Optical element for forming an arc-shaped illumination field

摘要

The invention relates to an optical Element for forming an arc-shaped field in a field plane of an illumination system for wavelengths ≤ 193nm, preferably ≤ 126nm, especially EUV-wavelengths, wherein the arc-shaped field has an axis of symmetry (100) and the field plane (16) is defined by a vector in y-direction, which is in parallel to the axis of symmetry and a vector in x-direction, which is orthogonal to the axis of symmetry said optical element comprises a plurality of mirror surfaces (12.1,12.2,12.3) each comprising an array of aspherical reflecting elements wherein said array of aspherical reflecting elements comprise a plurality of cylindrical mirrors with aspheric curvature in x-direction and said plurality of mirror surfaces are forming a nested mirror (10), wherein two adjacent mirror surfaces have a spacing dspace. <IMAGE>