Nondestructive measurement of layer structures in dielectric substrates by collimated terahertz time domain spectroscopy

Tojima, Yuya; Sudo, Hiroki; Kubota, Tomijiro; Cho, Keizo; Nakabayashi, Hiroaki; Suizu, Koji

doi:10.1587/elex.15.20180579

Cited by 2 publications

(2 citation statements)

References 11 publications

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“…Figure 1 shows the arrangement of the 2D experimental system. 20,25,26) A THz pulse transmitter was located at a fixed angle 30°of θ T , and a receiver was moved along a circular arc using a rotation stage over 0 to 90°of θ R . The sample was set in an imaging area centered at the pivot point of the system, and the position of the sample was aligned in the x-y plane using a liner stages.…”

Section: Imaging Methodsmentioning

confidence: 99%

Terahertz imaging for multiple reflectors using time-domain correlating synthesis method

Sato

Toh

Suizu

2018

Jpn. J. Appl. Phys.

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We had proposed a correlating synthesis method for terahertz imaging using a pulse reflection mode terahertz time-domain spectrometry system. The efficiency of the method for improving the resolution and eliminating fake images was verified by numerical simulations and experiments with two metal cylinders. However, an artifact image between the two reflectors is markedly shown. Moreover, the multi-reflection and the influence of echo distortion caused by the directivity of the terahertz beam have not been discussed. For application of imaging complicated target, this paper addresses following issues: 1) multi-reflection between reflectors, as well as the effect of the direction of polarization of terahertz wave; 2) distortion of echo signals from targets distributed in a broader area, as well as the effect of concave lenses. Finally, the efficiencies of these proposals are verified by an imaging experiment with five metal cylinders.

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Section: Imaging Methodsmentioning

confidence: 99%

Terahertz imaging for multiple reflectors using time-domain correlating synthesis method

Sato

Toh

Suizu

2018

Jpn. J. Appl. Phys.

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“…The application of the terahertz nondestructive testing method in thickness monitoring has now become one of the most mature technologies in its numerous applications. It can already be used in industrial applications and has attracted wide attention from all parties [42][43][44][45][46]. Hot-rolled oxide scale consist of wüstite, hematite and magnetite, and the wüstite is the chief component among them, and the proportion of wüstite is as high as 58% to 95% under different heat treatment conditions [2,[47][48][49].…”

Section: Introductionmentioning

confidence: 99%

Novel Terahertz Nondestructive Method for Measuring the Thickness of Thin Oxide Scale Using Different Hybrid Machine Learning Models

Chen

et al. 2020

Coatings

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Effective control of the thickness of the hot-rolled oxide scale on the surface of the steel strip is very vital to ensure the surface quality of steel products. Hence, terahertz nondestructive technology was proposed to measure the thickness of thin oxide scale. The finite difference time domain (FDTD) numerical simulation method was employed to obtain the terahertz time-domain simulation data of oxide scale with various thickness (0–15 μm). Added Gaussian white noise with a Signal Nosie Reduction (SNR) of 10 dB was used when simulating real test signals, using four wavelet denoising methods to reduce noise and to compare their effectiveness. Two machine learning algorithms were adopted to set up models to achieve this goal, including the classical back-propagation (BP) neural network algorithm and the novel extreme learning machine (ELM) algorithm. The principal component analysis (PCA) algorithm and particle swarm optimization (PSO) algorithm were combined to reduce the dimensions of the terahertz time-domain data and improve the robustness of the machine learning model. It could be clearly seen that the novel hybrid PCA-PSO-ELM model possessed excellent prediction performance. Finally, this work proposed a novel, convenient, online, nondestructive, noncontact, safety and high-precision thin oxide scale thickness measuring method that could be employed to improve the surface quality of iron and steel products.

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Nondestructive measurement of layer structures in dielectric substrates by collimated terahertz time domain spectroscopy

Cited by 2 publications

References 11 publications

Terahertz imaging for multiple reflectors using time-domain correlating synthesis method

Terahertz imaging for multiple reflectors using time-domain correlating synthesis method

Novel Terahertz Nondestructive Method for Measuring the Thickness of Thin Oxide Scale Using Different Hybrid Machine Learning Models

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