The "General Rules for White LED Metering for Lighting" jointly developed by the four Japanese groups is currently the only measurement standard for white light-emitting diodes (LEDs) for lighting. This article will introduce and analyze its contents for readers and related products. , study, research department reference.
White LED standard release With the rapid development of LED research and development technology, it has been regarded by many people as the main lighting source of new generation with full potential. However, LED has different spatial illumination characteristics from traditional illumination source, which is suitable for the measurement of optical characteristics of traditional Light Source. The method does not necessarily apply to LEDs such as Luminous Flux, Luminous Intensity, and Chromati City measurements, otherwise the measurement accuracy and accuracy of LEDs will be problematic. Therefore, the world's major standards associations have revised or added LED measurement standards, but because of the wide variety of LED packages and performance, there are also associations to develop new measurement standards for LEDs for different purposes. Commission Internationaledel For example, 'Eclairage CIE', which significantly revised the original LED measurement technology file CIE-127 in 2007, but due to many controversies, there are still many measurement problems to be solved, and the US Department of Energy (DOE) is leading the cooperation. The development of solid-state lighting products, a standards development group consisting of the American National Standards Institute (ANSI) and the North American Lighting Society (IESNA), is developing standards for solid-state lighting related test standards, including optical rotation measurements, color metrics. Standards such as measurement and life assessment, but these standards are characterized by the fact that solid-state Lighting Fixtures are considered as a whole, that is, LED cells cannot be measured by these standard specifications.
In recent years, China has also been committed to the promotion of semiconductor light-emitting device standards. With the support of the government, semiconductor light-emitting device test methods have been introduced, and other relevant standards are under review.
However, the fastest-growing country in the promotion of white LED standards for lighting is Japan, including the Japan Lighting Society (JIES), the Japan Lighting Commission (JCIE), the Japan Lighting Industry Association (JIL), and the Japan Electric Ball Industry Association (JEL). In 2004, four common standards "General Rules for White LED Metering for Lighting" have been established, which has become the only measurement standard for white LEDs for lighting. It has been the first to develop several unregulated standards in the first edition. Projects such as the manufacture of standard LEDs, the measurement of light intensity of small modules, and the method of life assessment.
In view of the progress of LED measurement methods and the expansion of standard content, the four groups announced the revision of this standard in March 2006, adding and revising the original standard content, measurement of colorimetry and luminous flux. More detailed specifications are made, such as measurement methods. However, based on the cautious mentality, many parts are still placed in the subsidiary part instead of the actual standard. However, the description of the relevant specifications is still very detailed. At this stage, the international standard can be found in the LED standard literature. It can be said that it is the most complete specification of content. This standard will be a very important reference when the industry still lacks appropriate general LED measurement specifications. The following highlights the important provisions of this standard, as well as the supplements to the revised version.
The scope of application is limited to white LEDs for lighting. In the beginning of the standard, the standard has been declared to be limited to white LEDs for illumination. It is considered to limit the measurement target to white LEDs for illumination to limit the measurement method compared with standard LEDs. Effectively improve measurement accuracy, and make detailed provisions for the content of standard LEDs. In the measurement part of the light intensity, the measurement is carried out according to the standard conditions specified by the International Commission on Illumination; in the measurement part of the luminous flux, the integration sphere is used for measurement, and the chromaticity and correlated color temperature are added in the revised version (Correlated Color). Temperature; CCT), Color Rendering Index (CRI), etc., and in principle the integrating sphere is used as its incident optical system.
This standard is mainly for the specification of single LED, but its measurement of the light intensity of small LED modules is also included in the specification. For small LED modules, it is not necessarily applicable to the average LED light intensity specified by CIE standard conditions. Measurement methods.
White LEDs for lighting are clearly defined as the biggest difference between this standard and other LED related standards. A clear definition of "white LEDs for lighting" is made. According to the interpretation of this standard, the so-called "white LED for illumination" has a light color that measures the luminous flux or the average light intensity, and the spectrum must cover the entire range of the visible light field, and there must be no missing parts; the relevant color temperature The range is within (2500~10000)K; and the correlated color temperature is on the CIE1960 Uniform Chromaticity Scale (UCS) coordinate, and the deviation from the Planckian Locus (Duv) must be less than 0.02.
It is worth noting that in this definition, RGB tri-color LEDs will be excluded from the range of white LEDs for illumination. In fact, in the interpretation of the annex to this standard, the definition of illuminated white LEDs is a controversial project. In terms of the relevant color temperature, since it is for general lighting, it is considered to be the same level as the Fluorescent Lamp (the relevant color temperature is about (2700~8000)K), but it is based on the actual development of white LED. According to the technique, the range of the correlated color temperature is set to be in the range of (2500 to 10000) K.
The light intensity/light flux is two large-scale measurement methods. Because there is no standardized and uniform LED package shape, size and light distribution characteristics, but different design structures are generated according to various purposes, LED measurement is difficult. Therefore, the structure, performance, and reproducibility of standard LEDs must be specified.
In this standard, standard LEDs are mainly divided into light intensity measurement and luminous flux measurement (see Table 1), which have different design concepts depending on the measurement characteristics. For example, a standard LED for light intensity measurement, because in the light intensity measurement method, the mechanical axis of the LED to be tested (MechanicalAxis) is a significant correction factor, so the standard is In the case of a bullet type that is easy to align with a mechanical shaft, a standard LED is used. As for the measurement of the total luminous flux, the standard LED for light flux measurement prevents the light from being emitted toward the rear of the LED and the light intensity is relatively uniform. The metal can type (TO-Can) package is used as a standard form. It is worth noting that the two types of standard LEDs here are white LEDs made of indium gallium nitride (InGaN) series chips combined with yttrium aluminum garnet (YAG) phosphors, which correspond to the definitions. The portion of the white LED that is used for illumination without missing wavelengths.
Since standard LEDs are an important reference for measurement, the standard is expected to minimize the instability of optical and electrical characteristics to minimize the effects of the surrounding environment to achieve the desired reproducibility requirements. In addition to limiting the measurement ambient temperature variation to less than 2 °C, in order to reduce the initial variation of LED, it is recommended to use a standard LED that has been driven by a constant current (such as 20 mA) for more than 100 hours. The ambient temperature of the standard LED must be controlled. At 25 ° C. In the revised version, it adds a temperature control socket (Socket) for the Lighting Fixture with chip temperature control in Annex 4, which requires the LED to reach the thermal equilibrium state under constant current conditions (hopefully at least The lighting measurement was performed after 5 minutes or more.
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