MULTI TOUCH

MULTI TOUCH

A SEMINAR REPORT

Submitted by

ALIKUTTY K A

in partial fulfillment for the award of the degree

of

BACHELOR OF TECHNOLOGY

in

COMPUTER SCIENCE & ENGINEERING

SCHOOL OF ENGINEERING

COCHIN UNIVERSITY OF SCIENCE & TECHNOLOGY,

KOCHI-682022

NOVEMBER 2008

DIVISION OF COMPUTER ENGINEERING

SCHOOL OF ENGINEERING

COCHIN UNIVERSITY OF SCIENCE AND TECHNOLOGY

KOCHI-682022

CertificateCertified that this is a bonafide record of the seminar entitled

“MULTI TOUCH”

done by the following student

ALIKUTTY K A

of the VIIth

semester,Computer Science and Engineering in the year 2008 in

partial fulfillment of the requirements to the award of Degree of Bachelor of

Technology in Computer Science and Engineering of Cochin University of

Science and Technology.

Ms.Shekha Chenthara Dr.David Peter S

Seminar Guide Head of the Department

Date:

ACKNOWLEDGEMENT

I thank my seminar guide Ms Shekha Chenthara , Lecturer, CUSAT, for her

proper guidance, and valuable suggestions. I am indebted to Mr. David Peter, the

HOD, Computer Science division & other faculty members for giving me an

opportunity to learn and do this seminar. If not for the above mentioned people my

seminar would never have been completed successfully. I once again extend my

sincere thanks to all of them.

ALIKUTTY K A

ABSTRACT

Multi-touch technology is an advanced human-computer interaction

technique that recogonises multiple touch points and also includes the

hardware devices that implement it, which allow users to compute

without conventional input devices . Multi-touch consists of a touch

screen (screen, table, wall, etc.) or touchpad, as well as a software that

recognizes multiple simultaneous touch points, as opposed to the

standard touchscreen which recognizes only one touch point at a time.

Multi touch using Frustrated Total Internal Reflection is a simple,

inexpensive, and scalable technique for enabling high-resolution multi-

touch sensing on rear-projected interactive surfaces. Different

applications for multi-touch interfaces both exist and are being proposed.

Some uses are individualistic eg iPhone, iPod touch, MacBook Pro,

MacBook Air. The use of multi-touch technology is expected to rapidly

become common place.

i

TABLE OF CONTENTS

CHAPTER NO TITLE PAGE NO

LIST OF FIGURES ii

LIST OF SYMBOLS,ABBREVIATIONS AND iii

NOMENCLATURES

1. INTRODUCTION 1

1.1 TOUCH SCREEN 1

1.1.1 TECHNOLOGIES 2

1.1.2 DEVELOPMENT 4

2. MULTI TOUCH 5

2.1 HISTORY 5

2.2 RECENT DEVELOPMENTS 6

2.3 FUTURE 7

3. FTIR 8

3.1 PRINCIPLES 8

3.2 DESIGN

3.3.1 REQUIREMENTS 10

3.3.1.1 HARDWARE 10

3.3.1.2 SOFTWARE 11

3.4 WORKING 13

3.5 ADVANTAGES 15

3.6 APPLICATIONS 16

4 CONCLUSION 17

5 APPENDICES 18

5.1 APPENDIX I 18

6 REFERENCES 20

ii

LIST OF FIGURES

FIG NO DESCRIPTION PAGE NO

3.1 Total Internal Reflection 9

3.2 Acrylic with led’s at its edges 11

3.3 IR rays obtained on a camera 12

3.4 Frustrated Total Internal Reflection 13

3.5(a) IR view of a touch 14

3.5(b) Pixel Positions located on the screen 14

5.1(a) Prototype setup 18

5.1(b) Video output w/o diffuser 18

5.2 Photo sharing and multimedia 18

5.3 Wonders of multi touch-transfering music between Ipods 19

5.4 A roadside wall at Helsinki 19

iii

LIST OF SYMBOLS,ABBREVIATIONS AND NOMENCLATURES

NO ABBREVIATION EXPANSION

1 FTIR Frustrated Total Internal Reflection

2 TIR Total Internal Reflection

3 IR Infra Red

4 LED Light Emitting Diode

5 PP Perceptive Pixel

6 SAW Surface Acoustic Wave

7 PDA Personal Digital Assistance

8 MS Microsoft Surface

9 FW Finger Works

10 API Application Interface

11 LCD Liquid Crystal Display

12 CRT Cathode Ray Tube

Multi Touch

Division Of Computer Science ,SOE,CUSAT 1

1.INTRODUCTION

1.1 TOUCH SCREEN

A touchscreen is a display which can detect the presence and location of a

touch within the display area. The term generally refers to touch or contact to the

display of the device by a finger or hand. Touchscreens can also sense other passive

objects, such as a stylus. However, if the object sensed is active, as with a light pen,

the term touchscreen is generally not applicable. The thumb rule is: if you can interact

with the display using your finger, it is likely a touchscreen - even if you are using a

stylus or some other object.

