Enhancing the measurement stability of segmented mirror edge height through synchronous measurement in atmospheric turbulence

Area of Science:

• Optical metrology
• Astronomical instrumentation
• Adaptive optics

Background:

• Accurate edge height measurement is vital for co-phased adjustment of segmented primary mirrors in giant astronomical telescopes.
• The Chinese Giant Solar Telescope (CGST) requires interferometric measurements exceeding 10 µm for integrated co-focus and phasing.
• Multi-wavelength technology is considered for CGST to extend measurement range, but faces challenges with edge jumps.

Purpose of the Study:

• To address the edge jump problem in multi-wavelength optical interference measurements for large solar telescopes.
• To develop and validate a technique for accurate co-phased adjustment of segmented mirrors under turbulent conditions.
• To enable efficient and precise alignment for the Chinese Giant Solar Telescope (CGST).

Main Methods:

• Investigated the cause of edge jumps in multi-wavelength measurements, identifying atmospheric turbulence as a primary factor.
• Proposed and implemented a dual-wavelength synchronous measurement technique.
• Conducted experiments on a segmented-mirror system under simulated turbulent atmospheric conditions.

Main Results:

• The dual-wavelength synchronous measurement technique significantly reduces or eliminates edge jumps.
• Under turbulent conditions with a one-second exposure, the probability of edge jumps was negligible.
• Co-phased adjustment using this technology requires only a few seconds per measurement and adjustment cycle.

Conclusions:

• Dual-wavelength synchronous measurement is an effective solution for the edge jump problem in large telescope phasing.
• This technique enables rapid and precise co-phased adjustment for the CGST, completing the process in 2-3 rounds.
• The method ensures the diffraction-limited observational capabilities of solar telescopes are maintained.