Basic knowledge of LED display

Basic knowledge of LED display

 

 

 

 

1. Pixel

Refers to the luminous point composed of each single or multiple light-emitting tubes. It is the smallest unit that can be independently controlled on the screenPIXEL is the abbreviation of pictureelement, on the three-color display, the pixel is composed of three parts: red, green, basket, each part is composed of one or several LEDs, theoretically, adjust the brightness of red, green, and blue respectively, and can show any color.

 

2. Pitch

The distance between the centers of adjacent pixels. The smaller the spacing, the shorter the viewing distance.

 

3. Resolution

Usually used in digital display devices, it represents the total number of pixels, and is generally written in the form of width x height, such as 800 x 600.

 

4. Viewing Angle

When the observer faces the LED, the maximum brightness of the LED can be seen, when the observer moves to the left or right, the brightness seen will decrease, when the brightness is reduced to half of the maximum brightness, the sum of the angle at this time plus the angle obtained by moving in the opposite direction is called the horizontal viewing angle, and the vertical viewing angle is measured in the same way. The angle of view of the LED manufacturer will give the parameters.

 

5. Brightness

Brightness is the most important parameter in any display device. The main unit of brightness is called candlelight (candela), which is represented by CD, and the brightness of a single LED is usually millicandelas, MCD, that is, one thousandth of a CD, adding the brightness of an LED per square meter together to obtain the brightness per unit area, expressed in nits (NITS), 1NITS=1CD/m2.

 

6. White balance

The brightness of red, green and blue must be balanced to accurately reproduce the true color, in other words, the white of the LED must be white, not pink. If red, green, and blue are both at the highest brightness, the mixed colors are usually not white, in order to get white (commonly known as 6500K color temperature), one or two of the red, green, and blue must be turned down, and in order to get the correct white, the brightness must be measured and adjusted repeatedly, a process called white balance.

 

7. Viewing Distance

For various display devices, the optimal viewing distance should be the minimum distance at which the human eye cannot distinguish pixels, which is about 3400 times the distance between dots. The observation distance of TV and computer is usually less than this requirement, but the acceptable distance cannot be less than 1700 times the distance between the dots.

 

8. Grey Levels

Also known as color depth, refers to the number of different brightness, red, green and blue have their own grayscale, in the full color system is generally 256 levels of grayscale, can produce 256X256X256 = 16,777,216 colors, in the PC is called 24-bit color, in the LED display system is called 8-bit system.

 

The number of colors that the LED display can perform depends on the gray level of the RGB three colors, which is 256 levels of gray in the standard full-color display, and 256 gray is not enough for the LED full-color system of the stadium, and it is not possible to accurately restore the restored color.

 

9. Refresh Rate

The rate at which the display is updated, usually expressed in hertz (Hz). It is not the same as the frame rate.

 

10. Frame Rate

The number of image frames displayed per second by the display usually depends on the input signal.

 

11. Field Frequency

Half frames of PAL and NTSC, because PAL and NTSC are interlaced, and only half a frame of image is displayed per refresh.

 

12. Advanced concepts

Pure green (Puregreen) and true green (truegreen) various colors of LEDs have been developed one after another, first red, yellow, yellow-green, blue LED and pure green LED have been invented in the 90s. At this point, it became possible to manufacture LED full-color displays.

 

13. GAMMA correction

This is a kind of transformation function to reduce the number of grayscale, so as to produce a color and contrast closer to the real environment, the actual color of the full-color screen is subject to many limitations, when the night, the brightness of the screen must be reduced, at this time the color that can be displayed will be reduced, therefore, the color of the digital RGB display is definitely less than 16M color, in order to solve this problem, a higher level of gray scale is required, and the system of 1Bill color (1024 levels of color each of red, green and blue) can express more realistic colors, Because the gray scale is expanded from 256 to 1024 levels, the number of colors that can be expressed is greatly enriched.

 

14. Virtual Resolution

Also known as shared pixels or dynamic pixels, the pixels that are 4 times the physical pixels are quickly sent to the physical pixels for display in 4 times according to the odd-even column and the odd-even row, and the effect is equivalent to reducing the spacing by half, and its cost is basically not increased compared with the traditional practice, but the original resolution can be achieved by 4 times.

 

15. Uniformity

The quality of the entire picture is largely dependent on the consistency of the LEDs. The problem of consistency is inherent in LEDs when LEDs are produced. Their brightness, viewing angle, and other characteristics are actually not uniform, these parameters are distributed in a certain range, the better the manufacturer's process control, the smaller the range, the selection of high-quality manufacturers to provide LEDs can reduce the workload of debugging, the sensitivity of the human eye to color and brightness is quite high, the difference between LEDs is easy to detect, especially in the bright display system, the difference is greater, the designer must use various technologies to eliminate this difference, increase consistency.

 

16. Colour Shift

LED display is composed of red, green and blue colors to produce a variety of colors, but these three colors are made of different materials, the viewing angle is different, the spectral distribution of different LEDs is changing, and these differences that can be observed are called color aberration. When an LED is viewed from a certain angle, its color changes, and the human eye is better able to judge the color of a real picture (such as a movie picture) than to observe the image generated by a computer.

 

17. Cellboard size

Refers to the dimensions of the cell board, usually expressed as the length of the cell board multiplied by the width, in millimeters.

 

18. Cellboard pixels

Refers to how many pixels a cell board has, usually expressed as the number of rows of cell board pixels multiplied by the number of columns. (e.g. 64×32)

 

19. Lattice density

Also known as dot matrix density, it usually refers to the number of pixels per square meter of display.

 

20. Maximum power consumption per square meter (Consumptionpersqm)

The maximum power consumption per square meter per hour usually refers to the power consumption when the display is fully white. Because we have adopted a capacity increase design in the design of the power supply, the maximum power of the power supply will not be reached in the case of full load of the display, which plays a good role in protecting the display screen.

 

21. Weight (Kg)

It usually refers to the weight of the screen per square meter (including power supply, frame, etc.), but does not include the weight of the frame.

 

22. Communication distance

The distance between the operating platform (computer) and the screen. Usually, the transmission of 8-core network cable is not more than 130 meters, and the transmission of optical fiber is 500 meters to 1300 meters.

 

23. Support mode

The full English name of VGA is VideoGraphicArray, which is the display drawing array, which is commonly known as the graphics card interface. VGA supports simultaneous display of 16 colors or 256 shades of gray at a higher resolution of 640X480 and 256 colors at 320X240 resolution.

 

The sensitivity of the naked eye to color is much greater than resolution, so images remain vivid even at lower resolutions. VGA quickly became popular due to good performance, and manufacturers have expanded it on the basis of VGA, such as increasing the video memory to 1M and making it support higher resolution such as 800X600 or 1024X768, these expanded modes are called VESA (VideoElectronicsStandardsAssociation) SuperVGA mode, referred to as SVGA, Today's graphics cards and monitors support SVGA mode. Both VGA and SVGA use a 15-pin trapezoidal plug to transmit analog signals.