The "General Principles of White LED Photometry for Lighting" jointly formulated by four groups in Japan is the only measurement standard for white light-emitting diodes (LEDs) used in lighting. This article will introduce and analyze the contents of the white LED light-emitting diodes (LEDs) for readers and related products. , learning, research department reference.
The white LED standard is released With the rapid development of LED research and development technology, many people have been regarded as the new generation of major lighting sources full of potential, but LED has a different spatial light characteristics from the traditional lighting source, so that originally applied to traditional light source optical characteristics measurement The method does not necessarily apply to LEDs such as LuminousFlux, Luminous Intensity, and Chromaticity measurements, otherwise the measurement accuracy and accuracy of the LED will be problematic. Therefore, all major standards associations in the world have revised or added new LED measurement standards. However, due to the large variety of LED packages and their different performance, there are also associations that have developed new measurement standards for LEDs for different purposes to the International Commission on Illumination (Commission Internationale de' Taking the example of “Eclairage; CIE†as an example, it substantially revised the original LED measurement technology document CIE-127 in 2007. However, due to many disputes, there are still many measurement problems to be solved, and the US Department of Energy (DOE) dominates. In conjunction with the promotion of solid-state lighting products, the standards development group formed by the American National Standards Institute (ANSI) and the North American Institute of Illumination (IESNA) is working on the development of solid-state lighting fixture-related test standards, including optical rotation measurements, Color measurement and life assessment standards, but the characteristics of these standards is that the content is to evaluate the solid-state lighting as a whole, that is, the LED monomer can not 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 countries in the promotion of white LED standards for lighting are Japan, including the Japan Society of Illumination (JIES), the Japan Lighting Council (JCIE), the Japan Lighting Industry Association (JIL), and the Japan Electric Ball Industry Association (JEL). ) In 2004, the four group common standard "General rule for white LED light metering methods for lighting" was established. It has become the only measurement standard for white LEDs used in lighting. It was first developed in the first edition and has not been specified before. Projects such as the manufacture of standard LEDs, light intensity measurement of small modules, and life assessment methods.
In view of the progress made in the measurement methods of LEDs and the content of the standard, there is still room for expansion. The four groups announced the revised version of this standard in March 2006, adding and revising the original standard content, measurement in colorimetry and luminous flux. Measurement methods, etc. to make more detailed specifications. However, based on a cautious attitude, many parts are still part of the subsidiary part rather than the actual standard. However, the specification of relevant regulations is still very detailed. The standard LED literature that can be found internationally at the current stage is this standard. It can be said that the content is the most complete specification. In the current industry is still lack of appropriate general-purpose LED measurement specification, the standard will be a very important reference. The following highlights the important provisions of this standard, as well as additional parts of the revised version.
The scope of application is limited to white LEDs for lighting. At the beginning of the standard, the standard has been declared to be limited to the use of white LEDs for lighting. It considers that the measurement target is limited to the white LEDs used in lighting to limit the measurement methods that can be compared with standard LEDs. Effectively improve the measurement accuracy, and make very detailed provisions for the contents of the standard LED. In the light intensity measurement part, the measurement is performed according to the standard conditions specified by the International Commission on Illumination. In the measurement part of the luminous flux, the Integrating Sphere is used for measurement, and the chromaticity and correlated color temperature are added in the revised version (CorrelatedColorTemperature; CCT), Color Rendering Index (CRI), and the like are measured, and an integrating sphere is used as its incident optical system in principle.
This standard is mainly aimed at the specification of single LED, but it also includes the specification for the measurement of the light intensity of small LED modules. For small LED modules, it does not necessarily apply to the average LED light intensity specified by the CIE standard conditions. Measurement methods.
The definition of the white LED for lighting is clear. The biggest difference between this standard and other LED related standards is to define the "white LED for lighting" very clearly. According to the interpretation of this standard, the so-called “white LED for illumination†measures the luminous flux of its luminous flux or average light intensity to satisfy the spectral range covering almost all areas of visible light, and there must be no missing part of it; correlated color temperature The range is (2500 ~ 10000) K; and the correlated color temperature at the CIE1960 Uniform Chromaticity Scale (UCS) coordinates, the deviation from the Planckian Locus (Duv) must be less than 0.02.
It is noteworthy that, in this definition, RGB tri-color LEDs will be excluded from the scope of white LEDs for lighting. In fact, in the explanation of the annex to this standard, the definition of white-light LEDs is a controversial project. In terms of the related color temperature regulations, since this is aimed at general lighting, the beginning is based on the same degree as the fluorescent lamp (the correlated color temperature is (2700~8000)K or so), but it refers to the actual development of white LEDs at present. Because of the technology, the range of the correlated color temperature is set to a range from (2500 to 10000)K.
Light intensity/luminous flux is a large number of measurement methods Because there is no standardized and uniform LED package shape, size, and light distribution characteristics at present, different design structures are produced according to various purposes, so it is difficult to measure the LED. Therefore, the structure, performance and reproducibility of the standard LED must be specified.
In this standard, the standard LED is mainly divided into light intensity measurement and luminous flux measurement, which have different design concepts depending on the measurement characteristics. For example, the standard LED for light intensity measurement is a calibration factor that is important in the light intensity measurement method for the mechanical LED axis (PhotoDetector). Lamps with easy alignment of the mechanical axis are used as the standard form; as for standard LEDs for luminous flux measurement, due to the measurement rule of full luminous flux, the use of the LED prevents the emission of light toward the rear of the LED, and the light intensity is relatively uniform. The TO-Can package is the standard form. It is noteworthy that the two types of standard LEDs here are white LEDs made of indium gallium nitride (InGaN) series chips and yttrium aluminum garnet (YAG) phosphors, which are corresponding to the definition items. The wavelengthless portion described for the lighting white LED.
Since the standard LED is an important reference for measurement, the standard hopes to minimize the instability of the optical and electrical characteristics while minimizing the influence of the surrounding environment in order to achieve the desired reproducibility. In addition to limiting the temperature variation in the measurement environment to less than 2°C, this standard recommends the use of standard LEDs that have been driven for more than 100 hours of constant current (eg, 20 mA) to reduce the initial changes in the LED. The ambient temperature of the standard LED must be controlled. At 25 °C. In the revised version, the addition of a temperature-controlled socket in the Annex 4 (a lighting fixture with a chip temperature control function) indicates that the LED needs to reach the thermal equilibrium state under a constant current (hopefully at least Lamp measurement after 5 minutes).