Giovanni Bozza

An Inexact Newton Method for Microwave Reconstruction of Strong Scatterers

An approach to solve the inverse scattering problem for imaging applications is presented. The proposed algorithm is based on an inexact Newton method applied to the Lippmann¿Schwinger integral equation. Inhomogeneous dielectric scatterers with high contrast in a tomographic arrangement are considered. The capabilities of the approach are assessed with reference to several different unknown objects. In particular, both noisy synthetic data and experimental data have been used. Furthermore, a comparison with a model based on the second order Born approximation is also reported.

A Two-Step Iterative Inexact-Newton Method for Electromagnetic Imaging of Dielectric Structures from Real Data

A new inverse scattering method is assessed against some of the real input data measured by the Institut Fresnel, Marseille, France. The method is based on the application of an Inexact-Newton method to the Lippmann-Schwinger integral equation of the inverse scattering problem within the second-order Born approximation. The regularization properties of the approach are evaluated by considering the reconstruction of multiple dielectric cylinders.

Application of an Inexact-Newton Method Within the Second-Order Born Approximation to Buried Objects

The imaging of buried objects is a challenging topic in electromagnetic research. In this letter, a method previously proposed for imaging of scatterers in free-space is extended to the case of objects buried in a lossy half-space. The proposed approach is based on the solution of the underlying inverse-scattering problem within the second-order Born approximation by means of a two-step inexact-Newton algorithm. The capabilities and limitations of the method are evaluated by means of some numerical simulations. Furthermore, comparisons with the free-space approach are also reported

An Inexact Newton-Based Approach to Microwave Imaging Within the Contrast Source Formulation

In this paper an approach to microwave imaging based on an inexact-Newton method within the contrast source formulation of the inverse scattering problem is considered. In this framework, the iteratively linearized equations of the inverse problem are solved by means of the regularizing truncated Landweber algorithm. This approach allows an effective and robust tool to inspect dielectric objects, as it is shown by the reported numerical results. Moreover, thanks to the structure of the involved integral equations within the contrast source formulation, computer memory saving can be obtained with respect to the electric field integral equation framework. Finally, the proposed method is validated against experimental data, kindly provided by the Institute Fresnel, Marseille, France.

Application of the No-Sampling Linear Sampling Method to Breast Cancer Detection

In this paper, the no-sampling linear sampling method is applied to microwave imaging of cancerous tissues in realistic models of female breast obtained from magnetic resonance imaging (MRI). The adopted formulation is based on a modified version of the far-field equation, sensitive to anomalies with respect to the healthy breast. The healthy configuration is taken into account through the related Greens function, which is numerically computed. The adopted imaging technique is assessed against the inspection of tumors of several positions and sizes in noisy environments. Moreover, a numerical analysis of the robustness of the method is performed when the model parameters used for evaluating the Greens function are not exactly known.

A New Microwave Axial Tomograph for the Inspection of Dielectric Materials

In this paper, the development of a microwave axial tomograph for the inspection of dielectric materials is discussed. In particular, hardware and software solutions are pointed out. An experimental bistatic imaging setup is described. Moreover, the results of several forward-scattering simulations, which are aimed at defining suitable working conditions, are reported. Finally, to invert the collected field-scattered data, a deterministic inexact Newton method is applied. The approach is evaluated by using synthetic data, and the results of a preliminary experimental reconstruction are reported.

Impact of Background Noise on Dielectric Reconstructions Obtained by a Prototype of Microwave Axial Tomograph

This paper investigates the influence of noise on a microwave axial tomograph developed by some of the authors for the inspection of dielectric objects. In particular, the impact of the measurement environment is considered and the images obtained from data measured in a controlled and an uncontrolled environment are presented and compared. Moreover, the effects of interference signals are considered. Accordingly, several experimental results are reported and discussed in terms of proper error parameters.

A fully no-sampling formulation of the linear sampling method for three-dimensional inverse electromagnetic scattering problems

We describe a very fast and automatic formulation of the linear sampling method for three-dimensional electromagnetic inverse scattering problems. This formulation is an extension of a no-sampling implementation recently proposed for two-dimensional configurations. In this 3D framework, regularization occurs independently not only of the sampling point but even of the polarization of the fundamental solution used as a known term. Furthermore, a very effective automatic procedure for the selection of the optimal surface describing the scatterer is introduced.

Detection of defects in wood slabs by using a microwave imaging technique

In this paper, an experimental set up based on interrogating microwaves is used to obtain images of the cross section of dielectric cylinders. In particular, a microwave tomographic configuration is used to inspect wood slabs in order to search for defects and voids. The measured data (samples of the scattered electric field) are inverted by using an efficient reconstruction technique, which is able to handle the ill-posedness of the inverse scattering problem. The developed experimental apparatus is validated in this paper by means of several numerical simulations. Preliminary experimental results are also reported.

A linear sampling approach to crack detection in microwave imaging

In this contribution a new approach for inspecting crack and defects in known structures by using microwaves is presented. The novelty consists in using a new formulation of the linear sampling method called the no sampling linear sampling method to invert the scattered data, which results to be particularly fast and effective. Such a technique belongs to the category of qualitative methods and is able to retrieve position and shape of anomalies inside a known structure, but it does not provide any information on the point values of the dielectric parameters of the defects. In the paper the formulation of the problem and the new version of the linear sampling method are outlined and some numerical results are provided to assess the proposed approach.