LED testing equipment technology, due to the characteristics of LED products with conventional light sources. The luminescence of the LED junction temperature is closely related to LED products, optical and opto-parametric test, the ambient temperature, the radiator or shell temperature change will change the LED junction temperature, which affects the light output. Test of the luminosity of the LED lamps, often light-emitting devices and lamps shell can not be separated, you need one test, usually using the absolute luminosity measurement method. The high brightness LED's blue light will cause human retinal photochemical damage, according to the IEC62471 "lamps and lamp systems biosecurity" series of standards, testing of the LED products of photochemical damage, is currently one of the industry focus of attention. In addition, the characteristics of the LED products with long life, we are not like general lighting products for long-term ignition test, must be a certain degree of accelerated test methods to predict the effective life of the LED products, such as the U.S. "Energy Star" LM80 standard, being developed in China LED life accelerated test method standards.
Therefore, in recent years in the rapid development of LED product performance measurement techniques and testing equipment. In China, with the rapid development of LED industry, the innovation capability of the detection technology and equipment improved, the introduction of a series of advanced testing equipment to meet current industry urgently needed; especially in the light distribution of LED products, optical and energy efficiency testing, lamps, space measurement, the acceleration test for detection of life, bio-optical radiation safety testing, the development of internationally competitive advanced testing equipment.
An LED optical and energy efficiency testing
LED product performance testing, temperature control is very important. According to the relevant standards at home and abroad, LED devices generally control the junction temperature or the shell of hot spot temperature; LED module, control module heat sink on the hot spot temperature; LED application products, while the ambient temperature as a benchmark. Therefore, detection of the optical and energy efficiency of LED products, LED components, modules and applications, test equipment, temperature control is very important.
Beam directivity of LED products in the integrating sphere measurements, the beam projected area, more sensitive to block the screen position, the IESNA LM79 standards and CIE127 technical report made provision, we recommend using a higher spectral reflectance ratio ball inside wall coating materials. U.S. NIST in promoting international LED standard test method standards, walking in the forefront of the world, also made high demands on test equipment. Thermostat integrating sphere in Figure 1, the tri-color Zhejiang University for the U.S. National Institute of Standards and Technology Research Institute, NIST developed the LED standard test equipment, thermostat test of LED devices, modules, applications, and three types of LED products.
Second, the LED lamps and luminaires spatial light distribution detected
The distribution of photometric measurement of the light source and lighting space luminous intensity distribution of the photometric equipment. Figure 2 is a mirror distribution photometer principle structure recommended in the International Commission on Illumination CIE70 technical documents, the mirror is always around the center axis of rotation between the mirror and photometric detectors can accurately set up a series of elimination stray bare Lanna, very effectively to eliminate stray light. Distribution photometer more suitable for a variety of complex beam spatial light distribution measurement, has been over one hundred laboratories around the world with the current usage. Our country's several national laboratories also used the this mirror Goniophotometer.
In recent years, with the rapid development of LED technology, LED space optical distribution measurements more and more international and domestic concerns.Compared with conventional light sources and lamps, LED lighting products are often more complex beam distribution, there may be some space for chroma difference, therefore the spatial light distribution measurement of LED products to the new requirements, not only to test the LED spatial light The intensity distribution space chromaticity to be measured non-uniformity distribution. In addition, many laboratory, space venue has restricted the application of high-performance devices, in order to save space, China has also developed the distribution of two mirror photometer.
Figure 3 shows the tracking mirror distribution photometer, China has independently developed a large photometric test equipment. It draws on the LCD motion artifacts measurement of optical tracking in the idea of measurement, to solve several circular motion mirror distribution photometer measuring beam axis is not fixed, eliminate stray light poor, or photoelectric detectors in space movement and other issues. Combined with the advantages of a central rotating mirror distribution photometer and circular motion mirror the distribution of photometric measurement of the lamp position remains unchanged, the measuring beam at normal incidence detector, photoelectric detectors to maintain a fixed position; in the optical path set more than eliminate stray light aperture, able to almost completely eliminate the test chamber floor, wall and ceiling mutual reflection of stray light. At the same time through a specially designed new high-precision color measurement system, space, light and color distribution can be achieved quickly and accurately measured the LED module or lamps. Photometer test of the distribution of a wide range of small footprint, high accuracy, meet the requirements of CIENO.70, the CIE 121 and BS EN13032 and other international standards of measurement.
LED light biological radiation safety testing and evaluation
With the development of biological research in light, the optical radiation safety has drawn increasing attention. LED chip power and external quantum efficiency is greatly improved in recent years the rapid development of high-power blue LED chip has been widely used in general lighting areas; the development of high-power multi-chip integration and the second optical technology, the LED of optical radiation dangers of even more concern. Human retinal optical radiation safety assessment of the damage, you need to measure the harmful radiation of 300nm ~ 700nm Blu-ray photochemical brightness and 380nm ~ 1400nm retinal thermal hazard radiance, and the need to comply with the conditions of measurement is similar to the human eye structure, the testtechnology and equipment put forward higher request. Figure 4 is created by our experts at the U.S. National Institute of Standards Technology NIST radiation safety tests based on human retinal radiance of LED light biological devices. Figure 5 is a LED light in China with independent intellectual property rights of biological radiation safety testing and evaluation system is mainly used for optical radiation safety testing and rating of the optical radiation source in the class a variety of non-laser light sources, lighting and electrical products. China is not only leading the LED light biological radiation safety measurement methods in international standardization activities, and testing equipment to go in the ranks of the leading international.
Fourth, LED life accelerated test
LED life of the product can reach tens of thousands of hours, how to conduct the assessment of product life, the global LED industry are very concerned. Feasible method is based on the LED junction temperature accelerated thermal stress tests. The LM-80 standard provides for three types of test temperature: 85 ° C, 55 ° C, and custom (25 ° C), the LED light in several temperature decay curve, the test time of 6000 hours. China is drafting the LED life accelerated testing standards and no specific provision in the test temperature, accelerated testing thermal stress generally be selected based on the LED structure of the material properties. Figure 6 is China's own R & D LED life and reliability of accelerated test device can simultaneously carry out the trial of three temperature zones, each temperature zone of 30 samples of the test. Detection system in real time to detect light intensity and color coordinate each test LED samples under the provisions of electrical parameters (forward current) decay curve over time. At the same time, real-time recording junction temperature (case temperature) and electrical test parameters automatically given the parameters of the useful life of the LED.
The continuous development of the potential and advantages of the LED, the next five to fifteen years will be LED lighting from the lighting of the traditional (alternative) into the revolutionary period of development of the (humane) lighting, the industry should be concerned about the trend of international standards to meet the new industrydevelopment opportunities and challenges. China in international standardization activities, from early tracking and equivalent international standards, as well as the beginning of this century began to actively participate in the formulation of international standards, today some of the leading international standards. After the turbulence of the international financial crisis, China's position in the international arena is undergoing new changes, the right to speak of China's semiconductor lighting international standards is also growing, in the future international trade will have a major impact on China. China's semiconductor lighting detection technology and equipment has been significant progress, increasing international status, especially in LED testing the formulation of technical standards, China's dominant position in certain key international standards has been affirmed.