Standards and detection technologies are important levers to lead the development of the semiconductor lighting LED industry. In recent years, with the development of the LED industry, the standards for LED applications, such as devices and modules, to lighting and display applications have developed rapidly. International standards organizations have successively issued relevant standards. China has also tracked and participated in actively leading international standards, especially in the international standard of photobiosafety measurement of lamps and lamp systems. At the end of July this year, the International Organization for Standardization (IEC) IEC approval was led by China, and Hangzhou Zheda Tricolor Instrument Co., Ltd. The unit of the international standard project leader has achieved zero breakthrough in the formulation of China's leading international standards in the field of lighting.
The International Organization for Standardization (IEC) is the first-level technical advisory body of the United Nations. The IEC standard is the most important trade technical document of the WTO. China's lighting optical detection technology has been internationally recognized, and has begun to lead the IEC optical measurement standard, which will promote the international development of China's semiconductor lighting LED detection equipment.
In terms of LED detection technology, the characteristics of LED products are quite different from those of traditional light sources. LED illumination has a close relationship with junction temperature. In the optical and optoelectronic parameter testing of LED products, changes in ambient temperature, heat sink or housing temperature will change the junction temperature of the LED, which will affect the light output. In the photometric test of LED lamps, it is often that the light-emitting device and the lamp housing are inseparable, and an integrated test is required, usually using an absolute photometric method. The blue light of some high-brightness LEDs can cause photochemical damage to the human retina. According to the IEC 62471 "Photobiosafety of Lamps and Lamp Systems" series of standards, the test of photochemical damage of LED products is also one of the hotspots of the industry. In addition, LED products have long life characteristics, we can not perform long-term ignition test like ordinary lighting products, we must use certain accelerated test methods to predict the effective life of LED products, such as the US "Energy Star" using LM80 standard, China is developing The LED life-sustaining test method standard.
Therefore, in recent years, the international development of LED product performance measurement technology and testing equipment has been rapid. In China, with the rapid development of the LED industry, the innovation capability of detection technology and equipment has been significantly improved, and a series of advanced detection equipments that meet the urgent needs of the current industry have been introduced; especially in the optical and energy efficiency detection of LED products, and the spatial light distribution measurement of lamps Advanced testing equipment with international competitiveness has been developed in terms of accelerated test testing of life and safety detection of photobioradiation.
I. Optical and energy efficiency testing of LED products
Temperature control is important in performance testing of LED products. According to the relevant standards at home and abroad, the LED device generally controls the junction temperature or the hot spot temperature of the housing; for the LED module, the hot spot temperature on the heat sink of the module is controlled; and for the LED application product, the ambient temperature is used as a reference. Therefore, in the optical and energy efficiency testing of LED products, the temperature control method in the test equipment is very important for LED devices, modules and application products.
Some LED products have strong beam directivity. When measuring in the integrating sphere, the beam projection area and screen position are sensitive. The IESNA LM79 standard and the CIE 127 technical report are all specified. It is recommended to use a higher spectral reflectance. 1 ball inner wall coating material. NIST in the United States is pushing the international LED standard test method standards, and is at the forefront of the world, and puts extremely high demands on test equipment. The constant temperature integrating sphere in Figure 1 is an LED standard test equipment developed by Zhejiang University Tri-Color Co., Ltd. for NIST of the National Institute of Standards and Technology. It can realize constant temperature testing for three types of LED products such as LED devices, modules and application products.
Second, the spatial light distribution detection of LED lights and lamps
A distributed photometer is a photometric measuring device that measures the spatial luminous intensity distribution of a light source and a luminaire. Figure 2 is the principle structure of a mirror distribution photometer recommended by the International Commission on Illumination CIE 70 technical document. The mirror is always rotated around the central axis. A series of astigmatism can be accurately set between the mirror and the photometric detector. Light, very effective in eliminating stray light. This kind of distribution photometer has been adopted by more than 100 laboratories around the world because it is suitable for spatial light distribution measurement of various complex beams, and it is currently used first. This kind of mirror distribution photometer is also used in several national laboratories in China.
In recent years, with the rapid development of LED technology, the measurement of spatial light distribution of LED products has attracted more and more attention at home and abroad. Compared with traditional light sources and lamps, LED lighting products often have more complex beam distributions, which may have a certain spatial chromaticity difference. Therefore, new requirements are placed on the measurement of spatial light distribution of LED products, not only to test the spatial light of LEDs. Strong distribution, while measuring spatial chromaticity unevenness distribution. In addition, for many laboratories, space sites restrict the application of high-performance equipment. In order to save space, China has also developed a distributed photometer using two mirrors.
The tracking mirror type distribution photometer shown in Figure 3 is a large-scale photometric test equipment independently developed by China. It draws on the idea of ​​optical tracking measurement in liquid crystal display motion artifact measurement, and solves the problem that the measurement beam axis is not fixed, the stray light difference is eliminated, or the photodetector moves in space in several circular motion mirror type photometers. A series of questions. At the same time, it combines the advantages of a central rotating mirror type photometer and a circular motion mirror type photometer. The position of the lamp remains unchanged during the measurement. The measuring beam is perpendicular to the detector, and the position of the photodetector remains fixed. The multi-noise astigmatism diaphragm set in the middle can almost completely eliminate the stray light reflected from the test room floor, wall and ceiling. At the same time, through the specially designed new high-precision colorimetric measurement system, the spatial light color distribution of LED modules or lamps can be accurately and quickly measured. The distribution photometer has a wide test range, small footprint and high measurement accuracy, and meets the measurement requirements of international standards such as CIE NO.70, CIE 121 and BS EN13032.
