The Mechanism Study Of The Back-scattering Effect To The Active Detecting

The target detection mode can be divided into passive detection and active detection according to illuminating the object whether or not. The passive detection detects targets rely on the target radiating light itself or reflecting the surrounding environment light(such as the sun light) which resulting its good concealment. But the passive detecting has strong dependence on the environment light, so it may not be able to identify and tracking the target effectively in the dark circumstances or poor weather conditions.Active detection is a detecting method that gives the active illumination on the target and receiving, imaging of target reflection light. Due to that it enhances target echo intensity, and the detection is not dependent on the target of ambient reflecting light, therefore active detection has the unique advantage in the field of remote small dim target detection and space target detection. in active detection process, when the probe beam of the laser device transmits in the atmosphere the scattering of atmospheric molecules and atmospheric aerosol particles is multi-directional. The atmospheric scattering in the backwards aspect would be transferred inversely and get into the receiving system, causing serious noise interferences to the detectors, and if the back-scattering was too strong, it would even make the detectors saturation, resulting that the detection system could not work properly. Therefore, it is necessary to analyze the back-scattering in the active detecting process and summary the method to avoid back-scattering.This article mainly investigates the active detection system and the impact of back-scattering effect to the detection ability. First of all, the article introduces the active detection system and the detection process, and analyzes factors that influenced the detection, including atmospheric disturbances, laser power and divergence, angle parameters of detector etc.. Echo power of diffuse target and “cat eye” target is deducted simultaneously. Then the paper carries on the theoretical analysis and derivation of the total scattering power received by the detector and the back-scattering power received by every single pixel and gets their specific expression according to a physical model of the atmosphere back-scattering in active detecting system established before. Then the paper takes the ratio of target echo power and back-scattering power as the coefficient to measure the Interference ability of back-scattering, and does simulation to calculate some related factors, which results show that most of the back-scattering received by the system is scattering from atmospheric in short distance, and the increase of laser and detector distance can greatly reduce the interference of back-scattering on the detection in the same conditions. Then two system level active detecting experiments is designed and implemented to verify the theoretical analysis and get the result of the reliability of the theoretical analysis. Finally, the paper makes the discussion and analysis of the feasibility scheme of applying active detection to space target detection, and calculates the theoretical detection distance of imaging detec-tion and non-imaging detection using the typical system parameters in current technology conditions.