The document provides an overview of resistive touchscreen technology. It describes how resistive touchscreens work using two electrically resistive layers separated by a small gap. When the layers are pressed together at a point, this allows the location to be detected. It discusses the different types of resistive technologies including analog 4-wire, 5-wire, 8-wire and digital matrix. The key features of resistive touchscreens are also summarized such as low cost, ability to work with any input material, and improved durability and visibility compared to earlier versions.

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CHAPTER 1
1. INTRODUCTION
A touchscreen is an electronic visual display that the user can control through simple or multi-
touch gestures by touching the screen with a special stylus/pen and-or one or more fingers.
Some touchscreens use an ordinary or specially coated gloves to work while others use a special
stylus/pen only. The user can use the touchscreen to react to what is displayed and to control
how it is displayed (for example by zooming the text size).
The touchscreen enables the user to interact directly with what is displayed, rather than using
a mouse, touchpad, or any other intermediate device (other than a stylus, which is optional for
most modern touchscreens).
Touchscreens are common in devices such as game consoles, personal computers, tablet
computers, and smartphones. They can also be attached to computers or, as terminals, to
networks. They also play a prominent role in the design of digital appliances such as personal
digital assistants (PDAs), satellite navigation devices, mobile phones, and video games and
some books (Electronic books).
The popularity of smartphones, tablets, and many types of information appliances is driving
the demand and acceptance of common touchscreens for portable and functional electronics.
Touchscreens are found in the medical field and in heavy industry, as well as for automated
teller machines (ATMs), and kiosks such as museum displays or room automation, where
keyboard and mouse systems do not allow a suitably intuitive, rapid, or accurate interaction by
the user with the display's content.
From the opportunities point of view one needs to look into the various industrial applications
of this technology and this can be done by classifying touch technology patent search results
by industry. Previous researches have found that touch technology has had very extensive
applications across many industries.
FIGURE 1.1: Use of Touchscreens

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1.1 History
In 1965, First finger driven touchscreen was developed by E. A. Johnson. The basic credit of
touchscreen goes to E. A. Johnson who was first person to develop touchscreen devices.
In 1971, the first "Touch Sensor" was developed by Doctor Sam Hurst (founder of Elographics)
while he was an instructor at the University of Kentucky. This sensor, called the "Elograph,"
was patented by The University of Kentucky Research Foundation. The "Elograph" was not
transparent like modern touch screens; however, it was a significant milestone in touch screen
technology.
In 1974, the first true touch screen incorporating a transparent surface was developed by Sam
Hurst and Elographics. In 1977, Elographics developed and patented five-wire resistive
technology, the most popular touchscreen technology in use today.
Touchscreens first gained some visibility with the invention of the computer-assisted learning
terminal, which came out in 1975 as part of the PLATO project. Touchscreens have
subsequently become familiar in everyday life.
Companies use touch screens for kiosk systems in retail and tourist settings, point of sale
systems, ATMs, and PDAs, where a stylus is sometimes used to manipulate the GUI and to
enter data. The popularity of smart phones, PDAs, portable game consoles and many types of
information appliances is driving the demand for, and acceptance of, touchscreens.
From 1979–1985, the Fairlight CMI (and Fairlight CMI IIx) was a high-end musical sampling
and re-synthesis workstation that utilized light pen technology, with which the user could
allocate and manipulate sample and synthesis data, as well as access different menus within its
OS by touching the screen with the light pen. The later Fairlight series III models used a
graphics tablet in place of the light pen.
The HP-150 from 1983 was one of the world's earliest commercial touchscreen computer. It
did not have a touchscreen in the strict sense; instead, it had a 9" Sony Cathode Ray Tube
(CRT) surrounded by infrared transmitters and receivers, which detected the position of any
non-transparent object on the screen.
Until recently, 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 commercialization of multi-touch technology.
Touchscreens are popular in hospitality, and in heavy industry, as well as kiosks such as
museum displays or room automation, where keyboard and mouse systems do not allow a
suitably intuitive, rapid, or accurate interaction by the user with the display's content.
Historically, the touchscreen sensor and its accompanying controller-based firmware have been
made available by a wide array of after-market system integrators, and not by display, chip, or
motherboard manufacturers. Display manufacturers and chip manufacturers worldwide have
acknowledged the trend toward acceptance of touchscreens as a highly desirable user interface

