Infrared analysers for measuring the composition of simple flowing gas streams on chemical plant have been available for more than 40 years. For almost as long, infrared spectrometers have been used in research laboratories to measure the composition of complex liquid and solid samples. Instrument performance has been improved, new sampling methods have been devised and mathematical procedures developed whereby measurements can now be made in plant laboratories by plant operators on complex gas and condensed phase products with sufficient precision zor specification testing and sufficient speed to permit composition trends to be followed. Recently, IR probes have been developed which permit remote measurements on liquids inside chemical plant vessels, and these sensors may well produce information of sufficient quality to permit real plant control. It is the object of this paper to follow these developments and assess the present position.

No abstract available.

Infrared gas analysis has been in use as an industrial process for decades. Normally the gas is sampled from the stack and conveyed to an analyser system. As this requires the gas to be extracted, filtered and cooled to remove condensates, other methods have been developed. These include across-stack gas analysis where an infrared transmitter is placed on one side of the stack and a receiver on the other side. As there is now no need to remove gas from the stack, there are advantages of simplicity and avoidance of loss of soluble gases with the condensate. However, it is not possible to do span and zero tests with the across-stack gas analyser as the measuring path is open. A method which combines the advantages of across-stack and extractive gas analysis is the in-situ gas analyser. In this instrument, a probe is in the stack which fills with stack gas because it is made out of a porous material. This probe has an infrared beam of suitable wavelengths inside. The high quality rigid path compensates for the fact that it is a shorter path than the across-stack gas analyser. The overriding advantage is that zero and span gases can be introduced as they can flush out the porous sampling tube. However, all the advantages of non-sampling are maintained and this method allows the accurate analysis of soluble gases such as NO2, SO2 and NH3.

At the current time there have been few studies on the fundamental changes in polymer chemistry which occur when a thermoplastic undergoes a welding cycle. The techniques described in this paper have been developed to study such changes. The experimental metho4s, using the bands at l894cm and 13O3cm for polyethylene and 998cm and 973cm for polypropylene, have been evaluated using parent materials, and were found to be sufficiently reproducible and accurate to distinguish small changes in crystallinity (polyethylene) and helical content (polypropylene) in weld areas.

When using a dispersive infrared spectrometer it is quite normal to wait 10 minutes or more for the presentation of a spectrum of ones sample. A routine is generally established where the next sample is prepared during this waiting period. Spectra produced by an FT-IR spectrometer is often available in under a minute hence the bottleneck has moved from the spectrometer to the sample preparation procedure. Such a shift in emphasis has resulted in more pressure being applied to accessory manufacturers to reduce sample preparation time or eliminate it completely.

The possibility to measure IR spectra of polymer melts open up new perspectives for process monitoring and control in polymer manufacture and processing. Precise information on product quality can be obtained rapidly. Furthermore, it is also possible to make measurements on unstable intermediate materials. Although spectroscopy on melts is considerably different from that on solid state, but this does not limit the information content. There exists a wide range of possible applications.

Two Hadamard transform instruments designed for the 1990's using a fixed Hadamard encodement mask are presented. One is a dispersive spectrometer for doing near-infrared (NIR) Hadamard transform Raman spectrometry. The other is a stationary interferometer for doing visible (VIS) and near-infrared (NIR) emission and absorption spectrometry. The encodement mask displays the Hadamard encodement generated by external command - in this case, a computer. In the dispersive spectrometer the encodement determines specific spectral resolution element combinations that are allowed to impinge upon the single detector. The irradiance for each such combination is measured at the single detector and the Hadamard transform of this data set represents the irradiance (i.e. intensity) of each spectral resolution element. The complete collection of these intensities compares favorably to the spectrum collected on a conventional dispersive spectrometer. The stationary interferometer uses a fixed encodement mask and appropriate optics to allow specific combinations of sections (i.e. spatial resolution elements) of the spatial interferogram to impinge on a single detector. The irradiance for each such combination is measured at the single detector and the Hadamard transform of this data set represents the irradiance (i.e. intensity) of each section (i.e. spatial resolution element) of the spatial interferogram. The advantage of encoding the spatial interferogram from the stationary interferometer is the ability to use the single fixed detector rather than an array of many fixed detectors or a single moving detector. Some general advantages of Hadamard transform instruments are: (1) multiplexing the signal to one detector (2) no continuously moving parts allow frequency precision and good spectral subtraction (3) reasonably high optical etendue' or throughput (4) selective elimination of certain areas of the spectra and the rejection of Rayleighline in Raman experiments

Near Infrared Reflectance (NIR) spectroscopy has now been in use within Glaxo for over 5 years as a tool to provide rapid analysis. Analyses are sufficiently robust to be performed alongside the manufacturing process by non-technical staff. This paper describes the strategies employed within Claxo to provide both classification information and quantitative or semi-quantitative data relevant to manufacturing processes using a combination of chemometric techniques and NIR spectroscopy's sampling advantages.

