LCD display(Liquid crystal display)

Liquid crystal display (LCD). It is a display that uses liquid crystal control technology to achieve color. Compared with CRT monitors, LCD has obvious advantages. Since light and dark are controlled by controlling whether light is transmitted, when the color does not change, the liquid crystal remains unchanged, so there is no need to consider the issue of refresh rate. For LCD monitors with stable images and no flicker, the refresh rate is not high but the image It is also very stable. The LCD display also uses the technical principle of liquid crystal to control the transmittance to make the bottom plate emit light as a whole, so it is truly completely flat. Some high-end digital LCD monitors use digital methods to transmit data and display images, so that there will be no color deviation or loss caused by the graphics card. There is no advantage of radiation at all, even if you watch the LCD monitor screen for a long time, it will not cause great damage to your eyes. Small size and low energy consumption are also unmatched by CRT displays.

The working principle of the LCD display: From the perspective of the structure of the liquid crystal display, the LCD display used is a layered structure composed of different parts. The LCD is composed of two glass plates, about 1mm thick, and 5μm containing liquid crystal material in between. Spaced evenly. Because the liquid crystal material itself does not emit light, there are lamp tubes as light sources on both sides of the display screen, and there is a backlight plate (or even light plate) and reflective film on the back of the liquid crystal display screen. The backlight plate is made of fluorescent material. Can emit light, its main function is to provide a uniform background light source. The light emitted from the backlight plate enters the liquid crystal layer containing thousands of liquid crystal droplets after passing through the first polarizing filter layer. The droplets in the liquid crystal layer are all contained in a small cell structure, and one or more cells constitute a pixel on the screen. There are transparent electrodes between the glass plate and the liquid crystal material. The electrodes are divided into rows and columns. At the intersection of the rows and columns, the optical rotation state of the liquid crystal is changed by changing the voltage. The liquid crystal material acts like a small light valve. Around the liquid crystal material are the control circuit part and the drive circuit part. When the electrodes in the LCD generate an electric field, the liquid crystal molecules will be twisted, so that the light passing through it will be refracted regularly, and then filtered by the second layer of filter layer and displayed on the screen.

Dot pitch: The meaning of the pixel pitch of LCD displays is similar to that of CRT. Dot pitch generally refers to the distance between two adjacent pixels on the display screen. The picture we see is formed by many dots, and the fineness of the picture quality is determined by the dot pitch. The dot pitch of the CRT depends on the design of the shadow mask or raster, the type of video card, and the vertical or horizontal scanning. The frequency varies, and the number of pixels in LCD displays is fixed. Therefore, when the size and resolution are the same, the pixel pitch of most LCD displays is basically the same.

Brightness: Brightness refers to the brightness of the screen. The unit is candela per square meter (cd/m2) or nits, which is a candlelight per square meter. At present, there are two ways to increase the brightness, one is to increase the light transmission rate of the LCD panel; the other is to increase the brightness of the background light, that is, increase the number of lamps.

Contrast: The contrast of a liquid crystal display is actually the ratio of brightness, which is defined as: in a dark room, the brightness under the white screen (the brightest time) divided by the brightness under the black screen (the darkest time). To be more precise, the contrast is the subtraction of the saturation of the white signal at 100% and 0%, and then dividing by the 0% white value with Lux (illuminance, that is, lux, lumens per square meter) as the unit of measurement ( 0% white signal is actually black), the value obtained. Contrast is the division of the darkest and whitest brightness units. Therefore, the brighter the white and the darker the black, the higher the contrast.

Viewing angle: It refers to the angle at which users can clearly observe all content on the screen from different directions. Since the light source that provides LCD displays has a certain directionality when output is refracted and reflected, color distortion will occur when viewed beyond this range, and CRT displays will not have this problem.

Resolution: LCD liquid crystal display and traditional CRT display, resolution is one of the important parameters. The resolution supported by traditional CRT monitors is more flexible, and the pixel pitch of LCD has been fixed, so the supported display modes are not as many as CRT. The best resolution of LCD is also called maximum resolution.