Aiming at insufficient research on polarization characteristics of infrared multi-coated targets, we propose a transmission model of infrared polarization characteristics of multi-coated targets. In the modeling of infrared polarization characteristics, most researchers focus on target surface roughness, ambient temperature, different target materials, and different kinds of coatings, but the comprehensive effect of these influencing factors and the multi-coated targets are seriously insufficient. In real life, the protection and camouflage effect of single-layer coatings on the targets is far worse than that of multi-layer coatings. Multi-layer coatings help homogenize the target during brushing, making the target surface smoother. Meanwhile, multi-layer coatings can independently design the coating type and thickness according to the coating effect of the target, which greatly expands the application range and functionality of the target coating. Therefore, we hope to propose a multi-coated infrared polarization transmission model. Based on this model, we can simulate the infrared polarization characteristics of multi-coated targets by simulating multi-coated targets. Then, the infrared radiation polarization characteristics of different materials under different coatings and coating quantities can be studied. This is of significance for the research on new infrared polarization stealth materials and infrared polarization of multi-coated targets.

The infrared polarization transmission model of multi-layer coatings has two main theoretical bases. First, for the infrared radiation model of the target, we divide the infrared radiation received by the detector into the intensity of the target spontaneous radiation and the intensity of the infrared radiation reflected by the target surface. The infrared radiation intensity of the target's spontaneous radiation is related to the target's emissivity. The higher target emissivity leads to higher spontaneous radiation intensity of the target. Similarly, the lower emissivity brings higher radiation intensity of the spontaneous radiation. This is why a large number of researchers try to reduce the spontaneous radiation intensity of the target by decreasing the target emissivity to achieve low target detectability as far as possible and then the infrared stealth effect. In infrared polarization, reducing the target emissivity is also a common method. Similarly, the ambient thermal radiation ratio has a strong influence on the infrared polarization characteristics of the target. By employing the control variable method, we study the target infrared linear polarization degree under the same ambient heat radiation ratio, different observation angles, and different coating layers. It is compared whether there are coatings to study the infrared linear polarization degree of spontaneous radiation of the target at different observation angles. In addition to the simulation, we adopt infrared linear polarization imaging to study the infrared polarization degree of the target in actual observation conditions.

Firstly, we analyze and derive the infrared radiation polarization model of the target according to the existing research on infrared polarization characteristics. Then, according to the geometric model hypothesis, the infrared polarization characteristics of the target under the multi-layer coatings are modeled, and the infrared polarization transmission model of the target under the multi-layer coating is built. By utilizing modern computer simulation technology, the infrared polarization characteristics of the target are simulated by controlling the influence factors such as the layer number in the model and the environmental heat radiation ratio. After the simulation, we verify the coatings with different layers through the experiment of design control variables. The simulation and experiment show that under the same coating quantity, the infrared linear polarization degree of the target increases first and then decreases with the rising observation angle. At the same observation angle, the infrared linear polarization degree of the target gradually decreases with the increasing layer number. This proves that under the experimental target and the coating, the layer number has a significant inhibition effect on the infrared linear polarization degree of the target, and with the increase in the layer number, the peak value of the linear polarization degree gradually moves to the smaller observation angle.

We analyze and calculate the reflected radiation, spontaneous radiation, and the interaction between reflection and spontaneous radiation of multi-coated targets. According to the analysis model of infrared polarization characteristics of target in a thermal radiation environment, the infrared polarization characteristics of multi-coated targets are studied. The results show that the coating number affects the polarization characteristics of both reflected radiation and spontaneous radiation, and the influence degree varies with the coating number. Then, we study the infrared polarization characteristics of multi-coated targets in a thermal radiation environment and discuss the effects of coating quantity and environmental thermal radiation ratio on infrared polarization characteristics. The experimental environment is set up to verify the simulation results, and the results show that the measured data has a good fit with the simulation data. Finally, the theoretical basis and influence of deviation between measured data and simulation data are analyzed. The experimental results show that the model is well fitted and the simulation model has good precision.