Method of error correction for heterodyne transformer

摘要

The invention relates to a method enabling determination of periodic errors of a heterodyne interferometer. According to the method repeated calibration measurement occurs for a constant calibration distance divided up into two distance segments. One of the distance segments is measured with the interferometer and the other is measured by an additional measuring system and does not present a periodical error with regard to the distance measured. Before each calibration measurement the distance segment measured by the interferometer is modified slightly. The second distance segment is modified accordingly in the opposite direction. The sum of the distance segment modifications must correspond to at least one optical wave length of the interferometer around the measuring wave length. Using the various calibration measurement results for the constant calibration distance, the periodic error components are separated and a wavelength dependent error curve is determined in order to correct all interferometer measurements.