Since LCD and CRT display have different imaging principles, their screen resolution is two different concepts. No matter in high-grade or low-grade LCD, the resolution is a little insufficient. A LCD panel is made up of many luminous spots and can only support its own true resolution. For example, the real resolution of 15 inch LCD is 1024×768, while the user wants to use 800×600 resolution, which can be displayed in two ways. One is the center of the display, only the middle of the LCD 800×600 points will display the image, other areas of the luminous point is not luminous state, the whole picture in the center of the reduction. The other is simulation display, this way can make the image to use every pixel on the screen, but at this time the image will inevitably appear fuzzy, distortion phenomenon, will have a great impact on the display effect.
- Refresh rate.
For CRT, the screen image is produced by bombarding the phosphor with free electrons under the action of high voltage. Since the phosphor in the kinescope has a short luminescence time after being hit by the electron beam, the electron beam must strike the phosphor continuously to make it glow continuously, thus defocusing will occur. And the electron gun starts from the first line of the screen, scanning line by line from left to right, scanning the entire screen and then starting from the first line, which inevitably produces a 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 is using back light, the fluorescent tube light source, controlled by the liquid crystal molecules light deflection or through, due to the liquid crystal molecules with just two states – shut or open, so there is no refresh rate of the problem for the LCD, when open the display, LCD panel in each pixel are continuously, so there will be no LCD high-frequency flicker phenomenon. Of course, LCD displays also have the concept of refresh rate, but it is completely different from the CRT screen refresh rate and has no significant impact on performance.
- Volume and weight this aspect LCD has the absolute superiority.
Due to the large size is one of the developing direction of future display, CRT display screen sizes to 2x, image edge part of the image quality is prone to distortion, it is more important because of the tube will also increases with the increase of the display screen size (i.e., display to increase the thickness), so must make the volume and weight of the whole display would rise to square number, production also increased greatly. The LCD, however, not only has no effect on the picture quality when the screen size increases, but also its working principle determines that its thickness can be controlled within 20cm forever. Screen size and weight are not nearly as important as CRT displays.
- Green environmental protection.
Due to the complex CRT circuit, numerous components and internal high-power components, which not only consume a lot of energy, but also generate relatively obvious heat, we can see that there are heat dissipation holes on the shell of CRT display.So, electromagnetic wave interference cannot avoid, good CRT monitor chooses the picture tube with excellent performance and control circuit, the metal shielding net is added inside the machine case, can achieve the purpose of preventing radiation and resisting electromagnetic wave.At present, display manufacturers pay more attention to health and environmental protection. More and more CRT monitors have passed the strict certification of TCO95 and TCO99, as well as the special protective coating on the surface of the picture tube, so as to ensure that there is no harm to human body when used for a long time.
Liquid crystal displays TN (TwistNematic) is commonly used in black and white twisted nematic liquid crystal, its working principle: the nematic liquid crystal sandwiched between two pieces of glass and the glass on the surface of coated a layer of transparent conductive film first ITO (indium tin oxide) and used as electrode, and then in a glass coated with thin film electrode layer orientation PI (polyimide), so that the liquid crystal along a specific and parallel to the direction is arranged on the surface of the glass. The natural state of liquid crystal has a distortion of 90 degrees. Electric field can make liquid crystal molecules rotate. The birefring-index of liquid crystal changes with the direction of liquid crystal. As long as the right thickness is chosen to change the polarization direction of the polarized light by just 90 degrees, two parallel polarizing plates can be used to prevent the light from passing through at all. A voltage high enough to make the liquid crystal parallel to the electric field so that the polarization of the light does not change and the light passes through the second polarizing plate.Thus, the light and shade can be controlled.
Color LCD displays general use TFT (Thin Film Transistor) Thin Film Transistor liquid crystal display (LCD), its principle: deposits a layer of silicon on the glass substrate, by printing lithography processes such as made Transistor array, each pixel has a semiconductor switch, the process is similar to large scale integrated circuit. LCD perfusion between two pieces of glass again, because each pixel can through the point of pulse directly control, therefore, each node are relatively independent, and can undertake continuous control, this design not only improves the display speed, at the same time can be precisely controlled according to gray, so the TFT LCD color more vivid, is called the true color. TFT is divided into polysilicon, amorphous silicon and monocrystalline silicon.
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