Influence of haze on pulse and FMCW laser ranging accuracy

Abstract

When the concentration of smog is large, the transmission process of laser signal will be greatly disturbed. In order to study the mechanism of this interference and reduce the ranging error, this paper focuses on the accuracy of smog and pulsed FMCW laser ranging. Firstly, based on the Mie scattering theory, the parameters such as scattering, extinction coefficient and asymmetry factor of haze under different conditions are calculated. Then Monte Carlo method is used to simulate the transmission process of pulse and FMCW laser signals. Finally, combined with ranging The principle analyzes the influence of haze on laser ranging accuracy. It is found that the smog will attenuate the amplitude of the pulsed laser signal, and as the transmission distance increases, this attenuation is significantly enhanced, reducing the signal-to-noise ratio of the ranging system. In addition, the delay and broadening of the pulse signal will also become larger due to the increase of the thickness of the haze, causing the waveform distortion of the echo signal, affecting the time discrimination accuracy of the pulse ranging, thereby affecting the ranging accuracy. The amplitude of the intermediate frequency signal of the FMCW laser ranging also decreases with the increase of the extinction coefficient. The amplitude of the echo signal decreases with increasing frequency because the attenuation of the high frequency signal by the haze is more pronounced. At the same time, the increase of the haze extinction coefficient will also reduce the signal-to-noise ratio of the echo signal, affecting the accuracy of the FMCW ranging.