LCD (liquid crystal display) adopts the latest full-color display technology, and its principle is simple and easy to understand. Basically, the whole concept of liquid crystal display technology is to make use of the physical characteristics of liquid crystal: when it is electrified, it conducts electricity, the arrangement becomes orderly, and light easily passes through; When there is no electricity, the arrangement is chaotic, which hinders the passage of light. Let the liquid crystal block or let the light pass like a gate. Technically, a liquid crystal panel consists of two pieces of quite exquisite sodium-free glass materials, called substrates, with a layer of liquid crystal sandwiched between them. When the light beam passes through this layer of liquid crystal, the liquid crystal itself will stand in rows or distort irregularly, thus blocking or making the light beam pass smoothly. Conventional LCD follows a series of different rules from CRT display. LCD overcomes the shortcomings of CRT, such as huge volume, high power consumption and flicker, but it also brings some problems, such as high cost, poor viewing angle and unsatisfactory color display. CRT display can choose a series of resolutions and can be adjusted according to the screen requirements, but LCD screen only contains a fixed number of liquid crystal cells, and the whole screen can only use one resolution (each cell is one pixel). CRT usually has three electron guns, and the emitted electron flow must be accurately concentrated, otherwise a clear image display cannot be obtained. However, there is no focusing problem in LCD, because each liquid crystal cell is turned on and off separately. This is why the same picture is so clear on the LCD screen. The LCD doesn't have to care about the refresh frequency and flicker, and the liquid crystal cell is either on or off, so the image displayed at such a low refresh frequency as 40-60Hz will not flicker more than the image displayed at 75Hz. On the other hand, the liquid crystal box of LCD screen is prone to defects. For the screen of 1024x768, each pixel is composed of three units, which are responsible for the display of red, green and blue respectively-so the total * * * needs about 2.4 million units (1024x768x3=2359296). It is difficult to guarantee that all these units are intact. Most likely, some of them have been short-circuited (with "bright spots") or disconnected (with "black spots"). Some customers may think that the perfect LCD screen should be bought at such a high price-unfortunately, this is unrealistic, and at most you can choose a screen with less obvious leisure time. The LCD screen contains some things that are not used in CRT technology. The light source of the screen is a cathode fluorescent lamp wrapped behind the screen. Sometimes, we will find an unusually bright line in a certain part of the screen. There may also be some indecent stripes, and a special bright or dark image will affect the adjacent display area. In addition, some fairly accurate patterns (such as shaking images) may appear ugly ripples or interference lines on the LCD screen. There is also a question of perspective or "observation angle". The reason why LCD has the problem of viewing angle is that it adopts the light transmission mechanism and adjusts the light passing through the screen. CRT is a luminous system. For CRT, the special material (phosphor) behind the screen can actively emit light. In LCD, although light can penetrate the correct pixel, oblique light can also penetrate the adjacent pixel, so when viewed from outside the normal viewing angle, the color will be seriously distorted. Advantages and disadvantages of liquid crystal display LCD is a new display device completely different from CRT in display principle. Compared with CRT display, LCD display has the following absolute advantages: 1. Small size and light weight. The structure of liquid crystal display is simple, even for large-screen liquid crystal display, the thickness of its finished product is less than 20 cm. However, the CRT display is low, and the polarization angle of the electron beam cannot be blindly increased because of the need to accurately control convergence and focusing. Therefore, the larger the viewing area, the greater the depth of CRT display. For example, the depth of a 19 inch CRT monitor exceeds 50 cm. This is a great waste of office space. Low power consumption, small heat dissipation, and the power consumption of LCD can be controlled below tens of uW/cm. Generally, the working power of 15 inch LCD is about 30W, and that of 17 inch CRT is above 100W. In addition, after long-term operation, the calorific value of LCD is much lower than that of CRT. 13. accurately restore the picture with sharp words. Whether visually or physically, LCD is essentially a full-screen display. It is completely different from the working principle of CRT, and fundamentally avoids the geometric distortion and nonlinear distortion of image restoration. However, due to the glass on the screen, the CRT display cannot be made too thin. At present, flat CRT displays are not completely flat. Even the flat-panel Terilon and flat-panel Diamondtron displays, which perform best in visual compensation, can only ensure "visual flatness" at a fixed viewing angle and viewing distance. Moreover, it is almost impossible to accurately control the electron beam to hit the corresponding phosphor spot after a long trajectory, and geomagnetic and surrounding electromagnetic fields are also very easy to interfere with the trajectory of the electron beam. Therefore, when the electron beam hits the center screen and edge of CRT display, the path and angle of electron beam movement are different. Even through complex dynamic focusing, the electron beam's landing point around the screen cannot be the same as the point in the center of the screen. Therefore, the focus