Clutter noise reduction for phased array imaging using frequency-spatial polarity coherence

Rui Gongzhang, Anthony Gachagan, Bo Xiao

Research output: Chapter in Book/Report/Conference proceedingConference contribution book

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Abstract

A number of materials used in industry exhibit highly-scattering properties which can reduce the performance of conventional ultrasonic NDE approaches. Moving Bandwidth Polarity Thresholding (MBPT) is a robust frequency diversity based algorithm for scatter noise reduction in single A-scan waveforms, using sign coherence across a range of frequency bands to reduce grain noise and improve Signal to Noise Ratio. Importantly, for this approach to be extended to array applications, spatial variation of noise characteristics must also be considered. This paper presents a new spatial-frequency diversity based algorithm for array imaging, extended from MBPT. Each A-scan in the full matrix capture array dataset is partitioned into a serial of overlapped frequency bands and then undergoes polarity thresholding to generate sign-only coefficients indicating possible flaw locations within each selected band. These coefficients are synthesized to form a coefficient matrix using a delay and sum approach in each frequency band. Matrices produced across the frequency bands are then summed to generate a weighting matrix, which can be applied on any conventional image. A 5MHz linear array has been used to acquire data from both austenitic steel and high nickel alloy (HNA) samples to validate the proposed algorithm. Background noise is significantly suppressed for both samples after applying this approach. Importantly, three side drilled holes and the back wall of the HNA sample are clearly enhanced in the processed image, with a mean 133% Contrast to Noise Ratio improvement when compared to a conventional TFM image.
Original languageEnglish
Title of host publication41st Annual Review of Progress in Quantative Nondestructive Evaluation
EditorsDale E. Chimenti, Leonard J. Bond
Pages1648-1656
Number of pages9
Volume34
DOIs
Publication statusPublished - 31 Mar 2015
Event41st Annual Review of Progress in Quantitative Nondestructive Evaluation Conference - Boise Centre, Boise, United States
Duration: 20 Jul 201425 Jul 2014

Publication series

NameAIP Conference Series
PublisherAmerican Institue Physics
Volume1650
ISSN (Electronic)0094-243X

Conference

Conference41st Annual Review of Progress in Quantitative Nondestructive Evaluation Conference
Abbreviated titleQNDE
Country/TerritoryUnited States
CityBoise
Period20/07/1425/07/14

Keywords

  • Moving Bandwidth Polarity Thresholding
  • scatter noise reduction
  • signal-to-noise ratio
  • noise characteristics
  • spatial-frequency diversity based algorithm
  • array imaging
  • sign-only coefficients
  • high nickel alloy
  • ultrasonic non-destructive evaluation

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