Patent ID: 7435956

Claim:
A charged particle optical system for the production of a charged particle beam deflectable through a large angle in the direction of a main scan axis, comprising: a charged particle optical assembly configured to produce a charged particle beam focused on a specimen plane; and an electrostatic deflector aligned on the optical axis of said optical assembly and positioned between said optical assembly and said specimen plane, said deflector having an exit aperture and an entrance aperture, said electrostatic deflector comprising: two parallel plates substantially perpendicular to said main scan axis and substantially parallel to said optical axis, said plates being positioned equidistant from said optical axis, said plates having chamfered inner surfaces; and a multiplicity of electrodes positioned peripherally in the gap between said plates, said electrodes being configured to maintain a uniform electric field transverse to said main scan axis; wherein said exit aperture has a larger area than said entrance aperture.