Many television and monitor manufacturers are now selling what they call LED TVs or LED monitors. This is somewhat of a misnomer, because these are still LCD displays. The difference between these and traditional LCD monitors is that they use a limited number of LEDs to enhance the picture created. A more appropriate way to describe these devices would be ‘LED-lit’ LCD displays.
Fluorescent tubes are used to light the screen on an LCD display. The result is that they are not very accurate in displaying black. The fluorescent tubes are always on, so sometimes light can escape and bleed into areas that are meant to be dark. This results in a picture that appears less sharp than a plasma display. Additionally, fluorescent tubes have a limited range in the variety of colors they can display.
The picture of an LCD display can be improved by using groups of LEDs to enhance the image. There are two types of such displays: back-lit LCDs and edge-lit LCDs. Back-lit displays have LEDs placed through the entire back of the display, while edge-lit displays have LEDs lined around the entire outside of the picture.
An advantage to edge-lit LCDs is that they can be extremely thin because the LEDs are only around the sides of the display. They are also cheaper than back-lit LCDs because there are much fewer LEDs.
A down-side to back-lit LCDs is that cost prohibits controlling the LEDs one at a time. Instead, LEDs are controlled in groups of clusters. This means that when a group of LEDs on an LED monitor are turned off, it may also darken an area of the display meant to be light. On the other hand, if a group of LEDs are turned on, it may brighten an area meant to be black.
True LED monitors are available. These displays use one LED for every single pixel, and each one is controlled independently. They are most frequently used outdoors and are very costly. An excellent example of a true LED monitor is the television in Times Square in New York City.
