Abstract: Apparatus include a polarization state generator situated to provide an interferometer source beam with a region of polarized source light with a polarization state that is in-plane as subsequently incident on a sample and a region of polarized source light with a polarization state that is perpendicular to in-plane as subsequently incident on the sample, and an interferometer unit configured to split the interferometer source beam into test and reference arm beams, to direct the test arm beam to the sample and the reference arm beam to a reference surface, and to recombine the test and reference arm beams to produce an interferometer output beam. Methods use a polarization state generator to produce an interferometer source beam and use an interferometer unit which splits the interferometer source beam into test and reference arm beams.

Abstract: Apparatus include a polarization state generator situated to provide an interferometer source beam with a region of polarized source light with a polarization state that is in-plane as subsequently incident on a sample and a region of polarized source light with a polarization state that is perpendicular to in-plane as subsequently incident on the sample, and an interferometer unit configured to split the interferometer source beam into test and reference arm beams, to direct the test arm beam to the sample and the reference arm beam to a reference surface, and to recombine the test and reference arm beams to produce an interferometer output beam.