Electron beam pattern generators are nowadays used extensively for the production of masks and for direct writing on wafers. For obvious reasons electron beam pattern genera-tors are optimized for integrated circuit fabrication. However there'is also considerable potential for the use of electron beam lithography in other areas. In this paper recent trends in the development of electron beam pattern generators are described and the problems encountered in the application of electron beam machines in other areas e.g. integrated optics are discussed.
Gas lasers have shown to be capable of delivering tens of terrawatt aspeak power or tens of kilowatt as average power. The efficiencies of most high power gas lasers are relatively high compared with other types of lasers. For instance molecular lasers, oscillating on low lying vibrational levels, and excimer lasers may have intrinsic efficiencies above 10%. The wavelengths of these gas lasers cover the range from the far infrared to the ultra-violet region, say from 12000 to 193 nm. The most important properties are the scalability, optical homogeneity of the excited medium, and the relatively low price per watt of output power. The disadvantages may be the large size of the systems and the relatively narrow line width with limited tunability compared with solid state systems producing the same peak power.
This presentation summarizes the infrared activities in the Netherlands during the past 30 years and indicates the directions for future work. The capabilities of infrared technology, being passive and useful for night vision applications were envisaged for a long time in our country. The dependence on the military market however made the progress slow, but this time was used properly by the research scientists to fully explore the problem areas.
Current developments in thermal imaging in the 8-12 micron waveband are towards improving spatial and radiometric resolution. However, they will not reduce the initial or whole life cost. To significantly reduce costs the overall size must be reduced and significant savings made in three critical areas; detectors, cooling and optics. 3-5 micron quantum detection using a parallel or serial parallel scan is investigated which reduces cost in these areas by using inherently cheaper detectors with thermo electric cooling and low cost optics optimised for diamond machining using a reflecting single field of view telescope.
The paper reviews pyroelectric vidicon work since the 1960's including crystal growth, target preparation and experimental tubes. The present state-of-the-art in thermal imaging vidicons and future possibilities are also discussed.
Focal Plane Arrays (FPA) of Cd Hg Te Detectors with responses in the 3-5 4μm or 8-14 4μm bands have been successfully incorporated into Infrared Imagers. Using a variety of digital signal processing techniques, good imagery has been obtained but the image quality is limited by sampling effects at the focal plane which cause non-isoplanatism and aliasing. Some initial modelling of these sampling effects and the way in which they affect the Modulation Transfer Function (MTF) have previously been reported(5). In this paper that modelling is extended to investigate, more fully, the non-isoplanatic nature of the system and in addition some MTF measurements are reported and compared with the results obtained from simulation. Some alternative methods of MTF measurement are being investigated and will be discussed.
The Size Invariant Processor is an electro-optic technique for discriminating between narrow band and polychromatic radiation in a natural background scene. This paper presents details of the systems principle of operation and of experiments carried out with a portable device, to determine its degree of discrimination against a natural background scene and to verify its source size independent discrimination.
Imaging sensors employing linear arrays of pyroelectric detectors have been built and demonstrated. Such sensors are suitable for "slow scan" applications in framing imagers. The impact of recent developments in detector technology are reviewed. Full T.V. rate solid state pyroelectric imaging sensors require the use of two dimensional arrays of detectors. A prototype sensor employing such a detector has been built and the performance achieved to date is described.
It is shown that by measuring the infrared image of a scene at two different points of time it is possible to calculate all local scene invariants. These results are used to predict the scene image at any other point of time using the heat balance equation. A good agreement with experimental results is obtained.
A calibrated imaging radiometer has been incorporated into a mobile measurement facility together with relevant meteorological sensors. Natural scene signature data has been collected over a period of time and used to form the basis of a scene temperature difference prediction model. The resulting model has been tested against "new" scenes, and the feasibility of a general model for the prediction of temperature differences in natural scenery as a function of meteorological history, has been studied.
Many infrared flame detectors are now available which detect the presence of a flame by sensing radiation at or near 4.3 microns in the middle infrared. However, the radiation spectrum produced in this wavelength band, largely due to the hot carbon dioxide produced in the flame, is modified in transmission through the atmosphere from the flame to the detector. A study of these changes has shown that they can be used to gauge the distance of the flame from the detector. Some preliminary results from a detector built to provide this type of information are reported and the advantages that the technique can provide in terms of fire detection systems are also considered.
