scispace - formally typeset
Search or ask a question

Showing papers on "Thermography published in 2005"


Journal ArticleDOI
TL;DR: IR imaging offers a useful and non-invasive approach to the diagnosis and treatment of many disorders, in particular in the areas of rheumatology, dermatology, orthopaedics and circulatory abnormalities.
Abstract: Since the early days of thermography in the 1950s, image processing techniques, sensitivity of thermal sensors and spatial resolution have progressed greatly, holding out fresh promise for infrared (IR) imaging techniques. Applications in civil, industrial and healthcare fields are thus reaching a high level of technical performance. The relationship between body temperature and disease was documented since 400 bc. In many diseases there are variations in blood flow, and these in turn affect the skin temperature. IR imaging offers a useful and non-invasive approach to the diagnosis and treatment (as therapeutic aids) of many disorders, in particular in the areas of rheumatology, dermatology, orthopaedics and circulatory abnormalities. This paper reviews many usages (and hence the limitations) of thermography in biomedical fields.

253 citations



01 Jan 2005
TL;DR: In this article, a depth inversion technique using the phase obtained by PPT is proposed, which relies on the thermal diffusion length equation, i.e. μ=(α /π·f), in a similar manner as in Lock-In Thermography.
Abstract: Pulsed Phase Thermography (PPT) is a NonDestructive Testing and Evaluation (NDT&E) technique based on the Fourier Transform that can be thought as being the link between Pulsed Thermography, for which data acquisition is fast and simple; and Lock-In thermography, for which depth retrieval is straightforward. A new depth inversion technique using the phase obtained by PPT is proposed. The technique relies on the thermal diffusion length equation, i.e. μ=(α /π·f), in a similar manner as in Lock-In Thermography. The inversion problem reduces to the estimation of the blind frequency, i.e. the limiting frequency at which a defect at a particular depth presents enough phase contrast to be detected on the frequency spectra. However, an additional problem arises in PPT when trying to adequately establish the temporal parameters that will produce the desired frequency response. The decaying thermal profiles such as the ones serving as input in PPT, are non-periodic, non-band-limited functions for which, adequate sampling Δt, and truncation w(t), parameters should be selected during the signal discretization process. These parameters are both function of the depth of the defect and of the thermal properties of the specimen/defect system. A four-step methodology based on the Time-Frequency Duality of the discrete Fourier Transform is proposed to interactively determine Δt and w(t). Hence, provided that thermal data used to feed the PPT algorithm is correctly sampled and truncated, the inversion solution using the phase takes the form: z=C1μ, for which typical experimental C1 values are between 1.5 and 2. Although determination of fb is not possible when working with badly sampled data, phase profiles still present a distinctive behavior that can be used for depth retrieval purposes. An apparent blind frequency f’b, can be defined as the blind frequency at a given phase threshold φd, and be used in combination with the phase delay definition for a thermal wave: φ=z /μ, and the normalized diameter, Dn=D/z, to derive an alternative expression. Depth extraction in this case requires an additional step to recover the size of the defect.

189 citations


Proceedings ArticleDOI
01 Jan 2005
TL;DR: In this article, pressure sensitive paint, temperature sensitive paint (TSP), and infrared (IR) thermography are used to measure the film cooling effectiveness on a flat plate, and a single row of cylindrical holes, with a compound angle, are used.
Abstract: Several steady state measurement techniques are used to measure the film cooling effectiveness on a flat plate. Pressure sensitive paint (PSP), temperature sensitive paint (TSP), and infrared (IR) thermography are used to measure the film cooling effectiveness. To compare these measurement techniques, a single row of cylindrical holes, with a compound angle, are used. Seven holes (D = 4 mm) are equally spaced 12 mm apart, and the hole length-to-diameter ratio is 9.92. The axial angle (θ) of the holes is 30°, and the compound angle (β) is 45°. In addition to evaluating the various measurement techniques the effect of the coolant blowing ratio is considered; effectiveness measurements are taken for blowing ratios, M, of 0.4, 0.6, 1.2, and 1.8. The effect of mainstream turbulence intensity is considered with the addition of a turbulence grid to the low speed wind tunnel. Of the three steady state measurement techniques considered in this study, PSP demonstrates the most promise for the measurement of the film cooling effectiveness. Because PSP is a mass transfer technique, film effectiveness measurements can be readily obtained near the film cooling holes. Although the heat transfer techniques of TSP and IR thermography are more desirable than traditional thermocouples or liquid crystal thermography, the applicability of measurements near the holes is questionable due to conduction problems associated with steady state heat transfer techniques.Copyright © 2005 by ASME

