机床滚转角高精度测量中的频偏现象研究

Analysis of Frequency Excursion in High-Precision Measurement of Machine Tool's Roll Angle

为降低正交偏振光外差干涉相位法中相位差的波动幅度,提高滚转角的测量精度,利用琼斯矩阵法,建立了测量光路和参考光路数学模型。新模型在原有模型的基础上考虑了双频激光器频差的不稳定性和光电探测器响应时间的差异性的影响,推导出测量信号和参考信号之间的频率偏差(简称频偏)会对相位差波动产生较大的影响。在此基础上,给出频偏是由双频激光器频差的不稳定性和光电探测器响应时间的差异性综合作用产生的,并且量化了频偏对于滚转角测量精度的影响。根据该模型,提出通过提高双频激光器的稳频精度和降低光电探测器的响应时间的差异性的方法来降低频偏,进而降低相位差波动。实验结果表明:在降低光电探测器响应时间的差异性后,相位差实际波动幅度由0.7°下降到0.1°左右,测量误差降低了85.7%,证明了分析模型有效可行。

In order to decrease the phase-different fluctuation and increase the roll angle measuring accuracy in extrapolation interference method, a new mathematical model of measurement optical path and reference optical path was established through Jones matrix method. The model takes the frequency unsteadiness of two-frequency laser and the difference of photo-detector＇s response time into consideration based on the existing model and deduces that the frequency difference between the reference signal and measuring signal （frequency excursion） is the main cause of phase-different fluctuation. So it can be concluded that the frequency excursion is caused by the frequency unsteadiness of two-frequency laser and the difference of photo-detector＇s response time. The effect of frequency excursion on the roll angle measuring accuracy is also calculated. Based on the model, this paper presents a method of increasing two- frequency laser frequency stabilization and decreasing the difference of photo-detector＇s response time to eliminate Dhase-different fluctuation. Experimental results indicated that after decreasing the difference of photo-detector＇ s response time, the range of phase fluctuation was decreased from 7° to 1° and the roll angle measuring error decreased by 85.7%, which proves that the new model is feasible.