Nondestructive Evaluation of Microwave-Penetrable Pipes by Synthetic Aperture Imaging Enhanced by Full-Wave Field Propagation Model

Abstract

A qualitative approach for microwave imaging multi-layered cylindrical structures (e.g., dielectric pipes) is proposed in this paper. This approach relies on a modified circular synthetic aperture imaging technique that exploits closed-form Green's function to account for the different propagation delays, internal reflections and refractions. The image can then be computed by employing a matched-filter expressed in terms of efficient Fourier Transforms. Consequently, a high-resolution and contactless approach for the inspection of this kind of structures is achieved. Moreover, the computational resources to render the images are negligible. Practical aspects of the technique such as sampling criteria, resolution and limitations of the technique are discussed. The efficacy of the method is illustrated via several examples including imaging of objects and anomalies inside different types of dielectric pipes.

Time-Reversal SAR Imaging for Nondestructive Testing of Circular and Cylindrical Multilayered Dielectric Structures

“…As mentioned earlier, unlike the Green's function approach (i.e., [28]) the utility of this approach is not limited to symmetrical layered cylindrical cases and can be applied to asymmetrical cases as well. To illustrate the efficacy of the approach for this purpose two asymmetrical layered cylindrical cases were considered, as show in Figs.…”

“…For 2-D C-SAR imaging, let:  and the superscript "*" denotes conjugate. Therefore, for a generally lossy and multi-layered 2D circular structure, we can use (28) and (29) to accurately reconstruct the SAR image. For 3D multi-layered cylindrical structure, due to the complicated tensor representation of polarization vectors, we can use the following method to simplify the model and to obtain a closely representative image of the structure.…”

“…perfect cylinders). This approach has been successfully implemented for such cylindrical geometries [28]. After the Green's function has been computed, the computational cost of the approach (i.e., Wiener deconvolutions) is determined by ( log ( ), where N and M are the total number of points along the height and azimuth directions, respectively, and P is the total number of concentric rings (i.e., radial) considered to build the image.…”

A Synthetic Aperture Radar (SAR)-Based Technique for Microwave Imaging and Material Characterization

“…In the area of nondestructive testing for detection of targets/objects embedded in a surrounding opaque medium (e.g., detection of tumors in breast tissue [6]), the aforementioned techniques require a priori information about the problem, which varies depending on the inverse scattering or imaging technique to be applied. For example, those based on multilayered Green's Function formulation need an initial guess of the constitutive parameters of the surrounding medium [16,17]. Inverse scattering techniques based on cost function minimization [3,14] require a set of first guess solutions and the definition of the search space boundaries.…”

Imaging of Internal Defects of Polymer-Modified Wood Using Total Focusing Method

“…The nondestructive testing technology can find the defects of wood by comparing the differences of physical or chemical characteristics [7]. Methods such as the electromagnetic wave detection, laser detection, infrared detection, ultrasonic detection, nuclear magnetic resonance, and X-ray detection have been widely used in the metal defect detection, ground penetrating radar, medical imaging, and other fields [8][9][10].…”