99 citations


Journal ArticleDOI
TL;DR: In this article, the use of finite element (FE) analysis to simulate the thermographic process for complex non-axisymmetric geometries has been presented, and a suitably calibrated finite element simulation has been generated and validated.

87 citations


Journal ArticleDOI
TL;DR: In this article, the authors proposed to divide the thermogram image into small, localized neighborhoods using the assumption that these neighborhoods exhibit the non-defective behavior for the thermal contrast computation.

82 citations


Journal ArticleDOI
TL;DR: In this article, the authors present a method to quantify the reflected flux by using an infrared mirror, which allows large surface temperature measurements by infrared thermography under near-ambient conditions with improved accuracy.

81 citations


Journal ArticleDOI
TL;DR: In this article, a multi-methodological approach to non-destructive evaluation of architectural structures is presented, where three different techniques such as infrared thermography, ultrasonics and electric-type geophysical methods are analysed to acquire information for a synergic use of different methods, which may be useful for the estimation of the buildings degradation sources.

78 citations


Patent
28 Feb 2005
TL;DR: In this article, a real-time thermal imaging apparatus and method includes multiple digital infrared cameras mounted to an automated composite material layup device to record digital infrared images of the composite material surface.
Abstract: A real-time thermal imaging apparatus and method includes multiple digital infrared cameras mounted to an automated composite material layup device to record digital infrared images of the composite material surface on a real-time basis during a composite material layup process. The digital infrared cameras are triggered periodically to produce digital images of the composite material. The digital image data is sent to an image analyzer which detects edges of and anomalies in the composite material and generates alarm and other process control signals. The image analyzer also aggregates the digital images from the multiple cameras and the digital images recorded over a sequence in time to produce a continuous virtual digital image of the composite material surface. The digital image data and associated analysis results are saved and may be displayed on a real-time basis or at a later time.

74 citations


Journal ArticleDOI
TL;DR: In this paper, the applicability of pulse phase thermography (PPT) for the investigation of structures is studied systematically on concrete test specimens and on a plastered sandstone column.
Abstract: The applicability of pulse phase thermography (PPT) for the investigation of structures is studied systematically on concrete test specimens and on a plastered sandstone column. In the test specimens, voids and delaminations are implemented in different depths and with different sizes, modelling real voids, honeycombing and debonding. Delaminations of plaster in concrete and masonry and behind tiles on concrete are investigated. PPT is based on the frequency analysis of the cooling down process of actively heated surfaces. Therefore, it is contactless and thus completely non-destructive (if overheating of the surface is prevented), fast and allows the inspection of large surface areas. The interpretation of amplitude and phase images gives semi-quantitative information about the observed defects. The phase images provide a deeper probing up to 10–15 cm in relation to the interpretation of the thermograms and to the amplitude images. In addition, the influence of surface inhomogeneities and non-uniform heating is reduced.

