The device of the LCD TV and the principle of operation

Judging by the number of models sold, LCD TVs have firmly taken a leading position in the market and in the hearts of viewers. To date, this type is chosen for the optimal price / quality ratio with minimal energy consumption. In this article we will talk about LCD TVs, reveal the secret and the principle of their work, the pros and cons.

REFERENCE. The name of these LCD devices comes from the English Liquid Crystal Display, literally it translates as a liquid crystal screen. LCD and LCD are the names of one type of TV.

Device: how the LCD TV works

The LCD or LCD system, as the name implies, consists of an array of elements of the same type - a system of liquid crystals, color filters - with the help of them an image is formed, a protective glass, a source of changing light.

The crystal system from the outside is evenly illuminated by a cold cathode fluorescent lamp. The operation of the panel itself depends on its location - a beam will pass or reflect. When there is no external influence, light freely passes through the polarizers. The substrate is visible. Liquid crystals (pixels) are controlled by applying potential difference (voltage) to them. The magnitude of this voltage determines how much the crystal will turn, and therefore the angle of polarization. The brightness depends on the degree of polarization. Accordingly, the crystal transmits more light, a dot on the screen is brighter. Then the light beam passes a polarizing filter perpendicular to the flow, a color filter and passes to the screen.

IMPORTANT. The pixels on the TV screen never go out, they can only change their polarization, i.e., the intensity of the glow. Therefore, the image does not disappear, but is replaced evenly frame by frame.

To summarize, it works like this - the luminous flux is filtered by a matrix consisting of many separate pixels that form a certain network. Three primary colors pass through this filter - blue, red and green, when combined with each other, a color picture is formed on the screen.

Notes

• Modern technology allow you to apply voltage to any crystal of each matrix layer. Each layer of the matrix is ​​important, but the main role is assigned to the first two, which are made of pure, without the addition of sodium, glass, called the substrate. It is between them that liquid crystals are located, and to be precise, their thinnest layer.
• Color picture - the result of using a matrix of passive filters, which, due to the separation of the white source, get three main ones - blue, red and green. Using their combination, any colors of the palette are obtained.
• If the polarization angle of the liquid crystal becomes 90º, relative to the passive filter, the light does not pass through it.
• Time response The crystal rotation speed is considered when voltage is applied to it. It is reduced by increasing the potential difference, faster is the turn. The clarity of the image when changing the frame depends on this speed. In order to make this parameter optimal, it is necessary to apply a voltage of maximum amplitude to the crystal.

Advantages and disadvantages of technology

Pros:

• Low power consumption - about 30 W / h. For example, CRT televisions consume 3 times more.
• During intensive work, heating is not more than 30ºС. Almost eliminated screen burnout.
• An anti-reflective coating is applied to the screen, which eliminates reflection, reflections, geometric distortions.
• It has a light weight, thin screen - does not take up much space, is mounted on a wall on a bracket.
• The absence of harmful electromagnetic radiation is not harmful to the eyes.
• The service life, on average, is twice as long as the plasma. Then the lamp is simply replaced, not the screen itself.
• Screen sizes can be from miniature (watches) to 100 inches.

Minuses:

• Primary colors suppress halftones and shades.
• There is a so-called loop problem, after-image.
• Great response time.
• Small, in comparison with plasma, viewing angle.

Some features

1. Contrast.Modern technologies, due to the polarization of the pixel, allow you to smoothly change the brightness in a wide range of 0-90º. Therefore, on LCD TVs, the dark colors are well displayed and easy to distinguish.
2. Brightness.As noted earlier - polarization cannot change instantly - it takes some time. Therefore, in the televisions of this system, the problem of displaying a rapidly changing, dynamic picture arises.
3. Limitation viewing angle.Due to the design of the LCD display, which has the form of a multi-layer sandwich, the viewing angle is limited. So, with a certain deviation of the eyes from the screen, the angle of polarization and, accordingly, the brightness of the crystal change. The color rendering and image contrast are falling.
4. Beaten pixelsThe crystals do not break, so the failure of the control transistor entails a dead pixel. A crystal, depending on the technology, can behave differently - if in the absence of voltage the light does not pass through it, then the point will be black, and when the maximum flow passes, it will burn.