LED-backlit LCD display
LED backlight or LED backlight or LED under light, is a variant of the through - or illumination of the LCD display. It comes with so-called LED TVs (so-called LED TVs ) and TFT computer monitors used. Are used white or colored to white miscible emitting diodes (LEDs ), which are arranged behind the liquid crystal elements.
Design and operation
Large technical problems in liquid crystal displays ( LC-Displays/LCDs ) with conventional cold cathode fluorescent lighting, so-called CCFLs, put the relatively low contrast value and the uneven illumination to plasma and CRT devices dar. The reason for this is due to the construction of LCD technology: the individual image-forming liquid crystal elements, much like a film, backlit using fluorescent tubes. Usually several CCFL tubes are required for this, which are arranged beside each other or one another. The difficulty is to distribute the light evenly. For this purpose one uses a light-conducting plastic, designed to produce a uniform light source. Despite this technique different light areas may appear on the monitor, type of construction usually in the places where there are the tubes.
With the help of LED backlight, this problem can be largely avoided many small distributed over the entire surface of the monitor LEDs produce better illumination. Thus, the image representation is vivid. There is also the possibility that one uses a lot of LED elements, which can be controlled separately. So you can, dim or turn off individual parts of the illuminated surface for displaying a deep black separately. This makes the image more contrast. Thus, the advantages of LED and LCD are used.
Another advantage of LED - backlit monitors is the long life of LEDs. In CCFLs often occurs flickering or failure of the light source. In addition, the LED elements are more energy efficient, which allows a longer battery of the notebook. Many new notebook models have screens with this technique; also in desktop monitors and televisions, it has now taken hold.
With newer television screens currently two different techniques are used:
- In the lateral arrangement (English: Edge LED, from edge: edge ) few LEDs are attached to the sides of your monitor and light from there the entire surface. Advantage is a low housing depth, but often problems will occur with uniform illumination.
- In two-dimensional array ( engl.: direct LED or full array with local dimming ) to illuminate the entire image surface light emitting diodes the image from behind. The image can be illuminated more uniformly and the contrast with local dimming of individual LEDs ( behind those dark areas ) are greatly increased.
Advantages of LED backlight ( white LED )
- Low power consumption
- Possibility of a flatter design of the equipment
- Higher contrast with local dimming
- Long life
Disadvantages of LED backlight ( white LED )
- The increased contrast applies only to devices with so-called local dimming. For devices with Edge - LEDs are available with respect to the static contrast no differences.
- At too low selected by the manufacturer PWM frequency the image of sensitive people may be perceived as flickering