Grant W B, Brothers A M, Bogan J R
Appl Opt. 1988 May 15;27(10):1934-8. doi: 10.1364/AO.27.001934.
This paper presents experimental results using an atmospheric backscatter dual CO(2) laser differential absorption lidar (DIAL). It is shown that DIAL signals can be averaged to obtain an N(-(1/2)) dependence decrease in the standard deviation of the ratio of backscattered returns from two lasers, where N is the number of DIAL signals averaged, and that such a lidar system can make measurements of gas concentrations with a precision of 0.7% in absorptance over 75 m in a short measurement time when the signal strength is high-Factors that eventually limit the rate of improvement in the SNR, such as changes in the ratio of the absorption and/or backscatter at the two laser frequencies and background noise are discussed. In addition, it is noted that DIAL measurements made using hard-target backscatter often show departures from N((1/2)) dependence improvement in the standard deviation, because they are further limited by the combined effects of atmospheric turbulence and speckle, since the relative reproducibility of the speckle pattern on the receiver gives rise to correlations of the lidar signals.
本文介绍了使用大气后向散射双二氧化碳激光差分吸收激光雷达（DIAL）的实验结果。结果表明，可以对DIAL信号进行平均，以使来自两台激光器的后向散射回波比率的标准偏差呈现N^(-1/2)依赖性下降，其中N是平均的DIAL信号数量，并且当信号强度较高时，这种激光雷达系统能够在短测量时间内，在75米的距离上以0.7%的吸收率精度进行气体浓度测量。文中讨论了最终限制信噪比提升速率的因素，例如两个激光频率处吸收和/或后向散射比率的变化以及背景噪声。此外，还指出使用硬目标后向散射进行的DIAL测量通常显示标准偏差偏离N^(1/2)依赖性改善，因为它们受到大气湍流和散斑综合效应的进一步限制，这是由于接收器上散斑图案的相对再现性导致激光雷达信号产生相关性。
