The non-invasive diagnostic and analytical approach to the study of works of art is an important topic within the priority research area of "Technologies applied to Cultural Heritage". Several techniques have been developed worldwide in the past to achieve a characterization of paintings as complete as possible and to extract data on the origin and age of materials used. Among the optical techniques a very important role is played by: - Infrared Reflectography (IRR), which enables the visualization of details underneath the visible surface of a painting, exploiting the partial transparency of the painted layer when subjected to IR radiation. - Hyper- and Multi-spectral imaging, a non-invasive technique for polychrome surface and painting investigation, which provides a spectral and colorimetric characterisation of the entire painted surface. With this project the Italian team (ENEA-Frascati & CNR-IFAC,Firenze) and the Japanese team (NICT-Tokyo & NNRICP-Nara) propose to extend the imaging techniques mentioned above to Gigahertz (GHz) and Terahertz (THz) frequencies, more specifically in the range from 20 GHz to 0.6 THz, which is situated between the microwave and infrared regions of the electromagnetic spectrum. Radiation in this spectral range is reflected by metals and aqueous materials, while it is transmitted with low attenuation through paper and most dielectric materials. Imaging applications are rapidly developing in material science. In particular, regarding the characterization of materials used in works of art, Mid IR spectroscopy and X-ray analysis are currently used to identify organic and inorganic materials respectively. GHz/THz imaging systems will provide useful data on the internal physical structure of non-metallic objects without touching the artworks investigated. This non-invasive cross-section image of the object is acquired by extracting the reflected pulse from a particular interface of two media with different refractive indexes. The main objective of the project is to extend the existing visible and infrared (VIS/IR) technologies in order to obtain a multifrequency analysis tool for cultural heritage artworks and objects (paintings, wall-paintings, mosaics, etc.). The integration of IRR data and VIS/IR hyper-spectral imaging with GHz/THz imaging will provide a powerful tool for researchers in the field of art conservation. This objective will be achieved by designing and constructing a novel hyper-spectral scanning system equipped with various probe heads and sources of electromagnetic radiation at different frequencies. The possibility to cover a wide spectral range will make it possible to correlate information from different spectral regions while performing fast measurements in a single data collection campaign. The long wavelength operation, together with the capability of the system to measure the phase of the reflected radiation will give additional information about the optical properties, not only of the sample surface, but also of the underlying materials, providing information about the internal structure of the samples, once the topological contribution to the measured phase shift is taken into account. Such a technique will be useful, for example, to identify paintings covered by gesso or plaster layers or to determine detachments in frescoes, which are not detectable with standard techniques. The high reflectivity and absorption of water in this spectral range can also be exploited to determine moisture damages to structures and the presence of biological infestations in the samples depth, like algae, lichens, green patinas or other microorganism under mosaic tiles. The ENEA-Frascati team has a long standing expertise in the development of THz sources, detectors and instrumentation. In collaboration with NICT-Tokyo, ENEA-Frascati already performed preliminary investigations in the THz region in the field of art conservation utilizing a THz Free Electron Laser operating in the spectral range from 90 to 150 GHz as a source. These laboratory measurements were carried out utilizing a reflecting imaging setup able to perform 3D scans of small samples, with 200 micrometers spatial resolution. ENEA also operates a second Free Electron Laser source in the frequency interval from 0.4 to 0.7 THz. The setup of an imaging system utilizing this source is under development. CNR-IFAC has extensive experience in the field of spectroscopy, for use in examining works of art, and in researching and developing multi- and hyper-spectral imaging instruments for non-invasive diagnostic purposes. CNR-IFAC has a consolidated expertise in microwave techniques and is well equipped with instrumentation up to 50 GHz. The established collaboration with NICT focuses on the development of new analytical technologies, for characterizing materials used in works of art, both as a diagnostic tools for analysing and understanding works of art, as an aid in conservation and restoration work, and, lastly, as a means of monitoring and evaluating the state of conservation of artistic objects. NICT-Tokyo has been a pioneer in the application of