March 1, 2009Dr. Muhammed Al-Mulhem1 ICS 415 Computer Graphics General Graphics Systems Dr. Muhammed...

March 1, 2009 Dr. Muhammed Al-Mulhem 1

ICS 415Computer Graphics

General Graphics Systems

Dr. Muhammed Al-MulhemDr. Muhammed Al-Mulhem

March 1, 2009March 1, 2009

Dr. Muhammed Al-MulhemDr. Muhammed Al-Mulhem

March 1, 2009March 1, 2009


Display technologies

Cathode Ray Tubes (CRTs)Cathode Ray Tubes (CRTs)

• Most common display device today.Most common display device today.

• Evacuated glass bottle.Evacuated glass bottle.

• Extremely high voltage.Extremely high voltage.

• ComponentsComponents

– Electron gun.Electron gun.

– Focusing & deflection systems.Focusing & deflection systems.

– Phosphor coated screen.Phosphor coated screen.

Cathode Ray Tubes (CRTs)Cathode Ray Tubes (CRTs)

• Most common display device today.Most common display device today.

• Evacuated glass bottle.Evacuated glass bottle.

• Extremely high voltage.Extremely high voltage.

• ComponentsComponents

– Electron gun.Electron gun.

– Focusing & deflection systems.Focusing & deflection systems.

– Phosphor coated screen.Phosphor coated screen.


Electron gun

• Contains a filament that, when heated, emits a stream Contains a filament that, when heated, emits a stream of electrons.of electrons.

• Electrons are focused with an electromagnet into a Electrons are focused with an electromagnet into a sharp beam and directed to a specific point of the face sharp beam and directed to a specific point of the face of the picture tube.of the picture tube.

• The picture tube is coated with small phosphor dots.The picture tube is coated with small phosphor dots.

• When the beam hits a phosphor dot it glows with a When the beam hits a phosphor dot it glows with a brightness proportional to the strength of the beam and brightness proportional to the strength of the beam and how long it is hit.how long it is hit.

• Contains a filament that, when heated, emits a stream Contains a filament that, when heated, emits a stream of electrons.of electrons.

• Electrons are focused with an electromagnet into a Electrons are focused with an electromagnet into a sharp beam and directed to a specific point of the face sharp beam and directed to a specific point of the face of the picture tube.of the picture tube.

• The picture tube is coated with small phosphor dots.The picture tube is coated with small phosphor dots.

• When the beam hits a phosphor dot it glows with a When the beam hits a phosphor dot it glows with a brightness proportional to the strength of the beam and brightness proportional to the strength of the beam and how long it is hit.how long it is hit.


CRT characteristics

How might one measure CRT capabilities?How might one measure CRT capabilities?

• Size of tubeSize of tube

• Brightness of phosphorsBrightness of phosphors

• Speed of electron gunSpeed of electron gun

• Width of electron beam Width of electron beam

• PixelsPixels

How might one measure CRT capabilities?How might one measure CRT capabilities?

• Size of tubeSize of tube

• Brightness of phosphorsBrightness of phosphors

• Speed of electron gunSpeed of electron gun

• Width of electron beam Width of electron beam

• PixelsPixels


Display technologies: CRTs

Vector Displays - Vector Displays - BattlezoneBattlezone? ? TempestTempest? ?



Vector DisplaysVector Displays

• Early computer displays: basically an oscilloscopeEarly computer displays: basically an oscilloscope

• Control X,Y with vertical/horizontal plate voltage Control X,Y with vertical/horizontal plate voltage

• Often used intensity as Z (close things were brighter)Often used intensity as Z (close things were brighter)

• DisadvantagesDisadvantages

– Just does wireframeJust does wireframe

– Complex scenes cause visible flickerComplex scenes cause visible flicker

Vector DisplaysVector Displays

• Early computer displays: basically an oscilloscopeEarly computer displays: basically an oscilloscope

• Control X,Y with vertical/horizontal plate voltage Control X,Y with vertical/horizontal plate voltage

• Often used intensity as Z (close things were brighter)Often used intensity as Z (close things were brighter)

• DisadvantagesDisadvantages

– Just does wireframeJust does wireframe

– Complex scenes cause visible flickerComplex scenes cause visible flicker



Raster DisplaysRaster Displays

• The most common CRTThe most common CRT

• The electron beam is swept across the screen, one The electron beam is swept across the screen, one row at a time.row at a time.


