Subtractive two-frame three-beam phase-stepping interferometry for testing surface shape of quasi-parallel plates.

Area of Science:

• Optical Metrology
• Surface Metrology
• Interferometry

Background:

• Accurate surface shape testing is crucial for optical component manufacturing.
• Traditional interferometric methods can be complex and sensitive to environmental factors.

Purpose of the Study:

• To develop an effective and robust method for testing the surface shape of quasi-parallel plates.
• To simplify surface shape analysis by reducing the number of required interferograms.

Main Methods:

• Derivation of a general formula for the difference between two phase-shifted three-beam interferograms.
• Utilizing two phase-shifted three-beam interferograms for surface shape analysis.
• Comparison of fringe extraction and phase distribution analysis using 2D Continuous Wavelet Transform, Hilbert-Huang Transform, and Fourier Transform methods.

Main Results:

• An effective method for surface shape testing of quasi-parallel plates was demonstrated.
• The method requires only two phase-shifted three-beam interferograms.
• Phase shifts do not require precise determination or uniformity across the image.
• Simulated and experimental data confirmed the algorithm's performance and robustness.

Conclusions:

• The proposed interferometric method offers an efficient and robust approach for quasi-parallel plate surface testing.
• The technique simplifies data acquisition and processing compared to conventional methods.
• The algorithm's reliability is validated through comprehensive testing.