Since the late seventies DND through the Director General Works has been actively encouraging the use of thermography as an efficient and effective technique for supporting preventive maintenance quality assurance and energy conservation programs at Canadian Forces Bases (CFBs). This paper will provide an overview of DND''s experiences in the utilization of thermography for facilities maintenance applications. 1. HISTORICAL MILESTONES The following are milestones of DND''s use of thermography: a. Purchase of Infrared Equipment In 1976/77 DND purchased five AGA 750 Infrared Thermovision Systems which were distributed to commands. In 1980/81/82 six AGA liOs five AGA TPT8Os two AGA 782s and one AGA 720 were acquired. Finally DND also purchased seven AGEMA 870 systems during 1987/88. b. First and Second Interdepartaental Building Thermography Courses In 1978 and 1980 DND hosted two building thermography courses that were conducted by Public Works Canada. c. CE Thermographer Specialist Training Courses DND developed a training standard in 1983 for Construction Engineering (CE) Thermographer qualification which included all CE applications of thermography. The first annual inhouse training course was conducted at CFB Borden Ontario in 1984. These are now being conducted at the CFB Chilliwack Detachment in Vernon British Columbia. 2 . MARKETING FACILITIES MAINTENANCE IR Of paramount importance for successfully developing DND appreciation for thermography was providing familiarization training to CE staff at commands and bases. These threeday presentations emphasized motivational factors conducting thermographic surveys and utilizing infrared data of roofs electrical/mechanical systems heating plants steam distribution and building enclosures. These factors consisted mainly of the following objectives: a. preventive maintenance by locating deficiencies to be repaired b. quality assurance by verification of workmanship materials and design c. energy conservation by locating heat loss areas 2 / SPIE Vol. 1313 Thermosense XII (1990)

Excessive Electrical Resistance Leaking (Tracking) Voltage Induced Voltage and Solar Magnetic Disturbances are four deviations that develop in high voltage electrical systems. This technical publication specifically directs these occurrences to the power company''s various voltages of transmission and also the many configurations of distribution. It is the intention of 1. 5. 5. Thermographic Testing Inc. to contribute information ascertained from actual case studies and electrical inspections over a course of several years. This publication presents methods findings variables and guidelines for the thermographic inspection programs implemented by power companies. 2.

As has been reported in the past (ref. 16), there are considerable uses for infrared imaging within the commercial nuclear industry. What was lacking was a source book to assist the individual utilities in establishing a program of inspections, identifying the resources available, and identifying the potential applications. Through research project RP 281418, The Electric Power Research Institute (EPRI) contracted the American Risk Management Corp. to write such a document. This paper highlights the final document and discusses the lessons learned from it.

A methodology based on IR Thermography measurements is proposed to estimate real istic values of hardware failure rates corresponding to secondary failures that is those caused by past or present outoftolerance or abnormal operating conditions. The methodology allows the establishment of useful correlations between these failure rates and the corresponding relevant thermal patterns as mapped using IR Thermography. The methodology is applied to practical cases of secondary failures in typical electrical and mechanical components having to do with failure modes due to abnormal stress corrosion and friction. The application of this technique to fault and failure diagnosis and both Reliability Availability and Maintainability (RAM) Analysis and Probabilistic Risk Assessment (PEA) is also briefly discussed. 1.

Abstract not available.

Imaging systems technology has been utilized traditionally for diagnosing structural envelope or insulation problems in the general thermographic comunity. Industrially, new applications for utilizing thermal imaging technology have been developed i n pred i cti ve/preventi ye mai ntenance and prod uct moni tori ng prociures at Eastman Kodak Company, the largest photographic manufacturering producer in the world. In the manufacturing processes used at Eastman Kodak Company, new applications for thermal imaging include: (1) Fluid transfer line insulation (2) Web coating drying uniformity (3) Web slitter knives (4) Heating/cooling coils (5) Overheated tail bearings, and (6) Electrical phase imbalance. The substantial cost benefits gained from these applications of infrared thermography substantiate the practicality of this approach and indicate the desirability of researching further appl i cati ons.

