NIST DEVELOPS PHOTOMETRIC AND COLORIMETRIC STANDARDS FOR LEDS.NIST (National Institute of Standards & Technology, Washington, DC, www.nist.gov) The standards-defining agency of the U.S. government, formerly the National Bureau of Standards. It is one of three agencies that fall under the Technology Administration (www.technology. has started a new project to investigate and develop measurement methods and standards for photometry photometry (fōtŏm`ətrē), branch of physics dealing with the measurement of the intensity of a source of light, such as an electric lamp, and with the intensity of light such a source may cast on a surface area. and colorimetry colorimetry Measurement of the intensity of electromagnetic radiation in the visible spectrum transmitted through a solution or transparent solid. It is used to identify and determine the concentrations of substances that absorb light of a specific wavelength or colour of light-emitting diodes (LEDs). Since high-intensity blue LEDs have recently become available, the application of LEDs is expanding rapidly in a wide variety of areas, including color displays, traffic and aviation signals, and signs. Accurate specifications of LED characteristics are therefore becoming increasingly important; however, large discrepancies in photometric pho·tom·e·try n. Measurement of the properties of light, especially luminous intensity. pho  to·met measurements of LEDs (as much as 50 %) are being reported by manufacturers and users. In order to improve the situation, NIST has investigated the technical problems and is developing standard LEDs and recommended measurement methods for luminous intensity, total luminous flux, and color (chromaticity and dominant wavelength). The NIST work is linked to the standardization efforts by CIE (Commission Internationale de l'Eclairage, International Commission on Illumination, Vienna, Austria, www.cie.co.at) An international organization that sets standards for all aspects of lighting and illumination, including colorimetry, photometry and the measurement of visible and (Commission Internationale de l'Eclairage) committees TC2-45,-46; NIST intends to have available LED calibrations and standards in 3 yea rs.
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