A framework for surface metrology on Cultural Heritage objects based on scanning conoscopic holography

L'applicazione della metrologia di superficie e dell'analisi dimensionale allo studio dei beni culturali può rivelare importanti informazioni sull'oggetto e favorire l'integrazione di molteplici tecniche diagnostiche. Tuttavia, l'applicazione di queste discipline ai Beni Culturali richiede particolari requisiti e attenzioni. In questa tesi, presento i risultati dell'implementazione di diversi sistemi di misurazione della superficie basati sul principio della conoscopia olografica. I senori conoscopici sono strumenti capaci di misurare distanze con precisione micrometrica a scale diverse, accoppiati a slitte micrometriche possono essere utilizzati per acquisire scansioni areali dell'oggetto in esame. Per facilitare la loro applicazione alle opere d'arte ho sviluppato un extit{framework} per applicare la metrologia di superficie ai beni culturali. Il framework copre diversi aspetti del processo di analisi ed utilizzo dei dati e comprende la creazione di raccolte di campioni, le strategie per la scansione dell'oggetto, l'archiviazione e l'analisi dei dati ed eventualmente l'incertezza legata alla misura. Il extit{framework} mira a rendere più accessibile l'implementazione della metrologia di superficie e dei sistemi di scansione dell'analisi dimensionale per l'analisi dei beni culturali. I risultati raccolti su una varietà di materiali artistici (metalli, dipinti su tavola, tela, carta, pergamena e dipinti murali) mostrano come questi sistemi possano essere utilizzati per monitorare gli effetti delle procedure di pulitura, la stabilità dimensionale delle opere d'arte ed il loro invecchiamento.The application of surface metrology and dimensional analysis to the study of artworks can reveal important information on the object and aid the integration of multiple techniques. However, the application of these disciplines to Cultural Heritage objects necessitates particular care and requirements. In this dissertation, I present the results of the implementation of different systems, based on Conoscopic Holography range finders, for measuring the surface. Conoscopic holography range finders are viable instruments for measuring distances with micrometer accuracy at different scales, coupled with micrometric stages they can be used for acquiring areal scans of the object under investigation. To ease their application to artworks I built a framework for applying surface metrology to Cultural Heritage objects. The framework covers different aspects of the research workflow comprising the creation of samples collections, the strategies for scanning the object, the storing and the analysis of the data and eventually the uncertainty linked to the measurement. This framework aims to make more accessible the implementation of surface metrology and dimensional analysis scanning systems tailored to the analysis of Cultural Heritage objects. The results collected on a variety of artworks materials (metals, panels painting, canvas, paper, parchment and mural paintings) show how these systems can be used for monitoring the effects of cleaning procedures, the dimensional stability of the artworks and their ageing

PCA-based method for managing and analyzing single-spot analysis referenced to spectral imaging for artworks diagnostics

Artworks diagnostics is based on the joint use of several nondestructive techniques to acquire complementary information on the materials. A common practice in the field is to perform the analyses with single-spot analytical techniques, e.g. spectroscopy-based, after a preliminary screening of the artwork with full-field imaging-based techniques. We present a method and its practical implementation for fusing and analyzing data collected using analytical systems that acquire single spot measurements mapped to spectral imaging stacks. The fused dataset of single-spot and imaging observations is analyzed using principal component analysis (PCA). The effectiveness of the method for artworks diagnostics is shown on spectroscopy and imaging datasets of an ancient canvas painting. The results of the PCA analysis on the final fused dataset are compared against the PCA analysis performed on the original datasets from single-spot and imaging measurements taken separately. We propose two practical implementations of the procedure, one based on using graphical user interface (GUI) and open-source GIS software (QGIS), the other one based on an open-source Python module, named SPOLVERRO, specifically developed for this project and released on a public repository. The method allows conservation scientists to analize effectively the heterogeneous datasets acquired in a diagnostic campaign. single-spot spectroscopy data are referenced on imaging data.the sampling area of each spectroscopy spot is used for extracting and averaging the respective imaging data values.the final matrix is analyzed using PCA for extracting further information

