What Is an LCD Backlight?

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LCD stands for liquid crystal display. LCD technology previously appeared in digital watches, calculators and other small electronics before flat screen televisions. By itself, liquid crystal produces no light. Instead, the material illuminates with the assistance of a backlight. The product seen on a television screen is the result of a backlight shining on liquid crystal to display a picture.

Backlight

  • Simply put, a backlight for an LCD screen is a lamp. All LCD televisions require a lamp, which serves as the backlight for the LCD picture. Depending on the television model, an LCD might require one or two lamps to provide an adequate light source. Because lamps eventually burn out with use, LCD television manufacturers usually create an easy replacement slot where lamp bulbs can be replaced with little effort.

Absence of Backlight

  • Liquid crystal, whether in a television, watch or computer monitor, still functions the same without a backlight. However, with the absence of a backlight, the LCD will not project a visual display. For example, a television that is hooked up to cable programming receives a signal from the cable feed and creates a picture on the screen. That picture illuminates for the viewer to see with the aid of a backlight lamp. If you remove that backlight, the cable feed still sends a signal to the television to create a picture on the screen, but the viewer cannot see the picture because the liquid crystal needs the backlight for illumination.

How LCD Works

  • Manufacturers of LCD products need to stabilize or immobilize liquid crystal before placing it in a product. This is done by sealing the liquid crystal between two plates. To visualize this, imagine a microscope slide where the object under magnification is placed between two glass slides. LCD plates work the same way. To change the shape of the liquid crystal, an electrical current is sent to it.

LCD Pixels

  • An LCD picture consists of millions of tiny pixels which together form a visual display. The light source behind each pixel is the backlight. The white backlight passes through a polarizer and a layer of glass. From there, the light passes through the liquid crystals. Electrodes which coat the plates holding the liquid crystal send vibrations to the plates to determine how and what light passes through. Once through, the light passes through a colored lens filter that produces a red, green or blue light. Finally, once the picture passes through each step in the pixel-producing process, it emits a visual display to the viewer.

Technical Issues

  • Although LCD televisions create stunning high-definition pictures, liquid crystal still shows limitations. One problem is that liquid crystal offers a slower reaction time than other television displays such as plasma. As a result, rapid movements on an LCD television often produce blurry images. This effect is known as ghosting. Additionally, LCD televisions have difficulty producing dark images on the screen. When a screen image should show black, light leakage from the backlight often causes the black screen to illuminate slightly. Thus, LCD televisions struggle to produce pitch black or very dark contrasts.

References

  • Photo Credit televisor lcd image by enens from Fotolia.com
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