Showing papers on "Thermography published in 1993"
TL;DR: In this paper, an overview of NDE using infrared thermography using external thermal stimulation and internal thermal stimulation is presented, along with a quantitative analysis of delaminations inspection of materials with low emissivity by thermal transfer imaging.
Abstract: Overview of nondestructive evaluation (NDE) using infrared thermography theoretical aspects experimental apparatus external thermal stimulation - methods and image processing internal thermal stimulation - methods and image processing quantitative analysis of delaminations inspection of materials with low emissivity by thermal transfer imaging thermal diffusity measurements of materials thermal tomography thermal NDE of nonplanar surfaces applications of infrared thermography to high temperatures.
423 citations
01 Nov 1993
TL;DR: The characteristics of Honeywell's two-dimensional (2D) arrays of micromachined microbolometers were summarized in this paper, and practical methods of operating these arrays in high-sensitivity room-temperature infrared (IR) imaging systems were discussed.
Abstract: This article summarizes the characteristics of Honeywell's two-dimensional (2-D) arrays of micromachined microbolometers, discusses practical methods of operating these arrays in high-sensitivity room-temperature infrared (IR) imaging systems, and describes recent performance measurements.
204 citations
TL;DR: This article found that 95% of the normal population have an interocular temperature difference (temperature of center of right cornea minus temperature of centre of left cornea) of 0.60 degrees or less.
Abstract: Thermography is an investigative technique which allows rapid color-coded display of the temperature across a wide surface by means of infrared detection. We describe an ocular thermographic study of a normal population and present case studies describing the application of this technique for patients with ocular disease. We found that 95% of the normal population have an interocular temperature difference (temperature of center of right cornea minus temperature of center of left cornea) of 0.60 degrees or less. There appears to be a greater difference in temperature between the limbus and the center of the cornea in patients with dry eyes. This technique has potential for evaluating tear film disorders and inflammatory conditions, for monitoring the progress of such conditions, and for evaluating the efficacy of various treatments.
102 citations
Patent•
07 Jun 1993
TL;DR: In this paper, a system including a mobile infrared thermography unit and a base station for automating the collection of thermographic data and for facilitating the efficient generation of reports is described.
Abstract: A system including a mobile infrared thermography unit and a base station for automating the collection of thermographic data and for facilitating the efficient generation of reports. The mobile infrared thermography unit includes an infrared camera, a storage device such as a videotape recorder for at least recording thermographic images captured by the infrared camera, and a mobile unit computer. The mobile unit computer includes a touch screen display for presenting information to a thermographer and for receiving data and command inputs from the thermographer. The mobile unit computer is interfaced to the infrared camera or the videotape recorder for maintaining a record, either by tape position or date/time stamp, where thermographic images of particular equipment are recorded. The mobile unit computer includes a display operable to prompt the thermographer with route information regarding particular equipment to be thermographically inspected, as well as to suggest to the thermographer particular problems possibly indicated by a particular thermographically-observed condition. The base station includes a base station computer which transfers information to the mobile unit computer prior to undertaking an inspection route, and receives information from the mobile unit computer when the route is completed. The base station computer is capable of directly accessing and downloading particular infrared images recorded by the videotape recorder, employing the tape position or date/time stamp information.
86 citations
13 Aug 1993
TL;DR: In this article, the authors investigated the polarization properties of thermal IR radiation (8 - 12 micrometers ) and built an infrared imaging polarimeter and participated in field and laboratory experiments.
Abstract: Modern infrared (IR) imaging systems are sensitive enough to detect weak targets, but background clutter makes the detection difficult. The introduction of an IR polarizer into thermal imaging systems is one of the techniques to improve this low target-to-clutter ratio. The use of polarized IR energy helps to detect man-made objects in complex natural backgrounds. Over the past 4 years, we have investigated the polarization properties of thermal IR radiation (8 - 12 micrometers ). In the course of our work, we have built an infrared imaging polarimeter and participated in field and laboratory experiments. This paper summarizes the results of our work. It includes a brief theoretical background, description of the equipment, and a comparison of our empirical findings with a theoretical model and with results of other researchers.
46 citations
TL;DR: In this article, the authors calculated the edge effects for a crack-like defect using the Wiener-Hopf technique and used them in an analytical model to explain transient thermographic image formation.
