Difference Between Raster Scan And Random Scan

What Is Raster Scan?

In 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 and off to create a pattern of illuminated spots.

What You Need To Know About Random Scan

• Raster scan is suitable for realistic display and well suited for displaying shading and color areas.
• The electron beam is directed from top to bottom and one row at a time on screen, but it is directed towards the entire screen.
• Picture definition is stored as an intensity value which results in it to have less resolution.
•  Raster scan has a low resolution because picture definition is stored as a set of intensity value for all screen points.
• Raster system produces jagged lines that are plotted as discrete point sets.
• It is mainly used for photos. Programs like photoshop are Raster editing program.
• Raster display has the ability to display areas filled with solid colors or patterns.
• The refresh rate is independent of picture complexity.
• Screen points/pixels are used to draw an image.
• Refresh rate varies from 60 to 80 frame per second.
• Picture definition is stored in refresh buffer also referred to as Frame Buffer.
• The capability of Raster system to store intensity values for pixels makes it well suited for realistic display of scenes containing shadow and color patterns.

What Is Random Scan?

In Random scan, display electron beam is directed only to the areas of screen where a picture has to be drawn rather than scanning from left to right and top to bottom as in raster scan. It is also referred to as vector displays as it draws picture one line at time. It can draw and refresh component lines of a picture in any specified sequence.

What You Need To Know About Random Scan

• Random scan is suitable for engineering and scientific drawings. It is only restricted to line drawing applications.
• The electron beam is directed only towards the part of the screen where a picture is required to be drawn.
• It stores picture definition as a set of line commands which results in high resolution.
• Random scan has a high resolution because picture definition is stored as a set of line drawing instruction.
• Random system produces smooth line drawings because the CRT beam follows the line path directly.
• Random system is mainly used for texts, logs, letterheads etc.
• Random display only draws lines and characters.
• The refresh rate depends directly on picture complexity.
• Mathematical functions are used to draw an image.
• Refresh rate depends on the number of lines to be displayed i.e 30 to 60 times per second.
• Picture definition is stored as a set of line commands referred to as Refresh Display File.
• Random systems are designed for line-drawing and cannot display realistic shaded scenes.

Also Read: Difference Between Printer And Plotter

Difference Between Raster Scan And Random Scan In Tabular Form