THz imaging to heritage science, and has contributed to pre-conservation examinations of masterpieces, which include Polittico di Badia by Giotto and Trittico di San Giovenale by Masaccio. The observation was compared with broadband spectroscopy by IFAC-CNR. NICT also works with leading museums, such as the Metropolitan Museum of Art. NICT has been collaborating with Tokyo National Museum-Tokyo and Nara National Institute for Cultural Properties NNRICP-Nara, which is responsible for conservation of archaeological and historical objects in Japan including wall paintings. The THz-ARTE project will address "on site" measurements, which require portable low power equipment, specifically designed to perform large area scans of paintings and frescoes. The project activity is articulated in the following phases and tasks: - The first task of the project aims at modifying an existing scanning tool, designed at CNR-IFAC for VIR/IR hyper-spectral and IR reflectographic measurements, in order to adapt it for driving a GHz source/probe head operating in the range between 20 and 40 GHz. This task will be carried out by ENEA and CNR-IFAC during the first year of the project. Based on the already acquired experience of CNR-IFAC, ENEA, NICT and NNRICP, "on site" measurements of works of art and of specific artwork mock-ups will be jointly performed. - The second task, to be carried out in the second year of the project, deals with the development of an new scanning system at ENEA, able to perform imaging on a 1x1 square meter area, on the basis of the results obtained in the first task. - The third task regards the implementation of a solid-state source operating at about 120 GHz on the two scanning systems previously developed. "On site" measurements of works of art will also be performed at this frequency. - A further step, which depends on funding availability in subsequent years of the project, will be the design and construction of a radiation launching system and detecting probe assembly based on the same conceptual scheme as the low-frequency system, but extending its operation up to 0.6 THz. A multidisciplinary international workshop on non-invasive diagnostic for art conservation gathering both scientists and art conservators will be jointly organized in the frame of the THz-ARTE project. A portable hyper-spectral imaging device, operating from the visible to the GHz spectral region, designed for "on site" operation on works of art, will be developed and tested. The device will be capable of providing images of large sampling areas (typically 1x1 square meter with a lateral resolution of about 0.5 mm in the GHz region). The phase-sensitive method employed in the detection of radiation in the spectral interval from 20 GHz to 0.6 THz will provide depth information on the artworks, including the capability of visualizing the internal structure of paintings and the possibility of monitoring damages or biological infestations under the surface. The availability of different probing heads will allow reflective imaging in frequency ranges that show complementary characteristics of the artworks under investigation: - the interval 20 - 40 GHz is suitable to investigate "thick" structures, like plaster or frescoes with coarse lateral resolution; - the interval 90 - 150 GHz can provide information on different painting layers with medium resolution; - the interval 200 - 600 GHz can complement IR techniques in identifying the nature of pigments and preparation layers. We expect to find correlations between results obtained in the VIS/IR region and in the GHz/THz region. Thanks to the special care devoted to the integration of different probing heads and to the system portability, the hyper-spectral imaging device has a great potential for industrial prototyping and commercialization. This project will boost the already established collaboration between ENEA / CNR-IFAC and NICT enhancing the scientific and technologic relations between Italy and Japan. A previous project was approved as a significant bilateral project in the frame of the collaboration agreement between Italy and Japan for the years 2008 - 2009.In spite of the lack of funding from MAE, relevant activities were conducted by ENEA-Frascati and NICT-Tokyo utilizing internal resources. As a part of the collaboration between ENEA and NICT comparative measurements on paintings and pigments were performed at the THz Compact Free Electron Laser Facility of the ENEA-Frascati Research Center. Both ENEA and NICT have additional collaborations with CNR. More specifically, there is a Scientific Collaboration Agreement between NICT and IFAC-CNR signed in 2010 that refers to research activities directed at the analysis, experimentation and refinement of (invasive and non-invasive) analytical tools and methodologies, the development of prototype instruments for diagnosing, restoring and conserving works of art, and the synthesis and evaluation of materials for conservation. CNR-IFAC, ENEA, NICT and NNRICP have plans to participate in joint research activities in the Horizon 2020 Programme of the European Union.
