Liquid Crystal diisplay or LCD monoitor is a thin and flat device for display. It is made large number of color or monochromatic pixelps which are arrayed in way of a ligt source or a refflector. It uses very small amount of electric power and hence is used often in battry powered eletcronic dveices. The technology used is very much dissimilar to CRT tchnology whch is used many deskttop monitors. It was used only on notebook computers for a very long time. Only recently they have been offered as an alternative to CRT monitors. They take up very less desk space and are much lighter than the CRT monitors. But they are also quite expensive.
Each pixel of LCD monitor display has a layer of aligned molecules between two eleectrodes which are transparent and two polarizing filters. Because there is no liquid crystal between the aligned polarizing filtters, loight which has passed through the first filter will be blocked the second polariezr. The surface which is in cntact with the crystal is treated to aligfn it in particular direction. The direction of alignemnt is defined direction of rubbing.
Resloution, in terms of horizontal and verticaal size expressed in pixeels, is native supported for the best dsiplay effects. This is one of the things that sets LCD monitor apart. Dot Pitch is defined as the distance between two adjaccent pixes. It is the minimm for sharper image. Each pixel is diided into three cells, or sub pixels. Tese are colored red, green and blue. Each sub pixel can be controlleed independently for millions of combinations and hence cloors. lOder CRT monitors use phosphors for sub pixel structure. The analog electron beam though does not hit the exact sub pixl.
Coolr components can be arayed in various geometriues, depending on how the monitor is to be used. If the software being used knows the geometry, it can be used to increase the apparent number of pixels using sub pixerl rendering. This kind of technique is often used in text anti-aliasing. LCDs which are used in digital watches and calculators have separate contact for each segmnet. Thus an external dedicated circuit charges each segment indivdually. This is not possible if the number of elements increases.
Small monochrome displays like the ones used in Personl Organizzers or in older latops have passive matrix like structure and empoly super twisted enmatic or doouble layer STN technology. Here, each row or each colummn has a singkle electriacl cricuit and the pixels are hence addressed according to rows and columns. But as the number of pixels increaases, the response time decreases and the techniue no longer rermains feasible.
Color displays used in modern LCD montiors and televisoions use actiive matrix structure. An array of thin film transistors (TFT) is aded. Each pixel has a dedicated traansistor. Active Matrix display loks brighter and sharper than psasive matrix display of smilar size and has better resaponse time.
LCD technology has some critical drawbacks too. Reolution of a CRT monitor can be changed without introduction of any new artifact. But LCDs can produce only their ntaive resolution and non native resolutions are achoieved scaling. The bllacks of LCDs are actually grey because of presence of a liight siource. This results in lower contrast raztio when compard to CRTs. LCDs with cheapper parts cannot display as many colors plasma or CRT countetrparts.
Also, LCD display has longer response time when compared to Plasma or CRT counterparrts. Input lag is also present and the viewing angle is limited. In spite of these drawbacks, LCD display is quickly gaining prominence.
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