Showing papers on "Thermography published in 1987"

A clinical microwave thermography system

Abstract: Microwave thermography is the technique of observing the natural thermal radiation from the tissues of the body at centimetric wavelengths to obtain information about internal body temperature patterns. The ability of the technique to relatively directly obtain a measurement of body internal temperatures is the result of the relative transparency of body tissues to microwave radiation at the lower microwave frequencies. Tissue properties are such that, for many medical applications, the optimum measurement frequency is near 3 GHz at which frequency temperature information can be obtained from clinically useful depths of several centimetres within the body while achieving a spatial resolution of one to two centimetres. With proper design of equipment, microwave temperature-pattern measurements can be made independently of the type of tissue being viewed by the measuring antenna. Equipment has been developed which is suitable for routine clinical use. This equipment is being used for clinical assessments of the technique and has demonstrated that microwave thermography can very simply, and with complete safety, provide medically valuable information about disease activity.

Thermographic assessment of skin temperature during a cold provocation test.

Abstract: A description was made of the development and application of infrared thermography and fingertip thermometry for the assessment of finger skin temperature during a cold provocation test. Three hundred and seventeen lumberjacks, grinders, metalworkers, stone cutters, and students were examined in laboratory and field investigations. Under laboratory conditions, the influence of water temperature and exposure duration was studied, and skin temperature measurements were made on the volar and dorsal side of the fingers. In the field occupational health examination, infrared thermography and fingertip thermometry were simultaneously applied during a cold provocation test. The following three types of temperature reaction could be recognized: normal rewarming and moderate delay and strong delay of rewarming. The temperature distribution along the finger length was analyzed. The following conclusions were drawn for practical application of the thermometric methods. Skin temperature must be measured on all 10 fingertips, either on the volar or on the dorsal surface. Fingertip thermometry may be used in occupational health examinations. Infrared thermography may yield more information on the development of disturbances in peripheral circulation along the finger length and may be used in special clinical work.

Microwave thermography—an index of inflammatory joint disease

Abstract: Microwave thermography is a technique measuring microwave emission from sites of inflammation. Microwaves have a wavelength of around 10 cm and are therefore able to penetrate clinically useful depths of up to 4 cm directly measuring tissue thermal radiation. A microwave detector was applied to the study of joint inflammation in rheumatoid arthritis and in a normal control group. Fifty-two knees were scanned using the detector and a microwave thermographic index was calculated for each knee. A strong correlation was found between the microwave thermographic index, and the clinical and laboratory parameters measured. This technique was found to be reproducible, quick, simple to use at the bedside without a controlled environment and, since it measures internally emitted radiation, is inherently safe.

Infrared Thermographic Flaw Detection in Composite Laminates

Abstract: Research performed to develop thermography as a routine rapid flaw detection tool for large composite structures is presented. The externally applied thermal field (EATF) technique is described whereby surface cracks or sub-surface impact damage creates detectable surface temperature perturbations when heated. EATF thermographic procedures and flaw detection capabilities in multidirectional and unidirectional graphite and glass fiber composites are described. The method’s advantages and limitations are outlined.

Liquid crystal thermography in the diagnosis of scaphoid fractures.

Abstract: LCT consists of pliable latex sheets impregnated with cholestrol crystals which respond to different temperatures by emitting different wavelengths of light ranging from brown (cool) through yellow and green to blue (hot). These latex sheets form one wall of a sealed box with the opposite wall being made of perspex to allow the thermographic image to be viewed. The thermographic detectors are calibrated to react to different temperatures. Each one has a mean temperature and responds 2°C above and below this mean. There are eight detectors which respond to mean temperatures of 24, 26, 28, 29, 30, 31, 32 and 33°C. Each box is airtight and has a valve through which air can be pumped to make the pliable latex sheet assume a convex contour which can be moulded around the subject under study. The box is held in a frame with a polaroid camera and a flash unit, thus a permanent picture of the thermographic image can be obtained (Novamedix Ltd, Whitchurch, England).

Electrosurgical dispersive electrodes heat cutaneous and subcutaneous skin layers.

