METHOD AND ARRANGEMENT FOR DETERMINING THE HEATING CONDITION OF A MIRROR IN AN OPTICAL SYSTEM

摘要

The invention concerns a method of and an arrangement for determining the heating condition of a mirror (101, 201, 401, 601, 701, 801) in an optical system, in particular in a microlithographic projection exposure apparatus. In an embodiment the mirror is an EUV mirror and a method according to the invention comprises the following steps: deflecting at least one input measuring beam on to the mirror (101, 201, 401, 601, 701, 801), ascertaining at least one optical parameter of at least one output measuring beam produced from the input measuring beam after interaction with the mirror (101, 201, 401, 601, 701, 801), and determining the heating condition of the mirror (101, 201, 401, 601, 701, 801) on the basis of said parameter.