Graphics Systems SUBJECT: COMPUTER GRAPHICS LECTURE NO: 04 BATCH: 16BS(INFORMATION TECHNOLOGY) 1/4/2019 1

Video Display Devices  Cathode-Ray Tube Monitor  Raster-Scan Displays  Random-Scan Displays  Color CRT Monitors  Direct-View Storage Tubes  Flat-Panel Displays  Three-Dimensional Viewing Devices 1/4/2019 2

Direct View Storage Tube  DVST gives alternative method for maintaining screen image as in raster scan.  DVST uses storage grid which store the picture information as a charge distribution just behind the phosphor coated screen.  DVST consists two electron guns.  Primary gun emits high speed electrons which strike on the storage grid to draw the picture pattern.  As electron beam strikes on the storage grid with high speed, it knocks out the electrons from the storage grid keeping the net positive charge.

Direct View Storage Tube  The knocked out electrons are attracted towards the Collector.  The net positive charge on the picture is nothing but the picture pattern.  The continuous low speed electrons from fluid gun pass though the control grid and are attracted to the positive charged area of storage grid.  The low speed electrons then penetrate the storage grid and strike the phosphor coating without affecting the positive charged picture pattern on storage grid.  In this process the Collector just behind storage grid smooth out the flow of fluid electrons.

Direct View Storage Tube AdvantagesDisadvantages  Not available in color.  Erasing selective part of screen is not possible.  It produces unpleasant flash on the screen.  Flat Screen  Very high resolution complex picture can be displayed without flickering.  Refreshing is not required as in CRTs

Flat Panel Display  A flat panel display refers to class of video devices that have reduced volume, weight & power requirement compared to CRT.  A flat panel display is thinner than CRTs, we can hang them on walls and can wear on the wrists.  It is categorized in to:  Emissive Display  Non-Emissive Display

Emissive Display  These are the devices that convert electrical energy into light to produce display.  Examples:  Plasma Panel, thin film electroluminescent, and Light emitting diodes.

Non-Emissive Display  These are the devices that optical effects to convert sunlight or light from some other resources into graphics pattern to produce display.  Examples:  Liquid Crystal Displays.

Three Dimensional Viewing Devices  VR Box