Abstract: Thermal edge effects for a cracklike defect have been calculated using the Wiener–Hopf technique These have been used in an analytical model to explain transient thermographic image formation The analysis has led to a simple method for defect sizing which is demonstrated using experimental results
27 citations
01 Nov 1993
TL;DR: In this paper, the authors present a survey of the capabilities of currently available room temperature infrared focal plane arrays and an example of how this technology could perform in a real world situation is presented from a theoretical point of view.
Abstract: The technology behind infrared focal plane arrays capable of operating at room temperature is discussed, emphasizing bolometric and pyroelectric devices. Theoretical limitations of thermal imagers operating at room temperature are explored and presented. The results of a survey cataloging the capabilities of currently available room temperature infrared focal plane arrays are presented. An example of how this technology could perform in a real world situation is presented from a theoretical point of view to show possible imaging system limitations due specifically to the room temperature focal plane.
24 citations
TL;DR: In this paper, a lock-in thermographic system was used to monitor the electromagnetic field by modulating the amplitude of the interference field and a multimode field inside a waveguide.
Abstract: Electromagnetic fields can be monitored by infrared thermography, using sensitive paints or coatings deposited on structures or thin films. Enhancement of the method by release of convective losses and conduction effects is demonstrated. This is obtained by modulating the amplitude of the fields and using a lock-in thermographic system. Examples of application are given which concern an interference field and a multimode field inside a wave-guide.© (1993) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
24 citations
01 Apr 1993
TL;DR: In this article, a 0.25mm-thick (0.01 inch) fiberglass screen is used to capture the temperature distribution within an airstream, which can be positioned perpendicular or parallel to the flow to obtain three-dimensional spatial measurements.
Abstract: In this paper, several automotive climate control applications for IR thermography are described. Some of these applications can be performed using conventional IR techniques. Others, such as visualizing the air temperature distribution within the cabin, at duct exits, and at heater and evaporator faces, require new experimental methods. In order to capture the temperature distribution within an airstream, a 0.25-mm-thick (0.01 inch) fiberglass screen is used. This screen can be positioned perpendicular or parallel to the flow to obtain three-dimensional spatial measurements. In many cases, the air flow pattern can be inferred from the resulting temperature distribution, allowing improved air distribution designs. In all cases, significant improvement in the speed, ease, and quantity of temperature distribution information can be realized with thermography as compared to conventional thermocouple array techniques. Comparisons are presented between IR thermography images and both thermocouple measurements and computational fluid dynamics (CFD) predictions.
23 citations
01 Jan 1993
TL;DR: In this article, the authors present a set of recommendations for future research by the rapporteurs for infrared thermography recommendations, based on the requirements interferometry and spectroscopy.
Abstract: Projects - requirements interferometry - spectroscopy temperature - concentrations pressure - forces velocity heat flux infrared thermography recommendations for future research by the rapporteurs.
TL;DR: In this paper, a description of infrared (IR) thermography, as it is employed in a hypersonic blowdown wind tunnel for the acquisition of high quality two-dimensional heat transfer data over aerodynamic surfaces, is given.
Abstract: A description of infrared (IR) thermography, as it is employed in a hypersonic blowdown wind tunnel for the acquisition of high quality two-dimensional heat transfer data over aerodynamic surfaces, is given. It is shown that the availability of an IR scanning radiometer and a standard digital image processing (DIP) system in the laboratory provides the means for highly efficient (in terms of time and cost) heat transfer measurement, with accuracy levels comparable to those achieved by classical discrete point gauges, such as thin-film surface resistance thermometers and thermocouples. The advantages of IR thermal mapping over the classical techniques, not only in measuring heat transfer distributions over complex three-dimensional configurations and in locating and quantifying highly localized hot spots, but also in interpreting puzzling results observed on simple configurations, are illustrated using a series of examples. A discussion of the limitations of the technique indicates that most of such limitations are common to classical 'zero-dimensional' instrumentation as well. >
Journal Article•
TL;DR: In this paper, a transient thermography (TTH) was used to detect delaminations, disbonds and lack-of-adhesion in a wide diversity of coated and uncoated materials.
Abstract: Thermal imaging enables the observation and resolution of structural defects based on the visualisation of temperatures of components relative to their surroundings. The technique's ability to furnish useful data for nondestructive examination is improved by generating a temperature, gradient in the material. Any flawed regions will inhibit the passage of heat, causing the flaw to be contrasted against its surroundings when viewed using a thermal imager. This technique, called transient thermography, was developed at Harwell, and has been shown to be capable of detecting delaminations, disbonds and lack-of-adhesion in a wide diversity of coated and uncoated materials. It is also capable the quality of composites. It therefore has a great deal to offer for the inspection of aerostructures
TL;DR: In this article, a method is described, in which infrared thermography is used to detect changes in the temperature image occurring in paper during a tensile test, which can facilitate the study of the local deformation process of paper.