Photothermal techniques use optically induced heat fluxes to probe the optical and thermal properties of materials. The techniques can be used for spectroscopy, measurement of thermal parameters, non-destructive evaluation, energy transfer studies and spectroscopic depth profiling. A large literature on the various photothermal techniques and their applications now exists, and several books are available giving a good overview of various aspects of the subject (cf Bibliography).

This paper briefly discusses the detector technologies suitable for incorporation into large two dimensional infrared arrays. The discussion is limited to technologies that are, or might become, compatible with silicon processing. This approach is seen as the best way to produce large area arrays in sufficient quantities and at a low enough cost to allow widespread use of infrared systems. Some aspects of the components that go to make up the subsystem are discussed, such as cooling engines.

Uncooled detectors of infra-red radiation exploiting the pyroelectric effect have considerable potential for thermal imaging applications when used in 1-D and 2-D arrays. This paper discusses the factors controlling the performances of such arrays. Lead scandium tantalate is a new ferroelectric ceramic which gives a very high figure-of-meriL The properties of this material are reported and compared and contrasted with those of other ferroelectric ceramics. The possibilities for direct fabrication of thin films of the materials are discussed. Linear arrays of detectors with D*'s of up to 5x108 cmHzlaW' and 2-dimensional arrays (up to lOOxlOO) with NETD's below 0.2K (25Hz,f/i) have been developed. The technologies for processing these arrays, including the use of reticulation for thermal MTF and microphony improvement, are discussed.

Focal plane arrays using ferroelectric ceramics have shown considerable success for ambient temperature IR imaging. To realise their full potential, however, the arrays must be reticulated, ie. the individual detector elements must be physically separated. In the research reported here, the use of focused argon-ion laser radiation to etch lead-compound ferroelectric ceramics in aqueous KOH is demonstrated. The experimental conditions required to laser-etch the desired structures for detector elements are discussed. Finally, the use of a reflective metal layer as an etch stop is assessed and laser-reticulated elements at 1 00 microns pitch are shown.

We have developed a low dark current, low noise 256 x 256 focal plane array (FPA) for a second generation instrument for the Hubble Space Telescope. The instrument is called NICMOS (Near Infrared Camera Multi-Object Spectrometer) and will have seven 256 x 256 FPAs for different scientific purposes. It is being developed by the University of Arizona and its subcontractors. This retrofit will be installed into the 1-1ST in about five years using the Space Shuttle. The final FPA flight units will be fabricated by our Electro-Optics division. This device is presently the world's largest and most sensitive FPA in waveband of 1.0 -2.5 jim. It is already being successfully used by ground based astronomers.

There are determined distributions of electric field of the light wave, the radiation intensity, the external quantum yield and the carrier concentration in a photosensitive element located in the optical resonanse cavity. The results obtained are used to evaluate the normalized detectivity of the (Hg,Zn)Te photon detector of lO.6piu radiation (PC, PEM and Dember). . It has been found, that the interference effects in a homogeneous with respect to the energy gap and doping, photosensitive element, results in the increase of the detective parameters of the detectors (up to 3 times). It can be obtained the high normalized detectivity * 8 1 1/2 (D >10 cmW Hz ) of uncooled (T300K) and cooled (T200K, D>lO9cmW1Hz1"2) photoresistors, PEM and Dember detectors with the optical cavity.

