What information does LED display have
Author:Zuo Ning Time:2021-06-10 17:22 Browse(481)
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edit the entryLED panel: LED is the abbreviation of light emitting diode, short for LED.

What information does LED display have

it is a display mode by controlling semiconductor light emitting diode.
its general appearance is composed of many small red lights, and the characters are displayed by the light on and off.
it is used to display text, graphics, images, animation, market, video, etc The display screen of video signal and other information.
the display screen of video signal and other informationThe LED display screen is divided into graphic display screen and video display screen.
both are composed of LED matrix blocks.
the graphic display screen can display Chinese characters, English texts and graphics synchronously with the computer; The video display screen is controlled by microcomputer.
it can display all kinds of information in a real-time, synchronous and clear way of information transmission, as well as two-dimensional and three-dimensional animation, video, TV, VCD programs and live scenes.
the LED display screen shows bright colors.
it has a strong sense of three-dimensional, static as oil painting, dynamic as film, and is widely used in finance, taxation, industry and commerce Posts and telecommunications, sports, advertising, factories and mining enterprises, transportation, education system, stations, docks, airports, shopping malls, hospitals, hotels, banks, securities markets, construction markets, auction houses, industrial enterprise management and other public placesLED display screen can display the changing numbers, text, graphics and images; It can be used not only in the indoor environment, but also in the outdoor environment.
it can be used in the outdoor environmentIt has the incomparable advantages of projector, TV wall and LCDLED has been widely valued and developed rapidly.
these advantages can be summarized as follows: high brightness, low operating voltage, low power consumption, miniaturization, long service life, shock resistance and stable performance.
LED has a broad development prospect.
at present, it is moving towards higher brightness, higher weather resistance, higher luminous density, higher light-emitting density, higher light-emitting density, higher light-emitting density, higher light-emitting density and higher energy consumption Higher uniformity of luminescence, reliability and panchromatic directionClassification of LED display1. According to the color base color can be divided intoSingle primary color display screen: single color (red or green).
the color of display screen is red or greenDual primary color display screen: red and green dual primary color.
256 gray levels, 65536 colors can be displayed.
the dual primary color display screen can display 65536 colorsFull color display: red, green and blue.
the full color display with 256 gray levels can display more than 16 million colors. it is suitable for making time clock screen, interest rate screen, etc., and electronic display for displaying numbers.
the LED digital display device is a 7-segment code nixie tubeLED dot matrix graphic display screen: the display device is a dot matrix display module composed of a number of evenly arranged light-emitting diodes.
it is suitable for playing text and image information.
the LED dot matrix graphic display screen is a dot matrix display module composed of a number of evenly arranged light-emitting diodesLED video display screen: the display device is composed of many light-emitting diodes.
it can display video, animation and other video files.
the LED video display screen is composed of many light-emitting diodes3. Classification by usageIndoor display: small light spot.
general φ 3mm-- φ The display area is generally several to ten square metersOutdoor display screen: the area is generally tens of square meters to hundreds of square metersIt has high brightness, can work in the sun, and has the functions of wind, rain and water proofing4. Classification according to the diameter of luminescent pointIndoor screen: φ 3mm、 φ 3.75mm、 φ 5mm、 Outdoor screen: φ 10mm、 φ 12mm、 φ 16mm、 φ 19mm、 φ 20mm、 φ 21mm、 φ 22mm、 φ 26mm The basic unit of outdoor screen light-emitting is light-emitting tube.
the principle of light-emitting tube is that a group of red, green and blue light-emitting diodes are sealed in a plastic tube to emit light together5. The display modes include static, horizontal scrolling, vertical scrolling and page turning.
a single module controls and drives 12 pieces (up to 24 pieces) of 8x8 dot matrix.
a total of 16x48 dot matrix (or 32x48 dot matrix), which is 12 times (or 24 times) of a single MAX7219 (or PS7219, HD7279, ZLG7289, 8279 and other similar LED display driver modules)! The display effect is good.
the power consumption is low, and the cost is lower than that of MAX7219.
the circuit can be used to form any lattice large display screenInspection method of LED display screen.
the results show that the method is simple and reliableA look at the screen specifications, appearance, flatness, wiring, etcSecond, after the screen is turned on, the bad points are out of the range. (generally speaking, the current screen is basically gone.)Color difference consistency, whether the display text is normal, display pictures, etc. for full color, white, red, green and blue should be printed on the full screenReview of technical advantagesComparison of existing common indoor full color schemes:1. Lattice module scheme: the earliest design scheme.
it is developed from indoor pseudo color lattice screenAdvantages: the cost of raw materials is the most advantageous, and the production and processing technology is simple, and the quality is stable.
the cost of raw materials is the highestDisadvantages: poor color consistency.
the mosaic phenomenon is serious, and the display effect is poor.
the mosaic phenomenon is serious2. Single lamp scheme: in order to solve the color problem of dot matrix screen.
a scheme based on outdoor display technology is proposed, and the outdoor pixel reuse technology (also known as pixel sharing technology, virtual pixel Technology) is transplanted to the indoor display.