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component and have begun to integrate touchscreen functionality into the fundamental design
of their products.
1.2 Brief History of Touchscreen
FIGURE 1.2: Brief History of Touchscreens

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1.3 Why Touch Screen?
1. Enable first-time users to interface with computers instantly, without any training
2. Eliminate operator errors because users make selections from clearly defined menus
3. Eliminate keyboards and mice, which many novice users find difficult to use
4. Rugged enough to stand up to harsh conditions where keyboards and mice can be
damaged
5. Provide fast access to all types of digital content
6. Ensure that no space is wasted since the input device is completely integrated into the
monitor
7. Most of the digital appliances support this technology
FIGURE 1.3: Cross Section of Touchscreen

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1.4 How Touchscreen Works
A basic touchscreen has three main components: a touch sensor, a controller, and a software
driver. The touchscreen is an input device, so it needs to be combined with a display and a PC
or other device to make a complete touch input system.
1. Touchsensor
A touch screen sensor is a clear glass panel with a touch responsive surface. The touch
sensor/panel is placed over a display screen so that the responsive area of the panel covers the
viewable area of the video screen. There are several different touch sensor technologies on the
market today, each using a different method to detect touch input.
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.
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.
The controller is usually installed inside the monitor for integrated monitors or it is housed in
a plastic case Tor external touch overlays.
The controller determines what type of interface/connection you will need on the PC.
Integrated touch monitors will have an extra cable connection on the back for the touchscreen.
Controllers are available that can connect to a Serial/COM port (PC) or to a USB port (PC or
Macintosh). Specialized controllers are also available that work with DVD players and other
devices.
3. Software Driver
The driver is a software update for the PC system that allows the touchscreen and computer to
work together. It tells the computer's operating system how to interpret the touch event
information that is sent from the controller.
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. This allows the
touchscreen to work with existing software and allows new applications to be developed
without the need for touchscreen specific programming.
Some equipment such as thin client terminals, DVD players, and specialized computer systems
either do not use software drivers or they have their own built-in touch screen driver.

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1.5 Types of Touchscreen Technologies
1. Resistive
1.1. Analog 4 Wire Resistive Touch
1.2. Analog 5 Wire Resistive Touch
1.3. Analog 8 Wire Resistive Touch
1.4. Digital Matrix Resistive Touch
2. Capacitive
2.1. Surface Capacitive Touch
2.2. Projected Capacitive Touch
3. Surface Acoustic Wave
4. Infrared Grid
5. Optical Imaging
6. Acoustic Pulse Recognition
Technology Resistive Infrared Capacitive Surface
acoustic
Wave
Durability 5 year 3 year 2 year 5 year
Stability High High Ok Higher
Transparency Ok Good Ok Good
Installation Built-in/On
wall
On wall Built-in Built-in/On
wall
Touch Anything Sharp Conductive Finger/ Pen
Intense Light
Resistant
Good Bad Bad Good
Response
Time
<10 ms <20 ms <15 ms 10 ms
Speed Good Good Good Low
Monitor
option
CRT CRT CRT or LCD CRT
Waterproof Good Ok Good Ok
TABLE 1.1: Comparison among different Touchscreen technologies

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CHAPTER 2
2. RESISTIVE TOUCHSCREEN
A resistive touchscreen panel comprises several layers, the most important of which are two
thin, transparent electrically resistive layers separated by a thin space. These layers face each
other with a thin gap between. The top screen (the screen that is touched) has a coating on the
underside surface of the screen. Just beneath it is a similar resistive layer on top of its substrate.
One layer has conductive connections along its sides, the other along top and bottom. A voltage
is applied to one layer, and sensed by the other. When an object, such as a fingertip or stylus
tip, presses down onto the outer surface, the two layers touch to become connected at that point:
The panel then behaves as a pair of voltage dividers, one axis at a time. By rapidly switching
between each layer, the position of a pressure on the screen can be read. As only sufficient
pressure is necessary for the touch to be sensed, they may be used with gloves on, or by using
anything rigid as a finger/stylus substitute.
FIGURE 2.1: Resistive Touchscreen
Resistive touch is used in restaurants, factories, retail stores and hospitals due to its high
resistance to liquids and contaminants.
A major benefit of resistive touch technology is its low cost.

