CRTs – A Review • CRT technology hasn’t changed much in 50 years CRT technology hasn’t changed much in 50 years • Early television technology Early television technology – high resolution high resolution – requires synchronization between video signal and electron requires synchronization between video signal and electron beam vertical sync pulse beam vertical sync pulse • Early computer displays Early computer displays – avoided synchronization using ‘vector’ algorithm avoided synchronization using ‘vector’ algorithm – flicker and refresh were problematic flicker and refresh were problematic
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CRTs – A Review CRT technology hasn’t changed much in 50 yearsCRT technology hasn’t changed much in 50 years Early television technologyEarly television.
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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
• LCDs: organic molecules, naturally in crystalline LCDs: organic molecules, naturally in crystalline state, that liquefy when excited by heat or E fieldstate, that liquefy when excited by heat or E field
• Crystalline state twists polarized light 90º. Crystalline state twists polarized light 90º.
• LCDs: organic molecules, naturally in crystalline LCDs: organic molecules, naturally in crystalline state, that liquefy when excited by heat or E fieldstate, that liquefy when excited by heat or E field
• Crystalline state twists polarized light 90º. Crystalline state twists polarized light 90º.
• LCDs: organic molecules, naturally in crystalline LCDs: organic molecules, naturally in crystalline state, that liquefy when excited by heat or E fieldstate, that liquefy when excited by heat or E field
• Crystalline state twists polarized light 90ºCrystalline state twists polarized light 90º
• LCDs: organic molecules, naturally in crystalline LCDs: organic molecules, naturally in crystalline state, that liquefy when excited by heat or E fieldstate, that liquefy when excited by heat or E field
• Crystalline state twists polarized light 90ºCrystalline state twists polarized light 90º
• LCDs act as light valves, not light emitters, and thus rely on an LCDs act as light valves, not light emitters, and thus rely on an external light source.external light source.
• LCDs act as light valves, not light emitters, and thus rely on an LCDs act as light valves, not light emitters, and thus rely on an external light source.external light source.
• Laptop screenLaptop screen
– backlitbacklit
– transmissive displaytransmissive display
• Palm Pilot/Game BoyPalm Pilot/Game Boy
– reflective displayreflective display
Display Technology: Plasma
Plasma display panelsPlasma display panels
• Similar in principle to Similar in principle to fluorescent light tubesfluorescent light tubes
• Small gas-filled capsules Small gas-filled capsules are excited by electric field,are excited by electric field,emits UV lightemits UV light
• UV excites phosphorUV excites phosphor
• Phosphor relaxes, emits Phosphor relaxes, emits some other colorsome other color
Plasma display panelsPlasma display panels
• Similar in principle to Similar in principle to fluorescent light tubesfluorescent light tubes
• Small gas-filled capsules Small gas-filled capsules are excited by electric field,are excited by electric field,emits UV lightemits UV light
• UV excites phosphorUV excites phosphor
• Phosphor relaxes, emits Phosphor relaxes, emits some other colorsome other color
• The display of the future? Many think so.The display of the future? Many think so.
• OLEDs function like regular semiconductor LEDsOLEDs function like regular semiconductor LEDs
• But they emit lightBut they emit light
– Thin-film deposition of organic, light-Thin-film deposition of organic, light-emitting molecules through vapor emitting molecules through vapor sublimation in a vacuum.sublimation in a vacuum.
– Dope emissive layers with fluorescent Dope emissive layers with fluorescent molecules to create color.molecules to create color.
• The display of the future? Many think so.The display of the future? Many think so.
• OLEDs function like regular semiconductor LEDsOLEDs function like regular semiconductor LEDs
• But they emit lightBut they emit light
– Thin-film deposition of organic, light-Thin-film deposition of organic, light-emitting molecules through vapor emitting molecules through vapor sublimation in a vacuum.sublimation in a vacuum.
– Dope emissive layers with fluorescent Dope emissive layers with fluorescent molecules to create color.molecules to create color.
