OBJECTIVE LENS ARRANGEMENT
An objective lens arrangement that may include a magnetic lens and an electrostatic lens. The magnetic lens may include one or more coils, an upper polepiece and a lower polepiece. The electrostatic lens may include an upper electrode, an internal lower electrode and an external lower electrode. A majority of the internal lower electrode may be surrounded by a majority of the external lower electrode. The upper electrode, the internal lower electrode, and the external lower electrode are arranged in a coaxial relationship along an optical axis of the objective lens arrangement. An area of a bottom aperture of the external lower electrode may not exceed an area of a bottom aperture of the internal lower electrode.