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A resistive touch screen consists of top and bottom transparent sheets facing each other with a
gap between them. The top and bottom sheets are coated with ITO (Indium Tin Oxide). ITO is
a transparent conducting material. The top and bottom sheets have uniform resistance value
over its surface. As the top sheet gets pressed, the pressed point of the top sheet physically
yields and contacts the bottom sheet. As the ITO layers of the top and bottom sheets contact,
electricity gets conducted at the contacted point, and the location of the conducted point is
detected. Top and bottom sheets consist of PET film, glass or polycarbonate plastic is most
commonly used. The most basic combination is PET film as top sheet and glass as bottom sheet
(film/glass structure). However, other combinations such as glass/glass, film/film are also
employed depending on applications. Each combination has its distinctive features. Spacer dots
are usually printed on the bottom sheets to prevent the top and bottom sheets from contacting
when not pressed. Size and placement of the dot spacers affect the operational feeling.
Electrodes are placed on edges to obtain parallel potential distribution of X (horizontal) and Y
(vertical) directions. These electrodes are going into FPC via lead lines that are also placed on
edges, and connected with external connector. This peripheral area on which electrodes and
lead lines are placed is called insulation area. The top and bottom sheets are attached on this
insulation area. There are several sensing methods in resistive technology. The most basic
sensing methods are analog 4- wire, 5-wire, 8-wire, and digital matrix.
2.1 Types of Resistive Touchscreen
The resistive touchscreens may be further categorized into 4 major parts-
1. Analog 4 Wire Resistive
2. Analog 5 Wire Resistive
3. Analog 8 Wire Resistive
4. Digital Matrix Resistive

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2.1.1 Analog 4 Wire Resistive
Analog 4-wire resistive is the most basic sensing method of resistive technology. Top and
bottom transparent conductive sheets that have uniform resistance value, are facing each other
with a gap. When the top sheet is touched, the touched point of the top sheet yields, and contact
the bottom sheet.
FIGURE 2.2: Analog 4 Wire Resistive Touchscreen
The contacted point is conducted, and its location is sensed. As feature of analog 4-wire
resistive technology, one sheet has electrodes for the vertical direction while the other sheet
has electrodes for the horizontal direction. Voltage of a touched point is measured by the other
sheet. In this way, the touched point in X and Y directions is detected.
2.1.2 Analog 5 Wire Resistive
In analog 4-wire resistive technology, one sheet has equipotential distribution in X direction,
and the other sheet has equipotential distribution in Y direction. The two sheets measure each
other’s voltages. In analog 5-wire resistive technology on the other hand, one sheet (bottom
sheet) has equipotential distribution in both X and Y directions. Voltage of the bottom sheet is
measured by the top sheet.
Just same as analog 4-wire resistive technology, an analog 5-wire resistive sensor consists of
top and bottom sheets which are facing each other with a gap in between. Unlike analog 4-wire
resistive technology, electrodes are placed on four corners of the bottom sheet in analog 5-wire
technology.

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FIGURE 2.3: Analog 5 Wire Resistive Touch
2.1.3 Analog 8 Wire Resistive
Analog 8-wire resistive technology is similar to analog 4-wire resistive and was developed as
an advanced version of it. The structure and sensing method of 8-wire resistive technology is
same as 4-wire resistive technology. Two transparent conductive sheets are facing. One sheet
has electrodes on right and left sides, and the other sheet has electrodes on top and bottom
sides. Voltage is imposed on the sheet with electrodes on right and left sides, then a touched
point in X direction is detected as the voltage is measured by the other sheet.
FIGURE 2.4: Analog 8 Wire Resistive Touch
Then, voltage is imposed on the sheet with electrodes on top and bottom sides, then a touched
point in Y direction is detected as the voltage is measured by the other sheet.

