Displacement measuring interferometry overview

Light interferometry has many advantages in the area of precision measurement and positioning. It offers high accuracy and resolution, long measuring range, up to hundreds of feet, ease of setup, the capability for making measurements having very low Abbe offset, and the ability to handle small angular displacements of the stage. This paper explains operation of the Michelson interferometer with single-frequency (DC interferometry) and two-frequency sources (heterodyne or AC interferometry). It discusses measurement errors when operating in air and vacuum, and an example application.