METHOD AND DEVICE FOR DETERMINING A HEATING STATE OF AN OPTICAL ELEMENT IN AN OPTICAL SYSTEM

The invention relates to a method and an apparatus for determining the heating state of an optical element in an optical system, more particularly in a microlithographic projection exposure system, in which during operation of the optical system electromagnetic radiation impinges on an incident surface (401) of the optical element (400), in which the heating state of the optical element (400) is determined by using calibration parameters. The average temperature at the incident surface is estimated based on temperature measurements performed by at least one temperature sensor (420) located at a distance from the incident surface (401), and wherein the calibration parameters are selected differently according to illumination settings set in the optical system. 本发明涉及一种用于确定光学系统中、更具体地说是微光刻投射曝光系统中的光学元件的加热状态的方法和装置，其中，在光学系统的操作期间，电磁辐射撞击光学元件(400)的入射表面(401)，其中，通过使用校准参数，基于通过位于距入射表面(401)一定距离处的至少一个温度传感器(420)执行的温度测量来估计入射表面处的平均温度，并且其中，根据光学系统中设定的照明设置来不同地选择所述校准参数。