It basically describes how CRT monitors produces different color on the screen.

1. COLOR PRODUCTION METHOD
Rishav Bhurtel

2. Types Of Display
• CRT or Cathode Ray Tube Monitor
• LCD or Flat Panel Monitor
• LED and OLED
• Plasma Display

3. CRT
• Cathode Ray Tube
• The cathode ray tube (CRT) is a vacuum tube containing one or more electron guns, and a
phosphorescent screen used to view images.
• Cathode rays were discovered by Johann Hittorf in 1869.
• Ferdinand Braun in 1897 invented the earliest version of CRT.
• Russian scientist Boris Rosing in 1907 used a CRT to form a picture.

4. Working Mechanism

5. • Spots of light are produced on the screen by the transfer of the CRT beam energy to the
phosphorous. When the Electrons in the beam collide with the phosphor coating, they are
stopped and their kinetic energy is absorbed by the phosphor. Part of the beam energy is
converted by friction into heat energy and the remainder causes electrons in the phosphor
atoms to move up to higher quantum-energy levels. After a short time the “excited”
phosphor begin dropping back to their stable ground state, giving up their extra energy as
small quantum of light energy. What we see on the screen is the combined effect of all the
electron light emission.
• Persistence
lower persistence higher refresh rate
some have greater than 1 sec and some ranges from 10 to 60 microseconds
• Resolution
number of points per centimetre
Spot Size
A CRT running at 1,280x1,024 at a 75Hz refresh rate illuminates and
re-illuminates nearly 100 million pixels per second.
• Aspect Ratio
An Aspect ratio ¾ means that a vertical line plotted with three points has the same length as
horizontal line plotted with four points.

6. A color CRT monitor displays color picture by using a combination of phosphors that
emit different colored light. By combining the emitted light a range of colors can be
generated. Two basic methods for producing color displays are:
• Beam Penetration Method
• Shadow-Mask Method

7. Beam Penetration Method
• Random scan monitors use the beam penetration method for displaying color picture.
• In this, the inside of CRT screen is coated two layers of phosphor namely red and
green.
• A beam of slow electrons excites only the outer red layer, while a beam of fast
electrons penetrates red layer and excites the inner green layer.
• At intermediate beam speeds, combinations of red and green light are emitted to
show two additional colors- orange and yellow.

8. Shadow Mask Method
• Raster scan system are use shadow mask methods to produce a much more range of
colors than beam penetration method.
• In this, CRT has three phosphor color dots.
• One phosphor dot emits a red light, second emits a green light and third emits a blue
light.

9. COLOR Production

10. • •When three beams pass through a hole in shadow mask they activate dot triangle as
shown in figure below:
• The colors we can see depend on the amount of excitation of red, green and blue
phosphor.
• A white area is a result of all three dots with equal intensity while yellow is produced
with green and red dots, magenta is produced with blue and red and so on.

11. Additive Color Mixing

12. Thank You.