The Optics for Arts, Architecture and Archaeology Conference, 8th under O3A series and 10th since its conception, is being held again in Munich as part of the SPIE Optical Metrology Symposium at the World of Photonics Congress in June 2021. We are proud to celebrate 20 years of this optics community in 2021.

O3A is an established event for discussing advanced methods and new instruments for the historical study, conservation and documentation of cultural heritage. The symposium is a unique forum focused on optics research in the field of heritage science. Optics applications in cultural heritage has a long and dynamic history owing to the non-destructive nature of optical imaging starting with microscopy, infrared photography and X-radiography. Optical imaging provided the most popular methods of examination for cultural heritage before micro-chemical analysis became possible. In recent years, the development of new imaging and spectroscopic techniques have revitalized the application of optics in cultural heritage. The non-invasive nature of these techniques has meant that whole objects and collections can now be examined with multiple techniques which will inevitably result in unprecedented amount of data collected that will in turn push new boundaries in data and image processing methods. The demand of the developing European Research Infrastructure for Heritage Science (www.e-rihs.eu) for news instruments, data processing methods and facilities will no doubt advance the field even further.

The 2021 symposium will cover instruments and techniques that span the entire electromagnetic spectrum covering a broad range of scales along with the associated data and image processing and visualization methods. New instruments and techniques, multi-modal imaging and multi-technique integrated analysis and data fusion techniques that meets the challenges of big data analytics are expected to be the focus.

Contributions are welcome and will be considered in all fields of research for cultural and natural heritage including the following areas of interest:

  • 3D topographic scanning, surface examination and analysis (e.g. RTI, structured light and other imaging and triangulation based methods, optical profilometry etc.)
  • 3D tomographic imaging, stratigraphic and depth resolved methods (e.g. optical coherence tomography, non-linear microscopy, terahertz imaging, micro-CT etc.)
  • structural analysis (e.g. holography and other interferometric techniques)
  • imaging and spectroscopy for material analyses (e.g. the various spectral imaging modalities such as reflectance imaging from UV to infrared, fluorescence imaging and fluorescence lifetime imaging, laser induced breakdown spectroscopy, laser induced fluorescence and Raman spectroscopy, X-ray imaging, synchrotron based techniques etc.)
  • temote imaging, sensing and spectroscopy at large stand-off distances including drone based methods
  • new portable instruments for in situ applications
  • multimodal imaging and multitechnique analysis
  • multiscale and multiwavelength imaging for structural and material analysis
  • light-matter interactions (e.g. fundamentals of laser interactions with materials, light induced material degradation, including those used for the illumination and excitation in the various techniques)
  • advanced image processing methods including artificial intelligence and machine learning method to tackle big data problems
  • new data visualization methods
  • new methods and applications to cultural heritage research.

  • The symposium will be an ideal forum to introduce new applications, to exchange ideas and to discuss methods and best practices for optics applied to heritage science. The World of Photonics Congress offers a perfect opportunity for instrumentalists to engage with industry finding out the latest developments in sensor technology and optical components at the accompanying exhibition. Senior researchers, early career researchers, and students are encouraged to participate.;
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    Conference 11784

