Abstract: An interferometer is provided which includes a source for generating a source beam of linearly polarized coherent light along a light path; a non-polarizing beam splitting, combining and resplitter disposed in the path of the source beam for splitting the source beam into a reference beam and a measuring beam and for recombining the reference and measuring beams into an interfering beam and resplitting the interfering beam into a first output beam and a second output beam; a reference reflector positioned in the reference beam for causing the reference beam to traverse a reference path and return to the non-polarizing beam splitting means; a measuring reflector spaced a distance to be measured from the non-polarizing beam splitter for causing the measuring beam to traverse a measured path and return to the non-polarizing beam splitter; a half wave plate in one of the reference and measuring beams for rotating the polarization of the measuring beam relative to the reference beam prior to recombining the measur