Computers: The Past, Present, and Future -- Present

Computers: Present: Tutorial

CRT Monitors

This is a typical CRT monitor.

CRT or Cathode Ray Tube monitors are composed of an "electron gun" and a specially coated screen. When the monitor receives the instruction from the video adapter, the electron gun "shoots electrons" onto the screen according to the instructions. So your saying, "that’s great so why do we see the stuff we do". Well, when the electrons hit the screen, they react with a chemical surface made of phosphors. The reaction of the electrons with the phosphors produces a small glow. The combined glow of the entire screen produces the visible image. The beams of electrons generally travel across the screen in a vertical manner.

Quality
The quality of a monitor is measured in two ways. The dot pitch is a measurement of the sharpness of the monitor. The dot pitch is generally a fraction of a millimeter and is the shortest distance between two dots of the same color. Generally, most monitors dot pitch is below .28mm. A common rule of thumb, the lower the dot pitch the sharper the picture, hence the better the quality. The second quality measurement is the refresh rate. The refresh rate is a rating of the frequency the monitor "refreshes" the image on the screen. Since the chemical reaction only lasts for a few milliseconds, the monitor must refresh multiple times per second. The more the monitor refreshes the less the user experiences the "flickering effect". The refresh rate is measure in Hertz (Hz), and a monitor will normally have a refresh rate of about 60Hz or more.
Now that you know how CRT monitors work, let’s learn about LCD screens.

All material and images on these pages are copyright Joseph,Ed. This page was developed for the Thinkquest1999 competition.