in this scheme, the color problem of dot matrix screen is solvedAdvantages: the color consistency is better than that of dot matrix moduleDisadvantages: poor color mixing effect.
small viewing angle, color difference in horizontal direction.
processing is more complex.
high antistatic requirements.
it is difficult to achieve the actual pixel resolution of more than 10000 points.
in this paper, the method of color mixing is introduced3. Chip scheme: the scheme using chip LED as display elementAdvantages: color consistency.
visual angle and other important display indicators are the best in the existing scheme, especially the color mixing effect of three in one surface paste is very good.
the color mixing effect of three in one surface paste is very goodDisadvantages: the processing technology is troublesome.
the cost is too high.
sub surface pasting scheme: actually, it is an improvement of single lamp scheme.
it is still in the process of improvement.
the scheme is still in the process of improvementAdvantages: in terms of display color consistency.
there is little difference between the primary indicators such as visual angle and the labeling scheme, but the cost is low, the display effect is very good, and the resolution can be more than 17200 theoretically.
in this paper, we introduce the principle of color consistencyDisadvantages: the processing is still more complex.
the antistatic requirements are high.
the anti-static requirements are highAnalysis of key technical indexes of LED display screenPixel out of control rateThe pixel out of control rate refers to the proportion of the smallest imaging unit (pixel) of the display screen not working normally (out of control).
there are two modes of pixel out of control: one is blind spot.
that is blind spot, which is called blind spot when it is not on when it needs to be on; Second, it is often a bright spot,Generally speaking,
pixels are composed of 2R1G1B (two red lights, one green light and one blue light, the same below), 1R1G1B, 2R1G, 3r6g and so on. Generally, the red, green and blue lights in the same pixel will not be out of control at the same time, but as long as one of the lights is out of control, We think that this pixel is out of control.
for the sake of simplicity.
we count and calculate the out of control pixels according to the primary colors of the LED display screen (i.e. red, green and blue), and take the maximum value as the out of control rate of the display screen.
we calculate the out of control pixel according to the primary colors of the LED display screen (i.e. red, green and blue)The ratio of out of control pixels to the total number of full screen pixels.
we call it "out of control rate of whole screen pixels."
in addition.
in order to avoid out of control pixels concentrating in a certain area, we propose "out of control rate of area pixels", that is, at 100% × In the 100 pixel area, the ratio of the number of out of control pixels to the total number of pixels in the area (i.e. 10000).
this index quantifies the requirement of "out of control pixels are discrete distribution" in SJ / t11141-2003 general specification for LED display screen.
it is convenient and intuitiveAt present, LED displays in China are aging (toaster) before leaving the factory.
LED lights with out of control pixels will be repaired and replaced. It is no problem that "out of control rate of whole screen pixels" is controlled within 1 / 104 and "out of control rate of regional pixels" is controlled within 3 / 104. Some enterprises even require that out of control pixels are not allowed before leaving the factory, However, it is bound to increase the manufacturing and maintenance costs of manufacturers and prolong the delivery time.
in different applications, the actual requirements of pixel out of control rate can be quite different,It is acceptable and attainable to control the index within 1 / 104; If it is used for simple character information release, it is reasonable to control the index within 12 / 104Gray scaleGray scale is the so-called color scale or gray scale, which refers to the brightness level.
for digital display technology,
gray scale is the decisive factor of the number of display colors.
generally speaking, the higher the gray scale is.
the richer the colors are, the more delicate the picture is, and the easier it is to show the rich details.
in this paper, the gray scale of digital display technology is introducedThe gray level mainly depends on the A / D conversion bits of the system.
of course, the video processing chip, memory and transmission system of the system all need to provide the support of corresponding bits.
at present, the domestic LED display mainly adopts the 8-bit processing system.
that is 256 (28) gray level.
simply understand that there are 256 brightness changes from black to white.
using RGB three primary colors can form 256 × two hundred and fifty-six × 256=16777216 colors.
that is commonly known as 16 megacolors.
international brand displays mainly use 10 bit processing system.
that is, 1024 gray level, RGB three primary colors can form 1.07 billion colors.
the display screen of international brand mainly uses 10 bit processing systemAlthough the gray level is the decisive factor to determine the number of colors.
but it does not mean that the larger the unlimited, the better.
because first of all, the resolution of human eyes is limited.
moreover, the improvement of system processing bits will involve the changes of system video processing, storage, transmission, scanning and other aspects, resulting in a sharp increase in cost, Generally speaking, the 8-bit system can be used for civil or commercial products.
the 10 bit system can be used for broadcast products.
the price performance ratio will be reducedBrightness identification levelThe brightness discrimination level refers to the brightness level of the image that the human eye can distinguish from the darkest to the whitestAs mentioned earlier, the gray level of the display screen is very high.
it can reach 256 levels or even 1024 levels.
however, due to the limited sensitivity of human eyes to brightness,
these gray levels can not be fully recognized.
that is to say, many adjacent gray levels of human eyes look the same.
and the eye resolution is different from each other.
for the display screen.
the level of human eye recognition Naturally, the more the better, because the displayed image is for people to see.
