Abstract: The Frequency-Modulated-Continuous-Wave laser ranging technology has the highest measurement accuracy in the common non-cooperative target laser ranging technology. The principle is to linearly modulate the optical frequency of the emitted laser. Calculate the distance of the target by measuring the frequency difference between the transmitted signal and the echo signal. Therefore, the accuracy of frequency measurement has a decisive influence on the accuracy of distance measurement. Due to the spectral leakage of the conventional FFT, the measurement accuracy is low, and the spectrum refinement method is fundamentally limited by the accuracy of the FFT. The all-phase FFT solves the problem of spectrum leakage and has the property of phase invariance. In this paper, the all-phase FFT method is applied to the frequency measurement of FMCW laser ranging. The frequency is measured by the time-shift phase difference method. The actual measured data is solved the MATLAB environment to calculate the target distance. Experiment shows that when the full-phase FFT is applied to the frequency modulation laser ranging digital signal processing, the ranging error is less than 0.3mm at a distance greater than 50 m, which achieves a good application effect.

Key words: Frequency-Modulated-Continuous-Wave, Laser ranging, All-phase FFT, Time shift phase difference method, Frequency measurement