    Optics for Arts, Architecture, and Archaeology (O3A) VIII

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    • DIgital Optical Technologies Plenary Session
    • Special Focus: Keynote Session I
    • Special Focus: Keynote Session II
    • FET-Open on Disruptive Ideas and Optical Technologies for Health I
    • Special Focus: Keynote Session III
    • Optical Metrology Plenary Session
    • FET-Open on Disruptive Ideas and Optical Technologies for Health II
    • 1: Machine Learning and Data Visualisation
    • 2: Imaging and Spectroscopy Instrument and Method Development
    • 3: Deformation and Structural Analysis
    • 4: Light-Matter Interaction
    • 5: 3D Tomography
    • 6: Ground-based and Airborne Remote Imaging and Spectroscopy
    • 7: Applications to Art, Archaeology, Architecture and Anthropology
    • 8: Multimodal Imaging and Spectroscopy
    • 9: 3D Surface Analysis
    • Poster Session
    Session LIVE: DIgital Optical Technologies Plenary Session
    Livestream: 21 June 2021 • 12:30 - 13:30 CEST | Zoom
    11788-600
    Author(s): Hiroki Kikuchi, Sony Corp. (Japan)
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    Sony is leveraging its "3R Technology" - Reality, Real-time, and Remote - to inspire Kando (emotion) value creation. Immersive, large-screen displays give us a sense of reality as if we are traveling around the world while we're at home. Sensors for automotive provide real-time feedback to the drivers to provide safety and comfort. AR/MR/VR technology connects people who are separated remotely and enriches their communication. Photonics is one of the core technologies of Sony and is the foundation of the core devices which create the values of Reality, Realtime and Remote. In this talk, Sony's unique photonic device technologies are introduced, including micro-display, AR/MR/VR, light field displays and laser devices. The prospects for the evolution of these technologies will also be presented.
    Session LIVE: Special Focus: Keynote Session I
    Livestream: 21 June 2021 • 14:15 - 15:45 CEST | Zoom
    11786-33
    Author(s): Adam P. Wax, Duke Univ. (United States)
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    OCT adoption is somewhat limited by the lack of an effective means for obtaining adequate image penetration in highly scattering tissue. For example, the ability to observe subtle changes in the layers of skin tissue where microcirculation occurs, generally anywhere between 1-4 mm deep, a depth currently beyond the penetration of traditional OCT systems. DA-OCT presents an attractive potential to image deeper into tissues exposing morphology that otherwise may go undetected. The approach is based on an off-axis scanning approach which uses distinct illumination and collection apertures to accept a larger proportion of quasiballistic signal. Here we present transliation ofDA-OCT to image large tissue volumes using a broadband SLD centered about 1.3 μm paired with a dynamic focus-tracking method to create an enhanced depth of focus.
    11788-1
    Author(s): Frederik Bachhuber, Olaf Claussen, Zhengyang Lu, Clemens Ottermann, Simone Ritter, Bianca Schreder, Ruediger Sprengard, Stefan Weidlich, Ute Woelfel, SCHOTT AG (Germany)
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    Waveguide technology is widely believed to constitute the most promising approach to realize affordable and fully immersive Augmented Reality (AR) / Mixed Reality (MR) devices. For all major technology platforms (diffractive, reflective, or holographic), specialty grade high index optical glass is the central component to achieve some of the key features of AR devices, such as field of view, MTF, or weight. We will provide insights into SCHOTT’s roadmap for dedicated glass development for the AR sector and discuss the latest achievement with high relevance for the industry. It is a game of trade-offs between the desired properties to produce an optical glass which enables the entry of AR devices into the consumer market.
    Session LIVE: Special Focus: Keynote Session II
    Livestream: 22 June 2021 • 08:30 - 10:15 CEST | Zoom
    11782-14
    Author(s): Saoucene Hassad, Lab. d'Acoustique de l'Univ. du Maine, CNRS (France); Kouider Ferria, Larbi Bouamama, Univ. Ferhat Abbas Sétif 1 (Algeria); Pascal Picart, Lab. d'Acoustique de l'Univ. du Maine (France)
    On demand
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    Data acquisition and processing is a critical issue for high-speed applications especially for three-dimensional imaging and analysis. Digital holographic tomography is a potential approach that can quantitatively measure the three-dimensional distribution of the refractive index of any phase object or transparent specimen. Generally, tomography is operated by acquiring projections of the sample and numerically mapping those projections onto a 3D representation using an inverse problem, such as the filtered back projection algorithm. From the practical point of view, there are mainly two ways for recording the data. First, the set of data can be acquired when varying the illumination angle. Last, the data can be acquired by the sample rotation. In both approaches, the sample and the optical set-up must be highly stationary whereas the illumination beam or the object is rotated. Another option is to simultaneously acquire the necessary set of data with a single shot acquisition and then to process them. This would have for advantage of permitting 3D imaging of non-stationary targets or transient time-varying object. The use of multiple camera sensors is complicated and not cost efficient. So, this paper presents the proof of concept for a novel approach based on three color digital holography and the use of a single monochromatic sensor. The principle is based on off-axis holography and spatial multiplexing of multi-wavelength holograms. Three wavelengths from three different laser lines are used to illuminate the target at different incidence angles. The reference beams from the lasers are combined into a single three color beam and the spatial frequencies of the reference waves are adjusted so as to allow for the spatial multiplexing of digital holograms with the monochromatic sensor. After de-multiplexing and processing the color holograms, the amplitude and phase of the target along the views are obtained. Further processing in order to compensate for aberrations of the set-up are proposed and discussed. As proof of concept, we provide results for 3D shape of a 3D ball reconstructed using the inverse Radon transform. These first results are adequate to be exploited in the study of the acoustic field of an ultrasound transducer, for a frequency of 40Khz.
    11785-34
    Author(s): Byoungho Lee, Youngjin Jo, Dongheon Yoo, Juhyun Lee, Seoul National University (Korea, Republic of)
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    Near-eye displays (NEDs) for augmented and virtual reality (AR/VR) are spotlighted because they have a possibility to provide much more immersive experiences never possible before. With the virtue of recent progress in sensors, optics, and computer science, several commercial products are already available, and the consumer market is expanding rapidly. However, there are several challenging issues for AR and VR NEDs to become closer to our lives. Here, we will explore these issues and important topics for AR and VR, and introduce some of the ideas to overcome them: diffractive optical elements (DOEs), retinal projection displays, and 3D display with focus cues. First, unlike VR with a simple optical system, AR that needs to merge an artificial image with an outer scene requires additional optics. The diffractive elements have the merit of being thin and transparent, suitable for the image combiner. Among them, holographic optical elements (HOEs) have great potential as they can record the desired volume grating from the simple lens to the complex wavefront using light interference. Second, in order to wear the NEDs for a long time, it must deal with the visual fatigue as well as the form factor. Retinal projection display can effectively prevent the vergence-accommodation conflict problem even with a simple optical design. In the retinal projection display, the light rays from the display are adjusted to converge into a small point using a lens. It ensures a wide depth range in which the images are clearly visible. Furthermore, it is possible to provide observers with accurate focus cues for the alleviation of visual fatigue via multi-layer displays and holographic displays. Recently, we conceived tomographic NED that can reproduce dense focal planes. We confirm that this system provides quasi-continuous focus cues, semi-original contrast, and considerable depth of field. The experimental results of our prototypes are explained. We also explain the recent activities of using deep learning in holographic NED system.
    11784-7
    Author(s): Claudia Conti, CNR-Istituto di Scienze del Patrimonio Culturale (Italy); Alessandra Botteon, Istituto di Fisica del Plasma "Piero Caldirola", Consiglio Nazionale delle Ricerche (Italy); Christopher Corden, Ioan Notingher, The Univ. of Nottingham (United Kingdom); Pavel Matousek, STFC Rutherford Appleton Lab. (United Kingdom)
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    Recent advances on micro Spatially Offset Raman Spectroscopy (micro-SORS), an optical spectroscopy method able to non-invasively investigate at the microscale the molecular composition of the subsurface of turbid materials, will be presented. The recent research topics include the application of micro-SORS to non-invasively reconstruct the diffusion profiles of conservation treatments applied in calcium-based matrices, the first in-situ surveys of prestigious panel paintings with a portable micro-SORS prototype derived modifying a commercial portable Raman spectrometer, and proof-of-concept experiments performed coupling micro-SORS with Time-Gated Raman Spectral Multiplexing method for the non-invasive suppression of the fluorescence originated by the subsurface.
    Session LIVE: FET-Open on Disruptive Ideas and Optical Technologies for Health I
    Livestream: 22 June 2021 • 11:00 - 12:50 CEST | Zoom
    11786-57
    From FET to EIC-Pathfinder (Invited Paper)
    Author(s): Ioannis Fiamegkos, European Innovation Council and SMEs Executive Agency (EISMEA) (Belgium)
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    The European Innovation Council (EIC) is Europe's flagship innovation programme aiming to identify, develop and scale up breakthrough technologies and game changing innovations. EIC has been established under the EU Horizon Europe programme and It has a budget of €10.1 billion. The aim is to support game changing innovations from early stage research, to proof of concept, technology transfer, and the financing and scale up of start-ups and SMEs. The EIC takes a pro-active approach to managing funding by developing the visions for innovation and technology breakthroughs and by steering the portfolios of projects to achieve these goals. In this new environment the well-known FET is transformed to EIC Pathfinder (with the Pathfinder Open and Pathfinder Challenges calls) aiming to develop a diverse portfolio of targeted projects that explore wide-ranging technological potential, inspired by cutting-edge science, unconventional collaboration and innovative practices. Grants of up to 3 to 4 million euros support early stage development of future technologies (e.g. various activities at low Technology Readiness Levels 1-3), up to proof of concept. Pathfinder projects can also receive additional funding for testing the innovation potential of their research outputs.
    11786-58
    Author(s): Romina Rega, Martina Mugnano, Danila del Giudice, Simona Itri, Volodymyr Tkachenko, Veronica Vespini, Sara Coppola, Pietro Ferraro, Istituto di Scienze Applicate e Sistemi Intelligenti (Italy); Heidi Ottevaere, Yunfeng Nie, Vrije Universiteit Brussel (Belgium); Sanna Uusitalo, VTT Technical Research Centre of Finland (Finland); Reinhard Schwoediauer, Martin Kaltenbrunner, University of Linz (Austria); Markku Känsäkoski, Ginolis (Finland); Emanuela Mazzon, IRCCS Bonino Pulejo (Italy); Pier Luca Maffettone, Gaetano D'Avino, University of Naples (Italy); Simonetta Grilli, Istituto di Scienze Applicate e Sistemi Intelligenti "Eduardo Caianiello" (Italy)
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    The goal of SensApp FET-Open project is to develop an innovative super-sensor that will be able to detect Alzheimer’s disease (AD) biomarkers (β-amyloid, Tau and pTAU) in peripheral blood. Considering that nowadays an accurate diagnosis of AD requires the highly invasive withdrawal and analysis of cerebrospinal fluid, SensApp will represent a breakthrough in the field of AD diagnosis thanks to the ability to detect the early stage of the disease by a simple blood collection. We call Droplet-Spilt-and-Stack (DSS) the new technology that will emerge from SensApp. The achievement of SensApp goal will be insured by the interdisciplinary cooperation between different research institutions and one company involved in the key fields of the project, Vrije University of Brussels, VTT Technical Research Centre of Finland, University of Linz, Ginolis Ltd, IRCCS Centre “Bonino Pulejo”, under the coordination of CNR-Institute of Applied Sciences and Intelligent Systems. This communication will illustrate the progress of the activities. Acknowledgments: The authors acknowledge the EU funding within the Horizon 2020 Program, under the FET-OPEN Project “SensApp”, Grant Agreement n.829104.
    11786-59
    Author(s): Stefano Vassanelli, Univ. degli Studi di Padova (Italy)
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    Neural probes for electrical imaging and microstimulation of brain networks represent an ideal communication gateway between nanoelectronic devices emulating neuron computation and biological neurons. We show that titanium oxide microelectrodes and memristors can establish synaptic-like connections between biological and silicon spiking neurons across an elementary biohybrid network.
    Session LIVE: Special Focus: Keynote Session III
    Livestream: 23 June 2021 • 14:00 - 15:30 CEST | Zoom
    11783-1
    Author(s): Lynford L. Goddard, Univ. of Illinois (United States)
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    In this talk, I will discuss several new forms of optical microscopy that my group developed in recent years. Our goal was to recover tiny nanoscale features using a conventional microscope. This problem is challenging because of the low signal to noise ratio for such features. In the first method, we introduced the regularized pseudo-phase and used it to measure nanoscale defects, minute amounts of tilt in patterned samples, and severely noise-polluted nanostructure profiles in optical images. We also extended the method to study the dynamics of droplet condensation using environmental scanning electron microscopy. In the second method, we built upon electrodynamic principles (mechanical work and force) of the light-matter interaction and applied it to sense sub-10 nm wide perturbations. In the third method, we introduced the concepts of electromagnetic canyons and non-resonance amplification using nanowires and applied these concepts to directly view individual perturbations (25-nm radius = λ/31) in a nanoscale volume.
    11786-67
    Author(s): Donald T. Miller, Indiana Univ. (United States)
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    Vision starts when light is captured by photoreceptors, specialized cells in the retina that set fundamental limits on what we can see and are unfortunately lost in many blinding diseases. While photoreceptors carry considerable clinical and scientific importance in ophthalmology and vision science, means to assess their function and health at the level of individual cells remain limited. Recent advances in adaptive optics optical coherence tomography (AO-OCT) imaging systems have enabled photoreceptor cells to be observed and tracked with unprecedented 3D resolution and sensitivity in the living human eye. This imaging capability has allowed the dynamics of these cells to be studied in exquisite detail, in particular nanoscale transients the cells generate after being stimulated by light. These changes have been found to carry fundamental information about the photoreceptor’s physiology. Here, I will describe the capability of AO-OCT to image, track, and quantify these miniscule cell dynamics and how these measurements are being used to study vision and to assess cell dysfunction and health in disease.
    Session LIVE: Optical Metrology Plenary Session
    Livestream: 23 June 2021 • 16:30 - 17:30 CEST | Zoom
    11782-500
    Author(s): Peter J. de Groot, Zygo Corporation (United States)
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    Optical instruments have long played a role in manufacturing, and strong arguments favor accelerated adoption of fast, non-contact measurements of surfaces, shapes and positions as an enabler for industry 4.0. High-precision techniques such as optical interferometry have advanced considerably and have found applications ranging from semiconductor wafer lithography to automotive engine production. Even though there are clear benefits, there are obstacles to the more widespread adoption of optical techniques for dimensional measurements. Many of these obstacles are technical--such as vibration sensitivity and metrological traceability; but others reflect the cultural gaps between academia, makers of optical instruments, standards organizations and end users. In this talk, I propose that understanding these cultural differences can assist in advancing optical methods for the most critical needs of data-driven manufacturing.
    Session LIVE: FET-Open on Disruptive Ideas and Optical Technologies for Health II
    Livestream: 24 June 2021 • 10:00 - 12:25 CEST | Zoom
    11786-60
    Author(s): Giuseppe Chirico, Univ. degli Studi di Milano-Bicocca (Italy)
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    I will review the fundamental limiting issues in in-vivo optical imaging and discuss the proposal made by the IN2SIGHT consortium to overcome them and its impact. IN2SIGHT will foster a breakthrough in in-vivo optical imaging that will renovate the biocompatibility tests (ISO10993 EU norm) required for the development of biomaterials for clinical use. These tests are economical and ethical unsustainable for small-medium industries and for the society. The IN2SIGHT approach stands on a micro-structured chip that will recast our thinking of deep tissue in-vivo imaging. I discuss how this proposal will allow unique quantification of the immune reaction to biomaterials, thus reducing time and costs for testing with a potential huge impact on public health systems and our society. The project sees the collaboration of seven partners from five countries and will exploit from the beginning inter-sectorial approaches in an interdisciplinary environment.
    11786-61
    Author(s): Paula Marques, University of Aveiro (Portugal)
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    The goal of NeuroStimSpinal FETOPEN project is to contribute with a solution for spinal cord injury (SCI). Considering the biological complexity of SCI, a small incremental discovery in this area may represent an improvement that will translate into better clinical care and in the quality of life of these patients. Therefore, a neural tissue engineered scaffold capable of not only combining fibrous and porous topographic cues in order to mimic the morphology of the native spinal cord, but also potentiating the properties of graphenebased materials supported in a protein-rich decellularized matrix is being developed to be coupled with a wireless electrical stimulation device to promote the growth and reconnection of the ruptured nerves. This communication will cover the challenge and the progresses obtained so far.
    11786-62
    Author(s): Joost Brancart, Seppe Terryn, Guy Van Assche, Vrije Univ. Brussel (Belgium); François Tournhilhac, Ecole Supérieure de Physique et de Chimie Industrielles de la Ville de Paris (France); Frank Clemens, EMPA (Switzerland); Fumiya Iida, Univ. of Cambridge (United Kingdom); Anton W. Bosman, SupraPolix B.V. (Netherlands); Bram Vanderborght, Vrije Univ. Brussel (Belgium)
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    Soft robotic systems benefit from improved compliance and larger degrees of freedom, allowing more complex motions and safer interaction with their environment than rigid robotic structures. Due to the inherent softness of the materials that are often used to create such soft robotic structures, these systems are highly susceptible to various damage modes, such as cuts or punctures by sharp objects, overloading during actuation, flaws originating from manufacturing process or fatigue failure, drastically limiting their service lifetimes. Various types of synthetic materials that possess the ability to repair damage are being used to create soft robotic systems that are able to recover their performance by repairing incurred damage, either autonomously or after the application of a stimulus. The breakthrough targeted in the SHERO project is the development of complete robotic systems that are able to (1) sense and locate damage and to evaluate the system performance, (2) react intelligently to alleviate the damaging event and prevent catastrophic failure, (3) take the necessary measures to heal the damage to restore all functions by facilitating an autonomous or controlled healing action of the damaged element, and (4) perform a rehabilitation by evaluating the quality of the healing process and the recovery of functional performance, and finally, (5) return to action.
    11786-66
    Author(s): Mantas Grigalavicius, Kristian Berg, Theodossis A. Theodossiou, Oslo Univ. Hospital (Norway)
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    In the course of experiments for our FET open project Lumiblast, we set off to measure the excitation of various photoactive drugs (photosensitizers, PS) by the luminescence emission of luminol. Luminol (5-Amino-2,3-dihydrophthalazine-1,4-dione) is a chemical that interacts with reactive oxygen species (ROS) in basic conditions, and in the presence of metal catalysts like Fe or Cu, gives out a characteristic blue luminescence. When dissolved in organic solvents like DMSO, however, luminol only requires the addition of bases like KOH, NaOH or potassium terbutoxide, to fulfil the conditions for luminescence emission. In the present work we employed a detection system based on a spectrograph coupled to a ccd camera to register fluorescence (Fig 1B) or luminescence (Fig 1 A, C). In the case of characteristic fluorescence registration (Fig. 1B), the PSs investigated were excited by a 532 nm laser with a variable power output. We have documented the energy transfer from chemically induced luminol luminescence to a number of PSs including rose bengal, erythrosin B, hypericin amongst others. In all cases both the luminol emission and the luminol luminescence-induced PS fluorescence were registered as shown in the example of luminol and erythrosine b in Fig. 1C. We further attempted to register the generation of singlet oxygen from luminol-excited PSs. To achieve this, we employed the near-infrared (NIR) photomultiplier tube (PMT) shown in Fig.1 E, with a cut-off filter at 900nm and a bandpass filter at 1270±30 nm. This allowed only radiation within this spectral region to reach the PMT, corresponding to the characteristic phosphorescence of singlet oxygen, spin forbidden de-excitation to ground state triplet oxygen. A characteristic steady state singlet oxygen registration can be seen in Fig. 1D, for erythrosine b which has a high singlet oxygen quantum yield. The luminol luminescence was initiated by addition of terbutoxide to the DMSO luminol solution, at which point we can see a rise of the signal at 1270 nm. Upon addition of the singlet oxygen quencher, L-histidine, the signal dropped steeply to background levels. NOTE: Figures are not available.
    Session 1: Machine Learning and Data Visualisation

