Truncated-correlation photothermal coherence tomography for deep subsurface analysis

Kaiplavil, Sreekumar; Mandelis, Andreas

doi:10.1038/nphoton.2014.111

Cited by 84 publications

(34 citation statements)

References 22 publications

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“…A significant breakthrough was achieved in the field by Tabatabaei and Mandelis' introduction of thermal coherence tomography (TCT) [22,26], which used the binary phase coding pulse compression technique (i.e., a narrow-band phase encoding technique) to optimize the thermal-waves' matched-filter responses in order to resolve overlaying absorbers in a diffusive field. Application of matched-filtering in a thermography system using pulsed excitation was first demonstrated by Kaiplavil and Mandelis [40] in 2011 and was later optimized to yield a highly depth-resolved thermal-wave tomographic imaging modality, termed truncated-correlation photothermal coherence tomography (TC-PCT) [41][42][43][44]. Some other fundamental advancements in the field of TWR include: incorporation of Barker [45] and Golay [46,47] code pulse compression techniques and performance optimization using spectral shaping [48].…”

Section: Matched Filtering In Thermographymentioning

confidence: 99%

Matched-Filter Thermography

Tabatabaei

2018

Applied Sciences

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Conventional infrared thermography techniques, including pulsed and lock-in thermography, have shown great potential for non-destructive evaluation of broad spectrum of materials, spanning from metals to polymers to biological tissues. However, performance of these techniques is often limited due to the diffuse nature of thermal wave fields, resulting in an inherent compromise between inspection depth and depth resolution. Recently, matched-filter thermography has been introduced as a means for overcoming this classic limitation to enable depth-resolved subsurface thermal imaging and improving axial/depth resolution. This paper reviews the basic principles and experimental results of matched-filter thermography: first, mathematical and signal processing concepts related to matched-fileting and pulse compression are discussed. Next, theoretical modeling of thermal-wave responses to matched-filter thermography using two categories of pulse compression techniques (linear frequency modulation and binary phase coding) are reviewed. Key experimental results from literature demonstrating the maintenance of axial resolution while inspecting deep into opaque and turbid media are also presented and discussed. Finally, the concept of thermal coherence tomography for deconvolution of thermal responses of axially superposed sources and creation of depth-selective images in a diffusion-wave field is reviewed.

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Section: Matched Filtering In Thermographymentioning

confidence: 99%

Matched-Filter Thermography

Tabatabaei

2018

Applied Sciences

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“…Due to a laser's high temporal dynamic the VCSEL device can bridge the gap between halogen lock-in-thermography and flash excitation through temporal pulse forming techniques. These have already been investigated theoretically and experimentally [1,2], but the limited capability of conventional heat sources made this endeavour difficult.…”

Section: Fig 1 Vcsel Array At Iktmentioning

confidence: 99%

“…While there are several modern approaches in signal form and evaluation [1,2], the two main regimes commonly known for achieving instationary heat diffusion necessary for active thermography use energy sources that can be controlled in either pulse mode (e.g. flash thermography) [3] or periodically.…”

Section: Introductionmentioning

confidence: 99%

Optical excitation thermography with VCSEL-array source

Rahammer¹,

Vetter²,

Kreutzbruck³

2016

Proceedings of the 2016 International Conference on Quantitative InfraRed Thermography

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A novel VCSEL array combines the high temporal flexibility of a laser source with the full field radiation characteristics of an array and yields a new optical excitation source for active thermography that can merge the two regimes of flash and lock-in thermography. Among others, we investigate the possibility of multiplex photothermics for two-dimensional material characterization, e. g. thickness mapping. Several first test results will be presented that demonstrate possibilities and capabilities of this new optical excitation source and compare it to conventional sources.

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“…An alternative excitation method called truncated-correlation photothermal coherence tomography (TC-PCT), which also combines the advantages of time-and frequency domain methods, was inspired by the radar technology and uses a chirped pulse approach in which a broadband thermal relaxation chirp is cross-correlated with a sequence of delay-swept and pulsewidth-truncated references. 13 Heat diffusion and the propagation of an undamped acoustic wave are mathematically modeled by the diffusion equation and the wave equation, respectively. Both equations are second order linear partial differential equations in space and time but describe a quite different physical phenomena.…”

Section: Introductionmentioning

confidence: 99%

Three-dimensional thermographic imaging using a virtual wave concept

Burgholzer

Thor

Gruber

et al. 2017

Journal of Applied Physics

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In this work, it is shown that image reconstruction methods from ultrasonic imaging can be employed for thermographic signals. Before using these imaging methods, a virtual signal is calculated by applying a local transformation to the temperature evolution measured on a sample surface. The introduced transformation describes all the irreversibility of the heat diffusion process and can be used for every sample shape. To date, one-dimensional methods have been primarily used in thermographic imaging. The proposed two-stage algorithm enables reconstruction in two and three dimensions. The feasibility of this approach is demonstrated through simulations and experiments. For the latter, small steel beads embedded in an epoxy resin are imaged. The resolution limit is found to be proportional to the depth of the structures and to be inversely proportional to the logarithm of the signal-to-noise ratio. Limited-view artefacts can arise if the measurement is performed on a single planar detection surface. These artifacts can be reduced by measuring the thermographic signals from multiple planes, which is demonstrated by numerical simulations and by experiments performed on an epoxy cube.Comment: 22 pages, 8 figures, 1 appendix, acceapted by JA

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Truncated-correlation photothermal coherence tomography for deep subsurface analysis

Cited by 84 publications

References 22 publications

Matched-Filter Thermography

Matched-Filter Thermography

Optical excitation thermography with VCSEL-array source

Three-dimensional thermographic imaging using a virtual wave concept

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