Patent ID: 8228483

Claim:
A projection objective comprising: a plurality of optical elements arranged to image a pattern from an object field in an object surface of the projection objective to an image field in an image surface of the projection objective with electromagnetic radiation from a wavelength band around an operating wavelength λ, the plurality of optical elements comprising: an optical correction plate comprising a body comprising a material transparent to the radiation, the body having a first optical surface, a second optical surface, and a plate normal substantially perpendicular to the first and second optical surfaces, wherein: the first optical surface has a non-rotationally symmetric aspheric first surface profile with a first peak-to-valley value PV 1 >λ; the second optical surface has a non-rotationally symmetric aspheric second surface profile with a second peak-to-valley value PV 2 >λ; and a thickness of the optical correction plate varies by less than 0.1*(PV 1 +PV 2 )/2 across the optical correction plate.