Terahertz Advanced Research TEchniques for non-invasive analysis in art conservation (THz-ARTE)
2013
Abstract
The non-invasive diagnostic and analytical approach to the study of works of art is an important topic within the priority research area of "Technologies applied to Cultural Heritage". Several techniques have been developed worldwide in the past to achieve a characterization of paintings as complete as possible and to extract data on the origin and age of materials used. Among the optical techniques a very important role is played by: - Infrared Reflectography (IRR), which enables the visualization of details underneath the visible surface of a painting, exploiting the partial transparency of the painted layer when subjected to IR radiation. - Hyper- and Multi-spectral imaging, a non-invasive technique for polychrome surface and painting investigation, which provides a spectral and colorimetric characterisation of the entire painted surface. With this project the Italian team (ENEA-Frascati & CNR-IFAC,Firenze) and the Japanese team (NICT-Tokyo & NNRICP-Nara) propose to extend the imaging techniques mentioned above to Gigahertz (GHz) and Terahertz (THz) frequencies, more specifically in the range from 20 GHz to 0.6 THz, which is situated between the microwave and infrared regions of the electromagnetic spectrum. Radiation in this spectral range is reflected by metals and aqueous materials, while it is transmitted with low attenuation through paper and most dielectric materials. Imaging applications are rapidly developing in material science. In particular, regarding the characterization of materials used in works of art, Mid IR spectroscopy and X-ray analysis are currently used to identify organic and inorganic materials respectively. GHz/THz imaging systems will provide useful data on the internal physical structure of non-metallic objects without touching the artworks investigated. This non-invasive cross-section image of the object is acquired by extracting the reflected pulse from a particular interface of two media with different refractive indexes. The main objective of the project is to extend the existing visible and infrared (VIS/IR) technologies in order to obtain a multifrequency analysis tool for cultural heritage artworks and objects (paintings, wall-paintings, mosaics, etc.). The integration of IRR data and VIS/IR hyper-spectral imaging with GHz/THz imaging will provide a powerful tool for researchers in the field of art conservation. This objective will be achieved by designing and constructing a novel hyper-spectral scanning system equipped with various probe heads and sources of electromagnetic radiation at different frequencies. The possibility to cover a wide spectral range will make it possible to correlate information from different spectral regions while performing fast measurements in a single data collection campaign. The long wavelength operation, together with the capability of the system to measure the phase of the reflected radiation will give additional information about the optical properties, not only of the sample surface, but also of the underlying materials, providing information about the internal structure of the samples, once the topological contribution to the measured phase shift is taken into account. Such a technique will be useful, for example, to identify paintings covered by gesso or plaster layers or to determine detachments in frescoes, which are not detectable with standard techniques. The high reflectivity and absorption of water in this spectral range can also be exploited to determine moisture damages to structures and the presence of biological infestations in the samples depth, like algae, lichens, green patinas or other microorganism under mosaic tiles. The ENEA-Frascati team has a long standing expertise in the development of THz sources, detectors and instrumentation. In collaboration with NICT-Tokyo, ENEA-Frascati already performed preliminary investigations in the THz region in the field of art conservation utilizing a THz Free Electron Laser operating in the spectral range from 90 to 150 GHz as a source. These laboratory measurements were carried out utilizing a reflecting imaging setup able to perform 3D scans of small samples, with 200 micrometers spatial resolution. ENEA also operates a second Free Electron Laser source in the frequency interval from 0.4 to 0.7 THz. The setup of an imaging system utilizing this source is under development. CNR-IFAC has extensive experience in the field of spectroscopy, for use in examining works of art, and in researching and developing multi- and hyper-spectral imaging instruments for non-invasive diagnostic purposes. CNR-IFAC has a consolidated expertise in microwave techniques and is well equipped with instrumentation up to 50 GHz. The established collaboration with NICT focuses on the development of new analytical technologies, for characterizing materials used in works of art, both as a diagnostic tools for analysing and understanding works of art, as an aid in conservation and restoration work, and, lastly, as a means of monitoring and evaluating the state of conservation of artistic objects. NICT-Tokyo has been a