A phase differential heterodyne interferometer for simultaneous measurement of straightness error and displacement

Abstract A phase differential heterodyne interferometer for simultaneous measurement of straightness error and displacement is proposed. In this interferometer, a modified mobile sensor composed of a Wollaston prism and a semi-reflective plane mirror is adopted to obtain the straightness error and displacement information simultaneously. A phase differential measurement is utilized to obtain phase differential signals for straightness error and displacement measurement, respectively, by using phase retarder and polarizing beam-splitter. Based on the relationship of π phase difference between the nonlinear errors of phase differential signals, the periodic nonlinear error of measurement results can be compensated. Benefiting from this design, the proposed interferometer can not only obtain the straightness error and displacement simultaneously, but also reduce the nonlinearity of measurement and the influence of the measured object’s rotation. The optical configuration and measurement principle are described in detail. The influence of Wollaston prism’s roll error is also discussed. And three verification experiments are presented at last.