• The most common CRTThe most common CRT

• The electron beam is swept across the screen, one The electron beam is swept across the screen, one row at a time.row at a time.




• Black and white television: an oscilloscope with a fixed scan Black and white television: an oscilloscope with a fixed scan pattern: left to right, top to bottompattern: left to right, top to bottom

– As beam sweeps across entire face of CRT, beam intensity As beam sweeps across entire face of CRT, beam intensity changes to reflect brightnesschanges to reflect brightness

• Analog signal vs. digital displayAnalog signal vs. digital display


• Black and white television: an oscilloscope with a fixed scan Black and white television: an oscilloscope with a fixed scan pattern: left to right, top to bottompattern: left to right, top to bottom

– As beam sweeps across entire face of CRT, beam intensity As beam sweeps across entire face of CRT, beam intensity changes to reflect brightnesschanges to reflect brightness

• Analog signal vs. digital displayAnalog signal vs. digital display


Display technologies: CRT

Can a computer display work like a black and Can a computer display work like a black and white TV?white TV?

• Solution: We need a special memory to buffer image. We call Solution: We need a special memory to buffer image. We call this the this the framebufferframebuffer..

• Digital description to analog signal to digital display.Digital description to analog signal to digital display.

Can a computer display work like a black and Can a computer display work like a black and white TV?white TV?

• Solution: We need a special memory to buffer image. We call Solution: We need a special memory to buffer image. We call this the this the framebufferframebuffer..

• Digital description to analog signal to digital display.Digital description to analog signal to digital display.


Display Technologies: CRTs

RefreshRefresh

• Frame must be “refreshed” to draw new imagesFrame must be “refreshed” to draw new images

• As new pixels are struck by electron beam, others are decayingAs new pixels are struck by electron beam, others are decaying

• Electron beam must hit all pixels frequently to eliminate flickerElectron beam must hit all pixels frequently to eliminate flicker

• Critical fusion frequencyCritical fusion frequency

– Typically 60 times/secTypically 60 times/sec

– Varies with intensity, individuals, phosphor persistence, Varies with intensity, individuals, phosphor persistence, lighting...lighting...

RefreshRefresh

• Frame must be “refreshed” to draw new imagesFrame must be “refreshed” to draw new images

• As new pixels are struck by electron beam, others are decayingAs new pixels are struck by electron beam, others are decaying

• Electron beam must hit all pixels frequently to eliminate flickerElectron beam must hit all pixels frequently to eliminate flicker

• Critical fusion frequencyCritical fusion frequency

– Typically 60 times/secTypically 60 times/sec

– Varies with intensity, individuals, phosphor persistence, Varies with intensity, individuals, phosphor persistence, lighting...lighting...


Display Technologies: CRTs

Interlaced ScanningInterlaced Scanning• Assume we can only scan all pixels of entire screen Assume we can only scan all pixels of entire screen

30 times / second30 times / second

• To reduce flicker, divide frame into two “fields” of odd To reduce flicker, divide frame into two “fields” of odd and even linesand even lines

Interlaced ScanningInterlaced Scanning• Assume we can only scan all pixels of entire screen Assume we can only scan all pixels of entire screen

30 times / second30 times / second

• To reduce flicker, divide frame into two “fields” of odd To reduce flicker, divide frame into two “fields” of odd and even linesand even lines


Display Technology: Color CRTs

Color CRTs are Color CRTs are muchmuch more complicated more complicated

• Requires manufacturing very precise geometryRequires manufacturing very precise geometry

• Uses a pattern of color phosphors on the screen:Uses a pattern of color phosphors on the screen:

Color CRTs are Color CRTs are muchmuch more complicated more complicated

• Requires manufacturing very precise geometryRequires manufacturing very precise geometry

• Uses a pattern of color phosphors on the screen:Uses a pattern of color phosphors on the screen:

Delta electron gun arrangement In-line electron gun arrangement


Display Technology: Color CRTs

Color CRTs haveColor CRTs have

• Three electron gunsThree electron guns

• A metal A metal shadow maskshadow mask to differentiate the beamsto differentiate the beams

Color CRTs haveColor CRTs have

• Three electron gunsThree electron guns

• A metal A metal shadow maskshadow mask to differentiate the beamsto differentiate the beams


Display Technology: Raster

Raster CRT pros:Raster CRT pros:

• Allows solids, not just wireframes.Allows solids, not just wireframes.