A Novel Framework for Highlight Reflectance Transformation Imaging

We propose a novel pipeline and related software tools for processing the multi-light image collections (MLICs) acquired in different application contexts to obtain shape and appearance information of captured surfaces, as well as to derive compact relightable representations of them. Our pipeline extends the popular Highlight Reflectance Transformation Imaging (H-RTI) framework, which is widely used in the Cultural Heritage domain. We support, in particular, perspective camera modeling, per-pixel interpolated light direction estimation, as well as light normalization correcting vignetting and uneven non-directional illumination. Furthermore, we propose two novel easy-to-use software tools to simplify all processing steps. The tools, in addition to support easy processing and encoding of pixel data, implement a variety of visualizations, as well as multiple reflectance-model-fitting options. Experimental tests on synthetic and real-world MLICs demonstrate the usefulness of the novel algorithmic framework and the potential benefits of the proposed tools for end-user applications.Terms: "European Union (EU)" & "Horizon 2020" / Action: H2020-EU.3.6.3. - Reflective societies - cultural heritage and European identity / Acronym: Scan4Reco / Grant number: 665091DSURF project (PRIN 2015) funded by the Italian Ministry of University and ResearchSardinian Regional Authorities under projects VIGEC and Vis&VideoLa

Multiscale roughness analysis by microprofilometry based on conoscopic holography: a new tool for treatment monitoring in highly reflective metal artworks

The analysis of surface roughness in highly reflective metal artworks is challenging and requires contactless devices capable to measure regions with high micrometer accuracy in both depth and lateral directions. We demonstrate optical profilometry based on scanning conoscopic holography for micrometer measurement of silver samples treated with different hand-made cleaning processes. The technique is shown effective in acquiring shiny and smooth metal samples providing high-resolution and highaccurate dataset (0.1µm depth and 5µm lateral resolution) that is a reliable representation of the microsurface structure. From a statistical point of view, the cleaning treatments have the same nature of the low-abrasion, but the underlying mechanical processes are different. This fact suggested a more in-depth study of both the amplitude and the hybrid areal roughness parameters. It is proposed a workflow for a dual integrated multiscale roughness analysis for surface characterization: a scale inspection to detect possible texture non-homogeneity, and a signals separation to outline the most significant texture components. The scale-limited components allowed to discriminate the different surface processes. The results on silver samples demonstrate the potential of multiscale roughness analysis by conoscopic holography as a new tool for treatment monitoring in metal artworks

Feasibility and performance analysis in 3D printing of artworks using laser scanning microprofilometry

We investigated optical scanning microprofilometry and conoscopic holography sensors as nondestructive testing and evaluation tools in archeology for obtaining an accurate 3D printed reproduction of the data. The modular microprofilometer prototype allows a versatile acquisition of different materials and shapes producing a high-quality dataset that enables surface modelling at micrometric scales from which a "scientific" replica can be obtained through 3D printing technologies. As exemplar case study, an archeological amphora was acquired and 3D printed. In order to test the feasibility and the performance of the whole process chain from the acquisition to the reproduction, we propose a statistical multiscale analysis of the surface signal of object and replica based on metrological parameters. This approach allows to demonstrate that the accuracy of the 3D printing process preserves the range of spatial wavelengths that characterizes the surface features of interest within the technology capabilities. This work extends the usefulness of the replicas from museum exposition to scientific applications

A Practical Reflectance Transformation Imaging Pipeline for Surface Characterization in Cultural Heritage

We present a practical acquisition and processing pipeline to characterize the surface structure of cultural heritage objects. Using a free-form Reflectance Transformation Imaging (RTI) approach, we acquire multiple digital photographs of the studied object shot from a stationary camera. In each photograph, a light is freely positioned around the object in order to cover a wide variety of illumination directions. Multiple reflective spheres and white Lambertian surfaces are added to the scene to automatically recover light positions and to compensate for non-uniform illumination. An estimation of geometry and reflectance parameters (e.g., albedo, normals, polynomial texture maps coefficients) is then performed to locally characterize surface properties. The resulting object description is stable and representative enough of surface features to reliably provide a characterization of measured surfaces. We validate our approach by comparing RTI-acquired data with data acquired with a high-resolution microprofilometer.Terms: "European Union (EU)" & "Horizon 2020" / Action: H2020-EU.3.6.3. - Reflective societies - cultural heritage and European identity / Acronym: Scan4Reco / Grant number: 66509

A novel framework for highlight reflectance transformation imaging

We propose a novel pipeline and related software tools for processing the multi-light image collections (MLICs) acquired in different application contexts to obtain shape and appearance information of captured surfaces, as well as to derive compact relightable representations of them. Our pipeline extends the popular Highlight Reflectance Transformation Imaging (H-RTI) framework, which is widely used in the Cultural Heritage domain. We support, in particular, perspective camera modeling, per-pixel interpolated light direction estimation, as well as light normalization correcting vignetting and uneven non-directional illumination. Furthermore, we propose two novel easy-to-use software tools to simplify all processing steps. The tools, in addition to support easy processing and encoding of pixel data, implement a variety of visualizations, as well as multiple reflectance-model-fitting options. Experimental tests on synthetic and real-world MLICs demonstrate the usefulness of the novel algorithmic framework and the potential benefits of the proposed tools for end-user applications

