Passive imaging of concealed objects in terahertz and long-wavelength infrared

Kowalski, Marcin; Kastek, M.; Walczakowski, Michał; Pałka, Norbert; Szustakowski, Mieczysław

doi:10.1364/ao.54.003826

Cited by 47 publications

(21 citation statements)

References 19 publications

(20 reference statements)

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“…Data augmentation has been applied. Our previous studies [60,62] show that the ability to detect the concealed object with the infrared and terahertz cameras is decreasing for long-lasting experiments. The detection algorithm provided bounding box for every detected object in the image.…”

Section: Resultsmentioning

confidence: 99%

Hidden Object Detection and Recognition in Passive Terahertz and Mid-wavelength Infrared

Kowalski

2019

J Infrared Milli Terahz Waves

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The study presents the comparison of detection and recognition of concealed objects covered with various types of clothing by using passive imagers operating in a terahertz (THz) range at 1.2 mm (250 GHz) and a mid-wavelength infrared (MWIR) at 3-6 μm (50-100 THz). During this study, large dataset of images presenting various items covered with various types of clothing has been collected. The detection and classification algorithms aimed to operate robustly at high processing speed across these two spectrums. Properties of both spectrums, theoretical limitations, performance of imagers and physical properties of fabrics in both spectral domains are described. The paper presents a comparison of two deep learningbased processing methods. The comparison of the original results of various experiments for the two spectrums is presented.

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Section: Resultsmentioning

confidence: 99%

Hidden Object Detection and Recognition in Passive Terahertz and Mid-wavelength Infrared

Kowalski

2019

J Infrared Milli Terahz Waves

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“…THz TDS is powerful for material spectroscopy, layer inspection, and transmission imaging of packaged objects. 2 THz-TDS systems are utilized in authentication, [3][4][5] nondestructive inspection, [6][7][8][9][10][11][12][13][14][15][16][17] three-dimensional (3-D) imaging, [18][19][20] quality control, [21][22][23][24][25] airport security, [26][27][28][29][30][31][32] art investigations, [33][34][35][36] detecting damages on wood caused by insects, 37 tomography, [38][39][40][41][42][43] characterization of astrophysical ice, 44 biomedical diagnosis and imaging, [45][46][47][48][49]…”

Section: Introductionmentioning

confidence: 99%

Survey of terahertz photonics and biophotonics

et al. 2020

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We review the advances of terahertz (THz) science and technology in biophotonics, including related challenges and solutions. The main impediment to THz spectroscopy and imaging in this field is the high absorption of the THz beam in water. Hence, transmission imaging and spectroscopy of thick wet tissue using THz radiation has generally been quite difficult. However, the absorption of THz waves by water molecules is so strong that increasing the power of the THz source can lead to structural and functional changes in tissues, so solutions must go beyond a larger power output. In terms of resolution, THz imaging is superior to ultrasound but inferior to visible light microscopy. Owing to its unique material analysis capabilities, promising diagnosis applications have been demonstrated through THz imaging and spectroscopy. Unfortunately, many applications are limited by beam penetration depth and resolution. Hence, researchers from a wide variety of scientific and technical fields have been actively improving these features through the development of electronic devices and materials. In addition, groundbreaking optical architecture and materials to reduce beam absorption in the optics of a system and generate focused beams with smaller diameters have been proposed. On the software side, image processing techniques to computationally enhance the resolution and quality of THz imaging have been proposed. Data science and machine learning to automate the diagnosis of defects and diseases through processing THz images and spectroscopy data have been proposed. We have reviewed the applications of THz radiation in biophotonics and research achievements toward advancing these applications. A conclusion with a roadmap toward increasing the footprint of the THz technology in biophotonics is also proposed.

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“…15 THz-TDS systems are powerful tools for material spectroscopy, layer inspection, and transmission imaging of packaged objects. 16 These capabilities of THz-TDS systems are utilized in authentication, [17][18][19] nondestructive inspection of composite materials, [20][21][22][23][24][25][26][27][28] threedimensional imaging, [29][30][31][32] metrology and quality control of industrial products, [33][34][35][36][37] detection of concealed weapons, [38][39][40][41][42][43][44][45] art investigations, 46,47 tomography, [48][49][50][51][52] biomedical diagnosis, [53][54][55][56] material characterization, [57][58][59][60][61][62] thickness measurement, …”

Section: Introductionmentioning

confidence: 99%

Review of GaN-based devices for terahertz operation

Ahi

2017

Opt. Eng

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Abstract. GaN provides the highest electron saturation velocity, breakdown voltage, operation temperature, and thus the highest combined frequency-power performance among commonly used semiconductors. The industrial need for compact, economical, high-resolution, and high-power terahertz (THz) imaging and spectroscopy systems are promoting the utilization of GaN for implementing the next generation of THz systems. As it is reviewed, the mentioned characteristics of GaN together with its capabilities of providing high two-dimensional election densities and large longitudinal optical phonon of ∼90 meV make it one of the most promising semiconductor materials for the future of the THz emitters, detectors, mixers, and frequency multiplicators. GaNbased devices have shown capabilities of operation in the upper THz frequency band of 5 to 12 THz with relatively high photon densities in room temperature. As a result, THz imaging and spectroscopy systems with high resolution and deep depth of penetration can be realized through utilizing GaN-based devices. A comprehensive review of the history and the state of the art of GaN-based electronic devices, including plasma heterostructure field-effect transistors, negative differential resistances, hetero-dimensional Schottky diodes, impact avalanche transit times, quantum-cascade lasers, high electron mobility transistors, Gunn diodes, and tera field-effect transistors together with their impact on the future of THz imaging and spectroscopy systems is provided.

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Passive imaging of concealed objects in terahertz and long-wavelength infrared

Cited by 47 publications

References 19 publications

Hidden Object Detection and Recognition in Passive Terahertz and Mid-wavelength Infrared

Hidden Object Detection and Recognition in Passive Terahertz and Mid-wavelength Infrared

Survey of terahertz photonics and biophotonics

Review of GaN-based devices for terahertz operation

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