Lithographic apparatus

摘要

A method of operating a lithographic projection apparatus comprises forming a spot(s) of radiation at the wafer level (14) using a pinhole at reticle level.A sensor (16) is defocused with respect to said spot such that it is spaced apart from said wafer level. The sensor is scanned beneath the spot to measure the angular intensity distribution of radiation at the spot and to determine the intensity distribution at the pupil plane of the projection lens system (10). <IMAGE>