71 citations


Journal ArticleDOI
TL;DR: This review gives an overview of focal plane array (FPA)-based infrared (IR) thermography as a powerful research method in the field of physiology and medicine and a new phenomenon, stable punctate hidrosis, is discovered and described.
Abstract: This review gives an overview of focal plane array (FPA)-based infrared (IR) thermography as a powerful research method in the field of physiology and medicine. Comparison of the gained results with the data previously obtained by other authors with other research tools is given. Outer thermoregulatory manifestations displayed by the human organism subjected to whole-body heating (sauna bath) and physical loads (exercise bicycling) are quantitatively analysed. Some details of human body emotional sweating (psycho-physiological effect) are reported. Particular attention is paid to studying active sweat glands as individual objects. All experimental data were obtained with the help of a high-sensitivity (0.03 degrees C) fast 128 x 128 InAs IR detector-based thermal imaging system operating in the short-wave spectral region (2.5 to 3 microm) and perfectly suiting medical purposes. It is shown that IR thermography makes it possible to overcome limitations inherent to contact measuring means that were traditionally used before in thermal studies. It is also shown that heterogeneous thermograms displayed by organisms with disturbed inner equilibrium can be quantitatively analysed in terms of statistical parameters of related surface-temperature histograms, such as the mean temperature and the standard deviation of temperature (SDT). The increase and the decrease in SDT turned out to be typical of prolonged physical load and subsequent relaxation, and of external whole-body heating, respectively. Explanation of this result based on a hypothesis advanced within the context of the doctrine of human-organism evolution is given. Skin-temperature distribution function accompanying the relaxed organism in normality was found to closely resemble normal-distribution function. Symmetry break down and variation of the shape of this characteristic may serve as an indicator of homeostasis shift and can be used as a quantitative criterion for the latter. A new phenomenon, stable punctate hidrosis, is discovered and described. The term sweatology is introduced to refer to the discussed specific research area in biomedical science.

Journal Article
TL;DR: In this article, a pulse compression approach is used to detect subsurface discontinuities using linear frequency modulated thermal wave imaging and digitized LFMI thermal wave image. But the proposed technique is limited by the limited depth resolution due to the fixed driving frequency of the excited heat sources.
Abstract: This paper proposes novel techniques for thermal nondestructive testing based on frequency modulated thermal waves. A mild steel sample having discontinuities at different depths is taken as a test sample. The limited depth resolution of the lock in thermography due to the fixed driving frequency of the excited heat sources is overcome by the proposed new technique. A pulse compression approach is used to detect subsurface discontinuities using linear frequency modulated thermal wave imaging and digitized linear frequency modulated thermal wave imaging. In this way, the peak power for probing the specimen can be decreased markedly by increasing the average transmitted energy, which is proportional to the length of the modulated excitation signal. Comparison between the techniques based on the analog frequency modulated signal and its digital form are presented.

Patent
26 Oct 2005
TL;DR: In this paper, a rotatable reflector is used to reflect infrared light from an inspected surface to an infrared sensor, which is magnetically coupled to an actuating portion of the device for concerted movement of the portions.
Abstract: A non-destructive inspection device has an infrared sensor for infrared thermography inspection of a structure or surface. A rotatable reflector reflects infrared light from an inspected surface to an infrared sensor. An inspecting portion of a non-destructive device is magnetically coupled to an actuating portion of the device for concerted movement of the portions. An inspection device includes both an infrared sensor for infrared imaging and an optical device such as a camera for visible light imaging.

Journal ArticleDOI
TL;DR: In this paper, the thermal analysis of a novel micro hotplate design for metal oxide gas sensors is presented, where the temperature distribution across the membrane is measured by means of infrared thermography, and reference measurements are made using an on chip platinum temperature sensor, commercially available thermal melt crayons and K-Type micro thermocouples.
Abstract: This paper reports on the thermal analysis of a novel micro hotplate design for metal oxide gas sensors. The hotplate is a 500 μm × 500 μm square shaped membrane made of 2 μm thick polycrystalline 3C–SiC on a silicon substrate suspended by four legs. The membrane is heated by an on chip platinum thin film heater. For reasons of a short response time and a high sensitivity a uniform temperature profile is desired. In the experiments reported here, the temperature distribution across the membrane is being measured by means of infrared thermography. To verify the absolute temperature of the thermography, reference measurements are made using an on chip platinum temperature sensor, commercially available thermal melt crayons, and K-Type micro thermocouples. The measured temperature results vary depending on the method used between 430 °C for the thermography and 870 °C with the melt crayons at a supplied heater power of 300 mW.

