Patent attributes
A system is disclosed that includes an interferometric sensor for measuring the wavefront of a radiation beam at, the interferometric sensor having a detector; an actuator for displacing the interferometric sensor in a direction along an optical axis; a first module for determining the change of phase of the wavefront at each of a plurality of locations on the detector, the change of phase resulting from displacement of the interferometric sensor by the actuator; and a second module for determining, for each of the plurality of locations, the corresponding pupil location at a pupil plane of the projection system traversed by the radiation, using the change of phase determined by the first module and the value of the displacement of the interferometric sensor, to produce a mapping between locations on the detector and corresponding pupil locations.