• Light-emitting, and quite bright (daylight visible)Light-emitting, and quite bright (daylight visible)
• Large viewing angleLarge viewing angle
• Fast (< 1 microsecond off-on-off)Fast (< 1 microsecond off-on-off)
• Can be made large or smallCan be made large or small
• Available for cell phones and car stereosAvailable for cell phones and car stereos
OLED pros:OLED pros:• TransparentTransparent
• FlexibleFlexible
• Light-emitting, and quite bright (daylight visible)Light-emitting, and quite bright (daylight visible)
• Large viewing angleLarge viewing angle
• Fast (< 1 microsecond off-on-off)Fast (< 1 microsecond off-on-off)
• Can be made large or smallCan be made large or small
• Available for cell phones and car stereosAvailable for cell phones and car stereos
Display Technologies: Organic LED Arrays
OLED cons:OLED cons:• Not very robust, display lifetime a key issueNot very robust, display lifetime a key issue
• Currently only passive matrix displaysCurrently only passive matrix displays
– Passive matrix:Passive matrix: Pixels are illuminated in scanline Pixels are illuminated in scanline order (like a raster display), but the lack of order (like a raster display), but the lack of phospherescence causes flickerphospherescence causes flicker
– Active matrix:Active matrix: A polysilicate layer provides thin film A polysilicate layer provides thin film transistors at each pixel, allowing direct pixel transistors at each pixel, allowing direct pixel access and constant illuminationaccess and constant illumination
See See http://www.howstuffworks.com/lcd4.htmhttp://www.howstuffworks.com/lcd4.htm for more info for more info
OLED cons:OLED cons:• Not very robust, display lifetime a key issueNot very robust, display lifetime a key issue
• Currently only passive matrix displaysCurrently only passive matrix displays
– Passive matrix:Passive matrix: Pixels are illuminated in scanline Pixels are illuminated in scanline order (like a raster display), but the lack of order (like a raster display), but the lack of phospherescence causes flickerphospherescence causes flicker
– Active matrix:Active matrix: A polysilicate layer provides thin film A polysilicate layer provides thin film transistors at each pixel, allowing direct pixel transistors at each pixel, allowing direct pixel access and constant illuminationaccess and constant illumination
See See http://www.howstuffworks.com/lcd4.htmhttp://www.howstuffworks.com/lcd4.htm for more info for more info
Movie Theaters
U.S. film projectors play film at 24 fpsU.S. film projectors play film at 24 fps• Projectors have a shutter to block light during frame advanceProjectors have a shutter to block light during frame advance
• To reduce flicker, shutter opens twice for each frame – resulting in 48 To reduce flicker, shutter opens twice for each frame – resulting in 48 fps flashingfps flashing
• 48 fps is perceptually acceptable48 fps is perceptually acceptable
European film projectors play film at 25 fpsEuropean film projectors play film at 25 fps• American films are played ‘as is’ in Europe, resulting in everything American films are played ‘as is’ in Europe, resulting in everything
moving 4% fastermoving 4% faster
• Faster movements and increased audio pitch are considered Faster movements and increased audio pitch are considered perceptually acceptableperceptually acceptable
U.S. film projectors play film at 24 fpsU.S. film projectors play film at 24 fps• Projectors have a shutter to block light during frame advanceProjectors have a shutter to block light during frame advance
• To reduce flicker, shutter opens twice for each frame – resulting in 48 To reduce flicker, shutter opens twice for each frame – resulting in 48 fps flashingfps flashing
• 48 fps is perceptually acceptable48 fps is perceptually acceptable
European film projectors play film at 25 fpsEuropean film projectors play film at 25 fps• American films are played ‘as is’ in Europe, resulting in everything American films are played ‘as is’ in Europe, resulting in everything
moving 4% fastermoving 4% faster
• Faster movements and increased audio pitch are considered Faster movements and increased audio pitch are considered perceptually acceptableperceptually acceptable
Viewing Movies at Home
Film to DVD transferFilm to DVD transfer
• Problem: 24 film fps must be converted to Problem: 24 film fps must be converted to
– NTSC U.S. television interlaced 29.97 fps 768x494 NTSC U.S. television interlaced 29.97 fps 768x494
– PAL Europe television 25 fps 752x582PAL Europe television 25 fps 752x582
Use 3:2 PulldownUse 3:2 Pulldown
• First frame of movie is broken into first three fields (odd, even, odd)First frame of movie is broken into first three fields (odd, even, odd)
