HIGHER INSTITUITE FOR APPLIED SCIENCES AND TECHNOLOGY

Touch Screen

Technologies Prepared by: Mohammed Al-Shirif

Supervisor: Eng. Mohedeen Awad

Language supervisor: Mrs. Nada Mouhanna

Coordinator: Dr. Nizar Zarka

Date: 28/03/2013 2nd Semester

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TABLE OF CONTENT:

1. ABSTRACT: ......................................................................................................................................................... 5

2. INTRODUCTION: ............................................................................................................................................ 6

3. ADVANTAGES AND DISADVANTAGES OF TO UCH SCREENS: ........................................................................................ 8

4. ANATOMY OF A TOUC HSCREEN: ............................................................................................................................ 8

5. RESISTIVE TOUCH TECHNOLOGIES: ......................................................................................................................... 9

5.1 RESISTIVE TOUCH STRUCTURE: ......................................................................................................................... 9

5.2 HOW DOES RESISTIVE TOUCH SCREEN WORK?...................................................................................................... 9

5.3 FOUR-WIRE RESISTIVE TOUCHSCREEN TECHNOLOGY............................................................................................ 10

5.4 FIVE-WIRE RESISTIVE TOUCHSCREEN TECHNOLOGY: ............................................................................................ 11

5.5 FOUR-WIRE VS. FIVE-WIRE RESISTIVE TOUCHSCREEN TECHNOLOGY: ..................................................................... 12

5.6 DIGITAL RESISTIVE TECHNOLOGY:............................................................................................................................ 13

5.7 PROS AND CONS OF RESISTIVE TOUCHSCREEN TECHNOLOGY: ................................................................................. 13

6. CAPACITIVE TOUCH TECHNOLOGIES: .................................................................................................................... 14

6.1 PROJECTED CAPACITIVE TOUCH TECHNOLOGY: ................................................................................................... 14

6.1.1 How does it work? .....................................................................................................................14

6.1.4 Mutual-capacitance vs. Self-Capacitance: ......................................................................................16

6.1.2 Projected capacitive technology advantages: ..................................................................................17

6.1.3 Projected capacitive technology drawbacks:...................................................................................17

6.2 SURFACE CAPACITIVE TOUCHSCREEN TECHNOLOGY: ....................................................................................................... 18

6.2.1 How does it work? .....................................................................................................................18

6.2.2 Surface capacitive technology advantages: ....................................................................................18

6.2.3 Surface capacitive technology disadvantages: .................................................................................19

6.3 PROS AND CONS OF CAPACITIVE TOUCH TECHNOLOGY: ......................................................................................... 19

7. SAW TOUCH SCREEN TECHNOLOGY: ..................................................................................................................... 20

7.1 HOW DOES IT WORK?......................................................................................................................................... 20

7.2 OPPORTUNITIES AND LIMITATIONS OF SAW TOUCH TECHNOLOGY: ...................................................................................... 21

8. BENDING WAVE TOUCHSCREEN TECHNOLOGY: ...................................................................................................... 22

9. INFRARED TOUCH SCREEN TECHNOLOGY: ............................................................................................................. 23

9.1 HOW IT WORKS? .............................................................................................................................................. 23

9.2 LIMITATION AND CONSIDERATION OF INFRARED TOUCHSCREEN: .......................................................................................... 23

10. OPTICAL IMAGING TOUCH TECHNOLOGY: ........................................................................................................... 25

10.1. HOW IT WORKS?......................................................................................................................................... 25

10.2. PROS AND CONS OF CAMERA-BASED TECHNOLOGY: ..................................................................................................... 26

10.3. FUTURE OF CAMERA BASED TOUCHSCREEN TECHNOLOGY: .............................................................................................. 27

11. COMPARISON STUDY: ...................................................................................................................................... 28

11.1. LIGHT TRANSMITTANCE: ................................................................................................................................... 28

11.2 THE DURABILITY: ............................................................................................................................................ 28

11.3 CALIBRATION STABILITY: .................................................................................................................................... 28

11.4 STYLUS FLEXIBILITY: ......................................................................................................................................... 28

11.5 SIZE:.......................................................................................................................................................... 29

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11.6 APPLICATIONS: .............................................................................................................................................. 29

11.7 COST: ........................................................................................................................................................ 29

11.8 TOUCHSCREEN RESOLUTION ......................................................................................................................... 29

12. PRACTICAL GUIDE TO DETERMINE WHICH TYPE IS YOUR TOUCHSCREEN: ................................................................. 30

