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-A synthetic approach to weathering degree classification of stone relics case study of the Yungang Grottoes

Tianhua Meng, Yuhe Lu, Guozhong Zhao, Chengquan Yang, Jianguang Ren,  Yunlong Shi

https://heritagesciencejournal.springeropen.com/articles/10.1186/s40494-017-0165-y

Classification of the weathering degree of large outdoor stone relics has long been a challenge in their protection engineering. An approach to classifying the weathering levels of the Yungang Grottoes is presented in this paper. This approach is based on combined terahertz (THz) spectra and ultrasonic velocity and the use of a least squares support vector machine (LS-SVM). A regression model for prediction of the weathering level was established using the optimal values of parameters determined by the double cross-validation (D-CV) method. This SVM regression prediction model (SVMRPM) predicts the weathering levels of the grottoes with relative errors of 8.16% or less. The SVMRPM can also be used to predict the weathering levels of some areas where ultrasonic testing is extremely difficult; the THz spectra can easily be obtained using approximately 0.2 g of sample material. This method is a highly efficient and economical technique for determining the degree of weathering of large exposed stone relics.

Abstract-Terahertz Imaging Progress at Capital Normal University

Guozhong Zhao, Jiayi Yu, Yashang Li, Jia Wang,

http://www.sciencepublishinggroup.com/journal/paperinfo?journalid=302&doi=10.11648/j.ijass.20170505.12

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 (THz-TDS). A practical focus-plane imaging system is built up based on the THz-TDS with the probe-beam-expanded electro-optical sampling and an infrared CCD imaging. The active terahertz continuous wave imaging is based on a CO₂-laser-pumped terahertz coherent source and an uncooled bolometer array of terahertz camera. The active terahertz polarization imaging and wave front imaging is developed. For the passive terahertz imaging, the low frequency of radiometers are used to detect the point-to-point beam-scanned terahertz signal by the optical focusing and scanning system so that the passive THz imaging is realized for the security inspection of human body. The related components and image processing methods are studied and used for the improvement of imaging speed and resolution. The research on THz imaging technology at Capital Normal University is opening up a potential application in the field of non-destructive testing and security inspection for the terahertz technology.

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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.

Abstract-The frequency selectivity of double H-shaped metallic structures

Xiaoxia Bu, Guozhong Zhao

Capital Normal Univ. (China)

http://proceedings.spiedigitallibrary.org/proceeding.aspx?articleid=1809344

Proc. SPIE 9043, 2013 International Conference on Optical Instruments and Technology: Optoelectronic Devices and Optical Signal Processing, 90430V (December 23, 2013); doi:10.1117/12.2036478

This paper presents the design and numerical simulation of the double H-shaped metallic periodic structure based on finite difference time domain (FDTD) method in terahertz frequency range. The double H-shaped structure unit cell consists of two H structures overlapped in the same plane. Numerical simulation results show that the double H-shaped structure results in a distinct and strong transmission trap in 0.2～3.0THz range. The position and the full wave at half maximum (FWHM) of transmission trap are changed with different structure size. The surface current distribution of structure is numerical simulated, which clarifies the frequency selection mechanism of the transmission spectra. © (2013) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.

Abstract-The frequency selectivity of double H-shaped metallic structures

Xiaoxia Bu, Guozhong Zhao

Capital Normal Univ. (China)

http://proceedings.spiedigitallibrary.org/proceeding.aspx?articleid=1809344

Proc. SPIE 9043, 2013 International Conference on Optical Instruments and Technology: Optoelectronic Devices and Optical Signal Processing, 90430V (December 23, 2013); doi:10.1117/12.2036478

From Conference Volume 9043

• 2013 International Conference on Optical Instruments and Technology: Optoelectronic Devices and Optical Signal Processing
• Yi Dong; Xiaoyi Bao; Chao Lu; Xiangjun Xin; Scott S. Yam; Xuping Zhang

This paper presents the design and numerical simulation of the double H-shaped metallic periodic structure based on finite difference time domain (FDTD) method in terahertz frequency range. The double H-shaped structure unit cell consists of two H structures overlapped in the same plane. Numerical simulation results show that the double H-shaped structure results in a distinct and strong transmission trap in 0.2～3.0THz range. The position and the full wave at half maximum (FWHM) of transmission trap are changed with different structure size. The surface current distribution of structure is numerical simulated, which clarifies the frequency selection mechanism of the transmission spectra. © (2013) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.