Research On The Surface Deformation Of 1m Aperture Primary Mirror Under Support System

In a photoelectric theodolite,the main mirror support system is the critical component of the optical system which determines the image quality.With improvement of the mirror resolution,increasing the aperture and the focal length is the telescope development inevitable trend.However,it will lead to a series of technical problems,including self-gravity,support mode,loading,temperature and other factors which influence in the mirror surface deformation.Therefore,it is necessary to reasonably design support system and study the deformation of the primary mirror.The research status of the large aperture telescope system at home and abroad is introduced in this paper.According to the design principles of the primary mirror support system and the previous research experiences,the preliminary layout design of 1m primary mirror and support structures are completed,including main mirror material,diameter thickness ratio,the number and position of support points and support mode.Through the empirical formula and the finite element parametric analysis,the typical axial 18 points Whiffle-tree and radical floating hammer lever balance mechanism composite supporting mode is determined.The 3D mode of the 1m primary mirror and its support system are established,and reasonable the nonlinear contacts and constraint conditions are applied by FEA.Then,the primary mirror is carried out by the static analysis.The approximate actualsurface deformation of the mirror at different elevation angles are solved through the finite element analysis combining with the experimental results,and satisfies with the design requirement.The ten orders natural frequencies and mode shapes are gained by the dynamic modal analysis.Finally,the mirror system in thermal mechanical coupling situation is analyzed,and the shape change rule in the steady,axial and radial temperature gradient fields are respectively discussed.In conclusion,the allowable temperatures of the main mirror are obtained at the constant temperature field.And the shape of mirror is more easily affected by the radial temperature,so it must strengthen to control the radial temperature of the primary mirror.