cathode ray tube presentation

8/13/2019 cathode ray tube presentation

1/16

PRESENTED BY PRESENTED TO:

JAGMAL RAI MR. VIKAS SIR

13BEL80

CATHODE RAY TUBE


2/16

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.

11/23/2013 Dept. Of Computer Science


3/16

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).



4/16

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.

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_tube


5/16

Basic Cathode Ray TubeThe CRT uses an evacuated glass envelope which is

large, deep, heavy, and relatively fr agile.



6/16

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.

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_tube


7/16

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.



8/16

TYPES OF CRT

The following are the different types of cathode

ray tube:

OSCILLOSCOPE CRTS

COLOUR CRTS

NIMO CRTS



9/16

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.

http://en.wikipedia.org/wiki/Shadow_maskhttp://en.wikipedia.org/wiki/Shadow_maskhttp://en.wikipedia.org/wiki/Shadow_mask


10/16

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



11/16

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



12/16

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



13/16

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.



14/16

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



15/16

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.



16/16


Documents

cathode ray tube presentation