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Optical Radiation

Programme Beneficiaries

The production, detection or control of optical radiation, from the ultraviolet through the visible to the infrared, is essential in a wide range of industrial applications such as product innovation, process control, product formulation and analysis, quality control and industrial processes. Its use also pervades medicine, the environment, communications and defence. A lack of reliable measurements would have a detrimental effect on the ability of UK industry to compete in the global market, by restricting innovation, by making manufacturing processes and controls less efficient, and by making it more difficult to trade within or across borders.

Industries using optical radiation include: biotechnology, pharmaceuticals, chemicals, plastics, glass, paint, semiconductor processing, aerospace, defence, optoelectronics, lighting, food, machine vision, industrial processing, textiles and printing. In fact, the list of industries that depend on optical radiation measurement is a nearly a complete role call of the UK’s industrial base. Measurement of optical radiation is also key to many health and safety issues, underpinning areas such as signalling, emergency lighting, UV exposure monitoring and medical diagnostics. Optical radiation metrology is also important for monitoring man’s impact on the environment, and for quantifying the effects such as ozone depletion and climate change.

Modern, efficient, high quality manufacturing relies increasingly heavily on optical radiation, as demonstrated through the use, for example, of non-contact, non-invasive diagnostic probes for online monitoring of chemical reactions or production processes, and the increasing prevalence of machine vision systems in automated manufacturing systems. The use of UV radiation is growing particularly rapidly, for processes such as sterilisation of the surface of fruit and vegetables to prevent rot and increase shelf life, water purification, curing of polymers and adhesives and destruction of airborne microbes in ventilation systems. Optical radiation is an intrinsic part of many production processes: for example, high-density integrated circuits could not be constructed without ultraviolet sources and the technology to measure them. In other areas, the production of optical radiation is the actual end product, e.g. electric lighting, which consumes around 8% of the electrical power generated in the UK. New technologies such as white LEDs and electrodeless lamps offer the potential for more efficient light production and consequent reductions in electricity consumption.

In the field of health optical radiation is used for clinical diagnostic systems such as photodynamic therapy for the treatment of skin cancers, flow cytometry, treatment of dermatological conditions such as psoriasis, laser based refractive surgery for the correction of myopia, and laser surgery for the removal of skin lesions. Analyses of biological agents such as bacteria and DNA often rely on the detection of fluorescence from the test sample, and the production of many pharmaceuticals depends on high accuracy measurements of transmission through manufacturing samples. Exposure of workers to high levels of UV radiation is dangerous to their health, and so control and monitoring of processes involving UV is important.

Ecologically, pollution can be monitored remotely, in real time, by optical detection systems providing instant analysis of potential hazards. And space borne optical instruments are used to monitor green biomass and the spread of deforestation, as well as to provide pictures of cloud cover for meteorological use. In addition, the health risk to the public due to the decrease in the ozone layer over northern Europe, and the consequent increase in levels of solar UV, necessitates careful monitoring of UV irradiation levels.

The Role of the Optical Radiation Metrology Programme

The NMS Optical Radiation Metrology Programme seeks to meet the widespread requirement for traceable optical radiation measurement. The Programme objectives are to:

• realise and improve national scales and standards for the measurement of optical radiation and the optical properties of materials;
• develop and extend existing measurement scales and transfer standards to meet future optical radiation measurement needs in the UK;
• provide a measurement infrastructure to enable companies, organisations and individuals to meet their optical radiation measurement requirements;
• foster innovation and stimulate UK competitiveness through the dissemination of best practice and technical advice for optical radiation measurements;
• ensure UK national standards for optical radiation measurement are equivalent to those of the UK’s trading partners.

The content of the Optical Radiation Metrology Programme was developed following extensive consultation with industry, research institutes, universities, medical physicists and regulators. This thorough understanding of user requirements, coupled with government policy for increased support for innovation (DTI Innovation Report, December 2003), has led to a significant shift in emphasis as compared with previous Programmes in this area. In particular:

• Knowledge transfer activities have been more closely focussed on providing support for innovation. At least 3 collaborative projects with industry will be carried out, to encourage the exploitation of recent developments in optical radiation, and several case studies will be developed, to encourage the greater take-up of measurement best practice in this field;
• New projects have been introduced, aimed specifically at supporting innovation in 5 key sectors: environment and climate change; imaging and displays; human factors, perception and appearance; medical and health; and manufacturing and process control;
• An increased emphasis has been placed on research to identify and develop novel techniques, to support industrial innovation and competitiveness into the future, and to maintain the UK’s strong global position in this field;
• Efforts relating to international liaison and support for regulation have been enhanced. Working in collaboration with other national metrology institutes not only helps to ensure that research efforts are not duplicated unnecessarily and that developments elsewhere are quickly and effectively exploited by UK industry, but also helps guarantee that measurements made in the UK are accepted internationally. Compliance with relevant regulations and standards is a critical aspect of the ability to trade. In a survey of technical standards and regulations conducted as part of the formulation of the Programme, over 1800 standards or regulations were identified which rely on the measurement of optical radiation or the optical properties of materials.

Maximising the Benefits from the Optical Radiation Metrology Programme

There is increased emphasis on research in the new Programme. Furthermore, as indicated above, most of the development work, and much of the work on knowledge transfer and support for international liaison and regulation, is focused on encouraging innovation in specific industry sectors. In total, these 4 activities comprise more than 70% of the total investment in the new Programme.

Recent Optical Radiation Metrology Programmes have concentrated primarily on making improvements to the uncertainty of the base measurement scales, so as to increase the “headroom” between these scales and the needs of industry and thus encourage the establishment of secondary calibration laboratories; and increasing the versatility and scope of measurement services. The focus has been on areas key to UK plc. In less important areas, traceability in the UK is taken from other national measurement institutes, e.g. traceability for UV radiation below 200 nm comes from the German institute, PTB. As a result of this investment, the UK scales for optical radiation are at the leading edge of world metrology in most areas and the UK’s national standards laboratory is regarded as a centre of excellence in this field.