Research On Support Technology Of Cryogenic Optical Mirror

Infrared detection technology is widely used in national defense,meteorology,resource exploration,environ-mental protection,astronomical observation and other fields.With the development of technology,infrared remote sensing instruments require higher accuracy.The cryogenic optical system can suppress the background noise and improve the sensitivity of the detector,which is of great significance to the application of infrared technology.The mirror is a key component that affects the imaging effect of the space camera.Mirror support technology has always been the focus and difficulty of space camera technology research.It is necessary to improve the surface accuracy,improve the dynamic stiffness,and reduce the quality through reasonable design.The larger the aperture and aspect ratio of the cryogenic mirror,the worse the surface accuracy in a cryogenic environment,and the greater the difficulty of supporting the mirror.The aspect ratio of the rectangular mirror directly affects the support structure of the mirror.This paper researched the support technology and support characteristics of mirrors with different aspect ratios in cryogenic environments.First,the paper summarized the design process and methods of cryogenic mirrors.Investigated the working environment of cryogenic mirrors and determined the corresponding design requirements.According to the support requirements and the working environment of the cryogenic mirror,selected the material for the mirror assembly.Researched the structure design and flexible design method of the mirror and analyzed the influence of the aspect ratio on the rectangular mirror.Secondly,researched the suitable support structure of mirrors with different aspect ratios at cryogenic.Designed the back center support structure for the square mirror,and designed the double-layer annular flexible groove based on the principle of flexibility to improve the cryogenic surface accuracy which is caused by the mismatch of thermal expansion coefficient of structural materials;Researched the changes in the position of the double-layer annular flex groove and the changes in related design parameters on the surface accuracy and mode of the mirror.Then researched and determined that the three-point back support structure is a reasonable structure of the medium-aspect ratio mirror and design a biaxial flexible structure to alleviate the surface change caused by the inconsistent deformation of the backplane and the mirror in the cryogenic environment.Researched the changes in the position and size of the biaxial flexible structure on the surface accuracy and mode of the mirror.Finally,compared multiple design options,eliminated the application of three-point support in large aspect ratio mirrors,determined that the six-point back support is suitable for large aspect ratio mirrors with small temperature changes and the six-point side support is the best support form for the cryogenic large aspect ratio mirror and researched the influence of the position of the six support points of the six-point side support on the cryogenic surface accuracy.