Patent ID: 7209292

Claim:
Projection objective for projecting a pattern arranged in an object plane of the projection objective into an image plane of the projection objective, having a multiplicity of optical elements which are arranged along an optical axis of the projection objective, wherein: the optical elements comprise a first group of optical elements following the object plane, and a last optical element following the first group, arranged next to the image plane and defining an exit surface of the projection objective which is arranged at a working distance from the image plane; the last optical element is substantially without refracting power and has at most slight curvature; and the projection objective is adapted with reference to aberrations to the effect that the working distance is filled up with an immersion medium with a refractive index substantially greater than 1; wherein a sum of the free distance in front of the last optical element and the distance between the exit surface and image plane is greater than approximately 0.5% of the overall length of the projection objective.