scholarly journals High-Resolution Bistatic ISAR Imaging of a Space Target with Sparse Aperture

Electronics ◽  
2019 ◽  
Vol 8 (8) ◽  
pp. 874
Author(s):  
Lin Shi ◽  
Xiaoxiu Zhu ◽  
Chaoxuan Shang ◽  
Baofeng Guo ◽  
Juntao Ma ◽  
...  
Keyword(s):  
High Resolution ◽  
Compress Sensing ◽  
Target Image ◽  
Unknown Parameters ◽  
Large Size ◽  
Isar Imaging ◽  
Bayesian Inference Method ◽  
Resolution Imaging ◽  
Sparse Aperture

Due to the large size of space targets, migration through resolution cells (MTRC) are induced by a rotational motion in high-resolution bistatic inverse synthetic aperture radar (Bi-ISAR) systems. The inaccurate correction of MTRC degrades the quality of Bi-ISAR images. However, it is challenging to correct the MTRC where sparse aperture data exists for Bi-ISAR systems. A joint approach of MTRC correction and sparse high-resolution imaging for Bi-ISAR systems is presented in this paper. First, a Bi-ISAR imaging sparse model-related to MTRC is established based on compress sensing (CS). Second, the target image elements and noise are modeled as the complex Laplace prior, and the Gaussian prior, respectively. Finally, the high-resolution, well-focused image is obtained by the full Bayesian inference method, without manual adjustments of unknown parameters. Simulated results verify the effectiveness and robustness of the proposed algorithm.

scholarly journals High-Resolution ISAR Imaging With Sparse Aperture VFM Waveforms Under Low SNR Condition

IEEE Access ◽  
2019 ◽  
Vol 7 ◽  
pp. 110651-110659
Author(s):  
Jiyuan Chen ◽  
Letao Xu ◽  
Xiaoyi Pan ◽  
Pu Zheng ◽  
Shunping Xiao
Keyword(s):  
High Resolution ◽  
Low Snr ◽  
Isar Imaging ◽  
Sparse Aperture

scholarly journals High Resolution Imaging of Compact Radio Sources by Gridding with Regularization

1998 ◽  
Vol 164 ◽  
pp. 411-412 ◽  
Author(s):  
S. F. Likhachev ◽  
R. M. Hjellming
Keyword(s):  
High Resolution ◽  
Image Reconstruction ◽  
Radio Source ◽  
Radio Sources ◽  
High Resolution Imaging ◽  
Traditional Methods ◽  
Compact Radio Source ◽  
Ill Posed ◽  
Resolution Imaging

AbstractThe problem of VLBI image reconstruction is a classical example of an ill-posed problem. A new procedure of gridding with regularization has been developed. This procedure was used in traditional methods (CLEAN, Hybrid) to improve the quality of compact radio source images. A few sources (GRO J1655–40, RY Scuti and Cyg X-1), observed with the VLA and VLBA, were processed with this procedure.

Hankel Matrix Completion Approach for High-resolution ISAR Imaging with Sparse Aperture

2021 ◽  
Author(s):  
Bangjie Zhang ◽  
Gang Xu ◽  
Lizhong Jiang ◽  
Rui Zhou ◽  
Yanyang Liu ◽  
...  
Keyword(s):  
High Resolution ◽  
Matrix Completion ◽  
Hankel Matrix ◽  
Isar Imaging ◽  
Sparse Aperture

Fabrication and Characterization of Gold Nano-gaps for ssDNA Immobilization and Hybridization Detection

2011 ◽  
Vol 14 (3) ◽  
pp. 191-196 ◽  
Author(s):  
Th. S. Dhahi ◽  
U. Hashim ◽  
N. M. Ahmed ◽  
H. Nazma
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
High Resolution ◽  
Conformational Changes ◽  
Electrical Contact ◽  
Resolution Enhancement ◽  
Transmission Electron ◽  
Resolution Imaging

We develop a method for fabricating the nano-gaps directly by using just photolithography and wet etching processes without any nano lithography or difficult techniques. It shows that this resolution enhancement allows one to fabricate metal electrodes with separation from arbitrarily large to fewer than one hundred nanometers. Furthermore, because these nano-gaps are on a thin film, they can be imaged with high-resolution transmission electron microscopy (HRTEM). Efforts toward achieving electrical contact to nanostructures have been active for over a decade. Even though several devices based on “nano-gaps” – two gaps separated by a nanometer-scale distance - have been demonstrated, their realization has remained a significant challenge. Even the best methods are highly labor-intensive and suffer from low yield and poor geometrical control. Most nano-gaps are also incompatible with high resolution transmission electron microscopy (HRTEM) and scanning electron microscopy (SEM). As a consequence, the proof of the nano-gap quality and content in past studies has been indirect. High-resolution imaging is therefore required to ensure the quality of nano-gaps and to be able to identify possible artifacts. This project presents a unique vertical nano-gap biosensor that can detect changes in DNA structure. Using a size reduction to interrogate samples between the nano-scale gaps, this biosensor will be sensitive enough to record the conformational changes for ss-DNA.

