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Cathode Ray Tube(CRT) in Computer Graphics


Posted Date: 22-May-2010  Last Updated:   Category: General    
Author: Member Level: Gold    Points: 20


My this article contains informatin about computer graphic system.



In computer system commonly used display device is video monitor the operation of most video monitors based on it. The following display devices is used in computer graphics :
Refresh Cathode ray Tube
Color CRT Monitors
Direct View storages tubes
Plasma panel Display
Refresh Cathode Ray Tube : It consists of the following main parts : CRT, Electron gun, Focusing system, Deflection system, phosphor coated screen
Working of CRT : The electrons are emitted by electron gun. These electrons pass through focusing and deflection system. The beam of electron strike at specified points son the phosphor coated screen. When it falls on screen small spot of light is generated at each position where beams strikes .
The light of phosphor fades after sometime. So electrons beam is repeated quickly to redraw picture in the screen on same point. The phosphor in screen is of difference persistence. The turn persistence is used to represent time internal during which phosphor emit after beam is removed.
The phosphor may have low or high persistence. If persistence is low then it will be suitable for animation. If persistence is high it will be used for display highly complex pictures in CRT we use cathode to heat the electrons. Cathode is heated by filament. The electrons are accelerated toward phosphor coating by high positive voltage

Control Grid : is used to surround the cathode. Grid is cylindrical in shape. It is made up of metal. Grid has hole at one end, through which electrons get escaped. The control grid is kept at lower potential as compared to cathode, so that a electrostatic field can be created. It will direct that electrons through point source , so process of focusing will be simplified. The brightness of picture can be controlled by adjusting follow of electrons and current in beam.
Focusing : is done by special focusing structure made up of two or more metal plates. The plates have different potential. An accelerating structure is also used in combination with focusing structure. Accelerating structure has two metal plates, the plates are perpendicular to beam can pass through these plates because holes are provided at center of plates. The plates are kept at high potential so that beam can be accelerated at desired velocity.
Deflection System : It is also called as yoke. It is located at neck of CRT tube. It is responsible for addressing of CRT. Deflection system consist of two pairs of coils. One coil control horizontal deflection, whereas other control vertical deflection. The deflection coils deflect the information rapidly so that it can be displayed clearly on screen without any flickering.
Phosphors : A variety of phosphor available. Phosphor has different colors . Color generally used is white . White color is suitable for dark background.
It should have small size .
It should have high efficiency in term of electric energy converted into light. It should have distance to burning under prolonged excitation
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