Phase Coherence Imaging: Principles, applications and current developments

Camacho, J.; Fritsch, C.; Fernandez-Cruza, Jorge; Parrilla, M.

doi:10.1121/2.0001201

Cited by 17 publications

(11 citation statements)

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“…Phase coherence imaging (PCI) [12,13] uses phase in order to determine a weighing factor for each signal arriving from each pixel in an image. In contrast, in TFM, the amplitude of the signals are added up irrespective of whether they arrive in phase or out of phase.…”

Section: Phase Coherence Imagingmentioning

confidence: 99%

Surface Acoustic Wave Suppression for Near-Surface Defect Imaging Using Laser Induced Phased Arrays

Davis

Fuwaires

Kamintzis

et al. 2022

2022 49th Annual Review of Progress in Quantitative Nondestructive Evaluation

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Laser induced phased arrays (LIPAs) offer fast and efficient remote ultrasonic imaging for processes operating in extreme environments and restricted access such as additive manufacturing and welding. In this work, LIPAs are synthesized in the non-destructive thermoelastic regime using an 8 ns pulsed 1064 nm generation laser and a 532 nm continuous wave detection laser. The acquired Full Matrix data is post-processed using the Total Focusing Method (TFM) to image near-surface side-drilled holes inside an Aluminium sample. The images generated, however, contain contribution from the surface acoustic wave (SAW). In laser ultrasonics, SAW is the strongest wave mode generated, and consequently, a region of the image generated is saturated by the SAW arrival (SAW cross-talk). The SAW cross-talk region extends into the sample starting at the scan surface and hence masks any features/defects within this region. This study explores and compares various signal processing techniques such as frequency-wavenumber filtering, phase coherence imaging and amplitude thresholding of ultrasonic signals in order to suppress/remove the SAW cross-talk from the ultrasonic data captured using LIPA for successful imaging of near-surface defects. The mode suppression is achieved by targeting the characteristics of the SAW: its velocity, amplitude and phase. The different methods of wave suppression are compared, and relative merits of each technique are discussed.

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Section: Phase Coherence Imagingmentioning

confidence: 99%

Surface Acoustic Wave Suppression for Near-Surface Defect Imaging Using Laser Induced Phased Arrays

Davis

Fuwaires

Kamintzis

et al. 2022

2022 49th Annual Review of Progress in Quantitative Nondestructive Evaluation

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Section: Imaging Algorithmsmentioning

confidence: 99%

“…During post-processing a Vector Coherence Factor (VCF) was introduced to the imaging algorithm in order to improve the image quality [13]. VCF is a variation of Phase Coherence Imaging (PCI) [13] and measures the coherence of phase throughout the A scan signals for any given pixel/voxel. In this way, the effects of grating lobes and random noise can be significantly reduced, as their contribution to any pixel will be incoherent, leading to low phase-coherence [14].…”

Section: Imaging Algorithmsmentioning

confidence: 99%

Remote, Volumetric Ultrasonic Imaging of Defects Using Two-Dimensional Laser Induced Phased Arrays

Lukács

Davis

Stratoudaki

et al. 2021

2021 48th Annual Review of Progress in Quantitative Nondestructive Evaluation

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Manufacturing processes, such as welding and additive manufacturing, take place at high temperatures and extreme environments that offer significant challenges to conventional non-destructive testing methods. Laser Induced Phased Arrays (LIPAs) have evolved as a promising testing method for the aforesaid applications due to its remote and couplant free operation. Contrary to transducer-based phased arrays, LIPAs are synthesized in post-processing by scanning the generation and detection lasers. The data from one-dimensional (1D) phased arrays are used to produce two-dimensional (2D), cross-sectional images, whereas the data from two-dimensional phased arrays generate three-dimensional (3D) images, thus providing more information on defect characterization. In this work, two-dimensional (2D) LIPAs are synthesized in the non-destructive thermoelastic regime using lasers for ultrasonic generation and detection, in order to image defects at different depths inside an aluminum sample. The acquired data is processed using the Total Focusing Method (TFM) algorithm to obtain volumetric images representing the interior of the sample. A 3D finite element (FE) model is also developed to support the experiments.

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“…The sign coherence factor (SCF) or the phase coherence factor (PCF) are extensions that take the phase into account in addition to the amplitude [41,42]. However, the use of these extensions requires that the phase is also the same for signal propagation paths of different lengths.…”

Section: Introductionmentioning

confidence: 99%

On Dispersion Compensation for GAW-Based Structural Health Monitoring

Backer

Fairuschin

Drese

2023

Sensors

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Guided acoustic waves (GAW) have proven to be a useful tool for structural health monitoring (SHM). However, the dispersive nature of commonly used Lamb waves compromises the spatial resolution making it difficult to detect small or weakly reflective defects. Here we demonstrate an approach that can compensate for the dispersive effects, allowing advanced algorithms to be used with significantly higher signal-to-noise ratio and spatial resolution. In this paper, the sign coherence factor (SCF) extension of the total focusing method (TFM) algorithm is used. The effectiveness is examined by numerical simulation and experimentally demonstrated by detecting weakly reflective layers with a highly dispersive A0 mode on an aluminum plate, which are not detectable without compensating for the dispersion effects.

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Phase Coherence Imaging: Principles, applications and current developments

Cited by 17 publications

References 0 publications

Surface Acoustic Wave Suppression for Near-Surface Defect Imaging Using Laser Induced Phased Arrays

Surface Acoustic Wave Suppression for Near-Surface Defect Imaging Using Laser Induced Phased Arrays

Remote, Volumetric Ultrasonic Imaging of Defects Using Two-Dimensional Laser Induced Phased Arrays

On Dispersion Compensation for GAW-Based Structural Health Monitoring

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