Proceedings ArticleDOI
10 Jan 2005
TL;DR: A 3D thermography imaging standardization technique to allow quantitative data analysis and the generation of combined 3D and thermal data from which thermal signatures can be quantified is developed.
Abstract: We develop a 3D thermography imaging standardization technique to allow quantitative data analysis. Medical Digital Infrared Thermal Imaging is very sensitive and reliable mean of graphically mapping and display skin surface temperature. It allows doctor s to visualise in colour and quantify temperature changes in skin surface. The spectrum of colours indicates both hot and cold responses which may co-exist if the pain associate with an inflammatory focus excites an increase in sympathetic activity. However, due to thermograph provides only qualitative diagnosis information, it has not gained acceptance in the medical and veterinary communities as a necessary or effective tool in inflammation and tumor detection. Here, our technique is base d on the combination of visual 3D imaging technique and thermal imaging technique, which maps the 2D thermography images on to 3D anatomical model. Then we rectify the 3D thermogram into a view independent thermogram and conform it a standard shape template. The combination of these imaging facilities allows the generation of combined 3D and thermal data from which thermal signatures can be quantified.

Journal ArticleDOI
01 Apr 2005-Insight
TL;DR: In this paper, a variant of TNDT for subsurface defect detection based on frequency modulated thermal wave imaging (FMTWI) is described, which is made of the frequency dependence of thermal diffusion length, to achieve entire depth scanning of a sample in one run.
Abstract: Thermal non-destructive testing (TNDT) is a whole field and non-contact technique for defect detection. The present work describes a variant of TNDT for subsurface defect detection based on frequency modulated thermal wave imaging (FMTWI). Use is made of the frequency dependence of thermal diffusion length, to achieve entire depth scanning of a sample in one run. This novel technique overcomes some of the drawbacks associated with traditional pulse and lock-in thermography. Experimental results are presented in support.

Journal ArticleDOI
TL;DR: In this paper, thermal properties of high-power diode lasers are investigated by inspecting their front facets as well as their active regions along the resonator, where hot spots at the front facet, in the substrate, or even in the active region within the substrate are discovered.
Abstract: Imaging thermography in the 3–5μm wavelength range is applied to the analysis of thermal properties of high-power diode lasers We investigate these devices by inspecting their front facets as well as their active regions along the resonator The latter is done through top windows within the substrate Raw data are found to be mostly interfered by thermal radiation traveling through the substrate, which is transparent for infrared light Substracting this contribution and recalibration allows for obtaining realistic temperature profiles along laser structures Facet heating is analyzed complementary by micro-Raman spectroscopy We show how hot spots at the front facet, in the substrate, or even in the active region within the substrate are discovered Our approach paves the way for an advanced methodology of device screening

Journal ArticleDOI
TL;DR: Evidence for the existence of acupuncture-specific, meridian-like artifacts in 6 healthy volunteers is analyzed and different structures appear on thermographic images of the human body which are technical artifacts and which are not identical to what are known as meridians in all textbooks of TCM.
Abstract: Background: According to Traditional Chinese Medicine (TCM) the vital energy flows through a system of channels also called meridians. Generally accepted proof for meridians cannot be considered as being given. Goal of this study was to examine whether possible stimulation-induced meridian-like structures, as recently described by other authors, can be visualized and objectified simultaneously at different infrared wavelength ranges. Methods: The study analyses evidence for the existence of acupuncture-specific, meridian-like artifacts in 6 healthy volunteers (mean age ± SD 28.7 ± 3.7 years; range 25 – 35 years). Two infrared cameras at different wavelength ranges were used for thermographic control of possible stimulation effects (moxibustion-cigar, infrared warmth stimulation, needle and laserneedle stimulation). In addition to thermography, temperature and microcirculatory parameters were registered at a selected point using laser-Doppler flowmetry. Results and Conclusion: After moxibustion (or infrared light stimulation) of the body at 2 – 5 µm and 7.5 – 13 µm ranges, different structures appear on thermographic images of the human body which are technical artifacts and which are not identical to what are known as meridians in all textbooks of TCM. Further scientific studies are required regarding the possible visualization of meridians.

