激光圆偏振干涉纳米位移测量信号处理方法

Signal Processing Method of Laser Circular Polarization Interference Nanometer Displacement Measurement

介绍激光圆偏振干涉纳米位移测量系统的光路结构，针对A／D误差和直流噪声引入的位移误差，提出了基于正余弦信号切换的干涉条纹处理方法，以提高测量精度。设计基于FPGA和DSP架构的激光圆偏振干涉纳米位移测量系统，其中FPGA主要用于信号的采集、大数计数及与上位机通讯，DSP主要用于小数计算。位移实验结果表明：在0～7μm范围内，步长为100nm的测量结果其线性拟合相关系数为0．9836，标准差为1．88nm；在0～15μm范围内步长为1μm的测量结果其线性拟相关系数为0．9992，标准差为2．96nm。验证了所提出的干涉条纹处理方法和信号处理系统能够实现纳米级位移测量精度的要求。

This paper introduces the light path structure of laser circular polarization interference nanometer displacement measuring system of puts forward interference fringe processing method based on sine and cosine signal switching in allusion to A/D error and displacement error introduced by dc noise so as to improve the measuring accuracy; designs laser circular polarization interference nanometer displacement measuring system based on FPGA and DSP architecture. FPGA is mainly used for signal acquisition, large number counting and communication with upper computer. DSP is mainly used for small number calculation. The result of displacement experiment shows that, when the step length is 100 nm, within the scope of 0-7 μm, the correlation coefficient of linear fitting of the measuring result is 0. 983 6 and standard deviation is 1.88 nm; when the step length is 1 μm, within the scope of 0-15 μm, the correlation coefficient of linear fitting of the measuring result is 0. 999 2 and standard deviation is 2.96 nm. It verifies that interference fringe processing method proposed and signal processing system can achieve the requirement of nanoscale displacement measuring accuracy.