1997 Fiscal Year Final Research Report Summary
DEVELOPMENT OF AN EFFICIENT DIFFRACTION TOMOGRAPHY TECHNIQUE WITH FAST-CONVERGENCE AND HIGH-RESOLUTION PROPERTIES APPLIED TO IMAGING OF UNDERGROUND OBJECTS
| Project/Area Number |
08650503
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
計測・制御工学
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| Research Institution | OITA UNIVERSITY |
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Principal Investigator |
TANAKA Mitsuru OITA UNIVERSITY・FACULTY OF ENGINEERING PROFESSOR, 工学部, 教授 (30091341)
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| Co-Investigator(Kenkyū-buntansha) |
KUDOU Takato OITA UNIVERSITY・FACULTY OF ENGINEERING ASSOCIATE PROFESSOR, 工学部, 助教授 (60225159)
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| Project Period (FY) |
1996 – 1997
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| Keywords | DIFFRACTION TOMOGRAPHY / UNDERGROUND OBJECT / THREE-DIMENSIONAL INVERSE SCATTERING / WAVELET EXPANSION / FINITE-DIFFERENCE TIME-DOMAIN METHOD / REVISED MARQUARDT METHOD / REVISED QUASI-NEWTON METHOD / ITERATIVE RECONSTRUCTION ALGORITHM |
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| Research Abstract |
1.The problem of imaging a homogeneous rectangular object in cross-well geometry is considered using the revised Marquardt method. Numerical results prove that the iterative scheme provides high-quality reconstructions with fast cnvergence property regardless of the polarization of the received electric field. Furthermore we investigate the inverse scattering of an inhomogeneous cubic object, which is located in free space. It is seen from the numerical results that the object's permittivity can be successfully reconstructed even in the presence of measurement error in the scattered field data.
2.In the electromagnetic scattering by a circular cylinder, we expand the permittivity profile of the object in a wavelet series to obtain the scattered field. It is shown that the memory storage and the computation time can be cosiderably reduced in comparison with the conventional moment method. Next, we deal with the scattering of a pulsed wave by a two-layred cylinder using the FDTD method. Numerical results confirm the we can esimate the inner structure and the medium parameter of the object from the scattering response.
3.We study the reconstructinon of the permittivity of two-and four-layred media using the FDTD method. An iterative algorithm is derived employing the revised quasi-Newton method and wavelet expansion. It is concluded from the numerical results that we can obtain the fast-convergence and high-resolution image of the permittivity. This algorithm is also applied to imaging of a dielectric circular cylinder. Numerical examples demonstrate that we can successfully estimate the position and the permittivity of the object.
It is neccessary to clarify the relationship between the object's properties and the waveform of the scattered field. Furthermore image reconstruction using real data is very important. These are the topics for future work.
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