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It tells everything about Multi touch interacion starting with what is touch...
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MULTI TOUCH
INTERACTION
Parvika Singhal (101103071)
What is Multi-Touch?
Ability of a surface to recognize the presence of
more than one or more than two points of contact
with the surface
India’s First Laser Multi-touch Table is provided by
Team Zugard
The first devices to support Multi-touch were:
Mitsubishi Diamond Touch (2001)
Apple iPhone (January 9, 2007)
Microsoft PixelSense (May 29, 2007)
NORTD labs Open Source system CUBIT (multi-
touch) (2007)
ELAN eFinger
MULTI TOUCH DEVICES
Multi-Touch Interaction
Human interaction with a computer where
more than one finger can be used to provide
input at a time
Benefits of multi touch interaction:
Natural
Simultaneous multi user input
History
Illustration
Touch screen Technologies
Resistive
Capacitive
Surface Acoustic Wave
Infrared
Optical
Resistive Touch screen
Consist of a glass
or acrylic panel that
is coated with
electrically
conductive and
resistive layers
made with indium
tin oxide (ITO)
The thin layers are
separated by
invisible spacers.
Projected-Capacitive Touch
screen
During a touch, capacitance forms between
the finger and the sensor grid. The
embedded serial controller in the touch
screen calculates touch location
coordinates and transmits them to the
computer for processing.
Surface Acoustic Wave Touch
Two transducers placed in corners & two receivers in the opposite corners
Sound wave travels parallel to the edges of the glass. When the sound wave encounters the reflectors, the wave is transmitted from the transducers to the receivers.
Touch point is detected when a drop in the amplitude of the sound wave occurs.
Infrared Touch screen
Uses an array of X-Y infrared LED and photo detector pairs around the edges of the screen to detect a disruption in the pattern of LED beams.
LED beams cross each other which helps the sensors pick up the exact location of the touch.
Optical Touch screen
Infrared back lights
are placed in the
camera's field of
view on the other
side of the screen.
Touch shows up as
a shadow and
each pair of
cameras can then
be pinpointed to
locate the touch
Techniques
FTIR : Frustrated Total Internal
Reflection
DI : Diffused Illumination
DSI : Diffused Surface Illumination
LED LP : Led Laser Plane
LLP : Laser Light Plane
PRINCIPLE OF WORKING
Mesh of IR is generated on screen
Frustration is created on the surface if touched
Detected by the camera
Blobs (bright luminescent object) are created and sent to tracker
Tracker communicates with application
FTIR
Infrared light is placed and directed into the edges of an acrylic panel. The light is trapped within the acrylic by “total internal
reflection”. When a finger touches the acrylic surface, the infrared light is “frustrated” causing the light to escape internal
reflection and scatter downwards where it is seen by an infrared camera.
Diffused Illumination
Infrared light is shined at the screen below/above (Rear/Front DI) surface. When an object touches the surface it reflects more light than the diffuser or objects in the background; the extra light is sensed by a camera.
Diffused Surface Illumination
When a finger or object touches the diffuser, it lights up from the infrared light escaping from within and is seen by a camera below the surface.
Laser Light Plane (LLP)
Infrared light from single or multiple lasers shine above the surface. The laser plane of light is about 1mm thick and positioned very close to the touch surface. When a finger or object hits the light plane, the object lights up and is seen by an infrared camera below the surface.
Led Light Plane (LP)
The narrow angle LEDs are positioned just above the touch surface in order to create a plane of light. When a finger or object touches the light plane, it is illuminated and seen by a infrared camera below the surface.
Real Images
FTIR
DI
DSI
LLP
Led LP
Programming for the MT
CCV (Community Core Vision) is an open source C++ software package that contains code to analyze data from a camera, detect IR blobs from within the data, interpret that IR blob data, and generate TUIO events for the application to interpret.
Since most operating systems only expect one mouse click at any single time, a new event and protocol must be used to interpret any number of touches, the TUIO protocol.
TUIO (Tangible User Interface Object) : A protocol used for communicating the position, size, and relative velocity of blobs