of CRT display in the center of the screen is always better than that at the edge of the screen. Moreover, after the RGB three electron beams are deflected at a large angle, perfect convergence cannot be guaranteed in any area of the screen. Poor convergence may easily lead to the flooding of displayed text. LCD is directly addressed according to the video signal, so there is no possibility of poor focusing and convergence. Therefore, the displayed text is very sharp, and the picture will not appear color cast. 4. The picture does not flicker. Liquid crystal is a light-receiving display device. The work of the backlight is constant, and only when the screen content changes, the display content will change the distortion of the LCD box. Only the light of the backlight panel can affect the flicker of the picture, and the backlight panel works at a frequency of about 75K. So the LCD screen is very stable and there is no flicker. CRT is an active light-emitting display device, and phosphor will only emit light under the bombardment of electron beam. Even if the phosphor is bombarded at a frequency of 85HZ, staring at the screen for a long time will still cause eye fatigue due to the flicker of the phosphor. 5. Low radiation. Only the driving circuit of LCD may have slight electromagnetic leakage. However, the structure of CRT display is complex, and the electromagnetic leakage is different because of the different working frequencies of each component. The radiation produced by the high voltage of kinescope is harmful to human body even if it meets the most stringent TCO99 standard, but it is still harmful to human body after being exposed to radiation for a long time. Screen adjustment is simple and convenient. The principle of LCD determines that it does not need as complicated adjustment as CRT. Now the LCD can be adjusted to the best working state according to different working conditions only by pressing the automatic adjustment once, leaving you only to adjust the brightness and contrast according to your personal hobbies. On the other hand, every time a CRT changes its resolution or refresh rate, or even changes its display direction, it must undergo complicated adjustments. Compared with CRT, LCD has incomparable advantages, but it also has some obvious disadvantages: 1. High production cost and low yield. At present, the production technology of LCD is not fully mature, and the yield is still low. It takes a long time for the expensive LCD panel production line to slowly improve the yield, and the discarded LCD panels cannot be recycled, resulting in high production costs. Although the competition has suddenly intensified due to the active participation of many manufacturers in the LCD production industry in Taiwan Province Province, the price of LCD panels has dropped sharply in recent years. However, compared with the traditional CRT display, its price is still slightly higher. 1. The existence of defects. In view of the current limitations of LCD production cost and process, industry standards allow LCD to have obvious defects. In fact, CRT manufacturers now allow CRT to have defects, but due to the maturity of CRT production technology, the possibility of bad spots is very small, even if there are bad spots, they exist in the form of dark spots. It is difficult to find in CRT, an active light-emitting display device. However, the defects of liquid crystal display may exist in the form of dark spots or bright spots, which are very obvious in light-receiving display devices and seriously affect the use. 3. Small viewing angle. The light transmittance of liquid crystal makes the light on the backlight board not only penetrate the liquid crystal pixels vertically into the human eye, but also penetrate the nearby liquid crystal pixels at other angles. When the LCD screen is viewed beyond a certain line of sight angle, the contrast and color distortion will appear, and the yin and yang of the screen will be seriously reversed. Although the nominal viewing angle of many liquid crystal displays on the market is as high as 160 degrees in the horizontal direction and 120 degrees in the vertical direction, these parameters are often measured by manufacturers using different standards. The response time of LCD includes rise time (Tr) and fall time (Tf). Because the response time of LCD depends on the movement time of liquid crystal molecules, how to reduce the response time of LCD is still a problem to be solved. At present, the overall response time of mainstream LCD in the market is generally 40-60ms, which leads to obvious tailing phenomenon when LCD plays back video pictures or displays game dynamic pictures. Many manufacturers in the market often use the rise time of LCD as the overall response time to deceive consumers. 5. The maximum number of display colors is insufficient. At present, the LCD on the market can display at most 8-bit colors for each primary color of LCD pixels through FRC technology, that is, the eighth power of 2 =256 colors. Then the maximum number of colors that each group of pixels can display is 256 * 256 * 256 =1677 7216 colors. It can be seen that LCD is still a long way from CRT display which can be full color in color reproduction. If LCD can be greatly improved in these aspects, I believe it is no longer a slogan to eliminate CRT monitors. Display performance comparison table of various structures: liquid crystal display, cylindrical display, flat panel right-angle display, shadow mask flat panel display, shadow grid flat panel display, excellent text, excellent color, excellent medium, excellent all-plane, excellent medium, excellent safety regulations, excellent medium, excellent coating-excellent medium, excellent nonlinear distortion, excellent medium, excellent geometric distortion, excellent medium and corner focusing and convergence-excellent medium, excellent power consumption, excellent.