pioneer in the application of THz imaging to heritage science, and has contributed to pre-conservation examinations of masterpieces, which include Polittico di Badia by Giotto and Trittico di San Giovenale by Masaccio. The observation was compared with broadband spectroscopy by IFAC-CNR. NICT also works with leading museums, such as the Metropolitan Museum of Art. NICT has been collaborating with Tokyo National Museum-Tokyo and Nara National Institute for Cultural Properties NNRICP-Nara, which is responsible for conservation of archaeological and historical objects in Japan including wall paintings. The THz-ARTE project will address "on site" measurements, which require portable low power equipment, specifically designed to perform large area scans of paintings and frescoes. The project activity is articulated in the following phases and tasks: - The first task of the project aims at modifying an existing scanning tool, designed at CNR-IFAC for VIR/IR hyper-spectral and IR reflectographic measurements, in order to adapt it for driving a GHz source/probe head operating in the range between 20 and 40 GHz. This task will be carried out by ENEA and CNR-IFAC during the first year of the project. Based on the already acquired experience of CNR-IFAC, ENEA, NICT and NNRICP, "on site" measurements of works of art and of specific artwork mock-ups will be jointly performed. - The second task, to be carried out in the second year of the project, deals with the development of an new scanning system at ENEA, able to perform imaging on a 1x1 square meter area, on the basis of the results obtained in the first task. - The third task regards the implementation of a solid-state source operating at about 120 GHz on the two scanning systems previously developed. "On site" measurements of works of art will also be performed at this frequency. - A further step, which depends on funding availability in subsequent years of the project, will be the design and construction of a radiation launching system and detecting probe assembly based on the same conceptual scheme as the low-frequency system, but extending its operation up to 0.6 THz. A multidisciplinary international workshop on non-invasive diagnostic for art conservation gathering both scientists and art conservators will be jointly organized in the frame of the THz-ARTE project. A portable hyper-spectral imaging device, operating from the visible to the GHz spectral region, designed for "on site" operation on works of art, will be developed and tested. The device will be capable of providing images of large sampling areas (typically 1x1 square meter with a lateral resolution of about 0.5 mm in the GHz region). The phase-sensitive method employed in the detection of radiation in the spectral interval from 20 GHz to 0.6 THz will provide depth information on the artworks, including the capability of visualizing the internal structure of paintings and the possibility of monitoring damages or biological infestations under the surface. The availability of different probing heads will allow reflective imaging in frequency ranges that show complementary characteristics of the artworks under investigation: - the interval 20 - 40 GHz is suitable to investigate "thick" structures, like plaster or frescoes with coarse lateral resolution; - the interval 90 - 150 GHz can provide information on different painting layers with medium resolution; - the interval 200 - 600 GHz can complement IR techniques in identifying the nature of pigments and preparation layers. We expect to find correlations between results obtained in the VIS/IR region and in the GHz/THz region. Thanks to the special care devoted to the integration of different probing heads and to the system portability, the hyper-spectral imaging device has a great potential for industrial prototyping and commercialization. This project will boost the already established collaboration between ENEA / CNR-IFAC and NICT enhancing the scientific and technologic relations between Italy and Japan. A previous project was approved as a significant bilateral project in the frame of the collaboration agreement between Italy and Japan for the years 2008 - 2009.In spite of the lack of funding from MAE, relevant activities were conducted by ENEA-Frascati and NICT-Tokyo utilizing internal resources. As a part of the collaboration between ENEA and NICT comparative measurements on paintings and pigments were performed at the THz Compact Free Electron Laser Facility of the ENEA-Frascati Research Center. Both ENEA and NICT have additional collaborations with CNR. More specifically, there is a Scientific Collaboration Agreement between NICT and IFAC-CNR signed in 2010 that refers to research activities directed at the analysis, experimentation and refinement of (invasive and non-invasive) analytical tools and methodologies, the development of prototype instruments for diagnosing, restoring and conserving works of art, and the synthesis and evaluation of materials for conservation. CNR-IFAC, ENEA, NICT and NNRICP have plans to participate in joint research activities in the Horizon 2020 Programme of the European Union.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
