a presentation report on multi touch technology.

1. Represented by:
Debasnata Pati
*

2. In computing, multi-touch refers to the ability of a
surface (a track pad or touchscreen) to recognize the
presence of more than one or more than two points
of contact with the surface.
OR
A surface which is able to detect / recognize more
than one or two points of touch.

3. What Is Multi-Touch
Technology??
Ans:
Multi-touch technology allows a touchscreen to
sense input from two or more points of contact at
the same time.
This allows us to use multiple finger gestures to
do things like pinch the screen to zoom in, or
spread the screen to zoom out.

4. THE TECHNOLOGIES USED
IN MULTI TOUCH ARE
 FTIR ( Frustrated Total Internal
Reflection)
 DI ( Diffused Illumination )
 LLP ( Laser Light Plane )
 DSI ( Diffused Surface Illumination)
 LED-LP (LED Light Plane)

5. FTIR( Frustrated Total Internal
Reflection)
 FTIR stands for Frustrated Total Internal Reflection,
which is mostly used method in Multi-touch
technology.
It is based on very simple principles of the technology:
 A surface of higher-index medium (acrylic, glass,
plastic) is used and Infra Red light is passed into the
side of this surface which trapped inside this medium
by the refraction index of the material.

6. FTIR (cont.)
 When the light ray is travelling inside a higher-index medium
Total Internal Reflection occurs and passes a surface boundary
into a lower-index medium . On a finger touch the surface of
the pane, causes the light to scatter downwards where it is picked
up by an IR camera. A camera on the opposite side from the user
with visible light filter registers the scattered light. And a
projector projects the image on to the projection screen.

7. DI( Diffused Illumination)
It comes on two main forms:
1. Front Diffused Illumination
2. Rear Diffused Illumination

8. FRONT DIFFUSED ILLUMINATION:
Infrared light is shined at the screen from the
above of touch surface. A diffuser is placed on top
or on bottom the surface. When an object touches
the surface, a shadow is created in the position of
the object. The camera senses the shadow.

9. Advantages Disadvantages
 No need for a compliant
surface, just an
diffuser/projection surface on
top/bottom.
 No LED frame required.
 Can track fingers and
hovering.
 An enclosed box is not
required
 Cannot track objects and
fiducials.
 Difficult to get even
illumination.
 Greater chance of false
blobs.
 Nor as reliable ( relies heavily
on ambient lighting
environment)

10. Rear Diffused Illumination:
 Infrared light is shined at the screen from below the
touch surface. A diffuser is placed on top or on bottom of
the touch 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 the camera.

11. Advantages Disadvantages
 No need for a compliant
surface, just an
diffuser/projection surface on
top/bottom.
 Can use any transparent
material like glass ( not just
acrylic).
 No LED frame required
 Difficult to get in illumination.
 Blobs have lower contrast (
harder to pick up by
software).

12. LLP ( Laser Light Plane)
Infrared light from single or multiple lasers shine
just above the surface. When a finger or object hits
the light plane, the object lights up and is
displayed by using a projector connected to a
computer pointed towards the projection material.

13. Advantages Disadvantages
 No compliment surface (
silicone).
 Can use any transparent
material like glass ( not just
acrylic )
 No LED frame required.
 An enclosed box is not
required.
 Simple setup.
 Cannot track traditional
objects and fiducials.
 Not truly pressure sensitive (
since light intensity doesn’t
change with pressure.

14. DSI ( Diffused Surface Illumination )
 DSI uses a special acrylic to distribute the IR across the surface .In this
the FTIR setup is used but the LED frame is switched to an acrylic.
This acrylic uses small particles that are inside the material, acting as
thousand of small mirrors. When you shine an IR light into the edges,
the light spread to the surface of acrylic & is seen by a camera below
the surface. An image is displayed by the projector.

15. Advantages Disadvantages
 No compliant surface
(silicone).
 Can easily switch back and
forth between DI ( DSI ) and
FTIR.
 Can detect objects, hovering,
and fiducials.
 Is pressure sensitive.
 Endlighten Acrylic costs more
than than regular acrylic ( but
the some of the cost can be
made up since no IR
illuminators are needed )
 Blobs have the lower
contrast ( harder to pick up
by software ) than FTIR and
LLP

16. LED-LP ( LED Light plane )
 The 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.

17. Advantages Of Multi-Touch
 Multi touch based on FTIR is a simple and inexpensive
technique.
 Scalable technique that enables high-resolution graphics.
 It requires true touch image information at high spatial and
temporal resolutions.

18. APPLICATIONS
• A multi touch display can be used in
• Personal computers, Laptops, Tabletops,
Graphics Tablets.
• It supports both LCD and CRT monitors.
• Telephone, Watches, Mobile Phone.
• Advanced multi touch Gaming with high
graphics support.
• An enhanced multimedia experience including
audio, video and photo sharing.

19. FUTURE USES
You can install touchscreens in places
where it simply would be impractical to
put a camera-based system. Taxicabs
and airplanes spring to mind.
You can carry a touchscreen in your
pocket and use it in a variety of settings
as part of a mobile device.

20.  Touch screens are the interface for 21st century.
 Touch screens address the conflicting demands for
smaller portable electronics with larger displays, by
eliminating traditional buttons without sacrificing
screen size.
 Multi touch technique using FTIR is simple and easy
to implement.
 It provides any resolution displays supported with
high graphics.
 A drawback of approach is that, being camera
based, it requires a significant amount of space.

21. THANK
YOU