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在频率扫描干涉法绝对距离测量过程中,目标的运动会对测量结果引入误差,经推导发现运动误差与激光扫频终点频率以及扫频过程中的光程差位移量有关。前者可直接通过高精度波长计测量,对于后者,提出了外差干涉频分复用技术,设计了一种新的频率扫描距离测量干涉仪,可同时实现目标绝对距离和光程差位移量的测量,通过剔除与扫频终点频率和光程差位移量有关的误差相位偏移量后即可实现运动补偿。分析了该绝对距离测量系统的可行性和运动补偿的不确定度,并对测量精度进行仿真验证。结果表明该方法快速有效,在较快速运动目标测距时可实现对纳米量级光程差位移量的测量。在几十米距离范围内,当频率扫描范围达到100 GHz时该补偿方法引入的误差约为几十微米。
During the absolute distance measurement of frequency scanning interferometry, the movement of the target will introduce errors into the measurement results. It is deduced that the motion error is related to the frequency of the end point of the laser swept frequency and the optical path difference displacement in the sweep process. The former can be directly measured by the high-precision wavelength meter. For the latter, the heterodyne interference frequency division multiplexing technology is proposed and a new frequency scanning distance measuring interferometer is designed, which can achieve both the target absolute distance and the optical path difference displacement Measurement, motion compensation can be achieved by eliminating the error phase offset related to the end-of-sweep frequency and the optical path difference displacement. The feasibility of the absolute distance measurement system and the uncertainty of the motion compensation are analyzed. The accuracy of the measurement is verified by simulation. The results show that the proposed method is fast and effective, and can measure the optical distance difference of nanometer order when the target is moving faster. Within a few tens of meters, the error introduced by the compensation method is about tens of microns when the frequency sweep reaches 100 GHz.