Patent ID: 7710640
Filing Date: 2010-05-04
Classification: G02B,G03F

Abstract:
1. A projection objective, comprising: at least one lens which as a consequence of intrinsic birefringence causes a maximum retardation of at least 25 nm/cm, wherein the projection objective has an optical compensation of a polarization such that a retardation which is caused by the projection objective is less than 0.25 times as large as the operating wavelength of the projection objective, and the projection objective is configured to be used in a microlithographic projection exposure apparatus, and wherein: the projection objective is configured to operate in an immersion mode, the projection objective is configured to produce at least one intermediate image and comprises an optical subsystem on the image-plane side which projects the intermediate image into the image plane with an image-plane-side projection ratio β the image-plane-side projection ratio β the projection objective is of a purely refractive design.