Patent ID: 7292312

Claim:
A lithographic apparatus, comprising: a substrate support configured to support a substrate; an illuminator configured to condition a beam of radiation; a patterning device support configured to support a patterning device that imparts a desired pattern to the beam of radiation; a projection system configured to project the patterned beam onto a target portion of the substrate; and a motion control system configured to control a motion of the substrate support or the patterning device support, the motion control system comprising a plurality of position detectors that detect a position of the substrate support or the patterning device support, wherein the plurality of position detectors comprises at least three interferometer encoder combinations, each comprising a one- or two-dimensional encoder grid, an optical sensor and an interferometer, wherein the one- or two-dimensional encoder grid of each of the at least three interferometer encoder combinations is constructed and arranged to co-operate as a reflecting target of the respective interferometer, wherein the optical sensor of each of the at least three interferometer encoder combinations is mounted to the motion controlled support and wherein the one- or two dimensional encoder grid of each of the at least three interferometer encoder combinations is mounted to a reference frame such that the position of the motion controlled support relative to the reference frame can be determined in 6 degrees of freedom.