Two standards relating to LED chromaticity and photometric measurements have already been published in 2008, and more are in the pipeline, according to a recent report in LEDs Magazine.
At the beginning of 2008, the American National Standard Lighting Group (ANSLG) published ANSI_NEMA_ANSLG C78.377-2008 entitled "Specifications for the Chromaticity of Solid State Lighting Products".
The standard can be downloaded as a PDF file for $60 from the ANSI (American National Standards Institute) website, or for free from the NEMA (National Electrical Manufacturers Association) website at www.nema.org/stds/ANSI-ANSLG-C78-377.cfm.
This standard specifies the range of chromaticities recommended for general indoor lighting with SSL products, and ensures that the white light chromaticities of the products can be communicated to consumers.
In June 2008, the Illuminating Engineering Society of North America (IESNA) published a documentary standard LM-79 entitled "Electrical and Photometric Measurements of Solid-State Lighting Products."
This describes the methods for testing SSL products for their photometric characteristics such as total luminous flux (lumens), luminous efficacy (lm/W), luminous intensity (candelas) in one or more directions, chromaticity coordinates, correlated color temperature (CCT) and color rendering index (CRI).
The most substantial part of LM-79 describes test methods for total luminous flux measurement, which is to be carried out with an integrating sphere or a goniophotometer. Crucially, LM-79 specifies absolute, rather than relative, photometry.
For other light sources and luminaires, there are separate standards for the measurement of lamps or luminaires. However, because in many current SSL products the LED light source(s) in the luminaires are not easily separable as replaceable lamps, the existing standards cannot be applied directly to SSL products.
The LM-79 document says that "since SSL technologies are still at their early stages, requirements for measurement conditions and appropriate measurement techniques may be subject to change at any time."
LM-79 can be ordered as a print version from the IESNA website. The cost is $25 to non members (30% discount to members).Click on Bookstore (upper menu bar), choose Print Publications and then in the Product ID box type in LM-79.