Lucas Aerospace. Engine Systems Division, has been involved with small mechanical cryocoolers since 1978, the initial work carried out between 1978 and 1984, comprised an evaluation of the various cooling cycle options available to cool military Infra Red Detectors in the 80K to 90K temperature range together with initial build and testing of early prototype units of the chosen Reverse Split Stirling Cycle machines (See FIG 3). These initial protypes and the subsequent modified designs produced between 1984 and 1986 were based on work carried out at Oxford University by Dr Gordon Davey and Dr Anna Orlowska, who both acted as consultants to Lucas Aerospace. It was felt that this design of cryocooler with its non-contacting seals and absence of any bearings or lubrication of any kind, offered the best solution for a lông life cooler. This design has been developed by Lucas Aerospace over the past 6 years, initially for Military (Avionics) applications and more recently for space applications. The change in emphasis to space applications came about in 1988 when Lucas Aerospace signed an agreement with Lockheed Missile and Space Company (LMSC) of Palo Alto, California to jointly develop a range of Cryocoolers for Space Applications. It was recognised by Lockheed that whilst they had a considerable capability with space rated Solid Cryogen coolers built up over many years experience in space, with the current trend for longer duration space missions of between 5 and 10 years, these coolers would carry very large weight and size penalties in meeting these requirements. Lockheed felt that the best option for these long life space missions, for cooling the various infra-red detectors in the 55K to 80K temperature range, was the small mechanical cryocooler being developed by Lucas Aerospace. This joint development programme is proceeding apace with three Cryocoolers being delivered to Lockheed for performance and vibration testing.

There are numerous requirements for inexpensive TV imaging systems to cover the near infra red spectrum out to 2000nm. Applications include covert surveillance, semiconductor inspection, laser and thermal imaging. At the heart of such a system is the image pick-up device: usually in the form of a vacuum tube of the Vidicon type or a solid state sensor array. Unfortunately there are very few photoemissive or photoconductive materials that can be employed as sensors for cameras across the 1000-2000nm band. Image tubes using the Si (Ag/O/Cs) photocathode work to i500nm but have poor sensitivity. Most silicon devices in the form of Vidicon targets or CCDs are not sensitive beyond iiOOnm. Only the PtSi Shottky barrier imagers cover this spectrum, but they are expensive and require cooling to reduce dark currents to tolerable levels. For over 50 years lead suiphide has been used to detect near infra red raaiation to its limit of 3300nm, but because of its low resistivity (iO iO ohm-cm) it cannot store charge information long enough to be useful a3 an imaging material. On the other hand lead oxide has a resistivity (iO ohm-cm) high enough for imaging but its long wavelength detection limit is only 650nm. In i949 Frank and Raithel (i) compromised by combining PbO and PbS in the hope of making a more viable IR photoconductive target. Their method was to evaporate first a PbO film and then subject it to sulphur vapour at elevated temperature followed by further heat treatments. Although the spectral response they obtained extended from the visible to about i800nm the sensitivity was non uniform, dark currents were high and the Image retention was severe. Later work by Heimann and Kunze (2) and Hon et. al. (3) claimed to improve the transient response or lag, but picture qualities still were deemed to be very poor. More recent developments by Kawai et.al. (4) extended the spectral limit of their Vidicon to 2700nm by using a very lengthy version of the original Frank and Raithel process. There remained however many practical problems concerned with reproducibility in the production process and the stability of target and tube performance. R Registered Trade Mark of EEV Co. for photoconductive camera tubes with lead oxide targets.

An experimental prototype of new generation infra-'red devices has been realized. Sensitive in the 8 to 10 microns wavelength band, its design coithines electronical scanning in the horizontal direction (1,024 eleraent IR Charge Transfer Device Focal Plane Array) and a simple opto-mechanical scanning in the vertical direc- tion (only one frame mirror). Images are displayed in the framework of present TV standard. Thanks to its large versatility, such a design is able to cope with any image requirement (interlaced or not, HDTV, . . . ) by electroni- cal control. Ranges are typically improved by j2 with respect to those of today high performance FLIRs.

