The influence of environmental radiation on the infrared characteristics of low emissivity surface

Low emissivity coatings or thin film materials are currently the main technical means for achieving infrared stealth. Due to the high reflectivity of low emissivity surfaces, environmental radiation such as solar radiation and ground radiation may have a significant impact on the effective infrared radiation of low emissivity surfaces. In response to the current research on low emissivity surface infrared radiation mainly limited to its suppression of self radiation, and the lack of information on the impact of environmental radiation on its effective radiation, starting from establishing a general infrared feature model that includes self emitted reflected environmental radiation, the focus is on deriving the effects of solar radiation and ground radiation on low emissivity surfaces in two atmospheric infrared windows 3-5 μm-band and 8-14 μm. The influence model of effective infrared radiation in the 3-5 μm-band has been calculated and experimentally verified. The results indicate that solar radiation and ground radiation have an impact on low emissivity materials in the mid infrared region of 3-5 μm-band and far Infrared 8-14 μm. The impact of effective infrared radiation in the two bands is different and is related to factors such as ground temperature, the angle between the target surface and the ground, the atmospheric transmittance of solar radiation, and the angle of solar incidence. In general, reducing the emissivity of a surface can reduce its effective infrared radiation, which is beneficial for achieving infrared stealth. However, there are two common exceptions that make using low emissivity materials not a good way to achieve infrared stealth. One is that when the surface temperature of the target is below 60 °C, due to the influence of solar radiation, reducing reflectivity in the 3-5 μmband may actually enhance its effective radiation. That is a challenge to the targets in the background of low and normal temperatures during a clear day range to realize infrared stealth in the 3-5 μm-band. The second exception is that due to the influence of ground radiation, when the temperature of the aircraft's bottom surface is lower than the ground temperature, reducing reflectivity in the 8-14 μm-band may actually enhance its effective radiation. That is a challenge to aircraft having a bottom surface to realize Infrared stealth in the 8-14μm-band. In both cases, adopting temperature control and cooling measures may be the only way to reduce its effective radiation radiation and achieve infrared stealth. The relevant conclusions can provide important references for infrared detection and target infrared stealth design.