An image processing computer is used to simulate the viewing of an aircraft by an observer using standard IR surveillance equipment. The technique enables specific and controlled target/background signatures based on either theoretical or practical measurements to be used in human factor experiments to measure aircraft detectability.
A brief theoretical description of graybody radiation laws is given. Distribution temperature is defined as the temperature for which the theoretical Planck radiation curve fits best the measured radiation curve of the real body. A numerical method for calculating the distribution temperature is described and discussed. Functional schemes and description of operating experimental device are presented. The main components of the device are 256-channel polychromator with fixed optical elements and a linear solid-state detector array, fast 8-bit A/D converter, I/O computer interface and computer. The device can take up to 80 samples of radiation spectra between 500 and 1100 nm with sampling speeds up to 473 spectra/second. The collected data are postprocessed with a powerful software package which allows calculations of distribution temperature, elimination of spectral lines before calculation, spectra smoothing and averaging, etc. It is not necessary to know the emissivity constant when calculating the distribution temperature. Calibration procedures necessary for such an instrument are defined and encountered problems are described. Experimental measurements of transient behaviour of tungsten-filament lamp during power-up conditions and temperature measurements of burning pyrotechnical mixtures are presented and described.
A new approach to the remote electro-optical detection of gases is presented. Radiation, of greater spectral width than an absorption line or series of lines, is analysed using an interferometer. Absorption strength is then deduced from features of the temporal coherence function. Theory and preliminary experiments are discussed.
A 64-element pyroelectric linear array detector has been developed. Included within the detector is a corresponding array of source followers together with a multiplexer and amplifier. High responsivity and high detectivity have been achieved together with a low level of microphony.
Pyroelectric detector arrays, linear and two dimensional, are of interest for many infrared applications. In this paper, a low-noise readout design using MOSFET arrays (LAMPAR) is proposed and analysed, and the noise performance presented. The design is being successfully implemented in several hybrid array programmes.
Good agreement has been found between theoretical models and measured performance for a range of array geometries. A 64 element 80 μm x 140 μm element array with integral MOSFET I.C. buffer pre-amplifiers shows improved source voltage uniformity c.f. a J-FET buffered array and low frequency D* of 1.7 X 108 cm/Hz/W at 40 Hz. The MOSFET array shows reduced degradation of D* at high temperatures, retaining a D* 1 x 108 cm,/Hz/V1 at + 700C across much of the band. A 64 element array has been designed using on-board multiplexers thus greatly reducing the connections needed to run the array.
A new thermal infrared detector fabricated using standard silicon IC technology and silicon micromachining is presented. The device consists of a 10-micron thick cantilever beam with one half covered by an absorbing layer and the other half containing a 44-strip p-Si/Al thermopile. The detectors have a responsivity (in vacuum) of 10 V/W and a relative detectivity D*, measured in air and for a 500 K blackbody source, of approximately 5 x 107 cmHzi/W.
The measurement of the magnification factor of infra-red or thermal band afocal telescopes to high accuracy may not be as easy as it might at first seem. One may need to carry out this measurement to an accuracy of 1% or better for systems, for example, where dual band overlay is required (eg a thermal display superimposed on the same scene viewed in the visual band). This paper describes some of the methods and experiments that we have carried out in an attempt to measure magnification to a target accuracy of 0.1%. These are for telescopes designed for a scanning thermal imaging system working in the 8-12um spectral region. Measurements are presented here only for a nominal X3 telescope, but in addition we have made measurements on others of larger magnification.
