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Influence of the LED lamp to the LED display

1、Viewing angle

The viewing angle of the LED display is determined by the LED lamp’s viewing angle. At present, most outdoor LED display use oval LED which its viewing angle is 100° in horizontal and 50° in vertical. Indoor display uses SMD LED which its viewing angle is 120° in horizontal and vertical. The display on the highway usually use round LED with 30° viewing angle because of its Particularity. The display installed on the tall building has higher requirements in vertical viewing angle. Viewing angle and brightness are mutually contradictory, wide viewing angle must make the brightness lower. We must choose the viewing angle according to the exact application.

2、Brightness

Brightness of LED is the important influence factor of the display brightness. The higher the LED brightness, the larger the margin of the available current, this is good for saving power and keeping the LED stable. Different LED has different viewing angle, in the case of chip brightness is changeable, the smaller the angle, the brighter LED, but the smaller the viewing angle of the display. Generally, we should choose LED with 100° viewing angle to ensure enough viewing angle of the display. For different pixel pitch and different viewing distance of the display, we should find a balance point between the brightness, angle and price.

3、Failure Rate

As the full-color display consists of tens of thousands or even hundreds of thousands of red, green and blue LED pixels, the failure of any color LED will affect the overall visual of the display. In general, according to industry experience, the failure rate should less than 3/10000 after 72 hours aging test (referring to the failure caused by LED lamp itself).

4、Anti-static ability

LED is semiconductor device, it’s sensitive to static electricity, can easily lead to static electricity failure, so anti-static ability is crucial to the life of the display. In general, the failure rate of LED’s human body static mode test  should not be less than 2000V.

5、Lifespan

The theoretical life of LED device is 100,000 hours, much larger than the other parts of LED display, so as long as the LED device has quality assurance,  property work current, reasonable PCB cooling design, rigorous display production process, LED devices will be one of the most durable parts in whole display .

LED devices accounted for 70% of the proportion of the price of LED display, LED devices can determine the pros and cons of LED display quality. Our country is not only a big producing country of LED devices, but also an gathering area where LED displays are manufactured. High-tech requirements of the LED display is development trend in the future, high quality requirements of the LED display is not only related to the trend of LED display manufacturers, but also implicated in the development of LED display device manufacturers.

6、Attenuation characteristics

The display brightness will be declined and the display color could be incongruous after long-time working, it’s mainly due to the brightness attenuation of LED devices. LED brightness attenuation will cause display brightness reduction. Red, green and blue LED brightness attenuation inconsistencies will result in LED display color inconsistencies. High-quality LED devices can control the brightness attenuation range well. As 1000 hours normal temperature 20mA standard, Red attenuation should be less than 2%, blue, green attenuation should be less than 10%, so when we design the display, for blue, green LED, we had better avoid using 20mA current, preferably only 70% to 80% of the rated current.

Attenuation characteristic is not only related to  the red, green and blue LED itself, but the use of current, PCB cooling design, the environmental temperature of the display also have impacts on the attenuation.

7、Size

LED device size affects the LED display pixel pitch, that is, resolution. 5mm oval lamp is mainly used for outdoor display above P16, 3mm oval lamp is mainly used for P12, P10 outdoor display, 3528 SMD LED is mainly used for P6, P8 indoor display, 2020 type SMD LED is mainly used for P2, P3 and other indoor display. Under the premise of constant pixel pitch, LED device size increases, it can increase the display area and reduce the sense of grainy when the LED device size increased, however, due to the reduced black area, it will reduce the contrast. On the contrary, when the LED size is reduced, the display area will be reduced, the sense of grainy will be increased, black area will be increases, and the contrast is increased.

8、Consistency

Full-color display is composed of countless red, green and blue LED pixels, the unity of brightness and wavelength for each color LED determines brightness uniformity, white balance uniformity, and color consistency of the entire display. In general, display manufacturers require device suppliers to provide LED in the 5nm wavelength range and 1: 1.3 brightness range, which can be graded by the device supplier through an automatic sorting machine of LED. Voltage consistency is generally not required.

LED has angle, so full-color LED display also has viewing angle, that is, when view from different angles, its brightness will increase or decrease. In this way, the angle consistency of red, green and blue LED color will seriously affect the consistency of different aspects of white balance, which has direct impact on the display video color fidelity. To achieve the brightness diversification’s matching consistency of red, green and blue LED in different angle, we need strict scientific design in package lens design and raw material selection, it depends on the packaging supplier's technical level. For display with good normal direction white balance, if the angle of the LED is not consistent, the white balance of the entire screen from different angles will be bad. The angle consistency characteristics of LED lamps can be tested by LED angle comprehensive tester, it’s particularly important for the medium and high-end displays.



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