How to distinguish the bad spots and bright spots of LCD display, and how to distinguish them?
Author:Qiao Yin Hu Time:2021-08-06 15:45 Browse(543)
The causes of bad points
The causes of bad points.

How to distinguish the bad spots and bright spots of LCD display, and how to distinguish them?

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as the price of liquid crystal display (LCD) continues to decline.
LCD has become the mainstream choice for many netizens when they configure or upgrade their computers.
when businesses show you LCD,
they often use more beautiful images, while many readers take them home after they buy LCD, It was found that there were many bad spots or dark spots or bright spots on the LCD.
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find a merchant to replace it.
the merchant said that five or even less than 15 bad spots on the LCD screen were normal and refused to replace it.
therefore, before purchasing the LCD, learn more about the bad spots of the LCD.
it is better to know more about the methods to identify the bad spots.
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I The bad points of LCD are everywhere.
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the bad points, bright points and dark points of LCD are also known as the "point defects" of LCD.
if there are too many "point defects" or they are eye-catching in the middle.
in many cases, it really makes users intolerable.
LCD is a special product.
in most cases, a crack on the wall of a new house can be repaired, The car can be repainted if it is scratched, but the "point defect" of LCD can't be repaired by consumers.
if you don't pay attention when you buy LCD.
if one or several bad points are just in the middle of the LCD, Then it's even more frustrating.
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the "point defect" of LCD is not only unique to LCD.
where there is LCD, there are bad points, which has become the highest complaint about LCD in the world.
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for example, color screen mobile phones.
when buying mobile phones,Businesses usually use black or bright colors as the default wallpaper pattern of the fuselage, so that "bad points" can be hidden, which makes it difficult for you to detect.
in actual use, it will be found because of changing the wallpaper or screen background.
no more than 3 bad points on the mobile phone screen belong to class A.
businesses can not replace them, so you need to pay more attention to this aspect when purchasing, In order to prevent it in advance.
similarly.
behind the hot sale of PSP, there is also the problem of LCD screen. At present, the most complaints about the quality problems of PSP are also the bad points of PSP screen, The defect rate of PSP's first batch of shipment has reached one third.
the same problem also occurs in Nintendo NDS host.
some of its products also have common screen defects.
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in a word.
whether it is LCD or LCD TV, all digital devices with LCD screen, such as mobile phone, PDA, handheld game console, DC, DV, etc., may have LCD defect, Before you buy this kind of products, you need to work hard on this problem, and master some necessary knowledge of LCD "point defect" in case of urgent need.
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Second, "point defect" concept and causes.
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what is "point defect"? As we all know,
LCD is mainly composed of filter, polarizing plate, glass and cold cathode fluorescent lamp. The "point defect" is the irreparable pixel on the LCD, except for human damage, Most of them are produced in the production process due to external pressure or slight deformation caused by heat on the internal reflector of the screen in the bright spot area.
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the liquid crystal panel is composed of many display points.
the liquid crystal material on each display point changes the refractive index of light under the control of electric signal.

