CRT (Refresh Cathode Ray Tube) & Video Display Devices


CRT (Cathode Ray Tube) is one of the Video Display devices. Cathode Ray Tube CRT working is given in detail below. Along with the working of Refresh Cathode Ray Tube, you may also study various Video Display Device. You may find out how those Video Display devices work and other more details below.


Video Display Devices:

Basically Display Devices are the Devices or else known as output devices for showing the information in visual form. So Video Display Devices are nothing but Display or output devices which present Videos in various forms. Most of the display devices are based on the standard CRT design. There are several Video Display Devices in Computer Graphics. Important Video display Devices are provided below. They are,

i).Cathode Ray Tube (CRT):

We often use Computer Monitors and Televisions in our regular life. So CRT technology is employed in these output devices. These CRT Displays are used mostly by Graphic professionals. Because CRT Technology offers good vibrant and very good accurate colour.

ii).Monitor or Display:

Monitor is also referred as Visual Display Unit. Monitor is an electronic output device where we can see entire output through this device.

iii).Random Scan Display:

Random Scan Display is formed by using various geometrical primitives. So they are formed using Curves, Points, Lines, and Polygons

iv).Raster Scan Display:

In the name Raster Scan Display, the Raster word means a rectangular array of points. or else array of dots. So Group of dots are known as Pixels, and image is sub grouped in to a sequence of stips.These are called Scan lines, and these scan lines are further divided in to Pixels.

v).Flat Panel Display:

This kind of Flat Panel Display surrounds number of various electronics visual display techniques or methods. So that it obviously become lighter and very thinner about 100mm.These kind of Flat Panel Displays are used in many portable devices. They are,

Ex: Digital Cameras, Phone, Laptops, Compact Cameras and Camcorders like wise

Refresh Cathode Ray Tube: (Refresh CRT)

C.R.T – Cathode Ray Tube

1).A beam of Cathode rays discharged by an Electron gun moves through some deflection systems.

2).So these deflection systems which direct the beam towards a described specified position on the Screen.

3).This Screen is Phosphor coated, and this Phosphor discharges a mark of light at each position where it is contacted by the Electron beam

4).To maintain the screen picture we need some process, as the light discharged by the phosphor fades with very high speed.

5).That method we require is “To keep up the phosphor glowing is to draw up again (redraw) the picture repeatedly by quickly directing this electron beam back on to the same points which were resulted in first time path. This kind of Display is called “Refresh CRT”

Cathode Ray Tube


Electron Gun Components:

i).Heated Metal Cathode

ii).Control Grid

1).Cathode gets heated by directing “Current” using wire coil, which is also called Filament

2).So obviously this causes electrons to be boiled off the very hot cathode surface. In the Cathode ray tube vaccum, already negative charged electrons are then accelerated towards the Coating by positive voltage

3).Accelerating voltage will be generated with a positively charged metal which is coated on the inside o the CRT envelope near the Phosphor screen

4).On the Phosphor screen, various marks or spots of light are produced on the screen by the transfer of CRT beam energy to screen

Refresh CRT

5).So soon after electrons in the beam collide with the phosphor coating, they are stopped. Now kinetic energy (K.E) is absorbed by the Phosphor. And some part of the beam energy is converted to heat energy because of Friction takes place. And the remaining energy causes electrons in the phosphor atoms to move up to the various higher of its quantum energy levels.

6).After some time, the excited phosphor electrons come back to their previous stable ground state.

7).Make note of this, the Frequency of the light emitted by the Phosphor is directly proportional to the energy difference between “excited quantum state” and “the Ground previous state”


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