An ion beam device is described. The ion beam device includes an ion beam source for generating an ion beam, the ion beam being emitted along a first axis, an aperture unit adapted to shape the ion beam, and an achromatic deflection unit adapted to deflect ions of the ion beam having a predetermined mass by a deflecting angle. The achromatic deflection unit includes: an electric field generating component for generating an electric field, and a magnetic field generating component for generating a magnetic field substantially perpendicular to the electric field. The device further includes a mass separation aperture adapted for blocking ions with a mass different from the predetermined mass and for allowing ions having the predetermined mass to trespass the mass separator, and an objective lens having a second optical axis, wherein the second optical axis is inclined with regard to the first axis.