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Touchscreen Implementation for Multi-Touch

Touchscreen Implementation for Multi-Touch. Design Team 2: Joey Grover Ahmad Alqudaihi Jason Grimes Dennis Wey. Touchscreens & Graphical User Interface. Guiding principles behind GUI Displays relevant information Intuitive technology Touchscreen Electronic Display

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Touchscreen Implementation for Multi-Touch

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  1. Touchscreen Implementation for Multi-Touch Design Team 2: Joey Grover Ahmad Alqudaihi Jason Grimes Dennis Wey

  2. Touchscreens & Graphical User Interface • Guiding principles behind GUI • Displays relevant information • Intuitive technology • Touchscreen • Electronic Display • Recognizes presence of user’s touch • Provides GUI and user control

  3. Touchscreen Technologies • Resistive • Capacitive • Surface • Projected • Optical imaging • Infrared

  4. Resistive Touchscreen • Composed of multiple layers separated by thin spaces • Using indium tin oxide (ITO) layers • Different standards • 4, 5, and 8 wire types • Each have advantages

  5. Resistive Touchscreen • User Presses Down • Contact is Made • Uniform Voltage on First Screen for X • Same on Second screen for Y • Happens instantaneously

  6. 4-Wire design • One screen for X • Another screen for Y • Both create voltage gradient. • Uses voltage divider

  7. Advantages • Works well with fingertip or stylus input • Generally most affordable touchscreen technology • Rugged/Durable • Has multi-touch input capabilities • Stantum • Touchco

  8. Disadvantages • Not as accurate • Multi-touch much more complex • Usually no discretion between stylus and hand • More pressure needed

  9. Capacitive Touch Technology Consists of: Insulator (glass or Air) Conductive coating (ITO) Two types: Surface projected

  10. Surface Capacitance Only one side is coated Electrodes at the edges Distribute voltage

  11. Surface Capacitance Cont. Before

  12. After Capacitor forms Current flows • Determine location • Controller • Ratio of currents , • XY coordinates R

  13. Projected Capacitance • Two parallel ITO layers • Two sheets of glass

  14. Projected Capacitance • Capacitor at each point on the surface

  15. Projected Capacitance Cont. E Field is projected through glass Finger couples with E field Capacitance changes

  16. Surface vs. Projected Limited resolution Single touch Operation with direct contact High resolution Multi touch Operation with indirect contact

  17. Multi-Touch Using Infrared

  18. Frustrated Total Internal Reflection • A process by which light is trapped within a medium and can be interrupted by a third medium of higher reflective index to cause light to escape. http://cs.nyu.edu/~jhan/ftirsense/ftirschematic.gif

  19. Rear Projection • Hardware • Infrared LED’s or lasers with line generator for optical dispersion • Glass surface or plexi-glass • Infrared Camera • Projector • Cost • Scalability http://reactivision.sourceforge.net/images/reactivision03.png

  20. Alternative Single-Unit Design • Eliminates rear projection • Expensive • Robustness http://wiki.fluidproject.org/display/fluid/Benchmarking+-+Touch+Screen+Options

  21. Software Surface Capture via Detector Digitized View

  22. Software Cont. • Interpret and Relay Information • Assign Objects or gestures with Unique ID# and location • Compare and Execute Feedback to User Raw Data

  23. Improving Accessibility? • Universal Design Principles • Utility for all users • Simple and intuitive • Touchscreens depend on visual feedback in order to use

  24. Pointing Device Gestures • Cursor movements as command shortcuts • Takes place of keyboard shortcuts • Useful in applications where keyboard use is less prominent or undesirable Above: Some possible cursor movement patterns for use in gesture support.

  25. Implementation: Step 1 • Filter Input • Sampling rate • Smooth out input data, get rid of unnecessary “noise” • Simplify data analysis

  26. Implementation: Step 2 • Vectorize • Separate x- and y-component • Compute dominant component and ignore smaller one • Store in array

  27. Implementation: Step 3 • Matching • Match captured vector array to pre-defined gesture library • If no match, pop smallest vector from array and repeat matching process

  28. Example Fig. 1 – User input Fig. 3 – After vectorization Fig. 2 – Captured/filtered pointer data Fig. 4 – Final matching result

  29. Goal • Allows for a quicker and more efficient UI • Universal Design • Enhances usability for visually-impaired as well as non-impaired • Easily added to existing touchscreen devices, no additional hardware required

  30. Questions?

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