In the manufacture of aluminum, an electrolytic process is used. Carbon anodes are used in the process (see Figure 1) to conduct electricity, and the carbon of the anode is consumed, forming carbon dioxide from oxygen in the ore (Al203). If the anodes are of uniform resistance, the current will be uniform and the anodes will be consumed evenly. The quality of the carbon anodes is a function of the temperature control during the baking process. Recently, infrared sensors have been used in a computer-aided process (Infracom System) that controls the baking cycle of the anodes.

Coals consist of a wide range of plant matter which has undergone metamorphosis, as well as various minerals. The organic matter in the coal contains the remnants of a variety of parts of plants such as trunks, bark, roots, stems, leaves, spores, and so forth. The various coherent remnant organic bodies in the coal, which are generally of microscopic dimensions, are termed "macerals." Most analyses of the chemical functionalities in coals use the coal in a ground-up particulate form which contains a huge variety of different macerals as well as minerals. Such analyses give only averaged information, rather than being characteristic of any individual component of the coal. Now, however, a new microscopic IR (infrared) spectroscopy technique makes possible the chemical analysis of individual macerals of coal. Areas as small as 25 micrometers across can be analyzed. The technique utilizes a computer-controlled IR microspectrophotometer (which is now commercially available) in conjunction with newly-developed procedures for preparing uncontaminated thin sections of coals. The sample preparation technique utilizes a hydrocarbon-soluble adhesive to cement the coal to a glass slide for final grinding. This enables removal of the adhesive with a solvent to produce an uncontaminated specimen. A suitable thickness for the specimens has been found to he roughly 15 micrometers. Using this technique variations from specimen to specimen within a given maceral type, or even heterogeneities within a single maceral, can be determined. Preliminary experiments using this new technique have been made on single macerals of homogeneous vitrinite and liptinite in Illinois No. 6 coal. The spectra clearly contrasted the more aromatic and hydroxyl-containing structure of the vitrinite to the more aliphatic structure of the liptinite. In this paper, details of this new technique are discussed, and recent results, including representative spectra, are presented.

The Raman microprobe "MOLE" (Instruments SA, Metuchen, NJ) allows one to obtain a Raman spectrum from a particle as small as one micron in diameter. The technique depends on the spectral analysis of light scattered from a monochromatically (laser) illuminated sample under a microscope; no vacuum is required, and in-situ analysis is usually possible, with minimal sample preparation. The Raman spectrum obtained from the sample, which may be organic or inorganic, gives molecular information which is useful for identification or quantitative analysis. A brief description of the method will be given, with advantages and disadvantages. Applications to various problems of semiconductor device manufacturing including contamination control, corrosion, silicon morphology, and packaging, will also be presented.

The development of Ultra violet (UV), along with near infrared (NIR) and infrared (IR) transmissive fibers, has motivated rapid evolution in technologies including communications and analytical chemistry. In both cases the emitting source, whether it be a laser diode or a participant in a chemical reaction, uses the fibre to transmit the light to a diffraction grating for dispersion. In the case of a communications application, this dispersed light will either terminate at a detector or be directed into other fibres. Diffraction gratings that have been optimized using ion-etching techniques or classical ruling have been used to produce devices capable of handling up to 20 fibres with up to 40 wavelengths simultaneously.

Electron probe microanalysis (and scanning electron microscopy with energy dispersive x-ray analysis) has been used for small area analysis for many years, but it gives only elemental information, in general. Cathodoluminescence and photoluminescence have been available as small area analytical techniques for several years, giving molecular information. Two "new" small area molecular analysis techniques have become available in the last few years, viz Raman (to be discussed in this symposium by C.L. Needham) and infra-red, which we will discuss. Examples will be given of the application of these various optical microanalytical techniques to device and packaging manufacture. The electron probe microanalyzer has been used for many years for analysis of small areas of microelectronic devices and packaging (e.g. Prof. Dave Wittry's initial analysis of Purple Plague was 1959). This type of analysis has been extended widely with the developments of scanning electron microscopes and energy dispersive x-ray analysis detectors and circuitry. Such analysis is elemental, in general, and has been very useful in the study of microstructure, thin films, contamination, corrosion products, etc. in all stages of device development, manufacture, test and application. However, often even quantitative elemental information lacks definition, and molecular information (how the elements are bonded together) is required. (In the analysis method described, some limited molecular information is available in low atomic number elements by measuring x-ray line shifts.)

Quantitative measurement of spatial characteristics of cathode ray tubes are becoming more and more important as the electronic display market grows both broader and deeper. Today with the emergence of very high resolution display systems, the need for accurate measurement of CRT's resolution and deflection linearity characteristics becomes increasingly essential.

The appearance of a manufactured product, given that it will fulfill its intended purpose, is its most important attribute. Appearance often determines the acceptability of a product to its seller, and ultimately to the consumer or end-user. The quality of the appearance of a product is psychologically related to its expected performance and useful life. It therefore determines its reception by potential purchasers. This paper describes the interaction of light with objects; reflection, absorption, transmission, or a combination of these phenomena, which result in the perception of the objects, and how measurements that correspond to the way the eye sees color may be made.

