There are two types of flat-screen televisions. These are LCD (Liquid Crystal Display) TVs and PDPs (Plasma Display Panels). LCD TVs and plasma TVs both work differently from the traditional Cathode Ray Tube (CRT) TVs. Unlike CRT TVs, flat-screen TVs do not use an electron beam running back and forth behind the screen to produce a picture.
An LCD TV and a plasma TV use the same technology of switching millions of tiny picture elements called pixels on and off to produce a moving picture. Each of these pixels is colored red, green, or blue, depending on the light that falls on them. The main difference between an LCD TV and a plasma TV is how their pixels are switched on and off.
In an LCD TV, a colored picture is produced because the pixels use liquid crystals that rotate polarized light. In a plasma TV, the pixels are microscopic fluorescent lights electronically turned on and off.
How Does an LCD TV Work
At the back of the LCD TV is a large bright light that is turned on when the TV is switched on. In front of the light are millions of pixels that are further separated into sub-pixels. Each sub-pixel is colored red, green, or blue. Each pixel is composed of a tiny liquid crystal placed between two glass polarizing filters. When the light at the back of the LCD TV is turned on, the liquid crystals in each pixel are also switched on. These crystals rotate to permit some of the rays of light to pass through the polarizing filters.
Depending on which sub-pixels the light touches, the pixel lights up and produces a certain color. Without the rotating liquid crystals, no picture will be produced because the polarizing filters block out all the light passing through the pixels.
A pixel has its own separate transistor. This transistor switches the pixel on and off as many times as needed every second.
How Does a Plasma TV Work
A plasma TV is made up of two sheets of glass. Between these two sheets of glass are millions of pixels filled with two kinds of gas, namely neon and xenon. Each pixel is coated with a chemical called phosphor. This chemical is what makes the pixels red, green, or blue.
When the plasma TV is electronically turned on, the electricity causes the colored phosphors to produce light. This in turn paints the moving pictures on the screen.
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