    Presentations scheduled in this session will be live-streamed on Monday 21 June, 9:30 to 10:50 hrs CEST


    To view the presentation timing and to connect to this live session, please follow the Live Link at:
    https://spie.org/optical-metrology/event/monday-am-live-stream-presentations-optics-for-arts-architecture-and-archaeology-o3a/2601558

    The link will be live 15 minutes prior to the announced start of the session.
    Note that times for the live broadcast are all Central European Summer Time, CEST (UTC+2:00 hours)
    11784-1
    Author(s): Costanza Cucci, Andrea Barucci, Lorenzo Stefani, Marcello Picollo, Consiglio Nazionale delle Ricerche (Italy); Reyes Jiménez-Garnica, Museu Picasso de Barcelona (Spain); Laura Fuster-Lopez, Univ. Politècnica de València (Spain)
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    Recently a new trend towards a more systematic use of Reflectance Hyperspectral imaging (HSI) has emerged in major museums. Extensive acquisition of HSI data opens up new research topics in terms of comparative analysis, creation and population of spectral databases, linking and crossing information. However, a full exploitation of these big-size data-sets unavoidably raises new issues about data-handling and processing methods. Along with statistical and multivariate analysis, new solutions can be borrowed from the Artificial Intelligence (AI) area, using Machine Learning (ML) and Deep Learning (DL) methods. In this work different algorithms based on multivariate analysis and Artificial Intelligence methods are comparitevely applied to process HSI data acquired on three Picasso’ paintings from the Museu Picasso collection in Barcellona. By using a “data-mining approach” the HSI-data are examined to unveil new correlations and extract embedded information.
    11784-2
    Author(s): Luke Butler, Sotiria Kogou, Alexander Hogg, Yu Li, Alessandra Vichi, Nottingham Trent Univ. (United Kingdom); Annabel Gallop, The British Library (United Kingdom); Haida Liang, Nottingham Trent Univ. (United Kingdom)
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    This study sets out to analyse the artistic materials used in the maritime Southeast Asian manuscript collection at the British Library. To gain a full understanding of how artistic practises may have developed over time and changed between regions, it is necessary to perform large scale scientific analysis. Visible/NIR spectral imaging is an efficient method of collecting spectral reflectance data which can be used to distinguish different materials. Recent advancements in automatic data collection have meant that the volume of data collected has greatly increased, making traditional approaches to data analysis impossible to perform in a timely manner. Machine learning provides a viable solution to this as it can be used to automatically cluster millions of spectra into smaller, more manageable numbers of distinct spectral groups. Self-organising Maps are used as the building blocks of an algorithm which can perform clustering of large collections of spectral imaging data. Spectral reflectance alone is often not enough to perform pigment identification, consequently other complementary techniques are required. Advances in spectral imaging mean that each of these complementary techniques has a corresponding imaging modality. The machine learning approach developed in this project can be adapted to allow for the clustering of multimodal spectral imaging data including VIS/NIR hyperspectral imaging, macro-X-Ray fluorescence mapping, macro-Raman mapping, and Fourier transform infrared mapping. For multimodal clustering, each modality can be clustered individually and then brought together to produce a single cluster map which is a more refined representation of the material distribution than that produced from any individual spectral imaging modality.   A visualisation tool has also been developed for the easy interpretation and interrogation of spectral imaging data cubes and cluster maps for entire collections. Both the visualisation tool and clustering method will be made accessible to the cultural heritage community through an online DIGILAB platform.  
    11784-4
    Author(s): Qunxi Zhang, Shaanxi History Museum (China); Shan Cui, Lu Liu, Jiaxin Wang, Jun Wang, Erlei Zhang, Jinye Peng, Northwest Univ. (China); Sotiria Kogou, Florence Liggins, Haida Liang, Nottingham Trent Univ. (United Kingdom)
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    Sketch extraction is of great value for historians to copy and study historical painting styles. However, most of the existing sketch extraction methods can successfully perform extraction only if the sketches are well preserved, but for paintings with severe conservation issues, the extraction methods need to be improved. Therefore, we propose a sketch extraction method using spectral imaging and deep learning. Firstly, the spectral image data is collected and the bands sensitive to the sketches are extracted by using the prior knowledge of the sketches (e.g. near infrared bands will be chosen if the sketches are made of carbon ink). A publicly available image dataset of natural scenes is used to pre-train the bi-directional cascade network (BDCN). The network parameters in the model are then fine-tuned by using the sketches drawn by experts based on images of painted cultural objects, so as to solve the problem of insufficient sketch dataset of painted cultural objects and enhance the generalization ability of the model. Finally, the U-Net is used to further suppress unwanted information, to make the sketch clearer. Experimental results show that the proposed method can extract clear sketches even with faded paintings and the presence of unwanted information or instrumental noise. It is superior to the other six advanced extraction methods in visual and objective comparison. The proposed deep learning method is also compared with an unsupervised clustering method using Self-Organising Map (SOM) which is a ‘shallow learning’ method where pixels of similar spectra are grouped into clusters without the need for data labeling by experts.
    11784-5
    Author(s): Noemi Zabari, Institute of Catalysis and Surface Chemistry, Polish Academy of Sciences (Poland)
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    Recent advances in technology have brought major breakthroughs in deep learning techniques. In this work, we elaborate on such techniques for output data of image processing performed on craquelure patterns in historical paintings. Historical painted objects, especially panel paintings, with their long environmental history, exhibit complex crack patterns called craquelures. These are cracks in paintings that can be referred to as ‘edge fractures’ as they are initiated from the free surface. The analysis has been conducted on the set of selected craquelure patterns on which recent deep learning methods i.e. Neural Networks algorithm is implemented and the results of such self-learning process are discussed.
    11784-6
    Author(s): Kai Yu, Yuheng Li, Northwest Univ. (China); Jing Yan, Shaanxi Provincial Institute of Archaeology (China); Ruiheng Xie, Univ. of Delaware (United States); Erlei Zhang, Liu Cheng, Jun Wang, Northwest Univ. (China)
    On demand
    Session 2: Imaging and Spectroscopy Instrument and Method Development

    Presentations scheduled in this session will be live-streamed on Monday 21 June, 16:15 to 17:05 hrs CEST


    To view the presentation timing and to connect to this live session, please follow the Live Link at:
    https://spie.org/optical-metrology/event/monday-pm-live-stream-presentations-optics-for-arts-architecture-and-archaeology-o3a/2601559

    The link will be live 15 minutes prior to the announced start of the session.
    Note that times for the live broadcast are all Central European Summer Time, CEST (UTC+2:00 hours)
    11784-8
    Author(s): Cristian Manzoni, CNR-Istituto di Fotonica e Nanotecnologie (Italy); Daniela Comelli, Giulio N. Cerullo, Benedetto Ardini, Politecnico di Milano (Italy); Renzo Vanna, CNR-Istituto di Fotonica e Nanotecnologie (Italy); Andrea Bassi, Gianluca Valentini, Alessia Candeo, Politecnico di Milano (Italy)
    On demand
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    The investigation of artworks of cultural heritage is generally aimed at the characterization of the constituent materials and the evaluation of their state of conservation. Research may shed light on the pigments and their potential deterioration mechanisms, and on the conservation treatments. Laboratory analysis on micro-samples taken from the artwork is still an invaluable practice for a deep understanding of the paint layer composition. In this context, a powerful technique is spectral microscopy, which acquires the spectrum for each point in the image of a sample. To acquire a continuous spectrum, one very efficient method is based on Fourier-transform (FT) spectroscopy as it allows massive parallelization on all the image pixels. Here we introduce a hyperspectral microscope based on an innovative FT spectrometer; the device is compact, robust, with high throughput and broad spectral coverage. In our microscope, light is collected by an infinity-corrected objective, propagates in the innovative spectrometer and is imaged on a silicon monochrome CMOS camera by a tube lens. The typical spectral resolution of the microscope, which can be flexibly adjusted for each measurement, is 3 THz (4 nm at 600 nm). We show very compact implementations of the hyperspectral microscope and their use for wide-field imaging of reflection, fluorescence and, interestingly, fluorescence-free Raman spectra. Thanks to the high throughput, the acquisition time of our microscope is significantly shorter than traditional raster-scanning approaches.
    11784-9
    Author(s): Margherita Longoni, Silvia Bruni, Univ. degli Studi di Milano (Italy)
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    Natural dyes pose problems concerning their non-invasive identification in artefacts when most of the techniques usually employed for “in-situ” analysis of coloring materials are used. Nowadays, surface-enhanced Raman spectroscopy (SERS) is currently employed to recognise dyes extracted from textiles, as well as applied to extractionless analysis directly on fibers. Nevertheless, there is still a demand for a method based on SERS suitable for the “in-situ” identification of the dyes on intact fabrics in museums. The enhancement of the Raman scattering in SERS is due to two different mechanism, an electromagnetic and a chemical one. The former contributes to the SERS intensification in an order of magnitude of 1010, while the latter of 102. Therefore, in principle, the SERS enhancement can be observed also in absence of a chemisorption and thus, a dry-state analysis leading to a completely non-invasive approach should be possible. In this context, we are studying the possibility of using thin films obtained by deposition of silver colloids on an optically transparent support, i.e. a glass slide, to prepare in an easy way SERS probes suitable for “in situ” analysis by means of portable Raman instrumentation. Silver nanospheres obtained by different methods [2,3] or, alternatively, silver nanostars [4] were deposited on glass slides functionalised with (3-aminopropyl)trimethoxysilane, to promote the adherence and prevent the so-called “coffee ring” effect. The films were tested for the identification of anthraquinonic dyes by a portable Raman micro-probe in mock-up samples of dyed textile fibres. The possibility of embedding the nanoparticles into a polymeric matrix will be also considered to ensure higher stability and a lower impact on the examined object. Finally, we exploited for the first time, at least to the best of our knowledge, commercial electrochemically-deposited substrates (SERSitive) to observe dry-state SERS, obtaining positive results that encourage in perspective to experiment the electrochemical path to produce suitable substrates for our purposes. [1] Z. Jurasekova, C. Domingo, J. V. Garcia-Ramos, S. Sánchez-Cortés, J. Raman Spectrosc, 39, (2008). [2] P. C. Lee, D. Meisel, J. Phys. Chem. A, 86, 17, 3391 (1982). [3] N. Leopold, L. Lendl, J. Phys. Chem. B, 107, 24 (2003). [4] A. Garcia-Leis, J. V. Garcia-Ramos, S. Sanchez-Cortes, J. Phys. Chem. C, 117, 15, 7791 (2013).
    11784-10
    Author(s): Daniela Comelli, Marta Ghirardello, Gianluca Valentini, Politecnico di Milano (Italy); Cristian Manzoni, CNR-Istituto di Fotonica e Nanotecnologie (Italy)
    On demand
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    We demonstrate the use of a wide-field, compact and ultra-stable hyperspectral camera, based on the Fourier-transform approach [1], to investigate the photoluminescence emission occurring from different radiative recombination paths in artist materials and paintings. The camera, based on the translating wedge-based identical pulse encoding system (TWINS), is characterized by high spectral resolution, high flexibility and compactness. Thanks to these latter feature we show how the device can be easily adapted for both microscopy measurements and remote time-gated imaging of paintings and we show its use for the identification and mapping of fluorescent species in artworks by also exploiting the potentiality provided by chemometrics methods. [1] Perri, A., et al. Optics express (2019), 27.11: 15956-15967.
    11784-11
    Author(s): Evgeniy L. Odlyanitskiy, Olga A. Smolyanskaya, ITMO Univ. (Russian Federation); Sergei Sirro, The State Russian Museum (Russian Federation); Jean-Paul Guillet, Univ. de Bordeaux (France); Vincent Detalle, Michel Menu, Ctr. de Recherche et de Restauration des Musées de France (France)
    On demand
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    Terahertz (THz) radiation in the frequency range 0.1 - 10 THz began to be used for the analysis of artwork in 2006. Terahertz images of paintings require computer processing in order to optimize the process of detecting defects and their visualization. In this work, an algorithm for solving this problem is proposed in relation to the terahertz analysis of paintings. A program is written in Python that searches, group and highlight defects in an image. To work with images, the methods of the OpenCV library is used, designed to solve computer vision problems. They are used to binarize images and search the defect contours on them, as well as to isolate defects when visualizing the results. The grouping of defects is carried out by the method of agglomerative hierarchical clustering. Scientific analysis of the materials used in art items allows to determine the period in which they were created, how they were preserved over the centuries and how they were restored. As part of the study, in this work, a 3D-model of the crystal structure of the red pigment was created. For this, the terahertz spectrum of the pigment was modeled by the density functional method. To experimentally study the optical characteristics of the pigment, measurements are carried out on a TeraView-4000 instrument in transmission mode. The pigment is measured in powder and tableted form. This work is supported by the Government of the Russian Federation (proposal #2020-220-08-5053 to support scientific research projects implemented under the supervision of leading scientists at Russian institutions and Russian institutions of higher education); and by RFBR and CNRS according to the research project №18-51-16002.
    11784-12
    Author(s): Alessia Artesani, Marina Ljubenovic, Istituto Italiano di Tecnologia (Italy); Stefano Bonetti, Istituto Italiano di Tecnologia (Italy), Univ. Ca' Foscari di Venezia (Italy); Arianna Traviglia, Istituto Italiano di Tecnologia (Italy)
    On demand
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    The work discusses the results of Terahertz Time-Domain Spectroscopy (THz-TDS) imaging carried out on cultural heritage assets. Hyperspectral THz images are corrupted by several degradation effects and their processing pose therefore major challenges. In this work, the limits of THz-TDS are addressed by a twofold computational strategy: (i) removal of the surface warping and (ii) application of a fast joint deblurring-denoising approach for image restoration. The reduction of the main degradation effects is illustrated with the aid of experiments conducted on ancient silver coin and a contemporary painting, highlighting the advantages for cultural heritage applications of imaging spectroscopy in the far-infrared frequencies (3-300 cm-1).
    Session 3: Deformation and Structural Analysis

