双频激光干涉仪中的数字相位计设计

Design of digital phasemeter on dual frequency laser interferometer system

基于Altera公司FPGA芯片,提出了一种基于双频激光干涉仪系统中数字相位计的实现方法。该相位计用于测量系统中被测信号和参考信号之间的相位差角度,间接测量激光干涉仪的光程差信息。被测信号经过光电接收器以及A/D模数转换成数字信号送到FPGA芯片中,与FPGA内建的查找表参考信号做正交相关法解调运算,得到一组X-Y值,再利用CORDIC算法计算arctan函数获取相位差,最后计算出干涉仪的光程差,算法的全过程使用FPGA硬件实现。实验结果表明,该相位计使双频激光干涉仪的相位差测量精度在0.01°以内。

Based on the Altera FPGA chip,a digital phasemeter on dual frequency laser interferometer system is introduced.The function of the phasemeter is to calculate measured signal and reference signal in order to get the phase difference,thus to get the interferometer optical path difference.The method is to use photoelectric converter and A/D convert device to get digital signal from the analog measured signal,and let the output do the multiply with look-up table in FPGA ROM based on the orthogonal correlation algorithm,then use CORDIC to get phase difference value,finally get the ultimate result.The experiment shows that the precision of digital phasemeter on dual frequency laser interferometer system is within 0.01°.