Search This Blog

23 March 2023

Raster Scan Vs Random Scan | Difference | Comparison

Most of the displays nowadays used for pictures of an object on the desktop or computer monitor are raster scans and random scans. An electron beam is moved across the screen in a raster scan from top to bottom, one row at a time. This is the main difference between a raster scan and a random scan. Only the areas of the screen where a picture need to be drawn are targeted by the random scan electron beam. Let us discuss some more differences between the Raster Scan Vs Random Scan with the help of the comparison given below.

What is Raster Scan?

A Raster scan involves moving the electron beam across the display one row at a time from top to bottom. The intensity of this electron beam is switched on and off as it moves across each row, resulting in a pattern of illuminated spots on the screen. In a memory location known as the refresh buffer, the picture definition for a rater scan is kept. The set of intensity values for each screen point is stored in this memory area. A pixel is a single screen point. The electron beam then moves back to the left side of the screen to start displaying the next scan line at the conclusion of each scan line. A raster scan system is exemplified by the pen plotter.

What is Random Scan?

In contrast to random scans, which scans from left to right and top to bottom, random scan direct the electron beam only to the area of the screen where the image will be displayed. The vector display, stroke writing display, or calligraphic display are other names for the random scan system. In a random scan, In a random scan, the refresh display file, a region of memory holds the picture definition as a collection of line drawing instructions. The system cycles through the set of commands in the display file, drawing each component line in turn, to display a specified image. Once all the line drawing commands have been carried out, the system loops back to the first line command in the list.

Raster Scan Vs Random Scan | Difference between Raster scan and Random scan


Because the CRT beam directly follows the line path, the Raster scan system generates jagged lines that are plotted as discrete point sets and the Random system generates smooth line drawings.

Solid pattern

A solid pattern is easy to fill in a raster scan, but a solid pattern is difficult to fill in a random scan.


The Raster scan system is less expensive, Random scan system is more expensive.


Modification is difficult in a raster scan, but modification is easy in a random scan.


In a Raster scan resolution is low because the picture definition is stored as a set of intensity values for all screen points, Whereas The resolution of the random scan is high because the picture definition is stored as a set of line drawing instructions.


Shadow mark technology is used in a raster scan, and Beam penetration technology is used in a random scan.

Refresh rate

Refresh rates do not depend on picture complexity in a raster scan system, But the refresh rate depends directly on picture complexity while using a random scan.


Referencing rate uses interlacing, Random scan does not use interlacing.

Easy to suit

Raster scan is suitable for realistic display and well suited for displaying shading and color areas, On the other hand, Random scan is suitable for engineering and scientific drawings. Only applications for line drawing are prohibited.


Using a raster scan, the entire area is scanned to display the image, whereas a random scan directs the beam along vectors to display the image.

Thanks for reading the article. Still, if you have any questions or queries in your mind about the Difference between Raster Scan and Random Scan then please ask us in the comment section below.

Popular Posts