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LED display basics
Nov 18, 2018

LED display terminology
1. What is pixel, pixel diameter, dot pitch pixel: The minimum illumination unit of the LED display has the same meaning as the pixel mentioned in the ordinary computer display; each of the LED display can be called separately controlled by the light unit Pixel. Pixel Diameter: The pixel diameter ∮ refers to the diameter of each LED illuminating pixel, in millimeters. Pixel Spacing: The center distance between two pixels of an LED display is called the pixel pitch, also called the dot pitch. The denser the dot pitch, the higher the pixel density per unit area, the higher the resolution, and the higher the cost. The smaller the pixel diameter, the smaller the dot pitch.

2. What is the LED display module? LED display module: It is composed of several display pixels, which is structurally independent and can form the smallest unit of LED display. Typical 8*8 dot matrix modules.
3. Unit board: It is the main unit of the display screen, which is composed of luminescent materials and driving circuits. The indoor screen usually consists of a unit board. Module: The smallest display unit for the outdoor display. A plurality of light-emitting diodes are packaged in a fixed mold case by welding, potting, etc. in a certain order, and become a module. Unit box: It is the main unit of the display screen, which consists of unit boards in a certain order. Outdoor screens are usually made up of unit boxes.
3. What is DIP? DIP is the abbreviation of DOUBLE IN-LINE PACKAGE, double in-line assembly, mainly used for indoor full color screen
4. What is SMT? What is SMD? SMT is the surface assembly technology (short for SURFACE MOUNTED technology), which is currently the most popular technology and process in the electronics assembly industry; SMD is a surface-mounted device (short for surface mounted device) for indoor full-color display. A single point of maintenance can be achieved to effectively overcome the mosaic phenomenon.
5. What is the plug-in module, what are the advantages and disadvantages? It means that the lamp of DIP package passes the lamp foot through the PCB board, and the tin is filled in the lamp hole by soldering. The module made by this process is the plug-in lamp group. The advantages are: high brightness, good heat dissipation, and the disadvantage is The pixel density is small.
6. What is a surface mount module? What are the advantages and disadvantages? The surface mount is also called SMT. The SMT packaged lamp is soldered to the surface of the PCB board through the soldering process. The lamp pins do not need to pass through the PCB board. The module made by this process is called the surface mount module. The advantage is that the display effect is good. The pixel density is large, suitable for indoor viewing: the disadvantage is that the brightness is not high enough, and the heat dissipation of the lamp itself is not good enough.
7. What is the sub-surface module? What are the advantages and disadvantages? Sub-surface label is a product between DIP and SMT. Its LED lamp has the same package surface as SMT, but its positive and negative pins are the same as DIP, and it is also soldered through PCB. The advantages are: high brightness, good display effect, disadvantages: complicated process and difficult maintenance
8. What is three-in-one? What are its advantages and disadvantages? It means that the SMT lamps of RGB three different color LED chip packages are vertically juxtaposed according to a certain interval; the advantages of three-in-one: good effect; disadvantages: complicated process, difficult maintenance; high cost.
9. What is three-in-one? The RGB three independently packaged SMT lamps are vertically juxtaposed at a certain interval;
10. What is the difference between the indoor module full color screen and the patch full color screen? (1) Luminous part: The display module of the module full color screen is generally yellow-green, the module of pure green is more expensive; the full-color screen of the patch generally uses pure green die (2) display effect: the module full color screen pixel point visual feeling Thick, low brightness, easy to have mosaic phenomenon; patch full color screen consistency is good, high brightness (3) maintenance: module full color is not easy to maintain, the whole module replacement cost is higher; patch full color easy to maintain, Perform single lamp repair and replacement
11, outdoor screen can not use the surface of the LED, why? No. The outdoor screen installation structure is strict, the patch LED can not adapt to the harsh outdoor environment; the outdoor screen brightness requirements are higher, and currently the patch LED can not meet the brightness requirements of the outdoor screen.
12. Why is the production cycle of outdoor screens longer? (1) Raw material procurement: LED lamp purchase cycle is long, especially imported die, ordering cycle takes 4-6 weeks. (2) Complicated production process: PCB design, shell production, glue filling, whitening balance, etc. 3) Strict structural requirements: generally box design, need to consider wind, rain, lightning, etc.
13. What is a synchronous system and what is an asynchronous system?
Synchronous and asynchronous are relative to the computer. The so-called synchronization system refers to the LED display control system that displays the content displayed on the display and the computer display. The asynchronous system means that the computer-edited display data is stored in advance. In the display control system, the normal display of the LED display will not be affected after the computer is turned off. Such a control system is an asynchronous control system.
14. What is a real pixel? What is a virtual pixel? What are the virtual pixels? What is pixel sharing?
