中文摘要：

针对大气背景是一个纵深背景而非一个平面，无法使用现有对比度计算公式计算的实际，基于红外焦平面探测器工作原理推导出了大气背景下探测器处辐射照度的对比度计算公式。通过对大气背景的红外辐射计算，并与报道的飞机红外辐射数据比较，应用对比度计算公式做分析可知：大气背景对探测的影响是必须考虑的；在3~5μm大气窗口的大气背景辐射很小，选择3~5μm大气窗口探测更容易发现目标；在8~12μm大气窗口内10μm附近的大气背景辐射较强，目标不易被探测。随着探测距离增加，探测器到无限远处的大气背景辐射亮度与探测器和目标之间的大气背景辐射亮度之差在减小，它会增大对比度，这是分析探测距离不可忽视的一个因素。

英文摘要：

On account of the present situation that the contrast formula can′t be used to calculate target and atmospheric background contrast, the irradiance contrast formula of target and atmospheric background was deduced based on the operating principle of focal plane detector. By calculating the atmospheric background infrared radiation, comparing it with the aircraft infrared radiation data report, and analyzing the contrast, results indicate that： the effect of atmospheric background on detection must be taken into consideration. The atmospheric infrared radiation between 3-5μm is very low, target in 3-5μm is easier to be detected. The atmospheric infrared radiation near 10μm is higher, and the target detection is more difficult. As the detection distance increases, the difference of radiance between the atmospheric path from detector to space and from detector to target decreases, and the contrast increases, which is an unneglectable factor to detection distance analysis.