The color of an object depends on how you look at it. The color of the illumination plays a major role. The direction of the illumination and the direction of viewing relative to the object can significantly affect the color. If a measurement of color is to quantify the color appearance, the geometric and spectral conditions of measurement must simulate the geometric and spectral conditions of observation. The colorimetry of specimens that exhibit gloss or sheen require special attention to the light specularly reflected from the surface. Metals are a special case. Much remains to be done to standardize geometric conditions in colorimetry.

The recent development in both theory & instrumentation places colorimetry in a new era. We see colorimetry applications having a great potential in the automotive industry. In general the applications can be categorized in three aspects. They are quality control, process control as well as material development.

Today, accurate color measurement of color cathode ray tubes requires a spectroradiometer. This instrument scans the spectral output of the CRT's phosphors and then a desktop computer is used to transform the spectral data into tristimulus values (X, Y, Z) and then into chromaticity coordinates x, y and finally, if needed and valid, into correlated color temperature values.

Microspectrophotometers capable of obtaining absorption or reflectance spectra of samples down to 2 micrometers in size will be discussed. Variations of spectra obtained from fibers, paint chips, colored dots and inks are remarkably different for dyes and pigments which appear similar to visual examination. Without cumbersome sample preparation, microspectrophotometry is therefore a fast and ideal technique for matching unknowns to specific materials for forensic investigations and document verification.

Combustion involves the burning or oxidation of a fuel which liberates heat. A fuel requires oxygen, an initial excitation in the form of heat, and a finite time and mixing to drive the combustion reaction to completion. An example of methane combustion can be symbolized as follows: CH4 + 202 + 7.52N2 → CO2 + 2H2O + 7.52N2 + Heat

Information is presented which provides general guidelines for evaluating optical specifications during the design phase of electro-optical instrumentation. These guidelines address the cost impact and production problems which can arise from overly stringent component and coating specifications and tolerances. Although applicable to a wide range of E-0 instrumentation, the main focus is on non-imaging infrared systems, with particular emphasis on optical coating and filter specifications.

The use of NDIR techniques for the monitoring of gases in industrial processes is discussed. Gas analyzer configurations utilizing microphone detectors and solid state detectors are reviewed. Typical applications are presented.

A system has been developed which permits the remote non-contact sensing of the correct fill level of granular, diffuse scattering materials where electrical connections may pose a hazard. The system consists of a sensor head, a fiber optic cable containing three low-loss fibers, and a small console which contains the light source, detector and all electrical and electronic components. The system uses a pair of nearly collimated parallel light beams to define a pair of lines in space, which are intersected at a small angle by the field of view of the detection system. The midpoint between the two intersections is the position at which a scattering surface produces equal intensity signals at the detector from the two beams. The distance below the sensor head at which the intersection occurs defines the level at which valve closing signal is generated. In order to label the light beams, a chopper modulates the two beams 90° out of phase. This permits separation of an automatic gain control signal to virtually remove dependence on the absorbance of the scattering material, as well as permitting independent measures of the two backscatter signals which activate a comparator when the relative scattering intensity from the nearer beam exceeds that from the further beam. Within the defined operating range, the reproducibility of trip level is about ±0.7% at a range of about 300mm.

Spectral radiance measurements in the 1.7μm - 15μm region were made on the burner flames of several industrial boiler facilities using different fuels over a wide range of operating conditions. From these data, it was found that the ratio Ro of the flame radiance in two spectral bands is closely correlated to the excess air or fuel/air ratio at the burner. This ratio is dependent upon the load or fuel rate and it must be compensated for load changes. Under some conditions, another spectral ratio RL was found to be proportional to the load and can be used to correct Ro. By means of a simple algorithm involving Ro and RL (or the fuel rate), the excess air at an individual burner can be calculated. A simple prototype burner monitor was built which measured these two ratios simultaneously. This was tested on boiler facilities burning oil, gas and coal. It was found that this instrument would indicate the excess air at a burner to an accuracy of 1.5% (0.3% O2). In some cases, such as when firing, with gas, the RL ratio does not adequately correct for load changes and an external input of fuel or steam rate must be used instead of RL.

Optical diagnostics provide the capability for nonintrusive, on-line, real-time analysis of chemical process streams. Several laser-based methods for monitoring fossil energy processes have been evaluated. Among the instrumentation techniques which appear quite promising are coherent anti-Stokes Raman spectroscopy (CARS), laser-induced breakdown spectroscopy (LIBS), and synchronous detection of laser-induced fluorescence (SDLIF). A CARS diagnostic was implemented on a coal gasifier and was successfully employed to measure species concentrations and temperatures within the process stream. The LIBS approach has been used to identify total trace impurities (e.g., Na, K, and S) within a gasifier. Recently, individual components in mixtures of aromatics hydrocarbons have been resolved via the synchronous detection of laser-induced fluorescence.