|How to control and improve the quality of LED full color display|
Full-color LED display screens are widely used in advertising media, traffic information, stadiums and other large indoor and outdoor video displays because of their irreplaceable advantages in terms of large size, high brightness and environmental adaptability. With the rapid improvement of LED chip technology, LED packaging technology, LED display manufacturing technology and further price reduction, full-color LED display is in the critical period of cost-effective adjustment. Li Mantie, general manager of Shenzhen Lehman Optoelectronics, put forward his own views when talking about the issue of “how to control and improve the quality of LED full-color display”.
Full color display dedicated LED selection
LED devices are the most critical components of full-color LED display wall for three reasons. First, LEDs are the most used key components in full-color screens. Thousands to tens of thousands of LEDs are used per square meter. Second, LEDs are The main body that determines the optical display performance of the whole screen directly affects the audience's evaluation of the display screen; again, LEDs account for the largest proportion of the overall cost of the display, ranging from 30% to 70%.
The choice of LED determines the quality of the entire display by more than 50%. If the LED is not selected, the other parts of the display will not be able to compensate for the defect in the quality of the display.
An important indicator reflecting the quality of LEDs for full-color LED displays:
1, failure rate
Since the full-color display is composed of tens of thousands or even hundreds of thousands of red, green and blue LEDs, the failure of any color LED will affect the overall visual effect of the display. In general, according to industry experience, the failure rate before the LED display starts to assemble to aging 72 hours before shipment should be no more than three ten thousandth (refer to the failure caused by the LED device itself).
2, antistatic ability
LEDs are semiconductor devices that are sensitive to static electricity and are highly susceptible to electrostatic failure. Therefore, antistatic capability is critical to the life of the display. In general, the human body electrostatic mode test failure voltage of LED should not be lower than 2000V.
3, attenuation characteristics
The red, green, and blue LEDs all have the characteristic of attenuating the brightness as the working time increases. The advantages and disadvantages of LED chips, the quality of auxiliary materials and the level of packaging technology determine the attenuation speed of LEDs. In general, after 1000 hours and 20 mA ambient temperature lighting test, the attenuation of red LED should be less than 10%, and the attenuation of blue and green LED should be less than 15%. The consistency of red, green and blue attenuation is displayed for full color LED. The white balance after the screen is greatly affected, which in turn affects the display fidelity of the display.
LED brightness is an important determinant of display brightness. The higher the brightness of the LED, the larger the margin of current used, which is beneficial for saving power and keeping the LED stable. LEDs have different angle values. When the brightness of the chip is fixed, the smaller the angle, the brighter the LED, but the smaller the viewing angle of the display. Generally, a 100 degree LED should be selected to ensure a sufficient viewing angle of the display. For displays with different dot pitches and different line of sight, a balance should be found in brightness, angle and price.
The full-color display is composed of countless red, green and blue LEDs. The brightness and wavelength consistency of each color LED determine the brightness consistency, white balance consistency and uniformity of the entire display. Sex. In general, display manufacturers require device vendors to provide LEDs with a wavelength range of 5 nm and a brightness range of 1:1.3. These specifications can be achieved by device suppliers through a spectral color separation machine. The consistency of the voltage is generally not required.
Since the LEDs are angled, the full-color LED display panel also has angular orientation, that is, the brightness is increased or decreased when viewed at different angles. In this way, the angular consistency of the red, green, and blue LEDs will seriously affect the consistency of white balance at different angles, directly affecting the fidelity of the display video color. To achieve the consistency of brightness changes of red, green and blue LEDs at different angles, it is necessary to strictly carry out scientific design on the design of package lens and raw materials, depending on the technical level of the packaging supplier. In the normal direction, the white balance is good. If the angle of the LED is not consistent, the white balance effect at different angles of the whole screen will be bad. The angular consistency characteristics of LED devices can be measured by the LED angle comprehensive tester, which is especially important for medium and high-end displays.