To irradiate a target with a beam of energetic radiation formed by electrically charged particles, the beam is formed and imaged onto a target, where it generates a pattern image composed of pixels. The pattern image is moved along a path on the target over a region to be exposed, and this movement defines a number of stripes covering said region in sequential exposures and having respective widths. The number of stripes is written in at least two subsequent passes such that for each pass, the widths of the stripes of one pass combine into a cover of the total width of the region to be exposed; and each pass is associated with one of a number of partial grids of pattern pixels which are exposable during the respective pass. The mutually different partial grids combine to the complete plurality of pattern pixels which compose the region to be exposed.