LCD displayWhat is the basic structure of the LCD display principle? I think a lot of people are not very understand it, perhaps many people know what is the LCD display, know the definition of which, but the structure and principle of the LCD display are not clear, then the following from these two aspects to analyze, bring you to understand!
Basic structure of LCD display
- A vertically oriented polarizer polarizes the incident light.
- The glass substrate has transparent electrodes of indium tin oxide (TO). The shape of the transparent electrodes will determine the address of the dark color that is displayed when the LCD is powered on with no light passing through. Vertical stripes are etched into the substrate so that the liquid crystal is oriented in the same direction as the incident light after polarization.
- Twisted Nematic (TN) type liquid crystal.
- A glass substrate with a common transparent electrode film (ITO) on which horizontal stripes are etched so that the liquid crystals are aligned in the horizontal direction.
- A horizontally biased polarizer that blocks or allows light to pass through.
- A reflective surface that reflects light back to the observer.
The following is an introduction to the main role of these components there is an important device backlighting: as the name implies is placed behind a light source; the simplest example is the night light-emitting publicity picture, in fact, we look at the picture on the spray chart, the picture behind the light source is called backlighting. Similarly, the bottom of the LCD display also has a piece of equipment to provide a light source, usually made of light-emitting diodes, so it is also called LED backlight.
Display Principle of Liquid Crystal Display
The basic principle of liquid crystal display is to place the liquid crystal between two conductive glass substrate, in the upper and lower two glass substrate under the action of the electrode, so that the liquid crystal molecules undergo a twisting deformation, to change the polarization state of the light beam through the liquid crystal box, to achieve the switch control of the backlight beam. If you add a color filter between the two glass substrates, you can achieve color image display.
If an external electric field is not applied to the liquid crystal box, since the twisted spacing of the liquid crystal molecules in the box in the TN type liquid crystal display device is much larger than the wavelength of the visible light, when the polarization direction of the incident linearly polarized light is in the same direction as that of the arrangement of the liquid crystal molecules on the surface of the glass, the direction of its polarization will be distorted by 90° due to the twisted deformation of the liquid crystal molecules after passing through the entire liquid crystal layer. It is emitted from the other side in a transmissive state. If a voltage is applied to the liquid crystal box at this time and reaches a certain value, the long axis of the liquid crystal molecules will begin to tilt in the direction of the electric field, and all the liquid crystal molecules between the two electrodes in the liquid crystal box will be rearranged in the direction of the electric field except for those on the surface of the electrodes. At this point, the 90° spin function disappears and the spin effect disappears between the orthogonal polarizers, making the device unaffected by light.
LCD liquid crystal display technology also varies brightness depending on the voltage, and the color displayed by each LCD display sub-pattern depends on the color filtering procedure. Since liquid crystals themselves have no color, the various colors are produced using color filters rather than sub-patterns, and the sub-patterns can only be adjusted for shades of gray by controlling the intensity of the light passing through them. Only a few active matrix displays use analog signal control, while most use digital signal control techniques. Most digitally controlled LCD displays use an eight-bit controller that can produce 256 levels of gray scale. Each sub-picture element is capable of expressing 256 levels, so you get 256 colors, with each pixel capable of expressing 16,777,216 finished colors. Because the human eye can't perceive linear changes in brightness, and the human eye is more sensitive to changes in low brightness, this 24-bit color scale isn't exactly ideal, and engineers use pulse-voltage adjustments to make the color changes look more uniform.
In a color LCD, each pixel is divided into three cells, or subpixels, with additional filters marking red, green and blue. These three sub-pixels can be controlled independently and the corresponding pixel can produce thousands or even millions of colors. Older CRTs used the same method to display colors. The color components are arranged according to different pixel geometries as needed.