13. MUL TI TOUCH TECHNOLOGY: ............................................................................................................................ 31

13.1. WHY MULTI-TOUCH HAS BECOME SO IMPORTANT?.................................................................................................... 31

13.2. HOW MANY TOUCHES ARE ENOUGH? ................................................................................................................... 31

14. CHEEK CHECK AND Z-AXIS: ................................................................................................................................ 32

15. TOUCH SCREEN OS: .......................................................................................................................................... 32

16. INTERACTION: ................................................................................................................................................. 33

17. MARKET TRENDS: ............................................................................................................................................ 34

17.1. THE RECENT HISTORY: ..................................................................................................................................... 34

17.2. MAINSTREAM TECHNOLOGIES: ............................................................................................................................ 34

17.3. 2013 TRENDS: ............................................................................................................................................. 35

17.4. WHAT IS NEXT? ............................................................................................................................................ 37

18. CONCLUSION: ................................................................................................................................................. 38

19. REFERENCES: .................................................................................................................................................. 39

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LIST OF FIGURES: FIGURE 1:EASE OF USING TOUCH SCREENS .............................................................................................................. 6

FIGURE 2: TOUCH SCREEN TECHNOLOGIES .............................................................................................................. 7

FIGURE 3: STRUCTURE OF THE RESISTIVE TOUCH PANELS............................................................................................... 9

FIGURE 4: WORKING OF RESISTIVE TOUCHSCREENS ..................................................................................................... 9

FIGURE 5: FOUR-WIRE RESISTIVE .......................................................................................................................10

FIGURE 6: WORKING OF 4-WIRE SYSTEMS .............................................................................................................10

FIGURE 7: LIMITATION OF 4-WIRE ......................................................................................................................11

FIGURE 8: FIVE-WIRE RESISTIVE ........................................................................................................................11

FIGURE 9: WORKING OF 5-WIRE TECHNOLOGY........................................................................................................12

FIGURE 10: DIGITAL RESISTIVE TECHNOLOGY ..........................................................................................................13

FIGURE 11: LIFE CYCLE OF THE ISOLATING DOTS ........................................................................................................13

FIGURE 12: CONCEPT OF CPACITIVE TECHNOLOGY.....................................................................................................14

FIGURE 13: PROJECTED CAPACITIVE STRUCTURE.......................................................................................................14

FIGURE 14:WORKING OF PROJECTED CAPACITIVE.....................................................................................................15

FIGURE 15: SENSING METHOD OF PROJECTED CAPACITIVE ...........................................................................................15

FIGURE 16: SELF CAPACITANCE .........................................................................................................................16

FIGURE 17: MUTUAL CAPACITANCE ....................................................................................................................16

FIGURE 18: WORKING OF SURFACE CAPACITIVE.......................................................................................................18

FIGURE 19: SURFACE ACOUSTIC WAVE.................................................................................................................20

FIGURE 20: WORKING OF SAW TOUCH SCREEN .......................................................................................................20

FIGURE 21: CONCEPTUAL DRAWING OF A BENDING-WAVE TOUCH SCREEN ............................................................22

FIGURE 22: WORKING OF INFRARED TOUCH TECHNOLOGY ...........................................................................................23

FIGURE 23: WORKING OF CAMERA-BASED TOUCH TECHNOLOGY .....................................................................................25

FIGURE 24: CAMERA-BASED OVERLAY CAN EASILY CONVERT ANY LCD SCREEN INTO TOUCHSCREEN ...............................................26

FIGURE 25: THE FUTURE OF OPTICAL IMAGING TOUCH TECH. ........................................................................................27

FIGURE 26: IGNORED TOUCH............................................................................................................................32

FIGURE 27: TOUCH SCREEN MODULES DISTRIBUTION .................................................................................................34

FIGURE 28: MARKET SIZE FOR TOUCH MODULES BY DEVICE SIZE IN 2012 .............................................................35

FIGURE 29: GLOBAL TOUCH SCREEN MARKET REVENUES..............................................................................................36

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LIST OF TABLES: TABLE 1: ADVANTAGES & DISADVANTAGES OF TOUCH SCREENS .......................................................................................8

TABLE 2: DIFFERENCES BETWEEN 4-WIRE AND 5-WIRE............................................................................................... 12

TABLE 3: PROS & CONS OF RESISTIVE TOUCH TECHNOLOGY.......................................................................................... 13