Abstract: A method is described, in which infrared thermography is used to detect changes in the temperature image occurring in paper during a tensile test. Thermography has been found to be useful instead of calorimetry for detecting the local variations in surface temperature and the thermal energy transfer in paper under strain. The changes in temperature images during the course of tensile straining can facilitate the study of the local deformation process of paper.
05 Jan 1993
TL;DR: The addition of a calibration capability in the 8-14 micron thermal infrared region to the current ground-based calibration of orbiting sensors is discussed in this article, where three methods to determine the effect of sky background on the thermal emittance of the ground are presented, along with use of LOWTRAN 7 to determine atmospheric effects.
Abstract: The addition of a calibration capability in the 8-14 micron thermal infrared region to the current ground-based calibration of orbiting sensors is discussed. Radiance- and reflectance-based methods are compared. An infrared thermometer was selected as the favored instrument for the determination of ground truth. Three methods to determine the effect of sky background on the thermal emittance of the ground are presented, along with use of LOWTRAN 7 to determine atmospheric effects.
TL;DR: In this paper, the authors used dual-band infrared computed tomography (DBIR) to study surface temperature differences at the epoxy-glue disbond site of a flash-heated lap joint.
Abstract: We discuss three-dimensional dynamic thermal imaging of structural flaws using dual-band infrared (DBIR) computed tomography. Conventional (single-band) thermal imaging is difficult to interpret. It yields imprecise or qualitative information (e.g., when subsurface flaws produce weak heat flow anomalies masked by surface clutter). We use the DBIR imaging technique to clarify interpretation. We capture the time history of surface temperature difference patterns at the epoxy-glue disbond site of a flash-heated lap joint. This type of flawed structure played a significant role in causing damage to the Aloha Aircraft fuselage on the aged Boeing 737 jetliner. The magnitude of surface-temperature differences versus time for 0.1 mm air layer compared to 0.1 mm glue layer, varies from 0.2 to 1.6 degree(s)C, for simultaneously scanned front and back surfaces. The scans are taken every 42 ms from 0 to 8 s after the heat flash. By ratioing 3 - 5 micrometers and 8 - 12 micrometers DBIR images, we located surface temperature patterns from weak heat flow anomalies at the disbond site and remove the emissivity mask from surface paint of roughness variations. Measurements compare well with calculations based on TOPAX3D, a three-dimensional, finite element computer model. We combine infrared, ultrasound and x-ray imaging methods to study heat transfer, bond quality and material differences associated with the lap joint disbond site.© (1993) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
TL;DR: In this article, the authors proposed a method to identify the delamination parameters of a defective slab (thermal contact resistance and depth) starting from an experimental thermal contrast curve, and the definition of a locally normalized contrast that allows us to process real experiments with the one-dimensional model, together with the calculation of Laplace transforms of this contrast, make the construction of identified contact resistance profiles (rear face) or of identified depth profiles (front face).
03 Dec 1993
TL;DR: In this article, a new thermographic technique, Forced-Diffusion Thermography (FDT), is described, which uses a continuously projected dynamic heat pattern to set up appropriate combinations of lateral and through-depth heat flow in structures.
Abstract: A new thermographic technique, Forced-Diffusion Thermography (FDT), is described. Forced-Diffusion Thermography uses a continuously projected dynamic heat pattern to set up appropriate combinations of lateral and through-depth heat flow in structures. A synchronous imaging IR camera is used to measure the structures thermal response to a patterned heat flux in order to find flaws such as cracks and delaminations. A numerical model of the technique is used to describe the thermal responses to cracks and delaminations. Experimental data is presented for the case of a fatigue crack in a 2 mm thick aluminum skin.
TL;DR: In this paper, the effects of the emissivity of an object, the ambient temperature, the atmospheric conditions surrounding the object, and its size and distance from the camera on the temperatures observed by the IR camera are discussed.
