Raster Scan Display

1. Raster Scan Display

Raster scan display is the most commonly used display method in computer graphics. The image is stored as pixels in a frame buffer.

• Line-by-line scanning
• Uses frame buffer
• Pixel-based display

2. Working Principle

The electron beam starts from the top-left corner and moves horizontally across the screen. After completing one line, it moves to the next line.

Top of Screen
--------------------> Horizontal Scan
| Next Line
| Next Line
v
Bottom of Screen

3. Frame Buffer

A frame buffer is a memory area that stores color or intensity values for each pixel on the screen.

• Stores pixel information
• Controls brightness and color
• Refreshes display continuously

4. Refresh Rate

Refresh rate refers to the number of times the screen is redrawn per second. It is measured in Hertz (Hz).

• Typical values: 60Hz – 75Hz
• Higher rate reduces flicker

5. Raster Scan vs Random Scan

Raster Scan                     Random Scan
----------------------------   ----------------------------
Pixel based                     Vector based
Uses frame buffer               No frame buffer
High memory requirement         Low memory usage
Used in TVs & monitors          Used in oscilloscopes

6. Advantages of Raster Scan

• Supports complex images
• Suitable for color display
• Low cost hardware

7. Disadvantages of Raster Scan

• Requires large memory
• Lower resolution compared to vector
• Aliasing effects

8. Applications of Raster Scan

• Computer monitors
• Television displays
• Mobile and laptop screens

Practice Questions

1. What is raster scan display?
2. Explain working of raster scan.
3. What is a frame buffer?
4. Define refresh rate.
5. Differentiate raster scan and random scan.

Practice Task