Design Realization lecture 24

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Design Realization lecture 24

• John Canny
• 11/18/03

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Last time

• Simulation in Matlab/Simulink
• PID stabilization
• Automatic code generation - example

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This time

• Improvisation application to circuits and
  real-time programming.
• Optics physics of light.

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Improvisation

• Exploration of the design possibilities of a
  medium.
• Earlier we listed qualities of media.
• For technical media, list their capabilities.
• E.g. speed, complexity, cost, reliability, for a
  system network, processor, sensor etc

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Improvisation extreme designs

• Trying to achieve a design goal using extreme
  designs
• E.g. expressive animation using motion only, or
  using high-performance characters.
• Mood change using lighting only, or camera
  position.
• Chair designs very light/heavy, simple/complex,
  single material or form

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Improvisation extreme designs

• Technical media
• Recognition with one type of sensor (e.g. light).
  
• Complex control with many simple chips (e.g.
  PICs), or with one complex chip (or a PC).
• Communication with simple network (serial) vs. a
  stack such as ethernet or bluetooth.
• PC board layout all surface-mount components,
  one-sided vs. two-sided layout, high vs. low
  density.

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Improvisation pattern libraries

• Normally, you learn a new medium by finding and
  applying design patterns.
• Application notes for PICs, sample circuit
  boards.
• As you become accomplished, you should save your
  own design patterns somewhere.

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Improvisation challenging conventions

• Design patterns are a good way to learn, but
  conventions should be challenged regularly.
• This involves understanding the essential
  functionality of components, e.g.
• RS485 transceivers as multidrop bus drivers.
• Battery sensors as A/D converters.
• Once this is understood, youre free to design
  out of the box.

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• Break

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Why Optics?

• Most of our interaction with technology is
  visual computers, architecture, games
• Most of the media we consume are visual TV
  movies, newspaper, DVDs,
• There are many new component-ized optical
  technologies, and the design possibilities are
  excellent.

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Optics physics of light

• Light is electro-magnetic radiation with
  wavelengths from 400-700 nm.
• Longer wavelengths at thered end of the
  spectrum,grading to violet at the short end.

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Optics physics of light

• The eye contains two kinds of light-receptive
  cell called rods and cones.
• Cones are the color sensors
• The three typesallow the eye torespond to
  three-way color mixes.

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Additive color mixes

• Because of the 3 types of receptor, colors can be
  synthesized using 3 colored emitters
• Phosphors (in TV and CRT displays)
• White light with filters (LCD displays,
  projectors)
• LED displays

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Color Bases - XYZ

• To describe color, its convenient to define a
  different basis.
• The XYZ (CIE) basis uses X,Y coordinates to
  represent color, and Z to represent brightness.
• Allows colors to be plotted in 2D.
• They are related to R,G,B by a linear
  transformation
• R 2.739 -1.145 -0.424 X G
  -1.119 2.029 0.033 Y B 0.138 -0.333
  1.105 Z

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CIE plot

• Shows colors in XY coordinates.
• Saturated (full) colorsat the boundary.
• Light sources coverregions in the plot.
• Blended colors arein the convex hullof the
  source.
• (Line shows blackbody radiation color)

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HSV

• Another common basis is HSV (Hue, Saturation,
  Value).
• Hue is taken to be the angle of the color.
• Saturation is the distance from the vertical
  axis.
• Value is the height(brightness).
• Considered moreintuitive for color choice.

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YUV

• The last common basis is YUV (popular in cameras
  and digital images).
• Y is intensity, U,V encode color (can be
  negative).
• Y-only gives B/W image.
• U,V may have fewer bits than Y.
• Assuming 8-bit (256 colors), transformation is
• Y 0.299R 0.587G 0.114B
• U -0.169R - 0.331G 0.500B 128.0
• V 0.500R - 0.419G - 0.081B 128.0

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Subtractive color

• Pigments absorb specific colors, so they subtract
  colors from a painting or document.
• To mix pigments, we choose pigments that absorb
  just one color
• K brightness (black to white)
• Cyan Blue Green White - Red
• Magenta Blue Red White - Green
• Yellow Red Green White Blue
• This gives the CMYK system.

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High quality color

• Its not possible to get most pure colors with 3
  phosphors/pigments(all colors are in theconvex
  hull of the basecolors).
• High-quality systemsuse more colors (e.g.
  7)spaced around the color wheel to provide
  better coverage.

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Light waves (EM radiation)

• Light is a form of electromagnetic radiation.
• E (electric) and B (magnetic) fields are at right
  angles to direction of propagation.

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2D light wave model

• Its convenient (for drawing and analysis) to look
  at light wave propagation in 2D.
• Wavefronts represent maxima of E or B at a given
  time instant.

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Superposition

• Light (and other EM radiation) obeys
  superposition
• The E/B field due to many sources is the sum of
  the field due to each source.
• A point source generates a spherical wave field.
• An extended source can be represented as a sum of
  point sources.

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Wavefronts and Rays

• From superposition, we can derive that waves
  propagate normal the the wavefront surface, and
  vice-versa.
• The ray description is most useful for describing
  the geometry of images.

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Reflection

• Most metals are excellent conductors.
• They reduce the E field to zero at the surface.
• This is equivalent to a field of point sources at
  the surface with opposite polarity.
• These sources re-radiatethe signal at the
  reflection angle.

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Reflection Ray representation

• Using the ray representation, incident and
  reflected light rays make the same angle with the
  surface normal.
• Incident, reflected rayand normal are all inthe
  same plane.
• If I, R, N unit vectors
• I?N R?N
• I?(N ? R) 0

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Refraction wave representation

• In most transparent materials (plastic, glass),
  light propagates slower than in air.
• At the boundary, wavefronts bend

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Refraction ray representation

• In terms of rays, light bends toward the normal
  in the slower material.