Abstract
Artworks have a layered structure subjected to alterations caused by various factors. The monitoring of defects at sub-millimeter scale may be performed by laser interferometric techniques. The aim of this work was to develop a compact system to perform laser speckle imaging in situ for effective mapping of subsurface defects in paintings. The device was designed to be versatile with the possibility of optimizing the performance by easy parameters adjustment. The system exploits a laser speckle pattern generated through an optical diffuser and projected onto the artworks and image correlation techniques for the analysis of the speckle intensity pattern. A protocol for the optimal measurement was suggested, based on calibration curves for tuning the mean speckle size in the acquired intensity pattern. The system was validated in the analysis of detachments in an ancient painting model using a short pulse thermal stimulus to induce a surface deformation field and standard decorrelation algorithms for speckle pattern matching. The device is equipped with a compact thermal camera for preventing any overheating effects during the phase of the stimulus. The developed system represents a valuable nondestructive tool for artwork diagnostics, allowing the monitoring of subsurface defects in paintings in out-of-laboratory environment.
Highlights
Artworks are subjected to structural alterations induced by various factors such as aging, microclimatic conditions and conservation treatments
The goal of this work was to propose an effective system for laser speckle pattern imaging of artworks
The developed prototype and the proposed optimal measurement protocol were validated in a typical context of artwork diagnostics by carrying out the experiment on a model of ancient painting with known hidden defects
Summary
Artworks are subjected to structural alterations induced by various factors such as aging, microclimatic conditions and conservation treatments. Ancient paintings present a complex layered structure that is susceptible to surface and subsurface decay, such as cracks, delaminations and detachments The monitoring of such “defects” at small scale (sub-millimeter) is one of the objectives of nondestructive testing techniques applied to the conservation field [1,2]. The drawback of interferometry, generally speaking, is its sensitivity to external vibrations, which makes achieving the optimal measurement conditions without controlled laboratory settings difficult. This issue and the requirement of optics-skilled operators represent the major obstacle for a widespread use of such technique in the routine diagnostics of artworks. More flexible interferometry-based techniques are represented by the speckle-based methods [5], such as Electronic Speckle Pattern Interferometry (ESPI)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
