Holographic monitoring of transportation effects on canvas paintings

Digital holographic speckle pattern interferometry is used to locate areas at risk of deterioration in paintings due to vibration

SYDDARTA: new methodology for digitization of deterioration estimation in paintings

ABSTRACT The SYDDARTA project is an on-going European Commission funded initiative under the 7th Framework Programme. Its main objective is the development of a pre-industrial prototype for diagnosing the deterioration of movable art assets. The device combines two different optical techniques for the acquisition of data. On one hand, hyperspectral imaging is implemented by means of electronically tunable filters. On the other, 3D scanning, using structured light projection and capturing is developed. These techniques are integrated in a single piece of equipment, allowing the recording of two optical information streams. Together with multi-sensor data merging and information processing, estimates of artwork deterioration and degradation can be made. In particular, the resulting system will implement two optical channels (3D scanning and short wave infrared (SWIR) hyperspectral imaging) featuring a structured light projector and electronically tunable spectral separators. The system will work in the VIS-NIR range (400-1000nm), and SWIR range (900-2500nm). It will be also portable and user-friendly. Among all possible art work under consideration, Baroque paintings on canvas and wooden panels were selected as the project case studies

Fully-Non-Contact Masking-Based Holography Inspection on Dimensionally Responsive Artwork Materials

Environmental control in galleries and museums is a necessity and is informed by the knowledge of ongoing processes of deterioration which can threaten the integrity and stability of artworks. Invisible dimensional changes in many works of art occur following environmental fluctuations as materials respond to the changes in humidity and temperature. The constant influence of dimensional changes usually remains invisible until displacement generates visible deterioration and irreversible damage. This paper exploits fully non contact coherent interferometry in a sequential masking procedure for visualising and studying surface deformation which is the direct effect of dimensional alterations induced by humidity changes. Surface deformation during dimensional displacements of constituent materials may occur on any artwork within an unstable environment. In this context, the presented research study explores the diagnostic potential of fully non contact sensors for the direct structural assessment of environmental effects as they occur in real time on works of art. The method is employed to characterise material responses, complementing and improving understanding of material behaviour in unstable environments

Holographic Interference: Structural Deformation Detection Applied to Cultural Heritage Objects

Interference is a fundamental physical phenomenon proving the wave nature of energy. It is based on wave superposition forming natural waveeffects expressed both in nature under random selective conditions as well as in laboratory scientific experiments by carefully controlled selection of parameters. Science generates a number of technology applications using the inherited properties of waves after their superposition in space termed interference. These interfering waves have extremely rare properties compared to their initial physical systems and become entities with measurable quantities which can be used to quantify qualities in other phenomena, mechanisms, and physical objects with variety of physical properties. These waves are currently fully explored in theoretical and experimental physics finding many modern applications and enlightening the way to longstanding questions. Remote non contact study of surfaces and their reactions visually witnessing internal subsurface and unknown bulk information without need to implement destructing forces or penetrating irradiation to trace them and without interacting with it or interfering with the results is one of the most challenging modern applications of interference physics. Apart from everyday life applications artworks’ conservation is a field that interference properties are uniquely suited. It is the quality of light wave interference that is being utilised in this body of research and summarised in the present thesis. The context of the presented thesis unfolded in next chapters is constructed in one book on a contextual rather than chronological order. The contextual base presentation is achieved through clustering same context published articles that have resulted over the course of years of research which have been published in review journals, conference proceedings or governmental publications. The formation of laser interference fringe patterns and their exceptional qualitites in application for structural diagnosis with defect detection and definition, their unique properties utilised in studies of environmental and climate effects, the prototype optical geometries and novel experimental methodologies envisaged to solve specific application problems are presented along with examination on theoretical matters of exploring interference properties, qualities, geometries and their outmost final product the interference fringe pattern. Thus in this thesis the aim is to prove the contribution of the experimental research publications to the study of interference patterns as a highly sophisticated structural diagnostic tool in the complicated problems of Cultural Heritage applications. The implementation of interference phenomena and the development in experimental investigations applied in inhomogeneous, anisotropic, shape variant, multilayered, multicomposition cultural heritage objects, paves the way to implement “fringe patterns” as a scaleless (scale independent) diagnostic detector allowing generation of novel tools and practices on problem solving projects. The developments are beyond the specific application and are extended to other fields of science and technology. The articles and bibliography cited within the text including author's publications utilised as sources in the writing of this thesis are referenced in square brackets and are explicitly listed in ANNEX I The list of publications of the author is shown in ANNEX II. The originals of author's publications supporting the thesis are provided after the Annex II as have been published. Due to limitation in number of pages there is not included a section to present the fundamental principles of the phenomena presented here instead a list of books commonly found in most University libraries is provided for interested readers as BIBLIOGRAPHY at the last paragraphs of ANNEX I

