Multi-touch technology for capacitive touchscreen and capacitive touch display

In computing, multi-touch is technology that enables a surface (a touchpad or touchscreen) to recognize the presence of more than one point of contact with the surface at the same time. The origins of multitouch began at CERN, MIT, University of Toronto, Carnegie Mellon University and Bell Labs in the 1970s. CERN started using multi-touch screens as early as 1976 for the controls of the Super Proton Synchrotron. 

Capacitive multi-touch displays were popularized by Apple's iPhone in 2007. Plural-point awareness may be used to implement additional functionality, such as pinch to zoom or to activate certain subroutines attached to predefined gestures.

Multi-touch is commonly implemented using capacitive sensing technology in mobile devices and smart devices. A capacitive touchscreen typically consists of a capacitive touch sensor, application-specific integrated circuit (ASIC) controller and digital signal processor (DSP) fabricated from CMOS (complementary metal–oxide–semiconductor) technology. A more recent alternative approach is optical touch technology, based on image sensor technology.

Multi-touch has been implemented in several different ways, depending on the size and type of interface. The most popular form are mobile devices, tablets, touchtables and walls. Both touchtables and touch walls project an image through acrylic or glass, and then back-light the image with LEDs.

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 as a computer event (gesture) and may be sent to the software, which may then initiate a response to the gesture event.

Capacitive

Capacitive technologies include:

• Surface Capacitive Technology or Near Field Imaging (NFI)
• Projected Capacitive Touch (PCT)
  • Mutual capacitance
  • Self-capacitance
• In-cell Capacitive