Periodic error correction in heterodyne interferometry

This paper describes periodic error in differential-path interferometry using a Frequency-Path model of the propagation of light from the source to detector in differential-path interferometers. The model identifies each possible path for each light frequency from the source to detector and predicts the number of interference terms that may be expected at the detector output. The behavior of all possible interference terms with respect to optical path changes may be grouped into one of four categories: Optical Power, AC Interference, AC Reference, and DC Interference. A description of a single pass, Michelson-type heterodyne interferometer is given and the periodic error is calculated for a selected system.