Up until recently, most touchscreens could only sense one point of contact at a time,

and few have had the capability to sense how hard one is touching. This is starting to

change with the emergence of multi-touch technology - a technology that was first

seen in the early 1980s, but which is now appearing in commercially available

systems.

The touchscreen has two main attributes. First, it enables you to interact with what is

displayed directly on the screen, where it is displayed, rather than indirectly with a

mouse or a touchpad. Secondly, it lets one do so without requiring any intermediate

device, again, such as a stylus that needs to be held in the hand. Such displays can be

attached to computers or, as terminals, to networks. They also play a prominent role in

the design of digital appliances such as the personal digital assistant , satellite

navigation devices and mobile phone

1.1.1 TECHNOLOGIES

There are a number of types of touchscreen technology

Resistive

A resistive touchscreen panel is composed of several layers. The most important are

two thin metallic electrically conductive and resistive layers separated by thin space.

When some object touches this kind of touch panel, the layers are connected at certain

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point; the panel then electrically acts similar to two voltage dividers with connected

outputs. This causes a change in the electrical current which is registered as a touch

event and sent to the controller for processing.

Surface acoustic wave

SAW technology uses ultrasonic waves that pass over the touchscreen panel. When

the panel is touched, a portion of the wave is absorbed. This change in the ultrasonic

waves registers the position of the touch event and sends this information to the

controller for processing. Surface wave touchscreen panels can be damaged by

outside elements. Contaminants on the surface can also interfere with the functionality

of the touchscreen.

Capacitive

A capacitive touchscreen panel is coated with a material, typically indium tin oxide

that conducts a continuous electrical current across the sensor. The sensor therefore

exhibits a precisely controlled field of stored electrons in both the horizontal and

vertical axes - it achieves capacitance. The human body is also an electrical device

which has stored electrons and therefore also exhibits capacitance. When the sensor's

'normal' capacitance field (its reference state) is altered by another capacitance field,

i.e., someone's finger, electronic circuits located at each corner of the panel measure

the resultant 'distortion' in the sine wave characteristics of the reference field and send

the information about the event to the controller for mathematical processing.

Capacitive sensors can either be touched with a bare finger or with a conductive

device being held by a bare hand. Capacitive touchscreens are not affected by outside

elements and have high clarity. The Apple iPhone is an example of a product that uses

capacitance touchscreen technology.

Infrared

An IR touchscreen panel employs one of two very different methods. One method

uses thermal induced changes of the surface resistance. This method is sometimes

slow and requires warm hands. Another method is an array of vertical and horizontal

IR sensors that detect the interruption of a modulated light beam near the surface of

the screen.

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Optical imaging

A relatively-modern development in touchscreen technology, two or more image

sensors are placed around the edges (mostly the corners) of the screen. Infrared

backlights are placed in the camera's field of view on the other sides of the screen. A

touch shows up as a shadow and each pair of cameras can then be triangulated to

locate the touch. This technology is growing in popularity, due to its scalability,

versatility, and affordability, especially for larger units.

Dispersive signal technology

Introduced in 2002, this system uses sensors to detect the mechanical energy in the

glass that occur due to a touch. Complex algorithms then interpret this information

and provide the actual location of the touch. The technology claims to be unaffected

by dust and other outside elements, including scratches. Since there is no need for

additional elements on screen, it also claims to provide excellent optical clarity. Also,

since mechanical vibrations are used to detect a touch event, any object can be used to

generate these events, including fingers and stylus. A downside is that after the initial

touch the system cannot detect a motionless finger.

1.1.2 DEVELOPMENT

Virtually all of the significant touchscreen technology patents were filed during the

1970s and 1980s and have expired. Touchscreen component manufacturing and

product design are no longer encumbered by royalties or legalities with regard to

patents and the manufacturing of touchscreen-enabled displays on all kinds of devices

is widespread.

The development of multipoint touchscreens facilitated the tracking of more than one

finger on the screen, thus operations that require more than one finger are possible.

