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Entropy 2018, 20(8), 621; https://doi.org/10.3390/e20080621

The Maximum Entropy Method in Ultrasonic Non-Destructive Testing—Increasing the Resolution, Image Noise Reduction and Echo Acquisition Rate

SPC ECHOPLUS, 123458 Moscow, Russia
Received: 26 June 2018 / Revised: 27 July 2018 / Accepted: 17 August 2018 / Published: 20 August 2018
(This article belongs to the Special Issue Entropy: From Physics to Information Sciences and Geometry)
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Abstract

The use of linear methods, for example, the Combined Synthetic Aperture Focusing Technique (C–SAFT), does not allow one to obtain images with high resolution and low noise, especially structural noise in all cases. Non-linear methods should improve the quality of the reconstructed image. Several examples of the application of the maximum entropy (ME) method for ultrasonic echo processing in order to reconstruct the image of reflectors with Rayleigh super-resolution and a high signal-to-noise ratio are considered in the article. The use of the complex phase-shifted Barker code signal as a probe pulse and the compression of measured echoes by the ME method made it possible to increase the signal-to-noise ratio by more than 20 dB for the image of a flat-bottom hole with a diameter of 1 mm in a model experiment. A modification of the ME method for restoring the reflector image by the time-of-flight diffraction (TOFD) method is considered, taking into account the change of the echo signal shape, depending on the depth of the reflector. Using the ME method, 2.5D-images of models of dangling cracks in a pipeline with a diameter of 800 mm were obtained, which make it possible to determine their dimensions. In the object with structural noise, using the ME method, it was possible to increase the signal-to-noise ratio of the reflector image by more than 12 dB. To accelerate the acquisition of echoes in the dual scan mode, it is proposed to use code division multiple access (CDMA) technology based on simultaneous emission by all elements of the array of pseudo-orthogonal signals. The model experiment showed the effectiveness of applying the ME method. View Full-Text
Keywords: antenna array; full matrix capture (FMC); triple scanning; structural noise; maximum entropy (ME); C–SAFT; total focusing method (TFM); time-of-flight diffraction (TOFD); code division multiple access (CDMA) antenna array; full matrix capture (FMC); triple scanning; structural noise; maximum entropy (ME); C–SAFT; total focusing method (TFM); time-of-flight diffraction (TOFD); code division multiple access (CDMA)
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).
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Bazulin, E.G. The Maximum Entropy Method in Ultrasonic Non-Destructive Testing—Increasing the Resolution, Image Noise Reduction and Echo Acquisition Rate. Entropy 2018, 20, 621.

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