Application Research Of Nanowire Polarization Imaging System

In recent years,polarization imaging has become a research hotspot after spectral imaging.The polarization imaging system based on the nanowire grid and adopts the method of defocusing plane imaging.The system is small in size and light in weight,and is suitable for moving bases and observing moving targets.It is one of the most widely used polarization imaging methods in the world.In this article,we discussed how to improve the polarization imaging accuracy of the system.Firstly,for the nonuniformity of the nanowire grid,a high-precision non-uniform correction algorithm is proposed.Secondly,according to the distribution of micro-polarizers in the system,combined with the idea of image interpolation,a correction algorithm with high spatial resolution is proposed.Finally,for the problem of improving the imaging accuracy of the system,a mathematical relationship including the extinction ratio,the photoelectrons number received by per pixel and the imaging accuracy is established.Through simulation and experiment,we verified the effect trend of extinction ratio and the photoelectrons number received by the pixel on imaging accuracy,which provided theoretical guidance for the engineering application of the system.At the end of the article,we proposed a movable polarization imaging system for the problem of loss of optical energy in the imaging system,and focused on the analysis of the diffraction and polarization imaging accuracy of the system,which provides important for further research of the system theoretical basis.The research content of this article can be divided into the following parts:The Ministry of Defense has always required small and light weights for photoelectric loads,and hopes it can detect camouflaged targets.By referring to relevant information on polarization imaging abroad,the achievements of each country in the direction of polarization imaging are analyzed and compared.By comparing the imaging accuracy,system complexity,and error source devices of division-of-time polarization imaging system and the simultaneous polarization imaging system.The polarization imaging system based on the nanowire grid can meet the work requirements for light and miniaturized,moving bases to observe moving targets.In order to solve the problem of non-uniformity in the engineering application of the system,it is proposed to use an algorithm to correct the non-uniformity of the system.We first established a vector transmission matrix with nanowire grid superpixel groups as a unit,and used matrix least squares to fit the mathematical model of the optimal transmission matrix through multiple sets of incident light to obtain a nanowire grid polarization imaging system Non-uniform correction parameter.Secondly,combining the idea of nanowire grid scribing method and spatial interpolation,a correction algorithm with high spatial resolution is proposed.In order to solve the parameter optimization problem of the nanowire grid polarization imaging system,we analyzed the Stokes vector of two mainstream scoring methods.Aiming at the better scoring method,the relationship between detector noise,extinction ratio and polarization imaging accuracy is derived.Due to the coupling effect of extinction ratio and detector noise on polarization imaging accuracy,we use the photoelectrons number received by pixel as the key bridge,so that when the above two parameters are coupled,the optimal system parameter setting can be found through the established mathematical model.To further optimize the practical performance of the nanowire grid polarization imaging system.Firstly,through the real shot images of the sea,land and air environment through the nanowire grid polarization imaging system,it proves that polarization imaging has a strong advantage in identifying camouflaged targets,but the use is limited when the detection targets has a lower polarization characteristic.The detection efficiency is not as good as the traditional intensity imaging system.To solve this problem,this paper proposes a nanowire grid mobile polarization imaging system,which can realize the switching between polarization mode and intensity mode by moving the nanowire grid.In order to analyze the influence of the diffraction of the system on the accuracy of polarization imaging,a linear expression containing crosstalk matrix was established,and conditional numbers were used to quantify the accuracy of polarization imaging.To verify the above theoretical model,we conducted an instrument matrix test experiment: building a nanowire grid polarization imaging system,generating a controllable linear polarization light source through an integrating sphere,collimator,and polarizer,and changing the polarization of the incident light source by rotating the polarization element state.The optimal system instrument matrix is obtained by the method of least squares fitting,and through the calculation of the external field image and the entropy of the typical target information,it is verified that the high-precision correction algorithm proposed in this article can effectively improve the polarization imaging information of the system entropy.In order to verify the above mathematical model including extinction ratio,photoelectron number of pixel receiving and polarization imaging accuracy,we change the optical aperture and exposure time of polarization element in the system through the experimental system built in the previous chapter,and measure 4 groups of different extinction ratio and 7 groups of experimental data of the accuracy of the nanowire grating polarization imaging system with different electron numbers were collected,and the fitted data curves were in good agreement with the theoretical curves.Finally,the engineering reasons for the difference between theory and experiment are analyzed.At the same time,we take typical polarization images under different optical system parameters and exposure time,and further verify the theory of this paper by calculating the polarization imaging accuracy of the images.To sum up,aiming at the engineering application of the nanowire grating polarization imaging system,this paper proposes the nonuniform correction algorithm and high spatial resolution for the system,and establishes the mathematical model including the photons number received by pixel,extinction ratio and polarization imaging accuracy.At the same time,according to the needs of aerial target detection and the defects of the nanowire grating polarization imaging system,a movable polarization imaging system is proposed,and the relationship between the system diffraction and the polarization imaging accuracy is established.The research content of this paper is of great significance to the development of polarization imaging in the field of airborne optoelectronics.