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for example, the LCD panel with a standard resolution of 1024x768.
a LCD panel has 786432 display points (pixels), with a size of 0.099mm. Behind each LCD point, there are three transistors corresponding to red, green and blue filters, respectively. Behind each LCD pixel, there is a micro driving tube to drive it, In these 2.35 million LCD pixels, any transistor failure will make the pixel become a bad or bright spot.
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so many points are difficult to guarantee that there are no bad spots.
therefore, the production of LCD board has very high requirements on the production process, and the number of bright spots and bad spots is directly related to the manufacturer's equipment level, worker's proficiency and the quality of production The technical ability is related to the process.
at present, at least 20% of the LCD boards produced in each batch have "point defects"
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if all the LCD boards with "point defects" are scrapped, it will cost a lot of money, Therefore, manufacturers generally avoid bad points to divide LCD panels.
LCD panels with no "point defects" or few "point defects" are sold to higher price manufacturers or major related manufacturers at a higher price.
while LCD panels with more bad points are generally sold to small manufacturers at a lower price to produce cheap complete machines,
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according to the data,
the common "point defects" of LCD can be divided into three types: bad point, bright point and dark point.
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● bad point.
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in the case of white screen, it is a pure black point or a pure white point in the case of black screen.
when switching to red, green, black, white, red, red, green, red, red, green, red, red, green, black, red, red, green, red, red, green, red, green, red, green, red, green, red, green, green, black In the blue three color display mode, this point is always in the same position and is always a pure black or white point.
in the blue three color display mode, this point is always in the same positionIn this case, the three sub pixels of R, G and B of the pixel are damaged.
such points are called bad points.
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● bright points.
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in the case of black screen, the R, G and B (red, green, red, red, red, red, red, red, red, red, red, red, red, red, red, red, red, red, red, red, red, red, green, red, red, red, red, red, red The appearance of bright spots can be divided into two situations:
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① in the case of a black screen, only R or g or B color dots are displayed.
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in the case of a black screen, red dots in the case of a black screen.
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② in the case of switching to red, green and blue display mode.
only R or g or B color dots are white, At the same time, in the other two modes, there are other color dots, in which there are two bright spots in the same pixel.
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● dark spots.
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in the case of white screen, the color dots with non simple R, G and B are called dark spots.
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the appearance of dark spots can be divided into two cases:
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① when switching to red, green, red, red, red, red, red, red, red, red, red, red, red, red, red, red, red, red, red, red, red, red, red, red, red, green, red In blue three color display mode.
in the same position, there is only one dark spot in R or g or B display mode.
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② in red, green and blue three color display mode.
in the same position, there is only one dark spot in R or g or B display mode, This situation indicates that there are two dark spots in the pixel.
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measurement standard.
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ISO (international standards organization.
International Organization for Standardization) formulated the standard on LCD panel defects in 2001,It defines four levels of quality.
class 1 is not allowed to have bad points.
is the highest level, the worst level is class 4, and 10N bad points are allowed.
in general,
class 2 is used, which allows three bad points, but if only two bad points are within the range of 5 * 5 pixels, it is also not allowed, In addition,
due to the different standards for the definition level of bad points all over the world, and due to the lack of LCD technology and manufacturing process, the cost is limited. Therefore, in the LCD display industry, many manufacturers default that a display with less than 3-6 bad points is a qualified product, Only some products that only use a + panel will make the promise of zero bright spot or zero bad spot.
in addition,
with the continuous improvement of technology, the no bright spot rate of some brands of LCD panels has been able to reach 90%.
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in addition,
although LCD displays have less than three bright / bad spots within the allowed range, However, more and more consumers are not willing to buy a display with n bright spots / bad spots when buying LCD, so it is difficult for LCD manufacturers with bright spots / bad spots to sell. In order to obtain profits, some manufacturers will not scrap these LCD screens. In most cases, they use a professional equipment to deal with the bright spots / bad spots, so as to make them more acceptable dark spots, We should pay attention to this point when choosing LCD.
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moreover, different countries or regions or brands have different definitions of the number of bad points for products with the same grade A.
this also needs to be understood when purchasing.
for example, Japanese standard takes less than 3 bad points as grade a qualified, Korean standard takes less than 5 bad points as grade a qualified However, in Taiwan standard, 8 bad points or less are regarded as A-level qualificationOf course,
these standards change with the improvement of production process.
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3 Common "point defect" detection methods and software.
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the number of "point defects" is one of the standards to measure the quality of LCD.
it is essential to see how many "point defects" there are before purchasing the LCD.
especially for some manufacturers who promise that there are no bad points in their products, all bright spots are turned into dark spots by instruments.
we should prevent them.
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1 Background check.
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businesses often show you all kinds of gorgeous pictures when displaying LCD.
it not only looks good, but also makes you can't see the missing spots on the LCD.
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when selecting LCD, we should pay attention to the bad points, bright spots, bright spots The most common method is to right-click the mouse on the desktop.
select "properties", select "appearance" in the open window, then select "black" or "white" in the "color" column, and then click "application"
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on the desktop, select "black" or "white" or "red, green, white" in the "color" column If there is any, the LCD has some defects.
it is better to ask for another product without such defects or defects on the four sides of the screen before payment.
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2, With a floppy disk or U-disk or a CD-ROM, and several common display detection software, you can also quickly show the original shape of the fillingThe common software includes Nokia monitor test, displayx, monitors matter checkscreen, etc.
each one has this function.
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● Nokia monitor test.
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among them, Nokia monitor test is a simple and practical display test software.
it can easily help you find out the problems existing in the LCD screen, such as bright spots and dark spots, After starting the software, the first row of options from left to right are geometric distortion test, brightness contrast test, breath phenomenon test and color test, and the second row of options from left to right are convergence test, focus test, resolution test and color test Water ripple test, text display test and Jitter Test, etc.
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among the multiple options of the software,
the "colors" item is useful for detecting the bad points of the display screen. In this option, five colors of white, red, green, blue and black can be output in the full screen state, It is very convenient to check whether there are bad spots on the display.
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● displayx.
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displayx is a 48KB display software.
there is no need to install it. After decompressing, run the main program.
click "general complete test" to complete all the tests.
including interlacing, solid color, color, convergence, geometry, breathing effect, 256 gray, grayscale Right click the mouse or press the ESC key to exit the contrast testIn order to test the bad points, you just need to select the "solid color" mode under the "routine single test" menu and click the mouse to enter different solid colors, such as all black, all red, all green, all white, all blue, etc., so that you can easily find the bad points on the LCD screen
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● passmark monitor test.
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passmark monitor test is a performance test software specially used to test the performance of your computer screen.
it provides 25 different test items.
you can test your computer screen according to different screen resolution settings and adjustments, Of course, it also includes testable LCD flat panel screens. It includes a number of tests, which can well detect the color, response time, text display effect and bad points of LCD, You can try this software.
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● monitors matter checkscreen.
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monitors matter checkscreen is a convenient LCD testing software besides CRT, It includes a number of tests, which can well detect the LCD color, response time, text display effect, whether there are bad points, the degree of video noise and adjustment complexity and other LCD parameters.
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select "LCD display"
to detect the color, response time, text display effect, bad points and other parameters,There are five test items in total. You can start the test by clicking directly, and you can return to the main interface by pressing the right mouse button or ESC.
among them.
color options (color, three primary colors and 16.7 million kinds of color scale images to investigate the color expressiveness, color uniformity, color scale expressiveness, brightness and contrast), crosstalk (sharpness detection, color contrast detection, color contrast detection, color contrast detection, color contrast detection, color contrast detection, color contrast detection, color uniformity, color level expressiveness, brightness and contrast detection) are provided, For PDA devices,
can be detected by pocketlcd.
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● pocketlcd.
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for PDA devices,
can be detected by pocketlcd, Pocket LCD is a tool software used to detect whether there are bad spots on the LCD of Pocket PC. It can let the user judge whether there are bad spots on the LCD by displaying different full screen colors.
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