Thermal-wave radar: A novel subsurface imaging modality with extended depth-resolution dynamic range

Tabatabaei, Nima; Mandelis, Andreas

doi:10.1063/1.3095560

Cited by 126 publications

(78 citation statements)

References 14 publications

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“…Moreover, based on this preliminary study, the application of quantitative infrared thermography for depth prediction in different materials and/or for the characterisation of different defects would provide a clearer view in the assessment of these depth prediction methods. In this direction, a comparative study incorporating different methodologies for depth prediction, such as the Logarithmic Peak Second-Derivative Time method [41], techniques based on the development of numerical modelling [42], or the recently developed Pulse Compression Thermography [43][44][45], which has shown to provide results with enhanced SNR, can define more representatively the strengths and weaknesses of each quantitative technique. −11.5 …”

Section: Discussionmentioning

confidence: 99%

Depth Retrieval Procedures in Pulsed Thermography: Remarks in Time and Frequency Domain Analyses

Theodorakeas

Koui

2018

Applied Sciences

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Featured Application: The present study intends to show the potentiality of pulsed thermographic imaging to quantitatively characterise hidden defects in Carbon Fibre Reinforced Polymers. By comparing the performance of different depth retrieval procedures, it was possible to evaluate the produced depth estimation accuracy and to define the impact of different experimental and analysis parameters in quantitative analysis. Abstract:In the present study, a Carbon Fibre Reinforced Polymer (CFRP) sample of trapezoid shape, consisting of internal artificial delaminations of various sizes and depth locations, is investigated by means of optical pulsed thermography for the retrieval of quantitative depth information. The main objectives of this work are to evaluate the produced depth estimation accuracy from two contrast-based depth inversion procedures as well as to correlate the acquired results with characteristics such as the location and size of the detected features and with analysis parameters such as the selection of the sound area. Quantitative analysis is performed in both the temporal and frequency domains, utilising, respectively, the informative parameters of thermal contrast peak slope time and blind frequency. The two depth retrieval procedures are applied for the depth estimation of features ranging in size from 3 mm to 15 mm and in depth from 0.2 mm to 1 mm. The results of the present study showed that the two different analyses provided efficient depth estimations, with frequency domain analysis presenting a greater accuracy. Nevertheless, predicting errors were observed in both cases and the factors responsible for these errors are defined and discussed.

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Section: Discussionmentioning

confidence: 99%

Depth Retrieval Procedures in Pulsed Thermography: Remarks in Time and Frequency Domain Analyses

Theodorakeas

Koui

2018

Applied Sciences

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“…However, increase in thermal diffusion length also increases the thermal wavelength and thus depreciates depth resolution. Recently, incorporation of matched-filtering in thermography has been proposed [21][22][23][24][25] for overcoming the classic compromise of conventional active thermography in order to maintain depth resolution while inspecting deep in samples. The sections below review the fundamentals of matched-filter thermography based on the works of Tabatabaei and Mandelis [21][22][23]26].…”

Section: Shortcoming Of Conventional Active 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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“…The block with blind holes sample design in normally used in the field of photothermal science to gauge the performance of the systems by demonstrating the characteristic depth profilometry nature of thermal waves. 14,15 That is, in accordance with the concept of thermal diffusion length, µ = α/πf m ; where α is medium thermal diffusivity, one can control the effective inspection depth by choosing the appropriate laser intensity modulation frequency (f m ). Consequently, conducting lock-in thermography at low modulation frequencies enables one to see deeper into the sample, albeit at the cost of inferior depth resolution, while experiments carried out at high modulation frequencies selectively reveal information from close-to-surface defects.…”

confidence: 99%

“…The lock-in amplitude and phase images of Figure 3 demonstrate the alignment of the results obtained from the developed inexpensive system with those previously obtained with expensive research-grade infrared cameras. 14 In recent years, lock-in thermography has proven to be effective for early detection of dental caries. [7][8][9]12 However, despite promising results, lock-in thermography has not yet been translated to Dentistry as a commercial product mostly due to the high cost of the system (costing about USD $120k with cryogenically cooled infrared cameras).…”

confidence: 99%