Yu-yan CAO, Jian-li WANG, Tao CHEN, et al. Active compensation of aberration for large ground-based telescope based on Hexapod platform[J]. Optics and precision engineering, 2020, 28(11): 2452-2465.
DOI:
Yu-yan CAO, Jian-li WANG, Tao CHEN, et al. Active compensation of aberration for large ground-based telescope based on Hexapod platform[J]. Optics and precision engineering, 2020, 28(11): 2452-2465. DOI: 10.37188/OPE.20202811.2452.
Active compensation of aberration for large ground-based telescope based on Hexapod platform
As the diameter of a ground-based telescope increases
the image quality will significantly degrade because of optical misalignment
which is caused by gravity and thermal deformations of the telescope structure. To accurately estimate the misalignment error
a mechanical model of a telescope was established
and the computation method and compensation process were investigated. According the structural components of the telescope
the structural model was simplified
and then the mechanical model was established using the finite element method. Based on nonlinear least square fitting
a method was presented to compute the misalignment error between the primary and secondary mirrors in which the inputs were the current node position of the primary and secondary mirror surfaces. Thereafter
a method in which the optical axis of the primary mirror used as the benchmark were adopted to determine the length of the hexapod leg with the objective of compensating for the misalignment error. Finally
numerical examples of a ground-based telescope with a diameter of 2 m were presented to verify the presented methods and the corresponding theories. The simulation results show that there are obvious misalignment errors because of gravity and thermal deformations
with maximum root mean square (RMS) radii of the optical spots being 1 473 and 557
μ
m
respectively. After the secondary mirror compensation
the RMS radii of the spots are decreased significantly
with all of them being
<
32
μ
m. The results verify the misalignment error and the hexapod leg length computation methods.
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Keywords
references
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