Proceedings ArticleDOI
01 Jan 2005
TL;DR: The main image processing methods used for both passive and active thermography, including 1st and 2nd order statistical thermal signatures are presented.
Abstract: In this paper, the main image processing methods used for both passive and active thermography are presented. 1st and 2nd order statistical thermal signatures are discussed. Typical methods of classification are presented

01 Jan 2005
TL;DR: In this article, two operation modes of lock-in thermography are introduced to detect regions of high series resistance in solar cells, working in the dark and under illumination, where images taken under two different conditions are used to calculate an image.
Abstract: Two operation modes of lock-in thermography are introduced to detect regions of high series resistance in solar cells These are differential techniques, working in the dark and under illumination, where images taken under two different conditions are used to calculate an image, which is especially sensitive to series resistance variations Though the series resistance cannot be measured quantitatively by these techniques, regions of increased emitter contact resistance can be reliably detected A realistic electrothermal modelling of a series resistance defect in a solar cell with and without illumination is presented The new thermographic techniques are compared with established techniques for series resistance imaging Especially the technique working under illumination gives results that agree very well with those of other methods Copyright # 2005 John Wiley & Sons, Ltd

Journal ArticleDOI
TL;DR: In this article, two operation modes of lock-in thermography are introduced to detect regions of high series resistance in solar cells, working in the dark and under illumination, where images taken under two different conditions are used to calculate an image.
Abstract: Two operation modes of lock-in thermography are introduced to detect regions of high series resistance in solar cells. These are differential techniques, working in the dark and under illumination, where images taken under two different conditions are used to calculate an image, which is especially sensitive to series resistance variations. Though the series resistance cannot be measured quantitatively by these techniques, regions of increased emitter contact resistance can be reliably detected. A realistic electrothermal modelling of a series resistance defect in a solar cell with and without illumination is presented. The new thermographic techniques are compared with established techniques for series resistance imaging. Especially the technique working under illumination gives results that agree very well with those of other methods. Copyright © 2005 John Wiley & Sons, Ltd.

Journal ArticleDOI
TL;DR: In this paper, the spectral effects of the illumination source on the hue-temperature characteristics of thermochromic liquid crystals (TLCs) used in a liquid-crystal thermography system were compared.
Abstract: Experiments have been performed to examine the spectral effects of the illumination source on the hue-temperature characteristics of thermochromic liquid crystals (TLCs) used in a liquid-crystal thermography system. Five illumination sources were compared in this study. It was found that “full spectrum” sources, which have a relatively uniform radiant intensity across the visible spectrum, tend to have the lowest temperature uncertainties and the broadest useful ranges, which are desirable calibration attributes. Radiation in the infrared, which leads to (usually undesirable) heating of a test surface, and in the ultraviolet, which can damage TLCs, are discussed for the various light sources. Experimental observations of the effect that UV damage has on liquid crystal calibrations are also provided. The use of a new method called background subtraction and the use of white balancing are investigated as methods of improving the calibration characteristics of TLCs. The uncertainty in temperature associated with different illumination sources and both background subtraction and white balancing is determined and discussed. It is shown that these methods can reduce the uncertainty in some cases.

Journal ArticleDOI
TL;DR: In this paper, Fenot et al. used the heat thin foil technique to impose several heat fluxes and measured the temperature distribution for each flux using infrared imaging, and determined the local heat transfer coefficients and adiabatic wall temperatures by means of a linear regression method.

