| The aerial camera is an optical instrument that is installed on the aircraft to obtain ground information from the air.As an important key device for aerial photogrammetry,it is optically photographed to obtain clear image information.With the development of modern technology,the resolution requirements of aerial cameras are getting higher and higher,and the focal length of aerial cameras is getting longer and longer.As the resolution and focal length of the camera increase,the impact of the camera's working environment on the image quality of the camera becomes more serious.The change of ambient temperature is an important factor affecting the image quality of aerial cameras.Therefore,studying the influence of temperature change on the aerial camera,using the appropriate athermal design method,reducing the influence of temperature change on the imaging quality and enhancing the temperature adaptability of the camera is an important research in the field of aerial camera design.This paper discusses the theoretical basis and development status of the athermal design of optical systems,and systematically studies the effects of temperature changes on imaging quality.Focusing on how to improve the temperature adaptability of optical systems,it is proposed to use the back focal length matching method to guide the completion of the athermal design.According to the different characteristics of different structures of the camera,the design is based on the R-C system in the mirror-lens structure and introduced the design process of the folding optical system.The design result of the camera is built into a finite element model,the corresponding temperature analysis is carried out,and corresponding optimization measures are taken for the optical system.Finally,a temperature experiment was performed on the camera to verify the simulation results.The main research contents of this paper can be summarized as follows:This paper first introduces the research background and significance of the athermal design of optical system,studies the temperature effect theory of optical system,analyzes the influence of temperature change on various parameters of optical system,and explains the reason why the imaging quality of optical system changes with temperature.Subsequently,the athermalization technology was studied and three main athermalization technologies were introduced.On this basis,an athermal design idea of optomechanical combination is proposed: back focal length matching.The athermal design of the optical system is achieved by matching the structural back focal length of the optical system with the optical back focal length.Then the basic process of the visible light system's athermalization design is introduced.Usually,the optical system that meets the imaging requirements at normal temperature is designed,and then the temperature analysis of the optical system is performed to determine the athermalization optimization scheme.When selecting the camera structure,by comparing the advantages and disadvantages of several different optical system structural forms,combined with the actual situation of engineering application,it is determined that the design is based on the R-C system in the mirror-lens structure.In the temperature analysis,in order to be closer to the real situation,the optical system is analyzed by the method of thermal integration analysis.The finite element model was established by using finite element software.The imaging quality of the optical system under different temperature conditions was analyzed,and the optimization scheme was determined according to the analysis results.And combined with the actual situation of engineering applications and past experience,choose the best design.Finally,the experimental platform is used to test the temperature of the optical system.The horizontal temperature test is used to verify the correctness of the model.The ambient temperature simulation test is used to verify whether the optical system meets the design requirements. |
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