Abstract: Electrosurgical return electrodes can produce heating, and occasionally burns, of cutaneous and subcutaneous skin layers. Up to now, only limited aspects of modern, dispersive, polymer electrodes have been studied using infrared thermography and thermocouples. This report presents new results on a quantitative infrared study, and adds the aspects of subcutaneous effects using microwave thermography as a third dimension. In agreement with previous work in infrared thermography, average cutaneous temperature increases observed in a dozen human volunteers were 1.5 degrees C for the normal mode, and 5.7 degrees C at near-fault (with partial contact). The intradermal and/or subcutaneous microwave thermographic images exhibited slightly lower, but still significant temperature elevations which were located at a more leading location, and were more widespread. This significant heating of subcutaneous layers, particularly of the sensitive stratum germinativum, clearly suggests the need for multiple-depth (microwave and infrared) thermography in order to evaluate the thermal performance of dispersive electrosurgical return electrodes.

Characterization of plasma sprayed coatings using thermal wave infrared video imaging

Abstract: A pulsed (time-domain) thermal wave infrared video imaging technique, using an IR camera, a video image processor, and a flash lamp, is described. This system is applied to the imaging of interfacial defects in plasma sprayed coatings on metallic substrates. Results are compared with the conventional point-scanned cw infrared thermal wave imaging technique.

Aerial Thermography - A Tool For Detecting Heat Losses And Defective Insulation In Building Attics And District Heating Networks

Abstract: Lack of reliable operational methods makes it difficult for potential users to benefit from infrared survey systems which are already well tested technically. In order to develop operational routines for the use of thermography for building and district heating network applications, airborne, mobile and handheld infrared systems have been tested in two different investigation areas. Provided that perturbing factors were taken into consideration and surveys were made during stable weather conditions, with low windspeed, the infrared system tested was found to have good accuracy and low operational cost. An aircraft equipped with an infrared line scanner (8-14 μm) seems to be the best system for surveying larger areas, while helicopter and mobile thermovision systems (8 - 14 μm), are preferable for smaller investigation areas. The best way to analyze thermograms seems to be with an interactive computer-based image analysis systems.

A Bibliography Of Non-Destructive Testing (NDT) Of Composite Materials Performed With Infrared Thermography And Liquid Crystals

Abstract: A BIBLIOGRAPHY OF NON-DESTRUCTIVE TESTING (NOT) OF COMPOSITE MATERIALS PERFORMED WITH INFRARED THERMOGRAPHY AND LIQUID CRYSTALSbyDouglas D. BurleighGeneral Dynamics Space Systems Division San Diego, CaliforniaBIBLIOGRAPHY OF NOT OF COMPOSITE PERFORMED WITH INFRARED THERMOGRAPHY NAME AUTHOR(S) JOURNAL___ VOL. NO. PAGE MONTTTH YEARTheoretical and Practical Aspects of the Thermal Nondestructive Testing of Bonded StructuresCan Thermal Pulse Video Thermography Help to Keep Aircraft Flying Safely?Video - Compatible ThermographyDetectability of Defects by Thermal NOTInfrared NDT of Bonded Structures : Aspects of Theory and PracticeA Model for Quantitative Flaw Detection Using Infrared ScanningThermal Pulse Inspection of Multilayer PartsA Method for Quantitative Characterization of Flaws in Sheets by Use of Thermal-Response DataNondestructive Testing of Honeycomb Structures by Computerized Thermographic SystemsA Thermal Method of Nondestructive Testing Large Parts Carbon-Reinforced PlasticAerostructure Nondestructive Evaluation by Thermal Field Detection; Phase II - Technique Refinement and Quantitative Determination of Flaw Detection CapabilitiesAerostructure Nondestructive Evaluation by Thermal Field Detection; Phase 1 - Fundamental Information and Basic Technique DevelopmentAerostructure Nondestructive Evaluation by Thermal Field TechniquesQuality Control and Nondestructive Evaluation Techniques for Composites - Part VII : Thermography - A State-of-the- Art ReviewThermographic Monitoring of Damage GrowthThermography Applied to Reinforced PlasticsUtility of Thermograpy in Process ControlThermographic Technique for the Nondestructive Evaluation of Graphite Composite StructuresV .P. Vavilov and R. TaylorJ. MilneW. N. Reynolds and C. M. WellsC. M. SayersV. VavilovC. K. Hsieh, et al.V. P. Vavilov and A. 1. IvanovT. V. Baughn and D. B. JohnsonR. Monti and G. MannaraV. T. Shcherbakov, et al.P. V. Me Laughlin, and M. G. MirchandP. V. Me Laughlin, et al.P. V. Me Laughlin,E. G. Henneke and K. L. ReifsniderA. Talug, and K. ReifsniderK. L. Reifsnider and E. G. HennekeR. J. Shuford and B. R. MarketC. W. Soulder and G. E. SingletonResearch Techniques in NDT 5 TestingAerospace Design and ComponentsBritish Journal of NDT 26 1British Journal of NDT 26 1British Journal of NDT 22 4British Journal of NDT 21Soviet Journal of NDT 20 6Materials Evaluation 4434th Congress of the International Astronautical Federation, Budapest, Hungary (IAF-83-419, A1AA A83-47378)Soviet Journal of NDT 1 9 6Naval Air Engineering Ctr. Report NAEC-92-181Naval Air Engineering Ctr. Report NAEC-92-157Naval Air Engineering Ctr. Report NAEC-92-131U.S. Army Aviation Research and Development CommandIRIEDevelopments in Reinforced Plastics Vol. 4 Edited by G. PritchardARO Workshop on Manufacturing ResearchSPIE 366Chapter 7 1982 240-27916-23 May 198640-44 Jan. 28-33 Jan. 1984179-183 July 1980185-192 July 1979381-388 June 850-858 June 1986Oct. 447.449 June 19831-197 Dec. 19841-117 May 19821-35 Nov. 19791-34 Mar. 198229-35 197889-130 1984June 198380-87 1983