Journal ArticleDOI
TL;DR: In this paper, the authors use a thermography camera to obtain phase angle images that are independent of most artefacts, which can be applied to metals (crack detection etc) and carbon fibre reinforced laminates where even impact damage can be detected on the front surface.
Abstract: The basic idea is that an induction coil induces eddy currents in conducting materials where the involved resistive losses are used for heating. The remote modulated excitation generates thermal waves that interact with boundaries thereby revealing defects. As a thermography camera monitors the temperature modulation on top of the surface, the response to the coded excitation allows for fast imaging of defects in larger areas without the need of slow point-by-point mapping. This is an essential advantage as compared to conventional eddy current techniques. As compared to inductive heating with visual inspection of the thermographic sequence, the advantage is local phase information resulting in phase angle images that are independent of most artefacts. Due to the Fourier analysis performed at the lockin frequency on the temperature image sequence, the signal to noise ratio in the obtained images is significantly better than in single temperature shots. The inspection method provides images of defects within several seconds, but the applicability is confined to conductive materials. However, it can be applied not only to metals (crack detection etc) but also to carbon fibre reinforced laminates where even impact damage can be detected on the front surface.

Journal ArticleDOI
01 Sep 2005-Insight
TL;DR: In this article, the estimation of bead width and depth of penetration during Tungsten inert gas (TIG) welding using infrared thermal imaging is presented, and the results confirm that IR technique is a sensitive and convenient tool ideally suited to monitor the welding process by mapping and analyzing the surface temperature distributions.
Abstract: The key to the success of robotic welding systems lies in the implementation of adaptive/intelligent welding. Adaptive welding enables dynamic altering of the welding parameters to compensate for changing environment. In a manual welding process, the welder ensures the quality of the weld by monitoring and suitably manipulating the process parameters according to the changing environment and based on his knowledge-base and experience. In the case of adaptive welding, sensors play the role of welder. Welding being a thermal processing method, infrared thermal imaging (thermography) using IR sensors have been a natural choice for sensing and weld process monitoring. This paper highlights the estimation of bead width and depth of penetration during Tungsten Inert Gas (TIG) welding using infrared thermal imaging. The results confirm that IR technique is a sensitive and convenient tool ideally suited to monitor the welding process by mapping and analysing the surface temperature distributions. Comparison of various methods to determine the bead-width during the welding process indicates that using the first derivative, it is possible to obtain a better estimate of the bead-width compared to the full width half maximum or point of inflection methods.

Journal ArticleDOI
TL;DR: In this paper, the authors used a Laplace transform on the time variable t and a Fourier transform on space variables, x and y, to evaluate the depth and volume of the flaw in a three-dimensional heat transfer configuration.
Abstract: This paper is devoted to the characterization of a subsurface flaw within an anisotropic medium during a nondestructive evaluation test using stimulated infrared thermography. A typical illustration is a delamination within a stratified composite material. The originality of the current study consists of providing simple analytical solutions to evaluate the depth and the volume of the flaw in a three-dimensional heat transfer configuration. The volume of the flaw is defined as the product of its lateral extent by its thickness. If the thermal contact resistance of the flaw is known, its lateral extent can be derived from the volume expression. The method proposed here consists of applying first a Laplace transform on the time variable t, then a Fourier transform on the space variables, x and y. The numerical or semi-analytical true solution of integral equations generated by this problem may be very time-consuming, especially in a three-dimensional configuration. We therefore suggest a modelling reduction using the analytical perturbation method written only at its first order. It is however assumed that flaw thermal resistance is small compared to the whole thermal resistance of the material under investigation. The perturbation formalism leads to the construction of approximate analytical solutions that are very convenient for quantitative inversion. The validity of this method has been analysed through a real nondestructive test performed on a calibrated carbon-epoxy laminate of known characteristics.

