Abstract-Passive terahertz imaging detectors based on antenna-coupled high-electron-mobility transistors

Jiandong Sun, Yifan Zhu, Wei Feng, Qingfeng Ding, Hua Qin, Yunfei Sun, Zhipeng Zhang, Xiang Li, Jinfeng Zhang, Xinxing Li, Yang Shangguan, and Lin Jin

 (a) Scanning-electron micrograph of the detector with schematic measurement circuitry. (b) Zoom-in view of the central active region including the gate and the field-effect channel. (c, d) Backside and front-side views of the silicon hyperhemispherical lens with a detector chip assembled on the planar surface in a liquid nitrogen dewar with a TPX window.

https://www.osapublishing.org/oe/abstract.cfm?uri=oe-28-4-4911

Aiming at the requirement of passive terahertz imaging, we report a high-sensitivity terahertz detector based on an antenna-coupled AlGaN/GaN high-electron-mobility transistor (HEMT) at 77 K without using low-noise terahertz amplifier. The measured optical noise-equivalent power and the noise-equivalent temperature difference of the detector were about 0.3pW/Hz−−−√$0.3\mathrm{p}\mathrm{W}/\sqrt{\mathrm{H}\mathrm{z}}$ and 370 mK in a 200 ms integration time over a bandwidth of 0.7 − 0.9 THz, respectively. By using this detector, we demonstrated passive terahertz imaging of room-temperature objects with signal-to-noise ratio up to 13 dB. Further improvement in the sensitivity may allow passive terahertz imaging using AlGaN/GaN-HEMT at room temperature.

© 2020 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

Abstract-Image denoising and enhancement of terahertz passive imaging

Yashang Li; Guozhong Zhao

https://www.spiedigitallibrary.org/conference-proceedings-of-spie/11179/111790X/Image-denoising-and-enhancement-of-terahertz-passive-imaging/10.1117/12.2539884.short

The wavelength of the terahertz is between the infrared and the microwave, and the photon energy is low, so it has great application prospects in security inspection. In order to further improve the target resolution of terahertz passive imaging system, A terahertz image enhancement method based on a block matching and three-dimensional and weighted Schatten-p norm minimization is proposed to improve the image resolution of terahertz passive imaging system. It uses three-dimensional matched filtering to remove image noise on the basis of mean filtering, and then adopts Lucy Richardson algorithm and weighted Schatten-p norm minimization for image restoration. Finally, the convolution filter is used to enhance image details and the background of the image is subtracted by the edge detection. The method of paper significantly enhances the image contrast and increases system resolution from 2cm to 1.5cm, effectively improving system performance

© (2019) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only

Abstract-Using Markov constraint and constrained least square filter to develop a novel method of passive terahertz image restoration

Yuanmeng Zhao, Xiao Sun, Cunlin Zhang, Yuejin Zhao,

https://iopscience.iop.org/article/10.1088/1742-6596/1187/4/042094

In recent years, passive terahertz imaging has gained significant attention in both research and practice. One big challenge with passive terahertz imaging is its low-quality images with high level of noise. State-of-the art image restoration methods have been developed for image denoising, such as methods based on Markov constraint and regular filter methods. Building upon these two methods, this paper develops a novel method for passive terahertz image restoration which preserves well both high frequency and low frequency information of the images. Performance of our method is evaluated using two common image criteria of the image sharpness, i.e. edge intensity and definition. Experimental results showed our method outperform state-of-the art methods for passive terahertz image restoration.

Abstract-Study of Automatic Detection of Concealed Targets in Passive Terahertz Images for Intelligent Security Screening

