Combined Holographic Subsurface Radar and Infrared Thermography for Diagnosis of the Conditions of Historical Structures and Artworks

This paper describes new application of holographic radar for non-destructive testing applied to cultural heritage items. A holographic radar, called RASCAN, operates at 4 GHz in continuos wave mode and produces images with high in-plane resolution (about 1 cm). Marble items and other stones have been investigated to validate the method to search for subtle cracks, moisture or to unveil details of structures at shallow depth (up to 2 wavelengths). Other important materials are aged wood items that are investigated for tunnels made by insects. Then the holographic radar imaging has been experimentally compared with infrared thermography to understand the advantages and disadvantages of these methods and to derive indications for solving the problem common in all geophysics of inherent non-uniqueness.