We manufacture thin-film Ni-NiO-Ni diodes for the detection of 10 p,m CO-laser radiation with the aid of electron and UV lithography and sputtering techniques. The minimum dimensions are 0.4 tm. The thickness of the oxide layers is of the order of 50 A. According to theory, the response of MOM diodes to infrared radiation should be proportional to the second derivative d21/dV2 of dc I-V characteristics of these diodes. However, part of the response of the MOM diodes originates in the thermal heating by the infrared radiation. Consequently, we have measured the dc I-V characteristics as well as the response to cw 10 .tm-CO2-laser radiation of Ni-NiO-Ni diodes at room temperature for different orientations of the diodes with respect to the incident laser radiation and its polarisation. For Ni-NiO-Ni diodes we have observed a cosine dependence of the signal on the angle of the polarisation versus the antenna which represents the proper non-thermal nonlinear response of the diode. At the moment, the coupling factor is of the order of 70. The MOM diodes and their thin-film metal-strip antennas are attached to Si wafers. The high refractive index of bulk Si at 10 tm wavelength diminishes thç coupling of the 10 p.m laser radiation to the MOM-diode by the attached thin-film metal strip antenna. Therefore, we reduce the thickness of the Si wafer on the back of the MOM diodes and their antennas to about 5p.m by etching. Thus, we increase the transmission of the Si wafer under the metal-strip antenna and improve the antenna performance. Furthermore, we try to increase the sensitivity of the diodes by further reduction of their minimum dimensions, which can be achieved by direct writing with the electron beam of the electron-beamlithography facility at Centre Suisse d'Electronique et de Microtechnique, Neuchâtel, Switzerland.

The systems described in this presentation relate to new forms of television camera assemblies in which arrays of sensors may be preselected to detect' scenes emitting or reflecting infrared rays or visible light or other wave forms including ultrasonic waves. In the first of the basic forms of arrangements, each element of an array of sensors or transducers is connected to a corresponding element of a second array comprising photosensors. The second array of photosensors is scanned by light originating from a light scanner or cathode ray tube to connect elements of the array of sensors or transducers to output terminals in sequence. A second form of arrangement involves the application of 'sequential electro-optical systems' comprising 'feedback photoconverters' for scanning by connecting elements of arrays of sensors or transducersto output terminals in sequence. The assemblies described form parts of the author/presenter's inventive projects as previously described and featured in specifications including U K Patent Specification Number 1 477 730 and in summaries of "G 0 Okikiolu - Bulletin of Inventions and Summary

Commercial thermography started around 30 years ago as a spin-off from military development in the area of thermal weapon-sights. In the early days of thermography many applications were discovered. Actually most of todays applications were identified already during the first years. The development of the applications were, however, in most cases hampered by limitations in available technology. During the last 10 years thermography has benefitted greatly from the general development of technology in particularly the following areas: - infrared detectors - digital electronics - computer technology - computer software - storage media The development in these areas have enabled the suppliers of thermographic equipment to develop systems that meet the application requirements. The technology development and the associated volume growth has also brought down the cost of thermographic equipment considerably since the early days of thermography. The other major driving force in the development of commercial thermography besides the technology development is the emphasis on quality and productivity in todays industry.

Pulse-video thermographic images of well characterised sub-surface defects have been examined in detail using an image analyser. The dependence of the transient response on defect size and depth beneath the surface has been established empirically and investigated analytically. Close parallels are drawn with earlier observed thermal wave effects. The work provides an indication of the basic sensitivity of this transient thermal inspection technique.

Reflective cavity pyrometers are increasingly used for on-line temperature sensing of metal sheets. The presence of the reflector increases the effective emissivity of the sheet, thus reducing the measurement error. Hemispherical geometries have been mostly used in the past for the reflector. This paper presents a Monte-Carlo analysis for a number of different cavity configurations. The value of the effective emissivity is evaluated for different cavity parameters and standoff range over the sheet as well as for different degrees of the metal sheet real emissivity. It will be shown, in particular, that a trucated hemisphere with centre of curvature belowthe sheet is preferable to the more conventional full hemisphere to reduce losses due to sheet fluttering. Applications to infurnace temperature monitoring of steel sheets will be indicated.

of Patent Specifications"Ground-based thermography is used to examine items of plant in power stations and substations and several examples of faults found are illustrated and discussed. Helicopter borne high resolution thermal imagers are used to monitor the transmission system, and the results, together with the constraints, are illustrated and discussed..

Temperature patterns on the skin surface, visualized by infra-red thermography produce much useful medical and physiological information in both health and disease. Medical thermographic systems are regularly used in many countries in oncological, rheumatological, neurological, and vascular pathologies. However, although many medical uses of thermography are not contentious, some fmdings seem contrary to accepted mechanisms and theories. This paper describes the range ofpathologies where thermography has a clear role and discuss some ofthe issues that still have to be darified in the interpretation ofthermal images from human skin, particularly in relation to superficial blood flow and skin metabolism.