Responsivity eta a function of electric current was measured on HgCdTe IR detectors. According to the known values for resistivity and distances between the contacts the dependance of the responsivity on electric field was also measured. It was stated that the detectors. fabricated on crystals with low resistivity, needed unuusually high currents to attain maximum responsivities. The measurements of spectral responses showed that the detectors had their spectral peaks in 7 - 12 μm range. From the dependance of the spectral maximum on the wavelength it is possible to determine the energy gap of the semiconductor and the composition index x. We investigated the resistivity changes as a function of temperature. These changes may be explained by the temperature changes of concentrations and mobilities of carriers. which were measured by the Hall method. With some detectors another unusual phenomenon was observed, namely that the resistivity and the responsivity as function of temperature reached their maximum at 17o K and at 124 K respectively. As the above phenomenon occurs to lower degree with higher currents, we consider the trap-influence on the charge carriers to be responsible for it.
Diamond-like amorphous carbon films on germanium are prepared by plasma decomposition of methane. The optical absorption coefficient dependance in the 8 to 13 μm range with the hydrogen and impurities contents as well as the interface quality are studied by infrared spectroscopy, quantitative microprobe analysis, T.E.M. cross section and ESCA experiments. The film behaviour in severe environmental tests is also reported.
There has been interest in infrared emittance and reflectance over the years due to space applications, solar energy, thermal imaging, etc. Several laboratories have built instruments to measure the emittance or reflectance of a variety of types of samples in some or all of the region from 1 to 25 micrometers. However, it appears that there are still no traceable standards available to calibrate these instruments. As a result of discussions among interested parties, a Round Robin was organized to circulate a few representative samples to as many laboratories as practical for comparative measurements. The various instruments represent different geometries and approaches to measuring what is expected to be the same physical property. The intent of the endeavor has been to assess the state-of-the-art and gain whatever understanding is possible from differences which are found in the results. It is hoped that: this will allow future improvements in the instruments and techniques, that it will add confidence in the data for the users, and that it can lead to future standards of infrared reflectance and emittance. Many samples were suggested. The final choice was influenced by availabilty, durability, reproducability, and ease of measurement by most instruments. Some samples were chosen to be specular and therefore measurable in an absolute sense. Diffuse samples were chosen to test possible variations in the angular response of different instruments. The results are summarized and compared. The contributors were encouraged to describe their instruments and methods in separate papers in order to have a more adequate opportunity to show those details. We believe that some progress has been made as a result of the cooperation, synergism, and serendipity of the project.
This paper describes an integrating sphere - Fourier Transform Spectrophotometer (FTS) instrument and its measurements of directional hemispherical reflectance as a function of angle, temperature and wavelength in the infrared. Samples can be mounted in the center of the sphere or on the wall of the sphere. The center mounted samples can be tilted to vary the beam incidence angle from 0° to 60°; wall mounted samples can be heated to temperatures of 250°C. Measurements on samples using both sample mounts are presented and compared. A discussion of the measurement techniques used to obtain round robin results (presented in an accompanying paper) is also given. A study of the temperature dependence of a single round robin sample is presented. Detailed measurements of a ruled gold sample are given and the importance of the detector's field-of-view in explaining this data is demonstrated with a simple experiment.
Based on a FTIR spectrometer a measuring device for the determination of the spectral near-normal/hemispherical reflectance and the spectral directional emittance, respectively, of opaque, diffusely reflecting samples has been built up. The device is mainly used for the measuring of the spectral emittance of low-emitting selective solar absorber coatings. The measuring arrangement for hemispherical reflectance measurements with a gold coated integrating sphere is shown. The measuring geometry of the diffuse reflection attachment, the performance of the whole device as well as the calibration and evaluation of the measurements are described. Emphasis lies on the properties of the used integrating sphere and sphere design: on the angular response of the sphere and the influence of the limited reflectance and partly specularity of the sphere wall. It is shown that the integrating capacity of photometer spheres with an IR-active diffuse gold coating is partly reduced due to the relatively high deviation of the sphere wall reflectance from unity as well as due to the deterioration of the Lambertian behaviour of the wall indicated by a specular reflectance factor increasing with growing wave-lengths. Nevertheless the reflection method has some advantages over the radiometric measurement of the thermal radiation emitted by heated samples.
There are specialized requirements for surface optical properties in a variety of fields. Activities in space especially have stimulated interest in these properties and led to development of refined instrumentation. One of the most commonly required optical properties is directional reflectance. The design and performance of a hemi-ellipsoidal spectroreflectometer to measure this property is the subject of this paper.