Surface Wave Touch Report

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CHAPTER-1

HISTORY

1.1 Background & Origination

Touchscreens emerged from corporate research labs in the second half of the

1940s. One of the first places where they gained some visibility was in the

terminal of a computer-assisted learning terminal that came out in 1975 as part

of the Plato project. They have subsequently become familiar in kiosk systems,

such as in retail and tourist settings, onpoint of sale systems, on ATMs and onPDAs where a stylus is sometimes used to manipulate the GUI and to enter

data. The popularity ofsmart phones, portable game consoles and many types

of information appliances is driving the demand for, and the acceptance of,

touchscreens.

The HP-150 from 1983 was probably the world's earliest commercial

touchscreen computer. It did not actually have a touchscreen in the strict sense,

but a 9" Sony CRT surrounded by infrared transmitters and receivers which

detect the position of any non-transparent object on the screen.

Until the early 1950s, most consumer 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 commercialisation ofmulti-touch

technology. 1

Touchscreens are popular in heavy industry and in other situations, such as

museum displays orroom automation, where keyboard and mouse systems do

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not allow a satisfactory, intuitive, rapid, or accurate interaction by the user

with the display's content.

Historically, the touchscreen sensor and its accompanying controller-basedfirmware have been made available by a wide array of after-market system

integrators and not by display, chip or motherboard manufacturers. With time,

however, display manufacturers and chip manufacturers worldwide have

acknowledged the trend toward acceptance of touchscreens as a highly

desirable user interface component and have begun to integrate touchscreen

functionality into the fundamental design of their products.

Figure1.1 Surface Wave Touch

CHAPTER-2

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INTRODUCTION TO SURFACE WAVE TOUCHSCREEN

2.1 What it is?

The Surface Acoustic Wave (SAW) technology is one of the most advanced

touch screen types. The technology is based on two transducers (transmitting

and receiving) placed for the both of X and Y axis on the touch panel. The other

important element of SAW is placed on the glass, called reflector. The controller

sends electrical signal to the transmitting transducer, and transducer converts the

signal into ultrasonic waves and emits to reflectors that are lined up along the

edge of the panel. After reflectors refract waves to the receiving transducers, the

receiving transducer converts the waves into an electrical signal and sends back

to the controller. When a finger touches the screen, the waves are absorbed,

causing a touch event to be detected at that point.

Figure2.1 Touchscreen Panel

Compared to Resistive and Capacitive technologies, SAW technology provides

superior image clarity, resolution, and higher light transmission. Because the

panel is all glass, there are no layers that can be worn, giving this technology the

highest durability factor and also the highest clarity. Disadvantages of Surface

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Acoustic Wave (SAW) technology include the facts that the touch screen must

be touched by finger, gloved hand, or soft-tip stylus (something hard like a pen

won't work) and that the touchscreen is not completely sealable, can be affected

by large amounts of dirt, dust, and / or water in the environment.

The Surface Acoustic Wave technology is recommended for ATMs, Amusement

Parks, Banking and Financial Applications, public information kiosks, computer

based training, or other high traffic indoor environments.

The Surface Wave touchscreen has two main attributes. First, it enables one to

interact with what is displayed directly on the the hand, where it is displayed,

rather than indirect with a mouse or 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 thepersonal digital assistant (PDA), satellite navigation devices, mobile

phones, and video games.

2.2 Types of Technologies

Mainly, there are three kinds of technologies in Touchscreen Technology:

I. Resistive Touchscreen

II. Surface Wave Touchscreen

III. Capacitive Touchscreen

Resistive Touchscreen

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Offering excellent durability and resolution, resistive technology is used in a

variety of applications and environments. The Analog Resistive touch screen is a

sensor consisting of two opposing layers, each coated with a transparent

resistive material called indium tin oxide (ITO). The ITO used has a typical

sheet resistivity between 100 and 500 ohms per square. The layers are separated

by a pattern of very small transparent insulating dots. Silver ink bus bars make

an electrical connection to the surface of the ITO at the outside edges, spanning

the desired axis of the given layer. Silver ink traces connect the bus bars to an

electromechanical connector used for interfacing to the sensor. The cover sheet

has a hard, durable coating on the outer side, and a conductive coating on the

inner side. When touched, the conductive coating makes electrical contact with

the coating on the glass, and a touch is registered by the analog controller.

