In the acceptance of an outdoor LED (semiconductor light-emitting diode) display device, the acceptance of the specification is completed in accordance with the regulations, and the final critical procedure is entered.
The vision of the owner unit and related experts are focused on the TV content of the screen, for a moment, into the discussion:
“The screen brightness doesn’t seem to be enough, the color is not very bright,†some experts said.
“The font is not clear and looks a bit fuzzy.†Another expert spoke.
“I don’t think the screen surface is flat enough. Some places seem to lack color?†Someone asked.
"The contract stipulates that the screen playback effect can reach the TV effect, and the actual effect of the big screen is far worse than the TV effect!" The excited voice of the owner made the atmosphere of the scene extremely extraordinarily tense.
The technical personnel of the project contractor came together. After some discussion and technical operation, according to the contractor's suggestion, the acceptance personnel stood at a certain distance in front of the screen, and the reopened screen began to play a new round of programs. First of all, the video animation is played. The color displayed on the big screen is dazzling and the font is very clear. Then the video program is played, the white clouds are blossoming, the green grass is green, and the bright flowers are gorgeous. The project acceptance passed smoothly!
Guan Jizhen, the vice chairman of the led display application branch of China Optical Optoelectronics Industry Association and the general manager of Beijing Sitong Intelligent Transportation System Integration Co., Ltd., told the story in an interview with China Electronics News. Guan Jizhen emphasized that the above scenarios are not uncommon in the acceptance of LED display application projects. In recent years, with the expansion of the field of application of LED display applications, the acceptance of products and projects has been objectionable and even the situation of the courts has been heard. One of the crux of the problem lies in the difference in understanding of product performance and quality.
Starting with the display app
Among the information obtained by human beings, the proportion of information obtained through the viewing of the human eye is the largest. However, due to the complexity of the human visual sensory effects, the standardization problem of display products that provide human perception information becomes very complicated.
According to Peng Wanhua, secretary general of the Optoelectronic Devices Branch of China Optical Optoelectronics | Laser Device Industry Association, the main technologies and industries of LED have developed very rapidly in recent years, and their applications have been expanding. From the earliest and most widely used LED display screens to the present The hotter semiconductor lighting, the wide variety of products, there is no need to have relevant technical standards and product standards. Especially in the field of semiconductor lighting, relevant organizations at home and abroad are actively organizing and formulating semiconductor lighting technology standards, and many problems have been encountered. However, as market demand grows, it is urgent to accelerate the development of semiconductor lighting technology standards.
Mass production applications drive and influence the development of product standards. LED display is a more obvious example.
Before 1995, the LED display, which is a representative product of LED display applications, developed rapidly, but at that time, there was no industry norm and standard for the production of LED display. In 1996, the former Ministry of Electronics commissioned Beijing Lantong Company to formulate the "General Specification for LED Display". In January 1998, the "General Specification for LED Display" was officially released as an electronic industry standard, and the standardization work of the LED display industry began to be standardized. At the beginning of 1998, China Optoelectronics Optoelectronic Devices Branch officially established the LED Display Professional Committee. After the establishment of the industry association, it actively carried out work in guiding the development of the industry, developing communication and coordination of optoelectronic devices and LED display product technology and testing standards. In 1999, the LED device and application seminar was held in Kunming, and Nanjing Luopu Company was commissioned to draft the "LED Display Detection Method". After the organization discussed and revised, it was officially issued in August 2000, and was a member of the LED Display Professional Committee. The unit is trial.
In 2003, the revised "General Specification for LED Display" and "Test Method for LED Display" were officially released as the industry standard of the Ministry of Information Industry. At the same time, sports, transportation, railway and other industries have also released a series of professional standards for industrial applications.
Actively illuminated LED display applications are widely used in many fields and are one of the effective means for modern society to publish and provide information. Guan Jizhen emphasized that the standards for LED display application products have actually been paid more attention and attention to the industry. With the development of the industry, it has been continuously developed and improved from scratch. The effect of LED display is highly correlated with the application environment and needs. The device material, viewing angle, line of sight, dot matrix, etc. all directly determine the quality of the display. The content of the program played also has a direct impact on the display effect. Without clear technical definitions and standard conditions, it is difficult to objectively evaluate the display effect.