• Leverages low-cost CRT technologyLeverages low-cost CRT technology

• Bright! Display Bright! Display emitsemits light light

Cons:Cons:

• Requires screen-size memory arrayRequires screen-size memory array

• Discreet sampling (pixels)Discreet sampling (pixels)

• Practical limit on size (call it 40 inches)Practical limit on size (call it 40 inches)

• BulkyBulky

Raster CRT pros:Raster CRT pros:

• Allows solids, not just wireframes.Allows solids, not just wireframes.

• Leverages low-cost CRT technologyLeverages low-cost CRT technology

• Bright! Display Bright! Display emitsemits light light

Cons:Cons:

• Requires screen-size memory arrayRequires screen-size memory array

• Discreet sampling (pixels)Discreet sampling (pixels)

• Practical limit on size (call it 40 inches)Practical limit on size (call it 40 inches)

• BulkyBulky


CRTs – A Review

• CRT technology hasn’t changed much in 50 yearsCRT technology hasn’t changed much in 50 years

• Early television technologyEarly television technology

– high resolution high resolution

– requires synchronization between video signal and requires synchronization between video signal and electron beam vertical sync pulseelectron beam vertical sync pulse

• Early computer displaysEarly computer displays

– avoided synchronization using ‘vector’ algorithmavoided synchronization using ‘vector’ algorithm

– flicker and refresh were problematicflicker and refresh were problematic

• CRT technology hasn’t changed much in 50 yearsCRT technology hasn’t changed much in 50 years

• Early television technologyEarly television technology

– high resolution high resolution

– requires synchronization between video signal and requires synchronization between video signal and electron beam vertical sync pulseelectron beam vertical sync pulse

• Early computer displaysEarly computer displays

– avoided synchronization using ‘vector’ algorithmavoided synchronization using ‘vector’ algorithm

– flicker and refresh were problematicflicker and refresh were problematic


CRTs – A Review• Raster Displays (early 70s)Raster Displays (early 70s)

– like television, scan all pixels in regular patternlike television, scan all pixels in regular pattern

– use frame buffer (video RAM) to eliminate sync problemsuse frame buffer (video RAM) to eliminate sync problems

• RAMRAM

– ¼ MB (256 KB) cost $2 million in 1971¼ MB (256 KB) cost $2 million in 1971

– Do some math…Do some math…

- 1280 x 1024 screen resolution = 1,310,720 pixels1280 x 1024 screen resolution = 1,310,720 pixels

- Monochrome color (binary) requires 160 KBMonochrome color (binary) requires 160 KB

- High resolution color requires 5.2 MBHigh resolution color requires 5.2 MB

• Raster Displays (early 70s)Raster Displays (early 70s)

– like television, scan all pixels in regular patternlike television, scan all pixels in regular pattern

– use frame buffer (video RAM) to eliminate sync problemsuse frame buffer (video RAM) to eliminate sync problems

• RAMRAM

– ¼ MB (256 KB) cost $2 million in 1971¼ MB (256 KB) cost $2 million in 1971

– Do some math…Do some math…

- 1280 x 1024 screen resolution = 1,310,720 pixels1280 x 1024 screen resolution = 1,310,720 pixels

- Monochrome color (binary) requires 160 KBMonochrome color (binary) requires 160 KB

- High resolution color requires 5.2 MBHigh resolution color requires 5.2 MB


Flat-panel display

• Flat-panel refers to a class of video devices that Flat-panel refers to a class of video devices that have reduced Volume, Weight, and Power have reduced Volume, Weight, and Power requirements compared to a CRT.requirements compared to a CRT.

• A significant feature of flat-panel displays is that A significant feature of flat-panel displays is that they are thinner than CRTs, and we can hang they are thinner than CRTs, and we can hang them on walls or wear them on our wrists. them on walls or wear them on our wrists.

• Flat-panel refers to a class of video devices that Flat-panel refers to a class of video devices that have reduced Volume, Weight, and Power have reduced Volume, Weight, and Power requirements compared to a CRT.requirements compared to a CRT.

• A significant feature of flat-panel displays is that A significant feature of flat-panel displays is that they are thinner than CRTs, and we can hang they are thinner than CRTs, and we can hang them on walls or wear them on our wrists. them on walls or wear them on our wrists.


