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Touch Screens
Touch screens were developed to give the user the opportunity for
direct visual pointing. Unlike most pointing devices, the user doesn’t
have to navigate a pointer across the screen to click the desired target.
Instead the user can directly touch the screen to indicate a desired action.
Touch Screen technology has two options for its application: capacitive
and optical. Similar to keyboards, there is a capacitive design that uses
the same principle technology as capacitive keyboards. Capacitive touch
screens are composed of two capacitive sheets separated by air. When the
user makes a selection by touching the screen, the two sheets are pressed
together, changing the overall capacitance. The controller in the touch
screen sends the information to the computer indicating the XY coordinates
of the "touch".
Optical touch screens are different from any technology we have previously
discussed. The optical design determines the location of the user’s touch
by a grid-work of light beams. When the user touches the screen, he or
she interrupts the path of light beams crossing the screen. Then, the controller
in the screen can easily find the exact location of the users touch.
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