These devices also allow multiple users to interact with the touchscreen

simultaneously.

With the growing acceptance of many kinds of products with an integral touchscreen

interface the marginal cost of touchscreen technology is routinely absorbed into the

products that incorporate it and is effectively eliminated. As typically occurs with any

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technology, touchscreen hardware and software has sufficiently matured and been

perfected over more than three decades to the point where its reliability is

unassailable. As such, touchscreen displays are found today in airplanes, automobiles,

gaming consoles, machine control systems, appliances and handheld display devices

of every kind. The ability to accurately point on the screen itself is taking yet another

step with the emerging graphics tablet/screen hybrids.

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2.MULTI TOUCH

Multi-touch is a human-computer interaction technique and the hardware devices that

implement it, which allow users to compute without conventional input devices e.g.,

mouse, keyboard. Multi-touch consists of a touch screen like screen, table, wall or

touchpad, as well as software that recognizes multiple simultaneous touch points, as

opposed to the standard touchscreen i.e. computer touchpad, ATM, which recognizes

only one touch point. This effect is achieved through a variety of means, including but

not limited to: heat, finger pressure, high capture rate cameras, infrared light, optic

capture, tuned electromagnetic induction and shadow capture.

2.1 HISTORY

Multi-touch technology dates back to 1982, when the University of Toronto

developed the first finger pressure multi-touch display. The same year, Bell Labs at

Murray Hill published what is believed to be the first paper discussing touch-screen

based interfaces.

Bell Labs

In 1984 Bell Labs engineered a multi-touch screen that could manipulate images with

more than one hand. The group at the University of Toronto stopped working on

hardware and moved on to software and interfaces, expecting that they would have

access to the Bell Labs work.

A breakthrough occurred in 1991, when Pierre Wellner published a paper on his

multi-touch “Digital Desk”, which supported multi-finger and pinching motions.

Fingerworks

In 1998, FW, a Newark-based company run by University of Delaware academics

John Elias and Wayne Westerman, produced a line of multi-touch products including

the iGesture Pad and the TouchStream keyboard. Westerman published a dissertation

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in 1999 on the subject. In 2005, after years of maintaining a niche line of keyboards

and touchpads, Fingerworks was acquired by Apple Computer.

2.2 RECENT DEVELOPMENTS

Various companies expanded upon these discoveries in the beginning of the twenty-

first century. Mainstream exposure to multi-touch technology occurred in the year

2007, when Apple unveiled the iPhone and Microsoft debuted surface computing. The

iPhone in particular has spawned a wave of interest in multi-touch computing, since it

permits greatly increased user interaction on a small scale. More robust and

customizable multi-touch and gesture-based solutions are beginning to become

available, among them TrueTouch, created by Cypress Semiconductor. The following

is a compilation of notable uses of multi-touch technology in recent years.

Microsoft Surface

In 2001 Steve Bathiche and Andy Wilson of Microsoft began work on an idea for an

interactive table that mixes both physical and virtual worlds. Research and

Development expanded rapidly in 2004, once the idea caught the attention of

Microsoft Chairman Bill Gates. In 2007 Microsoft introduced MS, a functional multi-

touch table-top computer based on a standard PC platform including an Intel Core 2

Duo processor, Windows Vista, and 2 GB of RAM

Perceptive Pixel

PP is a company founded by New York University consulting research scientist

Jefferson Y. Han that creates wall displays and tables that can accommodate up to 20

fingers. Han introduced the FTIR technique to multi touch screens. The displays use

light emitting diodes along with infrared light to determine the point of contact. Han

envisions large collaborative spaces that will allow multiple users to work and

interact. PP’s technology is currently being utilized, in the form of the Multi-Touch

Collaboration Wall, by CNN and an unspecified government contractor everyday

programs with ease and most importantly more than one user can operate the system

at any given time.

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Apple iPhone, iPod touch, MacBook Air, and MacBook Pro

In 2005, Apple acquired Fingerworks. In 2007 they introduced the iPhone, marking

the first time multi-touch technology was used on a phone. The iPhone includes such

components as a web browser, music player, video player, and a cell phone without

the use of a hard keypad or stylus.

Following the release of the iPhone, Apple also expanded its use of multi-touch

computing with the new iPod Touch, as well as the new MacBook Air. Multi-touch

was later added to the 2008 MacBook Pro line in the form of a trackpad. Apple is

currently in the process of trying to patent its “Multi-touch” technology and to

trademark the term "multi-touch".