    Presentations scheduled in this session will be live-streamed on Tuesday 22 June, 13:30 to 16:35 hrs CEST


    To view the presentation timing and to connect to this live session, please follow the Live Link at:
    https://spie.org/optical-metrology/event/tuesday-live-stream-presentations-optics-for-arts-architecture-and-archaeology-o3a/2601577

    The link will be live 15 minutes prior to the announced start of the session.
    Note that times for the live broadcast are all Central European Summer Time, CEST (UTC+2:00 hours)
    11784-13
    Author(s): Jessica Auber-Le Saux, Ctr. de Recherche et de Restauration des Musées de France (France), Univ. Paris-Saclay (France); Vincent Detalle, Ctr. de Recherche et de Restauration des Musées de France (France), Univ. PSL (France); Michalis Andrianakis, Foundation for Research and Technology-Hellas (Greece); Xueshi Bai, Ctr. de Recherche et de Restauration des Musées de France (France), Fondation des Sciences du Patrimoine (France); Nicolas Wilkie-Chancellier, Univ. Paris-Saclay (France); Vivi Tornari, Foundation for Research and Technology-Hellas (Greece)
    On demand
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    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.
    11784-14
    Author(s): Fabio M. Vincitorio, Gustavo Bolla, Ana Flores, Micaela Gomez-Coronel, Univ. Tecnológica Nacional (Argentina); Alberto Ramil, Ana J. López, Univ. da Coruña (Spain)
    On demand
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    In the last 100 years concrete and steel have been the most common building materials, so that they constitute the core of the structures on which the architecture of the 20th century is based [1]. Both materials present high resistance and durability [2] but the recent collapse of Minardi Bridge in Italy shows that it is absolutely necessary carry out real-time monitoring of the conservation status. In this sense, the building of the Agencia Impositiva Federal in the city of Paraná, built in the 70s, represents a clear example of brutalist architecture in Argentina. After 40 years of its construction and during remodeling tasks, serious problems in the concrete structures were discovered that forced the evacuation of the building. In order to develop an in situ monitoring system [3] that allows the premature detection of structural problems in 20th century building heritage, it was implemented a novel scheme based on digital holographic interferometry (DHI) which includes fiber optics to guide light from a semiconductor laser the optical set up made by 3D printing, that allows to register the dynamic behavior of the concrete based structure. This system was tested on concrete specimens of different composition which were submitted to loads in the range 1000 kg – 28 000 kg by using an Amsler hydraulic press. The obtained results, though preliminary, showed that it was possible to measure the radial deformation on normalized cylindrical specimens in the range of 4-10 micrometers. References: [1] Bell, T. R. (2017). A concept made concrete : conserving a Brutalist icon through architectural intervention. An explanatory document. A research project submitted in partial fulfilment of the requirements for the degree of Master of Architecture (Professional). Unitec Institute of Technology, New Zealand. https://hdl.handle.net/10652/4353 [2] Bolla, G.; López P.; Facendini S. Concrete with recycled aggregates for roads. 16 IRF World Meeting. 2010, Lisbon, Portugal. [3] Kumar R., Dwivedi G., Singh O.; Portable digital holographic camera featuring enhanced field of view and reduced exposure time, Optics and Lasers in Engineering, Volume 137,2021 https://doi.org/10.1016/j.optlaseng.2020
    11784-15
    Author(s): Sunita Saha, Warsaw Univ. of Technology (Poland); Amalia Siatou, Haute Ecole Arc (Switzerland), Univ. de Bourgogne (France); Robert Sitnik, Warsaw Univ. of Technology (Poland)
    On demand
    11784-16
    Author(s): Claudia Daffara, Sara Mazzocato, Univ. degli Studi di Verona (Italy); Tullio de Rubeis, Dario Ambrosini, Univ. degli Studi dell'Aquila (Italy)
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    A method for artworks monitoring is proposed, able to perform simultaneously speckle interferometry and speckle photography, towards the mapping of both out-of-plane and in-plane displacements. The system is simple and tailored to some specific needs of artwork diagnostics.
    11784-18
    Author(s): V. Gatto, Univ. of Amsterdam (Netherlands); Andrei Anisimov, Wouter Lettinga, Nan Tao, Technische Univ. Delft (Netherlands); Merel Van Schrojenstein Lantman, Univ. of Amsterdam (Netherlands); Bernice Crijns, RCE, Cultural Heritage Agency of the Netherlands (Netherlands); Roger M. Groves, Technische Univ. Delft (Netherlands)
    On demand
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    Structural delamination in mural paintings is a complex phenomenon and is considered among the most frequent types of damage. In conservation practice, the most common technique to identify structural detachments in wall paintings is the percussion method, otherwise known as the ‘tap and listen’ approach. Full-field optical techniques based on interferometry, such as shearography, can potentially provide a more scientifically substantiated evaluation of the condition of heterogeneous structures of wall paintings. The empirical nature of the percussion method was observed during the condition assessment of two medieval wall paintings in Maria Church, Nisse, Netherlands. Consequently, the need to obtain more knowledge regarding the structural condition of these wall paintings was established. Furthermore, to allow the formulation of specific treatment needs for structural delamination in wall paintings, accurate defect mapping is needed. The application of shearography coupled with thermography was believed to provide an holistic representation of the structural condition of the wall painting depicting St. Christopher in Maria Church. A comparison of the practical execution and the interpretation of data between shearography and the percussion method was conducted to deliver a description of both techniques. Initial comparison of the two methods confirmed what was already hypothesised: I) the percussion method can provide an approximate indication of delaminated areas. Results, which are considered both non-qualitative and non-quantitative, are dependent on the experience of the conservator; II) shearography can produce qualitative and quantitative results regarding the presence of delamination in complex structures of wall paintings. Analysis of the shearography data together with the percussion method may result in a reliable way to map the defects for future conservation activities. The next steps include optimisation of the thermal excitation for shearography to maximise the defect detection and adapt the shearography output for onsite interpretation by conservators and professionals in the cultural heritage.
    Session 4: Light-Matter Interaction

    Presentations scheduled in this session will be live-streamed on Tuesday 22 June, 13:30 to 16:35 hrs CEST


    To view the presentation timing and to connect to this live session, please follow the Live Link at:
    https://spie.org/optical-metrology/event/tuesday-live-stream-presentations-optics-for-arts-architecture-and-archaeology-o3a/2601577

    The link will be live 15 minutes prior to the announced start of the session.
    Note that times for the live broadcast are all Central European Summer Time, CEST (UTC+2:00 hours)
    11784-19
    Author(s): Marta Ghirardello, Politecnico di Milano (Italy); Vanessa Otero, LAQV Requimte (Portugal), VICARTE (Portugal); Gianluca Valentini, Lucia Toniolo, Politecnico di Milano (Italy); Austin Nevin, Courtauld Institute of Art (United Kingdom), CNR-Istituto di Fotonica e Nanotecnologie (Italy); Maria J. Melo, Univ. Nova de Lisboa (Portugal); Daniela Comelli, Politecnico di Milano (Italy)
    On demand
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    Cadmium yellows are a class of pigments based on cadmium sulfide (CdS) that can suffer degradation [1-4]. Although the degradation mechanism has been elucidated [5], the reasons behind the higher reactivity of some CdS are still unclear. It has been hypothesized that the higher reactivity can be related to an imperfect synthesis method [2-3]. This work shows that pigments synthesized following different routes [6-7] present different degrees of degradation in paints after artificial ageing. Moreover, the development of degradation products depends on the synthesis method and the photoluminescence emission from trap states [8] can be modified following degradation. Results obtained on in-laboratory prepared paints will be compared to historical degraded CdS paints from real paintings. [1] Van der Snickt, G. et al. Analytical Chemistry, 2012, 84.23: 10221-10228. [2] Mass, J. L. et al. Applied Physics A, 2013, 111.1: 59-68. [3] Levin, B.D.A. et al. arXiv:1909.01933, 2019. [4] Monico, L. et al. Science Advances, 2020, 6.2: eaay3514. [5] Monico, L. et al. Chemistry–A European Journal, 2018, 24.45: 11584-11593. [6] Otero, V. et al. Studies in Conservation, 2017, 62.3: 123-149. [7] Ghirardello, M. et al. Dyes and Pigments, 2020, 108998. [8] Comelli, D. et al., Analytical Chemistry, 2019, 91(5), 3421-3428.
    11784-21
    Author(s): Maria Amelia Suzuki, CNR-Istituto di Scienze del Patrimonio Culturale (Italy), Nottingham Trent Univ. (United Kingdom); Yu Li, Yuda Gu, Chi Shing Cheung, Nottingham Trent Univ. (United Kingdom); Cristiano Riminesi, CNR-Istituto di Scienze del Patrimonio Culturale (Italy); Haida Liang, Nottingham Trent Univ. (United Kingdom)
    On demand
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    Increased availability and use of ‘non-invasive’ analytical techniques in recent years, have called into question traditional assumptions of non-invasiveness of laser-based techniques and latest research developments have shown that it is essential to assess the extent of it for Raman spectroscopy, as particular compounds such as pigments may be highly altered/damaged upon laser radiation even at low laser intensity. In the present research, damage processes of oil paintings with historical pigments under CW lasers, with different excitation wavelength, laser intensity and fluence, are investigated with a monitoring set-up combining Raman spectroscopy, VIS-NIR reflectance spectroscopy and IR thermography.
    Session 5: 3D Tomography

