Analysis Of Influencing Factors Of Imaging Performance Of Aspheric Aerial Camera And Research On Flight Attitude Compensation

Aerial camera is a kind of equipment to obtain ground information.It has the characteristics of strong maneuverability,high timeliness and relatively low cost.It is widely used in environmental monitoring,geological survey,marine research and other fields.An aspherical aerial camera is an optical system that uses an airplane as a carrying platform and uses aspherical optical lenses in an aerospace environment.It can effectively improve the imaging performance of the optical system,simplify the system structure,reduce costs,and achieve functional integration.When the aerial camera is operating at high altitude,the imaging quality of the aerial camera is not only affected by the processing errors of the optical components,but also by external environmental factors(such as ambient temperature,vibration of the carrier,and flight attitude of the carrier,etc.)Impact.Among them,the ambient temperature can cause deformation of the optical components,and the vibration of the carrier and the change of the flight attitude will cause the overall displacement of the optical system,which greatly reduces the imaging performance of the aerial camera.This paper takes the aspherical aerial camera developed by the research team as the research object,and takes Modulation Transfer Function(MTF)as the performance index of the aspherical aerial camera imaging quality.The larger the MTF value of the optical system,the more the aerial camera’s imaging The higher the quality.Then,around the influence of ambient temperature,aircraft vibration and aircraft flight attitude on the imaging performance of aerial cameras,it analyzes the modulation transfer function(MTF)of the optical system in different external field environments.Finally,the three-axis stabilized platform developed by the research group is used to compensate the attitude angle caused by the change of the flight attitude of the carrier to ensure that the imaging quality of the aerial camera can meet the imaging needs.The specific research content is as follows:(1)Aiming at the influence of ambient temperature on the imaging performance of aspherical aerial cameras,this paper proposes a mathematical model of the influence of ambient temperature on the imaging performance of aspherical aerial cameras based on the structure and thermodynamics of the aspherical optical system.The amount of deformation,optical path difference and wave aberration of the element can predict the MTF of the optical system and reveal the change law of the MTF of the optical system under the effect of ambient temperature.Finally,simulation analysis and temperature imaging experiments are carried out for the impact of ambient temperature on the imaging performance of aspherical aerial cameras.The simulation results and experimental results are basically consistent with the theoretical prediction results,thereby verifying the correctness of the ambient temperature MTF prediction model.(2)Aiming at the influence of the vibration of the carrier on the imaging performance of the aspherical aerial camera,based on the imaging principle of the aspherical aerial camera and the principle of homogeneous coordinate transformation,this paper proposes a mathematical model of the influence of vibration on the imaging performance of the aspherical aerial camera.The vibrational image shift of is solved theoretically,and then the MTF of the optical system is calculated,and the mechanism of the influence of the vibration frequency and the MTF of the optical system is revealed.Finally,the accuracy of the vibration MTF model is verified through simulation analysis and vibration imaging experiments,and it is found that the vibration MTF prediction model can truly and effectively reflect the change law of the optical system MTF.(3)Aiming at the influence of the flight attitude of the carrier on the imaging performance of the aspherical aerial camera,this paper constructs the mapping relationship between the flight attitude angle of the carrier and the MTF of the aspherical optical system based on the imaging principle of the aspherical aerial camera and the principle of homogeneous coordinate transformation.According to the attitude image shift of the optical system,the MTF of the optical system under different flight attitude angles is obtained,and the law of the influence of different flight attitudes on the MTF of the optical system is revealed.Finally,the imaging performance of the aspherical aerial camera is studied using the flight attitude imaging experiment of the carrier.The experimental results are highly consistent with the vibration MTF prediction model,which verifies the accuracy of the MTF prediction model of the flight attitude of the carrier.(4)By comparing the MTF of the optical system in different external field environments,it is clear that the change of the flight attitude of the carrier is the key element that affects the imaging performance of the aerial camera.In order to ensure that the imaging quality of the aerial camera meets the needs of use,this paper further studies the compensation of the image shift caused by the flight attitude change of the carrier,and uses the three-axis stabilization platform developed by the research team to generate the attitude angle of the flight attitude change of the carrier.Compensation;based on the imaging principle of the aspherical aerial camera,the structure of the three-axis stabilized platform and the principle of homogeneous coordinate transformation,a carrier aircraft flight attitude compensation model is proposed,and genetic algorithms are used to solve the flight attitude compensation model,and the image of the optical system is calculated Shift compensation residuals and MTF.Then,the system modeling is carried out for the three-axis stable platform,and the sliding mode variable structure control method is used to compensate the mechanical rotation error caused by mechanical friction to ensure the stability of the three-axis stable platform.Finally,the aircraft flight attitude compensation imaging experiment is analyzed to verify the performance of the three-axis stabilized platform and the accuracy of the aircraft flight attitude compensation model.