Research On Key Technology Of High Efficiency And High Precision Manufacturing Of Space Large Scale SiC Aspheric Mirrors

With the continuous increase in the number and the light aperture of spatial optical systems,it has imposed more stringent requirements on the surface precision and processing efficiency of spatial optics.Silicon carbide materials have been recognized as the preferred mirror materials for 21st-century space optical systems and large-scale ground optical systems.Research on light-weight silicon carbide optical materials and its development are being carried out in an intense and orderly manner.Optical systems using silicon carbide as a mirror material have been used or will be put into use extensively.Scholars at home and abroad have made great progress in high-precision manufacturing of large-aperture optical components.In contrast,the manufacturing process of silicon carbide mirrors,especially large apture aspherical mirrors,is difficult to meet the increasing requirement for the number and quality of silicon carbide mirrors.Therefore,it is urgent to carry out innovative research on the bottleneck problems of high-efficiency and high-precision processing technology and theoretical of large-aperture optics.This thesis focuses on the high-precision and high-precision manufacturing requirements for large-diameter aspherical SiC mirrors.Aiming at gravity and stress unloading methods for large-aperture spatial mirrors,CCOS edge effect control mechanisms and processes,and the simultaneous guarantee of accuracy and convergence efficiency and other technical challenges,relevant research in the theory,methods,and processes of silicon carbide material polishing is carried out to provide new methods and approaches for high-efficiency and high-precision manufacturing of large-aperture aspheric SiC mirrors.The specific research includes the following aspects:(1)Research on the gravity and stress-deformation laws of lightweight large mirrors is carried out in response to the manufacturing challenges such as discontinuous local stress effects "lattice effect" and non-linear curvature distortion errors in the polishing process of large-aperture and thin mirrors.Based on the finite element static analysis method,the gravity deformation of lightweight large-diameter spatial reflectors under the action of gravity and stress is studied.The reflector support structure is optimized according to the size and distribution of the gravity deformation of the mirrors.According to the contact area between the support structure and the mirrors,the deformation laws is analyzed with gravity and stress.According to the precision requirements of manufacturing,the support structure is optimized.The lattice effect mechanism is discussed,and the effect of local polishing stress on the manufacturing precision of lightweight mirrors is analyzed.Based on the above research the parameters of the traditional contact polishing process are optimized.(2)The principle of nonlinear distortion of edge effect in the processing of off-axis aspherical and other complex optical surfaces is studied.In order to meet the requirements of rapid convergence manufacturing whole aperture,different sizes of polishing tools based on the discrete local error figuring technique are proposed.Aiming at the high-precision edge modification,a local variable pressure polishing method is proposed.The local variable pressure polishing tool for the edge effect is optimized.Based on the traditional polishing mechanism of silicon carbide material,the variable pressure polishing mechanism is analyzed.The edge errors convergent processes and theories for deterministic polishing based on an active nonlinear compensating method is established to realize whole-range error convergence for full-aperture data with different shapes of optics.(3)Aiming at the defects of the existing large-aperture SiC aspherical mirror manufacturing process,a combined processing method based on figuring efficiency of the removal function is proposed.Based on the analysis of the figuring ability of removal function and the smoothing principle of polishing membrane,an evaluation parameter for the convergence efficiency is established,which is the figuring efficiency of the removal function.And the specific method of combined machining is proposed based on the figuring efficiency.The polishing processes of different surface precision stages is determined and principle of removal function is selected.Further,the process is optimized by filtering process.