Display devices are also known as output devices.

Most commonly used output device in a graphics system is a video monitor.

It is an evacuated glass tube.

An electron gun at the rear of the tube produces a beam of electrons which is directed towards the screen of the tube by a high voltage typically 15000 to 20000 volts. Inner side screen is coated with phosphor substance which gives light when it is stroked bye electrons. Control grid controls velocity of electrons before they hit the phosphor. The control grid voltage determines how many electrons are actually in the electron beam. The negative the control voltage is the fewer the electrons that pass through the grid. Thus control grid controls intensity of the spot where beam strikes the screen. The focusing system concentrates the electron beam so it converges to small point when hits the phosphor coating. Deflection system directs beam which decides the point where beam strikes the screen. Deflection system of the CRT consists of two pairs of parallel plates which are vertical and horizontal deflection plates. Voltage applied to vertical and horizontal deflection plates is control vertical and horizontal deflection respectively.

There are two techniques used for producing images on the CRT screen:

• Vector scan/Random scan display.
• Raster scan display

Raster vs Vector

There are two main type of image files: Raster and Vector. Raster images are created with pixel-based programs or captured with a camera or scanner. They are more common in general such as jpg, gif, png, and are widely used on the web. Vector graphics are created with vector software and are common for images that will be applied onto a physical product. Also used in CAD, engineering, and 3D graphics which we do not provide information nor services for.

Raster images are made of pixels. A pixel is a single point or the smallest single element in a display device. If you zoom in to a raster image you may start to see a lot of little tiny squares.

Vector images are mathematical calculations from one point to another that form lines and shapes. If you zoom into a vector graphic it will always look the same.

A raster image has a specific number of pixels. When you enlarge the image file without changing the number of pixels, the image will look blurry. When you enlarge the file by adding more pixels, the pixels are added randomly throughout the image, rarely producing good results.

When you enlarge a vector graphic, the math formulas stay the same, rendering the same visual graphic no matter the size. Vector graphics can be scaled to any size without losing quality