Research On Simultaneous Measurement Of Straightness And Its Position Using A Modified Wollaston-prism-sensing Homodyne Interferometer

For the performance characterization of motion stages or precision guides in all kinds of high-end equipments,straightness is an essential geometric parameter.The measurement of high-precision straightness is a prerequisite for the ensurement of overall property of high-end equipment.In this thesis,a simultaneous measurement of the straightness error and its position using a modified Wollaston-prism-sensing homodyne interferometer is proposed for the demand for the manufacture of high-end equipment.A moving measurement mirror which is combined with a Wollaston prism and a semi-reflective mirror is designed for avoiding the deviation of measuring straightness caused by the rotation.The laser homodyne interferometry is adopted to reduce the nonlinearity and to realize the measurement of straightness and displacement with high-precision.From the actual implementation of measurement,a simultaneous measurement of the straightness error and its position using a modified Wollaston-prism-sensing homodyne interferometer is proposed.Meanwhile,the method for phase detection of modulation and demodulation with a sinusoidal signal combined with triangular signal is adopted to reduce the nonlinear error of phase measurement.For measuring straightness and displacement simultaneously,the displacement of the three beams for measurement are demodulated and it should be metioned that the measurement is achieve without adding any measuring beam.The straightness measurement deviation caused by the rotation of Wollaston prism is analyzed in detail by establishing an error analysis model.According to the model,the effect of straightness error measurement caused by yaw,roll and pitch of the Wollaston prism are studied theoretically.The expression of straightness measurement deviation is derived,and the method of eliminating straightness measurement deviation is proposed according to the expression.Based on the method for phase detection of modulation and demodulation with a sinusoidal signal combined with triangular signal,a signal processing system is designed.The hardware design of the signal processing system is implemented based on the development platform of Quartus ?,and the software design of the measurement system is implemented based on the development platform of Lab VIEW 2015.The collection,analysis,and processing of three measurement signals of straightness error and displacement is completed by the signal processing system.A device for measuring straightness and displacement simultaneously is constructed.The experiment for feasibility,experiment for Wollaston prism rotation error model and experiment for application have been performed respectively.In the experiment for feasibility,the results of experiment prove the accuracy of the measurement method.The standard deviations of the measurement datum in the 0.1 ?m and 0.01 ?m step straightness error measurement experiments are 11.47 nm and 2.23 nm respectively.The standard deviations of the measurement datum in the 0.1 ?m and 0.01 ?m step displacement measurement experiments are 0.57 nm and 0.78 nm respectively.In the experiment for Wollaston prism rotation error model,the results of experiment prove the accuracy of the model.In the range of 0 to 216 ?rad,the measurement values in yaw and roll motions are maintained between ± 0.032 ?m,and the measurement values in pitch is maintained between±0.048 ?m when the mounting point is in the suitable position.In the experiment for application,the experimental datum of straightness error and displacement are compared with the measurement datum of Renishaw's XL80 interferometer and the standard deviations are 0.299 ?m and 0.048 ?m respectively.