精测尺自适应匹配的光纤外差超高频激光相位法测距关键技术研究

The high-accuracy phase-shift laser range finder is attractive for various application fields, such as robot navigation, three-dimensional imaging, and profile measurements of large-scale structures. At present, the modulation frequency is tens of MHz, and the measurement accuracy is in the magnitude of millimeters, which limits the application of the phase-shift laser range finder. This project proposes an ultra-high frequency phase-shift laser range finder based on adaptive match of fine wavelength and fiber heterodyne detection. The main research work includes: investigate the approach to increase the modulation frequency from tens of MHz to about 15GHz; reveal the mechanism of the crosstalk of the ultra-high frequencies and its influence on the measurement results, and investigate the fine wavelength’s adaptive matched method to reduce the measurement error; investigate the rule of the phase delay of APD, and establish digital circuit to reduce the variation of phase delay by adjusting the DC bias of APD based on the measurement feedback; a fast high precision digital frequency correction scheme is proposed to suppress the influence of photoelectric noise and frequency shift on the phase difference, and an integral-cycle sampling phase-shift correlation method is proposed to estimate the phase difference between two sinusoidal signals with identical frequency; establish the platform of the ultra-high frequency phase-shift laser range finder based on adaptive match of fine wavelength and fiber heterodyne detection, and carry out the testing experiments. It is hopeful that the total uncertainty of the phase difference is less than 0.36 degrees, which can achieve a measurement accuracy of 0.01mm.

高精度激光相位测距在机器人导航、三维成像、大尺寸零件形貌测量等领域有着广泛的应用需求。目前，激光相位测距的调制频率在几十兆赫兹左右，导致测距精度在毫米量级，在很大程度上限制了其应用。为此，本项目提出了一种精测尺自适应匹配的光纤外差超高频激光相位测距方法，并研究基于此项改进引起的关键技术问题。主要研究内容有：研究并实现将调制频率由几十兆赫兹提高到15GHz的方法；研究超高频电信号串扰机理及其对测距误差的影响规律，探索精测尺自适应匹配方法，减少测距周期误差；揭示APD相位延迟规律，建立基于测量反馈的相位延迟补偿电路，消除返回光强变化引起的APD相位延迟波动；研究噪声条件下面向整周期采样的频率校正方法及相位差计算算法；构建精测尺自适应匹配的光纤外差超高频激光相位法测距平台并开展实验研究。本项目的实施，将实现相位差的总不确定度小于0.36°，从而在200米测距范围内达到0.01mm的测距精度。

高精度激光相位测距在机器人导航、三维成像、大尺寸零件形貌测量等领域有着广泛的应用需求。目前，激光相位测距的调制频率在几十兆赫兹左右，导致测距精度在毫米量级，在很大程度上限制了其应用。为此，本项目提出了一种精测尺自适应匹配的光纤外差超高频激光相位测距方法，并研究基于此项改进引起的关键技术问题。首先，本项目将相位法测距的调制频率提高到15GHz左右，从而将测距分辨率提高到微米级，并搭建了实验样机。改变测量系统结构，减少了传统混频方法产生的谐波和非线性失真；采用光纤外差探测方法，减少了探测器相位延迟波动。其次，从理论上分析了测距周期误差产生的机理，研究了自适应匹配精测尺减少测距周期误差的方法。研究表明，强度调制处的高频正弦信号串扰到光电探测端，导致了误差周期为调制信号半波长的系统误差。采用自适应匹配精测尺的方法，基本消除了相位差周期误差。第三，研究了APD相位延迟规律，根据APD相位延迟补偿数据，通过测量反馈电路在最佳偏压附近调节偏压，稳定APD的相位延迟。最后，对变时滞高阶微分方程的振动性进行了基础研究，并研究了实际噪声条件下非整周期采样的相位差算法。在估计相位差的方法中引入了希尔伯特黄变换，消除了非整周期采样引起的误差。标定实验中，相位差总误差在±0.15°内，在相对折射率和相对频率误差小于10ppb时，在200m范围内的测距偏差小于8.17μm。该项目完成了预期研究目标，针对光纤外差超高频激光相位法测距技术开展的理论和实验研究，具有重要的科学意义和工程应用价值。