A nonlinear filtering setup visualizes wave-front aberrations. In a single-beam scheme, however, the negative and positive phase shifts cannot be distinguished. As an improvement, a two-beam nonlinear scheme is proposed. It has self-aligning properties and mechanical stability, and can be used for remote testing of large optical objects such as photolithography masks, liquid crystal substrates, jet streams and turbulence.
© 2000 Optical Society of America
Alexander Parfenev, "Nonlinear Filtering in Two-Beam Interferometer," Appl. Opt. 39, 6515-6517 (2000)