Disclosed is a charged particle optical apparatus. The charged particle optical apparatus has a liner electrode in a first vacuum zone. The liner electrode is used to generate an electrostatic objective lens field. The apparatus has a second electrode which surrounds at least a section of the primary particle beam path. The section extends in the first vacuum zone and downstream of the liner electrode. A third electrode is provided having a differential pressure aperture through which the particle beam path exits from the first vacuum zone. A particle detector is configured for detecting emitted particles, which are emitted from the object and which pass through the differential pressure aperture of the third electrode. The liner electrode, the second and third electrodes are operable at different potentials relative to each other.