Calibration of interferometer instrument transfer function using reconfigurable sinusoidal phase via spatial light...

Area of Science:

• Optical metrology
• Interferometry calibration

Background:

• Extreme surface form measurement accuracy is critical for X-ray and EUV optics.
• Existing instrument transfer function (ITF) calibration methods lack standardization and require difficult fabrication of specialized structures.

Purpose of the Study:

• To propose and validate a novel, flexible method for instrument transfer function (ITF) calibration.
• To overcome the limitations of current ITF calibration techniques, particularly the need for high-accuracy fabricated structures.

Main Methods:

• Development of a reconfigurable sinusoidal phase (RSP) method utilizing a high-resolution spatial light modulator (SLM).
• Generation of variable sinusoidal phases with different spatial frequencies and amplitudes.
• Compensation of inherent wavefront distortion to single-nanometer PV and sub-nanometer RMS.

Main Results:

• The RSP method successfully compensates for wavefront distortion, eliminating the need for high-accuracy flat plates.
• Demonstrated repeatability and fidelity of the RSP ITF calibration results.
• The method aligns with the ISO definition of ITF.

Conclusions:

• The reconfigurable sinusoidal phase (RSP) method is a viable and promising approach for instrument transfer function (ITF) calibration.
• This technique simplifies calibration and enables investigation into optimal ITF calibration structure designs for specific instruments.