Before getting into what is Raster scan system and what is Random scan system, and its differences, it would be very useful when we first go through Random and Raster scan displays.
i).Random Scan Display (or) Vector Scan Display
ii).Raster Scan Display
i).Random Scan Display:
A).In this display, the name itself says that “Random”. In this kind of display the beam is actually moves between the endpoints of the graphic primitives.
B).Random Scan Display mainly draws continuous and ultimately it becomes smooth lines. This kind of display only draws “Characters and Lines”.There is no need of Scan Conversion hardware to this kind of random scan display.
ii).Raster Scan Display:
A).Generally in this kind of Display, the beam moves all over the screen and does one scan line at a time. So it actually moves from top to bottom, it may also moves from back to top. So this kind of display moves around and over the entire screen
B).Raster Scan Display can be able to display areas. Not only drawing areas, it also displays these areas filled with the Solid colors or even patterns too. These Random scan displays not only smooth lines, also shows boundaries of curve shaped primitives, polygons and more. These various primitives can be shown by approximating them with the pixels on the raster grid. For this raster scan display, Scan conversion hardware is compulsorily needed. Because each and every graphic primitive need to be scan converted. And so this display requires Scan conversion hardware.
Difference between Random Scan System & Raster Scan System:
|S.No||Random Scan System||Raster Scan System|
|1.||A System which follows Random or Vector Scan displays is called Random Scan System||A System which follows Raster Scan Displays is called Raster Scan System|
|2.||We must have to consider Mathematical formulae, functions to draw image||Pixels or Points on the screen can be used to draw any kind of image|
|3.||In Random Scan system, the name itself saying that Random. So it draws image using electron beam directly only to the parts of screen where the image is to be drawn||In this Raster Scan system, the electron beam swept across and over the screen. It draws only one row at a time. That too it follows from top to bottom|
|4.||As we know, this Random scan system directly send electron beam to the points directly which follows the line path. So Obviously this system produces smooth line drawings, and so resolution is good||Basically this Raster Scan system cannot produce Zigzag lines. It only follows line by line method. And so we can say that Resolution is somewhat poor compared to Random Scan System|
|5.||In Random Scan System, the picture definition is stored like a group of lines (As random drawing taking place in vector scan system).||In Raster Scan System, the picture definition is stored as group of points or set of points. Also known as Pixels (small dots) in buffer area|