Terahertz waves in cultural heritage: imaging results via the fiber-coupled terahertz time domain system

2015 ◽  
Author(s):  
Ilaria Catapano
Keyword(s):  
Cultural Heritage ◽  
Time Domain ◽  
Terahertz Waves ◽  
Imaging Results

THz imaging in the frame of the Archaeological Urban Park of Naples project

2020 ◽  
Author(s):  
Ilaria Catapano ◽  
Carlo Noviello ◽  
Giovanni Ludeno
Keyword(s):  
Data Processing ◽  
Cultural Heritage ◽  
Time Domain ◽  
Imaging Techniques ◽  
Urban Park ◽  
Thz Imaging ◽  
Terahertz Waves ◽  
Non Invasive ◽  
Processing Chain ◽  
Molecular Stability

<p>The Archaeological Urban Park of Naples (PAUN) project aims at addressing the need of analytical information relating to cultural heritage with modalities that encourage innovation systems of protection and enhancement. In this frame, one of the specific goals is the testing of multiple non-invasive or only minimally invasive investigation techniques, aimed at identifying a permanent diagnostic system calibrated to the specific context of the Urban Archaeological Park of Piazza Municipio, Napoli, Italy.</p><p>Among the electromagnetic sensing technologies, those exploiting Terahertz waves (1THz = 10<sup>12</sup> Hz) are the newest among the imaging techniques, which offers the attractive chance of characterizing the inner features of manmade objects with a sub-millimeter spatial resolution in a non-invasive way while assuring negligible long-term risks to the molecular stability of the exposed objects.</p><p>This possibility together with the recent development of compact, transportable and easily reconfigurable devices make THz imaging a more and more widespread considered investigation tool in the frame of cultural heritage. THz imaging allows, indeed, the gaining of information useful to improve knowledge about the design technique adopted by the artist and to detect possible damages affecting the conservation state of precious artworks [1].</p><p>In the frame of PAUN project, THz imaging is considered as part of the sensor network, which is dedicated to the material characterization and supports the conservation and use of the assets of the Urban Archaeological Park of Piazza Municipio. Specifically, THz imaging is adopted to analyze ancient decorated mortar specimens and gather information on their stratigraphy. At this regard, it is worth pointing out that the effectiveness of THz imaging, i.e. the capability of obtaining high resolution images of the object under test, is dependent not only on the performances of the hardware technology but also on the data processing approaches. Herein, we consider the time domain Z-Omega Fiber-Coupled Terahertz Time Domain (FICO) system, which is available at IREA-CNR, and a data processing chain specifically designed to improve the discrimination of different material layers and to reconstruct the inner features characterizing the investigated artworks [2].</p><p> </p><p>[1] Fukunaga, THz Technology Applied to Cultural Heritage in Practice, Cultural Heritage Science, Springer.</p><p>[2] Catapano, I., Soldovieri, F. A Data Processing Chain for Terahertz Imaging and Its Use in Artwork Diagnostics. J Infrared Milli Terahz Waves 38, 518–530 (2017).</p><p> </p><p>Acknowledge: Authors would like to thank the PAUN project “Archaeological Urban Park of Naples” by which the present work has been financed.</p><p> </p>

scholarly journals Three-Dimensional Imaging of Terahertz Circular SAR with Sparse Linear Array

Sensors ◽  
2018 ◽  
Vol 18 (8) ◽  
pp. 2477 ◽  
Author(s):  
Jubo Hao ◽  
Jin Li ◽  
Yiming Pi
Keyword(s):  
3D Imaging ◽  
Linear Array ◽  
Ground Plane ◽  
Three Dimensional ◽  
Terahertz Waves ◽  
Recovery Method ◽  
Imaging Algorithm ◽  
Imaging Geometry ◽  
Imaging Results ◽  
Sparse Linear Array

Due to the non-contact detection ability of radar and the harmlessness of terahertz waves to the human body, three-dimensional (3D) imaging using terahertz synthetic aperture radar (SAR) is an efficient method of security detection in public areas. To achieve high-resolution and all aspect imaging, circular trajectory movement of radar and linear sensor array along the height direction were used in this study. However, the short wavelength of terahertz waves makes it practically impossible for the hardware to satisfy the half-wavelength spacing condition to avoid grating lobes. To solve this problem, a sparse linear array model based on the equivalent phase center principle was established. With the designed imaging geometry and corresponding echo signal model, a 3D imaging algorithm was derived. Firstly, the phase-preserving algorithm was adopted to obtain the 2D image of the ground plane for each sensor. Secondly, the sparse recovery method was applied to accomplish the scattering coefficient reconstruction along the height direction. After reconstruction of all the range-azimuth cells was accomplished, the final 3D image was obtained. Numerical simulations and experiments using terahertz radar were performed. The imaging results verify the effectiveness of the 3D imaging algorithm for the proposed model and validate the feasibility of terahertz radar applied in security detection.

scholarly journals Decay curve analysis for data error quantification in time-domain induced polarization imaging