Rui Li,  Chao Li, Hongwei Li, Shiyou Wu, Guangyou Fang

https://ieeexplore.ieee.org/document/8586961

The automatic extraction of the targets in which we are interested from a given image is the fundamental of the automatic detection and identification for security screening systems based on imaging technologies. Suffering from the comparatively low signal-to-noise ratio (SNR), the automatic detection of targets in a passive terahertz (THz) imaging system facing great challenges, but in urgent necessary. In this paper, a comprehensive method for automatic detection of concealed targets in passive THz image by making the best use of the “block statistics uniformity” properties of the passive images is first studied. A theoretical model for the “featured regions” decomposition based on the minimization of a “fit energy” functional with respect to a “surface function” is established, to overcome the drawbacks of conventional methods with gradient-based edge operators for their unsuccessful application in low SNR passive images with blurred boundaries. Based on earlier theoretical basis and taking advantages of the distinguished contrasts of the convergent “surface function” in different “featured regions,” an automatic detection algorithm with three steps was further developed to automatically extract the number, the locations and the shapes of all the concealed targets, with the shape of each target derived as the contour point series arranged in clockwise direction. With plenty of experimental results in 0.2 THz band, it is found that, the proposed method has high detection accuracy about 95% with quite good realtime performance, even for the single channel proof-of-state system with low SNR. The theorem, algorithm, and results, in this paper, may have important applications in unmanned and intelligent security screening systems without any artificial interventions.

Port Authority tests new security tech that scans passersby

Port Authority officers test out new technology that can scan passersby. (Robert Miller)

By Allie Griffin

https://nypost.com/2018/08/14/port-authority-tests-new-security-tech-that-scans-passersby/

Port Authority officers on Tuesday tested new technology that can scan passersby – and possibly head off a gun-toting or bomb-carrying terrorist.

Cops at the Port Authority Bus Terminal had eyes glued to their laptops, keeping tabs on green millimeter wave and red terahertz images captured by camera-like devices made by UK-based Thruvision Group.

Port Authority officials said they have high hopes for these gadgets because it can spot someone carrying suspicious items under their clothes from 10 meters away.

“This is another level of security,” said PA police Superintendent Edward Cetnar.

Officers tested the Thruvision equipment Monday and Tuesday and are set to employ it again on Wednesday.

The PA wouldn’t commit to buying the equipment or say when it could be fully installed.

Authorities said this kind of technology could be crucial in fighting terrorists – like ISIS-inspired Akayed Ullah, who tried to blow himself up at the Port Authority Bus Terminal this past Dec. 11.

Abstract-Design and Characterisation of Titanium Nitride Subarrays of Kinetic Inductance Detectors for Passive Terahertz Imaging

Dmitry Morozo, Simon M. Doyle, Archan Banerjee, Thomas L. R. Brien, Dilini HemakumaraIain,  G. Thayne, Ken Wood, Robert H. Hadfield

https://link.springer.com/article/10.1007%2Fs10909-018-2023-z

We report on the investigation of titanium nitride (TiN) thin films deposited via atomic layer deposition (ALD) for microwave kinetic inductance detectors (MKID). Using our in-house ALD process, we have grown a sequence of TiN thin films (thickness 15, 30, 60 nm). The films have been characterised in terms of superconducting transition temperature Tc$T_{\mathrm{c}}$, sheet resistance Rs$R_{\mathrm{s}}$and microstructure. We have fabricated test resonator structures and characterised them at a temperature of 300 mK. At 350 GHz, we report an optical noise equivalent power NEPopt≈2.3×10−15 W/Hz−−−√${\text{NEP}}_{\mathrm{o}\mathrm{p}\mathrm{t}}\approx 2.3\times {10}^{-15}\text{W}/\sqrt{\text{Hz}}$, which is promising for passive terahertz imaging applications.

Abstract-Effective algorithm based on Fourier transform for the passive THz image quality enhancement

Vyacheslav A. Trofimov,  Vladislav V. Trofimov,  Ivan L. Shestakov,  Roman G. Blednov,  Valentine Yu. Kovalev,

https://www.spiedigitallibrary.org/conference-proceedings-of-spie/10209/1020907/Effective-algorithm-based-on-Fourier-transform-for-the-passive-THz/10.1117/12.2267861.pdf

We propose new approach for THz image quality enhancing using correlation function (convolution function) between Fourier transform of the image under consideration and Fourier transform of a standard image which can be enough complex. It is very important to stress that a standard image choosing allows us to remove essentially spurious parts of the image.

We discuss one more possibility to remove noise from background of the image as well as possibility of the image decomposition and its reconstruction.

