Optical and digital holographic interferometry applied in art conservation structural diagnosis

Holography and holographic interferometry have emerged as new tools for conservation researchers and practitioners, and are used to visualize structural and mechanical discontinuities in the bulk of an artwork. These may be an important factor of deterioration and can be a consequence of various degradation processes, caused by environmental parameters, transportation, handling, and various conservation and restoration actions. The holographic technology is based on studies of surface reflection of diffused laser beams. No sample removal or surface preparation are necessary so that the techniques can be regarded as non-destructive, non-contact and non-invasive. The review provides an introduction to the basic principles of operation and a description of several case studies.