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2.1.4 Digital Matrix Resistive Touch
Digital matrix technology was used before the analog resistive technologies such as 4-wire
and 5-wire appeared and employed on factory automation, copying machines, Faxes, phones,
mobile games, calculators cash dispensers and so on.
FIGURE 2.5: Digital Matrix Resistive Touch
Digital matrix is old type of the resistive technology. The top and bottom sheets of the digital
matrix have ITO coatings and electrodes forming in stripe, vertical and horizontal directions as
indicated in the figure. The top and bottom sheets are facing in the way that the striped ITO
coatings bisect at right angles. When pressed, the intersections of the ITO coatings contact, and
these contacted points are detected as touched points. Each intersection of the ITO coatings
works as an independent switch. It was used on the applications that did not require
writing/drawing. Once analog resistive technologies started to be employed for the applications
that require writing/drawing such as PDA, electronic personal organizer, and so on, the market
has moved from digital matrix to analog resistive technology. Analog resistive technologies
came to be employed even for such applications as factory automation and office automation
for which digital matrix was used on before. Today, analog resistive technologies are dominant
in resistive technology, and digital matrix resistive technology is seldom seen in market.

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2.2 Features of Resistive Touchscreen
1. Resistive technology is low cost due to its simple structure of touch screen and
controller circuit.
2. Resistive technology has no limitation for input material as long as top sheet yields by
pressing. The sensor can be operated with a finger, pen, and any other tool.
3. Analog resistive sensor has high resolution and location accuracy.
4. Thickness of resistive touch screens can be thin due to its simple structure.
5. Frame area (insulation area) is narrow comparing with other technologies.
6. Because of its simple structure and sensing method, it is possible to source a touch
screen and controller separately to make a touch screen unit.
7. Resistive touch screen consumes only low power.
8. Some recent resistive technologies support multi-touch input.
9. The structure that two layers of transparent ITO sheets are facing with air in between,
is sometimes considered to be a disadvantage of resistive technology in terms of
visibility. Decrease in light transmission, reflection of outside light, and Newton ring
may occur due to its structure, and spoil visibility. However, visibility of resistive
technology has been improved tremendously as film of high light transmission, anti-
newton ring film, and structure design to suppress reflection, has been developed.
10. It had been said that durability of resistive technology is not as good as other
technologies because thin transparent ITO sheets physically moves and contacts over
and over in resistive technology. Today, technical innovation of ITO films has
improved the durability of resistive technology greatly.
11. Size of over 27 - 28 inches are difficult to be built in resistive technology because of
the difficulty to make a uniform ITO coating in such large sizes.
12. There are great varieties in resistive technology. Apart from the basic film/glass
construction, glass/glass construction is often employed for automotive navigation
devices due to its toughness and environment resistance. Film/film structure is often
seen on mobile phones and other portable devices because it is light and does not crack
even if it is dropped onto the ground. Resistive touch screen may also come with a
polarizing film that will suppress reflection of sunlight.
13. As to applications of (analog) resistive technology, handheld terminals such
as smartphone, PDA, PND and portable games are majorities for consumer use. These
applications take advantages of resistive technology, that are high resolution, thinness,
and low power consumption. Other applications include automotive
navigation, camcorder, PC, POS terminal, POP terminal, Kiosk, factory
automation, sewing machine, medical devices and so on. Resistive technology was not
employed for public terminals such as Kiosk before, because of its durability and
visibility. Today, resistive touch screens are seen in many of these public terminals due
to improvement of quality and lowered cost.

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2.3 Advantages & Disadvantages of Resistive Touch
2.3.1 Advantages of Resistive Touchscreen
1. High Resolution and Accuracy
2. Fast Response
3. Pressure-activated by finger or gloved hand with a very light touch
4. Durable hard-coat front surface can be nonglare treated for reflection control or
polished for maximum clarity
5. Touchscreens and controllers are safety agency-approve components,so certification of
your system is easier
6. High resistant to liquids and contaminants
2.3.2 Disadvantages of Resistive Touchscreen
1. 80 % Clarity
2. Resistive layers can be damaged by a sharp object
3. Not suited for larger displays
4. Less accurate at edges
5. Requires pressure sense technique so not more durable

