Liquid Crystal Display (LCD) Television

Liquid crystal display television (LCD TV) is, as indicated by its name, a television using LCD technology (generally TFT), as opposed to cathode ray or plasma for its visual output.

Early LCD panel television had some difficulties displaying fast-moving action and had quite restricted viewing angles. These problems have largely been overcome in recent years, and the market for LCD televisions is booming, especially in Asia. For a long time it was widely believed that LCD technology was suited only to smaller sized televisions, and could not compete with plasma technology at larger sizes. This belief has been undermined by the announcements of ever-larger panels by companies such as Sharp Corporation, Samsung and LG.Philips. In October 2004, 40" to 45" televisions were widely available and Sharp Corporation had announced the successful manufacture of a 65" panel. Also in 2004, Samsung and Sony joined forces to build a factory in South Korea, intended to produce 60,000 panels a month, and in March 2005, Samsung announced an 82" HDTV TFT Panel. The world's largest 82-inch TFT-LCD developed at Samsung's 7G line. Viewing angle of 180° achieved by applying Samsung's proprietary S-PVA technology. 12.44 million thin-film transistors used to achieve full HD image quality of 6.22 million pixels. The main manufacturers have all pledged to invest billions of dollars in LCD production over the next few years, with televisions expected to be a key market.

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* Diagonal size: inches
* Contrast ratio.
* Degree viewing angle (horizontal/vertical): e.g.. 170/170, ....
* Luminance: cd/m².
* Response time.
* Dot pitch
* Max. resolution and color depth (e.g.. 24-bit : 16.7 M Colors)
* Digital Video Input Standard :HDMI (DVI-I is being phased out by tv manufacturers).
* Copy protection mechanism :HDCP
* Mount bracket: VESA

Universal capabilities

Modern LCD TV sets are geographically universal because they have a multisystem tuner, to display PAL, NTSC and SECAM norms. And they include an electronic (step-down & step-up) transformer that automatically can use 110/200 V AC indifferently and universal grounded adapter plugs.

Also, the vast majority are no longer just for TV and HDTV (DVB). They can also be used as a computer monitor with a VGA/DVI signal, although resolution support can vary widely.

Wireless AV kit (SmartLink)

Some newer LCD TV sets can connect to a host computer via a bluetooth or WiFi wireless link. See SmartLink, Streamium.

Teletext and Electronic Programme Guide

They generally include teletext and NexTView for EPG.

Developments in LCD televisions

TVs based on PVA and S-PVA LCD panels deliver quite good angle of view. They also deliver an adequate contrast ratio for viewing bright scenes; and also dark scenes in bright room. Dynamic contrast technique improves contrast when viewing dark scenes in a dark room. Alternatively, a TV from a creative electronics manufacturer will throw some light on the wall behind it to help make dark scenes look darker. However, PVA and S-PVA panels generally have difficulty with ghosting when going between different shades of dark colors.

Moving pictures on a CRT TV do not exhibit any sort of "trails" or "ghosting" because the CRT's phosphor, charged by the strike of electrons, emits most of the light in a very short time, under 1 ms, compared with the refresh period of e.g. 20 ms (for 50 fps video). In LCDs, each pixel emits light of set intensity for a full period of 20 ms (in this example), plus the time it takes for it to switch to the next state, typically 12 to 25 ms.

The second time (called the "response time") can be shortened by the panel design (for black-to-white transitions), and by using the technique called overdriving (for black-to-gray and gray-to-gray transitions); however this only can go down to as short as the refresh period.

This is usually enough for watching film-based material, where the refresh period is so long (1/24 s, or 41.(6) ms), and jitter is so strong on moving objects, that film producers actually almost always try to keep object of interest immobile in the film's frame.

Video material, shot at 50 or 60 frames a second, tries to actually capture the motion. When the eye of a viewer tracks a moving object in video, it doesn't jump to its next predicted position on the screen with every refresh cycle, but it moves smoothly; thus the TV must display the moving object in "correct" places for as often as possible, and erase it from outdated places as fast as possible.

There are two emerging techniques to solve this problem. First, the backlight of the LCD panel may be fired during a shorter period of time than the refresh period, preferably as short as possible, and preferably when the pixel has already settled to the intended brightness. This technique resurrects the much hated flicker problem of the CRTs, because the eye is able to sense flicker at the typical 50 or 60 Hz refresh rates.

Another approach is to double the refresh rate of the LCD panel, and reconstruct the intermediate frames using various motion compensation techniques, extensively tested on high-end "100 Hz" CRT televisions in Europe.

The best approach is probably a combination of two, possibly allowing the viewer to switch them on or off when viewing video- or film-based material.

Liquid Crystal Display (LCD) Television

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Universal capabilities

Developments in LCD televisions

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