Touch Screens Work

Although touch screen technology has been around for a number of decades, today we are experiencing a boom in the touch screen technology development industry. Beginning with the newly introduced iPhone, touch screen cell phones are available by just about every major cell phone manufacturer. But for those who wonder how the technology works, this article aims to answer those questions.

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 development of touch screen technology focuses on improving screen brightness, touch sensitivity and accuracy, and the elimination of misreading unintentional touches.

In the first system, the glass panel is overlaid with two metallic sheets. The first sheet is conductive and the second resistive. There are spacers between the sheets to keep them just slightly separated as well as a protective layer that severs only to keep the entire screen from being damaged. When the screen is on, both layers are charged with electrical currents.

This type of touch screen system works regardless of the medium used to touch the screen. Pressure from the user’s fingertips, stylus, or from being dropped all do the same thing and that is forcing the two sheets to touch each other. When this happens, the electrical current changes and the computer calculates where on the screen the touch was made. This is known as the resistive system.

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.

When it comes to these three types of touch screen systems, the surface acoustic is the most expensive but also allows for best quality. Without the need for a metallic sheet, it can allow 100% of the screens brightness to shine through. The resistive system, because it requires two sheets, allows only 75% and is the least expensive form of touch screen systems.