Advantages and disadvantages of CRT and LCD display

CRT display and liquid crystal display

All along, more perfect visual enjoyment is our pursuit. The traditional CRT display has experienced the development from black and white to color, from spherical surface to cylindrical surface to plane right angle, and finally to plane. In this acceleration process, the visual effect of the display has been continuously improved, and various indicators such as color, resolution, image quality, bandwidth and refresh rate have been greatly improved. At present, the mainstream flat panel displays have clear pictures, true colors, undistorted images and wider viewing angles, and the principle of human visual structure is fully considered in the design. A good flat panel display has a series of advantages such as long-term use and no eye fatigue.

It can be said that flat panel display is the highest level of CRT display development. However, because the basic working principle of CRT display is to bombard the display screen with free electrons excited by high voltage, the technology is very mature and there is not much room for development. Restricted by this, the traditional CRT display shows its own disadvantages in volume, weight and power consumption, but its own advantages are also very obvious, such as clear and realistic color reproduction, high image quality, large viewing angle, fast display speed without jitter, long life and durability. Many products have passed the stricter TCO 99 certification, which further embodies the humanistic technology of environmental protection and health. Looking at the CRT flat panel display market today, the main kinescopes used are Sony FD Trinitron, Diamondtron, LG Flatron and Samsung DynaFlat. In addition, although there are products using other picture tubes, they are rarely seen in the market and few people care about them.

Liquid crystal display has many advantages, such as small size, thin thickness, light weight, low energy consumption, no electromagnetic radiation, no flicker on the screen, avoiding geometric distortion, anti-interference, etc., and is favored by the industry and users. However, its price has remained high. With the breakthrough of key technologies and the substantial reduction of costs, its price has become approachable. Now the price of many 15 inch LCD monitors has dropped to about 3000 yuan. Just as 17 inch flat panel display began to be accepted by the market, the LCD market has also been officially launched.

LCD uses the photoelectric effect of liquid crystal, and obtains light and dark effects through external voltage control, refractive characteristics of liquid crystal molecules and the ability to rotate light, thus producing colorful colors and images and achieving the purpose of imaging. It is a typical light-receiving display. Completely different working principles make LCD and CRT displays have obvious performance differences, and at the same time, it easily solves the insurmountable shortcomings of CRT displays in terms of volume, weight, power consumption and environmental protection. And with the development of network environment and mobile office demand, LCD meets the requirements of more modern portability, environmental protection and energy saving.

Let's look at the advantages and disadvantages of CRT and low-end LCD in detail.

First, the resolution.

Because of the different imaging principles of LCD and CRT displays, their screen resolutions are two different concepts. Whether in high-grade or low-grade LCD, the resolution is a bit insufficient. The LCD panel is composed of many luminous points, which can only support its own real resolution. For example, for a 15 inch LCD, the real resolution is 1024×768, and the user wants to use the resolution of 800×600, so there are two display modes. First, the center display, only the 800×600 points in the middle of the LCD will display the image, and the luminous points in other areas will remain unlit, and the whole picture will be reduced in the center. The other is analog display, which can make the image use every pixel on the screen, but at this time, the image will inevitably appear blurred and distorted, which has a great impact on the display effect.

Second, the refresh rate.

For CRT, the screen image comes from the bombardment of phosphor by free electrons under high pressure. Because the phosphor in the picture tube will emit light briefly after being hit by the electron beam, the electron beam must constantly hit the phosphor to make it emit light continuously, so defocusing will occur. Moreover, the electron gun starts from the first line of the screen, scans line by line from left to right, scans the whole screen and then starts from the first line, which will inevitably produce flicker. Therefore, the refresh rate of CRT display screen must reach a certain speed, so that human eyes can not easily feel the flicker of the screen. LCD adopts backlight, that is, fluorescent tube as light source, and liquid crystal molecules control the deflection or passage of light. Because liquid crystal molecules have only two States-off or on, there is no refresh rate problem in LCD. When the display is turned on, every pixel in the LCD panel is constantly emitting light, so the LCD will not flicker at high frequency. Of course, LCD also has the concept of refresh rate, but it is completely different from CRT's screen refresh rate and has no obvious influence on performance.

