explanation of CRT, Random & raster scan displays

1. By
Ms. N.Ruba
Asst. Prof / Computer Applications

2. •THE VIDEO DISPLAY DEVICES IS AN OUTPUT DEVICES USED TO REPRESENT THE INFORMATION IN THE
FORM OF IMAGE.
•DISPLAY SYSTEMS ARE MOSTLY CALLED A VIDEO MONITORINGOR VIDEODISPLAY UNIT ( VDU).

4. CATHODERAYTUBE (CRT).
•COLORCRT MONITOR.
•LIQUIDCRYSTAL DISPLAY( LCD).
•LIGHTEMITTINGDIODE( LED).
•DIRECTVIEWSTORAGETUBES ( DOST).
•PLASMADISPLAY.
•3 D DISPLAY.

6. 1. CRT STANDS FOR CATHODERAY TUBE.
2. IT IS A TECHNOLOGYWHICH IS USED TO TRADITIONAL COMPUTERMONITOR
AND TELEVISION.
3. CATHODE RAY TUBE IS A PARTICULARTYPE AN ELECTRON OF VACCUM TUBE
DISPLAYIMAGE WHEN AN ELECTRONBEAM CALLED AN THE RADIANT
SURFACE.

7. •RASTER SCAN DISPLAY ARE MOST COMMON TYPE OF GRAPHICS
MONITOR WHICH EMPLOYS CRT.
•ITS BASED ON TELEVISION TECHNOLOGY.
•A MEMORY AREA CALLED REFRESH BUFFER AND FRAME BUFFER
STORES PICTURE DEFINITION.
•THIS MEMORY AREA HOLDS INTENSITY VALUES FOR ALL SCREEN
POINTS.
•EACH SCREEN POINTS REFERRED TO AS PIXELS.

9. •AN IMPORTANT FUNCTION OF DISPLAY PROCESS IS TO DIGITIZE A
PICTURE DEFINITION GIVEN IN AN APPLICATION PROGRAM INTO SET
OF PIXEL INTENSITY VALUES FOR STORAGE IN REFRESH BUFFER.
•THIS PROCESS REFERRED TO AS SCAN CONVERSION.
•THE PURPOSE OF DISPLAY PROCESSOR IS TO RELIEVE THE CPU FROM
GRAPHIC JOB.
•TYPICALLY PROFESSORS ARE UTILIZED TO INTERFACE INPUT DEVICES.

11.  ADVANTAGES :
 REAL LIFE IMAGES WITH DIFFERENT SHADES CAN BE DISPLAYED.
 COLOR RANGE CAN BE AVAILABLE IS BIGGER THAN RANDOM SCAN DISPLAY.
DISADVANTAGES :
RESOLUTION IS LOWER THAN RANDOM SCAN DISPLAY.
MORE THEN MEMORY IS REQUIRED.
 DATA ABOUT THE INTENSITIES OF ALL PIXEL TO BE STORED.

12. •RANDOM SCAN DISPLAY ELECTRON BEAM IS DIRECTED ONLY TO THE AREAS
OF SCREEN WHERE A PICTURE HAS TO BE DRAWN.
•IR IS ALSO CALLED VECTOR DISPLAY, AS IT DRAWS PICTURE ONE LINE AT
TIME.
•IT CAN DRAW AND REFRESH COMPONENT LINES OF A PICTURE IN ANY
SPECIFIED SEQUENCE.
•PEN PLOTTER IS AN EXAMPLE OF RANDOM SCAN DISPLAY.
•THE NUMBER OF LINES REGULATES REFRESH RATE AN RANDOM SCAN
DISPLAY.

14. •INPUT IN THE FORM OF AN APPLICATION PROGRAM IS STORED IN THE SYSTEM MEMORY
ALONG WITH GRAPHIC PACKAGE.
•GRAPHIC PACKAGE TRANSLATES THE GRAPHIC COMMAND IN APPLICATION PROGRAM INTO A
DISPLAY FILES STORED IN SYSTEM MEMORY.
•THE DISPLAY FILES IS THEN ACCESSED BY THE DISPLAY PROCESSOR TO REFRESH THE SCREEN.
•THE DISPLAY PROCESSOR CYCLE THROUGH EACH COMMAND IN THE DISPLAY FILES PROGRAM.
•SOMETIMES DISPLAY PROCESSOR IN A RANDOM SCAN IS REFERRED TO AS DISPLAY
PROCESSING UNIT/ GRAPHICS CONTROLLER.

16. HIGHER RESOLUTION IS COMPARED TO RASTER SCAN DISPLAY.
PRODUCES SMOOTH LINE DRAWING.
•
•
• LESS MEMORY REQUIRED.
ADVANTAGES:
REALISTIC IMAGES WITH DIFFERENT SHADES CANNOT BE DRAWN.
•
• COLOR LIMITATIONS.
DISADVANTAGES: