Multi touch is unlikely to be alien to you; every pinch, swipe, tap, long press and flick on a touch screen is essentially a multi touch gesture.
It’s not only touch screens that display this behavior; many laptop track pads support multi touch.
The technology has seen several types of implementations since the 60’s. In its most advanced implementation, multi touch becomes multi user in video walls and tabletops that let multiple users interact with the same device.
The most common usage of multi touch is in capacitive touch screens, as seen on smartphones and tablets.
Different types of multi touch technologies
Multi touch technology can be divided into two main types:
- Overlay based – Capacitive touch screens work according to this principle, where the sensors responsible for the multi touch features are embedded into the screen.
- Perimeter based– Infrared, Surface Acoustic Wave, Optical, as well as ShadowSense touch screens work on this principle, where the sensors are located on the perimeter of the screen.
The software stack is also important for detecting multi touch. The process of converting an input on the screen to a multi touch gesture has a number of stages:
- Input hardware layer– Here the input data is gathered in the form of either video or electric signals.
- Hardware abstraction layer– The input data is processed to generate image co-ordinates (e.g. imprint of the finger).
- Transformation layer– This layer calibrates the touch screen so that the image data (the imprint) can be converted into screen co-ordinates.
- Interpretation layer– Gesture recognition happens in this layer. Every gesture has a starting point, ending point and dynamic motion between the two points. A multi touch system recognizes a multitude of gestures.
- Widget layer– This layer generates the output of the gesture. All that pinching and zooming happens in this layer.
In the case of Baanto’s ShadowSense touch screen technology, shadows cast by an object on to sensors embedded in the bezel are used to detect multi touch gestures on our touch screen panels.
Up to 10 touch points are supported, as well as natural gestures like flicks, swipes and pinches. ShadowSense delivers stable and repeatable performance with no ghosting and or lost touch points.
One unique feature of ShadowSense touch screens is that their performance remains fluid even as the number of touch points increases, since the technology works independently of the host CPU.
Implementations of multi touch technologies
Over the years, as multi touch technologies have matured, the implementations have seen multiple form factors. Apart from phones and tablets multi touch screens can be seen in:
- Multi touch frames– can be mated with ordinary monitors to turn the user interface into a touch screen.
- Multi touch tables– Tabletop PCs, like Microsoft SurfaceTM fall within this category.
- Multi touch walls– are often used in public spaces to create interactive multi person experiences.
- Multi touch monitors– typically are found in laptops that come installed with touch supported operating systems like Windows 8