## 4 PSIFTIS Imaging Experiment Results and Data Processing
### Polarization Spectral Reconstruction  
In order to obtain the polarization spectrum and image information of the target, a carbon-silicon rod light source was used as the active light source. Narrow-band filters with central wavelengths of 3800 nm (2644.64 cm\({}^{-1}\)), 3970 nm (2522.93 cm\({}^{-1}\)), and 4720 nm (2111.72 cm\({}^{-1}\)) were selected respectively, and the theoretical spectral information of  
Figure 8: Image registration: (**a**) SUSAN corner detection results of two image units; (**b**) SIFT feature matching results of two image units; (**c**) polarization interference data cube set. Figure 7: Image segmentation method based on convolution kernel traversal and Canny edge detection: (**a**) target polarization interference image array; (**b**) convolution kernel traversal image result; (**c**) Canny edge detection image result; (**d**) final edge detection image result. the narrow-band filters was used to verify the spectral information of the target. The experimental results were displayed in the 0\({}^{\circ}\) polarization channel, and the wavenumber calibration methods of other polarization channels were the same. The theoretical spectra of each filter group in the 0\({}^{\circ}\) polarization channel are shown in Figure 9a. In order to solve the problem of wavenumber drift of a spectral line caused by tilting and pitching errors generated during the processing and adjustment of a multi-stage micro-mirror, wavenumber calibration experiments were conducted. The filter plates of each central wavelength were assembled into the system, and the polarization interference image arrays after adding the filter plates of each central wavelength were measured respectively. The decoupling of the spectrum was completed according to the above method, and the reconstructed spectrum was obtained after discrete Fourier transform, as shown in Figure 9b. Since the tilt and slope errors of the rooftop-shaped multi-stage micro-mirror cause linear wavenumber drift to the spectrum, the linear error transfer model of the wavenumber drift is:  
\[\
u t=k_{1}\
u+b_{1} \tag{17}\]  
Here, \(\
u^{\prime}\) is the spectral wave number after calibration, and \(\
u\) is the spectral wave number actually measured. The gain coefficient \(k_{1}\) is 0.9974 and the bias coefficient \(b_{1}\) is 11.9597 obtained through linear fitting, so the linear fitting model is:  
\[\
u t=0.9974\
u+11.9597 \tag{18}\]  
The calibrated central wavenumbers are 2642.98 cm\({}^{-1}\), 2525.05 cm\({}^{-1}\), and 2111.24 cm\({}^{-1}\), respectively, and the wavenumber errors are 1.66 cm\({}^{-1}\), 2.12 cm\({}^{-1}\), and 0.48 cm\({}^{-1}\), respectively. The wavenumber errors are all less than 1/2 of the theoretical spectral resolution (7.8 cm\({}^{-1}\)), which proves that the calibrated central wavenumbers are basically in accordance with the theoretical wavenumbers. After the accuracy of the spectral wavenumber measurement was verified by wavenumber calibration, spectral data detection was performed on the high-temperature target to obtain the target polarization spectral information. The target (as shown in Figure 6b) was subjected to target imaging experiments with 38\({}^{\circ}\) polarized light incident in the system with a 3970 nm central wavelength filter. According to the spectral decoupling method mentioned above, the polarization interference intensity data cube of the target's four polarization directions, \(I_{\theta}\)[\(x\),\(y\),\(\Delta\)(\(m\),\(n\))], can be obtained. The polarization interference intensity sequences corresponding to the characteristic pixel point (10.6) of the polarization interference image unit selected at the central wavelength of 3970 nm are shown in Figure 10.  
Figure 9: Filter spectrum: (**a**) theoretical spectrum; (**b**) reconstructed spectrum of each narrowband filter.