Formation Study And Experimental Research On A Novel Design Of Membrane Mirror

The design of membrane mirror is a novel method proposed when the system resolution and light-weight requirements are raised along with the development of spatial optical applications.Due to the serious shape error aroused in the shaping process,traditional inflated mirrors with initially flat surface shapes were rarely applied in imaging systems.Hence,a novel design of inflated mirror is proposed in this paper.The reflecting surface is a pre-shaped membrane with an initially parabolic shape.The inner inflating pressure is considerably decreased by adopting the pre-shaped membrane.Small deformation of the membrane mirror with greatly reduced shape error is sequentially achieved,making the inflated mirror qualified for imaging system.Primarily,according to the working principle of inflated mir ror,the mechanical property of the membrane surface is analyzed based on the theory of shell.The conditions of small and large deformations are respectively considered.The relation between deflection and mechanical characteristics are calculated.Meanwh ile,the regularity of the shape deviation when inflating an initially flat membrane is concluded.Then,shapes of the pre-shaped reflecting surface under different pressures are analyzed and imaging performance of the infrared system is simulated.A finite element model of the pre-shaped membrane is built on the basis of its mechanical properties and design requirements.Then accurate shape data under different pressures can be acquired by iteratively calculating the node displacements of the model.Shape data are applicable to build up deformed reflecting surfaces for the simulative analysis in ZEMAX by being fitted to the standard aspheric function.Thus,the infrared imaging system is set up and the imaging performance of the pre-shaped membrane mirror is verified.Finally,based on the above simulative results,the infrared imaging optical system applying inflated pre-shaped membrane mirror is constructed.Ground-based imaging experiments of nature scene are conducted.Outfield imaging experiment examines the ability to reserve detail information of nature scene with complex constructions.Experiment results indicate that the MTF of the infrared system can reach to 0.3 at a high spatial resolution of 8.5lp/mm,and texture details of the nature scene are well-presented.Eventually clear infrared imaging is realized.Moreover,by summarizing the experiences in experimental process,factors arousing shape deflections in actual operations are discussed.In conclusion,the method provides theoretical basis and technical support for the applications in lightweight optical components with ultra-large apertures.