In order to solve the problems of long manufacturing cycle and high processing cost of mirrors in reflective optical systems of space cameras, a method for manufacturing metal mirrors based on additive manufacturing process is proposed. This paper designs an open honeycomb structure on the mirror backplane, mirror blank is prepared by additive manufacturing technology. Preliminary improvement of surface quality with rough machining and diamond turning. Then, a high-precision mirror surface is obtained through surface modification and secondary diamond turning. The diameter of the prepared mirror is 110mm, mass reduction rate of 70% and surface shape accuracy is better than λ /15 RMS( λ =632.8nm).The results show that the metal mirror prepared by this process can meet the requirements of high-precision reflective optical systems. The research work in this article can provide technical reference for the application of additive manufacturing technology in the field of optics. It has important reference and guiding significance for the research and application of related fields.
The research on optical-mechanical system based on additive manufacturing is based on additive manufacturing, diamond turning, high-precision magnetorheological polishing, surface modification technology, internal lattice structure topology optimization and so on. It can overcome the problems of adhesive use and material matching in the traditional structure design, greatly reduce the difficulty of assembly and thermal control, and realize the lightweight design of internal structure that can not be realized by traditional processing methods. In addition, because the mirror body and its supporting structure are made of same metal materials and integrated, the strength and stiffness are greatly improved compared with the traditional design method. This paper summarizes the development status and technical parameters of additive manufacturing opto-mechanical system at home and abroad. The research progress of surface modification technology by domestic and foreign scholars was focused and the post-processing process and core technologies of the optical-mechanical system were described.
Spatial heterodyne spectroscopy for long-wave infrared identifies an ozone line near 1133 cm-1 (about 8.8 μm) as a suitable target line, the Doppler shifts of which are used to retrieve stratosphere wind and ozone concentration. The basic principle of Spatial Heterodyne Spectroscopy (SHS) is elaborated. Theoretical analyses for the optical parameters of spatial heterodyne spectroscopy are deduced. The optical system is designed to work at 160 K and to maximize the field of view (FOV). The optical design and simulation is carried on to fulfill the requirement. The principle prototype was built and a frequency-stable laser was used to conduct the experiment. Result shows that the designed interferometer can meet the requirement of spectral resolution (0.1 cm-1 ) and that the spatial frequency of fringe pattern is consistent with the theoretical value at normal temperature and pressure.
The influence of adhesive bonding and curing on the accuracy of mirror surface shape was analyzed to realize low-stress assembly of large aperture mirror. Firstly, based on Hooke's law, a curing shrinkage stress equation was deduced, taking deformation of the mirror and support structure into account under the boundary condition of continuous edge bond, and key parameters effecting mirror deformation were obtained. Secondly, for a 514mm ULE spectrometer primary mirror with an inserts structure mosaiced and bonded on mirror-back, an equivalent linear expansion coefficient method was used for finite element modeling. The shrinkage stress at the bond edge of mirror and the mirror surface shape were analyzed. It’s found that adhesive shrinkage has a significant effect on the mirror surface shape. Finally, the inserts structure of mirror assembly was optimized. In contrast to the non-optimum structure, the average stress of adhesive surface caused by adhesive curing shrinkage reduced from 0.28MPa to 0.18MPa, and the mirror surface shape (Root Mean Square, RMS) reduced from 0.029λ to 0.017λ. Finite element analysis results of the mirror assembly were given at last, surface shape accuracy (RMS) of mirror is 0.012λ under a load case of 1g gravity, and the first-order natural frequency of the component is 216 Hz. The obtained results showed that a suitable optimized support structure can effectively relieve adhesive curing stress, and also satisfy the design requirements for both the static and dynamic stiffness.
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