Implementations
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.
Types
- Capacitive Technologies
- Surface Capacitive Technology or Near Field Imaging (NFI)
- Projected Capacitive Touch (PST)
- Mutual capacitance
- Self-capacitance
- In-cell: Capacitive
- Resistive Technologies
- Analog Resistive
- Digital Resistive or In-Cell: Resistive
- Optical Technologies
- Optical Imaging or Infrared technology
- Rear Diffused Illumination (DI)
- Infrared Grid Technology (opto-matrix) or Digital Waveguide Touch (DWT)™ or Infrared Optical Waveguide
- Frustrated Total Internal Reflection (FTIR)
- Diffused Surface Illumination (DSI)
- Laser Light Plane (LLP)
- In-Cell: Optical
- Wave Technologies
- Surface Acoustic Wave (SAW)
- Bending Wave Touch (BWT)
- Dispersive Signal Touch (DST)
- Acoustic Pulse Recognition (APR)
- Force-Sensing Touch Technology
The optical touch technology functions 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 multi-touch. In an attempt to make the expensive technology more accessible, hobbyists have also published methods of constructing DIY touchscreens.
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