Display Device Ppt

8/3/2019 Display Device Ppt

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EC-204 Electronics Instruments & Measurements Dr. Utkal Mehta 1

DISPLAY DEVICES

Text Book:

Electronics Instrumentation By H S Kalsi


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EC-204 Electronics Instruments & Measurements Dr. Utkal Mehta 2

Display devices are used for the visual presentation ofinformation.

1. Analog display devices (cathode-ray tubes)

Oscilloscope tubes

TV CRTs

2. Digital display devices LED (including OLED) displays

LCD (liquid crystal) displays

Nixie tube displays and PDPs (plasma display panels)

Electroluminescent displays (ELDs)

3. Others:

Electronic paper

Using principles of nanoelectronics (carbon nanotubes, nanocrystals)

Laser TV


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EC-204 Electronics Instruments & Measurements Dr. Utkal Mehta

w4.siemens.de/.../heft2_97/artikel08/index.html
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Electronic display devices based on various principles were developed.

Active display devices are based on luminescence.

Luminescenceis the general term used to describe the emission ofelectromagnetic radiation from a substance due to a non-thermalprocess. Luminescence occurs from a solid when it is supplied withsome form of energy.

Photoluminescencearises as a result of absorption of photons.

In the case of cathodoluminescencematerial is excited bybombardment with a beam of electrons.

Electroluminescenceis a result of excitation from the application of anelectric field.

Fluorescencepersists for a short lifetime of the transition between the twoenergy levels.

Phosphorescence persists for much longer time (more than 10-8 s).

Passive display devices reflect or modulate light


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Display devices. Content and objectives

Cathode ray tubesElectron gunPrinciples of focusingDeflection of the beam

CathodoluminescenceOscilloscope tubesPicture tubes

Flat panel displays

LED displaysVacuum fluorescent displaysGas discharge displays and plasma display panelsElectroluminescent displaysLiquid crystal displays

Field emission displays

Objectives: overview structures, principles of operation and general properties

of display devices.


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Cathode-ray tubes

The cathode ray tube (CRT), invented by German physicist Karl FerdinandBraun in 1897, is an evacuated glass envelope containing an electron gun (asource of electrons) and a fluorescent screen, usually with internal or externalmeans to accelerate and deflect the electrons. When electrons strike thefluorescent screen, light is emitted.The electron beam is deflected and modulated in a way which causes it todisplay an image on the screen. The image may represent electricalwaveforms (oscilloscope), pictures (television, computer monitor), echoes of

aircraft detected by radar, etc.

A cathode ray tube (CRT) contains four basic parts:

electron gun,

focusing and accelerating systems,

deflecting systems, and

evacuated glass envelope with a phosphorescent screen that glows

visibly when struck by the electron beam.
http://en.wikipedia.org/wiki/Germanyhttp://en.wikipedia.org/wiki/Physicshttp://en.wikipedia.org/wiki/Karl_Ferdinand_Braunhttp://en.wikipedia.org/wiki/Karl_Ferdinand_Braunhttp://en.wikipedia.org/wiki/Vacuumhttp://en.wikipedia.org/wiki/Electron_gunhttp://en.wikipedia.org/wiki/Fluorescenthttp://en.wikipedia.org/wiki/Deflecthttp://en.wikipedia.org/wiki/Modulatehttp://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/Echohttp://en.wikipedia.org/wiki/Aircrafthttp://en.wikipedia.org/wiki/Radarhttp://en.wikipedia.org/wiki/Radarhttp://en.wikipedia.org/wiki/Aircrafthttp://en.wikipedia.org/wiki/Echohttp://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/Modulatehttp://en.wikipedia.org/wiki/Deflecthttp://en.wikipedia.org/wiki/Fluorescenthttp://en.wikipedia.org/wiki/Electron_gunhttp://en.wikipedia.org/wiki/Vacuumhttp://en.wikipedia.org/wiki/Karl_Ferdinand_Braunhttp://en.wikipedia.org/wiki/Karl_Ferdinand_Braunhttp://en.wikipedia.org/wiki/Physicshttp://en.wikipedia.org/wiki/Germany


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Cathode-ray tubes. Electron gun

An electron gun consists of a series of electrodesproducing a narrow beam of high-velocity electrons.