2.3 FUTURE

The use of multi-touch technology is expected to rapidly become common place. For

example, touch screen telephones are expected to increase from 200,000 shipped in

2006, to 21 million in 2012. Developers of the technology have suggested a variety of

ways that multi-touch can be used including:

Enhanced dining experience

Concierge service

Governmental use

Concept mapping

Collaboration and instruction on Interactive Whiteboards

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3.FRUSTRATED TOTAL INTERNAL REFLECTION

3.1 PRINCIPLES

Total internal reflection is an optical phenomenon that occurs when a ray of light

strikes a medium boundary at an angle larger than the critical angle with respect to

the normal to the surface. If the refractive index is lower on the other side of the

boundary no light can pass through, so effectively all of the light is reflected. The

critical angle is the angle of incidence above which the total internal reflection occurs.

When light crosses a boundary between materials with different refractive indices, the

light beam will be partially refracted at the boundary surface, and partially reflected.

However, if the angle of incidence is greater (i.e. the ray is closer to being parallel to

the boundary) than the critical angle — the angle of incidence at which light is

refracted such that it travels along the boundary — then the light will stop crossing

the boundary altogether and instead be totally reflected back internally. This can only

occur where light travels from a medium with a higher refractive index to one with a

lower refractive index. For example, it will occur when passing from glass to air, but

not when passing from air to glass.

The critical angle is the angle of incidence above which total internal reflection

occurs. The angle of incidence is measured with respect to the normal at the refractive

boundary. The critical angle is given by:

where n2 is the refractive index of the less dense medium, and n1 is the refractive

index of the denser medium.

Multi Touch


Fig 3.1 Total Internal Reflection

An important side effect of total internal reflection is the propagation of an evanescent

wave across the boundary surface. Essentially, even though the entire incident wave is

reflected back into the originating medium, there is some penetration into the second

medium at the boundary. Additionally, the evanescent wave appears to travel along

the boundary between the two materials. This wave can lead to a phenomenon known

as frustrated total internal reflection.

Under "ordinary conditions" it is true that the creation of an evanescent wave does not

affect the conservation of energy, i.e. the evanescent wave transmits zero net energy.

However, if a third medium with a higher refractive index than the second medium is

placed within less than several wavelengths distance from the interface between the

first medium and the second medium, the evanescent wave will be different from the

one under "ordinary conditions" and it will pass energy across the second into the

third medium.

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3.2 DESIGN

3.2.1 REQUIREMENTS

Multi touch is designed using the FTIR technology. FTIR describes the internal

reflection of light .It is force-sensitive, and provides unprecedented resolution and

scalability .Large enough to accommodate both hands and multiple users.This

phenomenon is also used in fingerprint and robot sensors.Allows us to create

sophisticated multi-point widgets for applications

3.2.1.1 HARDWARE

The basic design has a hardware and software part. Hardware requires basically IR

led’s,acrylic,camera,projector and a computer. Infra red light has a higher wavelength

than that of visible light .Therefore it has more intensity and will be felt everywhere

inside the denser medium. Acrylic is the denser medium .It is a synthetic fiber having

half the density of glass.An infra red camera or a webcam is used to catch IR light . A

IR block filter of the camera has to be removed since it blocks IR light. It also consists

of a projector and a computer. The object has to be projected on top of the acrylic

from a computer . Thus acrylic is a virtual display. The IR LED’s about 10-20 are

arranged on both sides of the acrylic along its edges .The camera below the acrylic

and the projector located behind to acrylic.

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Fig 3.2 Acrylic with led’s at its edges

3.2.1.2 SOFTWARE

Computer applications are necessary to communicate between a multi touch display

and a computer.These applications can be developed within several languages /

programming environments.For example: Processing (P5), Flash, C, C++, Java and

others.

Because of the usability of certain API’s and the relatively simple visualisation

possibilities, P5 or Flash 9, in combination with Actionscript 3.0 will make a great

combination .

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Fig 3.3 IR rays obtained on a camera

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3.4 WORKING

FTIR describes the internal reflection of light, inside a certain material. In our case, it

will be infrared light, that internally reflects inside is a piece of acrylic, also known as

plexiglas.This way, infrared light is beamed inside the acrylic and reflects internally.In

a simple way, you can say that, IR-light bounces inside the acrylic, from one side to

another.As soon as a finger touches the acrylic surface, the internal reflection of the

IR-light, is interrupted.The infrared light scatters on the finger tips.Infrared light is

invisible to the human eye, but by placing an infrared camera behind the acrylic your

fingertips will be visible on the infrared camera.The images that are generated by the

camera, contain white blobs (caused by the fingertips).

