Key Technologies Study Of Dynamic Displacement Calibration For High Speed Heterodyne Laser Interferometer Based On The Same Measurement Trajectory

Heterodyne laser interferometer is an important displacement detecting technology in the fields of super precision engineering,nano science technology and others.The interferometer dynamic displacement calibration is a necessary technical means to ensure dynamic measurement accuracy and to realize its traceability and standardization.With the continuous improvement of the dynamic displacement measurement precision and measurement speed of heterodyne laser interferometer,high precision and high speed calibration method and technique of heterodyne laser interferometer dynamic displacement measurement is becoming a pressing need.The cosine,Abbe and air refractive index difference errors in the calibration,and how to calibrate the key dynamic performance index——data age error have become bottleneck problems for high precision and high speed dynamic displacement measurement calibration of heterodyne laser interferometer.This paper mainly studies on solving the problems of cosine,Abbe,air refractive index difference errors in the calibration and how to calibrate data age error,a dynamic displacement measurement calibration method of heterodyne laser interferometer based on the same measurement trajectory and data age error calibration approach based on the same measurement trajectory calibration method are presented.The main research content is as follows:1.To solve Abbe and air refractive index difference errors in the calibration,a dynamic displacement measurement calibration method of heterodyne laser interferometer based on the same measurement trajectory is proposed.A standard interferometer is designed to make the measurement axis of calibrated interferometer be clamped in the middle position of the four parallel beams of the standard interferometer,which realizes the same displacement measurement direction,common measurement axis and common measurement point interferometer displacement measurement calibration.On the basis of deducing the displacement measurement model of the standard interferometer,two models of displacement calibration and air refractive index difference error are established,it is proved that this calibration method can eliminate Abbe and air refractive index difference errors in the calibration through analyzing the two models.The analysis shows that Abbe and air refractive index difference errors are below 2nm and 1nm in the 10 m displacement range,respectively.2.To solve cosine error in the calibration,an optical axis parallelism adjustment method based on beam orientation vector is proposed.The dual PSD-based orientation measurement unit for beam direction detection and double-wedge lens group for beam direction adjusting are designed,the corresponding beam direction measurement model and adjustment model are established,on the basis of obtaining beam direction vector,it is able to non coupling two-dimension rotate the beam direction into the aim direction to realize optical axis parallelism accurate adjustment,which provides technical assurance for the suppressions of Abbe and air refractive index difference errors in the calibration while restraining cosine error in the calibration.The analysis shows that this method is able to achieve 2" optical axis parallelism adjustment,which makes the cosine error be below 0.1nm in the 10 m displacement range.3.To solve how to calibrate data age error,a data age error calibration approach based on the same measurement trajectory calibration method is proposed.The data age error calibration model is presented and reasearched through analyzing the data age error model of interferometer displacement measurement.According to the principle of this calibration model,and at the condition of the same measurement trajectory calibration method,the data age error calibration with the resolution level of interferometer measurement is realized by means of the difference variation of instantaneous calibration results during acceleration process,which provides the necessary groundwork for the further study of the interferometer data age error calibration in the future.Experiment data shows that the calibration accuracies of the data age error and data age are better than 3nm and 5ns,respectively.Based on the above research,the dynamic displacement measurement calibration system of heterodyne laser interferometer based on the same measurement trajectory is built up.The optical axis parallelism adjustment method is verified,experiment data shows that beam direction detection accuracy is 1" and adjustment accuracy is 2",which satisfies the requirement of optical axis parallelism being 2".The established air refractive index difference error and displacement calibration models are verified,it is proved that this same measurement trajectory calibration method can eliminate air refractive index difference,Abbe and cosine errors in the calibration.In the 10 m displacement range,experiment data shows that the model value of air refractive index difference error relative to its experimental value only exists 13% deviation,the actual value of air refractive index difference error is less than 1.2nm according to this deviation relationship;Uncertainties of deviations between model and experimental values for Abbe and cosine errors respectively,are both in the wavelength stability 2×10-9 of the calibrated interferometer laser;The calibration repeatability of this same measurement trajectory calibration method is better than 20 nm.