Lithographic Apparatus and a Method for Determining a Polarization Property

A lithographic apparatus includes an illumination system, a support, a patterning device, a substrate table, a projection system, and a detector. The apparatus further includes a polarization changing element, such as a quarter-wave plate, that is adjustable and a polarization analyzer, such as a linear polarizer. The polarization changing element and the polarization analyzer are arranged in order in the radiation beam path at the level at which a patterning device would be held by the support. By taking intensity measurements for different rotational orientations of the polarization changing element, information on the state of polarization of the radiation at the level of the patterning device can be obtained. Because the polarization analyzer is located before the projection system, the measurements are not affected by the fact that the detector is located after the projection system, such as at the level of the substrate.