ios and a projection optical system pos of a charged particle beam cpb microlithography apparatus useful for making relatively large area batch transfers of pattern portions defined on a divided reticle fig3 also depicts certain optical relationships relevant to understanding the invention an illumination beam b 11 is produced by an electron source 1 desirably comprising a planar electron emitting surface the source 1 is situated at an extreme u201c upstream u201d end of the illumination optical system ios and emits an illumination beam b 11 in a u201c downstream u201d direction a first illumination lens 3 is situated below the electron source 1 the first illumination lens 3 converges the illumination beam b 11 onto a downstream beam shaping aperture plate 5 although the beam b 11 downstream of the first illumination lens 3 is denoted b 12 the beam b 12 nevertheless is the illumination beam the beam shaping aperture plate 5 defines a beam shaping aperture 6 the beam shaping aperture 6 has a prescribed size and profile through which a portion of the illumination beam b 12 passes other portions of the beam b 12 are blocked by the beam shaping aperture plate 5 the portion of the illumination beam b 12 passing through the beam shaping aperture 6 is denoted b 13 which nevertheless is the illumination beam a second illumination lens 7 is situated downstream of the beam shaping aperture 6 and a reticle stage 9 is situated below the second illumination lens 7 a reticle 31 is mounted on the reticle stage 9 the reticle 31 defines a pattern comprising a large number of pattern elements only one pattern element 33 is shown as an aperture.