Brief analysis of factors affecting the quality of LED display
Some time ago, I pushed an article on LED lamp inspection by the staff of the Entry-Exit Inspection and Quarantine Bureau. Let's take a look at what are the requirements for the LED display in the eyes of the staff of the Entry-Exit Inspection and Quarantine Bureau. China's LED display technology has gradually developed and matured, but due to the influence of many factors, there are still many problems in the quality of newly installed displays. Some display screens turn off lights and mosaic phenomena are serious; Some screen images are blurry and rough; Some displays require endless repair and maintenance. One of the main reasons for these undesirable phenomena is that the quality of LED displays is not in place,
Some time ago, I pushed an article on LED lamp inspection by the staff of the Entry-Exit Inspection and Quarantine Bureau. Let's take a look at what are the requirements for the LED display in the eyes of the staff of the Entry-Exit Inspection and Quarantine Bureau.
China's LED display technology has gradually developed and matured, but due to the influence of many factors, there are still many problems in the quality of newly installed displays. Some display screens turn off lights and mosaic phenomena are serious; Some screen images are blurry and rough; Some displays require endless repair and maintenance.
One of the main reasons for these undesirable phenomena is that the quality of LED display is not in place, at present, the quality of LED display in China needs to be further improved. Combined with my experience in the Entry-Exit Inspection and Quarantine Bureau, this article briefly introduces the quality standards of China's LED display industry, and on this basis, a single brief analysis of the factors affecting the quality of LED displays, hoping to promote the improvement of LED display quality in China.
LED display industry quality standard
"General Specification" is the main technical basic specification of display technology in China. It is fully suitable for LED indoor and outdoor text, graphics, video and other graphic displays. Its content consists of eight parts: scope, normative references, terms and definitions, classification, requirements, inspection methods, inspection rules, packaging, transportation, storage, etc.
The "Requirements" section puts forward 10 main requirements including: LED display hardware environment, LED display software environment, structure and appearance, safety requirements, LED display functions, LED display electrical characteristics, LED display power supply, environmental adaptability and reliability.
Quality requirements for LED displays
(1) Brightness requirements
Brightness is an important indicator of display quality, and the brightness of the display is mainly determined by the luminous intensity of the LED and the arrangement density of the display. Some LED displays are installed on very high exterior walls, and the installation angle of LED screens will also have an impact on people's eyes to judge the luminous intensity of the screen. SJ/T11141-2003. The general specification for LLD displays defines the brightness of LED displays as the intensity of light per unit area of the screen.
LED screen display color has single color, double color and full color three, the use of the use environment to divide can be divided into indoor and outdoor two, and different colors and environments for LED display parameter requirements are also different. The indoor full-color LED display requires a brightness of 800 cd/m2, while the outdoor full-color LED display requires 1500cd/m2, so that the brightness can basically ensure the screen image display policy. In recent years, the various technologies of LED display have been further developed, whether it is the use of materials or the transmission process are more mature, as a result, the LED display luminous efficiency requirements produced by manufacturers have also been greatly improved.
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(2) Chromaticity requirements
LED display has the characteristics of color reproduction. Some manufacturers do not realize the advantages of the wide color gamut of LED displays, blindly pursuing the high brightness of the screen, so the production of LED displays color distortion, dazzling displays, and sometimes information playback will make the audience uncomfortable.
Therefore, when the LED display production needs to evaluate its color indicators, if the color index can meet the corresponding requirements, then the color matching is appropriate and will not cause discomfort. The temperature measurement of the center position of the full-color LED display correlated color temperature and chromaticity coordinates needs to be less than 6500K, which can avoid the color of the full-color LED display is too cold, and the measured color temperature is not greater than the specified range.
(3) Energy efficiency requirements
Different LED displays want to achieve the same display effect, and the power consumption of the screen may be different. In promoting energy saving, emission reduction and green environmental protection today, the energy efficiency requirements of LED displays are also very important.
Energy efficiency evaluation LED products generally use luminous efficiency. The installation and use range of LED display, the measurement of the luminous amount of LED display is extremely difficult, and the brightness is easier. By studying the definition of brightness and luminous flux, the energy efficiency of the LED display is found, and the luminous area of the LED display is multiplied by the hemispherical surface, and the calculation result is the luminous flux.
LED displays are mostly large screens, and there may be some uneven brightness. In order to evaluate the energy efficiency of the LED display in a more objective and reasonable way, the LED display in the bright state, it is necessary to randomly select 9 different points in all directions, and the brightness of the nine points is measured at the same time, and then the average brightness of the LED display is obtained, which is represented by LAV. When measuring the brightness, measure the power consumption of the LED display, and obtain the energy efficiency of the LED display (unit lm/W) according to the formula.
(4) Environmental protection and safety requirements
Because the use of displays is often in different situations, different environments also have different safety requirements for LED displays. The main safety standards are: grounding, leakage current, temperature rise and medium strength. The most important of these four are leakage current and dielectric strength requirements. SJ /11141- 2003T display general specification requires 1.1 times the rated power supply voltage of the standard, the leakage current should not exceed 3.5mA, the power switch connected to the power switch should be tolerant of 1500 V, 1 minute test will not insulation breakdown.
The number of outdoor LED displays is much higher than indoors. The environmental adaptability requirements of indoor display screens are low, while the outdoor display is much higher than the requirements of environmental adaptability. Because it is installed in different regions and the environment is different, the outdoor display screen should be able to withstand the long-term effects of more harsh environments, such as wind, rain, earthquakes, and also ensure normal use in high and low temperature environments.
Conclusion
In China, LED display is widely used in the release of advertisements by major media and information notices of traffic management departments, and has a large audience. Therefore, it is necessary to ensure the quality of LED display screens, and manufacturers must pay attention to LED display brightness requirements, chromaticity requirements, energy efficiency requirements and environmental protection and safety requirements to meet the use requirements and extend the life cycle of products.