Evolution history of led displays from monochrome to full-color to small-pitch

An LED screen (LED display)is a device that transmits and displays visual information, in which the pixels are semiconductor LEDs.

LEDsare semiconductor devices that emit light due to the passage of current. The color of the light emitted by the LED can be red, green or blue, depending on the wavelength. In order to make the LED display full color, different colored LEDs need to be used.

The main advantages of LED display:

- Safe-Suitable for indoor and outdoor use
- High brightness-excellent visibility even in bright sunlight
- Long service life

This is why LED screens have become common.

Pixels are the smallest element of an image. Pixel diameter is 1.9-80 mm. Each pixel contains one to eight LEDs (Figure 2).

In a full LED display, each pixel contains green, blue and red LEDs. There are usually 8 LEDs in a pixel, but there can be more. The built-in processor produces all primary colors and all white tones.

Pixel pitch is the gap between the centers of two adjacent pixels. The higher the resolution of the LED display, the higher the image quality. To do this, pixel spacing must be minimum.

The number of LEDs per pixel refers to the position and number of blue, red and green LEDs in a pixel.

LED screen modulesare structural elements that combine pixels into a standard size. Different manufacturers produce modules of different size. Main module size: 160*160 mm, 130*65 mm, 256*256 mm, 320*160 mm. ETC。The module itself is a small plate with built-in LEDs on the front and built-in electronic components on the back. A module consists of multiple pixels. The number of pixels is determined by their diameter. Normally, when the LED fails, the module needs to be replaced. The spare parts kit contains a certain number of modules.

LED cabinetsare large prefabricated elements (also called panels) that include a certain number of modules. Module parameters are multiples of box parameters. For example, a panel with a size of 960x960mm consists of 36 (6*6) modules, each module having a size of 160* 160mm. Another example: the panel size is 1024*768mm, contains 12 (4*3) modules, and the size is 256*256 mm.

The size of the cabinet body is 0.5- 2m and the thickness is 175mm. The photo shows the front and rear views of the cabinet. These panels are fastened to each other without gaps to form a strong screen fabric. The cabinet must contain a power supply.

This cabinet structure makes it possible to design screens of various size. At the same time, the system remains very flexible-services can be provided to individual modules, which greatly simplifies services.

The viewing angle of an LEDis a characteristic of an LED that determines the maximum deviation in one direction or the other when the LED is perceived to be bright enough. If viewed perpendicular to the surface of the LED display, the image on the display will be as bright as possible. When you change the viewing angle, the viewing brightness and color rendering become lower. The LED angle size can vary within a small range-from 70 degrees to 120 degrees. In this case, the measure of the optimal viewing angle is determined by the angle at which the brightness is reduced by at least a factor.

Screen viewing angle-The angle at which the image brightness is twice as low as the brightness available when viewing the screen at right angles. The viewing angle range of the screen is 100-160 degrees.

Graphics resolution-The number of pixels on the screen. Generally, the graphics resolution of the screen is expressed as follows: horizontal screen resolution X vertical screen resolution. For example, 500x400.

Resolutionis the number of pixels per square meter of the display.

Standard brightness-The brightness of the light emitted by the module. Light intensity is measured in candelas per square meter (NIT). Generally, the brightness requirement for indoor screens is 1200-3000 cd/m2, and the brightness requirement for outdoor screens is 6500-10000 cd/m2.

Required power (power consumption): Peak power 750-900 W/m2, average power- 250-300 W/m2.

Fixed outdoor screens weigh 60-70 kg/m2, but indoor and rental screens weigh much less. Flexible mesh screens with large pitches have the lightest weight. Such screens are usually used in theater stage backgrounds, street decorations and other places where image quality requirements are not high (Figure 5)

How to choose the LED screen format?

Select an LED screen format that matches common formats for videos and computer programs: 4:3 or 16:9。Otherwise, it will be difficult to write content.

The screen size corresponding to the 4:3 format is arranged in descending order:

• 8x6
• 6x4
• 4x3
• 3×2.25
• 2 1.5 meters

The corresponding screen size for the 16:9 format is:

• 8×4.5
• 6×3.375
• 4×2.25
• 3×1.68
• 2x1.125 meters

What should I pay attention to when selecting pixel spacing?

