DISPLAY DEVICES

DEFINITION

• A display device is a device for

visual presentation of images

(including text) acquired, stored, or

transmitted in various forms.

Ex : Computer monitor,TV screen.

• Also known as an information

display

Classification Of Displays

• CRT Cathode Ray Tube
• LED Light Emitting Diode
• LCD Liquid Crystal Display
• Gas discharge PLASMA displays
• Electro- luminescent (EL) display
• Incandescent display
• EPID Electrophoretic image display
• LVD Liquid vapour display

On Methods Of Conversion Of Electrical

Data Into Visible Light

Active Displays
Light emitters: incandescent is the release of

electromagnetic radiation from a hot body due to its
high temperature

Luminescence: it is any emission of electromagnetic

radiation due to non thermal means

Gas discharge: glow of light around the cathode.

e.g. LEDs, CRTs, gas discharge plasma.

Passive displays
E.g. – LCD, EPIDs

On the application

• Analog : bar graph displays (CRT)

• Digital :alphanumeric, LEDs

Display size & physical

dimension

• Symbolic: alphanumeric, LEDs

• Console (interactive) : CRTs, LEDs

• Large screen : enlarged projection

system

Display format

• Direct view

• Non planar type

In terms of resolution & legibility of

characters

• Simple single element indicator

• Multi-element Display

• Cathode ray tube (CRT) displays

create images by impinging an
electron beam on the face of an
evacuated glass tube that has been
coated with phosphors that emit light
at the primary colors. Cathode-ray
tube (CRT) displays had been the
predominant display technology for
purposes such as home television
screens and computer monitors.

• A light emitting diode (LED) is a

semiconductor light emitting device,
which emits various colors of light,
with light sources being constituted
by compound semiconductors made
of various materials. Light-emitting
diodes have long life expectancy,
high tolerance to humidity, low
power consumption and minimal
heat generation

• Liquid crystal display (LCD) has many

advantages over other conventional
types of displays including high
display quality, small volume
occupation, lightweight, low voltage
driven and low power consumption. A
liquid crystal display device uses the
optical anisotropy and polarization
properties of liquid crystal molecules
to produce an image.

• A plasma display panel (PDP) is a

display device in which ultraviolet
rays generated by the discharge of
gas excites phosphors to realize
predetermined images. In a plasma
display panel, ultraviolet rays are
generated by discharging gas and
exciting phosphor to emit light for a
color display.

• Electroluminescent displays work by

making use of electroluminescence
phenomenon in which light is
generated when an electric field of
certain intensity is applied to a
fluorescent substance.

• A vacuum fluorescent display (VFD)

is an electron tube which displays a
desired pattern by causing electrons
emitted from the cathode in the
vacuum vessel (envelope) which is
transparent to impinge on the
phosphor applied to the anode and
causing the phosphor to emit light.
Vacuum fluorescent displays require
a filament power supply to heat the
filament to a temperature suitable
for proper emission of electrons
which are accelerated by an anode
potential onto a fluorescent material
to emit light.