What is a LED ?!

A light-emitting diode [LED] is a semiconductor device. You can see it as an electronic device that permits current to flow in one direction. And it illuminates when electricity passes through it.

A pixel is a point of light and the smallest element of an LED display. An LED display is manufactured by an array of pixels. Pixels are capable to present letters, graphics, animations and videos.

Pitch is a terminology to determine the resolution of the LED display. In LED displays, pitch refers to the distance between the centers of two adjacent pixels, and expresses in millimeters.

The smaller the pitch size, the higher picture resolution will be represented because of more pixels per area. On the contrary, the bigger pitch size, because of less pixels, will represent lower picture resolution.

Common brightness requirements as below:

1. Indoor: >800CD/M2

2. Semi-indoor: >2000CD/M2

3. Outdoor [locate south, face north] >4000CD/M2

4. Outdoor [locate north, face south] >8000CD/M2

1. Unique Double-side Display, Rhombus Display, Irregular Display

2. Magnetic buckle for fast connection of screens

3. Convenient maintenance by realizing single dot replacement

4. Customized pixel pitches, more creative possibility of artistry

5. Lightweight, super-thin, easy to take in & down by one person

6. Protection level is at least IP65, available for indoor, rental & outdoor use

7. Humanized operating interface with breakdown indicator light

The methods to improve LED brightness: 1. To use the light effectively. In other words, to increase the amount of light that irradiate towards the needed direction. In this method, light wave control technology is used. Through a better design of the optical structure shaped by the packaged epoxy resin, the light can be controlled to shine towards expected direction, thereby improving the brightness of LED; 2. To increase the light output of the chip itself: light output can be increased through improving the luminescence efficiency of the chip’s active layer or improving the external light extraction efficiency by optimizing chips’ shape or making larger scale chips that run high density current.

If the brightness of LED display runs under expectation, methods listed below can be used: 1. To alter the current magnitude that runs through the LED. Generally, LEDs allow a 20 milliampere operating current continuously. Only red LED has saturation phenomenon, other LEDs’ brightness are in direct ratio with the current amount that runs through them. 2. To realize gray scale control through adopting PWM [Pulse-Width Modulation] method. That is to change the width of the light pulse [duty cycle)] periodically. If the time for the relighting cycle is short enough [in other words, the refresh rate is high enough], the dithering of the luminescence pixel can not be felt by eyes thanks to the visual persistence trait. As it is more adaptive to adopt digital control to realize PWM, meanwhile, as microcomputer is widely used to provide the content to display in LED screens, nearly all of the LED control systems are composed by main controller, scanning board and display control device. Main controller firstly captures data of all colors’ brightness in one particular screen image from the display adapter, then to distribute the data to the scanning boards. Each scanning board takes charge of certain rows of the LED display and the LED display control signal in each row can be transmitted in serial mode.

Currently, there are two serial modes to transmit display control signal. One way is to make centralized control of each pixel’s gray scale in the scanning board. More detailed steps: the scanning board analyzes the data of each row of pixel received from the controller [PWM process], then the board will transmit the open signal of each row to corresponding LED light, controlling each LED to be lit on or to keep off state. The signal is transmitted in serial mode and in the form of pulse [the pulse signal will be 1 if it indicates LED to turn on, contrary, the signal will be 0]. The device used in this method is less, but the data amount being transmitted is comparatively larger.

In every relighting cycle, the gray scale level is in direct ratio with its pulse amount for each pixel, that is to say, 16 gray scale levels need 16 pulses and 256 gray scale levels need 256 pulses. As in LED display, the working frequency for the devices is limited, only 16 gray scale levels is achieved generally. 3. The serial transmitting content for the scanning board is not the on or off signals of each LED, but an eight-bit binary brightness value. If every LED has its distinct PWM to control its lighting time, a pixel under 16 gray scale levels need only 4 pulses and 256 gray scale levels need only 8 pulses in one relighting cycle, reducing serial transmission frequency greatly. Through this gray scale decentralized control method, 256 gray scale levels control can be achieved easily.

The quality of LED Displays can be identified from the following aspects:

The white balance effect is one of the most important indicator in the display. Chromatics taken in the proportion of red, green and blue colors will show 1:4.6:0.16 pure white, if the actual proportion of the deviation of the white balance of a little deviation occurs, and generally pay attention to whether the white bluish, partial yellow-green phenomenon. The white balance is good or bad by the display control system, the die also have an impact on the reduction of color.

LED display screen surface flatness to within ± 1mm. To ensure that the displayed image is not distorted, partial raised or recessed will lead to the display viewing angle of dead ends. The quality of flatness is determined mainly by the production process.

Indoor full color display brightness in 800cd/m2 above and outdoor full color display brightness to 1500cd/m2 above in order to ensure the normal work of the screen. Otherwise it will not see the displayed image. The viewing angle of audience directly determines the size of the viewing angle of display.