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CHAPTER 3
3. CAPACITIVE TOUCHSCREEN
A capacitive touchscreen panel consists of an insulator such as glass, coated with a transparent
conductor such as indium tin oxide (ITO). As the human body is also an electrical conductor,
touching the surface of the screen results in a distortion of the screen's electrostatic field,
measurable as a change in capacitance. Different technologies may be used to determine the
location of the touch. The location is then sent to the controller for processing.
Unlike a resistive touchscreen, one cannot use a capacitive touchscreen through most types of
electrically insulating material, such as gloves. This disadvantage especially affects usability
in consumer electronics, such as touch tablet PCs and capacitive smartphones in cold weather.
It can be overcome with a special capacitive stylus, or a special application glove with an
embroidered patch of conductive thread passing through it and contacting the user's fingertip.
FIGURE 3.1: Capacitive Touchscreen
The largest capacitive display manufacturers continue to develop thinner and more accurate
touchscreens, with touchscreens for mobile devices now being produced with 'incell'
technology that eliminates a layer, such as Samsung's Super AMOLED screens, by building
the capacitors inside the display itself. This type of touchscreen reduces the visible distance
(within millimetres) between the user's finger and what the user is touching on the screen,
creating a more direct contact with the content displayed and enabling taps and gestures to be
more responsive.

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Capacitive touchscreens are mainly classified into two categories:
1. Surface Capacitive
2. Projected Capacitive
3.1 Surface Capacitive Touchscreen
In this basic technology, only one side of the insulator is coated with a conductive layer. A
small voltage is applied to the layer, resulting in a uniform electrostatic field. When a
conductor, such as a human finger, touches the uncoated surface, a capacitor is dynamically
formed.
FIGURE 3.2: Surface Capacitive Touchscreen
The sensor's controller can determine the location of the touch indirectly from the change in
the capacitance as measured from the four corners of the panel. As it has no moving parts, it is
moderately durable but has limited resolution, is prone to false signals from parasitic capacitive
coupling, and needs calibration during manufacture. It is therefore most often used in simple
applications such as industrial controls and kiosks.

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3.1.1 Features of Surface Capacitive Touchscreens
1. Surface capacitive technology is suitable for large size monitors.
2. Surface capacitive sensor can respond to light touch, and no pressure force is needed
for detection.
3. Visibility is high because structure is only one glass layer.
4. Surface capacitive is structurally tough as it is made of one sheet of glass.
5. Surface capacitive does not get affected by moist, dust, or grease.
6. Parallax is minimized in surface capacitive.
7. Surface capacitive has high resolution and high response speed.
8. Basically, surface capacitive can detect touches by fingers only. It does not detect input
by gloved hand. Some surface capacitive touch screens may detect touches by thin-
gloved hand, but they do not support the combination use of bare finger and gloved
finger. Some surface capacitive touch screens support pen writing, but they usually does
not support combination use of finger touch and pen writing.
9. Surface capacitive technology does not support multi-touch.
10. Surface capacitive touch screen is likely to be affected by noise. Recently, tolerance for
noise has been improved with various methods such as noise shielding.
11. Surface capacitive touch screens tend to be employed for applications that are large size
(over 12 inch), used by general public, and requiring high-quality looking, high
resolution and high durability. They are used on ATM, ticketing
machine, kiosk, POS, office automation, factory automation, arcade games,
and medical and food industry. Surface capacitive touch screens are especially popular
in amusement fields such as casino gaming due to its high durability and visibility.

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3.2 Projected Capacitive Touchscreen
Projected capacitive touch also known as PCT technology is a variant of capacitive touch
technology. All PCT touch screens are made up of a matrix of rows and columns of conductive
material, layered on sheets of glass. This can be done either by etching a single conductive
layer to form a grid pattern of electrodes, or by etching two separate, perpendicular layers of
conductive material with parallel lines or tracks to form a grid.
FIGURE 3.3: Projected Capacitive Touchscreen
Voltage applied to this grid creates a uniform electrostatic field, which can be measured. When
a conductive object, such as a finger, comes into contact with a PCT panel, it distorts the local
electrostatic field at that point. This is measurable as a change in capacitance. If a finger bridges
the gap between two of the "tracks", the charge field is further interrupted and detected by the
controller. The capacitance can be changed and measured at every individual point on the grid
(intersection). Therefore, this system is able to accurately track touches.
Due to the top layer of a PCT being glass, it is a more robust solution than less costly resistive
touch technology. Additionally, unlike traditional capacitive touch technology, it is possible
for a PCT system to sense a passive stylus or gloved fingers. Moisture on the surface of the
panel, high humidity, or collected dust can interfere with the performance of a PCT system.

