General information

Digital Speckle Pattern Interferometry (DHSPI)   is an optical methodology to perform Non Destructive (NDT) contactless identification, visualization, measurement and monitoring of visible as well as  hidden  defects and damages on a surface under exam. Such technique is hence capable of verifying the state of a Cultural Heritage artifact, without any contact and damage, and to identify and  study defect type, eventual growth, as well as  study deterioration mechanisms and can used for direct monitoring of the response of the system under variation of environmental conditions.

A recording on a CCD is performed of an  interferometric image  obtained with the superposition of the backscattered radiation from the surface under analysis illuminated with highly coherent TEM00 diverged laser radiation (@532nm) and the so called “reference” beam. The surface under study is displaced with respect to its “rest” position, due to a small and harmless excitation (mostly thermal, by means of Infrared Lamps): the study of the evolution with time the “partial” or spatially limited displacement or the ”whole body” system, can provide  information about the reaction and the condition of the material of the artwork. The methods allows a quantitative study of the surface under exam with  an accuracy of half the wavelength of the radiation used.

Due to its intrinsic  non destructive and contactless characteristic  such technique can be used successfully on precious Cultural Heritage artifacts and  artwork both to its structural diagnosis,  conservation state,  environmental monitoring, and identify potentially critical defect growth, as well as monitoring the effect of the restoration intervention.