Demodulation method based on a component synthesis and gradient projection for phase-shifting interferometry

Area of Science:

• Optical Metrology
• Interferometry
• Wavefront Sensing

Background:

• Phase-shifting interferometry (PSI) is susceptible to vibration errors, which can compromise wavefront phase demodulation accuracy.
• Traditional PSI methods often struggle with effective pixel demodulation, especially at truncated interfaces.

Purpose of the Study:

• To propose a novel demodulation method for PSI that minimizes vibration error and enhances wavefront phase demodulation accuracy.
• To improve the percentage of effectively demodulated pixels compared to conventional techniques.

Main Methods:

• A pre-processing mechanism and multi-component synthesis are employed to correct vibration errors using two interference image sequences (0, π/2 phase shift).
• Interference images are synthesized, followed by background light filtering using a gradient projection algorithm.
• Wavefront phase is demodulated via arctangent operation on the processed image data.

Main Results:

• The proposed method achieves over 90% effective pixel demodulation at the truncated interface.
• Experimental results demonstrate a significant improvement in the number of effectively demodulated pixels (demodulation accuracy) compared to traditional methods.

Conclusions:

• The component synthesis and gradient projection-based demodulation method effectively reduces vibration errors in PSI.
• This approach significantly enhances wavefront phase demodulation accuracy and the overall effectiveness of pixel demodulation in interferometric systems.