Development of impact assessment procedure and preliminary results with digital holographic speckle pattern interferometry for signatures multi-encoding use

Abstract

The deterioration of cultural heritage is of major concern for gallery conditions and loan considerations worldwide. Artwork deterioration may increase during transportation and exhibitions or mishandling. Decisions about gallery conditions and loan requirements shall need reconsideration if findings based on artworks undergoing these procedures prove that impose catastrophic dimensional fluctuations. In this context, non interacting and non contact methods are useful in order to monitor the continuous changes in the monitored artwork. The presented paper refers to this application of high importance for the preservation of cultural heritage and forms part of the European project Multiencode (006427 SSPI). Holography techniques, in either optical and digital acquisition, are known to allow full field observation of object point's displacement. In addition to the importance provided by the techniques of revealing hidden discontinuities within an object, the procedures that have been developed which can be used to visualize and study deformations following environmentally induced alterations are similarly important. The interferometric formation which results in fringe patterns which correspond to hidden defects can be used as a key-indicator to control and monitor accidental or intentional interventions which may effect an object and hence result in an alteration of the originally-revealed fringe pattern information. Thus, in this paper the specific steps taken to develop an Impact Assessment Procedure for the assessment and evaluation of the fringe pattern alterations deduced by the implementation of a Digital Holographic Speckle Pattern Interferometry(DHSPI) system is presented and examples of the application are given.