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PRESENTED BY PRESENTED TO:
JAGMAL RAI MR. VIKAS SIR
13BEL80
CATHODE RAY TUBE
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Introduction
A cathode ray tube is a specialized vacuum tube
in which images are produced when an electronbeam strikes a phosphorescent surface.
A cathode ray tube is used to display images by
using Phosphors.
The CRT takes input from an external source and
displays it.
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History
The first CRT was invented by Karl Ferdinand
Braun(German Scientist) in 1897.
It is also known as Braun tube.
In 1907 a Russian scientist Boris Rosing used CRT in the
receiver of a television system.
The first cathode ray tube to use a hot cathode was
developed by John B.Jhonson (who gave his name to the
term Jhonson noise).
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W hat is cathode ray tube The cathode ray tube (CRT) is a vacuum tubecontaining
an electron gun(a source of electrons) and
a fluorescentscreen, with internal or external means to
accelerate and def lect the electron beam, used to create
images in the form of l ight emitted from the fluorescent
screen. The image may represent :
electrical waveforms(oscilloscope)
pictures (television, computer monitor)
radartargets and others.
11/23/2013 Dept. Of Computer Science
http://en.wikipedia.org/wiki/Vacuum_tubehttp://en.wikipedia.org/wiki/Electron_gunhttp://en.wikipedia.org/wiki/Fluorescenthttp://en.wikipedia.org/wiki/Waveformhttp://en.wikipedia.org/wiki/Oscilloscopehttp://en.wikipedia.org/wiki/Televisionhttp://en.wikipedia.org/wiki/Computer_monitorhttp://en.wikipedia.org/wiki/Radarhttp://en.wikipedia.org/wiki/Radarhttp://en.wikipedia.org/wiki/Computer_monitorhttp://en.wikipedia.org/wiki/Televisionhttp://en.wikipedia.org/wiki/Oscilloscopehttp://en.wikipedia.org/wiki/Waveformhttp://en.wikipedia.org/wiki/Fluorescenthttp://en.wikipedia.org/wiki/Electron_gunhttp://en.wikipedia.org/wiki/Vacuum_tube8/13/2019 cathode ray tube presentation
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Basic Cathode Ray TubeThe CRT uses an evacuated glass envelope which is
large, deep, heavy, and relatively fr agile.
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Overview
A cathode ray tube is a vacuum tubewhich consists of one or more
electron guns, possibly internal electrostatic def lection plates, and a
phosphor target. In television setsand computer monitors, the entirefront area of the tube is scanned repeti tively and systematically in a
f ixed pattern called a raster. An image is produced by controll ing
the intensity of each of the three electron beams, one for each
additi ve primary color (red, green, and blue) with a video signalas a
reference. In al l modern CRT moni tors and televisions, the beams
are bent by magnetic def lection, a varying magnetic field generatedby coils and driven by electronic circuits around the neck of the
tube.
11/23/2013 Dept. Of Computer Science
http://en.wikipedia.org/wiki/Vacuum_tubehttp://en.wikipedia.org/wiki/Television_sethttp://en.wikipedia.org/wiki/Computer_monitorhttp://en.wikipedia.org/wiki/Raster_scanhttp://en.wikipedia.org/wiki/Video_signalhttp://en.wikipedia.org/wiki/Video_signalhttp://en.wikipedia.org/wiki/Raster_scanhttp://en.wikipedia.org/wiki/Computer_monitorhttp://en.wikipedia.org/wiki/Television_sethttp://en.wikipedia.org/wiki/Vacuum_tube8/13/2019 cathode ray tube presentation
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How CRTs work display?A CRT moni tor contains mil l ions of tiny red, green, and
blue phosphor dots that glow when struck by an electron
beam that travels across the screen to create a visibleimage. I n a CRT moni tor tube, the cathode is a heatedfi lament. The heated fi lament is in a vacuum createdinside a glass tube. The electrons are negative and thescreen gives a positi ve charge so the screen glows.
11/23/2013 Dept. Of Computer Science
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TYPES OF CRT
The following are the different types of cathode
ray tube:
OSCILLOSCOPE CRTS
COLOUR CRTS
NIMO CRTS
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Color CRTs
Color tubes use three different phosphors which emit red, green,and blue light respectively. Color CRTs have three electron guns, onefor each primary color, arranged either in a straight line or in a
triangular configuration (the guns are usually constructed as asingle unit). A grille or mask absorbs the electrons that wouldotherwise hit the wrong phosphor. A shadow masktube uses ametal plate with tiny holes, placed so that the electron beam onlyilluminates the correct phosphors on the face of the tube.
The three beams in color CRTs would not strike the screen at thesame point without convergence calibration. Instead, the set wouldneed to be manually adjusted to converge the three color beamstogether to maintain color accuracy.
11/23/2013 Dept. Of Computer Science
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Phosphorus
Phosphors and shadow
mask Phosphorsare dots
inside the CRT monitor
that glow red, green, or
blue when an electron
gun sweeps over them
Phosphors are evenly
distributed across the
front of the monitor
One group of red, green,and blue phosphors is calleda triad
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Shadow Mask
Shadow maskis a screen that
enables the proper electron gun
to light the proper phosphor
Electron guns sweep across
the phosphors as a group
The area of phosphors lit at onetime by a group of guns is called
a pictureelement, orpixel
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Dot Pitch
Dot pitchdiagonal distance between
phosphorous dots of the same color
Range from 0.39 mm to as low as 0.18 mm
The lower the dot
pitch, the more dots
across the screen,which produces
a sharper,
more defined image
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Advantages of CRT The cathode rayed tube can easily increase the monitors
brightness by ref lecting the l ight.
They produce more colours
The Cathode Ray Tube moni tors have lower price rate
than the LCD display or Plasma display.
The qual i ty of the image displayed on a Cathode Ray
Tube is superior to the LCD and Plasma moni tors.
The contrast features of the cathode ray tube moni tor
are considered highly excellent.
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Disadvantages of CRT They have a big back and take up space on desk.
The electromagnetic fields emitted by CRT monitors consti tute a
health hazard to the functioning of l iving cell s. CRTs emit a small amount of X-ray band radiation which can resul t
in a health hazard.
CRTs operate at very high voltage which can overheat system or
resul t in an implosion
Within a CRT a strong vacuum exists in i t and can also resul t in a
implosion
They are heavy to pick up and carry around
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Applications
Before LCD or Plasma television, the CRT was used to
create a moving image.
CRT is used in cathode ray oscilloscope that displays
voltage and time period in the form of graphs.
CRT is also being used many displaying devices.
In the earlier computers CRT was used to display images
on Monitors.
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11/23/2013 Dept. Of Computer Science