A Color CRT Monitor display images by using a combination of phosphor that emits different light. A combination of RED, GREEN AND WHITE Phosphors is used to emit different color of light. The two basic technique for producing colors in CRT monitors
- Beam Penetration method
- Shadow mask method
Beam Penetration Method
- This method is used in random scan monitors.
- In this method , only two layers of phosphors are coated onto the CRT screen. (RED & GREEN)
- Beam penetration method is only able to produce 4 colors.
- A beam of electrons penetrates through the red layer and excites the inner green layer which in intermediate produces the Orange and Yellow color.
- It gives high resolution of the image.
- It is less costly as compared to shadow mask.
- The color of the image depends on how far the electrons excite the outer RED layer and Inner GREEN Layer.
The Quality of the pictures with the Beam penetration method is not good as with other method.
Shadow Mask Method
- This method is used in Raster scan monitors.
- In this method , CRT has three phosphor color dots at each pixel position. One dot emits a RED light, another emits a GREEN light and third emits a BLUE light.
- With shadow mask method , millions of colors can be generated.
- This type of CRT has Three electron guns , one for each color dot, and a shadow mask grid just behind the phosphor- coated screen.
- It gives low resolution of images.
- It is more expensive than other methods.
- In this Method, there are no such criteria for producing colors. It is used in computers, color TV etc.
The quality of the images is far better then the beam penetration method.