In liquid-cristal (ZHK) дисплее material is between two glass panels. Are they Herewith used электрооптические characteristic fluid crystal, placed in electric field. From the other types display he differs that that uses the light from external source.

ZHK display can be made very fine and comsumes very little energies. The Fluid crystal - an intermediate condition between fluid and hard phase material - conducts or does not conduct the light depending on attached to him voltages or temperature. Thence follows that, controlling voltage or the temperature in determined area, possible create the bright scenes.
In spite of obvious advantage in size and энергоэффективности, using ZHK monitor сопутствует the row of the undecided problems: контрастность, increase the corner of the review, rather high cost.

ZHK display with active matrix (AM-LCD) use described above principle of the action for element of each colour. Cvetovosproizvodyaschie elements in such дисплее affect the friend on friend. For removal of this defect are used магнитодиоды.
Thin-film transistor (TFT) ZHK-display.

In thin-film semiconductor liquid-cristal monitor TFT LCD (Thin Film Transistor Liquid Crystal Display) liquid-cristal material is located between two layers glass. The Light gets through crystals in accordance with direction, in which are turned their molecules. Polyarizacionnye filters adjust the passinging light through them. When presenting the voltage of the molecule of the crystal occupy the position, under which light meets with поляризационным by filter straight or under углом 90 . The Voltage forces the fluid crystals to work like shutter cameras, blocking or allowing passing of the light VWXbe drafty filters. High efficiency monitor TFT LCD is conditioned by small consuption material and energy. High KPD and low level of the electromagnetic radiation allows to refer these monitors to category device, "friendly" to surrounding ambience.

In TFT LCD display for each color element is used 1 transistor and 1 capacitor, which provide presenting the voltage on element at period of the included condition of the transistor. The Locked transistor insulates the element before moment, the following its cut-in. For making the scene is here used characteristic ZHK material to conduct or block the light depending on attached voltages.

Structure liquid-cristal TFT monitor

Film from amorphous silicon

Most broadly in thin-film transistor technology is used amorphous silicon. This is conditioned by low cost glass material, which become be used due to низкотемпературному state of working amorphous silicon. Other his(its) advantage are connected with high gain factor on current, small current rest and high stability.

Back illumination

ZHK-display does not radiate, but works as optical shutter. So for reproducing the scene he is required external source of the light, and behind ZHK panels is situated излучатель.

Color filter

The Color filter presents itself liquid-cristal panel, in which red, green and blue elements are located in determined order, forming color matrix. The Color filter is located on upper or lower glass panel of the monitor. Three color elements are initiated independently friend from friend and in combinations define the colour given area.

Relative hole

The Aperture attitude (the relative hole) presents itself attitude area scenes, or efficient area of the aperture, to the general area of the matrix ZHK display. Than this attitude more, that brighter display, since increases the area, occupying color element. Increases as well as контрастность. The Relative hole is an important factor ZHK display, used for estimation his(its) quality.

Corner of the review

Kontrastnosti scenes ZHK monitor changes depending on corner, under which lead his(its) observation. The Corner of the vision characterizes this change. He can be expressed through change the contrast at offset upwards/downwards and to the right/to the left. Reception capacity of the fluid crystal in big degree depends on corner of the slopping falling light. Thereby, change the contrast are defined by factor of the issue at the input and output.

The Interference is expressed in negative взаимовлиянии pixels, when a pixel actuated by voltage influences upon nearby passive. This phenomena characteristic of for simple panels of the type STN basically, however and in panel with active matrix noticeably small influence to interferences

Brightness

For measurement of brightness ZHK display are used such values, as NIT, Foot Lambert and кандела on square metre - kd/m (cd/m). Brightness display is defined by brightness of the back illumination and reception capacity to panels. Reception capacity of the fluid crystal low so for reinforcement of brightness of the scene use the aperture lattice with big relative hole, поляризационные to panels and color filters with high reception capacity or prisms.

