Measurement of random processes at rough surfaces with digital speckle correlation.

Area of Science:

• Optics and Photonics
• Materials Science
• Surface Metrology

Background:

• Understanding surface microstructure changes is crucial for material integrity.
• Scattering of light from rough surfaces is a complex phenomenon.
• Existing methods for measuring microstructural changes can be limited in scope or resolution.

Purpose of the Study:

• To investigate digital speckle correlation for quantifying small changes in random rough surface microstructures.
• To develop a theoretical model linking speckle correlation to surface microstructure parameters.
• To experimentally validate the theoretical model using fabricated surfaces and advanced measurement techniques.

Main Methods:

• Digital speckle correlation was employed to analyze alterations in the scattered-light field.
• A composite-roughness model was used to theoretically predict speckle correlation based on microstructure parameters.
• Photolithography was used to fabricate surfaces for experimental verification.
• High-resolution scanning force microscopy and correlation measurements were performed under varied experimental conditions.

Main Results:

• A good agreement was observed between theoretically predicted and experimentally obtained speckle correlation data.
• The study demonstrates the capability of digital speckle correlation to detect subtle microstructural modifications.
• The results confirm the validity of the composite-roughness model for this application.

Conclusions:

• Digital speckle correlation is a reliable method for quantitative, whole-field monitoring of surface microstructure changes.
• The developed theoretical framework accurately predicts experimental observations.
• This optical technique offers a non-contact, remote sensing approach for analyzing surface processes.