The monitor combines the appropriate amount of
red, green, and blue light to form the specified color on the screen. Additional signals
are used to synchronize the horizontal and vertical scanning so that pixels are
drawn in the correct position.
Cathode ray tube (CRT)
CRT monitors draw pixels by shooting electron beams at colored phosphor dots
coated onto the inside of the front glass panel, which then glow. It takes a significant
amount of energy to create the electron beams, and X-rays are produced as a side
effect. In order to shield the user from these X-rays, a significant amount of lead is
embedded into the glass of the CRT. Large electromagnets are used to bend the electron
beams as the display is scanned.
CRTs are a proven, reliable, and inexpensive technology, and they present a clear
image over a wide range of viewing angles. However, their large size, the use of lead
in their construction, their high energy usage, and concern over X-ray and electromagnetic
radiation has caused many people to consider alternatives.
Liquid crystal display (LCD)
LCDs use light-gates made out of tiny liquid cells adjacent to a polarizing filter. By
applying an electric current to the liquid, it can be polarized, allowing more or less
light to flow through the light gate.
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