A fuzzy environment such as smoke and dust can cause laser energy attenuation, signal-to-noise ratio reduction, and even false alarms caused by backscatter interference. It seriously affects the performance of the detection system and even makes the system unusable. In order to study the performance variation of pulse and frequency modulated continuous wave (FMCW) laser detection in fuzzy environment, this paper selects the ranging error and the equivalent target peak to backscatter peak ratio (TBR) as the evaluation index, and compares the performance of the two systems in fuzzy environment. The variation of detection performance under different degrees of fuzzy environment is also discussed. The results show that the detection performance of the two systems has different degrees of degradation in the fuzzy environment. In the case of different environmental visibility, the ranging error of the FMCW system is better than the pulse system. When the environmental visibility is high, the TBR of the pulse system is higher than the FMCW. As the visibility decreases, the TBR of the FMCW is gradually higher than the pulse. In comparison, the FMCW's detection performance is better than the pulse system in the case of low visibility, which is more obvious as visibility decreases.
Aerosols such as fog and dust interfere with the backscattering of laser proximity detection, which severely limits its application range. In order to achieve target recognition under aerosol interference conditions, the study of backscattering law is carried out. Based on Monte Carlo simulation method, the model of lidar interaction with aerosol is established, and the time domain characteristics of backscattering of laser radar are simulated. The peak intensity, signal delay and waveform broadening of backscattering echoes under different extinction coefficient (visibility), scattering coefficient and absorption coefficient were studied. The conclusions obtained from the study have certain reference significance for understanding the backscattering effect of aerosol particles, and also have certain significance for the subsequent research of anti-aerosol interference of laser detection.
Fog backscattering can cause false alarm for laser detection, especially multiple scattering of cloud and fog nearby the lidar. By setting up the receiving and transmitting field of view, a close range blind area can be generated to suppress the interference of near cloud and fog. As frequency modulated continuous wave ( FMCW ) laser detection has the advantage of anti-interference, the research on FMCW laser detection has been carried at at home and abroad, but the influence of detection baseline on the effect of FMCW laser detection Has not been studied. The fog and the target echo characteristics are simulated based on the Monte Carlo method. Then the echo spectrum and the calculation value of target distance under different baseline conditions are given. The influence of detection baselines on fog suppression ability of FMCW laser detection is analyzed. The simulation results show that the larger the distance between transmitting and receiving is, the The more prominent the peak of the intermediate frequency signal is, the less obvious the frequency aliasing is. The analysis results conform to the scattering law of cloud and fog on beam propagation, which can provide a basis for target recognition of laser detection and optimal design of Transmitting and receiving field parameters.