The display device is an output device used to represent the information in the form of images (visual form). Display systems are mostly called a video monitor or Video display unit (VDU).
Display devices are designed to model, display, view, or display information. The purpose of display technology is to simplify information sharing.
Today, the demand for high-quality displays is increasing.
There are some display devices given below:
- Cathode-Ray Tube(CRT)
- Color CRT Monitor
- Liquid crystal display(LCD)
- Light Emitting Diode(LED)
- Direct View Storage Tubes(DVST)
- Plasma Display
- 3D Display
- Cathode-ray Tube (CRT): Here, CRT stands for Cathode ray tube. It is a technology which is used in traditional computer monitor and television.
Cathode ray tube is a particular type of vacuum tube that displays images when an electron beam collides on the radiant surface.
Component of CRT
- Electron Gun: The electron gun is made up of several elements, mainly a heating filament (heater) and a cathode. The electron gun is a source of electrons focused on a narrow beam facing the CRT.
- Focusing & Accelerating Anodes: These anodes are used to produce a narrow and sharply focused beam of electrons.
- Horizontal & Vertical Deflection Plates: These plates are used to guide the path of the electron the beam. The plates produce an electromagnetic field that bends the electron beam through the area as it travels.
- Phosphorus-coated Screen: The phosphorus coated screen is used to produce bright spots when the high-velocity electron beam hits it.
There are two ways to represent an object on the screen:
- Raster Scan: It is a scanning technique in which the electron beam moves along the screen. It moves from top to bottom, covering one line at a time.
A raster scan is based on pixel intensity control display as a rectangular box on the screen called a raster.
Picture description is stored in the memory area called as Refresh buffer, or Frame Buffer.
Frame buffer is also known as Raster or Bitmap. Raster scan provides the refresh rate of 60 to 80 frames per second.
For Example: Television
The beam refreshing has two types:
- Horizontal Retracing
- Vertical Retracing