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835 results on '"Zhao, Yuejin"'

4. Wide-spectrum optical synthetic aperture imaging via spatial intensity interferometry

Author

Chu, Chunyan, Liu, Zhentao, Chen, Mingliang, Shao, Xuehui, Zhao, Yuejin, and Han, Shensheng

Subjects
Physics - Optics, Astrophysics - Instrumentation and Methods for Astrophysics
Abstract

High resolution imaging is achieved using increasingly larger apertures and successively shorter wavelengths. Optical aperture synthesis is an important high-resolution imaging technology used in astronomy. Conventional long baseline amplitude interferometry is susceptible to uncontrollable phase fluctuations, and the technical difficulty increases rapidly as the wavelength decreases. The intensity interferometry inspired by HBT experiment is essentially insensitive to phase fluctuations, but suffers from a narrow spectral bandwidth which results in a lack of detection sensitivity. In this study, we propose optical synthetic aperture imaging based on spatial intensity interferometry. This not only realizes diffraction-limited optical aperture synthesis in a single shot, but also enables imaging with a wide spectral bandwidth. And this method is insensitive to the optical path difference between the sub-apertures. Simulations and experiments present optical aperture synthesis diffraction-limited imaging through spatial intensity interferometry in a 100 $nm$ spectral width of visible light, whose maximum optical path difference between the sub-apertures reach $69.36\lambda$. This technique is expected to provide a solution for optical aperture synthesis over kilometer-long baselines at optical wavelengths.

Published
2022

24. Terahertz Non-Destructive Testing and Imaging of High-Voltage Cables

Author

Zhang Zhenwei, Xu Jing, Jia Rui, Wu Yinghong, Guan Hao, Han Siyi, Zhang Cunlin, and Zhao Yuejin

Subjects
terahertz, terahertz imaging, non-destructive testing, frequency modulated continuous wave, cross-linked polyethylene, 110.2970, Physics, QC1-999
Abstract

The evaluation of the internal defects in high-voltage cross-linked polyethylene cables is highly crucial for the security and reliability of power transmission. Here, a terahertz (THz) frequency-modulated-continuous-wave non-destructive testing (NDT) imaging system is used to demonstrate the non-contact detection of a high-voltage cable (35 KV). Combined with linear scanning and axial rotation, the three-dimensional (3D) data of the columnar target is acquired, and a 3D perspective image is reconstructed. The correspondence between the target in the real space and image space is determined to accurately show the internal spiral structure and strand number of metal wires. The results indicate that prefabricated air and water holes in the polyethylene insulation layer can be displayed. Furthermore, feature defect signals are automatically classified and recognised by combining the principal component analysis dimension reduction method and the support vector machine classification method, which can predict abnormal defects more efficiently in mass data. These results provide technical guidance for the non-contact NDT and visual evaluation of the internal state of detected cable targets.

Published
2022
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