Resistive touchscreens deliver cost-effective, consistent and durable

performance in environments where equipment must stand up to contaminants

and liquids, such as in restaurants, factories, and hospitals. Disadvantages of

Resistive technology include only 75% optical transparency and the fact that a

sharp object can damage the resistive layers.

Surface Acoustic Wave Touchscreen

The Surface Acoustic Wave (SAW) technology is one of the most advanced

touch screen types. The technology is based on two transducers (transmitting

and receiving) placed for the both of X and Y axis on the touch panel. The other

important element of SAW is placed on the glass, called reflector. The controller

sends electrical signal to the transmitting transducer, and transducer converts the

signal into ultrasonic waves and emits to reflectors that are lined up along the

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edge of the panel. After reflectors refract waves to the receiving transducers, the

receiving transducer converts the waves into an electrical signal and sends back

to the controller. When a finger touches the screen, the waves are absorbed,

causing a touch event to be detected at that point.

Figure 2.2.Surface Wave Touch

Compared to Resistive and Capacitive technologies, SAW technology provides

superior image clarity, resolution, and higher light transmission. Because the

panel is all glass, there are no layers that can be worn, giving this technology

the highest durability factor and also the highest clarity. Disadvantages of

Surface Acoustic Wave (SAW) technology include the facts that the touch

screen must be touched by finger, gloved hand, or soft-tip stylus (something

hard like a pen won't work) and that the touchscreen is not completely

sealable, can be affected by large amounts of dirt, dust, and / or water in the

environment.

The Surface Acoustic Wave technology is recommended for ATMs,

amusement Parks, Banking and Financial Applications, public information

kiosks, computer based training, or other high traffic indoor environments.

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Capacitive Touchscreen

The touchpad contains a two-layer grid of electrodes that are connected to a

sophisticated full-custom mixed signal integrated circuit (IC) mounted on the

reverse side of the pad. The upper layer contains vertical electrode strips while

the lower layer is composed of horizontal electrode strips. The IC measures

"Mutual capacitance" from each of the horizontal electrodes to each of the

vertical electrodes. A human finger near the intersection of two electrodes

modifies the mutual capacitance between them, since a finger has very

different dielectric properties than air. When a user touches the screen, some of

the charge is transferred to the user, and makes the potential difference on the

screen. After the panel controller recognizes that, the controller will send the

X-Y axis information to the PC port.

The advantage is that capacitive technology transmits almost 90% percent ofthe light from the screen. The superior efficiency gives capacitive better than

resistive technology.

2.3 Touch Screen Functional Description

Touching the top surface compresses the flexible top layer to the supported

bottom layer causing electrical contact of the two layers between the span of

insulating dots. Determining a touch location requires two measurements, one

to obtain an X-axis coordinate and one to obtain a Y-axis coordinate. A single

axis measurement is taken by applying a drive voltage across the ITO of one

layer via the silver ink bus bar and trace connections. The voltage applied to

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this layer produces a voltage gradient across the ITO. The voltage linearly

changes from the minimum drive voltage at one end to the maximum drive

voltage at the other end. The opposing layer, via a path through its ITO and

silver ink connections, is used to measure the voltage at the point of contact on

the voltage driven layer. This process is repeated, alternating functions of the

two layers to obtain a measurement on the other axis.

Measurements are made using a 10-bit analog to digital converter (ADC). A

10-bit ADC can resolve 2-to-the-10th power or 1024 different input values in

each the horizontal and vertical direction. The four-wire system resolution is,

however, less than 1024 due to losses in the drive voltage that occur before it

reaches the touch screen ITO.