CEDIP 13S has designed the RTIS 8902 under license of ONERA, a Pc compatible system for the digital recording of infrared images in real time and over a large dynamic of digitization (12 bits). The RTIS 8902 operates with AGEMA cameras, an extension to JI1FRAMETRICS camera is currently under development The unit is able to store to hard disk evezy infrared image from a single camera or a dual camera, the maximum storage time is related to the hard disk capacity and is about 10 minutes for a 600 MBytes hard disic Several applications for the RTIS 8902 have already been developed among whose infrared signature analysis, combustion analysis and nondestructive testing of matezials. The present paper describes a commercially available equipment, the PTR 9000, developped and build with the RTLS 8902 unit, and dedicated to the NDT of materials.

The radiative properties of surfaces with various oxide layers have been measured. Total emissivities are greater than those of clean specimens, and tend to increase with the thickness of the oxide layer. The influence of the layer depends on its structure and chemical composition.

An AGEMA 870 thermal imaging system has been used to measure the temperature of a film cooled panel in a hot duct, ventilated by flowing air at atmospheric pressure. To avoid detecting radiation from these gases, it proved necessary to view the panel through a narrow bandpass filter centred on 3.95im. The thermography results failed to agree with spot thermocouple measurements until changes were made to both the experimental and calculation procedures. The paper describes these changes and the calculation algorithms used to calibrate the system, account for non-uniform ambient radiation and eliminate the distortion produced by the wide angle lens.

Over the past few years infrared thermal imaging has been considered for a variety of engineering applications and the potential of this method is only now being realised with the range of applications still increasing (1 and 2). As a totally non-destructive method, it has the advantage of providing handsoff mformation quickly. As with other non-destructive or potentially destructive methods, however, there are particular factors which may influence the success of its application and, wherever possible, it should be used in the context of a combined testing approach (3). Because of the relative nature of data produced by a thermographic survey, the quantification of properties of a structure or the materials contained therein may require correlation by confirmatory localised 'destructive' sampling and/or inspection. This paper outlines the principles in operation, the conditions required for the survey to be successful and a range of situations where the technique has proved effective.

Photothermal thermography is a nondestructive technique for the analysis and testing of materials which associates the excitation of the tested parts by a flash with the detection of the induced temperature increase, thanks to an infrared thermography camera. We present here an apparatus called MECIR, which results from a several year long collaboration between both a research laboratory of the University of Reims and an outstanding civilian and military aircraft constructor. It includes an AGEMA infrared camera, a specially conceived system for the image capture and the treatment of data, as well as an illuminator composed of four Xenon flash tubes. The apparatus is to be used for the rapid testing of rather flat and large parts. We show the results of defect controls in objects made of composite materials and used in the aeronautic industry. (*) The development of MECIR is being sponsored by the French Ministry for Research and Technology.

The technology of aerial IR surveying for camercial purposes has improved significantly lately by the transfer of military technology to this activity. Sprite technology and sophisticated image enhancement techniques have been imaginatively applied to a wide range of caxerical survey applications not previously possible. The purpose of this paper is to describe some of these and thereby to stimulate the use of the equipment in new applications.

Under certain controlled conditions it is now possible to machine brittle materials such as glasses and ceramics using single or multi-point diamond tools (grinding), so that material is removed by plastic flow, leaving crack-free surfaces. This process is called 'shear' or 'ductile' mode grinding. It represents a major breakthrough in modern manufacturing engineering since it promises to enable: - complex optical components, both transmission and reflecting to be generated by advanced CNC machines with very little (or even zero) subsequent polishing. - complex shaped components such as turbine blades, nozzle guide vanes, etc. to be finish machined after near net shape forming, to high precision in advanced ceramics such as silicon nitride, without inducing micro-cracking and thus lowering ultimate rupture strength and fatigue life. Ductile mode "damage free" grinding occurs when the volume of materials stressed by each grit of the grinding wheel is small enough to yield rather than exhibit brittle fracture, i.e. cracking. In practice, this means maintaining the undeformed chip thickness to below the ductile-brittle transition value; this varies from material to material but is generally in the order of 0.1 pm or 100 nm, (hence the term "nanogrinding" is sometimes used) . Thus the critical factors for operating successfully in the ductile regime are machine system accuracy and dynamic stiffness between each grit and the workpiece. In detail this means: (i) High precision 'truing' of the diamond grits, together with dressing of the wheel bond to ensure adequate ' openness'; (ii) Design and build of the grinding wheel spindle with very high dynamic stiffness; error motions, radial and axial, must be considerably less than 100 nfl. (iii) Design and build of the workpiece carriage motion system with very high dynamic stiffness; error motions, linear or rotary, must be well within 100 nm. (iv) Smooth, rumble-free, high-stiffness servo-drives controlling the motions which form the chip. In general, and as a rule of thumb, a machine "loop-stiffness" (between tool and workpiece) not less than 300 N,4im (static) is necessary.

