Because the LED has an angle, the full-color LED display also has angle directionality, that is, when viewed from different angles, its brightness will increase or decrease. In this way, the angle consistency of red, green and blue LEDs will seriously affect the consistency of white balance at different angles and directly affect the fidelity of video color on the display screen. In order to achieve the matching consistency of brightness changes of red, green and blue LEDs at different angles, it is necessary to strictly carry out scientific design in packaging lens design and raw material selection, which depends on the technical level of packaging suppliers. For the display screen with good white balance in the normal direction, if the angle consistency of the LED is not good, the white balance effect of the whole screen at different angles will be bad. The angle consistency of LED beads can be measured by LED angle comprehensive tester, which is particularly important for medium and high-grade display screens. The key component of full-color display screen is led bulb. All led beads are the components with the highest cost and consumption in LED display screen, which plays a leading role in the quality of LED display screen.
Now let's learn about led beads as the most key component of LED display screen. How to identify the advantages and disadvantages of LED beads?First, LED is the most used key device in the full-color screen machine, and thousands to tens of thousands of LEDs will be used per square meter;Secondly, LED is the main body that determines the performance of the whole screen optical display, which directly affects the audience's evaluation of the display screen;
Third, LEDs account for the largest proportion of the overall cost of the display screen, ranging from 30% to 70%.How to identify the advantages and disadvantages of LED display lamp beads1 Look at the solder joint. The LED lamp belt produced by regular LED lamp belt manufacturers is produced by SMT patch process, solder paste and reflow soldering process
2 Look at FPC quality. FPC is divided into copper clad and calendered copper. The copper foil of copper clad plate is convex. If you look closely, you can see from the connection between pad and FPC3 Look at the cleanliness of the LED light strip surface. If the LED lamp belt produced by SMT process is adopted, its surface cleanliness is very good, and no impurities and stains can be seen4 Looking at the chip and production process of LED lamp, you can't see the difference with your eyes. You should use aging equipment and testing equipment. If you put the LEDs of several manufacturers on the aging instrument and age them with high current for 24 hours or more, you can measure the brightness of the LEDs of several manufacturers to see that the LED has the lowest luminous intensity attenuation and the best quality.
What are the effects of LED beads on LED display1. Perspective
The viewing angle of LED display screen depends on the viewing angle of LED lamp beads. At present, most outdoor displays use horizontal viewing angle of 100 Vertical viewing angle 50 ; Oval LED, indoor display screen is 120 horizontally and vertically; Patch LED. Because of its particularity, the display screen on expressway is generally 30 ; The circular LED of the viewing angle is enough. The display screen on some tall buildings has high requirements for vertical viewing angle. The angle of view and brightness contradict each other, and a large angle of view will inevitably reduce the brightness. The choice of perspective needs to be determined according to the specific purpose.
LED brightness is an important determinant of display brightness. The higher the brightness of the LED, the greater the margin of the current used, which is good for saving power consumption and maintaining the stability of the LED. LEDs have different angle values. When the chip brightness is fixed, the smaller the angle, the brighter the LED, but the smaller the viewing angle of the display screen. Generally, 100 degree led shall be selected to ensure sufficient viewing angle of the display screen. For displays with different point spacing and different viewing distance, a balance should be found in brightness, angle and price.
3. InefficiencyBecause the full-color display screen is composed of tens of thousands or even hundreds of thousands of pixels composed of red, green and blue LEDs, the failure of any color LED will affect the overall visual effect of the display screen. Generally speaking, according to industry experience, the failure rate of LED display screen 72 hours before shipment shall not be higher than 3 / 10000 (referring to the failure caused by the LED bulb itself).4. Antistatic ability
LED is a semiconductor device, which is sensitive to static electricity and easily leads to static failure. Therefore, the anti-static ability is very important to the service life of the display screen. Generally speaking, the failure voltage of LED human body electrostatic mode test shall not be lower than 2000V.5. Life span
The theoretical life of LED devices is 100000 hours, which is much longer than the working life of other components of LED display screen. Therefore, as long as the quality of LED devices is guaranteed, the working current is appropriate, the PCB heat dissipation design is reasonable and the production process of display screen is rigorous, LED devices will be one of the most durable components in the whole display screen. LED devices account for 70% of the price of LED display screen, so LED devices can determine the quality of LED display screen. China is not only a large producer of LED devices, but also a gathering place for the manufacture of LED display screen. The high-tech requirement of LED display screen is the future development trend. The high-quality requirement of LED display screen is not only about the trend of LED display screen manufacturers, but also involves the development of LED display device manufacturers. From the control of LED devices to promote the transformation of China from a large LED display manufacturing country to a powerful LED display manufacturing country.
6. Attenuation characteristics
The brightness of LED display screen will decrease and the color of display screen will be inconsistent after working for a long time, which is mainly caused by the brightness attenuation of LED devices. The attenuation of LED brightness will reduce the brightness of the whole display screen. The inconsistent brightness attenuation of red, green and blue LEDs will cause the inconsistent color of LED display screen, which is the phenomenon that we often say the display screen is spent. High quality LED devices can well control the brightness attenuation. According to the standard of 20mA lighting at room temperature for 1000 hours, the red attenuation shall be less than 2%, and the blue and green attenuation shall be less than 10%. Therefore, 20mA current shall not be used for the design of blue and green LEDs as far as possible, and it is best to use only 70% to 80% of the rated current. The attenuation characteristics are not only related to the characteristics of red, green and blue LEDs, but also affected by the use current, PCB heat dissipation design and the ambient temperature of the display screen.
The size of LED devices affects the pixel distance of LED display screen, that is, the resolution. 5mm oval lamp is mainly used for outdoor displays above p16, 3mm oval lamp is mainly used for outdoor displays of p12.5, p12 and P10, 3528 patch LED is mainly used for indoor displays of P6 and P8, and 2020 patch LED is mainly used for indoor displays such as P2 and P3. On the premise of constant point spacing, the increase of LED device size can increase the display area and reduce the sense of particles, but the contrast will be reduced due to the reduction of black area; On the contrary, the LED size is reduced, the display area is reduced, the particle sense is increased, the black area is increased, and the contrast is increased.
8. ConsistencyThe full-color display screen is composed of countless pixels composed of red, green and blue LEDs. The consistency of brightness and wavelength of each color LED determines the brightness consistency, white balance consistency and chromaticity consistency of the whole display screen. Generally speaking, the display manufacturer requires the device supplier to provide LEDs with a wavelength range of 5nm and a brightness range of 1:1.3. These indicators can be graded by the device supplier through the light and color splitter. Voltage consistency is generally not required.
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