Three, volume and weight

In this respect, LCD has absolute advantages. Because large size is one of the development directions of future displays, after the screen size of CRT displays reaches 2X inches, the picture quality at the screen edge is easily distorted. More importantly, CRT will grow with the increase of the screen size of the display (that is, the thickness of the display will increase), so the volume and weight of the whole display will inevitably increase by the square number, and the product cost will also increase greatly. However, when the screen size of LCD increases, it not only has no effect on the image quality, but also determines that its thickness can always be controlled within 20cm. The influence of screen enlargement on volume and weight is much less than that of CRT display.

Fourth, environmental protection.

Because the CRT circuit is complex, there are many components, and there are many high-power components inside, which not only consumes a lot of energy, but also causes obvious heating phenomenon, so all the CRT display shells we see have cooling holes. In this way, electromagnetic interference cannot be avoided. A good CRT display can achieve the purpose of preventing radiation and electromagnetic waves by selecting a picture tube and control circuit with excellent performance and installing a metal shielding net in the housing. At present, monitor manufacturers pay more attention to health and environmental protection. More and more CRT monitors have passed the strict certification of TCO 95 and TCO 99, and the special protective coating on the surface of CRT ensures that it will not cause harm to human body after long-term use.

In this respect, LCD has inherent advantages. It uses cathode fluorescent lamp as light source, the radiation value is almost zero, and only a small amount of electromagnetic waves come from the driving circuit. As long as the shell is sealed, electromagnetic waves can be prevented from leaking out. Because the calorific value is very low, the sealed shell will not affect the heat dissipation. Its power is only the same size CRT display? -1/3 or so.

Verb (short for verb) others

Other aspects include visual size, contrast, brightness and so on.

LCD is essentially a real flat panel display. The visual size of 15 inch LCD is the same as that of 17 inch flat CRT display, but the price will be much higher. Other aspects only need to pay attention to personal judgment when purchasing, so I won't say much here.

Judging from the current market situation, all the LCD monitors we can buy are low-end. The number and levels of colors that LCD can display are incomparable to CRT monitors, and users who have higher color requirements will definitely be dissatisfied. Due to cost and technical factors, the response time of middle and low-grade LCD signals can only be about 50 milliseconds. When doing some work that requires high screen refresh speed, LCD is often unsatisfactory. For example, when playing high-speed 3D games such as quakeIII and playing high-precision DVD, the smear phenomenon will be more serious because the LCD cannot refresh the screen quickly.

Relatively speaking, it is much cheaper to buy CRT than LCD, and the contrast of CRT display is much higher than LCD; At the same time, it also has faster reaction speed and stronger color expression; In addition, because CRT monitors have developed to a very mature stage, high-performance CRT monitors will have a longer technical life and will not be eliminated soon. At present, the LCD with a price of about 3,000 yuan has the possibility and opportunity of further improvement in technology. At the same price, we can even buy a good quality 19 CRT monitor. When you decide to buy, you should strike a balance between performance, price and personal needs!

Editor: Nowadays, for those friends who plan to buy monitors and have sufficient funds, many people feel a little helpless. When choosing cheap LCD and high-end CRT monitors, they often fall into a dilemma. In fact, the final answer to this question depends on you, because both LCD and CRT have their own distinctive characteristics. Therefore, when you have a difficult choice, you must first determine the purpose of using the computer. For example, you often have to write programs and manuscripts, and it takes a long time to search for information or browse the web, so the characteristics of LCD's environmental protection and good text display effect will bring you great convenience; However, if you are a graphic designer or a game enthusiast, a large-screen CRT display will never let you down, because CRT display is much better than LCD in color and delay, and you can get a larger display area at the same price as LCD. In a word, the dispute between LCD and CRT has just begun, but no matter who you choose in the end, as long as you can really make the best use of it, that is the best choice.

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