Pre-requisites: CRT, Refresh type output devices in Computer Graphics
The cathode ray tube (CRT) monitor displays with the help of a combination of phosphorus, as phosphorus exists in multi-color. Beam penetration is a method for producing color displays with CRT. The beam penetration technique uses multilayer phosphorus and achieves color by modulating the beam’s accelerating potential. It uses a random scan system to display color.
The arrangement of beam penetration CRT is similar to the normal CRT. The only unusual component is the use of multilayer phosphorus inside beam penetration. In multilayer phosphorus, a layer of red phosphorus is deposited behind the initial layer of green phosphorus. This method produces four colors only, red, green, orange, and yellow. The electron beam is produced by using an electron gun.
- If a low potential electron beam strikes the face, it excites only the red phosphor and produces red traces.
- If a high potential electron beam strikes the tube face, it excites the green phosphor and produces green traces.
- If an electron beam of intermediate potential and velocity, then it produces a combination of red and green i.e., orange and yellow.
However, the principle problem with this technique is the need to change the beam accelerating potential by an adequate amount in order to switch colors. When the accelerating potential changes, the deflection system must react to compensate. The hardware and software design must introduce delays between changes in color.
Advantages :
- It is a cheaper method.
- This method provides high resolution.
- It uses only one electron gun whereas the other method uses three or more electron guns.
- Easily identifies the type of electron i.e., high, low, or medium potential.
- A reliable method for producing colors.
Disadvantages :
- Produces only four colors.
- Not suitable for producing realistic views.
- Only suitable for the random scan.
- Color changing process takes time.
- The picture quality is quite poor.