In a charged-particle exposure apparatus for exposure of a target with a beam of electrically charged particles, the illumination system includes a deflector device adapted to vary the direction of incidence of the illuminating beam upon the pattern definition device, the pattern definition device forms the shape of the illuminating beam into a desired pattern, and the projection optics system projects an image of the beam shape defined in the pattern definition device onto the target; the projection optics system includes a blocking aperture device having an opening and being adapted to block passage of beams traversing outside the opening, namely when the deflector device is activated to tilt the beamlet by a sufficient angle from its non-deflected path, e.g., for blanking out during the process of loading a pattern into the pattern definition device.