The real pixel refers to the relationship between the physical pixel number on the display screen and the actual displayed pixel point is 1:1. How many points actually appear on the display screen can only display the image information of how many points. The virtual pixel refers to the relationship between the physical pixel number of the display screen and the actual displayed pixel number: 1:N (N=2, 4), which can display the image pixel 2 times or 4 times more than the actual pixel of the display screen; Pixels can be divided into virtual virtual and hardware virtual according to the virtual way: divided into 2 times virtual and 4 times virtual according to the multiple relationship, according to the lighting mode on one module: 1R1G1B virtual and 2R1G1B virtual. The real pixel screen corresponds to the virtual screen. In short, the real pixel screen refers to each of the three kinds of red, green and blue light-emitting tubes that constitute the display screen, and finally only participate in the imaging use of one pixel to obtain enough. Brightness. The virtual screen uses a software algorithm to control the LED of each color to finally participate in the imaging of multiple adjacent pixels, so that a larger resolution can be achieved with fewer lamps, and the display resolution can be increased by about four times. . As we all know, the biggest cost in the display is the lamp. How to save the cost of the lamp for the user without losing the brightness is one of the goals pursued by the display technology. And virtual technology is a development direction. The virtual technology is by no means a simple participation in the imaging of the lamp, and the influence on brightness and gradation is also very large. This requires the cooperation between the control system and the driver chip, and uses the software algorithm combined with the response time of the driver chip to achieve the purpose of saving the cost of the lamp under the premise of substantially non-destructive brightness.
15. What is remote control? Under what circumstances? The so-called remote is not necessarily a long distance. The remote control includes the main control terminal and the controlled terminal in a local area network, and the space distance is not far; and the main control terminal and the controlled terminal are within a relatively distant spatial distance, and the customer requests or directly exceeds the optical fiber according to the customer control position. Control the distance, then use remote control. Display to computer distance transmission: fiber or network cable, it is generally recommended to use fiber, because the transmission signal is good, it is not easy to be distorted. Multimode can be more than 500m, single mode is 10km, and Category 5 twisted pair is below 100. When the wiring distance between the display screen and the control computer is less than 100 meters, it is transmitted by the network cable; when the distance between the two is less than 500 meters and more than 100 meters, the multimode fiber is used, and when the distance is more than 500 meters, the single mode fiber is used. Control system technical requirements: There are no remote control and LAN control requirements, usually we are connected with the computer to control the TV, DVD and other signals, the computer basically requires AGP slot and PCI slot.
16. The static screen corresponds to the scanning screen. The static screen refers to the LED display screen displaying the text, image and video. The light points on the LED display are illuminated at the same time; instead of scanning The screen uses the visual persistence feature of the human eye to illuminate each line of the LED display in a short period of time. As we all know, the LED display is driven by the duty cycle (duty ratio: the ratio of the number of rows lit at the same time to the number of rows in the entire area in a certain display area. The indoor screen is usually 1/16 scan or 1/ 8 scanning, outdoor screen is generally static.), therefore, the brightness of the display has a great relationship with the time period of lighting. In the case of the same brightness of the same tube, the static screen is higher than the brightness of the scanning screen, so Static screens are often used in situations where high brightness is required outdoors, while scanning screens are often used indoors where brightness is not critical to save drive costs. Nowadays, there are also scanning methods to make LED displays outdoors to save costs. Of course, the use of the scanning screen outdoors is quite high for the control and drive parts, and the performance requirements for the driver chip are also extraordinary.
17. What is the perspective? What is the angle of view? What is the best perspective? The viewing angle is when the brightness of the viewing direction drops to 1/2 of the brightness of the normal of the LED display. The angle between the two observation directions of the same plane and the normal direction. Divided into horizontal and vertical viewing angles; the viewing angle is the angle between the direction of the image content on the display and the normal to the display screen. The best viewing angle is that you can just see the content on the display, and it is not flat, the angle between the clearest direction of the image and the normal.
18. What is the best line of sight? It is the vertical distance between the position of the screen and the position of the screen that is the most clear position of the screen. For two spots with a certain shape, brightness, and distance, the minimum vertical distance from the position of the two points to the two points cannot be distinguished, which is called the minimum line of sight, and the angle between the point and the line connecting the two spots It is called the minimum angle of view. Therefore, the factors affecting the minimum line of sight and the minimum angle of view are: the shape, brightness, and distance of the spot. For a rectangular display screen with a certain brightness and distance, the minimum vertical distance from the position point of the rectangular display screen content to the rectangular picture cannot be distinguished, which is called the maximum line of sight. Therefore, the factors that affect the maximum line of sight are: rectangular display screen brightness, distance. A range greater than the minimum line of sight and less than the maximum line of sight is called the effective line of sight.
How to choose the right display:
(1) Need for display content (2) Visibility of viewing distance and viewing angle (3) Requirements for screen resolution (4) Requirements for installation environment (5) Control of cost.
There are three important factors when designing the screen size:
(1) Needs to display content (2) Venue space condition (3) Display unit template size (indoor screen) or pixel size (outdoor screen).

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