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There are two types of Projected Capacitive Touchscreen:
1. Mutual capacitance
2. Self-capacitance.
3.2.1 Mutual Capacitance PCT
This is a common PCT approach, which makes use of the fact that most conductive objects are
able to hold a charge if they are very close together.
FIGURE 3.4: Mutual Capacitive Type Projected Capacitive Touchscreen
In mutual capacitive sensors, a capacitor is inherently formed by the row trace and column
trace at each intersection of the grid.
A 16 X 14 array, for example, would have 224 independent capacitors. A voltage is applied to
the rows or columns. Bringing a finger or conductive stylus close to the surface of the sensor
changes the local electrostatic field which reduces the mutual capacitance. The capacitance
change at every individual point on the grid can be measured to accurately determine the touch
location by measuring the voltage in the other axis. Mutual capacitance allows multitouch
operation where multiple fingers, palms or styli can be accurately tracked at the same time.
3.2.2 Self Capacitance PCT
Self-capacitance sensors can have the same XY grid as mutual capacitance sensors, but the
columns and rows operate independently. With self-capacitance, the capacitive load of a finger
is measured on each column or row electrode by a current meter. This method produces a
stronger signal than mutual capacitance, but it is unable to resolve accurately more than one
finger, which results in "ghosting", or misplaced location sensing.

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3.3 Features of Projected Capacitive Touchscreens
1. Projected capacitive supports multiple touches, thus supports various elaborate inputs.
2. Projected capacitive has relatively long life because it has no moving parts in operation.
3. Projected capacitive has high durability.
4. Sensitivity of the sensor can be adjusted. If sensitivity is adjusted to high level, the
touch screen can be operated over a cover glass or cover plastic sheet. These cover
sheets provide additional durability, environmental resistance, and a lot of flexibility in
design.
5. If sensitivity is increased, projected capacitive can be operated with gloved fingers.
6. Projected capacitive touch screen is excellent at optical property.
7. Projected capacitive responds to light touch. No pressure force is needed for detection.
8. Projected capacitive requires an advanced technology to measure electrostatic
capacitance and achieve precise locational information from it. Unlike resistive
technology, it does not work simply by connecting a touch screen with a controller
sourced from somewhere. A projected capacitive touch screen and controller need to
be designed together.
9. Projected capacitive is susceptible to electrical noise due to its detection mechanism.
Noise from LCD is especially influential to the sensor. Recently, various methods are
developed to improve tolerance for noise.
10. Projected capacitive requires fine pattering, thus takes high processing cost.
11. The notable application of projected capacitive is smartphone. Projected capacitive has
also been dominant in personal devices such as portable PC, mobile game, and portable
audio player.

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CHAPTER 4
4. OTHER TOUCH SCREEN TECHNOLOGIES
4.1 Optical Imaging
Optical touchscreens are a relatively modern development in touchscreen technology,
in which two or more image sensors are placed around the edges (mostly the corners)
of the screen. Infrared back lights are placed in the camera's field of view on the other
side of the screen. A touch shows up as a shadow and each pair of cameras can then be
pinpointed to locate the touch or even measure the size of the touching object (see visual
hull). This technology is growing in popularity, due to its scalability, versatility, and
affordability, especially for bigger units.
FIGURE 4.1: Optical Touchscreen Technology
Advantages:
1. Highest image clarity and light transmission of all touch technologies
2. Unlimited “touch-life”
3. Impervious to surface scratches
Disadvantages:
1. Accidental activation may occur because the infrared beams are actually above the glass
surface
2. Dust, oil, or grease build up on screen or frame could impede light beam causing
malfunction
3. Sensitive to water, snow, rain
4. May be sensitive to ambient light interference
5. Higher cost

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4.2 Infrared Grid Technology
Infrared touch screen monitors do not overlay the display with an additional screen or screen
sandwich. Instead, infrared monitors use IR emitters and receivers to create an invisible grid of
light beams across the screen. This ensures the best possible image quality. When an object
interrupts the invisible infrared light beam, the sensors are able to locate the touch point!
FIGURE 4.2: Infrared Grid Touchscreen
4.3 Surface Acoustic Wave (SAW)
SAW touch screen monitors utilize a series of piezoelectric transducers and receivers along the
sides of the monitor’s glass plate to create an invisible grid of ultrasonic waves on the surface.
When the panel is touched, a portion of the wave is absorbed. This allows the receiving
transducer to locate the touch point and send this data to the computer. SAW monitors can be
activated by a finger, gloved hand, or soft-tip stylus. SAW monitors offer easy use and high
visibility.
FIGURE 4.3: Surface Acoustic Wave Touchscreen

