06-11-2012, 12:01 PM
Touch Screen Technologies
[attachment=38270]
History
Touch screens emerged from academic and corporate research labs in the second half of the 1960s.
One of the first places where they gained some visibility was in the terminal of a computer-assisted learning terminal that came out in 1972 as part of the PLATO project.
Touch screens became widely used in kiosk and point of sale systems in banks and stores.
In 1983, the first touch screen computer, the HP-150, reached the market.
Introduction of advanced touch screen technologies leading to the commercialization of tablet PCs, PDAs, and touch-screen phones.
Resistive
Most widely used due to its simple structure
2 Types
1. Matrix (digital)
Striped electrodes on substrates such as glass or plastic face each other
2. Analogue
Transparent electrodes without any patterning facing each other
Low production costs
Resistive
Measurement of X & Y Coordinates:
Top sheet carries a voltage gradient by applying a voltage between the electrodes of top sheet
Bottom sheet serves as a slide in a linear potentiometer.
Surface Acoustic Wave
The waves propagate across the glass and are reflected back to the sensors.
When screen touched, a portion of the wave is reflected back to the sensors immediately.
The sensor is able to tell if the wave has been disturbed by a touch event at any instant, and can locate it accordingly.
Surface Acoustic Wave
How can the sensors tell?
Waves travel at the speed of sound
Speed of Sound = 343 m/s
Based on the time it takes for the wave to return to the source, the sensor can tell if it was disturbed or not.
If it was, based on the time it takes to get back to the source, the sensor can calculate the distance.
These calculations will generate (X,Y) coordinates
[attachment=38270]
History
Touch screens emerged from academic and corporate research labs in the second half of the 1960s.
One of the first places where they gained some visibility was in the terminal of a computer-assisted learning terminal that came out in 1972 as part of the PLATO project.
Touch screens became widely used in kiosk and point of sale systems in banks and stores.
In 1983, the first touch screen computer, the HP-150, reached the market.
Introduction of advanced touch screen technologies leading to the commercialization of tablet PCs, PDAs, and touch-screen phones.
Resistive
Most widely used due to its simple structure
2 Types
1. Matrix (digital)
Striped electrodes on substrates such as glass or plastic face each other
2. Analogue
Transparent electrodes without any patterning facing each other
Low production costs
Resistive
Measurement of X & Y Coordinates:
Top sheet carries a voltage gradient by applying a voltage between the electrodes of top sheet
Bottom sheet serves as a slide in a linear potentiometer.
Surface Acoustic Wave
The waves propagate across the glass and are reflected back to the sensors.
When screen touched, a portion of the wave is reflected back to the sensors immediately.
The sensor is able to tell if the wave has been disturbed by a touch event at any instant, and can locate it accordingly.
Surface Acoustic Wave
How can the sensors tell?
Waves travel at the speed of sound
Speed of Sound = 343 m/s
Based on the time it takes for the wave to return to the source, the sensor can tell if it was disturbed or not.
If it was, based on the time it takes to get back to the source, the sensor can calculate the distance.
These calculations will generate (X,Y) coordinates