As nuclear power generating station management personnel begin to implement infrared thermal analysis programs to monitor selected equipment they are faced with the inter-related problems of acquiring appropriate IR sensing equipment and designing programs which can initially provide them with the thermal data necessary to evaluate selected components. In addition, in order to have a truly useful program they must also provide for later inclusion of additional components and, if possible, retrieval of their historical thermal data as well. This paper briefly highlights some of the desirable features management should consider during the IR equipment evaluation stage, and presents a dual level approach to IR monitoring program design which is flexible enough to allow station management to initiate a complete IR monitoring program focusing on a selected list of components, while recording thermal images of additional components to allow for their later inclusion into the program.

The realities involved in performing thermographic diagnostic surveys are often not well understood by the therrnographer. With an interest in the growth of the thermographic coimnunity, and an understanding that proper application promotes growth, equipment manufacturers have considered training and education a worthwhile investment. This paper summarizes the training and technical assistance experience of one manufacturer as a recommended body of knowledge for thermographers. Five key areas are presented: Radiosity, Spatial Resolution, Heat Transfer, Equipment Operation, and Target Behavior.

As the American Society of Civil Engineers (ASCE) and the American Concrete Institute (Ad) work toward the adoption of new standards in masonry construction, a new level of quality control inspection is becoming mandatory. Required inspections will focus on evaluating masonry for compliance with the design specifications with regard to material, structural strength and thermal performance. The use of video infrared thermography provides a thorough, systematic mathod of masonry construction inspection. By video taping the survey, potential controversy can be alleviated by reviewing the permanent video taped record.

For district heating networks, practical applications of aerial thermography involve problems usually neglected in the process of research and methodological development. This process is usually initiated by first examining physical conditions for the specific application. Then is developed a method designed for the application. However, there should also be a test of the thermographic method in practice, including both an operational and economical evaluation of different stages of the application, suggesting feasible changes of the method and of the operational organisation. Experience from thermographic studies performed in the Scandinavian countries implies that follow-up studies are necessaiy when introducing high tech methods for practical applications. This kind of studies gives experience in major problems connected to different operational conditions, and makes it possible to avoid failures and to optimise the use of the information of the thermographic method. This paper deals mainly with the evaluation of aerial thermography for district heating networks applications. The main conclusions are that aerial thermography can contribute to an efficient operation of district heating systems, and the method is sufficiently developed for commercial use. However, the method could be improved by ensuring a feedback from the utility to the thermography consultant, so that analysis and interpretation routines, and presentation of results, may be further adjusted to user requirements. Also, increasing the knowledge possessed by the consultant and maintenance personnel regarding technical properties of culvert systems and thermographic methods, would result in more efficient procedures.

One of the tools traditionally used in assessments of the thermal status of buildings is the application of JR-techniques. This application has to a large extent been restricted to indoor inspections of attics, external walls and basements, or to roof inspections by means of aerial thermography, or to detection of air leaks by pressurisation of the building. These applications have, in general, been very successful. In this paper is presented an evaluation of a staged process where major building envelope anomalies have been detected by outdoor thermography, classified using indoor thermography, moisture meters and fiber optics techniques, and evaluated with regard to their impact on energy consumption and envelope performance. In the evaluation of this process, inspections of external walls using indoor thermography and vehicleborne outdoor thermography have been compared to one another regarding factors such as the number of suspected thermal anomalies detected, the accuracy in predicting real damages, the time required for the operation and the image analysis, factors limiting operational efficiency, and the ease of the operation. Also, the measured external surface temperatures have been compared to those predicted by an analytical calculation. It is concluded that vehicle-borne JR-inspections may provide a quick way of detecting building thermal anomalies. The prediction accuracy relative to indoor inspections to some extent depends on the building design. However, most major damages detected by indoor thermography can, under suitable operating conditions, be detected also from the outside. Thus, a process combining outdoor thermography to detect building anomalies and indoor thermography to survey selected details, in a cost-efficient way gives a rather complete picture of building damages and building thermal status. To make an efficient use of the thermographic data collected, the information should be stored in a data base containing also other data on the building, for example, data on building function,design and operation. The whole process of gathering data by IR-techniques should be integrated into already existing schemes for building management, operation and maintenance.

