Research On The Beam-splitting Quality Detection For Multi-axis Differential Interferometer

In recent years, the dual-frequency laser interferometer progressed towards the direction of miniaturization, modular, passivity, multi-axis and so on. The demand for high quality multi-axis differential interferometer is increasingly urgent. Although differential interferometer avoids some assembly errors of interference measurement system, there are still nonlinear errors in measurement that restricted the accuracy of dual interferometer system.In this paper, the author analyzed and summarized the nonlinear interferometric measurement errors during multi-axis interferometric measurement first. Then, the advantages and disadvantages about the traditional measurement method and the new measurement method to measure the beam splitter were compared. Next, a measurement scheme was proposed to measure the beam-splitting quality parameter of multi-axis differential interferometer. Finally, the author designed the photoelectric conversion circuit and the data acquisition circuit successfully detected the beam-splitting quality parameters.The main research content of the thesis involves:Firstly, a complete measurement scheme about multi-axis differential interferometer was proposed. In the measurement scheme data were gotten by detecting the change of output light intensity while rotating the Glen Thompson prism. In the theory model, the author analyzed the influence of optical devices in interferometer system to light polarization and established a theory model that contains all the parameters include the beam-splitting quality parameters of multi-axis differential interferometer, the placement tolerance of multi-axis differential interferometer, and the polarization state of the laser source simultaneously. Finally, paper used the data processing method to indirectly calculate these parameters.Secondly, the author completed the design of measurement system which is to detect the beam-splitting quality of multi-axis differential interferometer. In this section the highly accurate and large bandwidth photoelectric conversion circuit was designed. Then, the design of data acquisition hardware circuit based on a combination of FPGA and DSP was completed. Finally, the author designed PC control program by Lab VIEW and data processing based on MATLAB which realize the parameters calculation.Thirdly, various modules of the measurement system were tested and the errors were compensated by software. Finally, the author detected parameters which response to the quality of multi-axis differential interferometer. The results showed that the equivalent energy transmittance is 97.74%±0.07%, the equivalent energy reflectance is 98.87%±0.08%, light non-orthogonal angle is 0.506°±0.050°, elliptical polarization angle is-0.225°±0.007° and 0.440°±0.008° and the position error is-0.297°±0.031°.