Multi-touch

n computing, multi-touch refers to a touch sensing surface's (trackpad or touchscreen) ability to recognize the presence of two or more points of contact with the surface. This plural-point awareness is often used to implement advanced functionality such as pinch to zoom or activating predefined programs. In an effort of disambiguation or marketing classification some companies further break down the various definitions of multi-touch. An example of this is 3M, defining multi-touch as a touch-screen's ability to register three or more distinct positions. The use of touchscreen technology to control electronic devices pre-dates multi-touch technology and the personal computer. Early synthesizer and electronic instrument builders like Hugh Le Caine and Bob Moog experimented with using touch-sensitive capacitance sensors to control the sounds made by their instruments.[2] IBM began building the first touch screens in the late 1960s, and, in 1972, Control Data released the PLATO IV computer, a terminal used for educational purposes that employed single-touch points in a 16x16 array as its user interface. The prototypes[3] of the x-y mutual capacitance multi-touch screens (left) developed at CERN One of the early implementations of mutual capacitance touchscreen technology was developed at CERN in 1977[4][5] based on their capacitance touch screens developed in 1972 by Danish electronics engineer Bent Stumpe. This t

chnology was used to develop a new type of human machine interface (HMI) for the control room of the Super Proton Synchrotron particle accelerator. In a handwritten note dated 11 March 1972, Stumpe presented his proposed solution – a capacitive touch screen with a fixed number of programmable buttons presented on a display. The screen was to consist of a set of capacitors etched into a film of copper on a sheet of glass, each capacitor being constructed so that a nearby flat conductor, such as the surface of a finger, would increase the capacity by a significant amount. The capacitors were to consist of fine lines etched in copper on a sheet of glass – fine enough (80 ?m) and sufficiently far apart (80 ?m) to be invisible (CERN Courier April 1974 p117). In the final device, a simple lacquer coating prevented the fingers from actually touching the capacitors. Multi-touch technology began in 1982, when the University of Toronto's Input Research Group developed the first human-input multi-touch system. The system used a frosted-glass panel with a camera placed behind the glass. When a finger or several fingers pressed on the glass, the camera would detect the action as one or more black spots on an otherwise white background, allowing it to be registered as an input. Since the size of a dot was dependent on pressure (how hard the person was pressing on the glass), the system was somewhat pressure-sensitive as well.