Human Interfaces

Human Interfaces

1. Human Computer Interaction (HCI)

   • Perceptual Process (Input)
     • Fixations
       • info absorbed in eyes (60ms)
     • Saccades
       • quick movement between eyes (30ms)
     • Rauding rate
       • Raud: read with understanding
       • 30 letters/s
   • Cognitive Process (Process)
     • Hick Hyman Law
   • Motor Process (Output)
     • Fitt Law
       • - Predicts Motor Time (MT)
         • - Time taken to point to object
           • point mouse cursor to icon
             • FORMULA
               • Larger D => Larger MT
               • Larger W => Smaller MT
               • Application of Fitt Law
                 • Far but big targets may be easier to reach than near but small target
                 • Edges of your screen are very fast to reach
                   • Menu Bar in Mac OS/Linux. Not Windows
                 • Corners are even faster
                 • Pop-up menu is fast
                   • Right click

2. Touch Panels

   • advanced input devices that are mounted on display systems
     • Many Different Technologies
       • Resistive
         • When there is a touch, resistance changes and is measured to locate the touch
           • It works by applying a voltage across a resistor network
       • Capacitive
         • When there is a touch, the capacitance changes and it will be measured
           • Two Types:
             • Surface Capacitance
               • There are 4 voltage sources with current measurement circuit on the screen
             • Projected Capacitance
               • Self Capacitance
                 • When there is touch:
                   • 1. Self capacitance increases
                   • 2. Capacitors in parallel
               • Mutual Capacitance
                 • When there is touch:
                   • 1. Mutual capacitance decreases
                   • 2. Capacitors in series

3. Display technologies - LCD

   • Basic Definition
     • Pixel
       • picture element, basic building block on computer display
     • Resolution
       • how many pixels a display panel has
     • Aspect ratio
       • to describes the proportional relationship between its width and its height
     • Bits per pixel/bit depth
       • how many bits a pixel has to describe brightness and color of that pixel
     • Frame Buffer
       • a memory allocated for data used to periodically refresh the display

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