The device and principle of operation of LCD TV

LCD (Liquid crystal display) or LCD (LCD) TV, as they are called in the people - a TV with LCD display and backlight lamp. LCD, means that the display (monitor) are made on the basis of liquid crystals

TFT LCD (eng. Thin film transistor — thin film transistor) is a type of liquid crystal display which uses an active matrix-driven TFT. Amplifier for each sub-pixel (matrix element) is used to improve the performance, the contrast and sharpness of the display image

  • some history:
  • Liquid crystals was first discovered by Austrian botanist Rintaro 1888, but only 1930year, researchers from the British Corporation Marconi received a patent for their industrial application, however, the weakness of the technological base was not allowed at that time to actively develop in this direction.

    The first real breakthrough was made by scientists Ferguson and Williams from the American Corporation RCA. One of them created based on liquid crystals the temperature sensor using their selective reflective effect, the other studied the effects of electric field on nematic crystals. And now, at the end of the 1966, Corporation, RCA demonstrated a prototype LCD-monitor - digital clock. The world's first calculator CS10A was made in 1964 year, the Corporation Sharp, she, in October, 1975 year released the first compact digital clock with LCD display. Unfortunately, photos are not found, but this watch and the calculator is still remembered by many ab

    First LCD displays

    In the second half of 70's began the transition from vosmichastny LCD indicators to the production of matrix addressing (control) for each point. So, in 1976 company, the Sharp released a black-and-white TV with a screen diagonal of 5.5 inch, is made on the basis of LCD-matrix with a resolution of 160x120 pixels.

    The next stage in the development of LCD technology started in the 80-ies, when the devices have been used STN with high contrast. Then they were replaced by multilayer structure that allows to eliminate errors in the reproduction of color images. About the same time appeared active matrix technology a-Si TFT. The first prototype of the monitor a-Si TFT LCD was established in 1982 year by the corporations Sanyo, Toshiba and Cannon, but we, at this time, loved to play here with such toys with LCD display bk

    Toys of the USSR with the LCD displays

    Now LCDs have almost completely displaced from the market of CRT televisions, offering the buyer any sizes, from portable and small "kitchen", to huge, with diagonals of more than a meter. The price range is also very large and allows everyone to choose the right TV for their needs and financial capabilities

    New LCD TV

    Circuit design of LCD TVs is much more complicated than the simple CRT TV: miniature parts, multilayer PCB, expensive blocks... Now, who cares, TV with LCD panel without the back cover, and if you remove the special protective screens, you will see other areas of the chart, but it's better not to leave it to the experts bt

    diagram of a LCD TV
  • Device and principle of work:
  • Work LCD display (LCD) is based on the phenomenon of polarization luminous flux. It is known that the so-called crystals-Polaroids is able to pass only the component of the light vector of the electromagnetic induction of which lies in a plane parallel to the optical plane of the Polaroid. For the remaining part of the light flux Polaroid is opaque. This effect is called polarized light.

    If quite simple, imagine "light" in the form of small round balls, if his way to put the mesh with longitudinal cutouts (polarizer), then, after her, of "balls" will remain flat "pancakes" (polarized light). Now, if the second grid will be with the same longitudinal cut-outs, pancakes can "skip" through it and "Shine" further, if the second grid will have vertical slits, the light horizontal "pancakes" can not pass through it and "stuck" ad

    Filters in LCD

    When examined the liquid substance, long molecule which is sensitive to electrostatic and electromagnetic field and is able to polarize light, the opportunity to control polarization. These amorphous materials because of their similarity to crystalline substances for electro-optical properties, and also for the ability to take the form of a vessel, called the liquid crystals

    Structurally, the display consists of LCD (glass plates, between which are layers of liquid crystals), light sources lighting, pin harness and surrounds thecorps), often plastic, with a metal frame stiffness.

    Each pixel LCD matrix consists of a layer molecules between two transparent electrodes, and two polarizing filter, the polarization plane of which is (usually) perpendicular. In the absence of liquid crystals, light transmitted by the first filter, almost completely blocked the second.

    Device pixel LCD matrix

    The surface of the electrodes in contact with liquid crystals, specially treated for the initial orientation of the molecules in one direction. TN-matrix, these directions are mutually perpendicular, so the molecules in the absence of voltage are arranged in a helical structure. This structure refracts light in such a way that to the second filter plane of its polarization rotated, and through it light passes without loss. Except for the first absorption filter half of the unpolarized light, the cell can be considered transparent, though ... his loss is considerable.

    TN-matrix is open

    If the electrodes applied voltage, the molecules tend to line up in the direction of the electric field, which distorts the helical structure. The elastic forces oppose it, and in case of power cuts, the molecules return to their original position. With sufficient size of the field nearly all molecules become parallel, resulting opacity structure, the degree of transparency can be controlled by changing the applied voltage.

    TN-matrix closed

    As a light source (backlight LCD) are used in fluorescent lamps with a cold cathode (they are called that because the cathode is emitting electrons (negative electrode) inside the lamp is not necessary to heat above the ambient temperature that the lamp lights up). So it may look like a lamp for LCD TV, on the right photo - 'lamp Assembly in the work" TV with wide screen LCD display:

    Fluorescent lamps with a cold cathode

    Yourself lamp (bright white light) are located in a special Cabinet locks, behind them reflector, to reduce losses of light flux. In order to keep the LCD matrix is lit evenly (not striped like bulbs installed ap ), in front of the screen is lens, which distributes the luminous flux on the Mac. Unfortunately, this place is also occurs a considerable loss of "brightness" of glow lamps

    Lens in the LCD panel

    Modern LCD panels have a good viewing angle (about 160 degrees) without loss of image quality (colors, brightness), which is the most unpleasant thing they can see is that such a dead pixels, however, given the fact that their size is very small, one or two of these "burned" pixel does not greatly interfere with the viewing of films and programs, but on the screen - it can be quite frustrating bn

    Dead pixels in LCD panel
  • Advantages and disadvantages:
  • Compared to CRT TVs, LCD panels have excellent focus and clarity, no error information rays or violations of the geometry image, the screen never flickers, they are lighter and take up less space ay the disadvantages include the rather weak (compared to CRT) brightness and contrast, matrix is not as strong as the screen of the CRT, set digital brakes and glitches when analog or a weak signal, and poor treatment of the source material

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