Adaptive monogenic filtering and normalization of ESPI fringe patterns

Area of Science:

• Optical Metrology
• Image Processing
• Signal Processing

Background:

• Noisy fringe patterns, common in interferometry, hinder accurate analysis.
• Single-frame demodulation techniques require pre-processed, high-quality fringe data.
• Existing filtering methods may struggle with complex patterns like closed fringes.

Purpose of the Study:

• To develop a robust technique for filtering and normalizing noisy fringe patterns.
• To enable the successful application of single-frame demodulation schemes.
• To improve the analysis of interferometric data, including Electronic Speckle Pattern Interferometry (ESPI).

Main Methods:

• An adaptive filter is constructed as a linear combination of responses from isotropic bandpass filters.
• Space-varying coefficients are determined by the envelope of each filter's response.
• The monogenic image is utilized to compute the filter response envelope.

Main Results:

• The proposed technique effectively filters and normalizes noisy fringe patterns, including those with closed fringes.
• Successful application of single-frame demodulation schemes is demonstrated on processed patterns.
• Demonstrated effectiveness on real-world Electronic Speckle Pattern Interferometry (ESPI) image patterns.

Conclusions:

• The presented adaptive filtering technique is effective for pre-processing fringe patterns for single-frame demodulation.
• This method enhances the applicability of single-frame demodulation in optical measurement systems.
• The technique shows promise for improving the analysis of noisy interferometric data, particularly ESPI.