Embedded parallel-actuated technology for deformable space segmented mirror.

The deployable segmented space imaging system is an important solution for future ultra-large aperture space optical systems. To achieve the imaging capability of an equivalent aperture monolithic mirror, it requires not only to ensure the positional accuracy in the cophasing process, but also to have extremely high surface accuracy and curvature consistency of the sub-mirrors. However, this work is extremely challenging due to the manufacturing error of the sub-mirrors and the complex space environment. Active optical technology can ensure the surface shape accuracy of the spliced mirror by controlling the mirror surface deformation and compensating for the wavefront aberration. This article compares and analyzes the control ability of two types of deformable mirrors actuated by vertical and parallel methods. We explored the characteristics of the influence function mathematical models of the two types of actuation forms and compared the aberration and curvature correction abilities of them through finite element analysis, summarizing the advantages of the parallel actuation forms. Finally, a 300mm aperture embedded parallel-actuated deformable mirror was designed and manufactured, and relevant experiments were conducted to verify its adjustment ability. By comparing and analyzing the experimental results with the design results, the adjustment ability of the embedded parallel-actuated deformable mirror was verified.

Stress-induced deformation of the coating on large lightweight freeform optics.

Large aperture, lightweight optics are frequently utilized in modern optical systems. However, despite the use of advanced techniques for developing their materials, fabrication, and mechanical structure, the coatings placed on the substrates induce slight lattice mismatches and increase the thin film stress on polished surfaces. This significantly distorts nano-accuracy optical surfaces, especially on lightweight freeform surfaces. In this study, we construct a finite element model (FEM) and a ray tracing model to estimate the impact of the stress-induced deformation of the coating on a 1.5m class lightweight silicon carbine (SiC) mirror with a freeform surface. Our simulation results are within 10% deviation from the experimental results, and the deformation texture map matches these results as well. We discuss several possible strategies to overcome stress-induced deformation, including fabrication pre-compensation, lightweight structure redesign, and an inverse print-through effect.