Nonlinear filtering in two-beam interferometer.
A nonlinear filtering setup visualizes wavefront 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.
Parfenev
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Lebedev Physics Institute, Moscow, Russia.