Active-compensation of systematic error for the 1000 mm aperture flat interferometer

Area of Science:

• Optical Engineering
• Metrology
• Interferometry

Background:

• Large-aperture interferometers are susceptible to systematic errors from material inhomogeneity, manufacturing, and gravity.
• These errors cause reference wavefront distortion, limiting measurement precision in large optical systems.

Purpose of the Study:

• To propose and validate an active-compensation method for systematic errors in large-aperture flat interferometers.
• To mitigate reference wavefront distortion using a deformable mirror.

Main Methods:

• An active-compensation method employing a deformable mirror to modulate the reference wavefront was developed.
• Matrix optics derived the relationship between deformable mirror sag and wavefront error.
• Two optical path designs were considered based on deformable mirror placement (at or near the pupil).
• An algorithm was created for calculating and controlling deformable mirror sag, independent of pupil placement.

Main Results:

• The developed algorithm effectively compensated for intentionally introduced systematic errors in a 1000 mm aperture flat interferometer.
• The algorithm's error was on the order of 10^-6 mm, within acceptable tolerances for deformable mirror surface shape.
• Ansys Zemax optimization determined optimal deformable mirror surface shapes.

Conclusions:

• The proposed active-compensation method successfully corrects systematic errors and reference wavefront distortion in large-aperture interferometers.
• The deformable mirror control algorithm offers a flexible and accurate solution for improving interferometric measurements.