Patent ID: 7408716
Filing Date: 2008-08-05
Classification: G02B,G03F

Abstract:
1. A refractive projection objective, for projecting a pattern arranged in an object plane of the projection objective into an image plane of the projection objective, comprising: a first lens group with negative refractive power following the object plane; a second lens group with positive refractive power following the first lens group; a third lens group with negative refractive power following the second lens group; a fourth lens group with positive refractive power following the third lens group; a fifth lens group with positive refractive power following the fourth lens group; and a system aperture that is arranged in a transition region from the fourth lens group to the fifth lens group, so as to form a single-waist system with an object-side belly, an image-side belly and a waist, arranged between the object-side belly and the image-side belly, with a constriction site of narrowest constriction of a beam, a waist distance AT existing between the object plane and the constriction site, and the condition AT/L≦0.4 holding for a distance ratio AT/L between the waist distance AT and an object-image distance L of the projection objective; wherein the fifth lens group comprises, as a last optical element, a plano-convex lens with a curved entrance surface and a substantially flat exit surface.