Application of Nonuniform Fourier Transform to Solving Ultrasonic Tomography Problems with Antenna Arrays
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STIC METHODS
Application of Nonuniform Fourier Transform to Solving Ultrasonic Tomography Problems with Antenna Arrays D. O. Dolmatova, *, N. I. Ermoshina, **, D. A. Konevaa, ***, and D. A. Sedneva, **** aNational
Research Tomsk Polytechnic University, Tomsk, 634040 Russia *e-mail: [email protected] **e-mail: [email protected] ***e-mail: [email protected] ****e-mail: [email protected]
Received April 28, 2020; revised June 22, 2020; accepted June 23, 2020
Abstract—In ultrasonic tomography that employs the technique of digital focusing with an antenna (DFA), the problem of increasing the inspection performance is inextricably linked with the problem of increasing the speed of producing synthesized images. This problem can be effectively solved by concurrently using several approaches aimed at increasing the image production speed. In the framework of this paper, we consider the algorithm of nonuniform fast Fourier transform (NUFFT). The NUFFT can be used in the existing computationally efficient spatiotemporal processing algorithms with calculations in the frequency domain and is capable of correctly reconstructing synthesized images with sparse and non-uniform antenna arrays (AAs). The experimental data obtained indicate the ability of the NUFFT-based algorithm to restore synthesized images with high resolution. Keywords: ultrasonic tomography, digital focusing with antenna, antenna arrays, nonuniform fast Fourier transform, algorithms of spatiotemporal processing with calculations in frequency domain DOI: 10.1134/S1061830920080021
INTRODUCTION An urgent issue in the development of methods and equipment for ultrasonic nondestructive testing is transition from solving the problem of flaw detection to solving the problem of defect characterization. Industrial ultrasonic tomography systems are of great interest in this regard, as they render inspection results in the form of high-resolution images of the internal structure of objects. The DFA technique is one of the approaches that have found wide application in ultrasonic tomography systems. It assumes the use of an AA for the ultrasonic transducer and the acquisition of images of the internal structure of test objects through the use of spatiotemporal processing algorithms based on the synthetic aperture focusing technique [1, 2]. In the context of the practical use of ultrasonic tomography systems, the problem of increasing the productivity of ultrasonic testing is inextricably linked with the problem of increasing the speed of producing images with no loss in their quality. All existing algorithmic solutions to this problem can be divided into two fundamental approaches. The first approach is to use an optimized dataset that ensures the high quality of resulting synthesized images in spatiotemporal processing. The ultrasonic dataset can be optimized using sparse or non-uniform AA transducers. In sparse AA not all elements of such transducer are involved in the emission of ultrasonic waves and receiving the echo signals. The selected configuration of the sparse AA sho
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