Phase measurement of nonuniform phase-shifted interferograms using the frequency transfer function.

Area of Science:

• Optics and Photonics
• Metrology
• Surface Science

Background:

• Interferometry is crucial for precise surface measurements.
• Nonuniform phase shifts in interferograms present significant challenges for accurate phase retrieval.
• Existing phase measurement methods have limitations in handling complex phase variations.

Purpose of the Study:

• To develop a robust phase measurement method for interferograms with nonuniform phase shifts.
• To improve the accuracy and reliability of phase retrieval in optical metrology.
• To provide a superior alternative to current phase-shifting algorithms.

Main Methods:

• Phase shifts between consecutive interferograms are measured.
• Interferogram data spectrum is modified using measured phase shifts.
• A phase-shifting algorithm (PSA) is designed using frequency transfer function formalism.
• The proposed PSA is validated using experimental data.

Main Results:

• The developed PSA accurately estimates the surface of an aluminum thin film.
• The method demonstrates superior performance compared to Fourier transform, principal component analysis, and least-squares PSA.
• Accurate phase retrieval is achieved even with nonuniform phase shifts.

Conclusions:

• The proposed phase measurement method offers enhanced accuracy for interferogram analysis.
• This novel PSA provides a significant advancement in optical metrology and surface characterization.
• The technique is effective for real-world applications requiring precise surface measurements.