A charged particle beam focusing apparatus includes a charged particle beam generator configured to project simultaneously at least one non-astigmatic charged particle beam and at least one astigmatic charged particle beam onto locations on a surface of a specimen, thereby causing released electrons to be emitted from the locations. The apparatus also includes an imaging detector configured to receive the released electrons from the locations and to form images of the locations from the released electrons. A processor analyzes the image produced by the at least one non-astigmatic charged particle beam and in response thereto adjusts a focus of the at least one non-astigmatic charged particle beam.