    Presentations scheduled in this session will be live-streamed on Tuesday 22 June, 13:30 to 16:35 hrs CEST


    To view the presentation timing and to connect to this live session, please follow the Live Link at:
    https://spie.org/optical-metrology/event/tuesday-live-stream-presentations-optics-for-arts-architecture-and-archaeology-o3a/2601577

    The link will be live 15 minutes prior to the announced start of the session.
    Note that times for the live broadcast are all Central European Summer Time, CEST (UTC+2:00 hours)
    11784-22
    Author(s): Caterina Zaggia, Univ. degli Studi di Bologna (Italy); Magdalena Kowalska, Magdalena A. Iwanicka, Nicolaus Copernicus Univ. (Poland); Giorgia Sciutto, Silvia Prati, Univ. degli Studi di Bologna (Italy); Piotr Targowski, Nicolaus Copernicus Univ. (Poland)
    On demand
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    Removal of old deteriorated varnish layers from an easel painting is one of the most common but also most delicate restoration treatments. Apart from purely mechanical methods various solvents or mixtures of solvents have been used for this task over the last hundred years. Most often these chemicals were applied mechanically by swabbing, but also in a form of gels. However, the resulting formation of secondary and detrimental effects (such as swelling, leaching, solvent retention as well as high toxicity to the user) forced the development of new cleaning methodologies, aimed to overcome these drawbacks, guaranteeing a safe and effective removal of the damaged material. The aim of this paper is to discuss the applicability of optical coherence tomography for a multi-faceted and complementary assessment of different varnish removal processes, including the application of a novel nanogel system, the PHB-GVL. Since some effects, like swelling, may develop in a time span of hours, which is not a typical examination time for OCT, long-lasting stability of the measurement system had been ensured. For this task, a lab-developed high-resolution OCT instrument (3 µm axial resolution in the air) was adopted and the repeatability of surface recognition of 1.5 µm over 17 hours was achieved. This permitted for tracing of swelling effects in a multi-hour scale. The most desirable effect of such a restoration treatment is the removal of varnish without any alteration to the paint layer underneath. With the use of OCT, it was possible to trace this process by a direct comparison of the topography of the paint layer under varnish (before treatment) and after treatment. The results pointing at superior properties of the PHB-GVL nanogel applied with an electrospun polymeric tissue will be presented.
    11784-23
    Author(s): Patrick Atkinson, Chi Shing Cheung, Haida Liang, Nottingham Trent Univ. (United Kingdom)
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    The potential of Optical Coherence Tomography (OCT) as an online monitoring tool for the conservation treatment of artworks and historical objects is well recognised. OCT gives non-invasive micron scale measurements on the stratigraphy of transparent and turbid multi-layered structures such as the paint and varnish layers on Old Master Paintings, enabling the monitoring of the removal of degraded varnish coatings during the cleaning process. In previous work we highlighted the difficulties in distinguishing glaze layers on paintings (coloured, translucent layers containing pigments with refractive indices very close to the binding medium) from those of aged varnish due to similarities in their scattering properties which gave similar appearance in OCT images. We proposed a method to extract the spectra from the translucent layers to distinguish the glazed layer from the varnish layers, mitigating the possibility of accidental removal of glaze layers by over-cleaning. The method extracts the spectral features of a semi-transparent layer using a combination of spectral imaging (400-850 nm) and OCT images from a region with relatively uniform paint composition. The OCT image cube provides the thickness measure of the translucent layers and when coupled with the knowledge of the spectral information of the surface layer, the aged varnishes and glaze layers could be distinguished. This method, however, relied on the accurate alignment of the two separate imaging systems with vastly different spatial resolutions which makes spatial registration difficult, affecting the crucial correlation between the spectra and layer thickness. In this work, we propose a combined multimodal instrument that collects both the spectral image and OCT images from the same region of a painting through the same objective. A number of design options are considered based on the modification of an in-house developed high-resolution OCT system. Preliminary proof of concept results is demonstrated on painting mock-ups.
    11784-24
    Author(s): Michael Maria, Technische Univ. Delft (Netherlands); Lieve d'Hont, Univ. of Amsterdam (Netherlands); Andrei Anisimov, Technische Univ. Delft (Netherlands); Maartje Stols-Witlox, Univ. of Amsterdam (Netherlands); Roger M. Groves, Technische Univ. Delft (Netherlands)
    On demand
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    The visual appearance of a painting is the result of variations in pigments, layers and layer thicknesses. An important role can be played by ground colour. The ground is the first preparation of the support before the actual painting. Medieval painters worked on white grounds. Coloured grounds appeared during the late 15th century in Italy before spreading to the northern part of Europe around 1550. Painters like Rembrandt or Rubens exploited dark or light coloured grounds to create spectacular, realistic effects. But how can we understand how they do this? To answer this question and add some quantifiable analysis, one needs to resolve the spectral reflectivity profile of a painting in three spatial dimensions. In addition, as the main intent is to relate the optical effects with colours, one needs to operate using visible light. The answer to these challenges is visible-light Optical Coherence Tomography (vis-OCT). In this study, we investigate the use of vis-OCT to measure the reflectivity profile of multi-layered paint samples in three dimensions. Using mock-up paint samples we prepared with two thin paint layers on a black and a white paper support, we measured the reflectivity profiles of the separate colours and of the superposed colours over either the black or white (back)ground. This paper first describes the signal processing involved in rebuilding the spectral reflectivity in three dimensions. Secondly, we will present the results obtained from the mock-up samples and draw conclusions on the possibility to discriminate colours in a three-dimensional context. All reflectivity measurements will be compared to a classical, commercially available hyperspectral imaging setup. This study is executed in the context of the NWO Down to the Ground Project. The results of the OCT measurements will be used by technical art historians and conservators for investigations into coloured grounds.
    11784-25
    Author(s): Igor P. Gurov, Ekaterina V. Zhukova, ITMO Univ. (Russian Federation)
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    The paper presents the results of investigation of the art subjects materials micro structure that is the most important in studying the art subjects. The main diagnostic tests were performed using the OCT microscope (OCM) model EX1301 (Michelson Diagnostics, UK), which implements the swept-source Fourier-Domain OCT method. The device design uses the multi-beam OCT optics and a laser swept source model HSL-2000-11-MDL with central wavelength at 1305 nm. The laser wavelength sweep range is about 150 nm with radiation power 15 mW. The axial resolution (in tissue) is about 10 mkm and lateral resolution is 7.5 mkm. The OCM device has been successfully applied to investigate the techniques of khokhloma painting for the background and upper drawing, the vase executed in wood intarsia, jewelry encrusted by the mother of pearl. The experiments of investigation of porcelain, ceramic, natural and artificial origin stone were conducted. The OCM was used for studying thick multi-layer paint structure and varnish coatings and for evaluating properties of natural and imitation skin, canvas and tissues. Results of the study give a possibility to solve diagnostics problems. These include investigation of layered structures like dyes, varnishes, glues, materials with strong scattering and absorption in the analyzed spectral region, the local paint and varnish defects in the layers, areas of occurrence of pollution, to study cracks, splits of the material surface.
    11784-26
    Author(s): Victory Jaques, Marek Zemek, Jakub Šalplachta, Tomáš Zikmund, Daniel Ožvoldík, Jozef Kaiser, CEITEC - Central European Institute of Technology (Czech Republic)
    On demand
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    We present a practical demonstration of the overall capabilities of high resolution CT technique for the analysis of painted art samples, together with a developed comprehensive methodology. Those samples are made of a support material (panel, wall, yarn), preparatory layer(s) and pictural layer(s). They are multi-material and brittle, which makes them complicated to manipulate and analyze. We defined the visible and extractable features from acquired high resolution CT data (grains, material density, layering, growth lines, cells, yarn pattern). Its ease of access, achievable spatial resolution, non-destructiveness, 3D analysis, followed by overall effectiveness make the high resolution CT a perfect tool for the analysis of painted samples.
    11784-27
    Author(s): Aparajita Bandyopadhyay, Indian Institute of Technology Delhi (India); Karl Bertling, The Univ. of Queensland (Australia); Diksha Garg, Khushboo Singh, Indian Institute of Technology Delhi (India); Timothy Gillespie, Yah Leng Lim, The Univ. of Queensland (Australia); Lianhe Li, Paul Dean, Dragan Indjin, Edmund Linfield, A Giles Davies, University of Leeds (United Kingdom); Aleksandar D. Rakic, The Univ. of Queensland (Australia); Amartya Sengupta, Indian Institute of Technology Delhi (India)
    On demand
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    This present joint research, undertaken in two different hemispheres, is an effort to address the challenge of early structural and sub-surface assessment of heritage marble architectures, like the Taj Mahal, using two complementary non-contact, non-invasive imaging techniques in the THz range. This unique combination of broadband Terahertz Time Domain Imaging (THz-TDI) and highly sensitive, fast, THz-Laser Feedback Interferometry (THz-LFI) holds immense possibility in large-scale architectural restoration projects as they collectively provide accurate structural depth profile up to several centimeters in the volume of the marble including the strain generated within the structure leading to potential cracks.
    Session 6: Ground-based and Airborne Remote Imaging and Spectroscopy

    Presentations scheduled in this session will be live-streamed on Wednesday 22 June, 9:00 to 12:40 hrs CEST


    To view the presentation timing and to connect to this live session, please follow the Live Link at:
    https://spie.org/optical-metrology/event/wednesday-live-stream-presentations-optics-for-arts-architecture-and-archaeology-o3a/2601593

