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

2. Dr. Muhammed Al-Mulhem2 Display technologies 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. –Focusing & deflection systems. –Phosphor coated screen. 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. –Focusing & deflection systems. –Phosphor coated screen.

3. March 1, 2009Dr. Muhammed Al-Mulhem3 Electron gun Contains a filament that, when heated, emits a stream of electrons.Contains a filament that, when heated, emits a stream of electrons. Electrons are focused with an electromagnet into a sharp beam and directed to a specific point of the face of the picture tube.Electrons are focused with an electromagnet into a sharp beam and directed to a specific point of the face 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 brightness proportional to the strength of the beam and how long it is hit.When the beam hits a phosphor dot it glows with a brightness proportional to the strength of the beam and how long it is hit. Contains a filament that, when heated, emits a stream of electrons.Contains a filament that, when heated, emits a stream of electrons. Electrons are focused with an electromagnet into a sharp beam and directed to a specific point of the face of the picture tube.Electrons are focused with an electromagnet into a sharp beam and directed to a specific point of the face 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 brightness proportional to the strength of the beam and how long it is hit.When the beam hits a phosphor dot it glows with a brightness proportional to the strength of the beam and how long it is hit.

4. March 1, 2009Dr. Muhammed Al-Mulhem4 CRT characteristics 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 beamWidth of electron beam PixelsPixels 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 beamWidth of electron beam PixelsPixels

5. March 1, 2009Dr. Muhammed Al-Mulhem5 Display technologies: CRTs Vector Displays - Battlezone? Tempest?

6. March 1, 2009Dr. Muhammed Al-Mulhem6 Display technologies: CRTs Vector Displays Early computer displays: basically an oscilloscopeEarly computer displays: basically an oscilloscope Control X,Y with vertical/horizontal plate voltageControl 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 wireframe –Complex scenes cause visible flicker Vector Displays Early computer displays: basically an oscilloscopeEarly computer displays: basically an oscilloscope Control X,Y with vertical/horizontal plate voltageControl 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 wireframe –Complex scenes cause visible flicker

7. March 1, 2009Dr. Muhammed Al-Mulhem7 Display technologies: CRTs Raster Displays The most common CRTThe most common CRT The electron beam is swept across the screen, one row at a time.The electron beam is swept across the screen, one row at a time. Raster Displays The most common CRTThe most common CRT The electron beam is swept across the screen, one row at a time.The electron beam is swept across the screen, one row at a time.

8. March 1, 2009Dr. Muhammed Al-Mulhem8 Display technologies: CRTs Raster Displays Black and white television: an oscilloscope with a fixed scan pattern: left to right, top to bottomBlack and white television: an oscilloscope with a fixed scan pattern: left to right, top to bottom –As beam sweeps across entire face of CRT, beam intensity changes to reflect brightness Analog signal vs. digital displayAnalog signal vs. digital display Raster Displays Black and white television: an oscilloscope with a fixed scan pattern: left to right, top to bottomBlack and white television: an oscilloscope with a fixed scan pattern: left to right, top to bottom –As beam sweeps across entire face of CRT, beam intensity changes to reflect brightness Analog signal vs. digital displayAnalog signal vs. digital display

9. March 1, 2009Dr. Muhammed Al-Mulhem9 Display technologies: CRT Can a computer display work like a black and white TV? Solution: We need a special memory to buffer image. We call this the framebuffer.Solution: We need a special memory to buffer image. We call this the framebuffer. 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 white TV? Solution: We need a special memory to buffer image. We call this the framebuffer.Solution: We need a special memory to buffer image. We call this the framebuffer. Digital description to analog signal to digital display.Digital description to analog signal to digital display.

10. March 1, 2009Dr. Muhammed Al-Mulhem10 Display Technologies: CRTs Refresh 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/sec –Varies with intensity, individuals, phosphor persistence, lighting... Refresh 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/sec –Varies with intensity, individuals, phosphor persistence, lighting...