Both low bonding strength and high density of active grains are iiportant features for carrying out daiage-free grinding. Hoiogeneous ultrafine abrasive pellets were developed by applying electrophoretic deposition. Face grinding of brittle saterials using the pellets enabled creation of a supersiooth surface finish less than lOni peak to valley with no cutting iarks. Moreover, chippingfree grooving was accoiplished using a thin conductive blade on which ultrafine abrasive layer was grown under an electric field.

This paper describes a study of single point natural diamond machining techniques applied to machining flats, spherics and aspherics. It begins by examining four critical features of the diamond machining process that must be understood and applied before flats, spherics and aspherics can be diamond machined. The four critical features are as follows:- The unique physical properties of natural diamond that make it the ideal material for micro precision machining. The high quality machine design principles that must be applied to obtain optical surfaces and form. The design features of component fixturing for successful production of metal optics. How the accuracy and form stability of precision diamond machined optical components depend on the choice of material and the quality of the blank.

The inprocess interferometric techniques employed at British Aerospace enable diamond turning tools to be centred to accuracies exceeding 10 microinches. In addition to Ogive error the interferograms ifiustrate higher order effects such as tool geometry, cuuer radius defects and wear. A detailed analysis of diamond tool geometries was carried out and used to evaluate the resultant form defects arising in components. This analysis was then used to develop software compensation which could eliminate the errors of tool geometry. Simulation results showed that for the negative tool rakes used to machine infrared materials, software compensation is essential. A simple tool wear model was devised on the basis of wear being directly proportional to distance travelled. This model was used to demonstrate the frequently observed phenomenon of extending a tools effective lifetime by adjusting X-centre. Machine trials are currently underway to measure the reproducibility of wear effects .This will determine the validity of our basic model and enable us to derive a more accurate solution.

The increasing use of diamond machining in the production of high quality optical components requires the production process to be as simple as possible to enable the use of unskilled labour. A process has been developed using interferometry and computer image analysis to automate the initial set up of the diamond tool relative to the machine axes. This process is aimed at eliminating the ogive error caused by tool decentre sometimes found in diamond machined components.

The manufacture of reflecting components for optical systems by precision diamond machining is well established. Diamond machining is a process in which the tool is a diamond, and the finish produced by the diamond is usually the final finish. Much work has been carried out on the improvement of the stiffness of machines, both lathes and fly-cutting machines, reduction of vibration and the sharpness and shape of the diamond tool. With components of complex curvature the only economic way these can be manufactured is by diamond machining. In many cases low inertia is required and this means that mirrors must be made from a lightweight material such as an aluminium alloy. The machining can proceed at rates of up to a few inches per minute and so the production time can be quite short. It is shown that the surface finish can be limited not by the machining as such but by the presence of intermetallic inclusions. It is thought that these inclusions are inherited from the billet and are carried through to the extruded material. Surfaces machined from such material will produce diffuse scatter and loss of contrast when used in an optical system. The subject of this paper is the improvement of the aluminium alloy from which the reflective components are to be machined.

The drive for miniaturisation and higher precision across a widening range of manufacturing activities has placed increasing demands on industry for new capabilities for machining, positioning and control and measurement to nanometre tolerances; it has also called for improved understanding of materials and processes at the molecular level. The term Nanotechnology has been adopted to encompass technological activities across this broad spectrum and is defined as the technology of manufacture where dimensions or tolerances in the range 0.1 to 100 nanometres play a critical role. The UK's National Initiative on Nanotechnology (NION) was launched in 1986 to increase awareness of this emerging technology and to promote R&D in the field and to encourage its industrial exploitation. The initiative is supported by the LINK Nanotechnology Programme (LNP) which has an initial £7.5 million of government funding to support pre-competitive collaborative research in Nanotechnology. The paper will review the activities of NION, highlighting the policies, the key technologies and application areas, and will report the progress of the LNP.