Microwave Fields Determined From Thermal Patterns

Abstract: An infrared (IR) measurement technique is described which can be used to detect microwave fields, both continuous wave (CW) and pulsed. The technique involves placing a thin lossy detection screen material in the region over which the electromagnetic (EM) field is to be mapped. The fields are detected through the Joule heating that occurs when EM energy is absorbed by the screen material. When the surface temperature of the screen rises to 0.1 K or higher above the ambient temperature, the induced temperature distribution at the surface of the screen (which corresponds to the EM field intensities in the screen) can be detected by an IR scanning system via emitted thermal radiation. CW measurements by an IR measurement technique have been demonstrated and reported over the past several years. While the technique requires a minimum energy deposition for sufficient heating, the electrical parameters of the detection screen can be selected, such that the thermal mass of the screen is reduced, allowing a faster response. IR data acquisition to a high-speed memory has also been developed to store approximately 500,000 pixels of a two-dimensional IR image in less than three seconds. 5 This corresponds to thirty 128 x 128 frames of data with each pixel element represented as an 8-bit word, which correlates to the electric or magnetic field intensity at that location. As a diagnostic tool, this technique can be used to measure radiated fields and to support tests and evaluations of electronic systems in the presence of EM radiation, e.g., to determine the free-field environments around microwave sources, to determine the energy coupled into electronic circuits through partially shielded enclosures, and to verify hardening techniques. The near, far, and internal fields generated by a microwave horn can be mapped using a thin lossy screen. Apertures in enclosures can be identified by placing a resistive coating on the surface of the metal in the area suspected of containing an aperture. Examples of energy coupled into an electronic circuit and analysis of radiation from antennas are presented. The applications, advantages, and disadvantages of this new infrared technology are also discussed.

Thermal imaging techniques for the non destructive inspection of composite materials in real-time

Abstract: A novel approach for real time inspection of composite materials is presented, which utilises image processing techniques for the characterisation of flaws in composites. The technique is based on transient thermography coupled to the processing of infrared images obtained by exciting the specimen by a thermal pulse. This paper discusses the image reconstruction theory used for defect location, associated image processing techniques, the numerical models for solving the propagation of heat through flawed composites as well as the experimental set-up for testing composites and generating thermal images.

The use of an infrared camera for imaging the heating effect of RF applicators.

Abstract: An infrared camera provides a rapid method of assessing the effective distribution of RF energy on the surface and in the depth of a split phantom. The reduced emissivity appears to cause no problem for qualitative studies and allows the possibility of studying the effects of combined fields or surveying applicators for stray leakage.

