Liquid crystal display: what is LCD and how does it work?

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Liquid crystal display: what is LCD and how does it work?
Liquid crystal display: what is LCD and how does it work?

Learn what an LCD is, what it consists of, how it works, and how it works. Liquid crystal display (LCD) is a flat screen that reproduces an image using liquid crystals. It can be either monochrome or depict several million colors. A color image is formed using RGB triads (RGB is a model for the formation of colors from red, green and blue, English red, green, blue, respectively).

How are liquid crystal displays built?

LCD display consists of

from vertical and horizontal mutually perpendicular polarizing filters, between which liquid crystals are located, which, in turn, are controlled by transparent electrodes connected to the control processor, and from a color filter; there is a light source at the back (usually two horizontal lamps with bright white "daylight"). Liquid crystals are arranged in a specific order, creating a mosaic to form an image. The elementary particle of this mosaic is called a subpixel. Each subpixel is made up of a layer of liquid crystal molecules.

The principle of operation of the liquid crystal display

Polarizing Filters

- these are substances that transmit through themselves that component of the light wave, the electromagnetic induction vector of which lies in a plane parallel to the optical plane of the filter. The other part of the light stream will not pass through the filter. In the absence of liquid crystals between mutually perpendicular polarizing filters, it is the filters that would block the passage of light. The surface of transparent electrodes, which is in contact with liquid crystals, is treated for the initial geometric orientation of molecules in one direction. When current is applied to the electrodes, the crystals try to orient themselves in the direction of the electric field. And when the current disappears, the elastic forces return the liquid crystals to their original position. In the absence of current, the subpixels are transparent, since the first polarizer only transmits light with the required polarization vector. Thanks to liquid crystals, the polarization vector of light rotates and when passing through the second polarizer it is rotated so that the vector passes through it without interference. If the potential difference is such that the rotation of the plane of polarization in liquid crystals does not occur, then the light will not pass through the second polarizer and such a subpixel will be black. However, there is another type of operation of liquid crystal displays. In this case, the liquid crystals in the initial state are oriented so that, in the absence of current, the light polarization vector does not change and is blocked by the second polarizer. Therefore, a pixel that is not supplied with current will then be dark. And turning on the current, on the contrary, returns the crystals to a position that changes the polarization vector, and the light will pass. Thus, by changing the electric field, you can change the geometric position of the crystals, thereby controlling the amount of light that passes from the source to us. The resulting image will be monochrome. In order for it to become colored, you need to put a colored one after the second polarizing filter.

Color filter

Is a grid that consists of a mosaic of red, green and blue colors, each located opposite its own subpixel. As a result, we get a matrix of red, green and blue subpixels arranged in a strictly defined order. Three such subpixels form a pixel.The more pixels, the sharper the image. As the artist mixes the colors, the processor controls the subpixels to obtain the desired color shade. The ratio of the brightness of each of the three subpixels creates a certain pixel tint that they form. And the ratio of the brightness of all pixels forms the color and brightness of the image as a whole.

So, the basis of image formation on a liquid crystal screen is the principle of light polarization. The liquid crystals themselves play the role of a regulator, affecting the brightness and hue of the created image.

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