Applications of optical radiation are very diverse, including lighting of homes, shops and factories, signalling for road, rail, sea and air transport, process control in industries such as printing, plastics, textiles and pharmaceuticals, and medical treatments such as ultraviolet phototherapy for some skin diseases. As applications increase, so does the need for increasingly accurate optical radiation measurements of sources, detectors and materials.
The Photometry and Radiometry laboratory of NMISA is responsible for optical radiometric measurements. Optical Radiometry is the science of measuring radiant quantities (eg. power, irradiance, radiance, etc.) within the ultraviolet, visible and infrared regions of the electromagnetic spectrum.
Optical Radiometry services have been internationally classified in four branches to facilitate the selection of services via the database search engine.
Photometry: radiometry in the part of the spectrum perceived by the human eye as the sensation of light (380-780nm)
Properties of Detectors and Sources
It includes properties of detectors, spectral emission properties of sources and spectrally-integrated measurements for sources and detectors
Properties of Materials
Spectral properties of materials as well as colour and other spectrally-integrated measurements of materials are covered
The basic unit used in the field of Optical Radiometry is the candela. The candela (symbol: cd) is the standard unit of luminous intensity in the International System of Units (SI). It is formally defined as the magnitude of an electromagnetic field, in a specified direction, that has a power level of 1/683 watt (1.46 x 10 -3 W) per steradian at a frequency of 540 terahertz (540 THz or 5.40 x 10 14 Hz ).
Photometry and Radiometry has close links with the International Commission on Illumination (CIE). The CIE is a technical, scientific and cultural non-profit organization whose objectives are:
- To provide an international forum for the discussion of all matters relating to the science, technology and art in the fields of light and lighting and for the interchange of information in these fields between countries.
- To develop basic standards and procedures of metrology in the fields of light and lighting.
- To provide guidance in the application of principles and procedures in the development of international and national standards in the fields of light and lighting.
- To prepare and publish standards, reports and other publications concerned with all matters relating to science, technology and art in the fields of light and lighting.
To maintain liaison and technical interaction with other international organizations concerned with matters related to the science, technology, standardization and art in the fields of light and lighting.
Staff members of the laboratory serve on the relevant technical divisions of the CIE as South African representatives. The involvement is enhanced by the participation in the activities of the Illumination Engineering Society of South Africa (IESSA) who represents the CIE in South Africa, keep all lighting and related interests of this area informed of CIE recommendations and proceedings, and in general, assist in giving this region the benefit of developments that take place.
The Photometry and Radiometry Laboratory Supports:
- Supply traceability to SANAS accredited calibration and testing laboratories
- Supply traceability to measurements made in trade (under pin fair trade)
- Small, medium and micro enterprises
- The following industries: Lighting, Automotive, Aerospace, Paint, Textiles, Medical and Health, Light Industrial Metal Fabrication
- Traceability to NMI’s in AFRIMETS
Photometry & Radiometry Laboratory Involvement in Metrology
- Represents SANAS special technical committee for Photometry & Radiometry and Fibre Optics metrology and perform technical assessments and inter-laboratory comparisons on behalf of SANAS.
- Representation on SABS technical committees eg; TC64, SC64A, SC64C and the LED working group of SC64A.
- Representing South Africa on international committees of the BIPM, Consultative Committee for Photometry and Radiometry and its associated working groups, ensuring equivalence of measurements.
- In AFRIMETS through training, assessment and piloting comparisons.