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Objective A chromatic method is described for providing a preliminary indication of unacceptable bilirubin levels in a newly born baby in order to avoid the development of serious mental deficiencies. The aim was to investigate the reliability of a new chromatic approach using a novel template unit for a preliminary, non-invasive monitoring of the skin tissue of newly born babies with jaundice and its capability for use with different mobile phone cameras. Approach A description of the monitoring system is given along with an explanation of the monitoring technique used. Preliminary tests have been performed on 48 different neonates each being addressed by one of six different mobile phone cameras, which were randomly available to the operating clinicians. Main results The test results have a correlation (R 2) of 0.81, a sensitivity (Sn) of 0.97, a specificity (Sp) of 0.82, a positive predictive value (PPV) of 0.95 and a negative predictive value (NPV) of 0.9. Significance The significance of the results obtained is that they show the approach to have a high level of fail-safe reliability in indicating the bilirubin levels when compared with blood test results. The results also show that the approach can be used with a few different mobile phone cameras and that because of its non-invasive nature and its cost effectiveness, has the potential for remote use from a medical hospital to provide an immediate preliminary diagnosis.

The problem of extracting quantified information from physiological and physical indicators of the fatigue level of a vehicle driver is addressed. A chromatic approach has been used for processing the physiological and physical outputs from a driver fatigue monitoring system, the physical indicator being in the form of gyroscopic signals produced by the lateral movements of a vehicle. Some preliminary results are presented which show how the chromatic signatures of the physiological and physical indicators can be used to identify fatigue thresholds and provide a more optimized estimate of tiredness.

An approach is presented for remotely monitoring person-based events at a series of locations in a domiciliary environment in order to extract information about movement between locations and to quantify the extent of any persistent events at a particular location. Each individual event is detected via a change in the optical chromaticity of a location and not the person. Movement between locations is determined using space and time-based chromaticity to analyse the dynamics of the sequence of events. An example of the deployment of the approach is presented.

Given the wide ranging concern about air pollution by particulates of sizes 2 to 10 µm, there is a need for a cost-effective, easily deployed, portable system of moderate accuracy (rather than high precision) for temporary use on sites or on board vehicles to monitor such particulate concentrations. This paper describes such a system, which is based upon a chromatic modulation technique. A brief explanation of the chromatic approach is given followed by a description of the particulate monitoring unit. The performance of this unit has been established via various calibration tests and the instrument has been deployed for real life use at a number of sites. Some preliminary results are presented from a city centre bus terminus, the depot of a major bus operator and a site close to an official monitoring station.

One method for the identification of incipient transformer failures due to partial discharges involves measuring the concentration of dissolved gases in the transformer oil. The number of gases monitored is often considerable (≥10), and there is a problem in tracking time varying patterns of the concentration of these gases to yield meaningful prognostic information. This contribution describes the use of chromatic processing techniques in the gas identification domain for yielding conveniently assimilable information in the form of chromatic maps for prognostic purposes. Such maps take the form of polar diagrams of various chromatic parameters such as hue (dominant species), saturation (breadth of gases per cent) and lightness (the overall concentration of gaseous species). Three categories of transformer working conditions (safe, alert and faulty) have been established based on such chromatic signatures. A simple probabilistic model, which can facilitate examination of the implication of future data gathered online, has been assembled.

The use of chromatic processing for monitoring aviation fuels under different conditions is described. The approach is based upon the use of a reflective optical fibre probe energized via two light emitting diodes. Results are presented which show how the chromatic approach can discriminate between fuels of different types and fuel contaminated with water under both quiescent and agitated conditions.

Optical polarization processes in a parallel-sided glass element used in a Faraday rotation current sensor have been considered. In such sensors the path length necessary to produce sufficient rotation of the plane of polarization is produced by a multiplicity of reflections within the glass element. It is shown that such reflections induce ellipticity of polarization and that this affects the current-sensing performance of the sensor. Two reflection cases, corresponding to total internal reflections at a glass-air interface and reflections by aluminium-coated surfaces, are considered. The latter are shown to produce higher optical attenuation but a lower degree of elliptical polarization. The implications of the induced elliptical polarization in relation to chromatically modulated polychromatic light are considered. It is shown that the resolution of the Faraday sensing is improved by minimizing the ellipticity of the polarization with the aluminium-coated reflections. However a greater dynamic range and signal strength may be achievable with the total internal reflection element.

A technique is proposed for determining the location of an arc-discharge filament in a circuit breaker or a plasma torch utilizing only three photo-detectors, with the same spectral sensitivity, to observe the optical radiation emitted from the arc. The three detectors are placed at different azimuthal positions perpendicular to the central axis of the arc filament and are arranged symmetrically with respect to the central axis of the arc chamber and with their angular responses non-orthogonal. Outputs from the photo-detectors are analytically processed to yield two chromatic parameters, (the nominal radial mode) and (the dominant azimuthal mode), which define the arc location in the laboratory frame (, ). and are defined by algorithms used in chromatic processing. As an illustration, the technique has been applied to interpret some experimental results for determining the location of an arc filament lying within the nozzle of a gas-blast circuit breaker.

