| 摘要 |
An embodiment of a symmetry forming device for an alignment system can include an interferometer, a compensator, and an analyzer. The interferometer can be configured to receive a light beam, where the light beam can be produced from a light source or from combining beams from a plurality of light sources. Further, the interferometer can be configured to split the light beam into two beams, rotate one beam 180 degrees with respect to the other beam about an axis of rotation, and recombine the two beams to form a recombined beam. The compensator can be configured to adjust a path length of either the combined or the recombined beam in first and second polarization directions to form an adjusted light beam. The analyzer can be configured to pass a polarization direction or an amplitude and phase profile of either the recombined or adjusted light beam, where the recombined or adjusted light beam is directed onto a substrate.
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