Andrea Salvade

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.

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 Microwave Tomographic System for Wood Characterization in the Forest Products Industry

Abstract Nondestructive testing and evaluation techniques able to extract information about the internal structure of the samples under test are very important in the wood industry. Microwave imaging systems have been considered for a long time promising apparatuses for this task. In this framework, approaches exploiting the full scattering phenomena for creating images of the distributions of the dielectric properties of the targets have been developed in the last few years. In this paper, a prototype of microwave tomographic system is presented and several experimental validation confirming its suitability for the use in the wood and forest product industry are reported.

Microwave imaging of foreign bodies inside wood trunks

The detection of foreign bodies inside wood trunks is a key task in the wood processing industry. Bullets, screws, or other debris can severely damage carpentry machinery, and, consequently, must be removed prior to processing. In this paper, the feasibility of a new prototype of microwave tomograph for the detection of metallic inclusions inside wood trunks is analyzed. Numerical simulations show that the proposed system configuration is able to acquire data that can be successfully used, in conjunction with a proper inversion procedure, to obtain the distribution of the conductivity of the sample under test, and consequently, to identify the presence of metallic inclusions.

A Microwave Axial Tomograph: Experimental Set Up and Reconstruction Procedure

New steps toward the development of a microwave axial tomograph for inspecting dielectric materials are reported in this paper. The design of the proposed imaging system is described and the results of preliminary forward scattering simulations are reported in order to define the requirements for an efficient treatment of the measured scattered data

Preliminary test of a prototype of microwave axial tomograph for medical applications

An existing prototype of microwave imaging tomograph, previously designed by the present Authors for non destructive testing (NDT) applications, has been adapted in order to deal with biomedical targets. The developed system allows collecting multi-view multi-frequency data. An efficient inversion procedure is used to retrieve the distributions of the dielectric properties from the measured field samples. Some numerical simulations aimed at validating the proposed system and preliminary measurement results obtained by using a breast phantom are presented in this paper.

Reconstruction of Metallic Inclusions Inside Dielectric Targets by Means of a Microwave Tomographic System

Experimental results concerning the inspection at microwave frequencies of wood material with metallic inclusions are reported. They have been obtained by inverting samples of the scattered electromagnetic field collected by a prototype of an imaging system. The system is able to acquire multi-illumination multiview data in a tomographic arrangement. The retrieved maps of the dielectric permittivity and electric conductivity of the cross sections of unknown targets are obtained by applying the distorted-wave Born approximation to the electric field integral equation governing the scattering phenomenon.

A numerical evaluation of an optimal setup for a microwave axial tomograph aimed at the inspection of wood

This paper presents the results of model based numerical simulations (Ansoft HFSScopy) used to analyze the scattering of the electromagnetic field on sample objects, in order to determine an optimal setup for a new microwave tomograph aimed at the inspection of wood trunks. Such a tomograph is targeted to obtain images of the cross section of dielectric cylinders. In particular, it was used to inspect wood slabs and trunks in order to search for defects and voids. For best results of the inversion (tomographic image reconstruction) algorithms, it is important that the measured data (samples of the scattered electric field) are collected under an optimal setup configuration of the sample, the illuminating and the pick-up antennas.

Microwave detection of dielectric structures by using a tomographic approach

In this paper, an experimental set-up for tomographic imaging based on interrogating microwaves is presented. In particular, a previously proposed prototype aimed at identifying defects and voids in wood slabs is further developed and validated. Moreover, together with new improvements of the acquisition set-up, an efficient numerical approach, aimed at retrieving the dielectric characteristics of the sample under test from the measured data (samples of the scattered electric field,) is presented. The developed experimental apparatus and the inversion technique are validated by means of numerical and experimental simulations.