| LCD Monitors
and TV Monitors |
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| Essentially there are three different liquid-crystal technologies used in LCD monitors. No matter which technology is used, all LCD displays obey the same fundamental principles. Most versions of LCD are TFT LCD (Thin Film Transistor Liquid Crystal Display) which has a sandwich-like structure with liquid crystal filled between two glass plates. |  |
| Liquid crystal
was discovered by the Austrian botanist Fredreich Rheinizer in 1888.
"Liquid crystal" is neither solid nor liquid (an everyday
example are soap bubbles). In the mid-1960s, scientists showed that liquid
crystals when stimulated by an external electrical charge could change
the properties of light passing through the crystals. The early prototypes (late 1960s) were too unstable for mass production. But all that changed when a British researcher proposed a stable, liquid-crystal material (biphenyl). |
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| Backlit displays use one or more neon tubes to make up the so-called backlight, which illuminates the display from behind. The number of tubes may be limited to one for cheaper models, but you can find up to four in more expensive ones. Having two (or more) neon tubes doesn't really affect the picture quality in the least. Instead, the second tube acts as a backup in case the first one breaks. |  |
| In effect, this
considerably extends the monitor's working life, since a neon tube
generally lasts a mere 50,000 hours, while the electronics will keep on
plugging for 100,000 to 150,000 hours.
In order to ensure a uniform display, the light is redirected through a system of reflectors before it reaches the panel. Although it might not appear to be the case at first glance, the panel turns out to be incredibly complex. In fact, there are two panels, one on each side of the subpixels, each of which has been covered with a red, green or blue filter. In a 15" monitor, this adds up to 1,024 x 768 x 3 = 2,359,296 subpixels. Each RBG triad is controlled by a transistor that generates its own individual voltage. And this voltage, which can vary widely, causes the liquid crystals in each subpixel to move to a particular angle. The angle determines the quantity of light that passes through the subpixel, which, in turn, creates the image on the panel. The crystals' actual purpose is to deflect light so that it can pass a polarized filter before striking the display. If the crystals are arranged in the same direction as the filter, the light will pass through. On the other hand, if they are arranged perpendicular to the filter, the panel will remain black.
An ACTIVE LCD can show colors other than black and white. For example, a Computer Monitor or TV has an active LCD. In an active LCD, each of the pixels can be individually programmed to display color.
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