Xinjiang installs body scanners at checkpoints

A picture of the body security scanner installed in Tumxuk, Xinjiang Uyghur Autonomous Region. Photo: Zhao Yusha/GT

http://www.globaltimes.cn/content/1068368.shtml

New scanner avoids physical contact between police and travelers

Xinjiang will use a new high-tech body security scanner for road security checks, a move to enhance counter-terrorism work before the forthcoming 19th National Congress of the Communist Party of China (CPC).

A division from the People's Liberation Army in Tumxuk, Northwest China's Xinjiang Uyghur Autonomous Region, recently introduced 10 units of terahertz security scanners, which were installed at road security checkpoints.

"It took these scanners only 10 seconds to scan one person, while the traditional hand-held scanner takes almost 50 seconds to complete the task," Xu Yongsheng, vice head of a road security check station, told the Global Times on Tuesday.

Once the person steps into the body scanner, he or she is required to turn around, and an alarm will go off if the scanner detects metal or explosive objects.

Xu said the new scanner protects the police as they do not need to have physical contact with those being examined.

"We used to get into conflict with people when we examined them with hand-held scanners, especially women," Xu noted.

A local Uyghur named Rozi, who had to undergo the scanner several times when passing through the station, said the new scanner is more convenient as it saves him time and protects his privacy.

Xu noted many people are concerned about the possible health risks the machine might pose.

"The human body naturally transmits terahertz waves, which can be received by the terahertz body scanner. So unlike traditional X-rays, it has no harmful effects," Li Gang, president of Beijing Aerospace Yilian Science & Technology Development Company, the manufacturer of the scanner, told the Global Times on Tuesday.

Major battlefields

Li said the Xinjiang military contacted him in February about introducing the machines "to meet the counter-terrorism demands in Xinjiang."

Tumxuk and Kashgar are the gateways and major battlefields for Xinjiang's security work. The two cities are inhabited by many ethnic minority groups which move freely in large numbers every day, Qin Wenrong, a Xinjiang military officer, told the Global Times.

Qin said that the Tumxuk government has invested heavily in these scanners to enhance their counter-terrorism work ahead of the upcoming 19th National Congress of the CPC, which will convene in Beijing on October 18.

Qin said all 35 security checkpoints in Tumxuk will be equipped with the scanners in the future.

Meng Jianzhu, a member of the Political Bureau of the CPC Central Committee and head of the Commission for Political and Legal Affairs of the CPC Central Committee, called for the use of new technologies to fight terrorism during his inspection in Xinjiang in August.

Apart from body scanners, Qin said that the Tumxuk government conducted massive security checks throughout the city a few days ago and urged government officials to pay attention to suspicious signs, such as a sudden increase of strangers in homes.

Xinjiang has witnessed sporadic violent incidents.

In February, three knife-wielding attackers killed five and injured another five in Pishan county, Hotan prefecture, the Hotan government said on its website. Tumxuk is around 600 kilometers north of Hotan. 

Abstract-New progress of active and passive terahertz imaging

Guozhong Zhao, Jia Wang, Jiayi Yu

Capital Normal Univ. (China)

Yanchun Shen

Capital Normal Univ. (China)

Proc. SPIE 10030, Infrared, Millimeter-Wave, and Terahertz Technologies IV, 100300Q (December 8, 2016); doi:10.1117/12.2246784

http://proceedings.spiedigitallibrary.org/proceeding.aspx?articleid=2593072


The progress on terahertz imaging at Capital Normal University in Beijing is presented. Our works on Terahertz Imaging include the active and passive imaging. For the active terahertz imaging, the pulse and continue wave terahertz imaging are studied, respectively. The active terahertz pulse imaging is based on the terahertz time-domain spectroscopy with the probe-beam-expanded femtosecond pulse laser and an infrared CCD detection.
 The active terahertz continuous wave imaging is based on a CO2-laser-pumped terahertz coherent source and a NEC terahertz camera. The active terahertz polarization imaging is studied. For the passive terahertz imaging, the low frequency radiometers are used to detect the beam-scanned terahertz signal by the point-to-point scanning. The related components and image processing methods are developed and used for the improvement of imaging speed and resolution.
 © (2016) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.