Patent ID: 9069265
Filing Date: 2015-06-30
Classification: G01B,G03F,H01J

Abstract:
1. Interferometer module adapted for emitting a measurement beam and an associated reference beam towards a respective measurement mirror and reference mirror, said interferometer module comprising: a beam combiner for combining a reflection of said measurement beam and said reference beam into a combined beam, a non-polarizing beam splitter for splitting said combined beam into a first split beam and a second split beam, each split beam comprising a component of said reference beam and said measurement beam, a first polarizing beam splitter, for splitting said first split beam into a first polarized beam having a first polarization and a second polarized beam having a second polarization, a second polarizing beam splitter, for splitting said second split beam into a third polarized beam having a third polarization and a fourth polarized beam having a fourth polarization, a first, second, third and fourth detector for detecting a beam energy of said first, second, third and fourth polarized beams respectively, wherein said polarizations of said first, second, third and fourth polarized beams are different polarizations.