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ROLL NO:47

MULTI TOUCH INTERACTION

OVERVIEWMulti touch IntroductionHistory of multi touchTypesGesturesApplicationsAdvantages Conclusion Referenses

MULTITOUCH?

“In computing, multi-touch refers to a touch sensing surface's (track pad or touchscreen) ability to recognize the presence of two or more points of contact with the surface.”

Introduction• Multi-touch technology presents a wide

range of new opportunities for interaction with graphical user interfaces, allowing expressive gestural control and fluid multi-user collaboration through relatively simple and inexpensive hardware and software configurations.

•Multi-touch technology dates back to 1982, when the University of Toronto developed the first finger pressure multi-touch.•In 1984 Bell Labs engineered a multi-touch screen that could manipulate images with more than one hand. •In1991 Wellner published a paper on his multi-touch “Digital Desk”, which supported multi-finger and pinching motions.

History of Multi Touch…

Types

a) Capacitive Touch Technologiesb) Resistive Touch Technologiesc) Optical Touch Technologiesd) Infrared Technologies

Capacitive Touch Screen Technology

A capacitive touch screen consists of a glass panel with a capacitive (charge storing) material coating its surface. Circuits located at corners of the screen measure the capacitance of a person touching the overlay.Eg:(fig:1)

Fig:1

Resistive Touch Screen Technology

Resistive touch screen technology consists of a glass panel that is coated with electrically conductive and resistive layers. The thin layers are separated by invisible separator dots. When operating, an electrical current moves through the screen. When pressure is applied to the screen the layers are pressed together, causing a change in the electrical current and a touch is registered. Eg:(fig:2)

Fig:2

Infrared

Infrared technology relies on the interruption of an infrared light grid in front of the display screen. The touch frame contains a row of infrared LEDs and photo transistors, each mounted on two opposite sides to create a grid of invisible infrared light. The frame assembly comprises printed wiring boards, on which the electronics are mounted and is concealed behind an infrared-transparent bezel.Eg:(fig:3)

Fig:3

Optical TouchOptical imaging solution is one of the more modern touch technologies.Since NextWindow's technology uses optical sensors to detect the touch point, the touch registers just before the physical touch on the screen. This means that users can apply zero or light touch to the screen to initiate a response, and any input device, such as a paintbrush, finger, pen, or stylus will work.

Multi-touch GesturesTapPanLong pressScrollTwo finger scrollFlickTwo finger tapPinch openPinch close

Applications• Our technique is force-sensitive, and provides

unprecedented resolution and scalability, allowing us to create sophisticated multi-point widgets for applications large enough to accommodate both hands and multiple users.

A New Approach Frustrated Total Internal Reflection (FTIR):• If another material touches that within

which the light is reflecting, the reflection is frustrated, causing the light to escape.

• This has been used in the past:• fingerprint imaging• early touch sensors (1970s!)• tactile sensors for robotic grips

Using FTIR for Touch Sensitivity• A clear acrylic sheet is used as the touch surface.– 16 inches x 12 inches in prototype

• Edges of surface lit by infra-red LEDs to produce total internal reflection.

• A video camera is mounted under the surface and facing it.• When the surface is touched, the light escapes and registers

on the camera.

Advantages to this Approach• High capture rate and resolution– 30 frames per second– 640x480

• True zero-force touch sensitivity• Inexpensive to construct• Scalable to much larger (even wall-sized!)

surfaces• Transparent: can be combined with rear-

projection display

In more recent work we focus on new multi-touch paradigms and interactions that combine both traditional 2D interaction and novel 3D interaction on a touch surface to form a new class of multi-touch systems, which we refer to as interscopic multi-touch surfaces (iMUTS). We discuss iMUTS-based user interfaces that support interaction with 2D content displayed in monoscopic mode and 3D content usually displayed stereoscopically.

Enhancement in Technology

• Touch screens are the interface for the 21st century.• Multi touch technique using FTIR is simple and easy to

implement.• It provides any resolution displays supported with high

graphics.• A drawback of the approach is that, being camera-

based, it requires a significant amount of space.

CONCLUSIONS

REFERENCES

1) Low-cost Multi-Touch Sensing through FTIR by Jefferson Y. Han.

2) Touch-Sensitive Tablet input.3) Pearson Education, 2003.4) Buxton, Bill. 2008. Multi-Touch Systems that I Have Known

and Loved.5)http://www.billbuxton.com/multitouchOverview.html6) http://www.technologyreview.com/Infotec