The Method And Experimental Study Of Heterodyne Laser Interferometry Based On Polarization-maintaining Fiber Coupling

Dual-frequency heterodyne laser interferometer has been widely used for its property of high precision,strong anti-interference ability in many fields,such as precision machine tool detection,integrated circuit processing equipment,nanometer measurement,etc.The position error detection of CNC machine tool is an important application direction of dual-frequency laser interferometer,and also an important part of simultaneous measurement of multi-DOF geometric motion error of CNC machine tool.According to the geometric motion error of CNC machine tools,Feng et al.developed a laser high-precision multi-parameter rapid comprehensive measurement instrument for five-axis CNC machine tools.Among that,laser simultaneous measurement of linear guide rail geometric motion error of six degrees of freedom is an important part of the measuring instrument.In order to isolate the heat source,to simplify the optical path,and to realize the instrumentalization of the measuring instrument,the research group proposed to use polarization-maintaining fiber to coupling the dual-frequency laser with the measuring unit for the first time,which means,to use a polarization-maintaining fiber to simultaneously transmit the two orthogonal dual-frequency linearly polarized lights emitted by the dual-frequency laser,which has been proved in the experiment that the measurement can be realized.However,the influence of the polarization-maintaining fiber on the measurement datum dual-frequency laser and the influence on the nonlinear error in the position error measurement will reduce the precision of the instrument,which cannot be ignored in the ultra-precision measurement.In this paper,a measurement model for analyzing the nonlinear error caused by the axis misalignment between the laser source and PMF was established with the Jones Matrix.Experiments were performed for verifying and calculating.The results show that the measuring error caused by nonlinear error is less than 2 nm with the axis misalignment being up to 10 degrees.In addition,through investigation and experiment,this paper studies the influence of polarization-maintaining fiber plug on the stability of outgoing light direction and power stability,and completes the selection of fiber connector.Finally,the power stability and polarization stability of the light emitted from the dual-frequency laser based on zeeman effect and the dual-frequency laser coupling fiber based on birefringence are compared through experiments,whichprovides a reference for the selection of the dual-frequency laser of the light source of the measuring instrument.The influence of temperature and force on polarization-maintaining fiber also has been analyzed according to the experimental phenomena.