Free-Space Microwave Tomography for NDT Applications to Identify Different Dielectric Materials

Advancement of industrial tomographic instruments based on different imaging modalities (e.g., X-ray, gamma ray, magnetic resonance, ultrasound, microwave, etc.) has been an active area of research over the past three decades. Most of these instruments are costly, bulky and have operational limitations; therefore, an alternative is sought for such industrial applications. Microwave tomography (MWT) system has recently emerged as a more appropriate technique to non-destructively evaluate industrial objects. In the present work, a two-dimensional free-space microwave tomography system has been designed and developed to explore the possibility of imaging the distribution of dielectric properties in a reconstruction space. A multi-view approach is presented which makes use of a single transmission and receiving antenna to collect the line integral of the object through the image space. These line integrals have been processed with the multiplicative algebraic reconstruction technique (MART) to smear the projection data back to image space. The proposed imaging system has been first validated with numerical phantoms and then with the real specimens. The preliminary results are encouraging and illustrate the suitability of the prototype for industrial applications.