11. March 1, 2009Dr. Muhammed Al-Mulhem11 Display Technologies: CRTs Interlaced Scanning Assume we can only scan all pixels of entire screen 30 times / secondAssume we can only scan all pixels of entire screen 30 times / second To reduce flicker, divide frame into two “fields” of odd and even linesTo reduce flicker, divide frame into two “fields” of odd and even lines Interlaced Scanning Assume we can only scan all pixels of entire screen 30 times / secondAssume we can only scan all pixels of entire screen 30 times / second To reduce flicker, divide frame into two “fields” of odd and even linesTo reduce flicker, divide frame into two “fields” of odd and even lines

12. March 1, 2009Dr. Muhammed Al-Mulhem12 Display Technology: Color CRTs Color CRTs are much 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 much 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 arrangementIn-line electron gun arrangement

13. March 1, 2009Dr. Muhammed Al-Mulhem13 Display Technology: Color CRTs Color CRTs have Three electron gunsThree electron guns A metal shadow mask to differentiate the beamsA metal shadow mask to differentiate the beams Color CRTs have Three electron gunsThree electron guns A metal shadow mask to differentiate the beamsA metal shadow mask to differentiate the beams

14. March 1, 2009Dr. Muhammed Al-Mulhem14 Display Technology: Raster Raster CRT pros: Allows solids, not just wireframes.Allows solids, not just wireframes. Leverages low-cost CRT technologyLeverages low-cost CRT technology Bright! Display emits lightBright! Display emits lightCons: 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: Allows solids, not just wireframes.Allows solids, not just wireframes. Leverages low-cost CRT technologyLeverages low-cost CRT technology Bright! Display emits lightBright! Display emits lightCons: 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

15. March 1, 2009Dr. Muhammed Al-Mulhem15 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 –requires synchronization between video signal and electron beam vertical sync pulse Early computer displaysEarly computer displays –avoided synchronization using ‘vector’ algorithm –flicker 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 –requires synchronization between video signal and electron beam vertical sync pulse Early computer displaysEarly computer displays –avoided synchronization using ‘vector’ algorithm –flicker and refresh were problematic

16. March 1, 2009Dr. Muhammed Al-Mulhem16 CRTs – A Review Raster Displays (early 70s)Raster Displays (early 70s) –like television, scan all pixels in regular pattern –use frame buffer (video RAM) to eliminate sync problems RAMRAM –¼ MB (256 KB) cost $2 million in 1971 –Do some math… - 1280 x 1024 screen resolution = 1,310,720 pixels - Monochrome color (binary) requires 160 KB - High resolution color requires 5.2 MB Raster Displays (early 70s)Raster Displays (early 70s) –like television, scan all pixels in regular pattern –use frame buffer (video RAM) to eliminate sync problems RAMRAM –¼ MB (256 KB) cost $2 million in 1971 –Do some math… - 1280 x 1024 screen resolution = 1,310,720 pixels - Monochrome color (binary) requires 160 KB - High resolution color requires 5.2 MB

17. March 1, 2009Dr. Muhammed Al-Mulhem17 Flat-panel display Flat-panel refers to a class of video devices that have reduced Volume, Weight, and Power requirements compared to a CRT.Flat-panel refers to a class of video devices that have reduced Volume, Weight, and Power requirements compared to a CRT. A significant feature of flat-panel displays is that they are thinner than CRTs, and we can hang them on walls or wear them on our wrists.A significant feature of flat-panel displays is that they are thinner than CRTs, and we can hang them on walls or wear them on our wrists. Flat-panel refers to a class of video devices that have reduced Volume, Weight, and Power requirements compared to a CRT.Flat-panel refers to a class of video devices that have reduced Volume, Weight, and Power requirements compared to a CRT. A significant feature of flat-panel displays is that they are thinner than CRTs, and we can hang them on walls or wear them on our wrists.A significant feature of flat-panel displays is that they are thinner than CRTs, and we can hang them on walls or wear them on our wrists.

