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

Tornari, Vivi; Bernikola, Eirini; Nevin, Austin; Kouloumpi, Eleni; Doulgeridis, Michalis; Fotakis, C.

doi:10.3390/s8128401

Cited by 24 publications

(24 citation statements)

References 29 publications

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“…by vibration, has been described. The normal temperature and humidity variations can result in significant deformations that are exploited in ambient loading [169].…”

Section: Holographic and Speckle Methodsmentioning

confidence: 99%

Mobile depth profiling and sub-surface imaging techniques for historical paintings—A review

Alfeld

Broekaert

2013

Spectrochimica Acta Part B: Atomic Spectroscopy

114

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“…by vibration, has been described. The normal temperature and humidity variations can result in significant deformations that are exploited in ambient loading [169].…”

Section: Holographic and Speckle Methodsmentioning

confidence: 99%

Mobile depth profiling and sub-surface imaging techniques for historical paintings—A review

Alfeld

Broekaert

2013

Spectrochimica Acta Part B: Atomic Spectroscopy

114

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“…The optical geometry of the DHSPI system is designed according to the strict boundary conditions for optical off-axis transmission holography in double exposure phase-shifted holographic interferometry mode of application (DE psHI). The geometry of the portable instrument is shown in Figure 2 and development is described in detail elsewhere [21,22,34]. A hologram was recorded every given time interval ∆t and the phase ϕ i of each hologram was extracted; the subtraction of two consecutive phases gives a phase difference ∆ϕ i , which is directly linked with the displacement occurred during ∆t.…”

Section: Optical Geometrymentioning

confidence: 99%

Impact of Relative Humidity on Wood Sample: A Climate Chamber Experimental Simulation Monitored by Digital Holographic Speckle Pattern Interferometry

et al. 2019

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Relative humidity (RH) changes are a natural environmental effect that forces organic materials to a constant cycle of achieving equilibrium. The present work is part of an ongoing research based on the hypothesis that the inevitable deleterious effects of the RH natural cycle may be prevented or minimized if a deformation threshold is assigned to each monitored endangered object prior to exposure to structural damage. In this paper the characterization of the behavior of a softwood sample (1.0 cm thick) submitted to RH abrupt cycles has been performed, in terms of mass and rate of displacement of the surface. The exemplary study is based on the concept of recording the RH impact directly from the material surface, allowing us to identify diversity in reaction with time, which in turn could determine the onset of structural changes prior to irreversible damage. The RH impact is measured as surface deformation from interference fringes, using a custom-made real time holography system with interferometric precision termed digital holographic speckle-pattern interferometry (DHSPI). The main observations presented here are a hysteresis in the dynamic sorption isotherm and a greater rate of displacement during the drying. A long-term experiment was performed to identify signs of ageing of the sample. The evolution of the mass and the rate of displacement stayed similar, an offset with an interesting behavior was observed and highlights ageing of wood. In order to produce a future preventive model for distinct art objects it is necessary to determine a deformation threshold for each material. In this context the study was planned to continue with organic samples bearing variable density and thickness under longer-term RH cycles and monitoring until the samples show visible signs of irreversible damage.

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“…In this context, surface displacement is essential to occur within controlled time and load in order to produce an excitation which changes the spatial characteristics of the surface. To provide controlled induced excitation, two infrared lamps of 500 mW each are placed in front of the surface on 60° each from the vertical to the surface . The distance depends on object dimensions with the aim to cover the full surface providing homogeneous distribution of thermal energy.…”

Section: Optical Characteristics Of the Systemmentioning

confidence: 99%

On development of portable digital holographic speckle pattern interferometry system for remote‐access monitoring and documentation in art conservation

Tornari

2018

Strain

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Artworks are delicate objects representative of the most high values of human kind that require constant control over the situation they are in and effective actions to preserve them and deliver them safely to next generations. As such, the non‐destructive or minimally destructive nature of operator–artwork interactions has been considered as essential in this field. The complete diagnosis of the status of the art object signifying a full knowledge of invisible defects and their morphology allows its timely and correct maintenance and ensures its durability. It is herein presented the basic technical information on the development of a portable system termed Digital Holographic Speckle Pattern Interferometry (DHSPI) for the structural diagnosis of works of art. DHSPI has been tested on a variety of conservation problems over the years. It is a completely portable and fully PC driven automated system for the detection and non‐destructive diagnosis of the structural alterations of an artwork, whether they are defects lying on the subsurface or between the layers below it, the fringe number information allows the depth estimation and the complete documentation. The system exploits the benefits of a highly coherent laser beam as essential presupposition for remote on‐field access—that is the main emphasis given here—to immovable/movable art objects. It takes advantage of a CCD camera as photosensitive medium to record the interference of the retro reflected object laser beam from the object under consideration with a twin reference laser beam. The device allows micro projections of the defects on the surface of the object to be detected with a resolution that corresponds to half the wavelength of the laser beam. Local disparities, in relation to the total response of the object, are directly correlated to the detected microdisplacement of object surface as structural defects. Special tailor‐made software allows full control of the system, processing of the data, and extraction of anomalies. Direct visual qualitative observation of the displacement processes is followed as captured in the monitor. A second custom‐made software—not presented in detail here—enables further processing of the results to improve their imaging, quantification, and dimensioning. The final result is a quantitative map of alterations, the coordinates, and the classification of their risks which can be also extracted if further information is necessary. The qualitative or quantitative documentation map can be used as a guide to the conservator for maintenance and restoration work. Further on, the system also allows observation of the object's response to climate changes in order to predict the formation of alterations or the evolution of existing ones providing the only known direct tool for scheduling preservation strategies.

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

Cited by 24 publications

References 29 publications

Mobile depth profiling and sub-surface imaging techniques for historical paintings—A review

Mobile depth profiling and sub-surface imaging techniques for historical paintings—A review

Impact of Relative Humidity on Wood Sample: A Climate Chamber Experimental Simulation Monitored by Digital Holographic Speckle Pattern Interferometry

On development of portable digital holographic speckle pattern interferometry system for remote‐access monitoring and documentation in art conservation

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