Abstract-Restoration of integrated circuit terahertz image based on wavelet denoising technique and the point spread function model

 

Zhirui Zhang, Yao Lua,  Cixing Lv, Qi Mao, Song long Wang, Shihan Yan, 

https://www.sciencedirect.com/science/article/abs/pii/S0143816620311878

In recent years, terahertz (THz) imaging technology has attracted much attention in the detection of the integrated circuit (IC). However, limited by the hardware of the imaging system, THz images often contain a significant amount of noise, which impairs the quality of the image details. The THz image is also degraded due to the long wavelength. In this study, we propose a novel method for THz image restoration. We first apply a wavelet denoising technique to process the THz time-frequency signal. The point spread function (PSF) is then mathematically modeled to restore the details of the IC image, as the degradation of the THz image can be regarded as the convolution process of the object equation and PSF. Finally, we compare the performance between the restored THz images before and after wavelet denoising. The results demonstrate that the restored image after denoising performs better in peak signal-to-noise ratio and visual improvements, proving the practicability and precision of our proposed method.

Abstract-Image fusion based on multiscale transform and sparse representation to enhance terahertz images

Qi Mao, Yunlong Zhu, Cixing Lv, Yao Lu, Xiaohui Yan, Dongshan Wei, Shihan Yan, and Jingbo Liu

Schematic diagram of the fusion method based on MST and SR.

https://www.osapublishing.org/oe/abstract.cfm?uri=oe-28-17-25293

High-quality terahertz (THz) images are vital to integrated circuit (IC) manufacturing. Due to the unique sensitivity of THz waves to different materials, the images obtained from the point-spread function (PSF) model have fewer image details and less texture information in some frequency bands. This paper presents an image fusion technique to enhance the resolution of THz IC images. The source images obtained from the PSF model are processed by a fusion method combining a multiscale transform (MST) and sparse representation (SR). The low-pass band is handled by sparse representation, and the high-pass band is fused by the conventional “max-absolute” rule. From both objective and visual perspectives, four popular multiscale transforms—the Laplacian pyramid, the ratio of low-pass pyramids, the dual-tree complex wavelet transform and the curvelet transform—are thoroughly compared at different decomposition levels ranging from one to four. This work demonstrates the feasibility of using image fusion to enhance the resolution of THz IC images.

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

Abstract-Single-cell terahertz spectral characteristics in simulated scattering near-field imaging mode

Jie Wang, Shihan Yan, Zaoxia Li, Ziyi Zang, Xingxing Lu, and Hong-Liang Cui

Schematic of the coupled tip–cell model system.

https://www.osapublishing.org/osac/abstract.cfm?URI=osac-3-8-2096

Spectral imaging of a single cell with terahertz (THz) wave is valuable in determination of its physiological state for cell-based precision diagnosis, as THz photon energy is in tune with the vibration-rotation and conformation related excitations of cellular material, and THz absorption is extremely sensitive to the state and degree of hydration of a cell. Because of the severe mismatch between the cell size and the THz wavelength, such imaging has to be carried out in the near-field modality. To make the design and performance assessment of a THz near-field spectral imager effective and systematic, we simulate the scattering THz near-field signals of tumor cells by strictly controlling cell model parameters with representative physiological states. The results demonstrate that the specific physiological characteristics from intracellular hydration state, nucleocytoplasmic ratio, and cell geometric morphology of tumor cells can be characterized quantitatively by their discrepant dielectric response in the THz band, correlating THz near-field scattering signal from a cell with the latter’s corresponding physicochemical state.

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

Abstract-Single cell imaging with near‐field terahertz scanning microscopy

Zaoxia Li, Shihan Yan, Ziyi Zang, Guoshuai Geng, Zhongbo Yang, Jiang Li, Lihua Wang, Chunyan Yao, Hong‐Liang Cui, Chao Chang, Huabin Wang

https://onlinelibrary.wiley.com/doi/full/10.1111/cpr.12788

Objectives

Terahertz (THz)‐based imaging techniques hold great potential for biological and biomedical applications, which nevertheless are hampered by the low spatial resolution of conventional THz imaging systems. In this work, we report a high‐performance photoconductive antenna microprobe‐based near‐field THz time‐domain spectroscopy scanning microscope.

Materials and methods

A single watermelon pulp cell was prepared on a clean quartz slide and covered by a thin polyethylene film. The high performance near‐field THz microscope was developed based on a coherent THz time‐domain spectroscopy system coupled with a photoconductive antenna microprobe. The sample was imaged in transmission mode.

Results

We demonstrate the direct imaging of the morphology of single watermelon pulp cells in the natural dehydration process with our near‐field THz microscope.

Conclusions

Given the label‐free and non‐destructive nature of THz detection techniques, our near‐field microscopy‐based single‐cell imaging approach sheds new light on studying biological samples with THz.