Electrons are released from the indirectly heated

cathode.The intensity of the beam is controlled by variation ofthe negative potential of the cylindrical control gridsurrounding the cathode. This electrode is called the

modulator.The control grid has a hole in the front to allow passageof the electron beam.

The electrons are accelerated and focused.
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Cathode-ray tubes. Electromagnetic deflection


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Electrostatic focusing and electrostatic deflection

Oscilloscope tubes


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Color picture tubes

The colored image is produced varying the intensity of excitation of the three

different phosphors that produce the three primary colors (red, greenand blue)and reproduce the original colors of the image by an additive color process.

Electron

beam

Mask

Screen

The triangular arrangement of electron guns are used. The phosphors arearranged as triangular sets of coloured dots.

A metal shadow mask is placed directly behind the screen in the plane ofintersection of the electron beams to ensure that each beam hits the correctphosphor. The mask acts as a physical barrier to the beams as they progressfrom one location to the next and minimizes the generation of spurious colours

by excitation of the wrong phosphor.


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FLAT PANEL DISPLAYS

CRTs are relatively fragile and bulky.

Other types of thinner displays were developed. They are often called flatpanel displays.

Most flat-panel displays form digits or characters with combination ofsegments or dots. The arrangement of these elements is called the displayfont.

The most common format for numeric display is the seven-segment font.

Graphic displays are like very large dot matrices. Each dot in a graphicdisplay is called picture element, pixelor pel. The capabilities of a graphicdisplay depend on number of pixels horizontally and vertically.
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LED: Germanium Silicon Semiconductor

Gallium Arsenide RedGallum Arsenide Phosphide- Red or yellow

Gallium Phospide- Red or green(Most of the emiited photons have their

wavelengths in the visible region- Output is

light with different colours!)


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Flat panel displays requiring continuous refresh:

DLP (Digital Light Processing)

Plasma displaysLiquid crystal displays (LCDs)Organic light-emitting diode displays (OLEDs)Light-emitting diode display (LED)Electroluminescent displays (ELDs)Surface-conduction electron-emitter displays (SEDs)Field emission displays (FEDs)Nano-emissive display (NEDs)

Only the first five of these displays arecommercially available today, though OLEDdisplays are beginning deployment only in smallsizes (mainly in cellular telephones).

http://en.wikipedia.org/wiki/Flat_panel_display

Flat panel displays
http://en.wikipedia.org/wiki/DLPhttp://en.wikipedia.org/wiki/Plasma_displayhttp://en.wikipedia.org/wiki/AMLCDhttp://en.wikipedia.org/wiki/Organic_light-emitting_diodehttp://en.wikipedia.org/wiki/Light-emitting_diode_displayhttp://en.wikipedia.org/wiki/Electroluminescent_displayhttp://en.wikipedia.org/wiki/Surface-conduction_electron-emitter_displayshttp://en.wikipedia.org/wiki/Field_emission_displayhttp://en.wikipedia.org/wiki/Nano-emissive_displayhttp://en.wikipedia.org/wiki/Nano-emissive_displayhttp://en.wikipedia.org/wiki/Field_emission_displayhttp://en.wikipedia.org/wiki/Surface-conduction_electron-emitter_displayshttp://en.wikipedia.org/wiki/Electroluminescent_displayhttp://en.wikipedia.org/wiki/Light-emitting_diode_displayhttp://en.wikipedia.org/wiki/Organic_light-emitting_diodehttp://en.wikipedia.org/wiki/AMLCDhttp://en.wikipedia.org/wiki/Plasma_displayhttp://en.wikipedia.org/wiki/DLP


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LED displays

Light emitting diodes are used in LED displays.

Operation of the LED displays is based on the injection luminescence.

LED displays are available in many different sizes and shapes.

Usually LED displays radiate red, orange, yellow or green light.

They have a wide operating temperature range, are inexpensive, easilyinterfaced to digital logic, easily multiplexed, do not require high voltagesand have fast response time.

The viewing angle is good and display of arbitrary numbers of digits iseasily assembled.


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http://www.lcdinterfacing.info/7seg2.bmphttp://www.lcdinterfacing.info/7segpin.jpghttp://www.lcdinterfacing.info/7seg1.bmp

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