The verification of moisture in building envelopes has traditionally been carried out by testing procedures where one quantitatively determines the moisture content of the building component. Most methods have the drawback that it may take several days before the result is known. For some materials, these methods are also destructive testing procedures. Here is presented a qulitative testing procedure using thermographic methods. In buildings subjected to moisture damage, inspections have been carried out using JR-techniques. It has been investigated whether moisture damages can be detected from the interior as well as from the exterior of the buildings, whether previously verified moisture damages can be detected, whether JR-techniques can locate moisture damages other than those already detected, whether the extension of the damage can be estimated by JR-techniques, and to what extent the thermal image can explain the cause of a damage. Also, a cost comparison has been made, and operational conditions have been compared. It is concluded that JR-techniques provide an efficient way of detecting, verifying and evaluating moisture damages at a low cost.

In Denmark IR-techniques have found a widespend use in the Building and Construction sector. The applications include control of insulation level of buildings, district heating networks, transformer stations, electrical networks and water pipes in buildings, electrically heated floors, etc. In this paper is first described the Danish voluntary system for inspection of building insulation. This work is supervised by a government agency. Some examples are given on how these activities are carried out in practice. An important question is how to develop IR-techniques for new applications and how to transfer this knowledge for practical use. In this paper we describe how activities of this kind are carried out in cooperation with government bodies, research organizations and users of thermography. Important aspects discussed include the initialization of development projects, the financial aspects, the organization of projects of this kind and the technology transfer. Some examples are given from work of this kind.

Infrared thermography has been used by the Swedish National Testing Institute since 1968. The Institute has invesfigated the feasibility and reliability of using IR cameras for inspecting the thermal performance of buildings, and has contributed to drafting of Swedish and international standards applicable to the thermography of buildings. It has also been involved in the development and supervision of the Swedish scheme for authorization of test agencies (acredited laboratories) undeitaking building thermography work

Post-processing of infrared thermal image thta is a technique which finds many uses in a laboratory devoted to non-destructhe evaluation (NDE) of materials. Among these are determination ofmaterial pmperty values and detection/location of delaminations. Exanples are shown in which thermal diffusivity is measured for technique verification, as a verification of the tensor nature of diffusivity measurements and as a proxy for porosity in a test sample of a material under developmenL Another example is given in which the coefficient of thennal expansion is determined through the phenomenon of thermoelasticity. A final example is given in which post-processing extrts the thermal signature of a delamination from an image dominated by an unwanted feature. Following these examples of materials evaluation using post-processing, a set of procedures common to the data analysis in the examples is extracted. Generic requirements are given so that each procedure can operate consistently within the entire process to produce appropriate values of the material characteristics sought.

The objective of the present project is to develop improved thermographic techniques for the detection of subsurface flaws and disbonds in various aerospace materials. The scope of the effort to be presented in this paper includes the following: (1) the development of digital thermographic imaging capabilities, (2) the comparison of thermographic experimental results with models, and (3) the demonstration of thermographic methodologies to detect defects in composite materials. Based on the material to be presented it will be demonstrated that digital infrared thermography has useful applications for flaw detection in composites and potential applicability for detection of metallic corrosion under paint.

A numerical model was used to simulate the thermal response of a specific sample of graphite epoxy composite while excitation was provided by a specific, commercially available high-energy pulsed xenon flash lamp capable of repetitive pulses of 600 J each. A three-dimensional mathematical model was developed using polar coordinates to simulate the composite panel with implanted circular defects. The panel consisted of eight plies, and simulated defects included overlaps (added plies) and missing plies. During the first second of the simulation, six heat pulses of 0.2 msec duration were applied to the front surface of the sample. Temperature variations appeared on the rear surface of the sample due to the presence of defects within the thickness of the panel, which cause heat to diffuse through the panel at varied rates. Comparison with numerically generated test data was provided by an infrared thermal imaging system. While absolute temperatures and surface temperature gradients do not exactly match test data, general trends are apparent and overall correlation with test data is reasonable.