Pluses

Scaling the scene under multiple-mode work

• Practically full absence of the radiation. This is one of the main of the particularities LCD-monitor. In any modern CRT-monitor except electromagnetic is present and x-ray radiation appears at collision of the electron with surface) that in the aggregate very harmful influence upon health of the user.
• The Absence of the twinkling of the scene. Does Not get tired the vision and does not the nervious voltage, unlike CRT-monitor. In LCD-monitor scene is updated line by line so it does not tremble practically under any reasonable importance of the frequency of the trained unrolling.
• The Flat scene on all directions. First, after turning with CRT-monitor, appears the strange feeling that screen LCD-monitor concave inside, but in a certain time of the work with him this sensation will disappear.
• Clearness and ideal geometry of the scene. (But only in one mode, which corresponds to the physical permit of the matrix) Are absent such defect, inherent some CRT-monitor, as несведение and расфокусировка лучей, which bring about origin расплывчатости scenes. Also am absent any geometric distortion.

When use the monitor in permits different from permits of the matrix occurs the transformation of the scene(for this exist two methods:

• центрирование (Centering) - for image of the scene is used only that amount of the pixels, which necessities for imaging with more low permit(scene occupies only necessities amount pixels on medium of the screen)
• the sprain (the Expansion)- are used all pixels of the screen, but because of this appear small distortion, and grows worse the sharpness of the scene.

Impossibility equally to work in permits different from physical permit of the matrix possible in some measure to refer and to defect. At choice of the monitor it is necessary to take, that beside which physical permit of the matrix corresponds to that permit, with which You are going to to work.

Frequency of the renovation

If beside passive matrixes this defect then for active matrixes, котроые are used for production ZHK-monitor for personal computer, this sooner advantage on their own congener. Modern LCD-monitors allow liberally to play in dynamic plays and look видеофильмы.

Size ZHK-panels corresponds to seen area a screen

In change from CRT-monitor, beside which size by seen user of the area of the screen less (at the average on 1") than size of the tube.

Small gabarit sizes monitor

That allows to save the precious free place on Your worker table. But small weight of the monitor allows liberally to dispose him(it) on wall as picture.

Possibility of the tumbling of the screen on 90 with simultaneous u-turn of the scene

(Given particularity is present only beside a part LCD-monitor). Usual альбомный (Landscape) display easy changes in portrait (Portrait). This much comfortable when work with greater document (on screen possible completely to fit the sheet of the format A4) and Web-page. The Tumbling most scenes is realized with the help of special programme, which is delivered together with monitor. Exist also models CRT-monitor with possibility of the tumbling of the screen, but meet they much seldom.

Possible minus

"Possible" since pluses, about which was said above, there is always, but минусы can come up for dependencies from separate copy or producer of the monitor.

Brightness

With brightness are bound several defects beside LCD-monitor.

• The First defect this insufficient spare to brightness beside some models monitor that negative tells on quality of the scene.
• The Second reveals itself when use not one, but two or more lamps подсветки LCD-monitor. Herewith enough in a complicated way obtain even distribution to brightness of the scene on the whole area of the screen. Appearing light and dark heel well mark on even gray background. Possible is considered difference of brightness separate area screen before 25%(the criterion is changed depending on producer). Also beside monitor with диагональю 14" and more screen consists not from one, but from two matrixes that else more intensifies unevenness to brightness of the scene. To define, approaches You brightness of the concrete copy necessary to compare him(it) with congener.

Kontrastnosti

The attitude of brightness is Defined between the most bright white and the most dark black colour on screen LCD-monitor. Some display enough powerfully suffer from defect of the depth of the contrast. The Contrasting correlation 120:1 is considered good (provides reproduction alive saturated colour). On given moment already quite a few LCD-monitor that have a contrasting correlations 300:1 and above, which is used for exact image monochrome halftone.

