A Portable Compact System for Laser Speckle Correlation Imaging of Artworks Using Projected Speckle Pattern

Area of Science:

• Art conservation science
• Optical metrology
• Non-destructive testing

Background:

• Artworks possess complex layered structures susceptible to degradation.
• Sub-millimeter scale defect monitoring is crucial for artwork preservation.
• Traditional laser interferometric techniques can be adapted for defect detection.

Purpose of the Study:

• To develop a compact, in situ laser speckle imaging system for mapping subsurface defects in paintings.
• To create a versatile device with adjustable parameters for optimized performance.
• To provide a non-destructive diagnostic tool for artwork analysis outside laboratory settings.

Main Methods:

• Utilized laser speckle pattern generation via an optical diffuser projected onto artworks.
• Employed image correlation techniques for analyzing speckle intensity patterns.
• Developed a measurement protocol based on calibration curves for speckle size tuning.
• Validated the system on an ancient painting model with induced detachments using thermal stimulus and decorrelation algorithms.

Main Results:

• Successfully demonstrated in situ mapping of subsurface defects (detachments) in a painting model.
• The system's versatility allows for easy parameter adjustment and performance optimization.
• A protocol for optimal measurement, including speckle size tuning, was established.
• Integrated thermal camera ensured no overheating during thermal stimulus application.

Conclusions:

• The developed compact laser speckle imaging system is a valuable non-destructive tool for artwork diagnostics.
• It enables effective in situ monitoring of subsurface defects in paintings.
• The system is suitable for out-of-laboratory environments, advancing art conservation efforts.