Combination of oriented partial differential equation and shearlet transform for denoising in electronic speckle...

Area of Science:

• Optical Metrology
• Image Processing
• Interferometry

Background:

• Speckle noise in Electronic Speckle Pattern Interferometry (ESPI) fringe patterns significantly degrades measurement accuracy.
• Existing spatial-domain (e.g., oriented partial differential equations) and transform-domain (e.g., shearlet transform) filtering methods have limitations in effectively removing this noise.

Purpose of the Study:

• To propose and evaluate a novel hybrid filtering method for denoising ESPI fringe patterns.
• To leverage the complementary strengths of spatial and transform-domain filtering techniques for improved noise reduction.

Main Methods:

• A new filtering technique, SOOPDE-Shearlet, is developed by combining second-order oriented partial differential equation (SOOPDE) and the shearlet transform.
• The shearlet transform is applied to ESPI fringe pattern denoising for the first time within this hybrid framework.
• The proposed method was tested on experimentally acquired, low-quality ESPI fringe patterns.

Main Results:

• The SOOPDE-Shearlet method demonstrated superior performance in denoising ESPI fringe patterns compared to individual SOOPDE, shearlet transform, windowed Fourier filtering (WFF), and coherence-enhancing diffusion (CEDPDE).
• Experimental results validated the effectiveness of the combined approach in preserving fringe pattern details while reducing speckle noise.

Conclusions:

• The SOOPDE-Shearlet method offers a significant advancement in ESPI fringe pattern denoising.
• This hybrid approach effectively mitigates speckle noise, paving the way for more accurate and reliable interferometric measurements.