Display Technology: LCDs

• Liquid-crystal displays (LCDs)Liquid-crystal displays (LCDs)

• Commonly used in small systems, such as Commonly used in small systems, such as laptop computers and calculators.laptop computers and calculators.

• It produces a picture by passing polarized light It produces a picture by passing polarized light from the surrounding or from an internal light from the surrounding or from an internal light source through a liquid-crystal material.source through a liquid-crystal material.

• Liquid-crystal displays (LCDs)Liquid-crystal displays (LCDs)

• Commonly used in small systems, such as Commonly used in small systems, such as laptop computers and calculators.laptop computers and calculators.

• It produces a picture by passing polarized light It produces a picture by passing polarized light from the surrounding or from an internal light from the surrounding or from an internal light source through a liquid-crystal material.source through a liquid-crystal material.


Display Technology: LCDs

• Organic molecules, naturally in crystalline state, Organic molecules, naturally in crystalline state, that liquefy when excited by heat or E fieldthat liquefy when excited by heat or E field

• Crystalline state twists polarized light 90º. Crystalline state twists polarized light 90º.

• Organic molecules, naturally in crystalline state, Organic molecules, naturally in crystalline state, that liquefy when excited by heat or E fieldthat liquefy when excited by heat or E field

• Crystalline state twists polarized light 90º. Crystalline state twists polarized light 90º.


Display Technology: Plasma

Plasma display panelsPlasma display panels

• Also called gas-discharge displays.Also called gas-discharge displays.

• Constructed by filling the region Constructed by filling the region between two glass plates with a between two glass plates with a mixture of gases that usually include mixture of gases that usually include neon.neon.

• Similar in principle to Similar in principle to fluorescent light tubes.fluorescent light tubes.


• Also called gas-discharge displays.Also called gas-discharge displays.

• Constructed by filling the region Constructed by filling the region between two glass plates with a between two glass plates with a mixture of gases that usually include mixture of gases that usually include neon.neon.

• Similar in principle to Similar in principle to fluorescent light tubes.fluorescent light tubes.




• Firing voltages applied to an Firing voltages applied to an intersecting pair of horizontal and intersecting pair of horizontal and vertical conductors cause the gas at vertical conductors cause the gas at the intersection of the two conductors the intersection of the two conductors to break down into a glowing plasma to break down into a glowing plasma of electron and ions.of electron and ions.


• Firing voltages applied to an Firing voltages applied to an intersecting pair of horizontal and intersecting pair of horizontal and vertical conductors cause the gas at vertical conductors cause the gas at the intersection of the two conductors the intersection of the two conductors to break down into a glowing plasma to break down into a glowing plasma of electron and ions.of electron and ions.




• Picture definition is stored in a refresh Picture definition is stored in a refresh buffer.buffer.

• Firing voltages are applied to refresh Firing voltages are applied to refresh the pixel positions, at the intersection the pixel positions, at the intersection of the conductors, 60 times per of the conductors, 60 times per second. second.


• Picture definition is stored in a refresh Picture definition is stored in a refresh buffer.buffer.

• Firing voltages are applied to refresh Firing voltages are applied to refresh the pixel positions, at the intersection the pixel positions, at the intersection of the conductors, 60 times per of the conductors, 60 times per second. second.


Display Technology

Plasma Display Panel ProsPlasma Display Panel Pros• Large viewing angleLarge viewing angle

• Good for large-format displaysGood for large-format displays

• Fairly brightFairly bright

ConsCons• ExpensiveExpensive

• Large pixelsLarge pixels

• Phosphors gradually depletePhosphors gradually deplete

• Less bright than CRTs, using more powerLess bright than CRTs, using more power

Plasma Display Panel ProsPlasma Display Panel Pros• Large viewing angleLarge viewing angle

• Good for large-format displaysGood for large-format displays

• Fairly brightFairly bright

ConsCons• ExpensiveExpensive

• Large pixelsLarge pixels

• Phosphors gradually depletePhosphors gradually deplete

• Less bright than CRTs, using more powerLess bright than CRTs, using more power


Review

Read Chapter 2Read Chapter 2

• Details about display devicesDetails about display devices

Read Chapter 2Read Chapter 2

• Details about display devicesDetails about display devices

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March 1, 2009Dr. Muhammed Al-Mulhem1 ICS 415 Computer Graphics General Graphics Systems Dr. Muhammed...

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