摘要 |
An illumination system for a microlithographic projection exposure apparatus has a first polarization manipulator, a second polarization manipulator and at least one optical element located between these manipulators. The polarization manipulators ensure that the direction of the electric field vector of a light ray varies in time between the polarization manipulators, whereas the polarization state is fixed outside the polarization manipulators. This prevents high energy light from inducing birefringence in optical elements arranged between the two polarization manipulators.
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