1. A method for forming a pattern on a surface of a target by means of a beam of electrically charged particles, the method comprising: producing said particle beam; directing said particle beam through a pattern definition means producing a patterned particle beam; projecting said patterned particle beam by means of an optical column comprising at least one controllable deflection means onto said target surface to form, at a nominal location on the target, a beam image comprising the image of defining structures in the pattern definition means, wherein during a sequence of exposure steps said beam image is moved to different locations, respectively, by changing the nominal location of the beam image with respect to the target between exposure steps, wherein, during an exposure step, the actual location of the beam image is varied around the respective nominal location by means of said at least one controllable deflection means, through a set of locations realizing a distribution of locations within the image plane centering around a mean location coinciding with the nominal location.