Patent ID: 8811568

Claim:
A projection exposure system for microlithography, comprising: an exposure light source to provide exposure light; a projection objective comprising a plurality of optical elements arranged along an optical axis, the optical elements being configured to direct the exposure light from a mask in an object plane of the projection objective to a substrate in an image field of the projection objective during operation of the projection exposure system for microlithography; and a device for heating a surface of at least one of the optical elements, the device comprising: a correction light source different from the exposure light source; and an optical arrangement configured to direct correction light from the correction light source to an optical element of the projection objective such that at least part of a surface of the optical element of the projection objective is irradiated with the correction light, wherein the correction light strikes the part of the surface of the optical element of the projection objective at an angle such that an obtuse angle between the optical axis of the projection objective at the location of the optical element and the correction light is less than or equal to 105°.