CRTs

1
CRTs A Review

• CRT technology hasnt changed much in 50 years
• Early television technology
• high resolution
• requires synchronization between video signal and
  electron beam vertical sync pulse
• Early computer displays
• avoided synchronization using vector algorithm
• flicker and refresh were problematic

2
CRTs A Review

• Raster Displays (early 70s)
• like television, scan all pixels in regular
  pattern
• use frame buffer (video RAM) to eliminate sync
  problems
• RAM
• 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

3
Display Technology LCDs

• Liquid Crystal Displays (LCDs)
• LCDs organic molecules, naturally in crystalline
  state, that liquefy when excited by heat or E
  field
• Crystalline state twists polarized light 90º.

4
Display Technology LCDs

• Liquid Crystal Displays (LCDs)
• LCDs organic molecules, naturally in crystalline
  state, that liquefy when excited by heat or E
  field
• Crystalline state twists polarized light 90º

5
Display Technology LCDs

• Transmissive reflective LCDs
• LCDs act as light valves, not light emitters, and
  thus rely on an external light source.
• Laptop screen
• backlit
• transmissive display
• Palm Pilot/Game Boy
• reflective display

6
Display Technology Plasma

• Plasma display panels
• Similar in principle to fluorescent light tubes
• Small gas-filled capsules are excited by
  electric field,emits UV light
• UV excites phosphor
• Phosphor relaxes, emits some other color

7
Display Technology

• Plasma Display Panel Pros
• Large viewing angle
• Good for large-format displays
• Fairly bright
• Cons
• Expensive
• Large pixels (1 mm versus 0.2 mm)
• Phosphors gradually deplete
• Less bright than CRTs, using more power

8
Display Technology DMD / DLP

• Digital Micromirror Devices (projectors) or
  Digital Light Processing
• Microelectromechanical (MEM) devices, fabricated
  with VLSI techniques

9
Display Technology DMD / DLP

• DMDs are truly digital pixels
• Vary grey levels by modulating pulse length
• Color multiple chips, or color-wheel
• Great resolution
• Very bright
• Flicker problems

10
Display Technologies Organic LED Arrays

• Organic Light-Emitting Diode (OLED) Arrays
• The display of the future? Many think so.
• OLEDs function like regular semiconductor LEDs
• But they emit light
• Thin-film deposition of organic, light-emitting
  molecules through vapor sublimation in a vacuum.
• Dope emissive layers with fluorescent molecules
  to create color.

http//www.kodak.com/global/en/professional/produc
ts/specialProducts/OEL/creating.jhtml
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Display Technologies Organic LED Arrays

• OLED pros
• Transparent
• Flexible
• Light-emitting, and quite bright (daylight
  visible)
• Large viewing angle
• Fast (lt 1 microsecond off-on-off)
• Can be made large or small
• Available for cell phones and car stereos

12
Display Technologies Organic LED Arrays

• OLED cons
• Not very robust, display lifetime a key issue
• Currently only passive matrix displays
• Passive matrix Pixels are illuminated in
  scanline order (like a raster display), but the
  lack of phospherescence causes flicker
• Active matrix A polysilicate layer provides thin
  film transistors at each pixel, allowing direct
  pixel access and constant illumination
• See http//www.howstuffworks.com/lcd4.htm for
  more info

13
Movie Theaters

• U.S. film projectors play film at 24 fps
• Projectors have a shutter to block light during
  frame advance
• To reduce flicker, shutter opens twice for each
  frame resulting in 48 fps flashing
• 48 fps is perceptually acceptable
• European film projectors play film at 25 fps
• American films are played as is in Europe,
  resulting in everything moving 4 faster
• Faster movements and increased audio pitch are
  considered perceptually acceptable

14
Viewing Movies at Home

• Film to DVD transfer
• Problem 24 film fps must be converted to
• NTSC U.S. television interlaced 29.97 fps 768x494
  
• PAL Europe television 25 fps 752x582
• Use 32 Pulldown
• 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 three
  fields (even, odd, even)

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Additional Displays

• Display Walls
• Princeton
• Stanford
• UVa Greg Humphreys

17
Display Wall Alignment
18
Additional Displays

• Stereo

19
Visual System

• Well discuss more fully later in semester but
• Our eyes dont mind smoothing across time
• Still pictures appear to animate
• Our eyes dont mind smoothing across space
• Discrete pixels blend into continuous color sheets

20
Mathematical Foundations

• Angel appendix B and C
• Ill give a brief, informal review of some of the
  mathematical tools well employ
• Geometry (2D, 3D)
• Trigonometry
• Vector spaces
• Points, vectors, and coordinates
• Dot and cross products

21
Scalar Spaces

• Scalars a, b,
• Addition and multiplication ( and h) operations
  defined
• Scalar operations are
• Associative a (b g) (a b) g
• Commutative a b b a a h b b h a
• Distributive a h(b h g) (a h b) h g a h(b
  g) (a h b) (a h g)

22
Scalar Spaces

• Additive Identity 0
• a 0 0 a a
• Multiplicative Identity 1
• a h 1 1 h a a
• Additive Inverse -a
• a (-a) 0
• Multiplicative Inverse a-1
• a h a-1 1

23
Vector Spaces

• Two types of elements
• Scalars (real numbers) a, b, g, d,
• Vectors (n-tuples) u, v, w,
• Operations
• Addition
• Subtraction

