In view of the differences in polarization characteristics caused by different states of the detected targets, different radiation spectra, different sizes and shapes, complex transmission environment of soot and haze, and variable light field interference, we conduct the target multispectral polarization model and polarization characteristic transmission model, develop the optimal design method of micro-nano grating polarizer array, put forward the principle and schemes of high-resolution imaging detection instruments, and propose a novel deep network to solve the polarization image fusion problem through a self-learning strategy. We aim to use multispectral polarization imaging technology to solve the problems of complex optical field interference, limited visible distance, and insufficient classification ability of optical imaging under harsh conditions.

In this paper, the polarization imaging detection method and multispectral information fusion technology are studied, and the overall scheme of the multispectral polarization imager is proposed. Scientific methods such as the theory and model of target polarization characteristics under complex optical fields, micro-nano grid focal plane polarization device, optimization and testing of a multispectral fully polarized imaging system, and polarization image processing based on polarization difference characteristics are condensed.

Key technologies and solutions such as modeling and testing of target polarization characteristics generation and transmission, optimization of metal micro-nano grating polarization elements with high extinction ratio, the optical design of multispectral polarization imaging and testing system, and multispectral polarization information processing are analyzed. This will lay the foundation for the development of a multispectral polarization imaging detection test prototype, which will meet the practical application requirements of visual assistance and guidance in optical imaging.

We conduct the target multispectral polarization model and polarization characteristic transmission model, which reveal typical target multispectral polarization law and haze and dusty weather multispectral polarization transmission law and provide theoretical basis for multispectral polarization information processing.

We develop the optimal design method of micro-nano grating polarizer array, solve the defects of the current defocused plane polarization imaging device that only has micro-nano linear grating and cannot produce circular polarization, and propose a new chiral micro-nano circular grating mechanism. We also analyze the physical nature of the low extinction ratio of the division of focal plane polarization imaging, put forward the physical mechanisms for the generation of the high extinction ratio of the linear grating, and discuss the effect of the deviation of the preparation parameter on the extinction ratio law. Combining the micro-nano linear grating and circular grating, we study the new device of full polarization high extinction ratio and split focal plane imaging, and lay the technical foundation for the development of multispectral and multi-dimensional polarization high-resolution imaging detection instruments.

Aiming at the problems of close detection distance, low detection sensitivity, and narrow environmental application range of the existing instruments under the haze and smoke conditions, we put forward the principle and scheme of multispectral polarization high-resolution imaging detection instruments and the design scheme of multi-optical imaging optical system for the characteristics of large loss of light energy in polarization imaging. We break through the optical system design based on the polarization aberration correction and multispectral polarization calibration, so as to significantly improve the instrument's imaging and detection ability in the haze and dusty environment.

A novel deep network is proposed to solve the polarization image fusion problem through a self-learning strategy. The network consists of an encoder layer, a fusion layer, and a decoder layer, where the feature maps extracted by the encoder are fused and then fed into the decoder to generate a fused image. Given a multidimensional polarization image, effective features are extracted from this source image, which are fused to form an information-rich polarization image for subsequent advanced image applications.

Aiming at the problems of "not recognizing", "not seeing far", and "not being able to recognize" in optical detection caused by harsh environments and meteorological conditions, we put forward a multispectral polarization imaging detection technology and expect to achieve breakthroughs in three aspects: 1) in terms of device development, through the improvement of circular micro-nano grid design method and micro-nano grid substrate material-structure, it is necessary to prepare new devices with high extinction score of focal plane imaging; 2) in terms of system design, breakthroughs are required in the design of multi-optical path bias-preserving optical system, high-transmittance and high bias-preserving optical coating and other key technologies, and high spatial and temporal matching of instrument information acquisition; 3) in terms of information processing, the study of the polarization characteristic model and polarization transmission model of the target is important.

Adverse environmental and weather conditions not only have a great influence on optical imaging detection but also have an extremely serious effect on aircraft landing safety and other areas. Fog and low visibility conditions cause aircraft to fail to land properly, making flights grounded or delayed, with significant economic and social impacts. At present, to perform approach and landing under low visibility conditions, pilots mostly use ground and airborne navigation facilities/equipment to guide the aircraft to the runway in accordance with the specified flight path, mainly including instrument landing system ILS, microwave landing system MLS, satellite navigation technology GPS, laser landing system, and visual landing system. Under extremely severe conditions such as no radar guidance or no ground indication, the aircraft cannot obtain effective and safe landing guidance and assistance through the above guidance methods. Therefore, it is of great significance to develop visual aids for aircraft landing under adverse conditions. It can improve the safety of airplane landing under bad conditions such as smoke environments, sea fog environments, and low illumination environments.