The Weak Signal Detection Based On Lidar Visibility Meter

In bad weather conditions, the accurate detection of visibility plays a decisive part on the safe taking off and landing of aircraft. However, when working in high light condition, the lidar visibility meter is susceptible to background noise which mainly comes from the sun, the sky light radiation and internal thermal radiation. Moreover, the background noise varies according to the location, time and weather condition.The system which the paper studies about is based on the backscattering theory. Diode Pumped Solid State Laser(DPSSL) with low pulse energy and high pulse repeat frequency while Avalanche Photo Diode(APD) detector with the characteristics of low noise and high quanta efficiency have been adopted, which ensure the precision of system; Specially, the meter adopts embedded computer as the corefor system controlling and dataprocessing, and realizes thetiming control of system.To deal with the fact of echo signal-to-noise ratio degrading when faced with the strong background light, through the system improving and signal processing,a new method which combines the real-time background noise compensation with the moving average method using threshold segmentation is adopted to process the signal, which greatly eliminating the background noise in echo signal and improving the signal-to-noise ratio and then improving the precision of subsequent visibility inversion.Finally, the accuracy and effectiveness of this weak signal detection method is verified by the simulation and field comparativetests inwhich theoverall visibility detection erroris less than20%.