scholarly journals Image Enhancement by Histogram Specification Using Multiple Target Images

2011 ◽  
pp. 29-37
Author(s):  
Pavithra P ◽  
Ramyashree N ◽  
Shruthi T.V ◽  
Dr. Jharna Majumdar
Keyword(s):  
High Resolution ◽  
Image Enhancement ◽  
Input Image ◽  
Multiple Target ◽  
Target Image ◽  
Image Histogram ◽  
Histogram Specification ◽  
High Resolution Images

Shape and characteristics of the histogram plays a major role in finding the quality of an image. Histogram Specification is an image enhancement technique, where the histogram of the input image is transformed to a pre-specified histogram derived from a high resolution image, called target image. In this paper, the classical histogram specification technique is extended by using a target image which is obtained by fusing multiple high resolution images. A set of Quality Metrics were identified to assess the quality of the output enhanced image. The paper addresses the following issues: a) Effect of varying the number of target images on the quality of the output enhanced image b) Role of using different methods of fusion on the quality of the output enhanced image c) Category of the target image on the quality of the output enhanced image. If the input image is from a forest, whether in order to obtain an enhanced image, all target images has to be selected from the forest category d) Effect of preprocessing of target image on the quality of the output enhanced image.

Alternative approaches to ultra-high resolution imaging

1991 ◽  
Vol 49 ◽  
pp. 650-651
Author(s):  
J.M. Cowley
Keyword(s):  
High Resolution ◽  
High Voltage ◽  
High Resolution Electron Microscopy ◽  
Crystal Defects ◽  
High Resolution Imaging ◽  
General Applicability ◽  
Resolution Electron ◽  
Radiation Resistant ◽  
Resolution Imaging ◽  
Alternative Approaches

By extrapolation of past experience, it would seem that the future of ultra-high resolution electron microscopy rests with the advances of electron optical engineering that are improving the instrumental stability of high voltage microscopes to achieve the theoretical resolutions of 1Å or better at 1MeV or higher energies. While these high voltage instruments will undoubtedly produce valuable results on chosen specimens, their general applicability has been questioned on the basis of the excessive radiation damage effects which may significantly modify the detailed structures of crystal defects within even the most radiation resistant materials in a period of a few seconds. Other considerations such as those of cost and convenience of use add to the inducement to consider seriously the possibilities for alternative approaches to the achievement of comparable resolutions.

Principle and practice of high-resolution imaging with a field-emission TEM

1992 ◽  
Vol 50 (1) ◽  
pp. 138-139
Author(s):  
Max T. Otten ◽  
Wim M.J. Coene
Keyword(s):  
High Resolution ◽  
Field Emission ◽  
Incidence Angle ◽  
Temporal Coherence ◽  
Energy Spread ◽  
High Resolution Imaging ◽  
Major Improvement ◽  
High Resolution Images ◽  
Resolution Imaging

High-resolution imaging with a LaB6 instrument is limited by the spatial and temporal coherence, with little contrast remaining beyond the point resolution. A Field Emission Gun (FEG) reduces the incidence angle by a factor 5 to 10 and the energy spread by 2 to 3. Since the incidence angle is the dominant limitation for LaB6 the FEG provides a major improvement in contrast transfer, reducing the information limit to roughly one half of the point resolution. The strong improvement, predicted from high-resolution theory, can be seen readily in diffractograms (Fig. 1) and high-resolution images (Fig. 2). Even if the information in the image is limited deliberately to the point resolution by using an objective aperture, the improved contrast transfer close to the point resolution (Fig. 1) is already worthwhile.

Imaging of ferroelectric domain walls by electron holography

1992 ◽  
Vol 50 (1) ◽  
pp. 246-247
Author(s):  
Xiao Zhang
Keyword(s):  
Magnetic Field ◽  
High Resolution ◽  
Domain Walls ◽  
Ferroelectric Domain ◽  
Object Wave ◽  
Electron Holography ◽  
High Resolution Imaging ◽  
Quantitative Measurements ◽  
Resolution Imaging ◽  
Electron Microscopes

Electron holography has recently been available to modern electron microscopy labs with the development of field emission electron microscopes. The unique advantage of recording both amplitude and phase of the object wave makes electron holography a effective tool to study electron optical phase objects. The visibility of the phase shifts of the object wave makes it possible to directly image the distributions of an electric or a magnetic field at high resolution. This work presents preliminary results of first high resolution imaging of ferroelectric domain walls by electron holography in BaTiO3 and quantitative measurements of electrostatic field distribution across domain walls.

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