There are three commonly used types of touch screen technologies:
Resistive Capacitive Surface acoustic wave
Pos Touch Monitor
1. The resistive type uses a normal glass panel, that is covered by a resistive and a conductive metallic layer and a protective layer (scratch resistant) on top of all this. When you touch the screen, the two metallic layers are joined and the change in electrical field is detected. The circuit on the monitor then calculates the coordinates and transfer them to the touch screen software. Touch screen driver transfers the information about the coordinates to the OS, in a form of events similar to mouse clicks and drags.
This system registers a touch event as soon the surfaces are joined. This means, you can use a finger, a pen or any other item as input. This also makes it most vulnerable to physical damage by sharp objects. The metallic layers only transmit about 75% of the light from the monitor, making its display clarity the lowest of the three.
2. With the capacitive type, a layer storing electrical charge, is placed on the monitor glass. When you touch the layer, a small amount of the electrical charge is transferred to you, decreasing the charge on the layer. Sensors, located at the corners of the monitor, detect a change in electrical charge levels and transfer the information to the touch screen software to process.
The biggest advantage of capacitive type over resistive is that it has 90% light throughput, while the resistive. This gives the capacitive touch screen monitors a much clearer picture. Since this type uses electric charge to detect a touch event, you must use a conductive input, such as a finger.
3. The surface acoustic wave type uses two transducers and a reflector, all placed on the monitor glass plate. One transducer is sending electrical signals to the other and the reflector reflects this signal.
The receiving transducer is capable of detecting and locating any touch event. Since this type has no metallic layers placed on the display surface, they have 100% light throughput, and therefore the most clear picture. Similar to resistive, this type detects touch events by almost any object, except very small or hard items, such as a pen.
These are just the most commonly used types. There are many other touchscreen technologies out there, such as strain gauge configuration (from 1960's) or relatively-modern optical imaging technology. And new ones are being developed as we speak.
Touchscreen technology has seen a lot of progress during the last few years.
The iPhone has made a revolution in hardware as well as touch screen software. And surveys are showing significant rise in demand for touchscreens computers, for users of laptops, as well as desktop computers.
Perhaps, the time to put the mouse away, is finally coming.