12 Difference Between Raster Scan And Random Scan (With Comparison Table)

August 2022 · 5 minute read

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

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

Also Read: Difference Between Printer And Plotter

Difference Between Raster Scan And Random Scan In Tabular Form

BASIS OF COMPARISONRASTER SCANRANDOM SCAN
SuitabilityRaster scan is suitable for realistic display and well suited for displaying shading and color areas.  Random scan is suitable for engineering and scientific drawings. It is only restricted to line drawing applications.  
Electron BeamThe electron beam is directed from top to bottom and one row at a time on screen, but it is directed towards the entire screen.  The electron beam is directed only towards the part of the screen where a picture is required to be drawn.  
Picture DefinitionPicture definition is stored as an intensity value which results in it to have less resolution.  It stores picture definition as a set of line commands which results in high resolution.  
ResolutionRaster scan has a low resolution because picture definition is stored as a set of intensity value for all screen points.  Random scan has a high resolution because picture definition is stored as a set of line drawing instruction.  
Line DrawingsRaster system produces jagged lines that are plotted as discrete point sets.  Random system produces smooth line drawings because the CRT beam follows the line path directly.  
ApplicationIt is mainly used for photos. Programs like photoshop are Raster editing program.  Random system is mainly used for texts, logs, letterheads etc.  
DisplayRaster display has the ability to display areas filled with solid colors or patterns.  Random display only draws lines and characters.  
Refresh RateThe refresh rate is independent of picture complexity.  The refresh rate depends directly on picture complexity.  
Line DrawingScreen points/pixels are used to draw an image.  Mathematical functions are used to draw an image.  
Refresh RateRefresh rate varies from 60 to 80 frame per second.  Refresh rate depends on the number of lines to be displayed i.e 30 to 60 times per second.  
Picture Definition Storage  Picture definition is stored in refresh buffer also referred to as Frame Buffer.  Picture definition is stored as a set of line commands referred to as Refresh Display File.  
CapabilityThe capability of Raster system to store intensity values for pixels makes it well suited for realistic display of scenes containing shadow and color patterns.  Random systems are designed for line-drawing and cannot display realistic shaded scenes.  
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