| The laser interferometer is an important method to achieve large-scale nanometer measurement.There are many factors that affect the measurement accuracy,such as the laser power stability,air turbulence,circuit noises,and optical imperfections,which can introduce the measuring signal amplitude stability and phase errors.Therefore,the real-time signal error compensation of the laser interferometer is the crucial to achieve high-precision measurement.In this paper,based on the interference theory,the characteristics of laser interferometer signal errors have been analyzed.the real-time and high-precision signal processing system was developed including signal error compensation,signal demodulation and subdivision with the high-speed signal acquisition card and LabVIEW software platform.The main contents are as follows:(1)The polarization interference optical path was designed,the error of the optical path has been analyzed.(2)The photoelectric conversion circuit including the photoelectric detection module and amplifying circuit module was designed.The performance test shows that the circuit can optimize the output signal quality through gain adjustment and filtering,and improve the signal to noise ratio of the orthogonal signal.(3)Based on the accuracy and real-time requirements,the signal error compensation and signal demodulation algorithms was developed,the signal acquisition,demodulation and subdivision modules have been programmed in the environment of LabVIEW,which can realize real-time demodulation and error compensation of the interference signals.(4)Comparative experiment with Renishaw XL-80 laser interferometer was setup to test the performance of the measuring signal processing system.Experimental results show that the signal processing methods of laser interferometers can achieve the resolution 40 nm and the stability ±5nm with measuring range 20 mm.. |
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