Research on fine co-focus adjustment method for segmented solar telescope

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Abstract
For segmented telescopes, achieving fine co-focus adjustment is essential for realizing co-phase adjustment and maintenance, which involves adjusting the millimeter-scale piston between segments to fall within the capture range of the co-phase detection system. CGST proposes using a SHWFS for piston detection during the co-focus adjustment stage. However, the residual piston after adjustment exceeds the capture range of the broadband PSF phasing algorithm( ± 30μm), and the multi-wavelength PSF algorithm requires even higher precision in co-focus adjustment. To improve the co-focus adjustment accuracy of CGST, a fine co-focus adjustment based on cross-calibration is proposed. This method utilizes a high-precision detector to calibrate and fit the measurements from the SHWFS, thereby reducing the impact of atmospheric turbulence and systematic errors on piston measurement accuracy during co-focus adjustment. Simulation results using CGST demonstrate that the proposed method significantly enhances adjustment accuracy compared to the SHWFS detection method. Additionally, the residual piston after fine co-focus adjustment using this method falls within the capture range of the multi-wavelength PSF algorithm. To verify the feasibility of this method, experiments were conducted on an 800mm ring segmented mirror system, successfully achieving fine co-focus adjustment where the remaining piston of all segments fell within ±15μm.
Funding Information
  • National Natural Science Foundation of China (12273109)
  • Yunnan Province young and middle-aged academic and technical leaders reserve Talents Project (202405AC350004)
  • Yunnan Key Laboratory of Solar Physics and Space Science (202205AG070009)
  • Yunnan Revitalization Talent Support Program (202305AS350029, 202305AT350005)
  • Yunnan Provincial Science and Technology Department (202103AD150013)

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