Research On Dynamic Aberration Characteristics And Correction Methods Of Conformal Dome

The hemispherical dome has a large air drag coefficient,which is harmful to the improvement of the missile’s speed,range,and maneuverability.It has become a major factor restricting the development of the missile at a high speed.In order to adapt to high-speed missiles,researchers proposed the conformal optical technology,which uses a streamlined design of the dome.The seeker equipped with a conformal dome has a smaller air drag coefficient and can achieve a larger field of regard in structure.However,the conformal dome will introduce dynamic aberrations that changing with look angles,which seriously affect the imaging quality of the detection system.Therefore,correcting dynamic aberrations introduced by the conformal dome is the core task of conformal optics.In this dissertation,geometric and aberration characteristics of conformal domes are studied.The method of reducing dynamic aberrations by designing the inner surface and the solution method of the initial structure of the arch corrector are proposed.Relevant technical achievements can provide theoretical and technical support for the application of conformal optics technology and play a positive role in improving the performance of missiles.The main research content of this dissertation is as follows:Geometric and aberration characteristics of conformal domes are investigated in this dissertation.Based on the principle of differential geometry,we studied the geometric characteristics of the conformal dome,and obtained the unified formua for calculating the curvature of the quadric surface and the formula for calculating the angle between the boresight and the normal.We also summrarized the influence of fineness ratio,edge slope,and center of rotation on the difference of curvature radius and the angle between the boresight and the normal.Based on Zernike aberration theory,influences of the material,thickness,fineness ratio,edge slope of domes and the apterture,rotatonal center of imaging system on the dynamic aberrations introduced by equal thickness coniciodal domes are studied.The results show that the aberrations introduced by conicoidal domes are deteriorated with the increase of the refractive index,thick,fineness ratio,edge slope,aperture ratio,and the position of the rorational center away from the vertex of the dome.Among them,the aperture ratio has the greatest influence on aberrations,followed by the edge slope,fineness ratio and refractive index,the thickness and the position of the rotation center have a relatively small effect on aberrations.Design method of the inner surface of conformal dome based on eliminating boresight error is studied in this dissertation.We analyzed the mechanism and the harm of the boresight error,and proposed the design method of the inner surface of the conformal dome based on eliminating boresight error.According to the laws of refraction and geometric relations,the equations that the inner suface should satisfy are established,and a numerical solution method of the inner surface is proposed.Taking the conicoidal dome as an example,we studied the aberration characteristics of domes when designing the inner surface based on eliminating boresight error.The analysis shows that compared with the traditional equal thickness conicoidal dome,dynamic aberrations introduced by the dome designed with the eliminating boresight error method are insensitive to the change of the look angle,which is beneficial to reduce the design difficulty of subsequent correctors.Design method of arch corrector based on improved Wassermann-Wolf equation is studied in this dissertation.The principle and design method of the Wassermann-Wolf equation for axisymmetric systems are described.By simplifying the entrance pupil of the imaging system into strips,we established the corresponding relationship between the object rays and the image rays that are parallel to each other in the sagittal plane when the rays passing through the dome and the arch corrector,and proposed a method suitable for solving the initial structure of the arch corrector.By improving the Wassermann-Wolf equation,the differential equations for the front surfaces and back surfaces of the arch corrector and the boundary conditions for numerical calculation are deduced.Taking the coniciodal dome with equal thickness and the coniciodal dome designed by eliminating boresight error method as examples,the front surfaces and back surfaces of the arch corrector are calculated using the improved Wassermann-Wolf equation and boundary conditions.The aberration analysis results show that using the calculated front surface and back surface as initial structures,the optimized arch corrector can effectively correct the dynamic aberration introduced by the conformal dome.The magnitude of residual aberration can be corrected by the deformable mirror.