iPhone Touchscreen

Since its debut in 2007, the iPhone has become the one of the most well known smartphones in the world. One of the features that was unique to the iPhone when it was first released was ability to interpret touches from multiple locations on the touchscreen, also known as multi-touch. To explain how this type of touchscreen works, one first has to understand how touchscreens work in general.

In its most basic form, the iPhone touchscreen works by measuring changes in current. The screen is composed of the LCD display, a transparent conductive layer, a grid of nonconductive dots, a second conductive layer, and a protective transparent surface. When one touches the touchscreen, the upper conductive layer comes into contact with the lower layer at the location of the touch, causing a change in current in the area of the touch. By measuring the current on the screen, it can be the determined where the touch is occurring.

The difference between this type of screen and the iPhone is that the iPhone is able to detect multiple touches simultaneously. Typical touchscreens are unable to do this because they detect touches along specific axis’s or average screen wide touches. The iPhone works differently in that there is only one layer of conductive electrodes. Each of these electrodes is independent of the others, so that the system can identify multiple independent touches. This one layer of electrodes is the reason why one has to touch the screen with either their finger or another conductive surface. Your finger generates a current from the capacitative material, allowing the iPhone to determine where it has been touched.

Once a touch or touches have been detected by the iPhone, they are sent to the processing software which determines the features of each touch. This includes the size of the touch, whether movement was involved, number of touches, and location of the touch(es). Based on this information, the iPhone determines what kind of gesture was made. It sends this information to the running application which interprets it into an action in the program.