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Advantages:
1. Excellent image clarity
2. Even better scratch resistance than capacitive
3. High “touch-life”
Disadvantages:
1. Will not activate with hard items (pen, credit card, or fingernail)
2. Water droplets may cause false-triggering
3. Solid contaminants on the screen can create non-touch areas until they are removed
4.4 Frustrated Total Internal Reflection (FTIR)
It is a name used by the multi-touch community to describe the multi-touch methodology
developed by Jeff Han (Han 2005). The phrase actually refers to the well-known underlying
physical phenomena underlying Han’s method. Total Internal Reflection describes a condition
present in certain materials when light enters one material from another material with a higher
refractive index, at an angle of incidence greater than a specific angle. The specific angle at
which this occurs depends on the refractive indexes of both materials, and is known as
the critical angle, which can be calculated mathematically using Snell’s Law.
FIGURE 4.4: FTIR Touchscreen Technology
When this happens, no refraction occurs in the material, and the light beam is totally reflected.
Han’s method uses this to great effect, flooding the inside of a piece of acrylic with infrared
light by trapping the light rays within the acrylic using the principle of Total Internal Reflection.
When the user comes into contact with the surface, the light rays are said to be frustrated, since
they can now pass through into the contact material (usually skin), and the reflection is no
longer total at that point.

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4.5 Coded LCD: Bidirectional Screen
A new system that turns LCD displays into giant cameras that provide gestural control of
objects on-screen was introduced by MIT Media Lab in December, 2009. Instead of an LCD,
an array of pinholes is placed in front of sensors. Light passing through each pinhole strikes a
small block of sensors producing a low-resolution image. Since each pinhole image is taken
from a slightly different position, all combined images provide a good depth information about
the sensed image.
Pinholes are problematic because they allow very little light to reach the sensors, requiring
impractically long exposure times. Instead of pinholes, an array of liquid crystals could work
similarly but more effectively: The LCD's panel is composed of patterns of 19-by-19 blocks,
each divided into a regular pattern of differently sized black-and-white rectangles. Each white
area of the bi-coloured pixels allows light to pass through. Background software uses 4D light
fields to calculate depth map, changes the scene, and collects gesture information. The LCD
alternates between mask pattern display and a normal scene display at a very high
frequency/rate.

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CHAPTER 5
5. MULTI-TOUCH TECHNOLOGY
Till now all the technologies mentioned are used as single touch devices i.e. can recognize
only single touch at time. Whereas many devices now come with multi-touch technologies,
though multi-touch touchscreens can be made of using capacitive & resistive technologies
some of the new technologies include FTIR, Optical technologies which are capable of
sensing multiple touches on single screen at same time.
Multi-touch technology enables a surface (a trackpad or touchscreen) to recognize the presence
of more than one or more than two points of contact with the surface. The term "Multi-Touch"
was coined in 2007 by Apple Inc. at the Macworld - iWorld iPhone stevenote. This plural-point
awareness may be used to implement additional functionality, such as pinch to zoom or to
activate certain subroutines attached to predefined gestures.
FIGURE 5.1: Multi-Touch Operations
The two different uses of the term are the result of the quick developments in this field, which
resulted in many companies using the term "multi-touch" for marketing purposes for older
technology that is called gesture-enhanced single-touch or several other terms by other
companies and researchers. There are several other similar or related terms that attempt to
differentiate between whether a device can exactly determine or only approximate the location
of different points of contact and that attempt to further differentiate between the various
technological capabilities, but they are often used as synonyms in marketing.

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Technologies involved with Multi-touch
1. FTIR :Frustrated Total Internal Reflection
2. DI: Diffused Illumination
3. DSI: Diffused Surface Illumination
4. LED LP: Led Laser Plane
5. LLP: Laser Light Plane
FIGURE 5.2: Various Multi-Touch Technologies