A method is proposed for the automatic inspection of jet engine turbine blades using transient infrared thermography. The blades are thermally stimulated using internal flow (water) at different temperatures. By looking on the pressure (or suction) side of the blade, it is possible to detect and locate blocked cooling passages. Differential time-resolved image analysis methods are shown to effectively improve the visibility of obstruction defects in the presence of strong temperature fluctuations across the blade. Examples of such analyse are presented.

This paper describes the basic methodology used to develop a radionietric model to verify that a plastic coating skip can be detected on an aluminum web substrate. Experimental results confirmed that the model is accurate in predicting the radiation contrast between the coated and uncoated aluminum.

A case history is presented in which infrared imaging is used to locate shorts in a complex printed wiring board. Passing current through the short heats the conductor trace, and the current path is delineated on the IR image. This method is shown to be useful for a variety of current-carrying structures, both for failure analysis and reverse engineering. It can often be used with very limited knowledge of the detailed function of the device.

Development of thermophysical approach to the solution of thermal nondestructive testing has led to the so called 'dynamic thermal tomography" which allows to picturize the in-deep distribution of thermophysical properties including defects' description. Some aspects of the thermal tomography are discussed.

Until recently, very few choices were available to a hot-strip mill operator desiringinfrared scanning. Measurements were often made using either portable non linescanning/imaging systems or slow linescanners originally designed for cement applications.3 Since then, important changes have taken place and the summer/fall of 1989 saw the introduction of no less than four different opto-mechanical linescanners as well as the increasing use at high object temperatures of various near-IR (CCD) linear-arrays in lieu of more traditional (mid) IR scanners. In comparison to earlier systems most, if not all, scanners provided higher spatial resolution (typically 2000 IR-points per line), higher scanning rate (typically20 - 100 Hz) and drastically improved measurement accuracy (at least for the opto-mechanical scanners, see below). This article will outline some of the results obtained in a typical steel mill environment with one of the highperformance linescanners of the new breed, and comments will be made on the emerging CCD-technology. For those interested in other line scanning applications with different object characteristics and surface temperature, some indications will also be given of the possibility to project the results obtained on other usages.

A method to automatically detect areas on coated aluminum sheet that were left uncoated due to a process malfunction has been developed. Detection sensitivity approaches a 1/4-inch diameter bare spot on the aluminum sheet moving up to 1,000 ft/mm The coated aluminum sheet exits a curing oven at temperatures near 410°F. At this point in the process, any bare spots on the aluminum sheet have an approximate emissivity of 0.10. The coating increases the emissivity by 0.15 to 0.75 depending on type and thickness. Since the bare sheet has a lower emissivity, a coating skip will produce a sudden drop in radiated energy (apparent temperature) . The magnitude of the drop depends upon the coating skip size, the coating thickness, the sensor spot size and the sensor response speed. A scanning thermal sensor and signal processor collects line scan information. A baseline following threshold is used to detect anomalous incidents. These incidents are tracked from scan to scan in order to define a complete defect. Paint skip size, severity and location (both downweb and crossweb) can be reported.

A method of determining an infrared sensor for automated inspection of hot metal sheet is described. The sensor locates voids, inclusions, and surface defects characterized by a variation from background radiant flux. The sensor can be coupled with a commercially available processing system, developed for visible wavelength line scan cameras, to automatically track, classify and report product flaws in real time. Theory: For hot metals, emissivity is strongly dependent upon surface conditions. Any scratch on the material will radiatemore strongly than smooth regions due to multiple reflections between the sides of the indentation. Changes in emissivity are also observed where surface blemishes occur, with darker regions emitting more than lighter areas. In addition, any void or inclusion within the metal may result in conduction properties different from metal of homogeneous composition. If these flaws are near enough to the surface, they will alter the radiance in localized regions. Approach: To detect signal modulations of a few percent in areas as small as a scratch, a high resolution infrared scanner is required. In some hot metal sheet production facilities, the web width can range from three to seven feet while the line speed can exceed 1,000 ft/mm. In order to achieve 100% coverage under these conditions, the inspection system requires both a fast response sensor and rapid signal processing capability. Currently, there exists at least one commercially available image processing system capable of tracking and reporting surface anomalies in real time. Here we present a method for specifying a sensor based on properties of the target material, environmental considerations, and commercially available infrared detectors.