Geophysics ◽  
2018 ◽  
Vol 83 (2) ◽  
pp. E75-E86 ◽  
Author(s):  
Adrian Flores Orozco ◽  
Jakob Gallistl ◽  
Matthias Bücker ◽  
Kenneth H. Williams
Keyword(s):  
Time Domain ◽  
Decay Curve ◽  
Induced Polarization ◽  
Curve Analysis ◽  
Real Field ◽  
Acquisition Time ◽  
Transfer Resistance ◽  
Imaging Results ◽  
Error Characterization ◽  
Data Error

In recent years, the time-domain induced polarization (TDIP) imaging technique has emerged as a suitable method for the characterization and the monitoring of hydrogeologic and biogeochemical processes. However, one of the major challenges refers to the resolution of the electrical images. Hence, various studies have stressed the importance of data processing, error characterization, and the deployment of adequate inversion schemes. A widely accepted method to assess data error in electrical imaging relies on the analysis of the discrepancy between normal and reciprocal measurements. Nevertheless, the collection of reciprocals doubles the acquisition time and is only viable for a limited subset of commonly used electrode configurations (e.g., dipole-dipole [DD]). To overcome these limitations, we have developed a new methodology to quantify the data error in TDIP imaging, which is entirely based on the analysis of the recorded IP decay curve and does not require recollection of data (e.g., reciprocals). The first two steps of the methodology assess the general characteristics of the decay curves and the spatial consistency of the measurements for the detection and removal of outliers. In the third and fourth steps, we quantify the deviation of the measured decay curves from a smooth model for the estimation of random error of the total chargeability and transfer resistance measurement. The error models and imaging results obtained from this methodology — in the following referred to as “decay curve analysis” — are compared with those obtained following a conventional normal-reciprocal analysis revealing consistent results. We determine the applicability of our methodology with real field data collected at the floodplain scale (approximately 12 ha) using multiple gradient and DD configurations.

scholarly journals Time-domain imaging system in the terahertz range for immovable cultural heritage materials

Strain ◽  
2018 ◽  
Vol 55 (2) ◽  
pp. e12292
Author(s):  
David Giovannacci ◽  
Hoi Ching Cheung ◽  
Gillian C. Walker ◽  
John W. Bowen ◽  
Dominique Martos-Levif ◽  
...  
Keyword(s):  
Cultural Heritage ◽  
Time Domain ◽  
Imaging System ◽  
Terahertz Range

scholarly journals Terahertz Spectroscopy and Imaging Detection of Defects in Civil Aircraft Composites

2020 ◽  
Vol 2020 ◽  
pp. 1-8
Author(s):  
Mian Zhong ◽  
Bingwei Liu ◽  
Chen Li ◽  
Zhiqi Wang ◽  
Dongshan Wei ◽  
...  
Keyword(s):  
Frequency Domain ◽  
Time Domain ◽  
Spectral Characteristics ◽  
Low Velocity Impact ◽  
Quantitative Detection ◽  
Detection Frequency ◽  
Imaging Results ◽  
Civil Aircraft ◽  
The Impact ◽  
Detection Of Defects

Composite materials have increasingly become a high proportion of the structural weight of aircraft due to their excellent performances. Different types of damages may occur in the aircraft service period, which will bring potential safety risks to aircrafts. To investigate the defect damage detection and its spectral characteristics and imaging of carbon-fiber-reinforced polymer composite laminates, defects from the low-velocity impact damage in composites were measured by the THz time-domain reflection imaging system. Results show that there exists obvious THz spectral differences between the impact damaged defects and nondefect. The effective detection frequency band for the low-speed impact damaged defect is 0.12–2.0 THz. In the time domain, there are attenuations and delays in the spectra of defects relative to those of nondefects. In the frequency domain, with the increase of frequency, the power spectral density of the defect first increases and then decreases, and the absorption coefficient increases slowly. In general, the imaging results in time-domain imaging are better than those from the frequency-domain imaging, which not only is suitable for the qualitative detection of defects but also has great potential and application prospects in quantitative detection. This work shows an important guide for the application of THz technology to detect the composite material defects in civil aircraft.

scholarly journals Antenna Modeling and Reconstruction Accuracy of Time Domain-Based Image Reconstruction in Microwave Tomography

2013 ◽  
Vol 2013 ◽  
pp. 1-14 ◽  
Author(s):  
Andreas Fhager ◽  
Shantanu K. Padhi ◽  
Mikael Persson ◽  
John Howard
Keyword(s):  
Image Reconstruction ◽  
Time Domain ◽  
Tap Water ◽  
Antenna System ◽  
Scattering Data ◽  
Electromagnetic Model ◽  
Imaging Results ◽  
Highly Nonlinear ◽  
Modeling Errors ◽  
The Impact

