Study on moment correction method of primary mirror semi-active support

Liu Xiangyi; Wang Fuguo; Zhang Jingxu; Fan Lei; Wang Wenpan

doi:10.3788/IRLA201948.0518003

In the development of large ground-based telescope technology, the primary mirror support technology is always a key technology. In this paper, a semi-active support method was researched based on a 2 m SiC lightweight primary mirror, which was used to correct some unpredictable low-order wavefront aberration caused by machining error, assembly error and other factors. Firstly, the finite element simulation model was established, and the finite element simulation was carried out. An unit correction moment (1 Nmm) of Mx or My, which were two orthogonal moments, was separately applied to the 6 Tripod soft hinge, so the primary mirror deformations under a total of 12 cases of the situation were respectively analyzed. And then with the linear superposition principle of small deformation, the correction ability of the moment correction method for low order wavefront aberration was analyzed and calculated. It could be seen from the analysis that the moment correction method could correct the tilt and astigmatism very well. The initial mirror RMS value of the tilt and initial astigmatism which were normalized to 1/10(=632.8 nm), could be respectively corrected to 0.687 nm and 2.97 nm, the correction abilities were respectively 98.9% and 95.3%, and the required maximum correction moments were respectively 6.3 Nmm and 19.9 Nmm. Then, according to the whiffletree support structure of the primary mirror, a structure of the moment correction was designed with the leaf spring at the Tripod soft hinge. Finally, the feasibility of the leaf spring correction structure was verified through experiments, and the feasibility of the semi-active support scheme of moment correction was verified further. And a certain degree of engineering experience for the implementation of the moment correction method has been accumulated with high guiding significance.

Study on moment correction method of primary mirror semi-active support

1. Changchun Institute of Optics,Fine Mechanics and Physics,Chinese Academy of Sciences,Changchun 130033,China

Received Date: 2018-12-09

Rev Recd Date: 2019-01-20

Publish Date: 2019-05-25

Key words:

Abstract: In the development of large ground-based telescope technology, the primary mirror support technology is always a key technology. In this paper, a semi-active support method was researched based on a 2 m SiC lightweight primary mirror, which was used to correct some unpredictable low-order wavefront aberration caused by machining error, assembly error and other factors. Firstly, the finite element simulation model was established, and the finite element simulation was carried out. An unit correction moment (1 Nmm) of Mx or My, which were two orthogonal moments, was separately applied to the 6 Tripod soft hinge, so the primary mirror deformations under a total of 12 cases of the situation were respectively analyzed. And then with the linear superposition principle of small deformation, the correction ability of the moment correction method for low order wavefront aberration was analyzed and calculated. It could be seen from the analysis that the moment correction method could correct the tilt and astigmatism very well. The initial mirror RMS value of the tilt and initial astigmatism which were normalized to 1/10(=632.8 nm), could be respectively corrected to 0.687 nm and 2.97 nm, the correction abilities were respectively 98.9% and 95.3%, and the required maximum correction moments were respectively 6.3 Nmm and 19.9 Nmm. Then, according to the whiffletree support structure of the primary mirror, a structure of the moment correction was designed with the leaf spring at the Tripod soft hinge. Finally, the feasibility of the leaf spring correction structure was verified through experiments, and the feasibility of the semi-active support scheme of moment correction was verified further. And a certain degree of engineering experience for the implementation of the moment correction method has been accumulated with high guiding significance.

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Reference (15)

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Study on moment correction method of primary mirror semi-active support

doi: 10.3788/IRLA201948.0518003

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