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>> Liquid crystal display principle (LCM, LCD, module manufacturers) R & D 29th,May,2018
Historical evolution
In 1888, the Austrian botanist Leniz discovered a special mixture of substances. This substance is in the normal state between the solid and the liquid, not only that, it also has the dual characteristics of solid and liquid substances. At that time, there was no proper name for this material, so it was called Liquid Crystal (as the name suggests is a liquid crystal).
Liquid crystals of this substance were used for electronic display in 1968, 80 years after 1888.
In 1968, at the R&D center of R&D of RCA Company (the inventor of radio and television), engineers found that the liquid crystal molecules were affected by the voltage, changed the arrangement of their molecules, and could deflect the incoming light. phenomenon. Using this principle, RCA invented the world's first LCD screen and applied for a U.S. national patent. In the following years, liquid crystal display technology was widely used in general electronic products such as calculators, electronic watches, mobile phone screens, instruments used in hospitals, or screens on digital cameras.
Later, SONY and SHARP companies in Japan bought out the patent of RCA Corporation of the United States, and improved the liquid crystal display technology and widely promoted to various commercial fields.
Technical Application Editor
The LCD is an abbreviation of the English Liquid Crystal Display, and Chinese is called a liquid crystal display.
Laptops and LCD monitors
Whether it is a laptop or a desktop system, the LCD display used is a hierarchical structure composed of different parts. The last layer is a back light layer composed of a fluorescent substance that emits light. The light emitted by the backlight layer enters the liquid crystal layer containing thousands of crystal droplets after passing through the first polarization filter layer. Crystal droplets in the liquid crystal layer are all contained in a fine cell structure, and one or more cells constitute a pixel on the screen. When the electrodes in the LCD generate an electric field, the liquid crystal molecules are distorted, so that the light passing through them is refracted regularly, and then filtered through the second filter layer and displayed on the screen.
For simple monochrome LCD displays, such as those used on palmtop computers, the above structure is sufficient. However, for more complex color displays used in notebook computers, there is also a need for a color filter layer that specifically handles color display. Generally, in a color LCD panel, each pixel consists of three liquid crystal cells, each of which has a red, green, or blue filter in front of it. In this way, different colors can be displayed on the screen by the light of different cells. Almost all LCDs used in notebooks or desktop systems use thin film transistors (TFTs) to activate cells in the liquid crystal layer. TFT LCD technology can display clearer, brighter images. In the 1960s and 1970s, LCDs were inactive light emitting devices because of their low speed, low efficiency, and low contrast. Although they can display clear text, they often cause shadows when displaying images quickly, affecting the display of videos. It is only applied to Pocket PCs, pagers or mobile phones that require black and white display.
Like traditional CRT displays, LCDs used in desktop systems are also designed to receive waveform analog signals rather than digital pulse signals generated directly by the PC. This is mainly because the vast majority of standard graphics cards in the current desktop system still transmit video information from the initial digital signal to an analog signal and then send it to the display of the monitor. Although the LCD of the desktop system is designed to receive analog signals, the LCD itself can only process digital information. Therefore, after receiving the analog signal from the graphics card, the LCD needs to restore the analog signal to a digital signal before processing. In order to solve the display deficiency caused by the above problems, the latest desktop LCD adopts a special digital connector graphic card to directly transmit digital signals to the LCD display.
With the continuous maturity and development of LCD technology, the size of the display screen is gradually increasing. Traditional notebook computers use 8-inch (diagonal) fixed-size LCD displays. Now, TFT-based desktop system LCDs can support 14 to 18-inch display panels. Because the manufacturer determines the size of the LCD according to the size of the actual viewing area, rather than the size of the CRT, which is determined by the size of the tube, the size of the 15-inch LCD is equivalent to the size of a conventional 17-inch color display.
Dot matrix LCD
The display principle of the dot-matrix LCD In the digital circuit, all data is stored with 0 and 1, and different data operations can be performed on the LCD controller to obtain different results. For the operation of displaying English, since there are few types of English letters, only 8 bits (one byte) are required. For Chinese, there are more than 6000, so our DOS predecessors thought of a way to represent the Chinese characters, which is the internal code of Chinese characters, by using the 128 rarely used values of the ASCII table as two groups. The remaining low 128 bits are reserved for English characters, which are English internal codes. Then, after the inner code of the Chinese character is obtained, it is only a group of numbers. How can it be displayed on the screen? This involves the font of the text. Although the font is also a set of numbers, its meaning has a fundamental change with the meaning of the numbers. It uses the digits of each information to record the shape of English or Chinese characters, such as English. '''''''''''''''''''''''''''''''''''''''''''''''''' ''''''''''''''A''''''''''''''''''''''''''''''''''''' ''''''''''''''''''''''''''''The record in the font model shown in Figure 1:
Figure 2 "You" word chart 12864 dot matrix type LCD Introduction 12864 is a graphics dot matrix LCD display, which is mainly composed of a row driver / column driver and 128 x 64 full dot matrix LCD display. Graphic display can be completed, and 8×4 (16×16 dot matrix) Chinese characters can also be displayed.
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