18. March 1, 2009Dr. Muhammed Al-Mulhem18 Display Technology: LCDs Liquid-crystal displays (LCDs)Liquid-crystal displays (LCDs) Commonly used in small systems, such as laptop computers and calculators.Commonly used in small systems, such as laptop computers and calculators. It produces a picture by passing polarized light from the surrounding or from an internal light source through a liquid-crystal material.It produces a picture by passing polarized light from the surrounding or from an internal light source through a liquid-crystal material. Liquid-crystal displays (LCDs)Liquid-crystal displays (LCDs) Commonly used in small systems, such as laptop computers and calculators.Commonly used in small systems, such as laptop computers and calculators. It produces a picture by passing polarized light from the surrounding or from an internal light source through a liquid-crystal material.It produces a picture by passing polarized light from the surrounding or from an internal light source through a liquid-crystal material.

19. March 1, 2009Dr. Muhammed Al-Mulhem19 Display Technology: LCDs Organic molecules, naturally in crystalline state, that liquefy when excited by heat or E fieldOrganic molecules, naturally in crystalline state, that 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, that liquefy when excited by heat or E fieldOrganic molecules, naturally in crystalline state, that liquefy when excited by heat or E field Crystalline state twists polarized light 90º.Crystalline state twists polarized light 90º.

20. March 1, 2009Dr. Muhammed Al-Mulhem20 Display Technology: Plasma Plasma display panels Also called gas-discharge displays.Also called gas-discharge displays. Constructed by filling the region between two glass plates with a mixture of gases that usually include neon.Constructed by filling the region between two glass plates with a mixture of gases that usually include neon. Similar in principle to fluorescent light tubes.Similar in principle to fluorescent light tubes. Plasma display panels Also called gas-discharge displays.Also called gas-discharge displays. Constructed by filling the region between two glass plates with a mixture of gases that usually include neon.Constructed by filling the region between two glass plates with a mixture of gases that usually include neon. Similar in principle to fluorescent light tubes.Similar in principle to fluorescent light tubes.

21. March 1, 2009Dr. Muhammed Al-Mulhem21 Display Technology: Plasma Plasma display panels Firing voltages applied to an intersecting pair of horizontal and vertical conductors cause the gas at the intersection of the two conductors to break down into a glowing plasma of electron and ions.Firing voltages applied to an intersecting pair of horizontal and vertical conductors cause the gas at the intersection of the two conductors to break down into a glowing plasma of electron and ions. Plasma display panels Firing voltages applied to an intersecting pair of horizontal and vertical conductors cause the gas at the intersection of the two conductors to break down into a glowing plasma of electron and ions.Firing voltages applied to an intersecting pair of horizontal and vertical conductors cause the gas at the intersection of the two conductors to break down into a glowing plasma of electron and ions.

22. March 1, 2009Dr. Muhammed Al-Mulhem22 Display Technology: Plasma Plasma display panels Picture definition is stored in a refresh buffer.Picture definition is stored in a refresh buffer. Firing voltages are applied to refresh the pixel positions, at the intersection of the conductors, 60 times per second.Firing voltages are applied to refresh the pixel positions, at the intersection of the conductors, 60 times per second. Plasma display panels Picture definition is stored in a refresh buffer.Picture definition is stored in a refresh buffer. Firing voltages are applied to refresh the pixel positions, at the intersection of the conductors, 60 times per second.Firing voltages are applied to refresh the pixel positions, at the intersection of the conductors, 60 times per second.

23. March 1, 2009Dr. Muhammed Al-Mulhem23 Display Technology Plasma Display Panel Pros Large viewing angleLarge viewing angle Good for large-format displaysGood for large-format displays Fairly brightFairly brightCons 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 Pros Large viewing angleLarge viewing angle Good for large-format displaysGood for large-format displays Fairly brightFairly brightCons ExpensiveExpensive Large pixelsLarge pixels Phosphors gradually depletePhosphors gradually deplete Less bright than CRTs, using more powerLess bright than CRTs, using more power

24. March 1, 2009Dr. Muhammed Al-Mulhem24 Review Read Chapter 2 Details about display devicesDetails about display devices Read Chapter 2 Details about display devicesDetails about display devices