Component analysis of chemical mixtures using terahertz spectroscopic imaging

Watanabe, Yuuki; Kawase, Kodo; Ikari, Tomofumi; Ito, Hiromasa; Ishikawa, Y.; Minamide, Hiroaki

doi:10.1016/j.optcom.2004.02.032

Cited by 80 publications

(35 citation statements)

References 14 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In the literature at least three different two-dimensional (2D) THz imaging techniques can be found, each suitable for different applications. These techniques can be divided into two groups as shown in Figure 1C: the first one is in the time domain and the other two, multispectral imaging (37) and spatial distribution map (38,39), are in the frequency domain. The obtained time-domain THz image does not contain any spectroscopic information; thus, this type of imaging is suitable only for detection purposes.…”

Section: Terahertz Systems and Techniquesmentioning

confidence: 99%

“…The time-domain THz image is constructed based on key parameters-for example, maximum amplitude-which is obtained from the THz time-domain waveform, whereas multispectral imaging is performed using Fourier transform of the time-domain waveform to obtain the spectral frequency dimension, allowing imaging at different frequencies (2,37). By upgrading this technique with a component spatial pattern analysis method, the enhanced THz images can be obtained, indicating the separation of the spatial patterns of individual substance within heterogeneous samples from multispectral THz images at different THz frequencies, as shown in the last row in Figure 1C (38,39). However, the THz imaging has garnered a lot of attention to development of novel spectroscopic imaging techniques, not only in 2D but also in three dimensions (3D), during the last decade.…”

Section: Terahertz Systems and Techniquesmentioning

confidence: 99%

See 1 more Smart Citation

Applications of Terahertz Spectroscopy in the Field of Construction and Building Materials

Abina

Puc

Jeglic

et al. 2014

Applied Spectroscopy Reviews

View full text Add to dashboard Cite

In last two decades, rapid development in the field of terahertz (THz) technology has opened new possibilities for creating innovative imaging and sensing systems. Although the applications of THz technology in different sectors constantly increase, the construction industry lags behind them. The aim of this article is to review the current applications of THz spectroscopy in research and industry related to construction and building materials, along with the key drawbacks of technology and recommendationsfor future use. The review concludes that THz spectroscopy and imaging have promising potential and provide many opportunities for applications in construction and building materials characterization.

show abstract

Section: Terahertz Systems and Techniquesmentioning

confidence: 99%

Section: Terahertz Systems and Techniquesmentioning

confidence: 99%

Applications of Terahertz Spectroscopy in the Field of Construction and Building Materials

Abina

Puc

Jeglic

et al. 2014

Applied Spectroscopy Reviews

View full text Add to dashboard Cite

show abstract

“…As a first cut at viewing the identification process one can look at it as a two-dimensional space with the different metrics (ways to compare spectra) along one axis and the spectral characteristics (which processed form of the raw spectrum) along the second axis. Common methods include principal component analysis (PCA) and spectral angle mapping (SAM) [5], [7], [9], [14], although also other methods have been used [12]. As to what to compare, there are several options, the raw spectrum, the raw spectrum normalized by a reference spectrum (transmission coefficient), and the absorbance.…”

Section: Introductionmentioning

confidence: 99%

Robust Identification of Concealed Dangerous Substances by Spectral Correlation of Terahertz Transmission Images

Rheenen

Haakestad

2015

IEEE Trans. THz Sci. Technol.

View full text Add to dashboard Cite

Abstract-Terahertz images containing spectral information in each pixel are recorded in transmission mode using a fibercoupled time-domain spectroscopy system. The images are acquired by mounting a sample holder on an x-y stage, which is stepped across the beam in the two transverse directions, while the transmitted THz waveform is captured. The materials under investigation consist of uncovered and hidden samples of an explosive (RDX) and simulants (lactose and tartaric acid). Spectral angle mapping is used to identify the materials in the Terahertz images by comparing the spectrum in each pixel with a library of reference spectra for the different materials. We test the performance of several spectral characteristics derived from the measured transmission spectra. Robustness is studied by investigating the Receiver-Operating-Characteristics (ROCs). The ROCs are used to find which of the spectral characteristics is most robust to different sample preparation conditions, without the need for extensive pre-treatment of the data, such as baseline correction. Simple theoretical considerations are used to support the experimental results.

show abstract

“…Obviously, all these issues have been realized before and there is a vast body of literature [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17] on identifying substances by comparing their spectra. Spectral features have been measured in numerous wavelength bands corresponding to the energies of the transitions of interest.…”

Section: Introductionmentioning

confidence: 99%

Robust identification of concealed dangerous substances using THz imaging spectroscopy

Nystad

Haakestad

Rheenen

2015

Terahertz Physics, Devices, and Systems IX: Advanced Applications in Industry and Defense

View full text Add to dashboard Cite

False alarm rates must be kept sufficiently low if a method to detect and identify objects or substances is to be implemented in real life applications. This is also true when trying to detect and identify dangerous substances such as explosives and drugs that are concealed in packaging materials. THz technology may be suited to detect these substances, especially when imaging and spectroscopy are combined. To achieve reasonable throughput, the detection and identification process must be automated and this implies reliance on algorithms to perform this task, rather than human beings. The identification part of the algorithm must compare spectral features of the unknown substance with those in a library of features and determining the distance, in some sense, between these features. If the distance is less than some defined threshold a match is declared. In this paper we consider two types of spectral characteristic that are derived from measured time-domain signals measured in the THz regime: the absorbance and its derivative. Also, we consider two schemes to measure the distance between the unknown and library characteristics: Spectral Angle Mapping (SAM) and Principal Component Analysis (PCA). Finally, the effect of windowing of the measured time-domain signal on the performance of the algorithms is studied, by varying the Blackman-Harris (B-H) window width. Algorithm performance is quantified by studying the receiver-operating characteristics (ROC). For the data considered in this study we conclude that the best performance is obtained when the derivative of the absorbance is used in combination with a narrow B-H window and SAM. SAM is a more straight-forward method and requires no large training data sets and tweaking.

show abstract

Component analysis of chemical mixtures using terahertz spectroscopic imaging

Cited by 80 publications

References 14 publications

Applications of Terahertz Spectroscopy in the Field of Construction and Building Materials

Applications of Terahertz Spectroscopy in the Field of Construction and Building Materials

Robust Identification of Concealed Dangerous Substances by Spectral Correlation of Terahertz Transmission Images

Robust identification of concealed dangerous substances using THz imaging spectroscopy

Contact Info

Product

Resources

About