute value of the lens demagnification.