1. If the LED screen format is 4:3, then for a high image quality LED screen, the graphics resolution parameter must be greater than 256x192 pixels. For example, if the screen size is 6x4 meters, the pixel spacing should be less than 23.5 millimeters, and if the screen size is 3x2.25, the pixel spacing will be less than 11.75 millimeters. Obviously, the smaller the step size, the higher the image quality.
2. Viewing distance-the most comfortable viewing distance. Measure in meters. If the viewing distance is less than the necessary distance, then people will see the pixel structure of the image, which will naturally stimulate them. For example, if the pixel spacing is 16 mm, the shortest distance for a satisfactory image is 16 m, and if the pixel spacing is 4 mm, the viewing distance must be at least 4 m.

The maximum viewing distance for an image to be satisfactory is calculated by the following formula: Maximum distance in meters = 6V, where B is the screen width in meters.

On outdoor LED-backlit screens (Outdoor), pixel spacing of 10 to 40 mm is most commonly used. For outdoor large screens, the most commonly used spacing is 16 mm. For internal screens, use a spacing of 1.9-10 mm. Generally speaking, the smaller the spacing, the higher the quality of the screen, and correspondingly, the higher the cost. For flexible mesh screens, the spacing between pixels can be 10 mm or more depending on customer requirements.

What type of LED should I choose?

The cost of an LED screen is not only affected by the distance between pixels, but also by the type of built-in LED.

Japan's Nichia LEDs are rightfully considered to be the highest quality and most expensive, followed by Cree in the United States, then Taiwan's LED Crystal Optoelectronics and Samsung, and improved China's Multicolor and Absen. By the way, China Silan Microelectronics finally listed the most common LED types. The costs of various types of LEDs with similar technical characteristics may differ several times. The higher the quality of the LED, the more reliable and durable it will be, and the more it can meet brightness and color rendering standards.

LED screen manufacturing technology:

A variety of LED layout methods can be used to produce LED displays. The choice of layout method depends on the type of screen.

An LED cluster is an emitting device composed of the required number of LEDs. The clusters are housed in a light-tight, water-resistant enclosure. A cluster is equal to one pixel in the image. This layout method is used for the manufacture of large external screens.

LED Matrix-Here the diodes are located on the surface of the screen. In this case, the pixels are not designed, but each LED corresponds to a specific pixel. This production technology is used for the production of indoor LED displays.

Virtual pixels. The characteristic of this layout method is that LEDs are not assigned to specific pixels. Special programs use LEDs adjacent to each other to create pixels. Pixels can be combined horizontally and vertically, resulting in the effect of doubling the number of pixels on the screen. Therefore, the screen resolution can be increased several times. The output is a fairly high-quality image.

Surface mount technology. With this packaging method, micro LEDs are contained in a single package and soldered to printed circuit conductors. As a result, a relatively high screen resolution is achieved and the viewing distance is shortened. LEDs are moisture permeable, so such screens are usually used indoors. However, if you use very bright LEDs and moisture-proof fabric, the final screen can be installed outdoors.

How to display images on the screen:

The LED screen is capable of reproducing images from almost all available sources. Source code can be used:

• computers;
• Computer networks (including intranets and the Internet);
• Video conferencing system;
• DVD player;
• Video recorder;
• camera;
• Satellite and cable television;
• Industrial video surveillance system.

How is the LED display controlled?

The control signals sent by the computer are transmitted through a certain number of receiving cards and transmitting cards (receiving cards, transmitting cards), which are included in any LED display.

The screen is controlled by a computer installed with special software that is included in the delivery kit. Depending on the purpose of the screen (external or internal), the control system can be remote or built-in. Because the device supports the TCP/IP protocol, it can also transmit data and control the screen over a radio channel or network. Indeed, there are some shortcomings here. The channel bandwidth for transmitting images must be large.

LED screen installation options

External street screensare either fixed to the walls of the building or"" mounted to the roof using leg-type structures.

As for internal screens, they are usually fixed to the wall, suspended from cables or placed on special brackets. No matter what installation option you choose, you must develop a screen installation project. And in some cases special metal structures are required for installation.

Before installing screens on walls or building roofs, calculations need to be made to eliminate emergencies. For the customer, it is his responsibility to power the screen installation location and obtain all necessary installation licenses.

The use of external screens in Russia has its own characteristics. First, air conditioning or ventilation systems need to be used to eliminate the possibility of equipment failure when operating in extremely low or high temperatures.

Where can LED displays be used?

Due to their high brightness and large image size, LED screens are used by organizers of various events that need to attract large audiences. In most cases, LEDs