In 1975 the concept of visualizing, measuring and studying the thermal condition of welded seams was investigated by a laboratory of the French ministry of defense (at the request of a metal constructor). Gilbert Gaussorgues, the founding father of the company HGH was at the time in charge of the infrared laboratory in question, a department of the general administration of Armament in Toulon, France. His idea was to apply military IR-Technology to above mentioned welding application. Having developed a prototype, tests readily confirmed the validity of using IR-emission from the weld seam close to the actual moment of welding as an indicator of the quality of the fmal assembly. Nearly ten years later, in 1984, HGH decided, due to an increasing demand, to develop above preliminary tests to a complete product/application package designed specifically for welding process-control. The inspection oftubing and of the integrity welds of barrels with hazardous content, were the first applications.

Thermal stress of an integrated circuit (IC) has a direct effect on the reliability of the computer system. Cray Research, Inc., designer and manufacturer of large scale general purpose supercomputers, is currenfly screening all Cray Y-MP modules for thermal stress to increase the reliability of this product. The requirements for thermal screening in our production environment consisted of minimizing cost, decreasing production time and maintenance, and providing a testing procedure that would not require using highly trained personneL The commercially available equipment evaluated did not meet all of these criteria. The infrared (IR) scanning tester developed by Cray Research provides accurate measurements of IC case temperatures and automated analysis capabilities with a minimum of operator intervention or evaluation. The tester employs an Inframetrics Model 600 IR Imaging Radiometer that is controlled by a personal computer system and can be operated with a minimal amount of training by any production worker. The computer also controls and monitors various tester functions such as cycling the power supplies and monitoring the current draw of the module. The IR scanning capabilities provided by this system have been an invaluable tool in the production process. The JR scanning tester has also been useful for performing various thermal experiments throughout the company, as well as providing a thermal record of each Cray YMP module produced. This paper describes the design and operation of the IR scanning tester and provides algorithms for remote operation of an Inframetrics Model 600 JR Imaging Radiometer.

Implementing a new experimental aerodynamic technique, a long electrically heated wire was placed across flows with general velocity distributions (wakes, jets). By measuring the temperature distribution along the wire with an JR camera, the flow behavior was identified. Furthermore, it is suggested that by using Nusselt number correlations, the velocity distributions can be deduced. Comparing the results with predictions based on heat transfer correlations, it was found that the IR camera cannot accurately track high gradient temperature fields. A correction procedure is outlined to account for the errors found in the measured results.

In this paper, an attempt is made for the first time to study the heat capacity in n-channel inversion layers on mercury cadmium telluride under strong magnetic field for the more interesting case which occurs from the consideration of fourth order in effective mass theory and taking into account the interactions of the conduction, light-hole heavy-hole, and split-off bands, respectively. We have formulated the heat capacity without any approximations of strong of weak electric field limits. The heat capacity increses with Crier density and magnetic field in an oscillatory manner. The results in accordance with various models for both the limits have been shown for the purpose of comparison. The well known results for relatively wide gap materials have also been obtained as special oases of our generalized theoretical formulations. It is found that the theoretical predictions are in accordance with fourth order theory and a]so in quantitative agreement with the experimental observations as reported elsewhere.

A novel pyrometric technique is being developed in Electricite de France (EDF) for measuring the surface temperature of the moving blades of partial load steam turbines. This technique uses the photothermal effect to slightly (temporarily) modify the superficial temperature of the object. Theoretical considerations show that the measurement is proportionnal to successive derivatives of Planck's function. The point is that the measurement is thus made. insensitive to background radiation partially reflected to the detection system by the object itself. Moreover, the short duration of the operation (several microseconds) allows quick moving targets to be measured. We here use the method for monitoring the temperature of the moving blades of partial load steam turbines in EDF nuclear power plants. A rod-shaped probe using fiber optics is being built to take measurements in real conditions. Some laboratory preliminary results show effectiveness and good accuracy of the method. Further studies will permit the extension of this new method to many industrial problems where non-contact temperature measurements in adverse radiative conditions are required.