• Next frame of movie is broken into next two fields (even, odd)Next frame of movie is broken into next two fields (even, odd)
• Next frame of movie is broken into next three fields (even, odd, even)…Next frame of movie is broken into next three fields (even, odd, even)…
Film to DVD transferFilm to DVD transfer
• Problem: 24 film fps must be converted to Problem: 24 film fps must be converted to
– NTSC U.S. television interlaced 29.97 fps 768x494 NTSC U.S. television interlaced 29.97 fps 768x494
– PAL Europe television 25 fps 752x582PAL Europe television 25 fps 752x582
Use 3:2 PulldownUse 3:2 Pulldown
• First frame of movie is broken into first three fields (odd, even, odd)First frame of movie is broken into first three fields (odd, even, odd)
• Next frame of movie is broken into next two fields (even, odd)Next frame of movie is broken into next two fields (even, odd)
• Next frame of movie is broken into next three fields (even, odd, even)…Next frame of movie is broken into next three fields (even, odd, even)…
Additional Displays
Display WallsDisplay Walls
• PrincetonPrinceton
• StanfordStanford
• UVa – Greg HumphreysUVa – Greg Humphreys
Display WallsDisplay Walls
• PrincetonPrinceton
• StanfordStanford
• UVa – Greg HumphreysUVa – Greg Humphreys
Display Wall Alignment
Additional Displays
StereoStereoStereoStereo
Visual System
We’ll discuss more fully later in semester but…We’ll discuss more fully later in semester but…
• Our eyes don’t mind smoothing across timeOur eyes don’t mind smoothing across time
– Still pictures appear to animateStill pictures appear to animate
• Our eyes don’t mind smoothing across spaceOur eyes don’t mind smoothing across space
– Discrete pixels blend into continuous color sheetsDiscrete pixels blend into continuous color sheets
We’ll discuss more fully later in semester but…We’ll discuss more fully later in semester but…
• Our eyes don’t mind smoothing across timeOur eyes don’t mind smoothing across time
– Still pictures appear to animateStill pictures appear to animate
• Our eyes don’t mind smoothing across spaceOur eyes don’t mind smoothing across space
– Discrete pixels blend into continuous color sheetsDiscrete pixels blend into continuous color sheets
Mathematical Foundations
Angel appendix B and CAngel appendix B and C
I’ll give a brief, informal review of some of the I’ll give a brief, informal review of some of the mathematical tools we’ll employmathematical tools we’ll employ• Geometry (2D, 3D)Geometry (2D, 3D)
• TrigonometryTrigonometry
• Vector spaces Vector spaces
– Points, vectors, and coordinatesPoints, vectors, and coordinates
• Dot and cross productsDot and cross products
Angel appendix B and CAngel appendix B and C
I’ll give a brief, informal review of some of the I’ll give a brief, informal review of some of the mathematical tools we’ll employmathematical tools we’ll employ• Geometry (2D, 3D)Geometry (2D, 3D)
• TrigonometryTrigonometry
• Vector spaces Vector spaces
– Points, vectors, and coordinatesPoints, vectors, and coordinates
• Dot and cross productsDot and cross products
Scalar Spaces
• Scalars: Scalars: … …
• Addition and multiplication (+ and Addition and multiplication (+ and ) operations defined) operations defined
• Scalar operations areScalar operations are
– Associative: Associative:
– Commutative: Commutative:
– Distributive: Distributive:
• Scalars: Scalars: … …
• Addition and multiplication (+ and Addition and multiplication (+ and ) operations defined) operations defined
• Scalar multiplication “streches” a vector, changing its Scalar multiplication “streches” a vector, changing its length (length (magnitudemagnitude) but not its direction) but not its direction
• Scalar multiplication “streches” a vector, changing its Scalar multiplication “streches” a vector, changing its length (length (magnitudemagnitude) but not its direction) but not its direction
Dot Product
• The The dot productdot product or, more generally, or, more generally, inner productinner product of two vectors of two vectors is a scalar:is a scalar:
• Useful for many purposesUseful for many purposes
• Computing the length (Euclidean Norm) of a vector: Computing the length (Euclidean Norm) of a vector: lengthlength((vv) = ||) = ||vv|| = sqrt(|| = sqrt(v • v • v)v)
• NormalizingNormalizing a vector, making it unit-length: a vector, making it unit-length: v = v / ||v||v = v / ||v||
• Computing the angle between two vectors:Computing the angle between two vectors:
u • v u • v = |= |uu| || |vv| cos(θ)| cos(θ)
• Checking two vectors for orthogonalityChecking two vectors for orthogonality
– u • v = 0.0u • v = 0.0
• The The dot productdot product or, more generally, or, more generally, inner productinner product of two vectors of two vectors is a scalar:is a scalar:
