Study On Corrected Technology Of Large Aperture Primary Mirror Based On SiC Thick Mirror

With the increasing aperture of the optical remote sensor,it is an important target to improve the precision of the primary mirror while improving the light collecting ability and resolving power.For large-aperture telescope,not only does the traditional support system have a high cost and high technical requirement,but also it is hard to meet the precision target.Active optics can adjust the deformation of optical components to ensure good surface accuracy,which greatly reduces the manufacturing cost and improve the surface accuracy.Compared with traditional passive support,the support system of primary mirror using active optics is called active support.The active support design of a 2m Si C primary mirror of an optical remote sensor based on active and passive composite support is studied in this paper.The main works are as follows:1 ? On the basis of summarizing the active support systems of large-aperture telescopes at home and abroad,the characteristics of various support systems are expounded in detail,and the developing direction of active support of large-aperture mirror is summarized.2?The active and passive principle of active optics,the principle of active and passive compatibility,and the basic theory of zernike decomposition and fitting of surface shape are described in detail,which is based on active and passive support ofprimary mirror.3?An active support scheme for 2m Si C thick mirror is proposed.According to the actual working conditions,the aberrations to be corrected are determined as astigmatism and trefoil.The correction range is l/100-1l(l(28)632.8nm).33 junctions of reinforcing ribs are selected as candidate active points.The stiffness matrix of 1000 × 33 is extracted by finite element analysis,and the intrinsic mode of the model is extracted by SVD(Singular Value Decomposition).The model is used to analyze the primary mirror's ability of correcting.According to the corrected aberration,stiffness matrix and correction mode,the i SIGHT optimization link is constructed based on the genetic algorithm.The correction ability of the 18 active points is as follows: 0 ° astigmatism 3.71 %,45 ° astigmatism 3.65%,45 °trefoil12.8%,0 ° trefoil 13.5%.4?In this paper,the effects of 18 actuator failures on the four aberrations are studied.It is concluded that the failure of 1-3 actuators has little effect on the system,and the active support system has high redundancy and robustness.By analyzing the actuator output error,the system has the ability to correct the aberration when the actuator output error is 0.1N.According to the above analysis results,this paper gives the design index of the actuator.5 ? The actuator design is carried out.As the actuator work in space,so its structure is chosen as a stepper motor and a screw.According to the design index,the motor,transmission mechanism,sensor and so on are selected,and the open loop test is conducted.6?In order to validate the principle of active and passive compatibility and the feasibility of active support scheme,a 2m primary mirror active support design method is used to design 680 mm scale mirror active support,and the simulation experiment is carried out on the basis of the detected surface shape.In this paper,the active support scheme of 2m primary mirror based on active and passive composite support under on-orbit condition is put forward and the simulation experiment is carried out,which enriches the active optics theory.