Abstract-Convolutional neural network model based on terahertz imaging for integrated circuit defect detections

Qi Mao, Yunlong Zhu, Cixing Lv, Yao Lu, Xiaohui Yan, Shihan Yan, and Jingbo Liu

(a)Schematic of the T-Gauge 5000 system, (b) physical diagram of the THz-TDS system operating in the transmission mode.

https://www.osapublishing.org/oe/abstract.cfm?uri=oe-28-4-5000

Detection of integrated circuit (IC) defects is vital in IC manufacturing. Traditional defect detection methods have relied on scanning electron microscopy and X-ray imaging techniques that are time consuming and destructive. Hence, in this paper we considered terahertz imaging as a label-free and nondestructive alternative. This study aimed to use a convolutional neural network model (CNN) to improve the performance of the terahertz imaging IC detection system. First, we constructed a terahertz imaging IC dataset and analyzed it. Subsequently, a new CNN structure was proposed based on the VGG16 network. Finally, it was optimized based on its structure and dropout rate. The method proposed above can improve IC defects detection accuracy of THz imaging. Most significantly, this work will promote the application of terahertz imaging in practice and provide a foundation to further research in relevant fields.

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

Abstract-Temperature- and pH-dependent protein conformational changes investigated by terahertz dielectric spectroscopy

Ziyi Zang, Shihan Yan, Xiaohui Han, Dongshan Wei. Hong-Liang Cui, Chunlei Du,




https://www.sciencedirect.com/science/article/pii/S1350449518305267

Polypeptides and protein drugs have received enormous attention from pharmaceutical industry, medical sector and consumer groups because of a favourable combination of their bioactivity, specificity and overall success rate for the treatment of a variety of diseases. The efficacy and safety of drugs may be degraded due to fluctuating environmental factors, accompanied by changes of the natural conformation of protein. Thus, it is necessary and meaningful to evaluate drug status before use. To that end, the evolving new and pre-existing protein activity/conformation technologies have proven to ensure the safety of drug use consistently. Recently, terahertz time-domain spectroscopy (THz-TDS) has demonstrated suitability for label-free and non-destructive detection of polypeptide and protein conformational changes. In this paper, THz optical parameters of pepsin solutions under different temperatures and with varying pH are measured to demonstrate the feasibility and the considerable potential of THz spectroscopic method in detecting protein drugs. In cases where temperature or pH change is apparent, the THz absorption coefficient, the refractive index, and the dielectric loss tangent change noticeably, independently verified by enzyme activity testing. These findings strongly support the conclusion that THz spectroscopy of pepsin solutions can be used for qualitative analysis to identify the folding or unfolding of protein drugs caused by changes of environmental factors, laying the foundation of a new label-free method for quality control of protein drugs.

Abstract-Characterization of Nucleobases in Broadband Terahertz Spectra from 0.5 to 10 THz with the Air-Biased-Coherent-Detection Technique

Miao, Shihan Yan, Yong-qiang Sun , Wang Sheng, Fu Tang , Xiao-yu Peng, Yuan Hu

Figure 1. Experimental setup of the broadband THz-TDS based on the THz-ABCD technique.

https://www.mdpi.com/1424-8220/19/5/1148/htm

Terahertz time-domain spectroscopy (THz-TDS) is an effective coherent detection technique for deeply understanding the structures and functions of biomolecules. However, generally not full information in the whole THz range can be obtained due to the limited detection bandwidth (usually less than 5 THz) of the traditional THz-TDS systems. In this paper, effective THz absorption spectra in 0.5–10 THz range of five typical nucleobases of DNA/RNA are characterized with a super broadband THz detection technique, called the air-biased- coherent-detection (THz-ABCD) technique. Few unexpected characteristic absorption peaks appeared in the low-frequency region and meanwhile a series of anticipated characteristic absorption peaks are found in the high-frequency region. The fingerprint spectra of these nucleobases are helpful for further analysis on the vibration and twisting behavior of hydrogen bonds, van der Waals and electrostatic forces etc. between and within DNA/RNA biomolecules.

Abstract-Terahertz Spectroscopic Signatures of Microcystin Aptamer Solution Probed with a Microfluidic Chip

Mingkun Zhang, Zhongbo Yang, Mingjie Tang , Deqiang Wang , Huabin Wang, Shihan Yan , Dongshan Wei,  Hong-Liang Cui

https://www.mdpi.com/1424-8220/19/3/534

Terahertz signature detection of biological samples in aqueous solution remains a great challenge due to the strong terahertz absorption of water. Here we propose a new preparation process for fabricating a microfluidic chip and use it as an effective sensor to probe the terahertz absorption signatures of microcystin aptamer (a linear single-stranded DNA with 60 nucleotides) dissolved in TE buffer with different concentrations. The microfluidic chip made of silicon includes thousands of 2.4 μm × 2.4 μm square-cross-section channels. One repeatable terahertz absorption signature is detected and recognized around 830 GHz, fitted to a Lorentz oscillator. This signature is theorized to originate from the bending of hydrogen bonds formed between adjacent hydrated DNA bases surrounded by water molecules. Furthermore, the low-lying vibrational modes are also investigated by molecular dynamics simulations which suggest that strong resonant oscillations are highly probable in the 815–830 GHz frequency band

