1. Cathode Ray Tube (CRT) :
CRT is just like a vacuum glass tube. One end of the vacuum tube contains electron gun and the other end of the vacuum tube contains a screen which is coated with a pattern of dots or we can say phosphorus crystals. The light which is emitted by the phosphorus fades away very quickly from the screen. To maintain picture on screen for longer time the electron beam is redirected at the same points very quickly. Due to this there is the continuous glow of the phosphorus crystals on the screen. This type of CRT is also called as Refresh type CRT.
Various components which are used in CRT are:
- Electron gun
- Focusing System
- Deflection system
- Phosphorus Coated Screen.
2. Direct View Storage Tube (DVST) :
DVST is the resemblance of CRT because of the feature of drawing and displaying image. It uses electron gun to draw the image and to display the image it uses phosphorus coated screen. There is the use of phosphorus which has high persistence. To store the definition of image it does not use refresh buffer or frame buffer. In this the definition of picture is stored in the CRT in the form of positive charged distribution. Due to this reason, it is also been called as Storage type CRT. In this no refreshing is used due to which picture on the DVST will be seen for only 40-50 minutes before fading.
Various components which are used in DVST are:
- Electron gun
- Phosphorus Coated Screen
- Strong Mesh
Difference between DVST and CRT :
|1.||Use of Refresh Buffer||To store the picture definition, it uses refresh or frame buffer.||To store the picture definition, it uses grid which is called as storage mesh.|
|2.||Form of storage of picture definition||It stores the picture definition in the form of intensity values for different points on the screen.||It stores the picture definition in the form of positive charge distribution on storage mesh.|
|3.||Refreshing||Refreshing is required.||No refreshing is required.|
|4.||Colors Produced||It display wide range of colors.||It does not display colors.|
|5.||Use of Electron guns||It uses three electron guns i.e., Red, Green and Blue.||It uses two electron guns i.e., primary and flood gun.|
|6.||Flickering||In this the problem of flickering is observed; if the persistence of phosphor and refresh rate does not match.||In this there is no problem of flickering is observed.|
|7.||Modification of picture||In this the user can modify the particular portion of picture at any time.||In this the user cannot modify the particular portion of picture at any time. For modification, entire picture must be erased and redrawn.|
|8.||Use of Collector mesh||To control the flow of electrons, it does not use collector mesh.||To control the flow of electrons, it uses collector mesh.|
|9.||Application||CRT is widely used to display animations, realistic scenes and graphics etc.||DVST is only used for the line drawing applications.|