    The link will be live 15 minutes prior to the announced start of the session.
    Note that times for the live broadcast are all Central European Summer Time, CEST (UTC+2:00 hours)
    11784-28
    Author(s): Yu Li, Maria Amelia Suzuki, Chi Shing Cheung, Sotiria Kogou, Haida Liang, Nottingham Trent Univ. (United Kingdom)
    On demand
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    Studies of wall paintings require in situ ground based remote sensing evaluation. With its ablative nature, LIBS enables remote depth-resolved analysis. Combined with other remote technique s such as Raman and LIF, remote depth-resolved multi-modal analysis is made possible. Here we present a mobile standoff LIBS-Raman system with co-axial design. Other remote methods such as spectral imaging and LIF could also be incorporated, providing complementary information. Applications of standoff depth-resolved multi-modal material identification of wall paintings are demonstrated both in the lab and in situ for the first time, which helps better understand the painting schemes, and therefore inform decision-making for future conservation campaigns.
    11784-30
    Author(s): Sotiria Kogou, Yu Li, Chi Shing Cheung, Haida Liang, Nottingham Trent Univ. (United Kingdom); David Thickett, English Heritage (United Kingdom); Florence Liggins, Luke Butler, Nottingham Trent Univ. (United Kingdom)
    On demand
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    Historical buildings are prone to deterioration due to various reasons including environmental conditions, humidity and structural failures. The main factors of their degradation are moisture and salt activity. Salt weathering affects the appearance of the monuments but also causes chemical and mechanical degradation. The effect of salts in building deterioration is well-known, with several laboratory-based studies focusing on understanding the formation mechanisms. Here, we introduce a new methodology for the non-invasive monitoring and identification of moisture and salts following a complementary remote sensing approach. The study is based on ground-based remote short-wave infrared (SWIR) imaging and remote Raman spectroscopy from standoff distances of 3 to 15m [1]. The remote SWIR spectral imaging system covers the spectral range between 1 and 2.5 μm, with a spectral resolution of 5.5 nm and spatial resolution of 150 μm at a distance of 3m. The in-house developed mobile standoff Raman system operates with a continuous-wave (CW) excitation laser source at 780 nm. The laser beam can be focused at different distances resulting in a spot size of ~1 mm on the target. In our approach, SWIR imaging is used for scanning large wall surfaces. The post-processing of the acquired spectral imaging data using our novel machine learning-based clustering methods highlights the material variations across the wall. The detailed examination of the mean SWIR spectra for each cluster, allows a primary identification of moisture and salts, indicating also variations in volume concentration. The salts identification is then confirmed by remote Raman spectroscopy. The new method is presented through the examination of the historical building in Fort Brockhurst, an English Heritage monument in Portsmouth, UK.
    11784-31
    Author(s): Marina Ljubenovic, Arianna Traviglia, Istituto Italiano di Tecnologia (Italy)
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    This work introduces a novel fast hyperspectral image deblurring and denoising approach tailored to archaeological applications of remote sensing. Hyperspectral data recorded by means of airborne or satelliteborne sensors can be used to detect buried archaeological deposits as the latter have a localised impact on the physical and chemical properties of the soil and the vegetation located above them, contributing to make them structurally different from the surrounding elements. By processing and analysing hyperspectral images, archaeological photo-interpreters can detect subtle changes in the properties of ground elements that can be attributed to the presence of subterranean archaeological sites. Hyperspectral imagery, while rich in content as far as the spectral characteristics of ground elements, often lacks in spatial resolution and contains blurring degradation and noise, prominent especially in some spectral regions. The influence of blur and noise highly effects not only the quality of the visual appearance of the represented objects and compromises the interpretation process, but impacts also further processing of imagery, limiting consequently the detection of targets of interest. The methodology here presented is based on the low-rank properties of hyperspectral images and fully exploits a sparse hyperspectral data representation linked with the self-similarity characteristics of image patches (small image parts). The restoration procedure additionally includes a bend-dependent formulation of blurring degradation. The preliminary results show high performances and reduced computational complexity, and that the proposed approach is able to cope with Gaussian and Poisson noise and band-dependent blur. By removing severe noise and blur, the accurate detection and interpretation of buried structures in different shapes and sizes is thus improved. The proposed approach significantly increases the number of hyperspectral bands that can be used for further image processing and analysis, providing new avenues for features of interest discoveries in bands where they normally obscured by noise.
    Session 7: Applications to Art, Archaeology, Architecture and Anthropology

    Presentations scheduled in this session will be live-streamed on Wednesday 22 June, 9:00 to 12:40 hrs CEST


    To view the presentation timing and to connect to this live session, please follow the Live Link at:
    https://spie.org/optical-metrology/event/wednesday-live-stream-presentations-optics-for-arts-architecture-and-archaeology-o3a/2601593

    The link will be live 15 minutes prior to the announced start of the session.
    Note that times for the live broadcast are all Central European Summer Time, CEST (UTC+2:00 hours)
    11784-33
    Author(s): Xueshi Bai, Ctr. de Recherche et de Restauration des Musées de France (France), Fondation des Sciences du Patrimoine (France); Manon Gosselin, Univ. Paris-Saclay (France), Univ. Paris Nanterre (France); Philippe Dillmann, Florian Téreygeol, Univ. Paris-Saclay (France); Hortense Allégre, Ctr. de Recherche et de Restauration des Musées de France (France); Jessica Auber--Le Saux, Ctr. de Recherche et de Restauration des Musées de France (France), Fondation des Sciences du Patrimoine (France); Vincent Detalle, Ctr. de Recherche et de Restauration des Musées de France (France)
    On demand
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    Carbon content is one of the most influential factors of the mechanical behavior of iron and steel and a time marker of the fabrication period. The quantitative assessment of carbon content distribution in archaeological artefacts gives us insights on their properties and nature. We performed micro-LIBS analysis on archaeological steel in order to reconstruct its carbon content distribution map. The quantitative mapping of the carbon distribution enabled us to infer the different phases of the metallographic structure without time-consuming Nital attack treatment. In addition, LIBS carbon content mapping revealed phases that are invisible with metallographic method.
    11784-34
    Author(s): Giorgio Trumpy, Univ. Zürich (Switzerland); Jon Y. Hardeberg, Sony George, Norwegian Univ. of Science and Technology (Norway); Barbara Flueckiger, Univ. of Zurich (Switzerland)
    On demand
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    The digital reproduction of a historical movie should resemble as much as possible the analog film projection at the time of the movie release. Nowadays, practices in digital image capture of films do not properly consider the fundamental elements and conditions of the original film projection. The typical rigid RGB capture cannot adapt to the multitude of color film types to be digitized, and the diffuse illumination on the film generally used by standard digital scanning devices is unable to guarantee the proper visual rendition of the original analog projection of film prints. In order to overcome these problems, we designed and built a novel multispectral imaging system that illuminates the film with a condensed light beam. The light comes from the exit port of a custom-made integrating sphere, whose interior is illuminated by a set of ten LEDs that are switched on in succession for multiple image capture. The light coming out from the sphere is shaped by two distinct condensers chosen to minimize the light loss and to maximize the illuminated area. To obtain accurate transmittance data, a special flat-fielding operation had to be developed to compensate for the unstable temperature-dependent luminous intensities emitted by the LEDs. The new imaging system and the computational pipeline were tested on an assorted set of photographic slides. The level of accuracy of the transmittances obtained with the new multispectral imager guarantees color differences that fall below the color discrimination threshold of the human eye. In view of these results, the new optical design represents a promising solution for the creation of a new generation of motion picture film scanners.
    11784-36
    Author(s): Claudia Daffara, Univ. degli Studi di Verona (Italy); Simone Parisotto, Univ. of Cambridge (United Kingdom); Sara Mazzocato, Univ. degli Studi di Verona (Italy); Paola Ilaria Mariotti, Opificio delle Pietre Dure (Italy); Dario Ambrosini, Univ. degli Studi dell'Aquila (Italy)
    On demand
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    Infrared methods are of great importance in nondestructive testing of artworks, allowing a remote and wide-field imaging of interesting hidden features. Here we discuss a workflow based on thermal imaging in the mid infrared 3-5 micron range for the evaluation of subsurface defects in frescoes. Particular attention is payed to obtaining a high resolution (submillimetric) localization of the defects. The transfer of diagnostics techniques into real world applications, is discussed through the proof of concept of the proposed workflow on frescoes at the Sforza Castle (Milan, Italy).
    Session 8: Multimodal Imaging and Spectroscopy

    Presentations scheduled in this session will be live-streamed on Wednesday 22 June, 9:00 to 12:40 hrs CEST


    To view the presentation timing and to connect to this live session, please follow the Live Link at:
    https://spie.org/optical-metrology/event/wednesday-live-stream-presentations-optics-for-arts-architecture-and-archaeology-o3a/2601593

    The link will be live 15 minutes prior to the announced start of the session.
    Note that times for the live broadcast are all Central European Summer Time, CEST (UTC+2:00 hours)
    11784-37
    Author(s): Gaël Latour, Lab. d'Optique et Biosciences, Ecole Polytechnique (France), Univ. Paris-Saclay (France); Margaux Schmeltz, Lab. d'Optique et Biosciences, Ecole Polytechnique (France); Laurianne Robinet, Ctr. de Recherche sur la Conservation des Collections, Muséum National d'Histoire Naturelle (France); Sylvie Heu-Thao, Ctr. de Recherche sur la Conservation des Collections, Muséum national d'Histoire naturelle (France); Jean-Marc Sintès, Lab. d'Optique et Biosciences, Ecole Polytechnique (France); Claire Teulon, Lab. d'Optique et Biosciences, Ecole Polytechnique (France); Guillaume Ducourthial, Pierre Mahou, Marie-Claire Schanne-Klein, Lab. d'Optique et Biosciences, Ecole Polytechnique (France)
    On demand
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    Advanced nonlinear optical (NLO) microscopy enables quantitative in situ mapping of parchment degradation at the micrometer scale. We show that measurements of the ratio of fluorescence over second harmonic generation (SHG) signals probes severe collagen degradation and could help to identify the parchments most at risk, close to the irreversible collagen denaturation into gelatin. Conversely, the anisotropy parameter obtained from polarization-resolved SHG measurements probes the earlier stages of degradation. This approach is first validated by comparing NLO quantitative parameters to thermal measurements by differential scanning calorimetry on artificially altered contemporary parchments. We then analyze invaluable parchments from the Middle Ages.
    11784-38
    Author(s): Marta Castillejo, Mohamed Oujja, Instituto de Química Física Rocasolano, Consejo Superior de Investigaciones Científicas (Spain); Fernando Agua, Consejo Superior de Investigaciones Científicas (Spain); Mikel Sanz, Univ. Nacional de Educación a Distancia (Spain); Daniel Morales-Martin, Manuel García-Heras, María Ángeles Villegas, Consejo Superior de Investigaciones Científicas (Spain)
    On demand
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    Study of Historical Glass Grisailles by Non-linear Optical Microscopy M. Oujja(a), F. Agua(b), M. Sanz(a,c), D. Morales-Martin(b), M. García-Heras(b), M.A. Villegas(b), M. Castillejo(a) (a) Instituto de Química Física Rocasolano (CSIC), C/ Serrano 119, 28006 Madrid, Spain (b) Instituto de Historia (CSIC), C/ Albasanz 26-28, 28037 Madrid, Spain (c) Departamento de Física Interdisciplinar, Facultad de Ciencias, Universidad Nacional de Educación a Distancia (UNED), Senda del Rey 9, 28040 Madrid, Spain. In this work, the characterization via the Nonlinear Optical Microscopy (NLOM) modality of Multi-Photon Excitation Fluorescence (MPEF) of grisaille paint layers on historical stained glasses from different chronology and provenance in Spain is presented. Complementary glass analysis of the pieces was carried out by applying Laser Induced Breakdown Spectroscopy (LIBS) and Laser Induced Fluorescence (LIF) techniques. The grisaille paint layers studied display sufficient degree of transparency at the wavelength of 800 nm of the excitation femtosecond laser and in the spectral range of the emitted multiphoton fluorescence, making possible the non-invasive determination of the thicknesses of the grisaille paint layers by MPEF in the reflection configuration. The thickness values obtained by MPEF, in the range of 25 to 80 microns, were compared with those retrieved through Field Emission Scanning Electron Microscopy-Energy Dispersive X-ray Spectrometry (FESEM-EDS) measurements, showing good consistency and agreement. These results serve to validate the MPEF modality of NLOM for the non-destructive study of grisaille layers on historical glass substrates. Acknowledgments: This research has been funded by the Spanish State Research Agency (AEI) through projects PID2019-104124RB-I00/AEI/10.13039/501100011033 and PID2019-104220RB-I00 / AEI /10.13039/501100011033, by project TOP Heritage-CM (S2018/NMT-4372) from Community of Madrid, by EU H2020 project IPERION HS (GA 871034) and supported by CSIC Interdisciplinary Platform “Open Heritage: Research and Society” (PTI-PAIS). The authors acknowledge professional support from the TechnoHeritage Network of Science and Technology for the Conservation of Cultural Heritage.
    11784-39
    Author(s): Margaret Read, Nottingham Trent Univ. (United Kingdom), The British Museum (United Kingdom); Andrew Meek, The British Museum (United Kingdom); Florence Liggins, Chi Shing Cheung, Sotiria Kogou, Luke Butler, Nottingham Trent Univ. (United Kingdom); Capucine Korenberg, Denise Ling, The British Museum (United Kingdom); Haida Liang, Nottingham Trent Univ. (United Kingdom)
    On demand
    11784-40
    Author(s): Francesca Gabrieli, Rijksmuseum (Netherlands)
    On demand
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    Reflectance imaging spectroscopy (RIS) from visible to short-wave infrared (400 to 2500 nm), also known as hyperspectral imaging, is becoming another more widely used technique for the non-invasive study of polychrome art objects such as paintings. RIS is one of the many non- invasive imaging techniques used during “Operation Night Watch”. “Operation Night Watch” is the largest research project ever started by the Rijksmuseum in Amsterdam, and has the goal to investigate the conservation history, current condition, painting technique and artists’ materials of the Rembrandt iconic masterpiece Night Watch (1642) a canvas painting 3.78 m by 4.53 m in size. Due to the large size of the painting and its historical importance, the research is realized inside of a glass chamber that had been built around the painting in the “Gallery of Honor” of the Rijksmuseum, in front of the visiting public. RIS on the Night Watch was performed using two different hyperspectral line scanning imaging spectrometers (VNIR 400 to 1000 nm, 2.5 nm and SWIR 900 to 2500 nm, 6 nm). The complete painting was being scanned at a spatial resolution of 0.2 mm. The cameras including their lighting systems are mounted a on novel 2-D scanning platform, which includes auto focus systems that kept the line-scanning hyperspectral cameras in focus during scanning. The RIS results combined with the other non-invasive imaging techniques provide an in-depth understanding of Rembrandt’s painting technique and the actual condition of the painting and will serve as a foundation for the conservation treatment proposal for the Night Watch.
    Session 9: 3D Surface Analysis

