Robust adaptive phase-shifting demodulation for testing moving wavefronts

Area of Science:

• Optical Metrology
• Interferometry
• Wavefront Sensing

Background:

• Optical interferometers are highly sensitive to environmental perturbations affecting their optical path.
• Existing phase-shifting demodulation methods assume a static wavefront and global phase-shifting, limiting their accuracy in dynamic environments.

Purpose of the Study:

• To propose a novel and robust phase-shifting demodulation method for optical interferometers.
• To reduce detuning errors caused by environmental perturbations like vibrations and miscalibrations.

Main Methods:

• A new phase-shifting demodulation method based on local weighted least-squares estimation.
• The method estimates phase-shifting locally for each pixel, accommodating individual pixel phase shifts.
• Requires a sequence of at least 3 interferograms; phase shifts do not need to be known.

Main Results:

• The proposed method provides local phase-shifting estimation, unlike previous global approaches.
• Demonstrates robustness to environmental perturbations such as vibrations and optical setup miscalibrations.
• Successfully retrieves the modulating phase or wavefront under test even with dynamic wavefronts.

Conclusions:

• The novel local phase-shifting demodulation method offers superior robustness and accuracy for optical interferometry.
• This approach overcomes limitations of traditional methods by not assuming global phase-shifting or static wavefronts.
• Enables reliable wavefront measurements in the presence of environmental disturbances and system imperfections.