Raster scan system & random scan system
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In a raster scan system, the electron beam scans across rows of the screen from top to bottom, turning intensity on and off to illuminate spots and form an image. The image definition is stored in a refresh buffer memory that holds intensity values for screen points. In a random scan system, an application and graphics package are stored in memory, and graphics commands are translated into a display file that a display processor accesses to refresh the screen. Graphics patterns are drawn by directing the electron beam along picture lines one at a time, positioning it between coordinate-defined endpoints to fill each line.
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Raster scan system & random scan system
- 1. RASTER SCAN SYSTEM & RANDOM SCAN SYSTEM
- 4. In a Raster scan system, the electron beam is swept across the screen, one row at a time from top to bottom. As the electron beam moves across each row , the beam intensity is turned on & off to create a pattern of illuminated spots. Picture definition is stored in memory area called the Refresh Buffer or Frame Buffer. This memory area holds the set of intensity value for the screen points.
- 8. An Application program is input and stored in the system memory along with a graphics package. Graphics Commands in the application program are translated by the graphics package into a display file stored in the system memory. This display file is then accessed by the display processor to refresh the screen. Some times the display processor in a random-scan system is referred to as a display processing unit or a graphics controller.
- 10. Graphics patterns are drawn on a random-scan system by directing the electron beam along the component lines of the picture. Lines are defined by the values for their coordinates endpoints, and these input coordinate values are converted to X and Y deflection voltages. A scene is then drawn one line at a time by positioning the beam to fill in the line between specified endpoints.