# Infrared Imaging System with a Local Polarization Channel for Target Detection
## 4 Imaging Simulation Results  
### Local Polarization Imaging  
To simultaneously demonstrate the 2\(\times\) local magnification and local polarization imaging results, both the target scene model shown in Figure 4 and the imaging system model shown in Figure 2 are employed. As shown in Figure 4a, the target scene model was composed of an F-type light source array, wherein several capital letters \"F\" of the same size in different locations represented the different FOIs in different areas. An extra polarizer or quarter-wave plate was installed next to the F-type light source array to simulate the polarization characteristics of the target. Figure 3: Spot diagrams and MTF plots of the entire FOV and Areas 1, 2, and 3. (**a**) Spot diagram and (**b**) MTF plot of the peripheral channel. (**c**) Spot diagram and (**d**) MTF plot of Area 1. (**e**) Spot diagram and (**f**) MTF plot of Area 2. (**g**) Spot diagram and (**h**) MTF plot of Area 3. First, the target scene with linear polarization FOI was simulated. A linear polarizer was placed next to the center \"F\" to simulate the horizontal linear polarization characteristics of the FOI in the target scene, as shown in Figure 4b; essentially, Area 1 was horizontally polarized. We can obtain four images on the detector with polarization information for the four polarization states of 0\({}^{\circ}\), 45\({}^{\circ}\), 90\({}^{\circ}\), and 135\({}^{\circ}\) by rotating the micro-polarizer in the model four times. As a comparison, the imaging simulation of the infrared imaging system without the microlens group was carried out. The image is shown in Figure 5. The microlens group is a crucial part of the optical system to achieve local magnification and polarization imaging. Without it, the function of the 2\(\times\) local magnification and local polarization imaging is unachievable. Thus, the light intensity of every \"F\" in the image plane was equal. The central \"F\" was made as Area 1. When the polarization orientation of the micro-polarizer in the imaging system was 0\({}^{\circ}\), which was parallel to the polarization state of the central \"F\" in the target scene, the light intensity of the central \"F\" in the image plane was equal to that of the other letters, as shown in Figure 6a. When the polarization orientations of the micro polarizer were 45\({}^{\circ}\) and 135\({}^{\circ}\), the light intensity of the central \"F\" in the image plane was lower than that of the other letters, as shown in Figure 6b,d, respectively. When the polarization orientation of the micro polarizer in the imaging system was 90\({}^{\circ}\), which was perpendicular to the polarization state of the central \"F\" in the target scene, the light intensity of the central \"F\" in the image plane was zero, as shown in Figure 6c. We acquired the polarization images of the target scene by combining Equations (1), (2), and (4), as shown in Figure 7. Figure 7a shows the Stokes vector element I, which was the total intensity of the light. As shown in Figure 7a, the \"F\" in central FOI takes up 46 pixels in the Y direction, and in contrast, the \"F\"s in peripheral FOV take up 46 pixels in the Y direction. That is, the magnification of the central \"F\" is twice that of the other \"F\"s, which demonstrates the 2\(\times\) local magnification of the imaging system. Figure 7b shows the Stokes vector element Q, and Figure 7c shows the AOP plot. Those two figures show that  
Figure 4: Target scene model. (**a**) In X–Y plane. (**b**) In Y–Z plane. Figure 5: The imaging simulation of the infrared imaging system without the microlens group. only the enlarged central \"F\" is successfully imaged owing to the polarized property of the central \"F\" and the unpolarized property of the other \"F\"s. Thus, for the target with linear polarization characteristics, our system simultaneously captured images in the wide FOV and the local polarization images in the FOI. Subsequently, the target scene was analyzed with an elliptical polarization FOI.