The Lewis Research Center is developing, under contract, a Spacelab (manned module in the Space Shuttle payload bay) qualified infrared imager for non-contact surface temperature measurement in the Surface Tension Driven Convection Experiment, a microgravity fluid physics experiment. A versatile design philosophy was used in order to provide other experimenters with essentially an "off the shelf" Shuttle qualified instrument, eliminating the duplication of the rigorous development and flight qualification processes. An Inframetrics Model 600 Scanning Infrared Radiometer is being modified to satisfy both experimental and flight requirements, while maintaining the basic performance parameters of the commercial instrument. The modifications include an efficient, low power closed cycle cryogenic cooler to cool the detector, a ruggedized scanner mechanism, 8 bit AID conversion, Mil-STD components (where possible), size and weight optimization, and the addition of a microprocessor to perform automatic gain control. Features such as detector spectral response, the addition of spectral filters, and target temperature ranges could easily be changed to make this instrument useful as both a qualitative and quantitative diagnostic tool for Spacelab microgravity experiments, in combustion and fluid physics.

A cascade approach to the definition of the MTF for a (linear) sampled imaging system is discussed. The peculiarity of the present model consists in the fact that it can yield both the aliasing band and the averaged modulation response of the sampling process alone. For a line-scan system, which is the case of a typical Infrared Scanning Radiometer, a practical criterion to assess whether the coupled sampling and imaging subsystems produce a combined system which is either imaging-dependent or sampling-dependent is proposed. The application to the AGEMA Thermovision 880 IR camera connected to the TIC 8000 A/D sampling board is also discussed. The necessity to characterize the performance of the system in terms of its spatial resolution is given by the need to resolve the surface distribution of Goertler vortices on a ramp model in hypersonic flow.

The use of infrared imaging equipment for surface temperature measurements requires the knowledge of parameters such as object emissivity, temperature of the object surroundings and atmospheric transmittivity. The last two parameters can be evaluated from the gray levels of a thermal reference put into the scene. Accurate identification of the pixels belonging to the thermal reference but not to the investigated objects or background has been so far performed by a human operator. Full automation of such a task is highly desirable in actual practice, especially in applications involving a large numbers of thermograms or sequences of them. This work presents a method for the automatic detection of a Ohman thermal reference in digitized thermograms. The thermographic applications of the procedure, including automatic measurements of surface temperature and thermal parameters, are also described.

An IR-absorbing tracer gas when viewed against a warm background with an infrared short wave-band camera appropriately filtered can be used for detecting and recording the air turbulence caused by objects in laminar air streams in cleanroom environments. Air flow turbulence patterns in wind tunnels and from product prototypes have also been sucessfully recorded.

One of the most crucial limitations of quantitative thermography is the fact that, besides true object temperature, many complicated factors are involved in the formation of thermographic image . In many applications, complete knowledge about uncertainties which make some contributions to apparent temperature of an object is usually not available and reasonable assumptions are necessary. In this study, a calibration method of quantitative thermographic image has been developed under the assumptions; 1) object is radiometrically gray, 2) optical pathway attenuation and ambient irradiance is negl igible, 3) imager response to incident radiation flux is linear. The proposed method was tested on the heating pattern study of microwave antenna which is applied to a tissue phantom and was found to provide accurate temperature map.

An infrared scanner which is good for visual inspection is not always suitable for image processing applications. Noise and artifacts which are inconspicuous in continuous video can become objectionable when a single frame is digitized, processed and displayed. Fortunately, image processing can often be used to reduce or eliminate the artifacts. Signal noise and video interference can be reduced by a spatial lowpass filter; the filter can be tuned to the interference frequency to eliminate it completely. Digitizing an interlaced scan of a rapidly-changing scene effectively superimposes two images at slightly different instants; this image can be split into two images with reduced spatial resolution but twice the time resolution. The use of an oscillating mirror for scanning can introduce a ragged appearance on edges in the scene; this artifact can be greatly reduced by a suitable filter design. If the images are to be used for quantitative temperature or radiance measurements, then care must be taken to ensure that the filter algorithms do not introduce any systematic bias or distortion and that they do not move significant peaks and edges in the image. It is shown that a linear filter is well-behaved in this sense provided that its impulse response is localized, even, and has unit area. A filter matched to the characteristics of a specific equipment configuration was designed, implemented, and tested on sample images from that equipment. Selected sample images are shown before and after processing.

