Digital Holographic Speckle Pattern Interferometry has already been developed for preventive conservation and can monitor directly the changes at the surface of artworks. The system is based on speckle interferometry with phase-shift and gives the deformation of the analysed object. The existing data process consists of removing the noise of the interferogram, unwrapping this image and deriving and displaying 2D or 3D map deformation. To improve the time duration and accuracy of data imaging treatment, we developed an easier and faster processing method. We created a denoising methodology of interference pattern generated during data acquisition based on stationary wavelet transform.
Ancient wall mosaic decorations can be exposed to uncontrolled environmental conditions. The main mosaic conservation problems, induced by external factors, are related to temperature and humidity variations, which may result in moisture, salt crystallization and accelerated material deterioration within the underlying layers. Though such deterioration in the subsurface is not immediately visible, it can strongly affect the preservation of the entire structure and the decoration layer in the short or long-term future. In this paper, we present and discuss laboratory experimental results of Digital Holographic Speckle Pattern Interferometry (DHSPI), applied to the subsurface diagnostic of a mosaic model after artificially induced thermal change and under simulated environmental conditions in climate chamber. The tests were performed on a custom-built wall mosaic model with known construction and known defects, which are simulating voids, detachments and deteriorated, restored or reshuffled areas. Two types of induced stress were used: 1) low thermal excitation emitted by IR lamps directly to the surface; 2) simulated environmental conditions inside the climate chamber. In regards of the in-situ diagnostic investigation any structural alteration occurs as a natural reaction to the surrounding environment and monitoring of surface reactions and defect detection under natural fluctuations it could be considered as a very important aspect of implementation to optimize range of applicability for non-destructive remote portable instrumentation. The obtained DHSPI results on the detection of known defects in the mosaic under artificially induced thermal alteration and under simulated environmental conditions are compared and discussed.
Cultural Heritage (CH) is concerned with objects and materials that witness the historical evolution and human civilisation and are due to be inherited to next generations. As such prevention of damage and failure is an ultimate never-ending aim in art conservation science if CH protection is concerned . Interferometry techniques offer the spatial sensitivity to assess minor changes prior to damage while important ethic principles of non destructivity, non contact and non invasive type of measurements are satisfied as basic requirements for art object examination. Visual qualitative evaluation of the state of condition as provided by interference patterns as well as the quantitative surface morphology of deformation are important information sources for the conservation documentation acting as tools in the hands of the conservator. Hence it is herein briefly described how our optical laboratory explore the trends in modern interferometric instrumentation to adjust it to the needs for documentation in Cultural heritage field. In this context the development of a portable interferometry system based on the fundamentals of holographic and speckle interferometry satisfying the limitations and over passing the state of the art in on-field measurements for structural diagnosis in CH is presented and some examples from movable and immovable artwork examination is given.
The demand for non destructive and non invasive structural diagnostic techniques able to perform on field remote structural evaluation of historical structures and works of art it faces an increased demand. The techniques must have some basic important characteristics The non destructivity, accuracy, repeatability, non physical contact, portability, resolution, broad range of applicability depending on the type of artwork and the question at hand, are all among the important requirements underlying the requirement for on-field structural diagnostics. In this respect there are two known techniques that have been developed at full to provide a suited structural diagnostic application in artwork conservation. The systems presented here but discussed in detail elsewhere are stimulated infrared thermography (SIRT) and digital holographic speckle pattern interferometry (DHSPI) the prior can be found n market at commercial devise level while the latter is at laboratory prototype level. The two systems are being exploited for their complimentary advantages and in this paper are used in combined testing on art related targets according to the above criteria to confirm the enhanced diagnostic information that their complimentary use provides. Results confirm the effectiveness of each technique alone and the combination of data of both techniques in the conservation field. Each system is first briefly described and examples are given with the aim to present the suitability and appropriateness for use in structural documentation analysis and reports. The experimental work is in laboratory work-in-progress focusing on the hybriding of data synthesis.
Environmental impact on artworks has always been a big issues for preservation of Cultural Heritage. Nowadays with the climate change it is experienced a slow but steady process of temperature increase affecting relative humidity which fluctuates while materials attempt to keep moisture balance. During repetitive equilibrium courses fatigue accumulates endangering the structural integrity prior to fracture.
Assessing the risk imposed by the fluctuation allow preventive actions to take place and avoid interventive restoration action after fracture. A methodology is presented employing full-field interferometry by surface probing illumination based on direct realtime recording of surface images from delicate hygroscopic surfaces as they deform to dimensionally respond to relative humidity (RH) changes. The developed methodology aims to develop an early stage risk indicator tool to allow preventive measures directly through surface readings.
The presented study1 aiming to experimentally highlight acclimatisation structural phenomena and to verify assumed standards in RH safety range based on the newly introduced concept of deformation threshold value is described and demonstrated with indicative results.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.