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为了减小激光外差干涉纳米测量的非线性误差,必须明确偏振分光镜(PBS)分光性能非理想对非线性误差的影响机制.推导出非理想情况下偏振分光镜透射率和反射率的激光外差干涉非线性误差模型,建立了偏振分光镜分光性能非理想对非线性误差二次谐波的影响模型.仿真结果表明,偏振分光镜的透射率和反射率非理想对非线性误差的影响为一次谐波,且偏振分光镜分光性能越差,其对非线性误差的影响也越大.在偏振分光镜反射率为0.90的情况下,偏振分光镜透射率从1减小到0.90时,非线性误差由0.62 nm增大到1.24 nm.当存在偏振分光镜旋转角度误差时,偏振分光镜分光性能非理想引起的非线性误差不增加二次谐波分量,但增大了非线性误差一次谐波分量,严重影响非线性误差的大小.当偏振分光镜旋转角度误差为5°时,偏振分光镜透射率从1变为0.90,非线性误差从0.39 nm增大到1.41 nm.
In order to reduce the nonlinear error of the laser heterodyne interference nanometer measurement, the mechanism of the non-ideal linear polarization error of the polarization beam splitter (PBS) must be clarified.It is deduced that the transmittance and reflectance of the laser beam in the non-ideal case Heterodyne interference nonlinearity error model, the influence model of polarization beam splitter non-ideal on nonlinear second harmonic is established.The simulation results show that the influence of non-ideal transmittance and reflectance of polarization beam splitter on nonlinear error Is the first harmonic wave, and the worse the polarization performance of the polarization beam splitter is, the greater its influence on the nonlinearity error is. When the polarization beam splitter has a reflectivity of 0.90 and the transmittance of the polarization beam splitter decreases from 1 to 0.90, The nonlinear error increases from 0.62 nm to 1.24 nm. The non-linear error caused by the non-ideal polarization performance of the polarizing beam splitter does not increase the second harmonic component when the rotation angle error of the polarizing beam splitter exists, but increases the nonlinear error once Harmonic component, seriously affecting the size of nonlinear error.When the rotation angle error of the polarization beam splitter is 5 °, the transmittance of the polarization beam splitter changes from 1 to 0.90, and the nonlinearity error increases from 0.39 nm 1.41 nm.