Method for determining a radiation power and an exposure apparatus

摘要

Method for determining a mean radiation power $\stackrel{\_}{P_{\mathrm{rad}}^0}$ of electromagnetic radiation of a radiation source, the radiation being intensity-modulated with modulation frequency omega₀, in a predetermined time interval. The method provides a reflector designed to reflect electromagnetic radiation of the radiation source and electromagnetic radiation of a test radiation source, irradiates a predetermined area of the reflector with the source electromagnetic radiation, at least partially irradiates the predetermined area of the reflector with electromagnetic radiation of the test radiation source, measures a omega₀-modulated power component P_test,omega0(t) of a reflected test radiation power P_test(t) of an electromagnetic radiation of the test radiation source, the radiation being reflected from the area, in the predetermined time interval, determines a mean value $\stackrel{\_}{P_{\mathrm{test},{\mathrm{omega}}_0}^0}$ of the measured omega₀-modulated power component P_test,omega0(t) of the reflected test radiation power P_test(t) in the predetermined time interval, and determines the mean radiation power $\stackrel{\_}{P_{\mathrm{rad}}^0}$ from the relationship $\stackrel{\_}{P_{\mathrm{rad}}^0}=a.\stackrel{\_}{P_{\mathrm{test},{\mathrm{omega}}_0}^0},$ where a is a predetermined constant.