Nonlinear microwave imaging heavily relies on an accurate numerical electromagnetic model of the antenna system. The model is used to simulate scattering data that is compared to its measured counterpart in order to reconstruct the image. In this paper an antenna system immersed in water is used to image different canonical objects in order to investigate the implication of modeling errors on the final reconstruction using a time domain-based iterative inverse reconstruction algorithm and three-dimensional FDTD modeling. With the test objects immersed in a background of air and tap water, respectively, we have studied the impact of antenna modeling errors, errors in the modeling of the background media, and made a comparison with a two-dimensional version of the algorithm. In conclusion even small modeling errors in the antennas can significantly alter the reconstructed image. Since the image reconstruction procedure is highly nonlinear general conclusions are very difficult to make. In our case it means that with the antenna system immersed in water and using our present FDTD-based electromagnetic model the imaging results are improved if refraining from modeling the water-wall-air interface and instead just use a homogeneous background of water in the model.

Creation of Titania Artificial Interfaces with Geometric Patterns by Using Micro Stereolithography and Aqueous Solution Techniques

2012 ◽  
Vol 2012 (CICMT) ◽  
pp. 000117-000122
Author(s):  
Soshu Kirihara ◽  
Yousuke Itakura ◽  
Satoko Tasaki
Keyword(s):  
Time Domain ◽  
Anatase Phase ◽  
Far Infrared ◽  
Terahertz Wave ◽  
Terahertz Waves ◽  
Glass Substrates ◽  
Geometric Patterns ◽  
Water Solvent ◽  
Micro Patterning ◽  
Geometric Arrangements

Titania micro patterns with periodic arrangements were formed on glass substrates successfully for electromagnetic wave energy resonations and localizations in terahertz frequency ranges. Geometric arrangements of acryl polygon tablets with titania particles dispersions by using micro patterning stereolithography. Moreover, periodically arranged full titania tablets with anatase phase were created homogeneously though liquid phase crystal depositions of water solvent processes under micro templates fabricated by using the stereolithography system. The terahertz wave properties were measured and simulated by a using time domain spectroscopic system and finite difference time domain method. The terahertz waves having micrometer order wavelengths and belonging in far-infrared frequency ranges are expected to apply for various types of novel sensors which can detect micro cracks on materials surfaces, micro defects in electric devices, bacteria in foods, and cancer cells in human skins.

Ultrafast Magnetization Reversal Dynamics on A Micrometer-Scale Thin Film Element Studied by Time Domain Imaging

2000 ◽  
Vol 648 ◽  
Author(s):  
B.C. Choi ◽  
G. Ballentine ◽  
M. Belov ◽  
W.K. Hiebert ◽  
M.R. Freeman
Keyword(s):  
Domain Wall ◽  
Time Domain ◽  
Magnetization Reversal ◽  
Switching Time ◽  
Magnetization Vector ◽  
Domain Wall Motion ◽  
Time Resolved ◽  
Imaging Results ◽  
Resonance Frequencies ◽  
The Time Domain

AbstractPicosecond time scale magnetization reversal dynamics in a 15nm thick Ni80Fe20 microstructure (10μm×2μm) is studied using time-resolved scanning Kerr microscopy. The time domain images reveal a striking change in the magnetization reversal mode, associated with the dramatic reduction in switching time when the magnetization vector is pulsed by a longitudinal switching field while a steady transverse biasing field is applied to the sample. According to the time domain imaging results, the abrupt change of the switching time is due to the change in the magnetization reversal mode; i.e., the nucleation dominant reversal process is replaced by domain wall motion if transverse biasing field is applied. Furthermore, magnetization oscillations subsequent to reversal are observed at two distinct resonance frequencies, which sensitively depend on the biasing field strength. The high frequency resonance at f=2 GHz is caused by damped precession of the magnetization vector, whereas another mode at f≈0.8 GHz is observed to arise from domain wall oscillation.

High-Sensitivity High-Resolution Full-Wafer Imaging of the Properties of Large n-Type SiC Using the Relative Reflectance of Two Terahertz Waves

2014 ◽  
Vol 778-780 ◽  
pp. 491-494 ◽  
Author(s):  
Akihide Hamano ◽  
Seigo Ohno ◽  
Hiroaki Minamide ◽  
Hiromasa Ito ◽  
Yoshiyuki Usuki
Keyword(s):  
Silicon Carbide ◽  
Relaxation Time ◽  
Carrier Density ◽  
High Sensitivity ◽  
Thz Imaging ◽  
Terahertz Waves ◽  
Large N ◽  
Imaging Results ◽  
Standard Values ◽  
Precision And Accuracy

THz imaging was performed in 2 s intervals with 1 mm resolution on a 3 in., 0.42 mm thick, as-cut n-type Silicon Carbide wafer. Carrier density, relaxation time, mobility, and resistivity obtained from imaging results are 0.91 × 1018 cm-3, 4.36 × 10-14 s, 218 cm2V-1s-1, and 3.14 × 10-2 Ωcm, respectively. Compared with the standard values provided by the manufacturers, the results suggest that THz imaging has reliable precision and accuracy.

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