A multi-beam pattern definition device for use in a particle-beam processing or inspection apparatus, said device being adapted to be irradiated with a beam (lp,bp) of electrically charged particles and allow passage of the beam through a plurality of apertures thus forming a corresponding number of beamlets, said device comprising - an aperture array means (202, 812, 822, 832, 842, 852) in which said apertures are realized, wherein the aperture array means comprises at least two sets of apertures (221, 222; 931, 932, 933), each set of apertures comprising a plurality of apertures arranged in a substantially regular arrangement on the aperture array means with the arrangements of said sets being interlacing at least partially, wherein the apertures of different sets are, at least in a region where the arrangements are interlacing, offset to each other by displacements which correspond to a common displacement vector (d12, d13), - an opening array means (201, 813, 824) having a plurality of openings configured for the passage of at least a subset of beamlets that are formed by said apertures, wherein, in at least a region corresponding to said region of interlacing of arrangements, the opening array means comprises plurality of openings arranged in a substantially regular arrangement, said arrangement corresponding to the arrangement of one of said sets of apertures in said region and lacking openings at locations corresponding to apertures of the other set(s) of apertures, and - positioning means for positioning at least one of the aperture array means and the opening array means for adjusting the relative position of the aperture array means with respect to the opening array means, said positioning means being configured to selectively bring a selected set of the sets of apertures in the aperture array means into alignment with the plurality of openings in the opening array means in at least said region of interlacing of arrangements. - an aperture array means (202, 812, 822, 832, 842, 852) in which said apertures are realized, wherein the aperture array means comprises at least two sets of apertures (221, 222; 931, 932, 933), each set of apertures comprising a plurality of apertures arranged in a substantially regular arrangement on the aperture array means with the arrangements of said sets being interlacing at least partially, wherein the apertures of different sets are, at least in a region where the arrangements are interlacing, offset to each other by displacements which correspond to a common displacement vector (d12, d13), - an opening array means (201, 813, 824) having a plurality of openings configured for the passage of at least a subset of beamlets that are formed by said apertures, wherein, in at least a region corresponding to said region of interlacing of arrangements, the opening array means comprises plurality of openings arranged in a substantially regular arrangement, said arrangement corresponding to the arrangement of one of said sets of apertures in said region and lacking openings at locations corresponding to apertures of the other set(s) of apertures, and - positioning means for positioning at least one of the aperture array means and the opening array means for adjusting the relative position of the aperture array means with respect to the opening array means, said positioning means being configured to selectively bring a selected set of the sets of apertures in the aperture array means into alignment with the plurality of openings in the opening array means in at least said region of interlacing of arrangements.