We have developed a system which allows repetitive thermal events at frequencies as high as 2 kHz to be imaged without aliasing. A prototype unit, consisting of an unmodified scanning imaging radiometer (Inframetrics IR-600) , a PC-AT compatible microcomputer, and specially developed interface hardware and software, has been built and tested. The system functions as a video lock-in amplifier in that temperature components of the scene which vary at a preselected frequency are amplified, while other frequency components of the target temperature average out over time. Several applications of the system are discussed, including applications to engine research, nondestructive evaluation of materials, and feature extraction in high clutter environments. The tradeoffs between temporal resolution, spatial resolution, and image acquisition time are also examined.

We describe an infrared (IR) imaging system in which noise suppression and image enhancement occur as a result of real-time processing techniques, synchronized with active time-dependent heating of the target. The system consists of an JR video camera and a real time image processor under the control of a computer workstation, together with various time-dependent heat sources. The heat sources are used to launch pulsed or periodic thermal waves into the target, and the camera is used to record the thermal waves scattered back to the surface by sub-surface thermal features (cracks, coating substrate boundaries, inter-ply delaminations, etc.). The technique involves applying either a sequence of short (-S. 5 ms) heat pulses with relatively long time intervals between them, or a long train of square or sinusoidal heating pulses with frequencies of a few Hz to a few kHz. In the first (pulsed) case, the signal processor is operated as a pixel-by-pixel box-car averager with images being taken in several gated time windows after each pulse. After averaging over multiple pulses, and suitable arithmetic manipulation of the gated images, a resultant image with increased contrast and a considerably higher signal-to-noise ratio is obtained. The result is as if a quarter of a million box-car averagers (one for each pixel of the image) had processed the data. In the second (periodic heating) case, the system is operated as if it consisted of a similar number of vector lock-in amplifiers, again producing an improved signal-to-noise ratio. We show examples of sub-surface features in graphite-epoxy laminates and copper printed circuit traces embedded in polyimide.

Some large scientific organisations in the city of Tomsk, Siberia, USSR are involved into the researchings on the advanced IR sensing technology. They are Polytechnic Institute founded in 1896, Uriiversity of Tomsk founded in 1888, Institute of Atmosphere's Optics, Academy of Sciences arid Institute of Automatized Control Systems and Radio electronics. Main fields are as follows: 1) thermal (IR) nondestructive testing of materials, machines and systems; 2) optoelectronics; 3) laser optics, transmission of infrared through the atmosphere and investigation of energy distribution in laser beams. Researching equipment includes Western and Russian industrial thermovisers, lasers, personal computers, IR detectors etc and some borne-made devices and components. There are optical arid JR detectors Lndustry in Tomsk that allows i.e produce spheric and aspheric mirrors and lenses, JR filters, cadmium-mercury-teilur and indium anlymonide T1 receivers arid to develop the scanning and measuring devices on the base mentioned above. Seine projects to develop the specific Tomsk thermoviser so far have nOt come true so the main accent was made onto the computerized thermographic systems suitable for solution of particular scientific problems.

Hydrogen fires emit very little radiation in the visible band, indeed in daylight they are effectively invisible. This is a serious safety hazard particularly in the aerospace field where hydrogen is widely used as a rocket propellent. A practical imaging system has been developed to detect the non-visible radiation that these fires do give off. The emission spectrum,atmospheric transmission, background emission and reflection have been quantified under various conditions. This shows thermal wavelengths are well suited for this application. A low cost, uncooled, staring array TV compatible thermal imager has been optimised for this. The resultant image is 'punched through' to super-impose the flame on a bore-sighted visual TV image. Finally the integration of this equipment into the sophisticated C.C.T.V. observation system on the N.A.S.A. space shuttle launch pad is discussed.