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

Area of Science:

• Optical Engineering
• Astronomy Instrumentation

Background:

• Segmented telescopes require precise co-focus adjustment for co-phase alignment.
• Current methods using Shack-Hartmann Wavefront Sensors (SHWFS) leave residual piston errors exceeding algorithm capture ranges.

Purpose of the Study:

• To enhance the co-focus adjustment accuracy for the Chinese Galactic Survey Telescope (CGST).
• To develop a method that reduces residual piston errors to meet the precision requirements of phasing algorithms.

Main Methods:

• Proposed a fine co-focus adjustment technique based on cross-calibration.
• Utilized a high-precision detector to calibrate and fit SHWFS measurements.
• Mitigated impacts of atmospheric turbulence and systematic errors on piston measurement.

Main Results:

• Simulations showed the cross-calibration method significantly improved adjustment accuracy over standard SHWFS.
• Residual piston errors were reduced to be within the capture range of multi-wavelength PSF phasing algorithms.
• Experimental validation on an 800mm segmented mirror system achieved residual piston errors within ±15μm.

Conclusions:

• The cross-calibration method offers a viable solution for high-accuracy co-focus adjustment in segmented telescopes.
• This technique enables precise alignment crucial for advanced astronomical observations.
• Successfully demonstrated experimental feasibility and effectiveness.