激光相位分立调制和多波长干涉相位同步解调的绝对距离测量方法研究

High-precision, fast measurement of a wide range of absolute distances is the basis for large equipment manufacturing and large-scale metrology. The measurement accuracy of the laser frequency-sweeping interferometry is limited by the mode hope free tuning range of frequency and the multi-wavelength interferometry need to construct multiple synthetic wavelengths to expand the non-ambiguity range, which makes the measurement system complex. Though the combination of frequency-sweeping interferometry and multi-wavelength interferometry can compensate with each other for the measurement range and accuracy, the measurements of the two methods are executed in turn at present, which makes slow measurement and poor anti-interference ability. In this project, an absolute distance measurement method with laser phase independent modulation and interferometric phase synchronous demodulation of multiple wavelengths is proposed. Synchronous measurement of frequency-sweeping interferometry that used for coarse measurement and multi-wavelength interferometry that used for fine measurement is able to realize to improve the speed and anti-interference ability of large range absolute distance measurement. Thus the problems that the accuracy of frequency-sweeping interferometry is limited by the tuning range of frequency and the expansion of measurement range of multi-wavelength interferometry requires multiple synthesis wavelengths are able to be solved. An interference signal processing method based on frequency division multiplexing and PGC demodulation is proposed to solve the problem of synchronous phase demodulation for frequency-sweeping interferometry and multi-wavelength interferometry and improve the measurement accuracy. Related absolute distance measurement device is able to build to verify the feasibility of the proposed measurement method by experiments, and the measurement uncertainty analysis and the performance evaluation are carried out.

大范围绝对距离的高精度、快速测量是大型装备制造和大尺寸计量的基础。激光频率扫描干涉测量方法受无跳模频率扫描范围限制，测量精度低；多波长干涉法因扩大非模糊量程需构建多级合成波长，测量系统复杂；将频率扫描与多波长干涉相结合虽可实现测量范围和精度相互弥补，但目前两者相结合的方法因分时测量导致测量速度慢、抗干扰能力差。本项目提出一种激光相位分立调制和多波长干涉相位同步解调的绝对距离测量方法，拟实现频率扫描干涉法“粗测”和多波长干涉法“精测”的同步测量，以提高大范围绝对距离的测量速度和抗干扰能力，解决频率扫描干涉测量精度受限于频率扫描范围、多波长干涉法扩大测量范围需构建多级合成波长的技术问题；提出一种基于频分复用PGC解调的干涉信号处理方法，解决频率扫描和多波长干涉相位的同步解调问题，提高绝对距离测量精度；搭建相关绝对距离测量装置，实验验证所提出测量方法的可行性，并进行测量不确定度分析和性能评估。

本项目针对高端装备制造和大尺寸计量等领域对大范围、高精度绝对距离测量技术的需求，开展了激光相位分立调制与多波长干涉相位同步解调的绝对距离测量相关研究工作。研究了激光相位分立调制的多波长干涉相位同步解调方法，采用电光相位调制器对多波长光源分别施加不同频率的正弦相位调制，使不同激光波长对应的干涉相位分别加载至不同高频调制信号的边带上，通过解调各载波信号携带的相位信息，实现了多波长干涉相位的同步解调；研究了基于参考干涉仪的频率扫描干涉绝对距离测量方法，对激光频率进行大范围周期性连续扫描，提高了绝对距离测量速度和精度，采用固定波长的激光干涉仪实时监测和补偿测量干涉仪和参考干涉仪在频率扫描过程中的相位变化，进一步减小测量误差；研究了基于相位生成载波（PGC）解调的频分复用多波长干涉信号处理方法，提出了对载波相位延迟和相位调制深度敏感的PGC-DCDM解调方法，提高了相位解调精度；构建了绝对距离测量系统，通过稳定性实验、不同长度的绝对距离测量实验、与增量式干涉仪的对比实验、动态距离测量实验等验证了绝对距离测量方法的有效性，5m测量范围内绝对距离相对测量不确定度达10-6，测量结果的相对稳定性达10-7，并验证了该方法在动态距离测量中的可行性，可应用于大型精密设备的精确定位、安装和变形检测等场景，对精密测量领域的发展具有重要的意义。