the more brightness levels that the human eye can distinguish.
means that the larger the color space of the display screen, the greater the potential of displaying rich colors.
the brightness identification level can be tested by special software.
generally, the display screen can reach level 20 or above, even if it is a better level.
the brightness identification level of the display screen can reach level 20 or aboveGray nonlinear transformationGray nonlinear transformation refers to the transformation of gray data according to the empirical data or some arithmetic nonlinear relationship, and then provide it to the display screen.
because LED is a linear device.
it is different from the nonlinear display characteristics of traditional display.
in order to make the LED display effect conform to the traditional data source without losing the gray level.
generally, the gray level will be changed after the LED display system Nonlinear transformation of degree data, The number of transformed data bits will increase (to ensure no loss of gray data).
now, the so-called 4096 level gray or 16384 level gray or higher of some domestic control system suppliers refer to the size of gray space after nonlinear transformation.
4096 level adopts the nonlinear transformation technology from 8-bit source to 12 bit space.
16384 level adopts the nonlinear transformation technology from 8-bit to 16 bit space.
from 8-bit source to 12 bit space The space of the bit source is larger than that of the 8-bit sourceGenerally, it is at least 10 bits.
just like the gray level.
the larger the parameter, the better. Generally, 12 bits can do enough transformation.
this parameter is not as big as possibleExplanation of common terms of LED display screen1. LED brightnessThe brightness of LED is generally expressed by luminous intensity.
the unit is candela CD; 1000ucd (micro candela)=1 MCD (millicandela), 1000mcd=1 CD.
the light intensity of indoor single LED is generally 500ucd-50 MCD.
while the light intensity of outdoor single LED is generally 100 mcd-1000 MCD, or even more than 1000 MCD.
the light intensity of indoor single LED is generally 500ucd-50 MCD2. LED pixel moduleLED array into matrix or pen segment.
prefabricated into standard size module.
indoor display commonly used 8 * 8 pixel module, 8 character 7 segment digital module.
outdoor display pixel module has 4 * 4, 8 * 8, 8 * 16 pixel specifications.
outdoor display pixel module because each pixel is composed of more than two LED tube bundles.
solid is also known as tube bundle module.
outdoor display pixel module3. Pixel and pixel diameterEach LED light-emitting unit (point) in the LED display screen which can be controlled independently is called pixel (or pixel).
pixel diameter ∮ refers to the diameter of each pixel.
the unit is mm.
the pixel diameter ∮ refers to the diameter of each pixelFor the indoor display screen,
generally, a single LED is round in shape.
the common pixel diameter calibration methods for indoor display screen are ∮ 3.0, ∮ 3.75, ∮ 5.0, ∮ 8.0, etc.
among them, ∮ 3.75 and ∮ 5.0 are the most.
for the indoor display screen, the pixel diameter calibration methods are as followsIn the outdoor environment.
in order to improve the brightness and increase the line of sight, a pixel contains more than two cluster LEDs; Because more than two cluster LEDs are not circular in general, the pixel diameter of solid outdoor display screen is generally expressed by the average distance between two pixels:? 10,? 11.5,? 16,? 22,? 25.
the pixel diameter of solid outdoor display screen is generally expressed by the average distance between two pixels4. Point spacing, pixel density and information capacityThe center distance or dot pitch between two pixels of LED display screen; The number of pixels per unit area is called pixel density; The amount of display content per unit area is called information capacity.
the essence of the three is to describe the same concept: the distance between two pixels reflects the pixel density.
the distance between two pixels and the pixel density are the physical properties of the display screen; Information capacity is the quantitative unit of information carrying capacity of pixel densityThe smaller the distance between points.
the higher the pixel density, the more the information capacity, and the closer the distance suitable for viewing.
the smaller the distance between pointsThe larger the distance between points.
the lower the pixel density is, the less the information capacity is, and the farther the distance suitable for viewing is.
the larger the distance between points is5. ResolutionThe number of rows and columns of pixels in LED display screen is called the resolution of LED display screen.
resolution is the total number of pixels in the display screen.
it determines the information capacity of a display screen6. LED panelThe LED pixel modules are assembled and arranged into a matrix according to the actual needs.
a LED display screen is composed of a special display driver circuit, DC regulated power supply, software, frame and external decoration7. GrayscaleGrayscale refers to the degree of change in the brightness of a pixel.
the grayscale of a primary color generally has 8 to 1024 levels.
for example.
if the grayscale of each primary color is 256 levels,For dual primary color screen, the display color is 256 × 256=64K colors, which is also called 256 color display screen.
This screen has a color of 64K8. BicolorNowadays, most color LED displays are dual primary color screens.
that is, each pixel has two LED chips: one is red LED chip, and the other is green LED chip.
when the red LED chip is on, the pixel is red.
when the green LED chip is on, the pixel is green, and when the red and green LED chips are on at the same time, the pixel is yellow.
green is the primary color9. Full colorRed and green dual primary colors plus blue primary colors constitute full color.
at present, there are relatively few full-color screens.
due to the high cost of blue tube and pure green tube core
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