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

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.