Raster scan displays, like old CRT monitors, refresh the screen line by line, top to bottom. They scan across each line, painting pixels as they go. Random scan displays paint the screen in a random pattern instead of the rigid left-to-right, top-to-bottom fashion of raster scan. If you’ve ever used an older CRT monitor, chances are it used a raster scan. Newer flat-panel displays typically use random scans.The key differences between raster scan and random scan are:
Raster Scan Displays
Raster scan starts at the top left of the screen and moves horizontally, painting each pixel in turn until it reaches the end of the line. Then it quickly moves back to the left, drops down a line, and starts scanning and painting again. This line-by-line, left-to-right process continues until the entire screen has been refreshed.
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Raster scan was necessary for older display technologies but has some downsides. The constant repainting of the entire screen can produce a flickering effect that strains your eyes. It also makes animations and movement seem jerky since the screen is being entirely redrawn so frequently.
On the plus side, the raster scan is simple to implement and supports high resolutions. However, it requires a lot of bandwidth to transmit the data needed to constantly repaint the entire screen. It also can’t easily change the resolution or aspect ratio.
With newer display technologies like LCDs, plasmas and OLEDs, raster scan is no longer required. These screens can stay lit until the image needs to change, allowing for higher refresh rates, smoother movement, and less eye strain. While raster scans dominated for decades, modern displays now favor the flexibility and performance of random scans.
Random Scan Displays
The difference between random scan and raster scan is that the random scan displays have the ability to activate any pixel at any time whereas the latter scan across each line, painting pixels as they go. Pixels illuminate individually rather than line by line. This allows for faster refresh rates and often a sharper, cleaner image. The random activation of pixels also reduces motion blur since the image can change more quickly.
Random scan displays can activate more pixels at once, allowing for increased brightness overall. This is especially noticeable on larger screens. The random scan produces images that can be viewed clearly from more oblique angles. You don’t lose color or contrast as quickly when viewing from the side.
By painting pixels in a random, asynchronous fashion, a random scan reduces the blurring that can occur with fast on-screen motion. This is a big benefit for gaming, action movies, and other high-motion content. The random scan typically offers better pixel density and more precise control over individual pixels. This results in images that appear sharper and contain finer details.
So if visuals are a top priority or you frequently view fast-moving content, a display with random scan and a high refresh rate is the way to go. Your eyes will thank you!
Raster Scan vs Random Scan
In summary, while both raster scan and random scan have their advantages, the key differences in resolution, refresh rate, cost, image quality, and common uses can help determine which technology is the best choice for your needs.