Abstract-Temporal and Spatial Variability of Water Status in Plant Leaves by Terahertz Imaging

Zheyu Song,  Shihan Yan,   Ziyi Zang,  Yun Fu, Dongshan Wei,  Hong-Liang Cui,  Puxiang Lai,

https://ieeexplore.ieee.org/document/8403254/

Water and its distribution and transport dynamics in green plant leaves are vital to the growth of plants. Owing to the high sensitivity of terahertz (THz) wave to water, THz spectroscopy has great advantages in analyzing the water status of plant leaves. This paper presents a new approach to estimate the water status of plant leaves by the THz time-domain spectroscopy (THz-TDS) technique. Spatial distribution of THz transmission amplitudes located in vein xylem and mesophyll of all three kinds of leaves including wintersweet, ginkgo, and bamboo is detected by THz-TDS measurements. Based on the transmission amplitude, reconstructed THz images show that the water loss in the basal leaf region is more than that in the distal region during the natural drying process for all three plants. A good agreement is reached between the THz imaging method and the direct water weight measurement. To illustrate the accuracy and the sensitivity of the THz technique, the temporal and spatial variations of the water content in the damaged ginkgo leaf with a wound by cutting are also investigated for comparison. The water flow from the basal region to the distal region of the leaf is inferred according to the variation of THz transmission amplitude with the leaf region in different dehydration periods, which is consistent with the string-of-lakes model prediction. This paper shows the feasibility of using THz technology to monitor the temporal and spatial variability of the water status in plant leaves.

Abstract-Terahertz time-domain spectroscopy of chondroitin sulfate

Changcheng Shi, Yuting Ma, Jin Zhang, Dongshan Wei, Huabin Wang, Xiaoyu Peng, Mingjie Tang, Shihan Yan, Guokun Zuo, Chunlei Du, and Hongliang Cui

https://www.osapublishing.org/boe/abstract.cfm?uri=boe-9-3-1350&origin=search

Chondroitin sulfate (CS), derived from cartilage tissues, is an important type of biomacromolecule. In this paper, the terahertz time-domain spectroscopy (THz-TDS) was investigated as a potential method for content detection of CS. With the increase of the CS content, the THz absorption coefficients of the CS/polyethylene mixed samples linearly increase. The refractive indices of the mixed samples also increase when the CS content increases. The extinction coefficient of CS demonstrates the THz frequency dependence to be approximately the power of 1.4, which can be explained by the effects of CS granular solids on THz scattering.

© 2018 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

Abstract-Label-free protein detection using terahertz time-domain spectroscopy

Xiaohui Han, Shihan Yan, Ziyi Zang, Dongshan Wei, Hong-Liang Cui, and Chunlei Du

https://www.osapublishing.org/boe/abstract.cfm?uri=boe-9-3-994

Protein analysis is the foundation to understanding the mechanisms of complex biological processes. As one of the most widely used techniques to determine protein species and contents, protein dot blot aids biology research but needs corresponding antibodies for marking. A label-free detection method based on terahertz time-domain spectroscopy (THz-TDS) is proposed and demonstrated to improve this traditional technology. A membrane loaded with protein samples is directly scanned using a transmission THz-TDS system for spectral imaging. Different kinds of proteins can be distinguished by the refractive index extracted from the THz transmission spectrum. The intensity or shade imaged with the THz transmission spectrum can help detect the protein quantitatively. The feasibility of this new protein assay is demonstrated by the results of systematic testing with actual samples prepared with the dot-blot protocol.

© 2018 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

Abstract-Detection of DNA oligonucleotides with base mutations by terahertz spectroscopy and microstructures

Mingjie Tang,  Mingkun Zhang, Shihan Yan,  Liangping Xia, Zhongbo Yang, Chunlei Du, Hong-Liang Cui, Dongshan Wei,

http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0191515

DNA oligonucleotides with a 5-base mutation at the 3'-terminus were investigated by terahertz (THz) spectroscopy in a marker-free manner. The four single-stranded oligonucleotides with 17nt have been detected with specificity on a microfluidic chip, and corroborated by spectral measurements with split-ring resonators. The number of hydrogen bonds formed between the oligonucleotide and its surrounding water molecules, deemed a key contribution to the THz absorption of biological solutions, was explored by molecular dynamics simulations to explain the experimental findings. Our work underlies the feasibility of THz spectroscopy combined with microstructures for marker-free detection of DNA, which may form the basis of a prospective diagnostic tool for studying genic mutation.