Patent ID: 9366857
Filing Date: 2016-06-14
CPC Classification: G02B,G02F,G03F

Claim Text:
1. A device for heating a surface of at least one optical element of a projection objective of a projection exposure system for microlithography, the projection objective comprising a plurality of optical elements arranged along an optical axis, the optical elements being configured to direct 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, the device comprising: a correction light source different from a source of the exposure light; and an optical arrangement configured so that when arranged in the projection objective, the device directs correction light from the correction light source to the optical element via the optical arrangement 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°.