Design of long-wave infrared coded aperture imaging optical system and polarization aberration analysis based on vector diffraction characteristics

To address the issue where diffraction phenomena in long-wave infrared (LWIR) polarization optical systems containing a digital micromirror device (DMD) induce variations in polarization aberrations, thereby degrading polarization measurement accuracy, we propose a polarization aberration analysis and compensation method for LWIR secondary imaging optical systems incorporating DMD. The method effectively mitigates the impact of diffraction on polarization aberrations. Simulation results indicate that the modulation transfer function (MTF) across the whole field of view approaches the diffraction limit at the cutoff frequency, with maximum distortion below 0.2%. The imaging quality remains excellent, while the diattenuation and retardance of the system are reduced to 0.08 times and 0.74 times of their original values, respectively. Experimental measurements confirm polarization aberration errors below 5%, with polarization preservation performance ranging from 92.06% to 95.01%. The system achieves diffraction-limited performance. The proposed analytical model elucidates the relationship between diffraction and polarization aberrations, and the compensation method significantly reduces polarization aberrations.