How dose a LCD display work

Discussion in 'Archived Threads 2001-2004' started by Mike Bledsoe, Jul 5, 2002.

  1. Mike Bledsoe

    Mike Bledsoe Stunt Coordinator

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    I was just wondering if anyone knows how a LCD television works? I know how a plasma and CRT works but have never saw any where how a LCD works.
     
  2. Vince Maskeeper

    Vince Maskeeper Producer

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    I would say that LCD as a projection method is resonably similar to plasma in the general term. Think a projection panel with a grid of individual LC pixels that can be changed color based upon electrical current.

    The pixels are fired into various colors, light is shined thorugh or reflected off the panel- and an image is produced. In the case of LCD it is subtractive light (the LCD pixel is the opposite color of the produced color- blocking everything but the color you want to display).

    -Vince
     
  3. TomMadden

    TomMadden Agent

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    An LCD element works in an inverted way compared to a CRT or plasma. LCD displays work on the principle of removing light, rather than adding it. The backlight of an LCD panel is always a constant white light. When a charge is applied to an LCD element, the crystals inside it align themselves to have a polorizing effect on the light. That is, they block the light. The more current applied, the more light that is blocked. Thus, an LCD screen that is black has the most current applied to each element and an LCD screen that is white has no current applied to each element. This is why black isn't very black on some LCD screens - the screen was built in such a way that the LCD element could not block all of the light coming from the backlight.

    For a color LCD screen, the standard LCD elements have color filters in front of them. So, to do red on an LCD screen, the blue and green elements are turned on full, while the red element is turned off completely. This allow the backlight to shine through the red element's filter creating a red color. Contrast this with a CRT - which produces red by shutting off the blue and green guns and turning on the red one for that element. As one might imagine, the color management hardware and software is very different for the two.

    The backlight in computer and other small LCD displays is typically a flourescent tube (usually more than one for larger displays). Laptop computers typically have very, very tiny tubes for this - it's no wonder that the backlight is one of the greatest power drains on the laptop's battery. For an LCD projector, the backlight is the projector's bulb, of course. It shines a light on a small, high density LCD display.
     

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