双波长荧光雷达探测大气生物气溶胶的性能分析

生物气溶胶在大气中扩散极易传播和发生各种流行疾病,也是生物武器投放的主要形式,实现生物气溶胶实时、远距离的探测显得尤为重要。构建了一台双波长荧光雷达用于大气中生物气溶胶的预警和识别。该雷达系统采用Nd∶YAG固体激光器作为激励光源,基频1 064nm、四倍频266nm作为工作波长。基于激光诱导荧光雷达探测原理,对红外波段的弹性散射信号和紫外波段诱导的荧光信号进行数值分析。结果显示,在探测误差小于10%的情况下,距离为1.0km时,单激光脉冲测量得到白天和夜晚细菌孢子的最小探测浓度分别为15 100个颗粒·L~(-1)和8 386个颗粒·L~(-1);当脉冲数累加到10 000时,白天和夜晚的细菌孢子最小探测浓度显著改善,分别为144个颗粒·L~(-1)和77个颗粒·L~(-1)。分析结果还表明,通过红外波段确定细菌孢子云团位置后,为了提高系统对细菌孢子的探测性能,可增加紫外激光脉冲数量,延长荧光信号采集时间。

Performance Analysis of Double Wavelength Fluorescence Lidar in Detecting Atmospheric Biological Aerosols

Biological aerosols widely spreading in the atmosphere will easily result in various epidemic diseases,meanwhile,bio-logical aerosol weapons pose a severe threat to the safety and security of military forces and civilians.It is critically important to remotely detect biological aerosols at real-time.In this work,a double-wavelength laser induced fluorescence lidar was construc-ted for atmospheric bacterial spores'identification and thus the early warning.The device employed a Nd:YAG laser operating at 1064 and 266 nm,with a repetition rate of 10 Hz.Based on lidar detection principle,a series of numerical simulations were performed to estimate the measurement range of the elastic scattering signals in the infrared band and the fluorescence signals in-duced by ultraviolet laser.In the ultraviolet band,the signals were analyzed with a spectrograph to evaluate the minimum con-centrations of bacterial spores at different pulses.With a relative error of less than 10%,theoretical analysis shows that,within a range of 1.0 km,the system is capable of identifying a minimum concentration of bacterial spores at about 15000 and 8400 particles·L-1 at daytime and nighttime with the single laser pulse excitation.With an integrated pulses of 10000,the detectable abilities of the fluorescence lidar greatly improves,identifying a minimum concentration of bacterial spores at 144 and 77 particles·L-1 at daytime and nighttime,respectively.In the lidar operation,when bacterial spores are located by the infrared e-lastic signals,one could actually extend the collected intervals in the fluorescence detection to improve the Signal-to-noise ratio, which may lose acceptable temporal resolution.