基于等光频细分重采样的调频干涉测距方法

Laser ranging method of frequency modulation interference based on equal optical frequency subdivision resampling

为了解决调频连续波(FMCW)激光器调制非线性导致的测量信号频谱展宽降低激光干涉测距精度的问题,采用一种基于等光频细分重采样的调频干涉测距方法,进行了理论分析和实验验证,获得了双光路测距系统对不同位置目标信号等光频细分重采样后的波形数据,并进行了频谱分析。结果表明,通过等光频细分重采样的方法,使用细分后的时钟信号点对距离大于辅助干涉光路光程差的目标测量信号进行重采样,消除了激光器的调制非线性的影响,并且避免了采样点数不足引起信号失真的问题;在4.3m测量范围内,等光频细分重采样测距系统与激光干涉仪相比最大残余误差不超过±18.46μm,最大测量标准差为23.39μm;该方法使用的辅助干涉光路光程差很短,受环境的影响较小,可以获得稳定的时钟信号,并且可以减少双光路FMCW测距系统的体积与成本。该研究为长距离、高精度调频连续波测量提供了实用参考。

In order to solve the problem that modulation nonlinearity of frequency modulated continuous wave(FMCW)laser leads to the broadening of measurement signal spectrum and the reduction of laser interferometric ranging accuracy,frequency modulated interferometry ranging method based on equal optical frequency subdivision and resampling was adopted.Theoretical analysis and experimental verification were carried out.Waveform data of dual optical path ranging system after equal optical frequency subdivision and resampling of target signals at different positions were obtained.Spectrum analysis was also carried out.The results show that,by means of equal optical frequency subdivision and resampling,the subdivided clock signal points are used to resample the target measurement signal whose distance is greater than optical path difference of auxiliary interferometer.The influence of modulation nonlinearity of laser is eliminated.The problem of signal distortion caused by insufficient sampling points is avoided.Within the measurement range of 4.3m,comparing with laser interferometer,the maximum residual error of equal optical frequency subdivision resampling ranging system does not exceed±18.46μm.The maximum standard deviation is 23.39μm.Optical path difference of auxiliary interferometer used in this method is very short.It is less affected by the environment.A stable clock signal can be obtained.It can also reduce the volume and cost of dual optical path FMCW ranging system.This study provides practical reference for long-distance and high-precision FMCW measurement.