Journal ArticleDOI
01 Nov 2005
TL;DR: This new facility SATIR UPGRADE has been designed for the full non-destructive examination of the high heat flux (HHF) components taking into account main improvements of the SATIR facility.
Abstract: Among all non-destructive examinations (NDE), active infrared thermography is becoming recognised as a technique available today for improving quality control of many materials and structures involved in heat transfer. The infrared thermography allows to characterise the joint between two materials. In order to increase the defect detection limit of the SATIR test bed, several possibilities have been evaluated. The implementation in 2003 of a microbolometer camera and the improving of the thermosignal process allowed to increase considerably the detection sensitivity of the SATIR facility. The quality, the spatial stability of infrared image and the detection of edge defect have been also improved. The coupling on the same test bed of SATIR method with a lock-in thermography will be assessed in this paper. An improvement of the global reliability is expected by data merging produced by the two thermal excitation sources. This new facility SATIR UPGRADE has been designed for the full non-destructive examination of the high heat flux (HHF) components taking into account these main improvements. These systematic acceptance tests obviously need tools for quality control of critical parts.

Journal ArticleDOI
TL;DR: In this article, a multispectral imaging system that operates in two optical channels, the near IR at 1.5-2μm and the mid IR at 2.4-5.5μm, is applied to investigate the infrared (IR) emission from high-power diode laser bars.
Abstract: Broadband imaging thermography is applied to investigate the infrared (IR) emission from high-power diode laser bars. We demonstrate the capabilities of a multispectral imaging system that operates in two optical channels, the near IR at 1.5–2μm and the mid IR at 2.4–5.5μm. In the near-IR region, deep level luminescence of the device contributes significantly to the thermo-images. A complementary measurement of the IR emission spectrum shows a broad defect band with maxima at E1=0.94eV and E2=1.05eV. Analysis of IR transients in both spectral channels makes a distinction of thermal radiation and deep level emission possible. In the mid IR, thermal radiation dominates, allowing for an analysis of thermal properties of the device with measurement times of fractions of a second only. This makes imaging thermography highly attractive for device screening.

Journal ArticleDOI
TL;DR: In this paper, a transient method using the Laplace transform for estimation of the in-plane thermal diffusivity of low conductive materials is presented, which does not require a knowledge of the stimulation and boundary conditions by using two reference temperature profiles.
Abstract: A transient method using the Laplace transform for estimation of the in-plane thermal diffusivity of low conductive materials is presented. The temperature field of the sample is measured by infrared thermography. The main interest of the technique proposed here is to not require a knowledge of the stimulation and boundary conditions by using two reference temperature profiles. The parameter estimation is implemented in the time domain by an inverse technique using numerical Laplace inversion and convolution products. A sensitivity study has been carried out to optimize the choice of the two reference profiles. The effect of a space varying heat transfer coefficient on the estimated values of the unknown parameters has also been evaluated. Finally, the apparatus is described and experimental results obtained for a low conductive material like a vitroceramic are shown.

Proceedings ArticleDOI
01 Jan 2005
TL;DR: It is suggested that the induced evaporation method can be used to improve the diagnostic accuracy of infrared thermography, especially for tumors at early stages and/or deeply embedded.
Abstract: Infrared imaging has frequently been used in clinics to detect changes in skin surface temperature associated with some superficial tumors. In order to accurately detect and diagnose tumors (especially in their early stages) using infrared thermography, enhancement of thermal expression on the skin over the tumor is desired. This study proposed a novel approach to effectively enhance the skin thermal expression of tumor by induced evaporation on skin surface. To illustrate its feasibility, numerical calculation was first applied to simulate the corresponding heat transfer process, from which the three-dimensional transient temperatures of the biological bodies subjected to induced evaporation were theoretically predicted. Further, preliminary infrared imaging experiments on human forearm were also performed, in which water and 75% (V/V) medical ethanol were particularly chosen to be respectively sprayed on the skin surface. Both the numerical and experimental results indicate that the induced evaporation can significantly enhance the sensitivity of temperature mapping on skin surface over the tumor. The results also suggest that the induced evaporation method can be used to improve the diagnostic accuracy of infrared thermography, especially for tumors at early stages and/or deeply embedded