Insufficient corners of the review

Active ZHK-matrixes (either as other their varieties) possess rather unpleasant effect, which reveals itself at look at matrix under углом, exceeding definite sign, then colour become pale or are distorted. The Essence the problem is, optical system, forming brightness of each pixel of the screen, has a concrete corners, guaranteeing full passing by light from the source of all her(its) component. ZHK-monitors with low possible corners of the review rather uncomfortable in work, since happens to constantly to keep a check on position eye for screen of the monitor. But since time possible corners review beside new ZHK-monitor have all greater importances. At present from this problems nearly disposed, t. ch. on many monitors possible глядеть under углом in 40 degrees and more.

Nerabotayuschie or wedged to pixels

Technology of the creation TFT very complex because of that that number used transistor very great and enough in a complicated way obtain the acceptable percent suitable product (in monitor of the companies Samsung Electronics are used thin-film ZHK-panels, made with accuracy 99,999%). For matrix with physical permit 1024х768 (practically all 15" ZHK-monitors) total amount transistor is 3*1024*768=2359296 pieces. For revealing неработающих (always black or brightly white points - the most irritating from fault) and wedged pixels (the points, which on white background glow red, green or blue colour) necessary to get on screen of the monitor absolutely black, white, red, green and blue background on which will well be a mark all types неработающих or wedged pixels, which, depending on colour on screen, will vastly differ from their own соседей.
The Producers install the rates on limiting amount transistor, which can be off-hour in LCD-дисплее. The Truth, beside each producer its opinion about that, what amount transistor can not work. The Company Samsung Electronics for ZHK-monitor are incorporated following standards on amount неработающих pixel for 15" monitor (at presence greater amount fault pixels monitors subjects to change): dark points - 7шт., light points - 1шт. ( given at the time of writing the article, hereinafter can change in smaller side). At choice of the monitor advisable to examine several copies and choose that, beside which least amount of the fault pixels.

Razbalansirovka phases, problem to synchronizing signal

On quality of the scene LCD-monitor powerfully affects adjustment such parameter, as synchronizing and phase.
The Controller LCD-monitor, for determination of the number pixel in line, uses the strobe синхросигнал, which frequency must correspond to the frequency of the signal, enterring from graphic adapter. If they do not coincide on screen can appear interleaving vertical light and dark bands, scene can begin to tremble or in general схлопывается in one line. The Phase to have charge of focusing of the scene. The Result разбалансировки phases can be a flutter of the screen and hardly observable quickly running horizontal dark bands.

Razbalansirovku phases are under usual work to notice enough in a complicated way. So for check of correctness of the adjusting the phase necessary to get on screen of the monitor even light-gray background and then under разбалансированной phase will is well seen ripples, appearing because of quickly running dark horizontal bands. Also, typical разбалансированной to phase, ripples possible to notice if use OS Windows in "Panels zadach/taskbar" reveal the menu "Pusk/start" and choose the substitution "to Terminate rabotu/shut Down".
Necessary without fall to do checking the phase and try to dispose of garbling the scene on screen if such are present, and if this does not manage to do, that abandon to buying given copy.

Double transformation of the signal

CRT-monitors are an analog device so in usual personal computer are fixed видеокарты with analog output. But LCD-monitors - completely digital device, but since with video card have an analog output, producers have to provide compatibility LCD-monitor c CRT-monitor, but as a result joining the digital monitor with computer is realized with the help of analog converter. Originally digital signal is converted in analog in видеокарте (first, DAC-transformation), but then analog signal is transformed in digital analog-digital converter most LCD-monitor (second, ACP-transformation). Herewith possible appearance of the different distortion and vastly increases the cost, as most видеокарты, so and monitor (as a result of users pay the additional money for additional deterioration quality).
On given moment already exist the models with digital interface, but they wide-spread else less than LCD-monitors themselves.

Author: А. V. Savin It Is Added: 01.05.2007