Meaning of common technical parameters of industrial LCD
Date:2019-07-26
All LCD datesheets are marked with a lot of parameters. Usually when we choose industrial LCD, we also choose from the main technical parameters. So those are the main technical parameters of industrial LCD. What is the meaning of each parameter?
The main parameters of industrial LCD screen are: contrast, brightness, resolution, point spacing, response time, viewing angle, refresh rate, brightness, contrast, signal input interface, etc
contrast ratio
The control IC, filter, orientation film and other accessories used in LCD manufacturing are related to the contrast of the panel. For ordinary users, the contrast of 350:1 is enough, but in the professional field, such contrast can not meet the needs of users. Compared with CRT display, which can easily achieve 500:1 or even higher contrast, only high-end LCD can achieve such a degree. In the market, Samsung, ASUS, LG and other first-line brands now have LCD monitors with 1000:1 contrast. However, because the contrast is difficult to be accurately measured by the instrument, you have to go to see it yourself.
Tip: contrast is very important. It can be said that it is a more important indicator for selecting LCD than bright spot. When you understand that the LCD purchased by your customers is used for entertainment, you can emphasize that contrast is more important than no bad spot. When we watch streaming media, generally the brightness of the source is not big, but we need to see the light and dark contrast of the character scene and the texture change from gray to black, It depends on the contrast level to show, the 256 level gray test in the test software can see more small gray grid clearly when looking up, that is, the contrast is good!
brightness
LCD is a kind of material between solid and liquid. It can't emit light, so it needs additional light source. Therefore, the number of lamps is related to the brightness of LCD. The earliest liquid crystal display had only two lamps, the most popular one had four lamps, and the high-end one had six lamps. The design of the four lamps can be divided into three types: one is that there is a lamp on each side, but the disadvantage is that there will be dark shadows in the middle. The solution is to arrange the four lamps horizontally from top to bottom. The last type is the "U" type, which is actually two lamps in disguised form. The design of six lamps actually uses three lamps. The manufacturer bends the three lamps into "U" shape and then places them in parallel to achieve the effect of six lamps.
Tip: brightness is also an important indicator. The brighter the LCD is, the better it stands out from a row of LCD walls. The highlight technology we often see in CRT (youpai is called highlight, Philips is called highlight, and Mingji is called ruicai) is to increase the current of the shade tube and bombard the phosphor to produce a brighter effect. Such technology usually sacrifices the image quality, In exchange for the life of the monitor, all products using this kind of technology are generally bright by default. You always have to press a button to implement it. Click 3x to play games; Press one more button to turn it into 5x to light up the video disc. If you look at it carefully, it will become blurred. If you want to see the text, you have to go back to the normal text mode. This design actually allows you not to highlight it frequently. The principle of LCD display brightness is different from CRT. They are realized by the brightness of backlight behind the panel. Therefore, the lamp should be designed more, the light will be uniform. In the early days of selling liquid crystal, it was a great thing to tell others that liquid crystal was three. But at that time, Chimei CRV developed a six lamp technology. In fact, it turned the three tubes into a "U" shape and became the so-called six tubes; Such a six lamp design, coupled with the lamp light itself is very strong, you can see the panel is very bright, such a representative work in youpai is represented by va712; But all bright panels will have a fatal injury, the screen will leak light, this term is rarely mentioned by ordinary people, the editor thinks it is very important, light leakage means that in the full black screen, the LCD is not black, but white and gray. Therefore, a good LCD should not blindly emphasize brightness, but more emphasis on contrast, the VP and VG series of upai do not stress brightness.
resolving power
LCD display is realized by LCD pixels, but because the number and position of LCD pixels are fixed, the LCD can achieve the best display effect only at the standard resolution, while at the non-standard resolution, the LCD internal IC is calculated by interpolation algorithm, so the picture will become blurred, However, the true resolution of the LCD display depends on the size of the LCD panel, and the true resolution of 15 inches is 1024 × 768, 17 inches is 1280 × 1024。
Dot distance of LCD
The meaning of pixel pitch of LCD is similar to dot pitch of CRT. However, the former is not as important to product performance as the latter. The dot pitch of CRT will change with the design of mask or grating, the type of video card and the vertical or horizontal scanning frequency. The number of pixels on the LCD display is fixed. Therefore, as long as the size and resolution are the same, the pixel spacing of all products should be the same. For example, the resolution is 1024 × 768 15 inch LCD display, the pixel spacing is 0.297mm (some products are also marked as 0.30mm).
response time
Response time is an important indicator of LCD display. It refers to the speed of each pixel responding to the input signal, that is, the speed of pixels turning from dark to light or from light to dark. Its unit is Ms. the smaller the response time is, the better. If the response time is too long, serious "tailing" phenomenon will occur when displaying dynamic images (especially when watching DVD and playing games). At present, the response speed of most LCD displays is about 25ms, such as BenQ, Samsung and other high-end products, the response speed is up to 16ms, and even now there is a 12ms LCD.
viewing angle
Viewing angle is also a very important parameter of LCD display. Because the LCD display must be in a certain viewing angle range to obtain the best visual effect, if viewed from other angles, the brightness of the picture will become dark (brightness decline), the color will change, and even some products will change from positive image to negative image. The angle between up and down (vertical viewing angle) or left and right (horizontal viewing angle) is the "viewing angle" of LCD. Because the light source of LCD display has certain directionality after refraction and reflection, it will produce color distortion when viewing beyond this range.
Refresh rate of LCD display
Due to the difference in design, LCD display will not flash like CRT display because of the high or low refresh rate. For CRT displays, the refresh rate is related to the speed of picture updating. The faster the speed is, the less likely the picture is to flicker. The refresh rate is generally above 75Hz, so that users will not feel the picture flickering. (if you have seen the display picture taken by the camera, there will be black shadows flashing one by one. If the refresh rate is higher, the number of black shadows flickering will be lower, The better for the user's eyes).
Brightness, contrast
Brightness is measured in candlelight per square meter (CD / m2), which is usually indicated in LCD specifications, and the indication of brightness is the maximum brightness that the backlight can produce. General LCD displays have the ability to display 200 CD / m2 brightness, even higher than 300 CD / m2. The higher the brightness, the wider the application environment. At present, there are two ways to improve the brightness. One is to improve the light passing rate of LCD panel; The other is to increase the brightness of the background light, that is, to increase the number of lamps. It should be noted that a brighter product is not necessarily a better one, and whether the brightness is uniform is the key, which can not be found in the product specifications. Whether the brightness is even or not is closely related to the number and configuration of light sources and reflectors. The brightness must be dark far away from the light source.
Signal input interface
LCD displays generally use two signal input modes: traditional analog VGA 15 pin D-sub and DVI input. In order to adapt to the mainstream display card with analog interface, most LCD displays provide analog interface, and then convert the analog signal from the display card into digital signal in the display. In the process of digital to analog conversion, there will be some information loss, so the displayed screen font may be blurred, jitter, color deviation and other phenomena; Now there are many video cards with DVI and VGA interfaces, and the price is not high, so it is recommended to use DVI interface.
The technical parameters of industrial LCD are not only the above, but also the working temperature, storage temperature, structure size and so on.
