| Asteroids are important targets for deep space exploration in the 21 st century and contain rich material resources.The detection of asteroids can enable human beings to further understand the universe,understand the solar system,and detect the formation and evolution of the earth,which has lofty scientific significance.Navigation imaging and spectroscopic integrated cameras have the characteristics of miniaturization and integration,which can meet the requirements of asteroid spacecraft for optical autonomous navigation,high-resolution imaging and hyperspectral analysis.With the development of China’s asteroid detection,the demand for navigation imaging and spectroscopic integrated cameras is becoming increasingly strong.Navigation imaging and spectroscopic integrated cameras have some problems which have few spectral segments and low spectral resolution.To solve these problem,this paper uses a dual-channel co-aperture optical structure based on digital micromirror device（DMD）.The optical structure enables pixel-level light modulation between the two branches through DMD devices,enabling the system to both high-resolution imaging and navigation,as well as area array spectroscopy of moving targets such as asteroids.Based on specific innovative projects,this paper investigates the problems in the design of dual-channel co-aperture optical systems for high-resolution imaging and hyperspectral acquisition for asteroid detection.The main research content includes the following four aspects:First,the overall layout design of the system was studied.By modeling and analyzing the folding optical path based on DMD,the conclusion is drawn that DMD will limit the optical performance of the co-aperture system.The design scheme of the dual-channel co-aperture optical system based on DMD and the prism of total internal reflection（TIR）is proposed which improved the field of view and relative aperture of the co-aperture system.Secondly,the effect of three-connected TIR prism on the image quality of the imaging branch was studied,and the aberration correction of the imaging branch was performed.In this paper,the vector ray tracing model of the prism is established,the influence of various possible aspects of the prism on the aberration is analyzed,and the aberration elimination conditions of the high-resolution imaging branch optical system are obtained,which provides a theoretical basis for the design of the high-resolution imaging branch with excellent imaging quality.Then,aim at the influence of DMD on the spectral deformation of the hyperspectral acquisition branch,a vector dispersion model of the spectrophotonic element under the angle of incidence of any beam is established,and the characteristics of the spectral deformation corresponding to the two-dimensional slit are analyzed through this model,as to obtain a method to reduce the spectral deformation variable of the two-dimensional slit,which provides a theoretical basis for the design of the hyperspectral acquisition branch.Finally,according to the above research results,a dual-channel co-aperture optical system with an F number of 4,a field of view angle of 2.14°× 1.17°,and a focal length of 400 mm was designed.The design results show that the imaging branch and the spectral branch of the system has good imaging quality,which can not only obtain high-spatial resolution area array images with instantaneous field of view angle of 18μrad,but also obtain spectral information of the area of area with a spectral resolution of 3 nm,which can meet the requirements of navigation imaging and spectral integration camera.It provides certain technical support for the development of advanced navigation imaging and spectral integration cameras in China.After the design is completed,the three-connected TIR prism is processed.And the feasibility of the scheme is verified by the construction and imaging experiments of prototype of the dual-channel co-aperture optical system. |
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