24
Vector Addition/Subtraction

• operation u v, with
• Identity 0 v 0 v
• Inverse - v (-v) 0
• Addition uses the parallelogram rule

v
u
-v
v
u-v
-v
u
25
Affine Spaces

• Vector spaces lack position and distance
• They have magnitude and direction but no location
• Add a new primitive, the point
• Permits describing vectors relative to a common
  location
• Point-point subtraction yields a vector
• A point and three vectors define a 3-D coordinate
  system

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Points

• Points support these operations
• Point-point subtraction Q - P v
• Result is a vector pointing from P to Q
• Vector-point addition P v Q
• Result is a new point
• Note that the addition of two points is not
  defined

27
Coordinate Systems

• Grasp z-axis with hand
• Thumb points in direction of z-axis
• Roll fingers from positive x-axis towards
  positive y-axis

28
Euclidean Spaces

• Euclidean spaces permit the definition of
  distance
• Dot product - distance between two vectors
• Projection of one vector onto another

29
Euclidean Spaces

• We commonly use vectors to represent
• Points in space (i.e., location)
• Displacements from point to point
• Direction (i.e., orientation)
• We frequently use these operations
• Dot Product
• Cross Product
• Norm

30
Scalar Multiplication

• Scalar multiplication
• Distributive rule a(u v) a(u) a(v)
• (a b)u au bu
• Scalar multiplication streches a vector,
  changing its length (magnitude) but not its
  direction

31
Dot Product

• The dot product or, more generally, inner product
  of two vectors is a scalar
• v1 v2 x1x2 y1y2 z1z2 (in 3D)
• Useful for many purposes
• Computing the length (Euclidean Norm) of a
  vector length(v) v sqrt(v v)
• Normalizing a vector, making it unit-length v
  v / v
• Computing the angle between two vectors
• u v u v cos(?)
• Checking two vectors for orthogonality
• u v 0.0

32
Dot Product

• Projecting one vector onto another
• If v is a unit vector and we have another vector,
  w
• We can project w perpendicularly onto v
• And the result, u, has length w v

33
Dot Product

• Is commutative
• u v v u
• Is distributive with respect to addition
• u (v w) u v u w

34
Cross Product

• The cross product or vector product of two
  vectors is a vector
• The cross product of two vectors is orthogonal to
  both
• Right-hand rule dictates direction of cross
  product

35
Cross Product Right Hand Rule

• See http//www.phy.syr.edu/courses/video/RightHan
  dRule/index2.html
• Orient your right hand such that your palm is at
  the beginning of A and your fingers point in the
  direction of A
• Twist your hand about the A-axis such that B
  extends perpendicularly from your palm
• As you curl your fingers to make a fist, your
  thumb will point in the direction of the cross
  product

36
Cross Product Right Hand Rule

• See http//www.phy.syr.edu/courses/video/RightHan
  dRule/index2.html
• Orient your right hand such that your palm is at
  the beginning of A and your fingers point in the
  direction of A
• Twist your hand about the A-axis such that B
  extends perpendicularly from your palm
• As you curl your fingers to make a fist, your
  thumb will point in the direction of the cross
  product

37
Cross Product Right Hand Rule

• See http//www.phy.syr.edu/courses/video/RightHan
  dRule/index2.html
• Orient your right hand such that your palm is at
  the beginning of A and your fingers point in the
  direction of A
• Twist your hand about the A-axis such that B
  extends perpendicularly from your palm
• As you curl your fingers to make a fist, your
  thumb will point in the direction of the cross
  product

38
Cross Product Right Hand Rule

• See http//www.phy.syr.edu/courses/video/RightHan
  dRule/index2.html
• Orient your right hand such that your palm is at
  the beginning of A and your fingers point in the
  direction of A
• Twist your hand about the A-axis such that B
  extends perpendicularly from your palm
• As you curl your fingers to make a fist, your
  thumb will point in the direction of the cross
  product

39
Cross Product Right Hand Rule

• See http//www.phy.syr.edu/courses/video/RightHan
  dRule/index2.html
• Orient your right hand such that your palm is at
  the beginning of A and your fingers point in the
  direction of A
• Twist your hand about the A-axis such that B
  extends perpendicularly from your palm
• As you curl your fingers to make a fist, your
  thumb will point in the direction of the cross
  product

40
2D Geometry

• Know your high school geometry
• Total angle around a circle is 360 or 2p
  radians
• When two lines cross
• Opposite angles are equivalent
• Angles along line sum to 180
• Similar triangles
• All corresponding angles are equivalent

41
Trigonometry

• Sine opposite over hypotenuse
• Cosine adjacent over hypotenuse
• Tangent opposite over adjacent
• Unit circle definitions
• sin (?) x
• cos (?) y
• tan (?) x/y
• etc

(x, y)
42
Slope-intercept Line Equation

• Slope m
• rise / run
• Slope (y - y1) / (x - x1) (y2 - y1) / (x2
  - x1)
• Solve for y
• y (y2 - y1)/(x2 - x1)x -(y2-y1)/(x2 -
  x1)x1 y1
• or y mx b

43
Parametric Line Equation

• Given points P1 (x1, y1) and P2 (x2, y2) x
  x1 t(x2 - x1) y y1 t(y2 - y1)
• When
• t0, we get (x1, y1)
• t1, we get (x2, y2)
• (0lttlt1), we get pointson the segment
  between(x1, y1) and (x2, y2)

y
P2 (x2, y2)
P1 (x1, y1)
x
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Other helpful formulas

• Length sqrt (x2 - x1)2 (y2 - y1)2
• Midpoint, p2, between p1 and p3
• p2 ((x1 x3) / 2, (y1 y3) / 2))
• Two lines are perpendicular if
• M1 -1/M2
• cosine of the angle between them is 0

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Reading

• Chapters 1 and Appendix B of Angel