Fundamentals And Design
LCD stands for Liquid crystal display. An LCD basically consists of two glass plates with a special liquid between them. The special property of this liquid is that it rotates or "twists" the polarized plane of light. This effect is influenced by the electric field produced. So each glass plate is coated with a very thin film of metal. To get polarized light, you coat the bottom glass plate with polarized light foil, known as a polarized light plate. Another foil had to be applied to the bottom glass plate, but this time the plane of polarization was distorted by 90°. This is called a profiler.
In the idle state, the liquid twists the plane of polarization of the incident light by 90°, allowing it to pass unimpeded through the analyzer. So LCDS are transparent. If a specific voltage is applied to the metal film coating, the crystal will rotate in the liquid. This distorts the plane of light's polarization by another 90°. For example, the analyzer blocks light from passing through, making the LCD screen opaque.
TN, STN, FSTN, Blue Mode, Yellow-Green Mode
A liquid that distorts the plane of polarized light by 90° is called TN(distorted nematic phase). The STN(superdistorted nematic) liquid distorts the plane of polarized light by at least 180°. This improves the contrast of the display. The technique does, however, color the display to a certain extent. The most common colors are called yellow-green and blue patterns. There is also a gray mode that is more blue than gray in practice.
To counteract unwanted color effects, the FSTN technique uses additional foil on the outer layer, but this results in a loss of light, meaning the technique only works on illuminated displays.
However, different colors only occur when the display is either unlit or illuminated by white light. If there is any color lighting (such as yellow-green LED lighting), it overrides the color display. A blue-mode LCD with yellow-green LED lighting will always appear yellow-green.
Displays The Driver And Controller
The semiconductor industry now offers a very wide range of LCD drives. We usually distinguish between pure display drivers with no intelligence of their own, controllers with display memory and possible character sets, and microcontrollers with integrated LC drivers.
The pure display driver works in a similar way to the shift register. They usually have a serial input. They require external pulses, and in high frequency multiplexing operations, they require new display data to be continuously displayed to achieve the highest possible refresh frequency (MSM5219, UPD7225, HD44100, LC7942, etc.). An example of a real controller is the hd44780 for dot matrix display: once it receives ASCII, the controller manages the character set, memory, and multiplexing entirely on its own. The following controllers are widely used for graphics display :HD61202/3, HD61830, SED1520, SED1330, T6963.
All well-known uC manufacturers now offer one or more versions of the integrated display driver. They have their own display memory, which can be accessed by command.
IPS Technology
For tft displays, IPS technology broadens the viewing Angle compared to TN technology, which is widely used.
With full Angle color stability, improve the color stability of different perspectives. It provides the same color for a 90° direct view as it does for a 20° or 160° down view or top view. No more color transfer or reversal effects.
In addition, readability is guaranteed even in very flat viewing angles - no difference compared to standard tft displays with TN units.
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