Raster Scan Systems !
It is the most common type of graphics monitor based on television technology. In a raster scan system, the electron beam is swept across the screen, one row at a time from top to bottom. When electron beam moves across each row the beam intensity is turned ON and OFF to craete a pattern of illuminated spots. Picture definition is stored in a memory called frame buffer which holds the set of intensity values, which are then retrieved from the frame buffer and pointed on the screen one row at a time as shown in figure below:
At the end of each line the beam must be turned off and redirect to the left hand side of the CRT, this is called Horizontal Retrace. At the end of each frame, the electrin beam return to top left corner of the screen to begin the next frame called Verticle Retrace as shown in figure below:
- produce realistic images
- also produced different colors
- and shadows scenes.
- low resolution
- electron beam directed to whole screen