Research On Environmental Error Of Dual Frequency Laser Interferometer Measurement System

As a non-contact measurement method,laser measurement technology is widely used in the fields of precision testing,machine tool processing,equipment testing,etc.The dual frequency laser interferometer can measure the accuracy of nano and even sub nano,which has the advantages of high resolution,large range and high dynamic speed measurement.Because the measurement standard of the dual frequency laser interferometer is laser wavelength,the wavelength is easily affected by the fluctuation of ambient temperature,pressure and humidity when the wavelength is transmitted in the air,which will reduce the measurement accuracy of the interferometer.Therefore,the paper takes the measurement system of double frequency laser interferometer as the research object,and studies the influence of environmental factors on the measurement system.The main research contents are as follows:(1)Based on the basic displacement measurement principle of interferometer measurement system,the relationship between the air refractive index and the displacement measurement value of interferometer is deduced when the external environment changes.According to the requirement of interferometer measurement system,the components of each module of the measurement system are analyzed in detail.It includes the selection of main devices of laser light source module,the installation and debugging of optical platform,the design and force simulation of mechanical parts,the hardware functional structure of signal processing module and the function analysis of each board.(2)According to the characteristics of the measurement system,the main sources of environmental errors in the system are analyzed.The simulation analysis and key evaluation of some important errors are carried out to get the corresponding optimization scheme.Using MATLAB software to complete the simulation analysis of the influence of environmental parameters on the air refractive index;the influence of deformation caused by heating of optical elements on the measurement system is discussed;the finite element analysis of the measurement system is carried out by ANSYS software to get the influence of external vibration on the measurement system;The influence of air disturbance on laser beam drift in different optical path length measurement is studied,which provides a basis for subsequent experiments.(3)In order to verify the influence of environmental factors on displacement measurement,a set of double frequency laser interferometer measuring platform is built,which includes system performance test,and environmental compensation experiment.The experimental results and compensation effect are analyzed in detail.Performance test before taking isolation measures: the displacement measurement values of interferometer at 40 mm and 30 mm are 32.36 nm and 25.71 nm respectively,which are poor stability.Performance test experiments after taking isolation measures: the displacement measurement values measured by interferometer at optical range of 40 mm,30mm and18 mm are 30.25 nm,14.58 nm and 4.85 nm respectively,and the system stability is enhanced.The experimental results show that when the ambient temperature is 23.91,the displacement measurement error is 10.48 nm,and the measurement error increases with the increase of the actual measurement environment temperature,which is approximately linear.The indirect compensation method is used to complete the environmental compensation of the measurement system.When the optical distance is 18 mm,the displacement measurement value after compensation decreases by about 2%;when the optical distance is 30 mm,the displacement measurement value is decreased after compensation under the two conditions before and after the isolation measures are adopted;when the sampling time is increased,the difference between the compensation value and the actual measurement value is presented with time change The compensation effect will be enhanced gradually.