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Design Realization lecture 24

Design Realization lecture 24. John Canny 11/18/03. Last time. Simulation in Matlab/Simulink PID stabilization Automatic code generation - example. This time. Improvisation: application to circuits and real-time programming. Optics: physics of light. Improvisation.

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Design Realization lecture 24

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  1. Design Realization lecture 24 John Canny 11/18/03

  2. Last time • Simulation in Matlab/Simulink • PID stabilization • Automatic code generation - example

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

  4. 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…

  5. 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…

  6. 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.

  7. 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.

  8. 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, you’re free to design “out of the box”.

  9. Break

  10. 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.

  11. 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.

  12. 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.

  13. 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

  14. 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]

  15. 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)

  16. 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.

  17. 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 = 0.299*R + 0.587*G + 0.114*B U = -0.169*R - 0.331*G + 0.500*B + 128.0 V = 0.500*R - 0.419*G - 0.081*B + 128.0

  18. 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.

  19. 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.

  20. 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.

  21. 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.

  22. 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.

  23. 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.

  24. 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.

  25. 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

  26. Refraction – wave representation • In most transparent materials (plastic, glass), light propagates slower than in air. • At the boundary, wavefronts bend:

  27. Refraction – ray representation • In terms of rays, light bends toward the normal in the slower material.

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