Patent ID: 8537335

Claim:
An illumination system configured to illuminate an illumination field, the illumination system comprising: a variably adjustable pupil shaping unit configured to receive light and to generate a variably adjustable two-dimensional intensity distribution in a pupil shaping surface of the illumination system, wherein: the pupil shaping unit comprises a Fourier optical system configured to convert an entrance beam bundle entering through an entrance plane of the Fourier optical system into an exit beam bundle exiting from an exit plane of the Fourier optical system; the Fourier optical system has a focal length f FOS ; the Fourier optical system has a structural length L between an entrance-side first system surface and an exit-side last system surface along an optical axis; (L/f FOS )<1/6; and the illumination system is configured to be used in a microlithography projection exposure apparatus.