• Useful for many purposesUseful for many purposes
• Computing the length (Euclidean Norm) of a vector: Computing the length (Euclidean Norm) of a vector: lengthlength((vv) = ||) = ||vv|| = sqrt(|| = sqrt(v • v • v)v)
• NormalizingNormalizing a vector, making it unit-length: a vector, making it unit-length: v = v / ||v||v = v / ||v||
• Computing the angle between two vectors:Computing the angle between two vectors:
u • v u • v = |= |uu| || |vv| cos(θ)| cos(θ)
• Checking two vectors for orthogonalityChecking two vectors for orthogonality
– u • v = 0.0u • v = 0.0
u θ
v
ProjectingProjecting one vector onto another one vector onto another
• If If vv is a unit vector and we have another vector, is a unit vector and we have another vector, ww
• We can project We can project ww perpendicularly onto perpendicularly onto vv
• And the result,And the result, u u, has length , has length w w • • vv
ProjectingProjecting one vector onto another one vector onto another
• If If vv is a unit vector and we have another vector, is a unit vector and we have another vector, ww
• We can project We can project ww perpendicularly onto perpendicularly onto vv
• And the result,And the result, u u, has length , has length w w • • vv
Dot Product
u
w
v
wv
wv
wvw
wu
)cos(
Dot Product
Is commutativeIs commutative
• u • v = v • uu • v = v • u
Is distributive with respect to additionIs distributive with respect to addition
• u • (v + w) = u • v + u • wu • (v + w) = u • v + u • w
Is commutativeIs commutative
• u • v = v • uu • v = v • u
Is distributive with respect to additionIs distributive with respect to addition
• u • (v + w) = u • v + u • wu • (v + w) = u • v + u • w
Cross Product
The The cross productcross product or or vector productvector product of two vectors is a of two vectors is a vector:vector:
The cross product of two vectors is orthogonal to bothThe cross product of two vectors is orthogonal to both
Right-hand rule dictates direction of cross productRight-hand rule dictates direction of cross product
The The cross productcross product or or vector productvector product of two vectors is a of two vectors is a vector:vector:
The cross product of two vectors is orthogonal to bothThe cross product of two vectors is orthogonal to both
Right-hand rule dictates direction of cross productRight-hand rule dictates direction of cross product
Orient your right hand such that your palm is at the Orient your right hand such that your palm is at the beginning of A and your fingers point in the direction of beginning of A and your fingers point in the direction of AA
Twist your hand about the A-axis such that B extends Twist your hand about the A-axis such that B extends perpendicularly from your palmperpendicularly from your palm
As you curl your fingers to make a fist, your thumb will As you curl your fingers to make a fist, your thumb will point in the direction of the cross productpoint in the direction of the cross product
Orient your right hand such that your palm is at the Orient your right hand such that your palm is at the beginning of A and your fingers point in the direction of beginning of A and your fingers point in the direction of AA
Twist your hand about the A-axis such that B extends Twist your hand about the A-axis such that B extends perpendicularly from your palmperpendicularly from your palm
As you curl your fingers to make a fist, your thumb will As you curl your fingers to make a fist, your thumb will point in the direction of the cross productpoint in the direction of the cross product
Orient your right hand such that your palm is at the Orient your right hand such that your palm is at the beginning of A and your fingers point in the direction of beginning of A and your fingers point in the direction of AA
Twist your hand about the A-axis such that B extends Twist your hand about the A-axis such that B extends perpendicularly from your palmperpendicularly from your palm
As you curl your fingers to make a fist, your thumb will As you curl your fingers to make a fist, your thumb will point in the direction of the cross productpoint in the direction of the cross product
Orient your right hand such that your palm is at the Orient your right hand such that your palm is at the beginning of A and your fingers point in the direction of beginning of A and your fingers point in the direction of AA
Twist your hand about the A-axis such that B extends Twist your hand about the A-axis such that B extends perpendicularly from your palmperpendicularly from your palm
As you curl your fingers to make a fist, your thumb will As you curl your fingers to make a fist, your thumb will point in the direction of the cross productpoint in the direction of the cross product