Modeling And Integrated Design Of Imaging Spectrometers With Aberration-correction Convex Holographic Gratings

With the development of optical remote sensing technology and its more and more extensive application in the field of Aeronautics and Astronautics,the technical indexes of imaging spectrometers,such as relative aperture,spectral resolution,spatial resolution and the detection ability of weak signal,are required to be much better.At the same time,in order to adapt to the rapid development and carrying requirements of new remote sensing platforms such as UAV(unmanned aerial vehicle),miniaturization and lightweight have become another development tendency of airborne and spaceborne imaging spectrometers.The spectrometer with a convex holographic grating is based on the Offner concentric configuration,which has good optical performance,simple and compact structure,and meets the needs of lightweight and miniaturization;moreover,its application affected by the material and environment is very small,so it is easy to achieve the focal surface stability,spectral stability and broadband spectral imaging,which is suitable for the space environment.At present,the imaging spectrometer with a convex holographic grating is widely used in optical remote sensing and other fields closely related to the development of national economy,including satellite remote sensing,security,ecology,agriculture and forestry,resource exploration,oceanography,food safety,pharmaceutical monitoring,medicine,manufacturing,etc.In view of this,the paper carried out the research of spectrometers with convex holographic gratings based on the Offner concentric configuration.The aim is to develop aberration-correction convex holographic gratings and the aberrationcorrection spectrometers with independent intellectual property rights.In this paper,the geometric aberration theory,configurations and design methods of the spectrometers with convex holographic gratings have been studied.The key theory and technology of developing the aberration-correction spectrometers with convex holographic gratings are broken through,providing conditions for the mass production of such spectrometer.The main contents of this paper include the following parts:Firstly,a design method of using an aberration-correction convex grating as the core dispersive device of the Offner imaging spectrometer is proposed.Compared with traditional convex gratings,aberration-correction convex gratings have the ability of both dispersion and aberration correction.The introduced system aberration is selfcorrected,retaining the concentric structure of the standard two-element three-reflection system,and overcoming the defects of the aberration-correction technology of the traditional convex grating imaging spectral system.Secondly,a theoretical model of aberratios of the convex grating imaging spectral system is established.Based on the Fermat principle,the image spot diagram function of the convex grating imaging spectral system is derived,and the various aberrations of the system are expressed by the recording parameters of the convex grating and the structure parameters of the system.The convex grating imaging spectral system is modeled and simulated both with ZEMAX optical design software and MATLAB simulation software,which provided theoretical guidance for the optimal design of aberration-correction convex gratings applied to imaging spectrometers.Thirdly,an aberration-correction convex grating applied to Offner concentric Rowland circle structure is designed.Aiming at the main aberration astigmatism of the convex grating imaging spectral system,the focal condition of the system is analyzed,and the mathematical relationship between the grating groove function coefficients and astigmatism of the system is derived.Then,based on the optical path function theory,an anastigmatic convex grating imaging spectral system is optimally designed.Fourthly,based on the aberration correction theory of convex gratings,the integrated design research of aberration-correction convex gratings and imaging spectrometers is carried out,and the optical imaging performance is evaluated.According to the optimization method of convex grating groove function fitting,the convex grating imaging spectral system is integrated and optimized.For the matching problem of numerical aperture between the imaging spectrometer’s fore-telescope system and the imaging spectroscopy system,a multiple structure optimization method is adopted.The aberration of the overall system is evenly distributed,and high-quality imaging in the whole working spectral range is realized.Fifthly,based on the holographic reconstruction principle,the exposure structure of the aberration-correction convex holographic grating is optimized and designed.According to the optical path function theory,the theoretical model of the aspheric wave exposure system is established and the RMS optimization function of the spot diagram is derived.Combining the imaging characteristics of the Offner relay imaging system and the principle of holographic reconstruction,the global optimization algorithm genetic algorithm performs an integrated optimization design on the exposure system of the aberration-correction convex holographic grating and its imaging spectral system.Analyzing the performance of the optimized aberration-correction convex holographic grating imaging spectral system,which provides technical guarantee for the feasibility of the aberration-correction convex holographic grating.