    Presentations scheduled in this session will be live-streamed on Wednesday 22 June, 9:00 to 12:40 hrs CEST


    To view the presentation timing and to connect to this live session, please follow the Live Link at:
    https://spie.org/optical-metrology/event/wednesday-live-stream-presentations-optics-for-arts-architecture-and-archaeology-o3a/2601593

    The link will be live 15 minutes prior to the announced start of the session.
    Note that times for the live broadcast are all Central European Summer Time, CEST (UTC+2:00 hours)
    11784-41
    Author(s): Siavash Maraghechi, Emanuela Bosco, Johan P. M. Hoefnagels, Akke S. J. Suiker, Technische Univ. Eindhoven (Netherlands)
    On demand
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    Degradation of paper and the consequent loss of its chemical and mechanical properties has been studied for many decades. For conservators an understanding of the loss of mechanical properties of paper during degradation is highly relevant from a practical point of view. Considering the fibrous microstructure of paper, the mechanical properties of single cellulose fibers and their change in time has been of interest in paper degradation studies. With current advances in experimental micromechanics, the characterization of cellulose fibers is achievable at small scales and with very high accuracy. Such detailed analyses on naturally aged paper in combination with accelerated aging experiments lead to valuable insight in the degradation of paper. The current study represents a novel methodology for the accurate mechanical characterization of micro-scale fibers, such as cellulose fibers. To this end, in-situ mechanical tests are performed using high resolution optical profilometry (white light interferometry) in combination with Digital Image Correlation (DIC) to attain detailed strain measurements. Given the curly geometry of cellulose fibers, there is considerable out-of-plane deformation during a micro-tensile test, making is necessary to use profilometric images. An in-house built setup is used for application of micro-scale speckle pattern needed for DIC. Reliable evaluation of the cross-sectional area of fibers is attained by acquiring profilometric images of both the front and back sides of each fiber, using a mirror in a novel self-calibrating setup. Detailed analyses of the results from different samples show the accuracy and reliability of the measurements and the methodology. By these means, an accurate evaluation of the stiffness and strength of cellulose fibers is attained. Performing such measurements on cellulose fibers from aged papers is expected to result in better understanding of the effect of cellulose degradation on the mechanical properties of paper.
    11784-42
    Author(s): Irina M. Ciortan, Norwegian Univ. of Science and Technology (Norway); Andrea Giachetti, University of Verona (Italy); Sony George, Jon Y. Hardeberg, Norwegian Univ. of Science and Technology (Norway)
    On demand
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    Fluorescence is a photoluminescence phenomenon where light is absorbed at lower wavelengths and re-emitted at longer wavelengths. For classic artworks, fluorescence gives useful information about varnish and retouches. At the same time, modern artworks may employ synthetic fluorescent pigments because of their special appearance properties, such as increased brightness and vividness provoked by self-luminescence. Hence, it is relevant to investigate the fluorescent signals of cultural heritage objects when studying their appearance. This work proposes a variant to Reflectance Transformation Imaging (RTI) technique, namely Fluorescence Transformation Imaging. Reflectance Transformation Imaging method outputs a single-camera multi-light image collection of a static scene, which can be used to model the reflectance of the scene as a polynomial of the illumination directions. Similarly, Fluorescence Transformation Imaging aims to model the fluorescent signal based on a series of images with fixed scene and viewpoint and varying incident light directions - what changes with respect to RTI is that the wavelength of incident light needs to be shorter than the sensing wavelength. In the literature, there are works that explore the isotropic property of fluorescence in low-dimension multi-light imagery methods (such as Photometric Stereo) to model the appearance of an object with a first-order polynomial. This is because in the fluorescent mode the object gets closer to a Lambertian surface than in the reflective mode where non-Lambertian effects such as highlights are more likely to appear. Nonetheless, this assumption stands for single-object scenes, with uniform albedo and convex geometries. When there are multiple fluorescent objects in the scene, with concavities and non-uniform fluorescent component, then the fluorescence can become secondary light to the object and create interreflections. This paper explores the Reflectance and Fluorescence Transformation Imaging methods and the resulting texture maps for appearance rendering of heterogeneous non-flat fluorescent objects.
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    This contribution presents some examples of the application of ultraviolet fluorescence (UVF) photography and photogrammetry on cultural heritage objects and paintings. The used approach is based on low-cost systems sustainable in terms of costs for restorers and conservators, but, at the same time, able to supply valid and relevant information for a better knowledge of the preservation state, of previous restoration interventions and of possible superimposed materials. This knowledge is fundamental for planning and addressing the restoration activities, such as cleaning and consolidation, in the most appropriate way as possible. Specific cases studies will be reported concerning large paintings and 3D objects. In the first case, it has been necessary to acquire several images by dividing the surface into various parts, as function of the dimensions of the investigated area, and then by using photogrammetric tools to recompose the images into a single one (orthophotomosaic of the painting). In the second case, the UVF images are acquired all around the 3D objects and then processed in order to obtain a photorealistic model under ultraviolet fluorescence. The image acquisitions were obtained by using a digital camera equipped with different lens and filters. Lighting of the surfaces was obtained by UV projectors. The acquired images have been then processed through photogrammetric tools in order to obtain the final 2D and 3D ultraviolet fluorescence outputs of the investigated artworks that can be explored and profitably used for gathering metrically precise information and material response to UV radiation.
    11784-44
    Author(s): Athanasia Papanikolaou, Piotr Garbat, Malgorzata Kujawinska, Warsaw Univ. of Technology (Poland)
    On demand
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    Digital image correlation (DIC) is a well-established technique for the measurement and monitoring of displacements and strains in engineering objects. In technical applications, the surface of an object is modified by applying artificial random structure and monochrome cameras are typically used. The challenge in the measurement of Cultural Heritage objects (CHO) lies in the necessity of using the natural surface texture, which in most cases is far from the ideal random pattern required for DIC. On the other hand, spectrally separated content of natural CHO textures captured by color cameras may provide additional spatial information and support DIC analysis. Therefore the main objective of this work is to gain knowledge on the best color image preprocessing path including the selection of the best demosaicing algorithms for the spectral and monochrome channels with respect to minimizing displacement reconstruction errors.
    Session PS: Poster Session
    Note that times for the live broadcast are all Central European Summer Time, CEST (UTC+2:00 hours)

    Posters will be available for viewing during the two live-streamed sessions on Friday 25 June, 10:00 to 11:30 hrs AND 15:30 to 17:00 hrs CEST


    Select the best time available for your time zone and join us and the poster authors for the live poster sessions on Friday 25 June!
    The poster session will be hosted on the Remo platform, allowing visitors to move freely between presentations, meet the authors, and ask questions about their research. Use this opportunity to meet your colleagues and coauthors online.

