Patent ID: 7796274

Claim:
A measuring system for optically measuring a microlithography optical imaging system configured to image a pattern arranged in an object surface of the imaging system onto an image surface of the imaging system, the measuring system comprising: an object-side structure carrier comprising an object-side measuring structure arranged on an object side of the imaging system; an image-side structure carrier comprising an image-side measuring structure arranged on an image side of the imaging system; the object-side measuring structure and the image-side measuring structure matched to each other to produce a superposition pattern when the object-side measuring structure is imaged onto the image-side measuring structure by the imaging system; and a detector detecting the superposition pattern in a locally resolving manner; wherein: the imaging system is an immersion system configured to image the pattern onto the image surface with an immersion liquid; at least one of the object-side structure carrier and the image-side structure carrier is arranged in a region of the immersion liquid; and a protective system is provided for the structure carrier arranged in the region of the immersion liquid, the protective system increasing a resistance of the measuring structure of the structure carrier arranged in the region of the immersion liquid to degradation by the immersion liquid.