Double-action phase plate in a superimposed oblique-incidence heterodyne laser interferometer

This paper proposes and discusses modified layouts for an oblique-incidence heterodyne interferometer based on interferometers with flat and concave d iffraction gratings. The layout with a concave grating creates the prerequi sites for substantially reducing the size of the measurement apparatus, whi ch can be implemented in the form of a single superimposed monoblock suitab le for monitoring large flat mirrors directly on a grinding-polishing machi ne. (C) 1999 The Optical Society of America. [S1070-9762(99)00908-2].