    Learn more about the Remo platform on the How to Participate page. [{https://spie.org/conferences-and-exhibitions/EOM/how-to-participate+{https://spie.org/conferences-and-exhibitions/EOM/how-to-participate}]
    11784-45
    Author(s): Dario Giuffrida, Istituto per i Processi Chimico Fisici, CNR (Italy), Univ. degli Studi di Messina (Italy); Viviana Mollica Nardo, Istituto per i Processi Chimico Fisici, CNR (Italy); Daniela Neri, Irene Calabrò, Loredana Pace, Giovanni Cucinotta, Comune di Reggio Calabria – Settore Cultura (Italy); Rosina Celeste Ponterio, Istituto per i Processi Chimico Fisici, CNR (Italy)
    On demand
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    The present work shows the application of a terrestrial laser scanner (TLS) for the documentation of an interesting religious building preserved in the medieval archaeological site of Motta Sant’Agata, located in the hinterland of the Municipality of Reggio C., Italy. The survey project, part of the POR project “Circuito delle aree archeologiche urbane di Reggio Calabria”, has a twofold objective: 1. to create a 3D model with high resolution and metric accuracy for needs related to conservation, restoration and monitoring of degradation processes of the structures; 2. to develop digital products and media for dissemination and remote visit (via virtual tour and augmented reality). Considering the size of the area (about 900 mq) and the architectural features of the ruins, made up by perimeter walls of 30 m x 10m preserved for over 2 m in elevation, 4 underground crypts and other annexed structures (e.g. bell tower), the use of the Faro Focus 3D S120 appeared the most suitable choice. It is a portable and versatile laser-scanner, based on phase-shift technology, which is mounted on a tripod and is equipped with a calibrated RGB camera with 70 megapixels. This device has allowed to capture the entire religious complex through 94 positions of scans distributed along the nave, inside the crypts and along the perimeter walls. The model resulting from the scan process have finally provided a 3D digital replica, from which qualitative and quantitative information useful can be extracted: geometric measures, plans at different altitude, transversal and longitudinal sections and wall elevations. A virtual tour was also generated using the 360° pictures captured during each scan. TLS have finally revealed useful for metric documentation, monitoring the conservation of the buildings, as basis for digital or physical restoration as well for their enhancement and dissemination.
    11784-47
    Author(s): Sureeporn Khampaeng, Pichayada Katemake, Chawan Koopipat, Chulalongkorn Univ. (Thailand)
    On demand
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    The technical photography (TP) method has been using in identifying pigments in paintings and the results could be used in the early stage before confirming with other methods such as X-Ray Fluorescence and Raman spectroscopy. The TP method employs visible, UV and IR as light sources with different filters. Moreover, the multi-spectrum method, using a continuous light source and various filters, has been used in the same application. This research proposed a method of using narrow multi-colored LEDs as light sources instead of colored filters. It aimed to optimize the number of LED channels for identifying pigments in conservation and restoration applications. Twelve tunable single-wavelength LEDs having wavelengths of 400-700 nm and 2 white LEDs, were used as light sources for capturing images of 357 Kremer pigments, applied on white card paper, without an optical brightening agent, through a visible pass filter, located in front of the single lens reflex Canon 5D Mark II camera that was modified by removing the UV and IR blocks. The 357 pigments including 9 main colors: 50 red pigments, 37 orange pigments, 82 yellows, 38 greens, 38 blues, 17 purples, and a group of greys browns, blacks and whites were used as samples. Subsequently, the pigments were classified, based on the captured images obtained from the individual LED. The redundancy of the CIEL*C*h data of each LED was reduced using the principal component analysis and the number of LEDs was optimized. It was found that all pigments could be classified and some pigments could be identified using single wavelength LEDs. The PCA should be applied to the CIEL*C*h data of pigments having similar shade. The 598 nm 425 nm LEDs were optimized for identifying and classifying blue pigments. The 430 nm, 640 nm and 540 nm were for purple, 403 nm, 540 nm, 660 nm and 672 nm for red, 403 nm, 447 nm, 540 nm and 672 nm for orange, 503 nm, 540 nm and 598 nm for yellow, 503 nm, 598 nm and 640 nm for green and 403 nm, 503 nm, 540 nm and 660 nm for a group of white, grey, black and brown.
    11784-49
    Author(s): Antonio Perri, NIREOS SRL (Italy); Cristian Manzoni, CNR-Istituto di Fotonica e Nanotecnologie (Italy); Daniela Comelli, Politecnico di Milano (Italy); Giulio N. Cerullo, Politecnico di Milano (Italy), CNR-Istituto di Fotonica e Nanotecnologie (Italy); Dario Polli, Politecnico di Milano (Italy), NIREOS SRL (Italy), CNR-Istituto di Fotonica e Nanotecnologie (Italy); Fabrizio Preda, NIREOS SRL (Italy)
    On demand
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    Hyperspectral imaging (HSI) is a novel non-invasive analytical technique based on spectroscopy. It measures the light spectrum from each point of a scene of interest. It generates an accurate digital record for documentation and archiving in art conservation. This information can be used for diagnostics by monitoring changes, degradation or damages to paintings, for supporting in artwork restoration, for artist's material identification and pigment mapping, as well as for discovering the history of a piece of art by e.g. revealing underdrawings and retouchings. HSI measures the continuous spectrum of the light as a function of the wavelength λ for each pixel of the scene at coordinates (x, y) with fine spectral resolution, thus building the so-called 3-dimensional hyperspectral image. This data cube contains an extensive amount of information. Therefore, many numerical methods and algorithms have been developed to enable the extraction of quantitative parameters related to the physicochemical properties of the imaged objects from congested scenes. Here we present HERA, a novel and compact hyperspectral camera by NIREOS. The device, based on the Fourier-transform approach, combines high delay precision, long-term stability, insensitivity to vibrations and broad spectral coverage. It can measure absolute reflectance and fluorescence with very high spectral accuracy and resolution (≈3-nm, comparable to best commercial push-room systems) in the visible and near-infrared. HERA does not require any scanning of the object under analysis. This feature makes it extremely flexible and applicable to the study of works of art of different nature and size. Potential applications range from the on-site study of museum paintings, to the assessment of the conservation status of large monuments and historic buildings, to the documentation of small objects using standard macro photography lenses. In this paper, we will present a series of application examples in the field of conservation science to demonstrate its versatility.
    11784-50
    Author(s): Inmaculada Donate Carretero, Ana Rosa García Pérez, Carmen Vega Martín, Beatriz Mayans Zamora, María Martín Gil, Miriam Bueso Manzanas, Instituto del Patrimonio Cultural de España (Spain)
    On demand
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    During 15th and 16thcenturies, while painters in Flanders or Italy used chalk (calcium carbonate) in ground layers of panel paintings, master painters in Spain employed gypsum (calcium sulphate dihydrate). Thereby, the identification of these minerals in such artworks is relevant for historical studies, especially for periods when there was an active artistic exchange between those countries. Visible and near-infrared reflectance imaging spectroscopy is already applied to characterize pigments and binders in paintings. In addition, there are investigations suggesting that, due to the transparency of some pigments mixed with binder in the near-infrared range, the signal coming from the subjacent substrate may be identified in the reflectance spectra, together with the bands of absorption of pigments and binders. This work proposes a non-invasive methodology involving near-infrared reflectance imaging spectroscopy, for distinguishing between chalk- and gypsum-based ground layers. The presented methodology has been validated using reference samples of oil pigments applied on both preparation layers. Spectral images of samples of gypsum, chalk and pigments, powdered and mixed with binder have been compared with the spectra of the reference samples, revealing the distortions on the reflectance curves of pigments due to the ground layers. The spectral images have been acquired with the VARIM 2.0 system, endowed with an InGaAS detector camera, coupled to an image spectrograph, covering the range from 1000 nm to 1700 nm. Moreover, several real cases have been examined. Study areas takes into account zones affected by retouching, rectifications and conservative interventions, previously identified by non-invasive imaging techniques. The results prove the capability to discriminate gypsum and chalk on ground layers of panel paintings using a non-invasive methodology that involves near-infrared reflectance imaging spectroscopy and without sampling. Consequently, this technique can be a new and important tool to study the origin of panel paintings from the 15th and 16th centuries.
    11784-51
    Author(s): Agnese Babini, Sony George, Jon Y. Hardeberg, Norwegian Univ. of Science and Technology (Norway)
    On demand
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    Hyperspectral imaging has become a powerful technique for the non-invasive investigation of works of art, thanks to the possibility to obtain spectral information over the spatial region, allowing the identification and mapping of constituent materials. While hyperspectral imaging has been extensively used on paintings and manuscripts, little work has been done on stained glass. In this paper, a workflow for the imaging and analysis of stained-glass windows is proposed. Contrarily to previous works on the topic, which deal with in-situ applications, the acquisition workflow described in this paper relates to a laboratory set-up. In this configuration, the imaging was carried out in transmittance, under controlled illumination, using a HySpex 1800 camera, which works in the VNIR region. The sample was placed on a translator stage equipped with a diffusing panel, with the light source positioned below the diffuser. To test the validity of the set-up, a mock-up stained-glass panel, originally employed for a project at the Fairford Church (England), was used. A detailed description of the acquisition set-up and the pre-processing steps will be provided in the paper. The processing was carried out with two aims: object visualization and chromophore identification. Regarding visualization, both RGB and false-color images were created by extracting suitable bands from the data-cubes, while the appearance of the glass under different illuminants was rendered using color matching functions. Regarding chromophore identification, the RGB and false-color images were compared, to understand whether similar colors had different compositions. The spectra of each tile were then extracted and compared, and pXRF measurements were carried out to obtain complementary information on the glass composition.
    11784-52
    Author(s): Giovanna Marussi, Univ. degli Studi di Trieste (Italy); Ilaria Carlomagno, Giuliana Aquilanti, Matteo Amati, Patrick Zeller, Elettra-Sincrotrone Trieste S.C.p.A. (Italy); Matteo Crosera, Univ. degli Studi di Trieste (Italy); Enrico Prenesti, Univ. degli Studi di Torino (Italy); Bruno Callegher, Gianpiero Adami, Univ. degli Studi di Trieste (Italy)
    On demand
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    X-Rays are a non-destructive, element specific probe of great potential for cultural heritage. Furthermore, synchrotron radiation sources provide high intensity leading to extraordinary sensitivity. These capabilities were exploited for studying four ancient gold coins dating back to the IV and V century A.D.. Combining the complementary information obtained by X-Ray Fluorescence and Photoemission Spectroscopy, we determined the chemical composition of the coins and we assess the speciation of the chemical contaminants providing information about historical situation of the minting period of the specimens and the metallurgic knowledge available at the time.
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    Optical Coherence Tomography (OCT) has proven to be an extremely valuable tool for the non-invasive stratigraphic analysis of paintings. One of the important components of OCT is the broadband laser source. The recent availability of off-the-shelf white light supercontinuum laser sources has meant that OCT systems can be built at any wavelength in the visible and short-wave infrared (SWIR) regime (~400-2500 nm). The most common OCT systems are those built for biomedical applications and they tend to be centered around near infrared spectral regions with low water absorption coefficient, such as 800nm and 1300nm. Historic artist materials such as paints tend to be highly scattering which limits the OCT depth of penetration at these wavelengths. A systematic study was conducted on paint layers composed of common artist pigments in egg tempera and oil to explore the optimum spectral window for maximum depth of penetration for OCTs and found it to be around 2.2 µm over the VIS/SWIR range. An OCT system was then developed at 1960nm and demonstrated to provide superior depth of penetration compared with lower wavelength OCT systems for highly scattering paint and other materials. Recently, the development of broadband laser sources has been extended to the mid-IR region. Consequently, there has been a growing interest in developing OCT with ever longer wavelength, beyond the SWIR, in the hope to increase the depth of penetration even further. To explore this in the mid-IR spectral region, we collected the FTIR spectra of a large selection of paint materials prepared as paint outs in external reflection and transmission mode in the region 4000 - 400 cm-1 (2.5 - 25 µm). With this work, we aim to systematically explore whether by extending the wavelength of OCTs to the mid-IR region would allow deeper penetration into objects of interest for cultural heritage science. To explore this in the mid-IR spectral region, we collected the FTIR spectra of a selection of paint materials prepared as paint outs in external reflection, transreflection and transmission mode in the region 4000-400 cm-1 (2.5-25 µm). External reflection (ER)-FTIR spectroscopy is a suitable tool for the non-invasive chemical characterization of materials and presents significant advantages (no need of sampling and detection of combination/overtone bands) compared to the other collection modes [4]. However, its use is still limited as FTIR spectra collected in ER mode, particularly in specular geometry, are much more challenging to interpret compared to FTIR spectra collected in Attenuated Total Reflection (ATR) and transmission mode. This is due to strong distortions affecting fundamental IR bands of ER-FTIR spectra, which are a direct consequence of the reflection phenomenon for absorbing materials in mid-IR. Multiple factors affect the resulting ER-FTIR spectra, including the material refractive index, absorption coefficient, roughness of the surface and particle size. Hence, the same pigments in egg tempera and oil applied on different substrates as paint outs were measured. Finally, the FTIR spectra collected will be used to compile a spectral database of paint materials, which will contribute to the advancement of ER-FTIR spectroscopy for non-invasive chemical analysis of materials.
    Conference Chair
    Nottingham Trent Univ. (United Kingdom)
    Conference Chair
    Technische Univ. Delft (Netherlands)
    Program Committee
    Univ. degli Studi dell'Aquila (Italy)
    Program Committee
    Consejo Superior de Investigaciones Científicas (Spain)
    Program Committee
    Daniela Comelli
    Politecnico di Milano (Italy)
    Program Committee
    Univ. degli Studi di Verona (Italy)
    Program Committee
    Vincent Detalle
    Centre de Recherche et de Restauration des Musées de France (C2RMF) (France)
    Program Committee
    National Gallery of Art (United States)
    Program Committee
    Duke Univ. (United States)
    Program Committee
    Raffaella E. M. Fontana
    Istituto Nazionale di Ottica (Italy)
    Program Committee
    ITMO Univ. (Russian Federation)
    Program Committee
    State Hermitage Museum (Russian Federation)
    Program Committee
    Univ. Paris-Sud (France)
    Program Committee
    Consiglio Nazionale delle Ricerche (Italy)
    Program Committee
    S. I. Vavilov State Optical Institute (Russian Federation)
    Program Committee
    Istituto Nazionale di Ottica-CNR (Italy)
    Program Committee
    International Institute for Conservation (United Kingdom)
    Program Committee
    Warsaw Univ. of Technology (Poland)
    Program Committee
    Nicolaus Copernicus Univ. (Poland)
    Program Committee
    Mathieu Thoury
    Synchrotron SOLEIL (France)
    Program Committee
    Foundation for Research and Technology-Hellas (Greece)