Precision and repeatability improvement in frequency-modulated continuous-wave velocity measurement based on the splitting of beat frequency signals

The basic principle of frequency-modulated continuous-wave lidars is to measure the velocity of a moving object through the Doppler frequency shift phenomenon. However, the vibration generated by the moving object will cause the spectrum to broaden and the precision and repeatability of speed measurement to decrease. In this paper, we propose a speed measurement method based on (HCN)-C-13-N-14 gas cell absorption peak splitting the sweep signal of a large bandwidth triangular wave modulated frequency laser. This method obtains the speed of a continuously moving target by re-splicing an accurately-split frequency sweep signal, which effectively solves the problem of simultaneous processing of excessive amounts of data when measuring the speed of a continuously moving target. At the same time, the (HCN)-C-13-N-14 gas cell absorbs the spectra of specific wavelengths, which reduces the phase delay of the beat signal corresponding to the up-and down-scanning, thus reducing the signal spectrum broadening caused by frequency deviation, and improving the speed measurement resolution and range effectively. The experimental results show that for speeds of up to 30mm/s, the mean error was less than 231 mu m/s and the mean standard deviation was less than 61 mu m/s. (C) 2021 Optical Society of America under the terms of the OSA Open Access Publishing Agreement