| Abstract: | The nonlinearity of heterodyne interferometers is mainly influenced by the nonorthogonality and ellipticity of the linearly polarized partial beams of the laser and by the limited extinction capability of the polarizing beam splitters. The phase errors at the interferometer output can be detected by measuring the phase difference between the two orthogonal directions in the output beam. This arrangement can be used to check an interferometer setup for causes of nonlinearity and to eliminate them by adjustment, replacement, etc. The arithmetical mean value of the phases of the two orthogonal output signals is linear, except for a residual error. These detection and compensation capabilities of the proposed phase measurement arrangement are demonstrated by experimental investigations. |
