A touchscreen is an electronic visual display that can detect the presence and location of a touch within the display area. The term generally refers to touching the display of the device with a finger or hand. Touchscreens can also sense other passive objects, such as a stylus.
These are touch screen technology in use today by different manufacturer:
1, Wire Resistive - composed of several layers, the most important of which are two thin, electrically conductive layers separated by a narrow gap. When a finger, presses down on a point on the panel's outer surface the two metallic layers become connected at that point: the panel then behaves as a pair of voltage dividers with connected outputs.
2. Surface acoustic wave - uses ultrasonic waves that pass over the touchscreen panel. When the panel is touched, a portion of the wave is absorbed.
3. Capacitive - consists of an insulator such as glass, coated with a transparent conductor such as indium tin oxide As the human body is also a conductor, touching the surface of the screen results in a distortion of the screen's electrostatic field, measurable as a change in capacitance.
4. Infrared-uses an array of X-Y infrared LED and photodetector pairs around the edges of the screen to detect a disruption in the pattern of LED beams.
5. Optical imaging - in which two or more image sensors are placed around the edges (mostly the corners) of the screen. Infrared back lights are placed in the camera's field of view on the other side of the screen.
6. Dispersive signal technology - uses sensors to detect the mechanical energy in the glass that occurs due to a touch. Complex algorithms then interpret this information and provide the actual location of the touch.
7. Acoustic pulse recognition - uses piezoelectric transducers located at various positions around the screen to turn the mechanical energy of a touch (vibration) into an electronic signal.The screen hardware then uses an algorithm to determine the location of the touch based on the transducer signals.