Graphics Hardware Output Display Devices Input Devices Video

Graphics Hardware • Output Display Devices • Input Devices.

Video Display Devices

Objectives • • • Determine the basic operation of video monitors. Identify the components of CRT. Explain the working of a CRT with the help of a diagram.

A. Raster Scan Display o Interlaced o Non interlaced B: Random Access (Calligraphic)

Cathode Ray Tube

Color Display

Components 1. Electron Gun 2. Focussing System 3. Magnetic Deflection Coils 4. Phosphor Coated Screen 5. Electron Beam 6. Connector Pins 7. Base

The cathode ray tube (CRT) is an evacuated glass envelope containing an electron gun (a source of electrons) and a fluorescent screen, usually with internal or external means to accelerate and deflect the electrons. When electrons strike the fluorescent screen, light is emitted. Resolution of CRT The maximum number of points that can be displayed without overlap on a CRT The number of points per cm that can be plotted horizontally.

Aspect Ratio The ratio of vertical points to horizontal points necessary to produce equal length lines in both direction on the screen. Aspect Ratio ¾ means a vertical line plotted with 3 points has the same length as a horizontal line plotted with 4 points Persistence is defined as the time it takes the emitted light from the screen to decay to one tenth of its original intensity. Lower persistence phosphor require high refresh rate.

• Color CRT Monitors. • Direct View Storage tube. • Flat panel Displays