Depth super-resolved imaging of infrastructure defects using a terahertz-wave interferometer

Momiyama, Homare; Sasaki, Yu; Yoshimine, Isao; Nagano, Shigenori; Yuasa, Tetsuya; Otani, Chiko

doi:10.1016/j.ndteint.2021.102431

Cited by 5 publications

(2 citation statements)

References 18 publications

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“…[45][46][47][48] The light-like directness of THz provides high spatial resolution and radio wave-like trans-parency for soft materials. [49][50][51] These characteristics allow for fluoroscopic imaging, including X-ray imaging, to be conducted at low energy levels with minimal exposure, and micrometersized metal detection is possible. In addition, similar to IR spectroscopy, a vibrational spectrum (fingerprint spectrum) derived from a molecular structure can be quickly identified through THz spectroscopy because intra-and intermolecular vibrations exist in the THz frequency region.…”

Section: Introductionmentioning

confidence: 99%

Broadband Photodetectors and Imagers in Stretchable Electronics Packaging

Araki

Suzuki

et al. 2023

Advanced Materials

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The integration of flexible electronics with optics can help realize a powerful tool that facilitates the creation of a smart society wherein internal evaluations can be easily performed nondestructively from the surface of various objects that is used or encountered in daily lives. Here, organic‐material‐based stretchable optical sensors and imagers that possess both bending capability and rubber‐like elasticity are reviewed. The latest trends in nondestructive evaluation equipment that enable simple on‐site evaluations of health conditions and abnormalities are discussed without subjecting the targeted living bodies and various objects to mechanical stress. Real‐time performance under real‐life conditions is becoming increasingly important for creating smart societies interwoven with optical technologies. In particular, the terahertz (THz)‐wave region offers a substance‐ and state‐specific fingerprint spectrum that enables instantaneous analyses. However, to make THz sensors accessible, the following issues must be addressed: broadband and high‐sensitivity at room temperature, stretchability to follow the surface movements of targets, and digital transformation compatibility. The materials, electronics packaging, and remote imaging systems used to overcome these issues are discussed in detail. Ultimately, stretchable optical sensors and imagers with highly sensitive and broadband THz sensors can facilitate the multifaceted on‐site evaluation of solids, liquids, and gases.

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Section: Introductionmentioning

confidence: 99%

Broadband Photodetectors and Imagers in Stretchable Electronics Packaging

Araki

Suzuki

et al. 2023

Advanced Materials

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“…Other ranging techniques now use the frequency-modulated continuous-wave (FMCW) radar principle [ 1 , 2 , 3 , 4 ], the amplitude-modulated continuous-wave (AMCW) radar principle [ 5 , 6 ], interferometry [ 7 ], or computed tomography [ 8 ]. In recent years, a new technique has been added to the arsenal of terahertz-wave ranging: the optical coherence tomography (OCT), either in its original form, the time-domain (TD) OCT, in which a low-coherence (wide-spectrum) light source is used [ 9 ], or the source-swept (SS) OCT, relying on a tunable monochromatic source [ 10 , 11 , 12 ]. This report is a contribution to the SS-OCT type of radar.…”

Section: Introductionmentioning

confidence: 99%

Discrete Fourier Transform Radar in the Terahertz-Wave Range Based on a Resonant-Tunneling-Diode Oscillator

Konno

Dobroiu

Suzuki

et al. 2021

Sensors

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We used a resonant-tunneling-diode (RTD) oscillator as the source of a terahertz-wave radar based on the principle of the swept-source optical coherence tomography (SS-OCT). Unlike similar reports in the terahertz range, we apply the stepwise frequency modulation to a subcarrier obtained by amplitude modulation instead of tuning the terahertz carrier frequency. Additionally, we replace the usual optical interference with electrical mixing and, by using a quadrature mixer, we can discriminate between negative and positive optical path differences, which doubles the measurement range without increasing the measurement time. To measure the distance to multiple targets simultaneously, the terahertz wave is modulated in amplitude at a series of frequencies; the signal returning from the target is detected and homodyne mixed with the original modulation signal. A series of voltages is obtained; by Fourier transformation the distance to each target is retrieved. Experimental results on one and two targets are shown.

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