Study of resolution and super resolution in electromagnetic imaging for half-space problems

It has been observed that super resolution is possible in the electromagnetic imaging. In the first part of the paper, the possible resolution of image is investigated in the inversion of far-field data using the diffraction tomographic (DT) algorithm, where two cases are considered when the object...

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Bibliographic Details
Published in:IEEE transactions on antennas and propagation 2004-06, Vol.52 (6), p.1398-1411
Main Authors: Tie Jun Cui, Weng Cho Chew, Xiao Xing Yin, Hong, Wei
Format: Article
Language:English
Subjects:
Algorithms
Approximation algorithms
Distortion measurement
Electromagnetic diffraction
Electromagnetic scattering
Half spaces
Image resolution
Imaging
Inverse problems
Inverse scattering
Inversions
Iterative algorithms
Mathematical models
Spatial resolution
Studies
Tomography
Transmitters
Wavelengths
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Summary:It has been observed that super resolution is possible in the electromagnetic imaging. In the first part of the paper, the possible resolution of image is investigated in the inversion of far-field data using the diffraction tomographic (DT) algorithm, where two cases are considered when the object is in a homogeneous space and in an air-earth half space. The study shows that the resolution of image for inversion of far-field data has been limited theoretically to 0.3536-0.5 wavelength using the DT algorithm in homogeneous-space problems, and it is even worse in half-space problems. If the transmitters and receivers are located in the near-field regime, however, the image resolution is less than 0.25 wavelength, which is the super-resolution phenomenon. In the second part of the paper, the physical reason for the super-resolution phenomenon is investigated using different electromagnetic inverse scattering methods. The study has demonstrated that the information of evanescent waves in the measurement data and its involvement in inversion algorithms is the main reason for the super resolution. Four inversion algorithms are considered for half-space problems: the DT algorithm, the spatial-domain Born approximation (BA), the Born iterative method (BIM), and the distorted BIM (DBIM). The first two belong to linear inverse scattering, while the last two belong to nonlinear inverse scattering. Further analysis shows that DBIM provides a better super resolution than BIM, and BIM provides a better super resolution than BA. Numerical simulations validate the above conclusions.
ISSN:0018-926X
1558-2221
DOI:10.1109/TAP.2004.829847