What Is The Difference between Raster Scan and Random Scan?

What is the difference between raster scan and random scan? Raster scan refreshes the entire screen systematically, while random scan refreshes only the specific areas where changes occur.

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.

Subscribe To My Channel Please

Difference between Raster Scan and Random Scan (With Table)

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

What Is Raster Scan?

Raster scan is a method of displaying images on a screen through a systematic and sequential process. In this technique, the electron beam moves horizontally and vertically across the screen, scanning each pixel in a predetermined pattern.

The scanning typically begins at the top-left corner and progresses from left to right, row by row, until the entire screen is covered. As the electron beam scans each pixel, it illuminates phosphors on the screen, producing the desired image.

This systematic approach ensures that the entire display is refreshed multiple times per second, creating a coherent and continuous visual experience for the viewer. Raster scan technology is widely used in modern computer monitors, television screens, and other display devices.

It enables the representation of intricate graphics, text, and multimedia content by breaking down the image into a grid of pixels and systematically rendering each pixel in a specific order. The uniform scanning pattern of raster scan contributes to the consistent and smooth presentation of visual information on electronic displays.

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?

Random scan, also known as vector scan or stroke writing, is a method employed in displaying images on a screen through a different approach than raster scan. In contrast to the systematic and sequential scanning of raster technology, random scan involves the direct tracing of the electron beam along the paths of displayed shapes. Rather than covering the entire screen in a predetermined pattern, the electron beam moves to specific points to draw lines and shapes as needed.

This method is particularly suitable for displaying graphical elements where changes occur in localized areas. Unlike raster scan, random scan only refreshes the parts of the screen that require updating, making it more efficient for certain applications. Random scan technology was historically associated with older or specialized display systems, and it is characterized by its ability to render intricate graphics and geometric shapes with precision.

However, as technology has advanced, raster scan has become more prevalent in mainstream display devices, while random scan is now found in niche applications where its unique capabilities are still relevant.

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

Main 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.

You May Also Like:

Similarities between Raster Scan and Random Scan

1. Both raster scan and random scan are methods for creating images on a screen.

2. Both techniques utilize an electron beam to illuminate phosphors on the screen.

3. They are employed in the field of display technology.

4. Both can render geometric shapes, although the methods differ.

5. Both contribute to the refresh rate of the displayed content.

6. Both raster and random scan technologies have been used in the history of display systems.


In conclusion, the disparity between raster scan and random scan unveils the fascinating diversity in display technologies that have shaped the evolution of visual computing. Raster scan, with its systematic and sequential approach, has become the bedrock of modern display devices, gracing computer monitors and television screens worldwide. Its ability to refresh the entire screen in a methodical manner ensures a coherent and immersive visual experience, making it ideal for rendering detailed graphics, text, and multimedia content.

On the other hand, random scan, or vector scan, introduces a different paradigm by directly tracing the electron beam along the paths of displayed shapes. This targeted approach is particularly adept at rendering intricate graphical elements efficiently, refreshing only the specific areas of the screen where changes occur. While historically associated with older or specialized display systems, random scan continues to find its niche in applications where precision in drawing geometric shapes is paramount.

As we reflect on these two technologies, it’s evident that their differences arise from distinct approaches to image rendering. Raster scan embraces a comprehensive, all-encompassing strategy, while random scan opts for a selective and efficient method. The choice between them depends on the specific requirements of the application at hand, with raster scan dominating mainstream displays and random scan thriving in specialized environments where its unique capabilities are prized.

In the dynamic landscape of display technologies, both raster scan and random scan have contributed significantly to the visual experiences we enjoy today. As we move forward, it’s intriguing to consider how emerging technologies will continue to redefine and expand the possibilities in the ever-evolving realm of visual computing.

More Sources and References

Leave a Comment