15 Interesting Difference between Raster Scan and Random Scan

What is the difference between raster scan and random scan?

Raster and random scan are the mechanisms in which images are displayed on the screen of the monitor. These two terms tend to confuse a lot of people.

The guide provides the difference between a raster scan and a random scan. This will help you get to know the core difference between these two terms.

Difference between Raster Scan and Random Scan

What Is Raster Scan?

Raster scan is a scanning method where computer graphics move electron beam along with the monitor screen covering one line at a time from top to bottom.

The electron beams are normally set at both high and low levels to help generate patterns of illuminated spots as it sweeps around the screen.

Refresh buffer also known as frame buffer help to save the image definition specifically in the memory area that contains a combination of intensity values.

These stored intensities tend to be collected from the frame buffer and represented on the screen as one scan line at a time. Pixel or pel is the fundamental unit of defining a single scan line.

Advantages of Raster Scan

  1. Produce realistic images
  2. Generate million different colors
  3. Able to produce shaded scenes

Disadvantages of Raster Scan

  1. Tend to be quite expensive
  2. Have low resolution

What Is Random Scan?

The random scan is a scanning technique that uses electron beams to draw a line image on CRT. The image is normally made from a sequence of straight-line segments.

Each line on the screen is constructed by moving the electron beams from one point to another on the screen. Each point of the line can easily be defined by x and y coordinates.

Once the image has been drawn, the system goes back automatically and start to design all the lines of the image for 30 to 60 times in a second.

Advantages of Random Scan

  1. Generate smooth line drawings
  2. Have high resolutions
  3. CRT electron beams are directed only to the parts of the screen where an image is to be drawn.

Disadvantages of Random Scan

  1. Cannot display realistic shaded scenes

Comparison Chart: Raster Scan Vs Random Scan

Basic Terms Raster Scan Random Scan
Electron Beams Sweep on the graphic monitor to create one line at a time from top to bottom Directed only on the screen where the image is to be rendered.
Resolution Low High
Cost Quite expensive Quite affordable
Alteration Quite simple and easy Tend to be difficult
Picture Definition Stored as a combination of intensity values for all screen points Stored as a group of line constructions in a display file.
Realistic Display unable to display realistic shaded scenes Able to display realistic shaded scenes
Picture Rendering Use of pixel Use of mathematical functions
Application Suitable for creating realistic scenes Suitable for polygon drawings
Interweaving Commonly used Not used at all
Refresh Rates 60 to 80 frame per second 30 to 60 times per second

Core Difference between Raster Scan and Random Scan

  1. Random scan has a higher resolution while the raster scan has a lower resolution
  2. Raster scan is quite affordable whereas random scan is quite expensive
  3. The random scan is quite simple to alter while raster scan is tough to make modification
  4. The solid pattern of raster scan is easy to fill while that of random scan is difficult
  5. The refresh rate of a random scan is about 30 to 60 times per second while that of the raster scan is 60 to 80 frames per second.
  6. A raster scan uses an interlacing method while a random scan does not.
  7. Raster scan is suitable for realistic shade scenes while the random scan is restricted for polygon drawings.

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Comparison Video


The core difference between the raster scan and random scan is the drawing of an image whenever scan points are formed from the non-particulate radiation on the graphic monitor.

Understanding a raster scan vs random scan is quite important during the formation of realistic shade scenes and polygon drawings.

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