A technique for interpreting acoustic signals is presented based upon the use of Gabor type devices. This interpretation technique processes the information acquired from vibration sensors and presents the information as three time-varying parameters which represent the dominant signal frequency, the nominal breadth of the frequency content of the signal and its effective energy content. The technique is an extension of the chromatic analysis used successfully in the optical domain. The information produced by this analysis proves to be more convenient for defining a signal than that yielded by the conventional Fourier transform approach. By way of an example, the Gabor transform based technique is applied to the monitoring of acoustic signals generated by a high-voltage circuit breaker (as used on power transmission networks). Results are presented which indicate that the technique is capable of quantifying trends in complicated time-varying acoustical signals.

An optical sensor multiplexing system is described which uses code division multiplexing (CDM). A novel CDM code has been developed for use with spatial light modulators (SLMs) which has advantages compared with conventional CDM codes. Conventional codes introduce significant crosstalk levels in the demultiplexed signals which can be reduced by using long pseudo random bit sequences (PRBSs). The new code, however, ideally introduces no crosstalk which allows much shorter PRBSs to be used with the additional benefit of a reduced duty cycle time. In a test system with twelve sensors the measured signal-to-noise ratios (SNRs) were in the range 68+or-2 dB and the crosstalk levels were less than -70 dB.

A thin film measuring system for the online monitoring of semiconductor films during processing with a radio frequency plasma is described. The method is based upon the use of chromatic processing of polychromatic interference signals produced by the thin semiconductor film when illuminated with white light. A description is given of the interpretation of the polychromatic signals produced by interference effects and some typical experimental results are presented to illustrate the capabilities of the technique. The approach utilizes cost effective instrumentation with acceptable time response for real time process control via optical fibre transmission. It is currently being incorporated as part of an intelligent knowledge based system for such process control.

A novel optical fibre sensor has been developed for on-line monitoring of oil quality within industrial equipment. The monitoring is based on chromatic modulation because of the inherent self-referencing demonstrated by this technique. The sensor is shown to exhibit long-term stability and is capable of operating up to a temperature of 120 degrees C. Several industrial oils have been examined using the sensor, and typical modulation depths of 20% were obtained with resolution in the range of 0.1%. This is sufficient to record some interesting physical and chemical changes related to the reaction kinetics of oil degradation. The sensor is also capable of detecting oil leaks within a system since it can distinguish between the chromaticities of oil and air.

A novel chromatic pressure sensor has been investigated. The sensor consisted of an absorbing glass modulator mounted on a diaphragm and was addressed by a pair of optical fibres. The chromatic transmission of the sensor varied with pressure as the modulator moved within the fibre gap. By monitoring the chromatic transmission, pressure measurements with signal to noise ratios up to 1 in 2.7*103 were achieved. A prototype system incorporating 300 m of optical fibre and four couplers was successfully used to measure pressure in a potentially explosive reaction vessel.

The motivation for the present contribution was to produce a cost effective, convenient system for the optical monitoring of degraded high voltage transformer oils using the chromaticity of polychromatic light transmitted through the oil. The technique uses readily available and portable instrumentation. Examples of results for typical oil samples have been obtained with the technique and comparisons made with the conventional technique of Colour Index. It is shown how the chromatic technique can supplement the Colour Index approach to provide additional information about changes in the transformer oil, such as the presence and extent of solid micro-particles.

An economic approach for the preliminary assessment of 2–10 µm sized (PM10) airborne particle levels in urban areas is described. It uses existing urban closed-circuit television (CCTV) surveillance camera networks in combination with particle accumulating units and chromatic quantification of polychromatic light scattered by the captured particles. Methods for accommodating extraneous light effects are discussed and test results obtained from real urban sites are presented to illustrate the potential of the approach.

An approach is described for discriminating between different liquors with a portable system based upon chromatic monitoring. It uses a webcam–computer combination in a robust manner and has the potential for making cursory assessments in the field. The behaviour of the system has been investigated using subsidiary measurements with a spectrometer, from which the repeatability of test results has been assessed. It is shown that the webcam–computer system can provide useful referencing to reduce the influence of system artefacts and so yield good discrimination between different liquors without the use of a spectrometer.

Methods based upon chromatic analysis are described for quantifying broadband optical absorption spectra in discriminating between different types of liquors. The absorption spectra are quantified by three chromaticity coordinates, which can be represented by two points, one on each of two chromatic diagrams. Various types of liquors may then be distinguished on such chromatic maps and groups of similar samples conveniently identified. Examples of the deployment of the approach are given for distinguishing between and classifying various types, brands and mixtures of alcoholic beverages and for identifying an authentic brand. The method provides a high level of traceability and is not restricted to a particular type of optical spectrum.

A system for addressing the scale of activity and detecting periods of immobility of a vulnerable individual is described. The system does not invade the privacy of the individual, is robust to ambient changes and is economic in terms of cost and the amount of data captured. The system is based upon the cross-correlation of changes in the chromatic signatures of a limited number of locations in an environment with the outputs from a triggerable infrared sensor. Results are presented to indicate the system performance.