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CHAPTER 6
6.1 ADVANTAGES OF TOUCHSCREEN
1. Touchscreen enables people to use computers without any training
2. This technology is simple & user friendly
3. Touch screen eliminates operator errors
4. Multi touch functions are possible (e.g. zoom in, zoom out, rotation)
5. Proven reliability, expended functionality & decreasing cost
6. Fast access to all types of digital media
7. It ensures no space is wasted as input device is completely integrated into monitor
8. Touch screens provide sufficient security
9. Touch screen interfaces can be updated with simple software changes
6.2 DISADVANTAGES OF TOUCHSCREEN
1. Low precision in case of virtual touch screens
2. Although user friendly, touch screens cannot be used to enter large amount of data
3. Touch screens will cost about two to three times of the existing keyboard
4. Touch screen devices are expensive than non-touch type devices
5. Another failure include not getting fast processing behind the buttons
6. Larges displays are more power consuming
7. Conductive touchscreens require special conducting material/ stylus to operate
8. Moisture & dust produce another problem

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CHAPTER 7
7.1 APPLICATIONS OF TOUCHSCREEN
1. Public Information Displays
Information kiosks, tourism displays, trade show displays, and other electronic displays
are used by many people that have little or no computing experience. The user-friendly
touch screen interface can be less intimidating and easier to use than other input devices,
especially for novice users. A touchscreen can help make your information more easily
accessible by allowing users to navigate your presentation by simply touching the
display screen.
2. Retail and Restaurant Systems
Time is money, especially in a fast paced retail or restaurant environment. Touchscreen
systems are easy to use so employees can get work done faster, and training time can
be reduced for new employees. And because input is done right on the screen, valuable
counter space can be saved. Touchscreens can be used in cash registers, order entry
stations, seating and reservation systems, and more.
3. Customer Self-Service
Self-service touch screen terminals can be used to improve customer service at busy
stores, fast service restaurants, transportation hubs, and more. Customers can quickly
place their own orders or check themselves in or out, saving them time, and decreasing
wait times for other customers. Automated teller Machines (ATMs) and airline e-ticket
terminals are examples of self-service stations that can benefit from touchscreen input.
4. Control and Automation Systems
The touch screen interface is useful in systems ranging from industrial process control
to home automation. By integrating the input device with the display, valuable
workspace can be saved. And with a graphical interface, operators can monitor and
control complex operations in real-time by simply touching the screen.
5. Computer Based Training
Because the touch screen interface is more user-friendly than other input devices,
overall training time for computer novices, and therefore training expense, can be

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reduced. It can also help to make learning more fun and interactive, which can lead to
a more beneficial training experience for both students and educators.
6. Assistive Technology
The touch screen interface can be beneficial to those that have difficulty using other
input devices such as a mouse or keyboard. When used in conjunction with software
such as on-screen keyboards, or other assistive technology, they can help make
computing resources more available to people that have difficulty using computers.
CHI Centres, Inc. has developed a system that allows non-verbal individuals to
communicate using a PC and touchscreen display.
And many more applications...

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CONCLUSION
Touch systems represent a rapidly growing subset of the display market. The majority of touch
systems include touch sensors relying on vacuum-deposited coatings, so touch coatings present
opportunity for suppliers of vacuum coatings and coating equipments.
Touch sensor manufactures currently require thin films in the areas of transparent conductors,
optical interference coating and mechanical protective coatings. Touch sensors technical
requirements dovetail well with those of the flat panel and display filter markets. The reality
should provide value added opportunities to operations participating in these areas.
New ways to bring people closer together utilizing the most recent technological advances (i.e.
cell phones and handhelds) will continue to be implemented and studied. Moving from
automated screening to computerized full assessments of both patients and caregivers is the
next logical step of this program and is currently in process at City of Hope. Future use of
technology will help to bridge the gap between detection of problem-related distress and
referrals for assessment or treatment, creating proactive approach to whole-person-centered
care.

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REFERENCES
1. “Touchscreens 101: Understanding Touchscreen Technology and Design” published
by Planet Analog
2. “The State of the Touch-Screen Panel Market in 2011” by Duke Lee
3. “Issues & techniques in touch-sensitive table input” by Buxton W. & Hill R.
4. Stone M. D. "Touch-screens for intuitive input”, PC Magazine
5. “Comparative study of Various Touchscreens” by Semantics-scholars.org
6. “Enhancing touch interaction on Human, Screen, everyday objects” by Munehiko
Sato, Ivan Poupyrev & Chris Harrison
7. “A brief history of touch screen” by arstechnia.com
8. “How it works :The technology of touchscreens” article by Computerworld.com
9. “Touchscreen technologies in brief” dmccoltd.com