Touch screen technology can be mysterious if you ever stop to wonder what really makes a screen recognize your finger, pen, or stylus. As technology advances, touch screens are becoming more popular because they make the user interface more exciting and intuitive for people new to modern tech gadgetry. There are three basic systems used in screens to recognize your touch and at the writing of this article, infrared technology is making its way as the fourth system as well as others in development for different scale products.
The first is a resistive system that uses a conductive and resistive metallic sheet to cover a glass panel. The two layers are held apart by spacers with electrical currents running through both layers when the screen is on. There is also a scratch protection layer that covers the metallic layer to keep the screen from being destroyed too easily. When the user touches the screen, the two layers are forced to touch each other at that spot. There is a change in the electrical field when the contact is made and the coordinates of the point of contact are fed to a computer which calculates where that is on the screen and in turn tells the operating system which determines what a touch on that particular spot means.
The capacitive system is built with a layer that holds an electrical charge right on top of the glass panel. When a finger touches the screen, some of the charge escapes into the finger. The decrease in charge is measured in circuits which are usually located at the corners of the screen. And from the relative change in charge at each corner the computer can calculate what the point of contact was with the finger that released some of the charge.
The surface acoustic wave system uses a pair of transducers along the sides of the glass plate. And reflectors are placed in the glass plate to reflect the electrical signal that is sent from one sending transducer to one receiving transducer. When a finger touches the screen, the electrical signal is disturbed and using two axes the computer can calculate the precise area of contact.
Because the surface acoustic system does not use a metallic plate, it allows 100 percent of light from the monitor through for perfect clarity. As opposed to the resistive system which transmits about 75 percent of the monitors light and the capacitive system which transmits about 90 percent for improved image quality over the resistive system.