Research On Key Technologies Of Wide-spectrum Computational Imaging With Single Diffractive Lens

The photoelectric imaging system with high resolution,light weight and low power consumption is the constant trend of the development of aviation and aerospace photoelectric imaging system.Diffractive optical elements have ultra-thin and ultra-lightweight structures,and a single element can perform complex modulation of the wavefront,which is one of the important development directions of large-aperture high-resolution imaging systems.The moire satellite in the United States is equipped with a diffractive primary mirror with a diameter of 20 meters;although the diffractive optical element can achieve large-diameter imaging,it is limited by the chromatic aberration and diffraction efficiency of the diffractive optical element.The technical route of increasing the system energy with a large aperture and correcting chromatic aberration with a rear mirror group has no prospect of development and application,so it is necessary to overcome the wide-spectrum imaging technology of a single diffractive lens.The traditional broadband diffraction imaging technology requires complex optical chromatic aberration correction components,resulting in low energy transmittance of the imaging system.Emerging computational optical imaging methods,with image algorithms as the core combined with the imaging characteristics of diffraction systems,have the function of replacing complex chromatic aberration correction components.With the improvement of people's cognition level,the establishment of a technical route for the coordinated optimization of harmonic diffractive optical system design and image processing is of great significance to the technological progress of broadband diffractive imaging systems.In this paper,the wide-spectrum computational imaging technology of single diffractive lens is studied,which mainly includes the following research contents:(1)Research on the image quality degradation model of harmonic diffractive optical elements in wide-spectrum imaging: for the edge artifacts and blur caused by chromatic aberration of harmonic diffractive optical elements,and the diffraction stray light effect caused by the reduction of diffraction efficiency,the imaging quality degradation model of harmonic diffractive optical elements is constructed,which is called harmonic diffractive optics.The optimal design of components and the construction of image restoration algorithm lay the theoretical foundation.(2)Research on the inverse optimization design algorithm of wide-spectrum achromatic harmonic diffractive optical elements: Focusing on the problem of insufficient optimization of the chromatic aberration of diffractive optical elements by current optical design software,the diffractive optical element is constructed with the point spread number of the constraining element as the link between optical design and image processing algorithm.The framework of the optimal design of the combination of components and image algorithms;the dual constraint factors of optical chromatic aberration and image restoration prior are constructed in the objective function,and the optimization algorithm of harmonic diffractive optical components based on objective function-assisted direct binary search is developed;designed in the visible spectrum.The achromatic harmonic diffractive lens is simulated and verified based on strict electromagnetic theory.(3)The computational imaging image processing algorithm of single diffractive lens is studied: based on the image quality degradation model of harmonic diffractive lens under wide spectral band,a deep residual network(MZDDR)model for multichannel subregional image restoration and super-resolution reconstruction is designed;The MZDDR network model is tested on the image standardization test data set to verify the robustness of the algorithm in general image processing tasks;by building a single diffractive lens imaging device,imaging experiments are performed on the exterior scene to solve the degradation of the wide-spectrum imaging quality of the single diffractive lens.Problems,test the effect of super-resolution reconstruction of the system;conduct simulation imaging experiments on achromatic harmonic diffractive lens imaging system to test the performance of the imaging system;compare the performance of ordinary harmonic diffractive lens computational imaging system and achromatic harmonic diffractive lens computational imaging system,which proves that the optimal design framework of the combination of diffractive optical elements and image algorithms can improve the computational imaging performance.In this paper,the image quality degradation model of harmonic diffractive optical element is deduced.Aiming at the inverse optimization design of low-harmonic diffractive optical elements with broad spectral bands,a direct binary search optimization design method based on objective function assistance is proposed,and an achromatic harmonic diffractive lens is designed.According to the image quality degradation model,a suitable computational imaging algorithm is proposed,which is the deep residual network model of multi-channel differentiated region image restoration and super-resolution reconstruction.A common harmonic diffractive lens computational imaging system device is built,and the system test imaging effect is good,and the superresolution reconstruction can improve the effect by 1.4 times.The achromatic harmonic diffractive lens computational imaging system is simulated by simulation,which shows better imaging performance.Compared with the ordinary harmonic diffractive lens computational imaging system,PSNR and SSIM are improved by 3.13 d B and 0.03,respectively,which verifies that the diffractive optical element in the computational imaging system is used The superiority of the optimal design framework combined with the image algorithm provides a new technical route for promoting the application of diffraction imaging systems.