What is the Use of a Random Scan System
Raster scan and random scan are two popular approaches used to draw pictures on the screen of a monitor. The raster scan display device sweeps the electron beam over the entire screen one line at a time in a downward direction. It stores picture definition as a group of intensity measures for various screen points in a buffer. This buffer is known as the frame buffer.
It is Used for Drawing a Picture in One Line at a Time
Random-scan systems use an electron beam that acts like a pencil to build a line on the panel. This technique is ideally suited for line drawing and requires less memory than raster scan. However, it is less able to render shaded images.
When a cathode ray tube is operated as a random-scan display device, the electron beam is directed only to those parts of the screen where a picture is to be drawn. For this reason, random-scan monitors are also called vector displays or stroke-writing or calligraphic displays. The component lines of a picture can be drawn and refreshed by a random-scan system with 30 to 60 times per second.
Graphics commands are translated by the random-scan program into a display file, which is stored in system memory. Each time the screen is refreshed, the display processor accesses the command program in order to draw a new picture. This process is synchronized with the reading of intensity values held in the refresh frame buffer.
It is Cheaper Than Raster Scan
Raster scan and Random Scan are two different ways of drawing images on the screen. Both methods have their advantages and disadvantages, but Random Scan is cheaper because it uses fewer bits to draw a picture. It also does not use interlacing, which can reduce image quality.
In a raster scan display, the electron beam is swept across the screen one row at a time from top to bottom. As the electron beam sweeps over each row, it toggles between high and low intensity levels to generate a pattern of illuminated spots on the screen. This technique is similar to that used in oscilloscopes. The difference between raster scan and random scan is, in a random scan, only an area of the screen with a picture is displayed whereas in a raster scan, the entire screen is scanned.
The picture definition for a raster display is stored as a combination of intensity values for all screen points in an area of memory known as the frame buffer. The system then draws the individual lines of a picture by tracing over them using a set of line-drawing commands that are stored in the refresh display file.
It is More Efficient Than Raster Scan
In a random scan, the electron beam is directed only to the part of the screen where a picture is to be drawn. The resolution of this method is higher than that of raster scan. It is a good choice for applications that require polygon drawings. It is also suitable for constructing lifelike scenes. Examples of such devices include TV sets and dot matrix printers.
Raster and random scan are the two popular methods used to display images on the screen of a monitor. The main difference between them is that in raster scan, the electron beam is swept across the screen one line at a time from top to bottom. In contrast, in random scan, the electron beam is aimed at only those parts of the screen where pictures are drawn.
Raster scan systems store picture definition as an intensity value in a special area of memory called a frame buffer. These values are then retrieved to refresh the screen image. It is easy to modify a raster image, but it is harder to draw smooth lines in this system.
It is More Accurate Than Raster Scan
Raster scan is a method of displaying an image on a display screen using intensity control. It stores information of on and off pixels in a memory area called refresh buffer or frame buffer. It also has the capability to display different color variants. This type of display can be found in our home television sets and dot matrix printers. It requires a large amount of memory to store the frame buffer and it cannot display zacked lines.
Random scan displays can draw a picture in arbitrary sequence, which is why they are also called vector displays. A random-scan monitor is best suited for line drawing algorithms and can refresh the screen at rates of 60 to 80 times per second.