These blobs will be analyzed by software. Every blob corresponds to certain

coordinates. Software can by analyzing these coordinates perform certain tasks, for

example move, resize or rotate objects.

Fig 3.4 Frustrated Total Internal Reflection

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(a) (b)

Fig 3.5 (a) IR view of a touch(b)Pixel positions located on screen

Multiple points are obtained on the camera .Each point is a pixel position. Either a

single pixel or a group of pixel . Each point locations are identified and all operations

are performed .Suppose if we want to zoom a picture we use 2 fingers and move it in

or out to perform zoom in and zoom out respectievely . Two coordinates will be

located on the camere .The difference is found which is put as the offset and it is

either added or subtracted with the locations to zoom out and zoom in respectievely.

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3.5 ADVANTAGES

Multi touch based on FTIR is a simple and inexensive technique .It

constructs a multi touch display with the available and less costly

materials .

Scalable technique that enables high-resolution graphics .It provides

support to any resolution possible as all multiple points could be

generated on a camera

It acquires true touch image information at high spatial and temporal

resolutions.The actual finger print of the touch is obtained .This could

be used to determine the force sensitivity on displays , either too hard

or soft touches can be analysed.

It is scalable to large installations.Any kind of applications can be

made to suit multi touch using FTIR . Allows us to create sophisticated

multi-point widgets for applications

Larger shared-display systems ie it is well suited for use with rear-

projection like wall screens,table tops .All this lead to high resolution

graphics.

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3.6 APPLICATION

A myriad different applications for multi-touch interfaces both exist and are being

proposed. Some uses are individualistic e.g., iPhone, iPod touch, MacBook Pro,

MacBook Air, HTC Diamond . However, multi-touch technology is mainly used to

incorporate collaboration into the computing experience .

A multi touch display can be used in

Personal computers,Laptops,Tabletops,Graphics Tablets .

It supports both LCD and CRT monitors .

Telephones ,Watches ,PDAs, Mobile phones.

Advanced multi touch Gaming with high graphics support

Governmental,office and business purposes

An enhanced multimedia experience including audio,video and photo sharing

Enhanced dining experience

Applications for a multi touch display are never ending . We can even convert a

computer to a mere piece of display attached to a wall or a table

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4.CONCLUSION

Touch screens are the interface for the 21st century. Touch screens address the

conflicting demands for smaller portable electronics with larger displays, by

eliminating traditional buttons without sacrificing screen size. The recent release of

the iPhone has created a buzz around touch screen interfaces and its multi-touch

acrobatics have caught the eye of many industry leaders.

There are many ways to make a multi-touch screen. Some of the early designs

measured the change in electrical resistance or capacitance on a surface when fingers

touched it. But these devices have limited resolution, are relatively complex, and don't

easily and inexpensively scale up to large dimensions. Multi-touch technologies have

a long history. This technique using FTIR is simple and easy to implement . It

provides any resolution displays supported with high graphics .The applications being

both made and proposed are plenty in number .

A drawback of the approach is that, being camera-based, it requires a significant

amount of space behind the interaction surface, though we primarily expect

application scenarios where rear-projection would have been employed anyway (e.g.

interactive walls, tables). Also, as an optical system, it remains susceptible to harsh

lighting environments.

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5.APPENDICES

5.1 APPENDIX I

(a) (b)Fig 5.1 (a) Prototype setup (left) (b) Video output w/o diffuser (right)

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Fig 5.2 Photo Sharing and multimedia

Fig 5.3 Wonders of multi touch ,Transfering music between Ipods

Fig 5.4 A roadside wall at Helsinki

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6.REFERENCES

Low-Cost Multi-Touch Sensing through FTIR by Jefferson Y. Han

Buxton, W., Hill, R., and Rowley, P. 1985. Issues and Techniques in

Touch-Sensitive Tablet Input

Donald Hearn ,M Pauline Baker, Computer Graphics C version, 2/E

Pearson Education ,2003

Buxton, Bill. 2008. Multi-Touch Systems that I Have Known and Loved.

http://www.billbuxton.com/multitouchOverview.html

How to build a multi touch by Harry Vaan Der

Opensource,MultitouchDisplay,http://www.technologyreview.com/Infotec

h

MULTI TOUCH

Documents

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ipod touch

use of multitouch technology

multitouch interfaces

touch pixel positions

bachelor of technology

technology kochi

computer science division