Beam-Shape Effects and Noise Removal From THz Time-Domain Images in Reflection Geometry in the 0.25 - 6 THz Range (original) (raw)
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Terahertz time domain spectroscopy and imaging applied to cultural heritage
2013
The spectroscopy and imaging techniques using the terahertz (THz) range have progressed rapidly, and are expected to become useful examination tools in heritage science. Its nondestructive cross-section images are especially useful to understand the techniques of artworks, especially panel paintings.
Terahertz applications in cultural heritage: case studies
Terahertz (THz) spectroscopy and imaging is a non-destructive, non-contact, non-invasive technology emerging as a tool for the analysis of cultural heritage 1 . THz Time Domain Spectroscopy (TDS) techniques have the ability to retrieve information from different layers within a stratified sample, that enable the identification of hidden sub-layers in the case of paints and mural paintings 2 .
2019
In the field of Cultural Heritage science, the use of non-destructive and contact-free techniques has increased sharply over the past 10 years. Compared to conventional spectroscopic and imaging techniques such as X-ray, Ultraviolet (UV), Infrared (IR) and laser spectroscopy, terahertz time-domain imaging (THz-TDI) is an innovative, non-invasive and safe technique, which provides good penetration depth (~1 cm) and broad spectral bandwidth (0.1 10 THz). This paper sets out the protocol and methodology for the application of THz-TDI to immovable Cultural Heritage, illustrated by a series of case studies. The case studies demonstrate the efficacy of the technique in providing structural and material information for conservators.
Terahertz imaging systems: a non-invasive technique for the analysis of paintings
2009
Terahertz (THz) imaging is an emerging technique for non-invasive analysis. Since THz waves can penetrate opaque materials, various imaging systems that use THz waves have been developed to detect, for instance, concealed weapons, illegal drugs, and defects in polymer products. The absorption of THz waves by water is extremely strong, and hence, THz waves can be used to monitor the water content in various objects. THz imaging can be performed either by transmission or by reflection of THz waves. In particular, time domain reflection imaging uses THz pulses that propagate in specimens, and in this technique, pulses reflected from the surface and from the internal boundaries of the specimen are detected. In general, the internal structure is observed in crosssectional images obtained using micro-specimens taken from the work that is being analysed. On the other hand, in THz time-domain imaging, a map of the layer of interest can be easily obtained without collecting any samples. When realtime imaging is required, for example, in the investigation of the effect of a solvent or during the monitoring of water content, a THz camera can be used. The first application of THz time-domain imaging in the analysis of a historical tempera masterpiece was performed on the panel painting Polittico di Badia by Giotto, of the permanent collection of the Uffizi Gallery. The results of that analysis revealed that the work is composed of two layers of gypsum, with a canvas between these layers. In the paint layer, gold foils covered by paint were clearly observed, and the consumption or ageing of gold could be estimated by noting the amount of reflection. These results prove that THz imaging can yield useful information for conservation and restoration purposes.
Terahertz Waves and Cultural Heritage: State-of-the-Art and Perspectives
Sensing the Past, 2017
Noninvasive diagnostic technologies capable of gathering information on materials and the state of preservation of works of art are crucial to help conservators, archaeologists, and anthropologists plan and carry out their tasks properly. Among these technologies, those operating in the terahertz (THz) frequency range are among the newest and are deserving great attention as they allow both high-resolution imaging and material identification. A synthetic snapshot of the development today of THz spectroscopy and imaging is provided in this chapter together with practical examples assessing the advantages offered in the framework of cultural heritage surveys.
Nonlinear imaging and THz diagnostic tools in the service of Cultural Heritage
Applied Physics A, 2012
We present the use of novel nonlinear imaging, terahertz time-domain spectroscopy and imaging as powerful diagnostic tools for studies of works of art. It is shown that nonlinear imaging offers precise in-depth information, while terahertz imaging can reveal hidden objects and uncover information on highly absorbing organic compounds whose visualization is difficult in other parts of the spectrum.
Time-domain imaging system in the terahertz range for immovable cultural heritage materials
Strain
In the field of Cultural Heritage science, the use of non-destructive and contact-free techniques has increased sharply over the past 10 years. Compared to conventional spectroscopic and imaging techniques such as X-ray, Ultraviolet (UV), Infrared (IR) and laser spectroscopy, terahertz time-domain imaging (THz-TDI) is an innovative, non-invasive and safe technique, which provides good penetration depth (~1 cm) and broad spectral bandwidth (0.1-10 THz). This paper sets out the protocol and methodology for the application of THz-TDI to immovable Cultural Heritage, illustrated by a series of case studies. The case studies demonstrate the efficacy of the technique in providing structural and material information for conservators.
Applied Sciences
In recent years, THz imaging techniques have been used in several fields of application. At the beginning of the century, the low availability of powerful THz sources was one of the limiting factors to the advancement of THz technology. At the ENEA center in Frascati, two Free Electron Lasers (FELs) operating in the THz spectral region were available at that time, making it possible to exploit all the features of THz imaging. In this paper, we will describe an alternative THz imaging technique, developed over 15 years of studies at the ENEA center of Frascati, and its application in the art conservation field, reporting the latest results of such studies on the optical properties of pigments in the GHz-THz region of the spectrum, on the possibility of detecting biological weeds under mosaic tiles and on the THz analysis of ancient leather wallpapers. This alternative technique was first developed in the framework of a bilateral collaboration between Japan and Italy, the THz-ARTE Pro...
Real-time terahertz imaging for art conservation science
Journal of the European Optical Society: Rapid Publications, 2008
A new real-time terahertz imaging system has been developed by using a quantum cascade laser source and a microbolometer focal plane detector array. The application to non-invasive analyses of cultural heritage is demonstrated with an oil paint specimen. The experimental results suggested that the terahertz imaging system can identify materials based on a spectral database with a spatial resolution of about 300 µm. The transmission imaging indicated the difference between natural and artificial ultramarine pigments. Since the size of the system is similar to a common portable infrared camera, it can be used at the place where the object is located, such as museums, and can contribute to conservation activities, such as drying process monitoring. This real-time, small, non-invasive terahertz imaging system can be used in various fundamental research fields and practical industries.
A Survey of Terahertz Applications in Cultural Heritage Conservation Science
IEEE Transactions on Terahertz Science and Technology, 2011
The authors present a review of the advances that have been made to establish terahertz applications in the cultural heritage conservation sector over the last several years. This includes material spectroscopy, 2D and 3D imaging and tomographic studies, using a broad range of terahertz sources demonstrating the breadth and application of this burgeoning community.