Multi touch

On touchscreen displays, multi-touch refers to the ability to simultaneously register three or more distinct positions of input touches. It is often used to describe other, more limited implementations, like Gesture-Enhanced Single-Touch or Dual-Touch.

Multi-touch has been implemented in several different ways, depending on the size and type of interface. Both touchtables and touch walls project an image through acrylic or glass, and then back-light the image with LEDs. When a finger or an object touches the surface, causing the light to scatter, the reflection is caught with sensors or cameras that send the data to software which dictates response to the touch, depending on the type of reflection measured. Touch surfaces can also be made pressure-sensitive by the addition of a pressure-sensitive coating that flexes differently depending on how firmly it is pressed, altering the reflection.Handheld technologies use a panel that carries an electrical charge. When a finger touches the screen, the touch disrupts the panel's electrical field. The disruption is registered and sent to the software, which then initiates a response to the gesture.

In the past few years, several companies have released products that use multitouch. In an attempt to make the expensive technology more accessible, hobbyists have also published methods of constructing DIY touchscreens.

Many companies in recent years have expanded into multitouch, with systems designed for everything from the casual user to multinational organizations.

Laptop manufacturers have begun to include multitouch trackpads on their laptops, as well as constructing tablet PCs that respond to touch input rather than traditional stylus input.

In the wake of the iPhone, several mobile phone manufacturers have begun to replace traditional push-button interfaces with multitouch interfaces on their handheld devices as well. So far, such innovations are mostly restricted to the higher-end smartphones used for web browsing and computing in addition to phone-based functions.

A few companies are focusing on large-scale surface computing rather than personal electronics, either large multitouch tables or wall surfaces. These systems carry a hefty price tag and are generally used by government organizations, museums, and companies as a means of information or exhibit display.

Apple Inc. lists "Multi-Touch" on their page of trademarks, however, this was only added some time after October 2007, and Apple was awarded a patent covering multitouch on 20 January 2009,. "Multi-Touch" is now considered a Genericized trademark.