针对激光频率扫描干涉(FSI)测距系统中激光器输出光频率非线性对测量精度的影响,提出了一种基于非平稳信号阶次跟踪的方法。从频域的角度分析了FSI测距系统中影响测量精度的主要因素。通过检测法布里-珀罗标准具的透射信号,实现对光频率的快速间接测量。利用最小二乘的方法对光频率进行线性拟合,实现对光频率变化率的修正。通过多项式拟合的方法确定光频率的时间-频率数学表达式,构造等频率的间隔点对其逆向插值,获得对应的时间序列。对采样的干涉信号在时间序列处正向插值,重构等频率间隔采样的干涉信号,对重构的干涉信号进行频谱分析,最终得到非平稳干涉信号的干涉频率。结果表明,在不限制待测距离的条件下,利用阶次跟踪的方法,可以有效抑制激光器输出光频率非线性的影响,FSI测距系统的测量精度得到显著提高。在1000 mm的测量范围内,测量结果的空间分辨率提高了36倍以上。 Aiming at the influence of laser output optical frequency nonlinearity on measurement accuracy in laser frequency scanning interference (FSI) ranging system, a non-stationary signal order tracking method is proposed. From the perspective of frequency domain, the main factors influencing the measurement accuracy in FSI ranging system are analyzed. By measuring the Fabry-Perot etalon transmission signal, rapid and indirect measurement of light frequency is achieved. The least squares method is used to fit the optical frequency linearly to correct the rate of change of optical frequency. The polynomial fitting method is used to determine the time-frequency mathematical expression of the optical frequency. The frequency interval points are constructed and interpolated inversely to obtain the corresponding time series. The interference signals sampled at the time series are interpolated and reconstructed, and the interference signals sampled at the frequency intervals are interpolated. The spectrums of the reconstructed interference signals are analyzed, and finally the interference frequency of the non-stationary interference signals is obtained. The results show that the order tracking method can effectively suppress the nonlinearity of the output optical frequency of the laser without limiting the distance to be measured, and the measurement accuracy of the FSI ranging system is significantly improved. In the 1000 mm measurement range, the spatial resolution of the measurement results increased more than 36 times.