Abstract: Infrared (IR) thermography applications in the design, development and production of printed circuit boards (PCBs), hybrid circuits, microcircuits, and other electronic components are described. This noncontact temperature measurement technique can capture a highly accurate record of the thermal dynamics of small objects at intervals as short as 1/30th of a second. It is ideal for studying the heat distribution across boards to determine the optimum layout of components, the effectiveness of proposed heat-dissipation and -removal devices, and the performance of developmental systems under stimulated load conditions. The effects of the emissivity of the object, the ambient temperature, the atmospheric conditions surrounding the object, and its size and distance from the camera on the temperatures observed by the IR camera are discussed. >
TL;DR: In this paper, a method for estimating the groove depth in laser machining processes based on temperature measurements was discussed, where the temperature field was measured through infrared thermography, an analytical model relating temperature to groove depth was used to predict the groove depths given a temperature measurement and its location.
Abstract: Summary This paper discusses a method for estimating the groove depth in laser machining processes based on temperature measurements. The temperature field was measured through infrared thermography, an analytical model relating temperature to groove depth was used to predict the groove depth given a temperature measurement and its location. Theoretical and experimental results are compared and discussed.
TL;DR: In this article, the authors discuss the higher demands on the performance of the imaging objective and provide some guidance in how to deal with them, and discuss how to build more compact and lighter thermal imaging systems.
Abstract: Focal plane arrays (FPA) have eliminated bulky scanning mechanisms. While it is now possible to build more compact and lighter thermal imaging systems, the demand on the performance of the imaging objective has increased. To discuss these higher demands, and to provide some guidance in how to deal with them, is the purpose of this paper.
TL;DR: In this article, the U.S. Army's FLIR92 sensor performance model was used to predict laboratory performance for staring focal plane array (FPA) thermal imagers.
Abstract: With the increasing availability and applicability of staring focal plane array (FPA) thermal imagers, the accurate modeling of these sensors is a critical requirement within the infrared community. The FLIR92 sensor performance model, developed by the U.S. Army Night Vision and Electronic Sensors Directorate (NVESD), provides the capability to predict laboratory performance for staring FPA thermal imagers. FLIR92 uses readily available system level parameters to predict the device MRTD and MDTD. This paper illustrates the techniques used in the model by evaluating performance for a staring FPA thermal imager.
28 May 1993
TL;DR: A dedicated algorithm devoted to large building quantitative inspection, which detects suitable reference structures put in the field of view by means of a visual image processing and identifies the 3D position of the wall.
Abstract: Large building quantitative inspection needs both automatic correction of perspective distortion and precise air and surface temperature measurement. Unfortunately these operations are heavily time consuming if performed manually by a human operator. We present a dedicated algorithm devoted to this task. The procedure first of all detects suitable reference structures put in the field of view, by means of a visual image processing and identifies the 3D position of the wall. The second step matches the thermogram with the visual image of the object. The third step performs an inverse perspective projection applying a thermal camera model, the output is a corrected radiance field. The fourth step measures the air temperature on the reference and the surface temperature map. The surface temperature can be obtained by absolute, relative or differential methods mainly depending on object emissivity value and its spatial distribution.
TL;DR: In this article, a measurement technique to determine the surface heat transfer distribution in complex turbulent flows is described, and a constant wall heat flux test surface has been designed for this purpose.
Abstract: A measurement technique to determine the surface heat transfer distribution in complex turbulent flows is described. For this purpose, a constant wall heat flux test surface has been designed. To measure the surface temperature of the test plate, an infrared camera was used. The instrumentation allows the determination of the heat transfer with high accuracy and detailed spatial resolution. In examining combustor-type separated flow, the capabilities of the technique are demonstrated and its accuracy is verified by appropriate conventional techniques.
01 Jan 1993
TL;DR: In this article, a unique Heat Transfer Jet Impingement Facility (HJIF) has been designed and constructed for testing nozzles, and the performance of the noizles at various flow and operating conditions is evaluated from infrared images and computer codes.
Abstract: Infrared images of jet impingement are used to evaluate the effectiveness of heat transfer due to an air jet from a nozzle striking a surface. A unique Heat Transfer Jet Impingement Facility (HJIF) has been designed and constructed for testing nozzles. The nozzles to be tested are mounted in the facility. The performance of the nozzles at various flow and operating conditions is evaluated from infrared images and computer codes. The experimental apparatus and the operational procedures for the utilization of the infrared images are described. This unique application of infrared imaging as a research and development tool for determining air nozzle performance at steady state conditions has been found to be generally superior to earlier approaches.
TL;DR: In this article, a subsonic wind tunnel was used to obtain measurements of radiant power over a constant-heat-flux ribbed surface and the results showed the development of the thermal field near the origin of the ribbed surfaces.
