Resolution enhancement of nondestructive testing from B‐scans

Abstract

This article presents an approach to extend our previous work of the minimum‐weighted norm method in computerized tomography. In particular concentrating on applications of ultrasonic nondestructive testing, the resolution enhancement in the image reconstruction from B‐scans is achieved. To combat the degradation problem due to physical focus of finite‐sized ultrasonic transducer and incompleteness of B‐scan data, a profile‐oriented prior knowledge about the object being detected is incorporated in the image reconstruction, in the form of weighted summation of specific basis functions. Each basis function is characterized by an image of coherent illumination pattern associated with a specific measuring time and a specific measuring position. From the demonstrations with both simulated and experimental data values, this technique proves a great potential in improving the image quality. © 2012 Wiley Periodicals, Inc. Int J Imaging Syst Technol, 22, 185–193, 2012

A Sparse Reconstruction Algorithm for Ultrasonic Images in Nondestructive Testing

“…This regularization method is used by Shieh et al to improve the resolution of B-scan images [ 4 ]. In addition to the Tikhonov method, there are other regularization techniques, formulated from different approaches.…”

“…Although the B-scan reconstruction algorithm is quite simple and fast, it suffers from low lateral resolution. Additionally, transducer diameter and depth of the object may negatively affect image quality [ 4 , 5 ] due to beam spreading and diffraction [ 6 ]. In the early 1970s, the synthetic aperture focusing technique (SAFT) [ 7 – 9 ] was developed inspired in concepts of synthetic aperture (SA) used in airborne radar mapping systems [ 10 ].…”

Ultrasonic Model-Based Iterative Reconstruction with Spatially Variant Regularization for One-Sided Non-Destructive Evaluation

“…In [14], [16]- [18], the authors used a simple regularization terms, such as l 1 or l 2 . This regularization is suitable for imaging point scatters or sparse regions.…”