The reliability standards of LEDs are also critical to the application. Ding Chenglong, deputy director of the Discrete Device Branch of China Semiconductor Industry Association and deputy general manager of Beijing Changdian Zhiyuan Optoelectronics Co., Ltd., said in an interview with the reporter of China Electronics News: "I have repeatedly suggested and called on various occasions to establish China as soon as possible. LED reliability standard system. In 2001, we went to the scientific research department of Beijing Traffic Management Bureau to investigate the application status of LED on traffic lights. We received our researchers pointing to the traffic lights placed on the roof and told us that this was sent by a certain enterprise in the south last year. The traffic light samples coming. In less than a year, can you still see the color? Looking at the faint red, green and blue, we really don’t know what to say. Now many companies clearly understand their LED specifications. The print has a lifespan of 100,000 hours. I really don't know what the experimental basis for this 100,000 hours is. And we learned that in 2005, when a US company bought their 5 watt high-power white LED device, the company would clearly tell the user. The life of this product is 3,000 hours. I know that this is because they come from a large amount of experimental data and responsibly inform customers, otherwise they have faced The possibility of huge compensation."
For the display application, Ding Chenglong told the reporter a story like this: "At the beginning of 2004, we went to a well-known LED large-screen company in Beijing to investigate their LED device usage. They said that they use blue-green LED on the big screen, only use Japan Day. The device of Asia. The reason is that the pipes of Nichia are not bad, and the pipes of other companies are bad. It is no wonder that the pipes of Nichia are sold well and sold well. Think about it too, a large LED screen, using tens of thousands and hundreds of thousands. Only LED devices, in the process of welding, assembly, debugging, splicing, installation, which part of the device is damaged, it is very difficult to do. Not to mention that after the large screen is placed in place, several LED devices are broken, what do you do? I would rather have a more expensive device, but I don’t know how to do it better than the latter."
In fact, it involves a reliability issue. The reliability of LEDs is that users should have reliable, durable, long-lasting, and non-destructive performance when using LEDs. LED is an important branch of semiconductor discrete devices. It is inseparable from the inherent heat of semiconductor devices, the increase in leakage of PN junctions after temperature rise, the change of barrier, the degradation of function (lower brightness) and even permanent damage (decreased luminous efficiency) until damage. Therefore, the internal quantum efficiency of the LED epitaxial wafer is improved, and the light extraction (also known as external quantum) efficiency of the LED epitaxial wafer and the chip is improved, that is, the electrical energy input to the LED is converted into light energy instead of thermal energy as much as possible, thereby Reducing the temperature rise of the LED, and good heat dissipation should run through all aspects of the LED epitaxial wafer, chip, package and even application, which is the fundamental measure to improve the reliability of the LED. China's energy-saving lamps have experienced the problem of saving electricity and saving money for a long time. LED will not take the old road of energy-saving lamps, the key is whether we can quickly establish a series of reliability standards for LEDs in China, and strictly implement them.
For LED application product standards, Mr. Yan Tongsheng, Chairman of Hangzhou Zheda Tri-color Instrument | Instrument Co., Ltd. introduced that in the LED application product standards, the Ministry of Information Industry, the Ministry of Communications, the Coal Machinery Industry Association, the Light Industry Association and other relevant ministries have LEDs. The standards are being developed, such as LED light source for miner's lamp, LED road traffic induced variable sign (completed) and so on.
According to the current LED technology level and performance, LEDs are mainly concentrated in indicators, traffic lights, display screens, mobile phone backlights, landscape decorative lighting, local lighting and other applications, currently in LCD backlights and floodlights, street lights and other general lighting It has shown a clear application momentum.
Therefore, the development of LED application product standards will be the focus of work in the next few years.
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