Question

Color CRT Monitors

Answer 1

Color CRT Monitors

Color CRT Monitors are similar to CRT . The CRT Monitor display by using a combination of phosphors. The phosphors are different colors. The basic idea behind the color CRT monitor is to combine three basic colors- Red, Green, and Blue. By using these three colors, we can produce millions of different colors.The two basic color display producing techniques are:

1. Beam Penetration Method
2. Shadow-Mask Method

Beam–Penetration Method

It is used with a random scan monitor for displaying pictures. There are two phosphorus layers- Red and Green are coated inside the screen. The color shown depends on how far the electron beam penetrates the phosphorus surface. A powerful electron beam penetrates the CRT, it passes through the red layer and excites the green layer within. A beam with slow electrons excites only the red layer. A beam with the medium speed of electrons, a mixture of red and green light is emitted to display two more colors- orange and yellow.

Advantages:

1. Better Resolution
2. Half cost
3. Inexpensive

Disadvantages:

1. Only four possible colors
2. Time Consuming

Shadow–Mask Method

It is used with a raster scan monitor for displaying pictures. It has more range of color than the beam penetration method. It is used in television sets and monitors.

Structure: It has three phosphorus color dots at each position of the pixel.

• First Dot: Red color
• Second Dot: Green color
• Third Dot: Blue color

1. It has three different guns. Each for one color.
2. It has a metal screen or plate just before the phosphorus screen, named “Shadow-Mask.”
3. It also has a shadow grid just behind the phosphorus coated screen with tiny holes in a triangular shape.

Working

A Shadow Mask is a metal plate with tiny holes present inside a color monitor. A Shadow Mask directs the beam by consuming the electrons so that the beam hits only the desired point and displays a resulting picture. It has three different guns. These guns direct their beams to shadow mask, which allows them to pass. It is a task of a shadow mask to direct the beam on its particular dot on the screen and produce a picture on the screen. A Shadow Mask can display a wider range of pictures than beam penetration.

Advantages:

1. Display a wider range picture.
2. Display realistic images.
3. In-line arrangement of RGB color.

Disadvantages:

1. Difficult to cover all three beams on the same hole.
2. Poor Resolution.

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