Patent ID: 7848016

Claim:
A catadioptric projection objective for imaging a pattern provided in an object surface of the projection objective onto an image surface of the projection objective comprising: an object-side imaging subsystem creating a final intermediate image closest to the image surface from radiation coming from the object surface; an image-side imaging subsystem directly imaging the final intermediate image onto the image surface; the image-side imaging subsystem including a last optical element closest to the image surface and creating a convergent beam having an aperture sin α≧0.8 in the last optical element to provide an image-side numerical aperture NA; the image-side imaging subsystem including, in order, along a propagation direction of radiation: a primary negative lens group having overall negative refractive power; an intermediate positive lens group having overall positive refractive power; a secondary negative lens group having overall negative refractive power; and a final positive lens group having overall positive refractive power and including the last optical element, where the last optical element has only a single refractive index and has a convex entry surface having a radius R LOE of curvature with R LOE /NA<40 mm.