This document discusses multi-touch interaction and technologies. It describes how multi-touch allows for multiple simultaneous points of input detection on a touch surface. Various touch screen technologies are covered, including resistive, capacitive, surface acoustic wave, infrared, and optical. It also discusses techniques for optical touch sensing including FTIR, DI, DSI, LLP and LED LP. Programming for multi-touch involves using open-source libraries like CCV and TUIO protocols.

1. MULTI TOUCH
INTERACTION
Parvika Singhal (101103071)

2. 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

3. MULTI TOUCH DEVICES

4. 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

5. History

6. Illustration

7. Touch screen Technologies
 Resistive
 Capacitive
 Surface Acoustic Wave
 Infrared
 Optical

8. 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.

9. 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.

10. 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.

11. Infrared Touch screen
 Uses an array of X-Y
infrared LED and phot
o 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.

12. 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

13. Techniques
 FTIR : Frustrated Total Internal
Reflection
 DI : Diffused Illumination
 DSI : Diffused Surface Illumination
 LED LP : Led Laser Plane
 LLP : Laser Light Plane

14. 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

15. 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.

16. 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.

17. 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.

18. 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.

19. 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.

20. Real Images
 FTIR

21.  DI

22.  DSI

23.  LLP

24.  Led LP

25. 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