红外被动遥测系统应用于污染气体监测时, 其检测下限可用噪声等效柱浓度来衡量, 该参数是表征系统灵敏度的重要指标。 在污染气体红外辐射大气传输模型基础上, 推导出了噪声等效柱浓度的理论表达式, 表明其与系统噪声等效辐射通量密度、 背景及污染气团辐射亮温和目标气体的吸收系数相关。 以六氟化硫为示踪气体进行了实验, 计算并分析了系统在不同背景和污染气团辐射亮温环境下的检测下限, 并给出了系统噪声等效柱浓度的伪彩色分布图。 结果表明, 系统噪声等效柱浓度随背景和污染气团辐射亮温的温差增大而迅速减小, 温度差为30 K时检测下限降至10-2 ppm·m量级, 噪声等效柱浓度分布图的生成有助于判别系统在复杂背景下的检测下限变化范围。

NECL could be used to estimate the limit of detection of the infrared passive remote sensing system. It was an important indicator of the sensitivity of the system. The theoretical equation of the NECL according to the atmospheric infrared radiation transfer model showed that NECL related to NESR, the brightness temperature of background and pollution gas, and the absorption coefficient of pollution gas. The remote sensing of SF6 was done. The limit of detection of the system at the different brightness temperature of background and pollution gas could be calculated. False color image of NECL was given from the measured data. The results show that NECL decreases rapidly by increasing the difference in brightness temperature of the background and pollution gas, the value of NECL was down to 10-2 order of magnitude when the brightness temperature difference was equal to 30 K. False color image of NECL contributes to the discrimination of the limit of detection of the system in the complex background.