Nonlinear Phased Array Imaging

Anthony Croxford, Jingwei Cheng, Jack Potter

Research output: Chapter in Book/Report/Conference proceedingConference Contribution (Conference Proceeding)

4 Citations (Scopus)
348 Downloads (Pure)

Abstract

A technique is presented for imaging acoustic nonlinearity within a specimen using ultrasonic phased arrays. Acoustic nonlinearity is measured by evaluating the difference in energy of the transmission bandwidth within the diffuse field produced through different focusing modes. The two different modes being classical beam forming, where delays are applied to different element of a phased array to physically focus the energy at a single location (parallel firing) and focusing in post processing, whereby one element at a time is fired and a focused image produced in post processing (sequential firing). Although these two approaches are linearly equivalent the difference in physical displacement within the specimen leads to differences in nonlinear effects. These differences are localized to the areas where the amplitude is different, essentially confining the differences to the focal point. Direct measurement at the focal point are however difficult to make.

In order to measure this the diffuse field is used. It is a statistical property of the diffuse field that it represents the total energy in the system. If the energy in the diffuse field for both the sequential and parallel firing case is measured then the difference between these, within the input signal bandwidth, is largely due to differences at the focal spot. This difference therefore gives a localized measurement of where energy is moving out of the transmission bandwidth due to nonlinear effects.

This technique is used to image fatigue cracks and other damage types undetectable with conventional linear ultrasonic measurements.
Original languageEnglish
Title of host publicationHealth Monitoring of Structural and Biological Systems 2016
EditorsTribikram Kundu
Number of pages9
DOIs
Publication statusPublished - 23 May 2016

Publication series

NameProceedings of SPIE
PublisherSociety of Photo-optical Instrumentation Engineers
Volume9805
ISSN (Print)0277-786X
ISSN (Electronic)1996-756X

Keywords

  • Phased arrays
  • nonlinearity
  • diffuse field
  • fatigue cracks

Fingerprint Dive into the research topics of 'Nonlinear Phased Array Imaging'. Together they form a unique fingerprint.

Cite this