双纵模双频激光干涉仪的非线性对测量精度的影响

Influence of nonlinearity on measuring precision of dualfrequency laser interferometer with two longitudinal modes

对具有特殊后续电信号处理系统的双纵模双频激光干涉仪的非线性误差进行了研究。根据理论分析推导出了存在非线性时输出信号的表达式,并据此给出了非线性误差的表现形式是使混频输出信号产生漂移起伏,主要影响因素是偏振分光镜分光偏振度及光路调整理想程度。根据分光偏振度可计算信号最大漂移幅度及其带来的测量误差,计算出的漂移幅度值与实际观测值相近,该值可作为判断光路调整精度的一个标准,也是确定后续信号处理环节(细分辨向计数)中最大细分数的依据。

The nonlinearity error of the dual-frequency laser interferometer with two longitudinal modes and special subsequent electrical signal processing system was studied. The expressions for the output signal pair were desired based on the theoretical analysis when the nonlinearity exised. From the above it was given that the nonlinearity makes the frequency-mixing output signals shift and undulate, and its main factors are the perfection degree of the optical system adjustment and the polarization splitting degree of the polanzation beam splitter. The maximum signal shift amplitude was close to that observed on oscillograph and it could be used to estimate the perfection degree of the optical system adjustment and determine the maximum interpolation number in the subsequent signal processing stage.