Proprietary Technologies
| Oxford Medical Diagnostics owns and also licences a range of technologies: Laser and Broadband, Cavity Enhanced Absorption Spectroscopy (‘CEAS’ and 'BBCEAS') As developed and patented by the University of Oxford and licensed to the Company exclusively. Plasma Emission Spectroscopy (‘PES’) As developed and patented by the Company. |
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Cavity Enhanced Absorption Spectroscopy (‘CEAS’)
The general technique of Cavity Enhanced Absorption Spectroscopy (‘CEAS’) covers a wide range of closely linked optical analysis technologies – all sharing a common feature where a short (10-100 centimetres) optical cavity is used to enhance the effectiveness of laser light to detect the concentration of trace gaseous molecular species within a volume of bulk gas – e.g. air.
The current technical focus at Oxford Medical Diagnostics is on the use of Tunable Diode Lasers. This technique utilises an optical cavity with ultra-high grade mirrors at both ends, enabling repetitive wavelength scanning over the targeted region of absorption, hence considerably enhancing sensitivity through an effective increase in the sample path length to several kilometres.
Broadband Cavity Enhanced Absorption Spectroscopy (‘BBCEAS’)
Lasers normally operate over a “narrow” wavelength range, i.e. they are very good for observing isolated small molecules with very clear, well separated spectroscopic features, but often do not work over the whole of an absorption spectrum which would be needed to characterise a “large” molecule. Broadband systems, in contrast, will operate over a wider spectral range, and thus are of more use for detecting these larger species.
The newly patented technique uses two broadband sources. One is not a laser, but a Superluminescent Light Emitting Diode, or ‘SLED’, a spectrally bright source which has largely been developed for the telecoms industry. The radiation is passed into an optical cavity to enhance the path length, and then into a spectrometer of some kind to disperse the radiation into its different wavelengths – presently a small Fourier Transform Infra-Red (FTIR) machine. In future, the detection can be achieved with simple spectrometers or even optical filters. The second, brighter source, applicable to the new technique is a supercontinuum source – a pulsed device which is sent into an optical fibre to convert the monochromatic wavelength into a broad continuum. Both of these devices (SLED or supercontinuum source) have been shown to be able to detect acetone in a breath matrix at ppm (parts per million) levels in a scan lasting four minutes.
Plasma Emission Spectroscopy (‘PES’)
PES involves the spectral analysis of light generated from a gaseous sample through which a small (c. 5mm) electric arc is passed. The design of the Oxford Medical Diagnostics Breath AnalyserTM is based on previous work by designer Tim Moor, supported by the experimental work of Professor Albert Crowe, formerly Head of the Physics Department, Newcastle University, UK.