COLOR SYSTEMS

Monitors & TV

Computer monitors and televisions make use of the 3 primary colors of mixing light. The amazing thing about these video screens is that they are composed of thousands or even millions of very tiny dots or stripes of red, green, and blue.

In this case, the three primary colors are not actually combined until our eyes blend the tiny dots together. The dots are so small that our eyes cannot pick out the individual dots from a distance. So we see objects of many different solid colors. If we take a magnified look at the screen, all we see are the individual dots or stripes of red, green and blue.

Magnified view

Television screen pattern
of	red	-	green	-	blue
stripes (or dots)

Some Video tubes use dots, while other models use stripes, and still others use rectangular segments as shown here.

		So where do all the different colors come from when we look at a video or computer screen? They come from the various brightness levels of the tiny dots.
If only a group of dots for red and green are lit up, we should see a shade of yellow in that part of the picture. If these green dots are not so bright, the color should appear a shade of orange.
		A cut-away view through the back of a video or television picture tube
DIAGRAM OF HIGHLY ENLARGED COLOR STRIPES.

The scanning beams from three electron guns hit the tiny color phosphor dots. This causes them to glow with various amounts of brightness according to the way the TV picture looks.

Of course, there's also a great deal of electronics and invention behind these rapidly blinking color dots. In fact, the dots blink at various brightness levels so fast that we cannot even tell that only three dots are being lit at a time.

How do the 3 scanning electron beams hit only the right color dots? Right before the beams hit the screen, they must go through a barrier with many tiny holes called a "shadow mask". There is one hole for each group of 3 primary color dots. So there are thousands of holes too.

			shadow mask
		electron guns

The three electron beams are positioned so that the 3 beams can pass through the same hole at the same time, but at 3 different angles. The beam for blue will only be able to hit blue dots. The beam for red can only hit red dots. The beam for green can only hit green dots.

In some of the diagrams above, a screen with stripes is shown. Usually the openings in the shadow mask will match the shape of the color phosphors, whether they are dots, stripes, or rectangular segments.