The techniques for manufacturing blazed zone plates are summarised. The advantages and disadvantages of using zone plates to replace or complement conventional components is discussed and it is found that the applications for which they offer real advantages are relatively SpeCialiSed.

A recent paper by Hall examined two optical design studies in which aspheric surfaces were used to benefit the system. In the case of a Petzval lens system the material cost was reduced. In a Maksutov system the introduction of aspheric surfaces resulted in increased freedom of choice in terms of system length and cost. The examples chosen were unrelated and represented radically different problems. The designs were created heuristically. The design process used manually corrected seidel aberrations, followed by damped least squares optimisation. Being isolated problems, the study gave no insight into the general problem of aspheric optical design. The problem is complicated by the intractability of the algebra involved in obtaining general solutions from seidel theory. Because of the difficulty involved, there is also not much spherical design precedent on which to base a study of aspheric systems.

A folded dual magnification telescope, operating in the 8-12 micron waveband, has been designed to be incorporated in a pressure resistant housing sealed with a spherical profile pressure window. A single element is located immediately behind the window and is aspherised to control the aberrations generated by the window. An additional aspheric element is incorporated in a two lens turret which is switched in to provide low magnification. The trade-offs between control of aberrations, cold reflections and mechanical considerations are discussed together with details of tolerancing and manufacturing requiitments.

The design considerations and approach to developing a 5.5X afocal telescope to retrofit an existing prototype FLIR system that did not anticipate the inclusion of a telescope are presented. Besides having to meet certain mechanical limitations, the afocal telescope was designed to correct for residual aberrations in the FLIR optics rather than being more generic in nature. The optical performance of the FUR with and without the afocal telescope are compared. Fabrication issues and test results will be presented.

This paper reviewed the infrared uses of diamond-like carbon thin films and the potential uses of synthetic diamond layers. Diamond-like carbon is used widely as a protective anti-reflection coating for exposed germanium infrared windows and lenses and as thin protective coatings for front surface aluminium mirrors. This material is also used in protective anti-reflective coatings for zinc sulphide as the outer thin film in multi-layer designs incorporating variable index intermediate layers of germanium carbide. The maximum thickness of diamond-like carbon that can be used is often limited by the stress induced in the layer through the method of deposition and by the absorption present in the basic material. This stress and absorption can be far lower in synthetic diamond layers but there are now problems associated with the high substrate temperatures, difficulties in coating large areas uniformly and problems arising from surface scattering and low deposition rates.

With continually increasing demands for improvements to atmospheric and planetary remote-sensing instrumentation, for both high optical system performance and extended operational lifetimes, an investigation to assess the effects of prolonged exposure of the space environment to a series of infrared interference filters and optical materials was promoted on the NASA LDEF mission. (2) The NASA Long Duration Exposure Facility (LDEF) was launched by the Space Shuttle to transport various science and technology experiments both to and from space, providing investigators with the opportunity to study the effects of the space environment on materials and systems used in space-flight applications.4 Preliminary results to be discussed consist of transmission measurements obtained and processed from an infrared spectrophotometer both before (1983) and after (1990) exposure compared with unexposed control specimens, together with results of detailed microscopic and general visual examinations performed on the experiment. The principal lead telluride (PbTe) and zinc suiphide (ZnS) based multilayer filters selected for this preliminary investigation consist of : an 8-12 m low pass edge filter, a lO.6m 2.5% half bandwidth (HBW) double half-wave bandpass filter, and a 10% HBW triple half-wave bandpass filter at 15 jim. Optical substrates of MgF2 and KRS-5 (TlBrI) will also be discussed.

Two MRTD collimator systems have been developed for measuring the performance of FLIR's installed on aircraft, tanks and other vehicles. One of these is a general purpose equipment for performing a full assessment of an imager, whilst the other i s a hand portable test set for doing go/no-go checks on performance. The latter is also very suitable for production testing..

Many of the problems associated with Minimum Resolvable Temperature Difference (MRTD) testing arise from a generally unstable environment, which is especially so outdoors. This paper describes a novel thermal arrangement (subject to a patent application') in which the temperatures of a number of "Hot" MRTD bar patterns are referred to a "Cold" MRTD bar pattern in a way that overcomes the problems of an unstable environment and gives a quick "One-look" GO-NOGO test.