Infrared observations of failure processes in plain concrete

Abstract: Infrared thermography has been used as a nondestructive and noncontact technique to analyse the thermomechanical response of plain concrete under a given unconfined compression and subjected to a superimposed vibratory excitation. The experimental investigationconsists of the study of thermographic or heat patterns which are recorded or observed in real time. The parameter investigated is the heat generation due to energy dissipation by the material which has been excited beyond its stable reversible limit.

Evaluating and testing thermographic phosphors for turbine-engine temperature measurements

Abstract: A technique developed earlier for measuring the temperature of inaccessible surfaces in low-temperature rotating machines is being adapted to measure the temperature of surfaces at the higher temperatures and in the erosive environment inside operating turbine engines. The method uses the temperature dependence of the characteristic decay time of the laser-induced-fluorescence of thermographic phosphors to measure the temperature. This paper summarizes recent work in four areas: phosphor characterization and calibration, instrumentation development, bonding, and field tests. By using improved instrumentation and data-analysis techniques, calibration curves for several phosphors are measured with greater accuracy and extended to higher temperatures than before. Phosphors are evaluated that were attached to sample surfaces by high-temperature bonding materials, electron-beam deposition, flame spraying, and plasma spraying. A burner rig test was performed on some phosphor-coated samples and the instrumentation required for an upcoming spin-pit test was designed, built, and calibrated.

Image Processing Software For Real Time Quantitative Infrared Thermography

Abstract: True temperature can be determined from infrared thermography provided the material emissivity and ambient irradiance are known. The measurement equations found in the literature are valid only if the scanner response is linear in radiance. Other complications arise if the emissivity depends on temperature. Spectral (or band) rather than total emissivity values should be used but are less often found in the literature. A new method, specimen calibration, avoids these problems by determining a calibration curve specific to the specimen and experimental arrangement. The computer program VDAS (Video Data Analysis System) automates the collection of calibration data, reduction to a calibration curve, and temperature measurement using the curve. The new method was tested on nylon 6/6 between 20 and 160° C and on 304L stainless steel between 30 and 500° C and was found to be significantly more accurate.

Numerical analysis of heat input effects in thermography

Abstract: A numerical model, suited for use on microcomputers, has been developed to examine the effect of heat input function on surface temperature contrast for passive thermographic NDE. Single and double step input functions have been compared, and the effects of varying pulse length and power, defect condition, defect depth to diameter ratio, and maximum allowed front face temperature rise examined. Results indicate that a two-step heat input function enhances the generated surface temperature contrast by up to 10% over the single pulse and compares well with that generated by contact heating.

Apparatus and system for thermographic identification of parts

Abstract: A method and apparatus for the non-destructive identification of coated and uncoated metal parts employing infrared thermography. The apparatus comprises a means for directing infrared radiation onto the surface of a part; a means for scanning the part surface for reflected infrared radiation; a means for capturing the reflected radiation and converting it into a signal representative of variations in radiation reflected from the surface of the part; means for etching an identifying code into the surface of the part; and means for displaying the signal as a video image. The method comprises altering the surface reflective characteristics of a part to produce an identifying code, irradiating the part with infrared radiation of a specific wavelength and detecting differences in the amount and intensity of radiation reflected from the part.

Using An Imaging Infrared Radiometer To Measure Time-Dependent Temperature Distributions

Abstract: Time- dependent temperature distribution data were obtained from cylindrical nylon test specimens deformed in torsion.The temperatures were measured with an infrared radiometer and calculated with image analysis software. These data providea clear picture of the evolution of the specimen's surface temperature profile prior to and during strain localization and failure.Measurements like these will be used to evaluate parameters in a material model now under development. The data will alsohelp establish the validity of existing numerical methods. Introduction In order to develop new material models that can accurately represent coupled thermal and mechanical behavior, it isnecessary to measure test specimen temperatures as a function of deformation rate. In general, temporal and spatial resolutionare both needed to define the development of the temperature field during a test. The most common way of obtaining suchdata is with an array of spot detectors (e.g. thermocouples). Unfortunately, even though these detectors may provide goodinformation at a particular point, they can influence the response of a specimen (thermocouples have been observed to initiateareas of strain localization). In addition, spot detectors can be difficult to attach to nonmetallic specimens. The resultingpoor contact may lead to ambiguous data.Because of the drawbacks associated with spot detectors, we used an imaging infrared radiometer to measure the temper-ature of nylon specimens undergoing torsional deformation. This technique provides accurate, full -field surface temperaturemeasurements without contacting the specimen. Because of the full field measurement, the temperature at the time and the