Interferometric Quantification of the Impact of Relative Humidity Variations on Cultural Heritage

It has been shown that Relative Humidity (RH) provokes dimensional displacement detectable directly from surfaces using holographic interferometry. RH variations constitute a physical environmental load that drives organic materials to a constant equilibrium cycle. This paper is a small synopsis of the interferometric research direction and a data acquisition on the detection of the dimensional impact of relative humidity on cultural heritage objects. Since RH cycling is unavoidable, the interferometric data change depends on the object structure and RH cycle characteristics. Based on the fact that each artwork is by construction unique, and on the observation that the effects of an RH cycle on the structural condition of any artwork are also unique but the preventive conservation strategies require generalised approaches and not on a case-by-case study, being introduced is a novel, universal, preventive deterioration methodology: “deformation threshold value” (DTV). DTV is assignable to each distinct object in order to control routinely its structural condition and prevent damage. DTV is not assigned hypothetically based on any assumed/expected reactions but from a monitored calibration of the artwork in its environment. Each artwork in its hosted environment has its unique reaction. The reaction, though, is not steady but changes as the artwork changes. DTV can be acquired routinely and valued accordingly to seasonal RH change. Monitoring the seasonal RH and seasonal dimensional reaction has been shown to correspond to a standard DTV pattern whose deviations violate the expected seasonal reaction. Through the interferometric monitoring of surface, the distinct DTV acts as a safeguard for the artwork. In this synopsis, some results of the generation of DTVs are shown. Our future plan is for the DTV numbers to serve as data inputs for preventive models to formulate a distinct risk index representative of each artwork condition and to be used as remote risk warning to prevent its deterioration. Based on the DTV concept, methods and instruments for sequential data acquisition aim to present experimental data outputs as DTVs that identify transient shape changes prior to visible damage have been developed. In this research, the starting point was the interferometric quantification of the displacement of well-characterized fresh samples. The fresh samples are known in terms of density, cut, thickness, moisture content, structural condition and are submitted to RH simulation cycles. Shown here are three exemplary cases: usual, abrupt and smooth. The interferometric monitoring following the cycles of RH is a long-term duration of several weeks; measurements are performed directly from the surface, and relative displacement (RD) from temporal measurements of interference fringes provide the required output data to calculate the rate of displacement (RoD) of the surface. Measuring the impact of RH directly from the artwork surface allows the detection of the temporal diversity of structural reactions to the same RH cycle for distinct artworks. The monitoring system uses interferometric precision provided by digital holographic speckle-pattern interferometry (DHSPI) placed on a specially designed climate chamber DHSPI monitoring workstation

Wall Mosaics: A Review of On-Site Non-Invasive Methods, Application Challenges and New Frontiers for Their Study and Preservation

This review concerns the challenges and perspectives of on-site non-invasive measurements applied to wall mosaics. Wall mosaics, during the centuries, decorated numerous buildings, nowaday being part of world cultural heritage. The preservation and maintenance of these valuable decorations are undoubtedly directly dependent on identifying possible problems that could a\ufb00ect their hidden structure. On-site non-invasive methods, using di\ufb00erent contact or no-contact technologies, can o\ufb00er support in this speci\ufb01c \ufb01eld of application. The choice of the appropriate technique or combination of di\ufb00erent techniques depends, in general, on the depth of investigation, the resolution, the possibility to have direct contact with the surfaces or, on the contrary, limited accessibility of the wall mosaics due to their location (e.g., vaults), as well as deterioration problems, (e.g., voids, detachments, or humidity e\ufb00ects). This review paper provides a brief overview of selected recent studies regarding non-invasive methods applied to the analysis of wall mosaics. This review, discussing the assessment of advantages and limitations for each method here considered, also considers possible future developments of imaging techniques in this speci\ufb01c context for cultural heritage applications

Fully-Non-Contact Masking-Based Holography Inspection on Dimensionally Responsive Artwork Materials

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Study of Crack Growth of Transparent Materials Subjected to Laser Irradiation by Digital Holography

The crack growth of transparent materials after laser wavelength irradiation was studied. It is known that laser irradiation is used in many applications for the ablation of undesired material and/or coatings. The impact of laser irradiation on cracks was studied using the digital holography (DH) technique. Transparent samples were irradiated using near-ultraviolet, visible, near-infrared, and infrared light. The DH system is able to detect cracks and crack growth of the transparent samples irradiated by a range of laser wavelengths. Results also show that light with infrared to near-infrared wavelengths has a great effect on crack growth. High-resolution photomechanical effects of laser irradiation on material expansion or/and generation of defects due to specific wavelengths are also illustrated. The DH system with a multispectral laser has practical applications for laser cleaning of painted artworks