Touch point coordinates are reported to the host computer or microcontroller

through a serial communications port.

Figure.2.3. Touch functional Desription

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CHAPTER-3

CONTRUCTION

There are several principal ways to build a touchscreen. The key goals are to

recognize one or more fingers touching a display, to interpret the command that

this represents, and to communicate the command to the appropriate

application.

In the most popular techniques, the capacitive or resistive approach, there are

typically four layers;

1. Top polyester layer coated with a transparent metallic conductive coating

on the bottom

2. Adhesive spacer

3. Glass layer coated with a transparent metallic conductive coating on the

top

4. Adhesive layer on the backside of the glass for mounting.

When a user touches the surface, the system records the change in the electrical

current that flows through the display.

Dispersive-signal technology which 3M created in 2002, measures the

piezoelectric effect the voltage generated when mechanical force is applied

to a material that occurs chemically when a strengthened glass substrate is

touched.

There are two infrared-based approaches. In one, an array of sensors detects a

finger touching or almost touching the display, thereby interrupting light beams

projected over the screen. In the other, bottom-mounted infrared cameras record

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screen touches.

In each case, the system determines the intended command based on the

controls showing on the screen at the time and the location of the touch.

There are three major components in Surface Wave Touch:

1.Touch Sensor

A touch screen sensor is a clear glass panel with a touch responsive surface

which is placed over a display screen so that the responsive area of the panelcovers the viewable area of the display screen.

The sensor generally has an electrical current or signal going through it and

touching the screen causes a voltage or signal change. This voltage change is

used to determine the location of the touch to the screen

Figure 3.1 Touch Sensor

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2.Controller

The controller is a small PC card that connects between the touch sensor and

the PC. It takes information from the touch sensor and translates it into

information that PC can understand.

Figure 3.2 Touch Conroller

3.Software Driver

The driver is a software that allows the touch screen and computer to work

together. It tells the operating system how to interpret the touch event

information that is sent from the controller.

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Most touch screen drivers today are a mouse-emulation type driver. This makes

touching the screen the same as clicking your mouse at the same location on the

screen.

Figure.3.3 Touch Software Driver

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CHAPTER -4

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 routinelyabsorbed into the products that incorporate it and is effectively eliminated. As

typically occurs with any 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. With the

influence of the multi-touch-enabled iPhone, the touchscreen market for mobile

devices is projected to produce US$5 billion in 2009.

CHAPTER-5

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ERGONOMICS & USAGE

Ergonomics is defined as the study of peoples efficiency in their workingenvironment, here the working environment we are discussing is the usage of

Surface Wave Touchscreen.

5.1 Finger Stress

An ergonomic problem of touchscreens is their stress on human fingers when

used for more than a few minutes at a time, since significant pressure can berequired for certain types of touchscreen. This can be alleviated for some users

with the use of a pen or other device to add leverage and more accurate

pointing. However, the introduction of such items can sometimes be

problematic depending on the desired use case (for example, public kiosks such

as ATMs). Also, fine motor control is better achieved with a stylus, because a

finger is a rather broad and ambiguous point of contact with the screen itself.

5.2 Fingernail as Stylus

These ergonomic issues of direct touch can be bypassed by using a different

technique, provided that the user's fingernails are either short or sufficiently

long. Rather than pressing with the soft skin of an outstretched fingertip, the

finger is curled over, so that the top of the forward edge of a fingernail can be

used instead. The thumb is optionally used to provide support for the finger or

for a long fingernail, from underneath. This method does not work on

capacitive touch screens, as fingernails lack the electrical properties required to

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be sensible by capacitive sensing.

The fingernail's hard, curved surface contacts the touchscreen at a single very

small point. Therefore, much less finger pressure is needed, much greater

precision is possible (approaching that of a stylus, with a little experience),

much less skin oil is smeared onto the screen, and the fingernail can be silently

moved across the screen with very little resistance [, allowing for selecting text,

moving windows, or drawing lines.