Abstract: Convective heat transfer over ribbed surfaces is a very complex process that requires detailed measurements for further understanding. The experimental technique presented in this article is a viable alternative to existing methods for providing local heat transfer measurements on a surface of complex geometry. Infrared (IR) thermography was used in a subsonic wind tunnel to obtain measurements of radiant power over a constant-heat-flux ribbed surface. The results using this procedure show the development of the thermal field near the origin of the ribbed surface. Velocity and pressure drop data illustrate the significant changes in the flow field (near the first ribs), which correlate with the infrared data for the thermal field.
01 Nov 1993
TL;DR: In this article, a scanning imaging system that simultaneously generates visual or near-infrared (NIR) and far infrared (FIR, 8 to 12 micrometers ) digitized images is described.
Abstract: A scanning imaging system that simultaneously generates visual or near-infrared (NIR, < 2 micrometers ) and far infrared (FIR, 8 to 12 micrometers ) digitized images is described. The visible or NIR images are presentations of reflected radiation at the corresponding wavelengths. The FIR emission is calibrated with thermostated black bodies to yield a thermal image. The system was designed to produce twin images, with identical perspective and scale factor, that can be overlayed to allow unambiguous identification of the observed object and precise location of thermal features on the observed object. This system has a variety of uses, especially in clinical applications of telethermometry. The visual imaging system is designed to use the same optical scanning configuration as that which generates the thermometric data. The camera's optical scanning system is described, as are the electronics of the imaging system, including the design of the photodiode amplifier, pixel trigger generator, digitizer and the computer interface circuits. A few experimental images taken by this system are also presented.© (1993) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
TL;DR: In this article, the temperature distribution in the condensed and gas phase during combustion of polymer materials in fire tests was measured by means of thermography, and it was shown that these data are very useful for mechanistic rationalization of the diagnostically poor, fail-pass rating of most of these tests.
Abstract: The temperature distribution in the condensed and gas phase during combustion of polymer materials in fire tests was measured by means of thermography. It is shown that these data are very useful for mechanistic rationalization of the diagnostically poor, fail-pass rating of most of these tests. Preliminary data were obtained for polymer materials, fire retarded or not, burning in the widely used Glow Wire and UL 94 tests. It is shown that the relative fire hazard and test rating may depend strongly on the combustion parameter on which the rating is based. Furthermore, detailed data on temperature distribution are helpful in eliminating intrinsic ambiguity of the UL 94 classification in the case of fire-retarded materials burning with dripping.
TL;DR: In this paper, a scanning electron microscope is used to reveal hot regions in microelectronic devices, with a spatial resolution in the submicrometer range, using a focused, low-energy electron beam charging the insulator during the scanning process.
Abstract: Charging insulating films in a scanning electron microscope is shown to be a potentially useful thermographic technique which makes it possible to reveal hot regions in microelectronic devices, with a spatial resolution in the submicrometer range. This technique entails depositing an insulating film on the device to serve as thermographic medium. A focused, low‐energy electron beam charges the insulator during the scanning process. Hot regions modify the local charge, which in turn modifies the secondary electron signal and thus generates a thermal contrast. This technique has been applied to investigate mirrors of GaAs/AlGaAs graded index separate confinement single quantum well laser diodes. Thermographic images of these mirrors have been obtained with a spatial resolution of 0.25 μm. Since the thermal images can be observed using the scanning electron microscope’s TV mode, the course of fast thermal phenomena at laser mirrors can be imaged. As an example, the thermal drift prior to the thermal runaway at laser mirrors has been investigated.
01 Jan 1993
TL;DR: The first law of thermodynamics introduces the energy conservation principle and explains that any industrial process consuming energy will see a great part of this energy be transformed into heat (following the law of entropy).
Abstract: Even before Max Planck published his theory of radiation on 14 December, 1900, measurement of temperature was of concern to Mankind. The first law of thermodynamics introduces the energy conservation principle and explains that any (industrial) process consuming energy will see a great part of this energy be transformed into heat (following the law of entropy). Temperature is therefore an important parameter to measure. The glass thermometer, invented by Galileo in 1593, was the first instrument for quantitative temperature measurement (Wise 1988). It allowed Herschel in 1800 to discover the infrared spectrum. Nowadays, temperature scale is ruled by international norms: the freezing point of gold (also known as the gold point) is the basic standard for the International Practical Temperature Scale (IPTS).