1.Different types of LCD, LCM LCD products terminals

LCD refers to the liquid crystal glass panel that has been packaged with liquid crystal materials and leading electrodes, excluding LCD drivers and controllers, which is the most original state of all LCD products.

Glass products on the market for direct users are limited to low-density segment-type products.

LCM (LCDModule) liquid crystal display module, refers to the glass and LCD driver integrated into the LCD display products together, it provides the user with a standard LCD display driver interface (have four, eight, VGA and other different types), the user to operate according to requirements of the interface to control the LCD display correctly.

Compared with glass, LCM is a more integrated LCD product. For small-size LCD display, LCM can be more convenient to connect with various microcontrollers (such as microcontrollers).

However, for large-size or color LCD displays, generally take up a considerable portion of the control system's resources or cannot be controlled at all, such as 320×240256 color LCM, displayed at 20 fields/second (that is, 1 second full screen refresh display 20 times), and the amount of data transmitted in one second is as high as:

320×240×8×20 = 11.71875Mb or 1.465MB, if the standard MCS51 series single-chip microcomputer processing, assuming the repeated use of MOVX instructions to continuously transmit these data, considering the address calculation time, at least need to connect to the 421.875MHz clock to complete the data transmission, visible processing of the huge amount of data.

LCD terminal refers to all the devices that are relevant to the LCD display or functional modules are integrated into the LCD display products, because most of the work completed within the terminal display and control, so it only need to provide the user with a low standard serial interface can be convenient to realize all kinds of display function.

Because LCD products, especially large-scale LCM products, need to deal with a large amount of information, software, hardware design is complex, for the general engineer, is not a small challenge, and LCD terminal users from the cumbersome LCM research and development, debugging liberation, greatly speed up the development of the product progress, and due to the professional division of labor, to ensure the stability of the entire product.

Production and maintenance are more convenient.

In general, in order to facilitate the use of users, LCD terminals are often integrated with a keyboard and touch screen interface, making the design of human-computer interaction products more flexible and convenient.

Above all, to the computer display system analogy, equivalent to a display of glass tube, LCM is equivalent to a display, while LCD terminal is equivalent to the collection of all video card, motherboard and LCD monitors (such as Banks, logistics system widely used display terminal or POS terminal) user when choosing LCD products, mainly according to their own situation, combined with the following points to consider:

1, glass is only suitable for a conductor, the application of low cost, need an external drive or single chip microcomputer as the LCD driver, takes some system resources, but this is a more flexible way, the cost is low;

2, LCM products suitable for the batch is large, cost contradictory prominent application.Small and medium-sized batches, the general annual consumption of no more than 1000 cases, the cost of using LCM will be similar to the use of LCD terminals because of research and development investment, the loss of market opportunities, and even higher, and the maintenance of small batch products, production are problems.

3, LCD terminal is suitable for medium and small batch applications, especially in the project application is very common, because the profit of the project from the project efficiency, can use LCD terminal for system integration in the fastest time to realize your request.

LCD display areas, principle and classification of flat display device widely used with liquid crystal display (LCD), electroluminescent (EL), plasma display (PDP), light emitting diode (LED) display, vacuum fluorescent display devices (VFDS), etc.

LCD, is a certain temperature range was different in solid, liquid, and different from gaseous state of special material, it has peculiar to the anisotropy of crystal birefringence, and liquid liquid.

Generally can be divided into thermotropic liquid crystal and lyotropic liquid crystal two categories.

In the field of display application, the thermotropic liquid crystal is used, beyond a certain temperature range, the thermotropic liquid crystal will no longer show a liquid crystal state, the temperature is low, crystallization phenomenon, the temperature rises, it becomes a liquid;

The storage temperature marked by the liquid crystal display device refers to the temperature range of the liquid crystal state.

Liquid crystal display device has the following features (1) low power consumption, (2) the flat structure, (3) passive display type (no glare, does not stimulate the human eye, does not cause eye fatigue), (4) shows that large amount of information (because pixels can be done very small), (5) easy to colorize (on the chromatography can be very precise repetition), 6 no electromagnetic radiation (secret) safe to human body, for information,

Long life (LCD has almost no deterioration problem, so the life is very long, but the general LCD backlight life is limited, but the backlight part can be replaced).

Liquid crystal because of its anisotropic with electro-optic effect, especially the twisted nematic effect and the distortion effect, so can make different types of display devices, the following will introduce several common type of liquid crystal and its working principle: TN (TwistNematic) twisted nematic liquid crystal.

A layer of positive dielectric anisotropic liquid crystal is sandwiched between two glass substrates coated with a transparent conductive layer. The liquid crystal molecules are arranged parallel to the glass surface, and the arrangement direction is continuously twisted 90° between the upper and lower glass.

Then add a polarizer on the top and bottom, and add a reflector on the bottom, basically forming a TN type liquid crystal.

STN (SuperTN) type liquid crystal, the structure of the TN type liquid crystal is roughly the same, but the liquid crystal molecule is not distorted 90° but distorted 180°, and can also be distorted 210° or 270°, which is characterized by a better electro-optical response curve, which can adapt to more row and column drives.

TN type or the STN LCD, generally is the liquid crystal box of applied voltage, voltage reaches a certain value, the selection of rows and columns appear "show" phenomenon, so the more ranks number, request the higher driving voltage, therefore, often TN type or the STN LCD requires higher normal polarity driving voltage or low voltage polarity, also because of this,

TN and STN type liquid crystals are difficult to make high resolution liquid crystal modules (LCM).

So far, the STN LCD can only achieve pseudo color (generally the human eye can distinguish 218 or 262144 color color, so that 218 and more than 218 color color is called "true color, otherwise called pseudo color) shows that can realize the VGA, SVGA such as high resolution, but due to constitute their passive matrix, the matrix method is

Each pixel is actually a non-polar capacitor, which is prone to crosstalk phenomenon, so that the real active image cannot be displayed, and TFT liquid crystal completely solves this problem.

TFT (ThinFilmTransistor) is a thin film transistor active matrix liquid crystal display device, design a field effect at each pixel point switch tube, this would be easy to achieve true color, high resolution of liquid crystal display device.

Now TFT-type liquid crystals generally achieve more than 18bit color (218 colors), in terms of resolution, VGA(640×480), SVGA(800×600), XGA(1024×768), SXGA(1280×1024) and even UXGA(1600×1200) have become a reality.

It has been widely used.