The human fingernail consists ofkeratin which has a hardness and smoothnesssimilar to the tip of a stylus (and so will not typically scratch a touchscreen).

Alternately, very short stylus tips are available, which slip right onto the end of

a finger; this increases visibility of the contact point with the screen.

Figure. 5.1 Fingernail as Stylus

5.3 Fingerprints

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Touchscreens can suffer from the problem of fingerprints on the display. This

can be mitigated by the use of materials with optical coatings designed to

reduce the visible effects of fingerprint oils, such as the oleophobic coating usedin the iPhone 3G S, or by reducing skin contact by using a fingernail or stylus.

Combined with haptics

The user experience with touchscreens without tactile feedback or haptics can

be difficult due to latency or other factors. Research from the University of

Glasgow Scotland [Brewster, Chohan, and Brown 2007] demonstrates thatsample users reduce input errors (20%), increase input speed (20%), and lower

their cognitive load (40%) when touchscreens are combined with haptics or

tactile feedback, [vs. non-haptic touchscreens].

As an "Gorilla Arm"

The Jargon File dictionary of hacker slang defined Gorilla Arm as the failure to

understand the ergonomics of vertically mounted touch screens for prolonged

use. The proposition is that human arm held in an unsupported horizontal

position rapidly becomes fatigued and painful, the so-called "gorilla arm". It is

often cited as a prima facie example of what not to do in ergonomics, despite

contrary evidence. Vertical touchscreens still dominate in applications such as

ATMs and data kiosks in which the usage is too brief to be an ergonomic

problem.

CHAPTER-6

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COMPARISON AMONG TOUCHSCREENS

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APPLICATIONS OF SURFACE WAVE TOUCH

Transportation

From train stations to airports, touchscreen interface devices are used in almost

all forms of mass transportation.

Its applications can decrease training time, increase productivity, create higher

quality products and service, thereby raising profits.

Gaming

From Casinos and entertainment centres to counter top and bar environments.

Touch screen interface devices have been used to provide an easy and fun way

to interact. Easy to integrate touch software has expanded the potential for

creating exciting new games.

POS

For point of sales, resellers, distributers and end customers. The easy to use

touch screen enables Pos distributers to provide products that help customers

reduce employee training time and speed up transition.

Kiosk & Public Access Applications

From Trade show booths to retail outlets &from public environments to web

phones , touchscreen with built-in kiosk system provides interactive multimediasolutions. They enable kiosks to be used in environments where a keyboard or

mouse is not practical.

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Few Applications.

Figures. 7.1 Applications

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ADVANTAGES OF SURFACE WAVE TOUCH

Direct pointing to the objects.

Fast.

Finger or pen is usable (No cable required)..

No keyboard necessary.

Suited to: novices, application for information retrieval etc.

DISADVANTAGES OF SURFACE WAVE TOUCH

Low precision by using finger.

User has to sit or stand closer to the screen.

The screen may be covered more by using hand.

No direct activation to the selected function.

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CONCLUSION

Though the touch screen technology contains some limitations its

very user friendly, fast, accurate, easy for the novices & fun to

operate. It has been widely accepted. And now by just modifying a

little it can replace the mouse and key board completely in near

future.

Surface Acoustic Wave technology is one of the most advanced

touch screen types. It is based on sending acoustic waves across aclear glass panel with a series of transducers and reflectors. When a

finger touches the screen, the waves are absorbed, causing a touch

event to be detected at that point.

Because the panel is all glass there are no layers that can be worn,

giving this technology the highest durability factor and also the

highest clarity. This technology is recommended for public

information kiosks, computer based training, or other high traffic

indoor environments.

REFERENCES21

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www.elotouchsyatems.com

www.touchscreens.com

www.wikipedia.com

www.sawtouch.com

www.google.com

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