Measuring thermal spread during bipolar cauterizing using an experimental pneumoperitoneum and thermal sensors

ObjectiveDuring nerve-sparing robot-assisted radical prostatectomy (RARP) bipolar electrocoagulation is often used but its use is controversial for the possible thermal damage of neurovascular bundles. Aim of the study was to evaluate the spatial-temporal thermal distribution in the tissue and the correlation with the electrosurgery-induced tissue damage in a controlled, CO2-rich environment modelling the laparoscopy conditions..MethodsWe manufactured a sealed plexiglass chamber (SPC) equipped with sensors to reproduce experimentally the environmental conditions of pneumoperitoneum during RARP. We evaluated in 64 pig musculofascial tissues (PMTs) of approximately 3 cm3 × 3 cm3 × 2 cm3 the spatial-temporal thermal distribution in the tissue and the correlation with the electrosurgery-induced tissue damage in a controlled CO2-rich environment modeling the laparoscopy conditions. Critical heat spread of bipolar cauterizing during surgical procedure was assessed by the employment of a compact thermal camera (C2) with a small core sensor (60 × 80 microbolometer array in the range 7–14 μm).ResultsBipolar instruments used at 30 W showed a thermal spread area of 18 mm2 when applied for 2 s and 28 mm2 when applied for 4 s. At 60 W, bipolar instruments showed a mean thermal spread and 19 mm2 when applied for 2 s; and 21 mm2 when applied for 4 s. Finally, histopathological analysis showed that thermal damage is distributed predominantly on the surface rather than in depth.ConclusionsThe application of these results is very interesting for the definition of an accurate use of bipolar cautery during nerve-sparing RARP. It demonstrates the feasibility of using miniaturized thermal sensors, thus addressing the potential for next developments regarding the design of thermal endoscopic devices for robotic use

Worldwide tests of generic attractants, a promising tool for early detection of non-native cerambycid species

A large proportion of the insects which have invaded new regions and countries are emerging species, being found for the first time outside their native range. Being able to detect such species upon arrival at ports of entry before they establish in non-native countries is an urgent challenge. The deployment of traps baited with broad-spectrum semiochemical lures at ports-of-entry and other high-risk sites could be one such early detection tool. Rapid progress in the identification of semiochemicals for cerambycid beetles during the last 15 years has revealed that aggregation-sex pheromones and sex pheromones are often conserved at global levels for genera, tribes or subfamilies of the Cerambycidae. This possibly allows the development of generic attractants which attract multiple species simultaneously, especially when such pheromones are combined into blends. Here, we present the results of a worldwide field trial programme conducted during 2018-2021, using traps baited with a standardised 8-pheromone blend, usually com-plemented with plant volatiles. A total of 1308 traps were deployed at 302 sites covering simultaneously or sequentially 13 European countries, 10 Chinese provinces and some regions of the USA, Canada, Australia, Russia (Siberia) and the Caribbean (Martinique). We intended to test the following hypotheses: 1) if a species is regularly trapped in significant numbers by the blend on a continent, it increases the prob-ability that it can be detected when it arrives in other countries/continents and 2) if the blend exerts an effective, generic attraction to multiple species, it is likely that previously unknown and unexpected spe-cies can be captured due to the high degree of conservation of pheromone structures within related taxa. A total of 78,321 longhorned beetles were trapped, representing 376 species from eight subfamilies, with 84 species captured in numbers greater than 50 individuals. Captures comprised 60 tribes, with 10 tribes including more than nine species trapped on different continents. Some invasive species were captured in both the native and invaded continents. This demonstrates the potential of multipheromone lures as ef-fective tools for the detection of 'unexpected' cerambycid invaders, accidentally translocated outside their native ranges. Adding new pheromones with analogous well-conserved motifs is discussed, as well as the limitations of using such blends, especially for some cerambycid taxa which may be more attracted by the trap colour or other characteristics rather than to the chemical blend

Smartphone diagnostics for cultural heritage

In recent years, smartphones have developed tumultuously; in fact, they have increasingly taken on the role of portable and compact personal computers equipped with a range of sensors and applications capable of monitoring, for example, physical activity, heartbeat and sleep. Their ability to manage and transmit data makes them a very interesting tool even in the scientific field, where the concept of "lab in a phone" is gaining ground. In this work, after briefly summarizing these new approaches, we will consider the application of smartphones to the diagnostics of Cultural Heritage