Two methods of making an objective measurement of MRTD have been under development. The techniques and some results obtained using two different types of thermal imager, are described and discussed with particular consideration given to the effect of the MTF of the eye. Conclusions are that objective measurement techniques can now seriously be considered as an alternative to subjective measurements for production testing.

The importance of image restoration is increasing with the widespread use of imaging systems in various sectors of modern technology. However, as far as the quantitative application of computerized Infrared Scanning Radiometers to the study of thermo-fluid--dynamic problems is concerned, it seems that the image restoration is not addressed in a satisfactory way by the currently available commercial systems. The aim of the present paper is to yield a contribution in this direction. While defining a degradation model, in particular, the effects (if any) due to digital sampling are also taken into account by means of a cascade model including both imaging and sampling effects. Two heat transfer applications (in presence of natural and forced convection) are discussed.

A facility is under development which largely automates the radiometric calibration of a pair of AGEMA Thermovision Series 780 radiometers or both channels of a dual waveband radiometer. The output of the radiometer is proportional to the photon flux incident on the detector. Calibration is performed by determining the relationship between the total radiant emittance of a black body and the electrical output of the detector. Measurements are made at a specified number of temperatures over the range 0 to 1000 °C and a least square method is used to determine the calibration constants. The radiometers, which are mounted on a motorised stage providing motion transverse to their principal optical axes, are positioned under the control of a computer so as to view one of two black body sources. The available video signal is dependent on range and level controls, and, to achieve full resolution and maximum accuracy, a mechanism is employed to adjust the level control automatically. The video signal is displayed on the computer screen for the purpose of alignment and for determining where the black bodies are located in the image. Once alignment and the initial setup has been completed, the process is put under the control of the computer. For each measurement point, the computer sets the black body controller and waits for the set temperature. After a specified delay to allow stabilisation, a predetermined number of video frames are averaged to determine the radiometric signal levels corresponding to the image of the black body. When measurements are complete, the data points are fitted to determine the calibration constants. Provision has also been made to accept digitised signals taken directly from the detector preamplifiers.

The importance of image restoration is increasing with the widespread use of imaging systems in various sectors of modern technology. However, as far as the quantitative application of computerized Infrared Scanning Radiometers to the study of thermo-fluid--dynamic problems is concerned, it seems that the image restoration is not addressed in a satisfactory way by the currently available commercial systems. The aim of the present paper is to yield a contribution in this direction. While defining a degradation model, in particular, the effects (if any) due to digital sampling are also taken into account by means of a cascade model including both imaging and sampling effects. Two heat transfer applications (in presence of natural and forced convection) are discussed.

We are developing a high-resolusion infrared interferometer applying 3.39 inn He-Ne laser.This interferorneter will be utilized in testing for infrared materials and optical systems in real time. In this paper,the outline of our interferometer and several applications of it are described.

No abstract available.

The application of Hadamard transform spectroscopy to production control problems and quality assurance is now possible. Presently the visible and near infrared region of the spectrum are readily accessible for the measurements. Additional spectral regions will be used as better Hadamard masking switch technology progress in the '90s. The Hadamard optics can be applied to dispersive spectrometers, stationary interferometers, and commercial instrumentation for infrared and Raman studies.

Concrete is not quite such a non-destructable material as many are led to believe. It can deteriorate with time due to changes in the chemistry, the effect of moisture penetration and the corrosion of reinforcing steel bars. Much of this damage occurs relatively close to the surface, sometimes revealed by discolourations or the presence of cracks and sometimes as spallation when the corrosion products of steel cause delamination of the near surface concrete. These effects may occur in good quality concrete but their severity and rapidity of onset may be enhanced by fabrication defects when aggregates may not be to specification or the packing conditions cause porosity. It may thus be months or even years afterwards that these defects come to light. As a consequence a new industry has been formed to inspect concrete structures which may include X-ray equipment, linac accelerators, gamma isotope sources, ultrasonics, radar and of course thermography. Each of these nethods will have their own particular attractive features and merits. But most of these activities tend to be used more as a "fire fighting" service than as one ensuring regular maintenance of critical structures or even as quality control of structures during building. Quite often it seems that Non-destructive Testing is turned into a litigation service for dissatisfied customers and thermography is no stranger to this topic. It is heartening to see that the ASTM organisation in the USA and British Standards are encouraging and developing suitable standards for the inspection of concrete by thermographic techniques.