Optical fringe subdivision with nanometric accuracy

Abstract Reliable bidirectional optical fringe counting is normally obtained by using two signals derived from the optical outputs of an interferometer varying sinusoidally with path difference and in phase-quadrature. This paper describes a calibration technique that uses these signals to achieve nanometric uncertainties in path length determinations. It discusses some of the limitations to achieving this uncertainty and describes a simple experimental technique for verifying the accuracy of fringe subdivision.