Subcutaneous Temperature Measurement by Microwave Thermography

Abstract: Electromagnetic and thermal models have been developed to assist the interpretation of microwave thermographic data. The electromagnetic modelling is strongly dependent on the tissue dielectric properties and the thermal modelling is strongly dependent on the tissue thermal conductivity. These tissue properties all have a similar dependence on tissue water content, which allows tissue behaviour to be specified in terms of its water content for combined thermal and electromagnetic modelling. This modelling has been successfully applied to several body regions and, in particular, is being used to study variation of blood supply to the female breast.

Thermal Imaging System For Material Processing

Abstract: In the field of lasers for welding and surface processing, we need to measure the map of temperatures in order to control the processing in real time by adjusting the laser power, the beam pointing and focussing and the workpiece moving speed. For that purpose, we studied, realized and evaluated a model of thermal imaging system at 2 wavelengths in the mid-infrared. The device is connected to a 3 axis table and to a 3 kW CO 2 laser. The range of measured temperatures is 800 C to 1 500 C. The device includes two AGEMA infrared cameras fixed to the welding torch each operating with a choice of filters in the 3, 4 and 5 micrometre band. The field of view of each is about 14 mm by 38 mm. The cameras are connected to an M68000 microprocessor family based microcomputer in which the images enter at the rate of 6. 25 Hz with 64 x 128 pixels by image at both wavelengths. The microcomputer stores the pictures into memory and floppy disk, displays them in false colours and calculates for each pixel the surface temperature of the material with the grey body assumption. The results have been compared with metallurgic analysis of the samples. The precision is about 20 C in most cases and depends on the sample surface state. Simplifications of the laboratory device should lead to a cheap, convenient and reliable product.

Microwave thermography in rheumatic disease.

Abstract: Microwave thermography is a technique measuring emitted microwave radiation from sites of inflammation. The wavelength used is of the order of 10 cm and is therefore able to penetrate to clinically...

Temperature Measurement Using Video Cameras

Abstract: Video cameras can be used for surface temperature estimation from the measured radiance at single wavelengths or from the ratio of radiance at two wavelengths. This paper discusses limitations of video thermography for both methods in the near-, mid-, and far-IR regions.

Infrared Transparencies (Thermoscenes) For Simulation Of Infrared Scenes As A Tool To Improve Flir Testing

Abstract: The Minimum Resolvable Temperature Difference (MRTD) is a classic performance parameter, used by manufacturers of thermal imaging systems (FLIR's) in the characterization and final testing of such devices. The Johnson criterion [1] relates the MRTD to practical characteristics, such as the ability of the FLIR to resolve objects, as function of distance. However, the MRTD measurement suffers from several drawbacks,e.g. i) it is subjective, ii) it fails to account for complex real life situations, such as background and foreground clutter, object shape and non-uniformities of temperature and emissivity. This paper describes a new type of transparency which has been developed to simulate real infrared scenes. The transparency consists of a half-tone mesh of variable size holes which, when placed in front of a blackbody, simulates a two dimensional radiant emittance pattern. The pattern itself can be generated from a thermal image of any real object as seen by a high performance FLIR, from an artificially computer generated image, or from a combination of the two. Examples of thermoscenes and measurements of radiation distribution over a simple pattern are shown. Potential applications of the thermoscenes are also discussed.

An Investigation Into The Factors Affecting Infrared Temperature Measurements For Building Applications

Abstract: Various factors affecting infrared temperature measurements are discussed. Temperature calibration curves at surrounding temperatures between -20°C and 25°C are presented for two infrared imaging systems operating in the 2 to 5 μm and 8 to 14 μm wavelength regions. The calibration curves for the 2 to 5 μm system were found to be independent to surrounding temperatures, while the calibration curves for the 8 to 14 μm system were found to be strongly dependent to surrounding temperatures. Equations to account for changes in surrounding temperatures are presented. Laboratory measurements of emissivity using both systems at different surrounding temperatures (22°C, 4°C, and -11°C) are given for several typical building materials. The emissivity measurements are used in computing surface temperatures of the materials. Comparisons are made between predicted and measured surface temperatures.