|LED display video panels commonly used concepts and words|
It is the smallest unit that can be independently controlled on the screen. PIXEL is the abbreviation of picture element. On the three primary color screen, the pixel consists of three parts: red, green, and basket. Each part is composed of one or several LEDs. In theory, respectively Adjust the brightness of red, green and blue to show any color.
The center distance of adjacent pixels. The smaller the spacing, the shorter the viewing distance.
Usually used in digital display devices, indicating the total number of pixels, generally written in the form of a wide X height, such as 800X600.
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 angle is increased. The sum of the angles obtained by moving up and down in the opposite direction is called the horizontal viewing angle, and the vertical viewing angle is measured in the same way. The LED viewing angle manufacturer will give the parameters.
Brightness is the most important parameter in any display device. The main unit of brightness is called candle (candela), which is represented by CD. The brightness of a single LED is usually added by millicalenda, MCD, or one thousandth of a CD, and the brightness of a square meter is added together to obtain the brightness per unit area. (NITS) indicates that 1 NITS=1 CD/m2
For various display devices, the optimal viewing distance should be the minimum distance that the human eye cannot distinguish the pixel, which is about 3400 times the dot pitch. The viewing distance of televisions and computers is usually less than this requirement, but the acceptable distance cannot be less than 1700 times the point spacing.
Screen update rate / refresh rate (Refresh Rate)
The rate at which screens are updated, usually expressed in Hertz (Hz), is different from the frame rate.
The number of image frames displayed per second on the screen, usually depending on the input signal (25 fps for PAL, 30 fps for NTSC)
Field frequency (Field)
Half of the frames of PAL and NTSC, because PAL and NTSC are interlaced, only half of the image is displayed for each refresh.
Pure green and true green
In the past 30 years, various color LEDs have been developed. First, red, yellow, yellow-green, blue LEDs and pure green LEDs were invented by Japanese engineers in the 1990s. At this point, it is possible to manufacture LED full-color screens. The LED screen of the video must be pure green. If you use yellow-green to do it, the color is definitely not true. If the number of green tubes in a pixel is much larger than the number of red tubes and blue tubes, it must be a yellow-green tube, because yellow Green is not bright enough, you must use more than one, but the yellow-green LED is cheap. This kind of screen is commonly called pseudo color screen.
The brightness of the red, green and blue colors must be balanced to accurately restore the true color. In other words, the white color of the LED must be white instead of pink. If the red, green and blue are at the highest brightness, the mixed colors are usually not white. In order to get white (usually called 6500K color temperature), one or two of the red, green and blue colors must be turned down. In order to obtain the correct white, it is necessary. Repeated measurement to adjust the brightness, this process is called white balance.
The number of colors that LED screens can express depends on the gray level of RGB three colors, which is 256 levels of gray in the standard full color screen. For the stadium full color system of the stadium, 256 gray levels are not enough to recover accurately. Restore color. Also known as color depth, refers to the number of different brightness, red, green and blue have their own grayscale, in general color system is generally 256 grayscale, can produce 256X256X256 = 16,777,216 colors, called 24-bit color in PC, It is called an 8-bit system in the LED display system.
GAMMA correction (gamma correction)
This is a kind of transformation function to reduce the amount of gray, which produces a color and contrast that is closer to the real environment. The actual color of the full color screen is limited. When the night, the brightness of the screen must be reduced. The color 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 needed. The 1Bill color system (1024 colors of red, green and blue) can express more realistic colors. Because it expands from 256 levels of gray to 1024 levels, it greatly enriches the number of colors that can be expressed.
Virtual Resolution Technology (Virtual Resolution)
Also known as a shared pixel or a dynamic pixel, a pixel that is four times as large as a physical pixel is quickly sent to a physical pixel for four times in a parity column and a parity row. The effect is equivalent to reducing the pitch by half, and the cost is basically the same as the conventional method. Compared, basically no increase, but can achieve the original 4 times resolution.
The quality of the entire picture is largely determined by the consistency of the LEDs. The issue of consistency is an inherent problem with 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 is, the smaller the range is. The LEDs provided by high-quality manufacturers can reduce the workload of debugging. The human eye is quite sensitive to color and brightness. It is easy to detect the difference between LEDs. Especially in high-brightness display systems, this difference is even greater. Designers must use various techniques to eliminate this difference. , increase consistency.
LED screens are composed of red, green and blue colors to produce various colors, but these three colors are made of different materials, the viewing angles are different, and the spectral distributions of different LEDs are varied. These differences can be observed. Color difference. When the LED is viewed at a certain angle, its color changes, and the ability of the human eye to judge the color of the real picture (such as a movie picture) is better than that of the observation computer.