TABLE 4: DIFFERENCES BETWEEN MUTUAL-CAPACITANCE & SELF-CAPACITANCE ................................................................... 16

TABLE 5: PROS & CONS OF SURFACE ACOUSTIC WAVE TECHNOLOGY ............................................................................... 21

TABLE 6: PROS & CONS OF TRADITIONAL INFRARED TOUCH TECHNOLOGY .......................................................................... 24

TABLE 7: A BRIEF COMPARSION BETWEEN DIFFERENT TOUCH TECHNOLOGIES ...................................................................... 30

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1. Abstract: Touchscreen technology and devices that use that technology have become widely popular over

the past few years. Even so, very small amount of people knows that there are different technologies

implemented in those devices that they use in everyday life. Through this seminar, we would try to

present the different solutions currently available on the market. Simultaneously, we will compare

between those solutions, emphasizing on differences between those technologies, and making the

differences between them more obvious and understandable. Later, we will give our opinions on

market trends in the future, and our vision and conclusion about this topic .

Keywords:

Touchscreen technologies, resistive touchscreen, capacitive, surface acoustic wave, infrared, optical imaging, multi-touch, interaction.

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2. Introduction:

After over two decades virtually been dominated by the use of mice and keyboards, the last few

years have been characterized by the rise of alternative input devices, generally designed for

improved ergonomics. The touchscreen is the most sophisticated computer access technology to-

date, with the fastest growing market demand. Today, virtually all software requires some kind of

pointing device. The Touch Screen is a technological advancement on traditional input and pointing

devices used to access applications.

A touchscreen is an electronic visual display that can detect the presence and location of a touch

within the display area. The term generally refers to touching the display of the device with a finger

or hand. Touchscreens can also sense other passive objects, such as a stylus.

The touchscreen has two main attributes. First, it enables one to interact directly with what is displayed, rather than indirectly with a pointer controlled by a mouse or touchpad. Secondly, it lets

one do so without requiring any intermediate device that would need to be held in the hand (other than a stylus, which is optional for most modern touchscreens). [MA10]

With touchscreen technology a computer display can function as both input device and output device. A touch sensitive screen provides a user with a friendlier input interface that doesn’t require

extensive computer skills or literacy. Such interface is an easy way to communicate with devices where the user touches the screen to select options presented on the screen.

Mechanical QWERTY keyboards and their associated mice are falling out of favor to be replaced by sleek touch screens. In touch screen systems the user doesn't need to look away from the screen

to a keyboard and back again. Entering wrong information is impossible with a touchscreen, only valid options are offered on the screen. There are no loose pieces of hardware to be damaged or lost

Touchscreens are very intuitive; it is natural for people to respond to their environment by touching. Not only adults but also

Children can easily interact with this technology (see figure 1). Moreover, this interface can be beneficial to those that have difficulty in using other input devices such as a mouse or

keyboard. Touch panels are accessible to people with significant physical disabilities. They are also efficient for Visually

Impaired, providing full access to the screen with easy

adjustments that adapt to individualized needs.

Touch screens started to be developed in the second half of the

1960s. Early work was done at the IBM, the University of Illinois, and Ottawa Canada. By 1971 a

number of different techniques had been disclosed. Touchscreens have subsequently become

familiar in everyday life.

Touch screen technology are widely available and in use in many facets of society. Touch screen

can be found in use as public information displays, retail and restaurant systems, POS, ATM,

computer-based training systems, customer self-service aids, control and automation systems,

assistive technology for the disabled, tourism kiosks, GPS systems, phones, tablets, game consoles,

and continues to appear in newer technologies. Touch screens have reached into every industry,

every product type, every size, and every application at every price point.

Figure 1: Ease of Using touch screens Figure 1:Ease of using touch screens

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As touchscreen usage increases and new applications emerge, it is important to understand the differences between touchscreen technologies. There are over a dozen touch-screen technologies in use, and no single technology can meet 100% of the requirements for every application. As a result,

there has been an accelerated stream of innovations in touchscreen technologies in the last few years. The range of user environments for these applications has created a wide variety of touch

technologies, each with unique characteristics contributing to application advantages and disadvantages. The most used touch technologies include projected capacitive, resistive, surface capacitive, surface acoustic wave (SAW), infrared beam (IR) and camera-based. Other technologies

include: dispersive signal technology (DST), acoustic pulse recognition, LCD in-cell optical, and force sensing are out of use.

Touch technologies are classified into four main types: resistive, capacitive, acoustic and optical.

Each type has its own different specific technologies. See figure (2).

Figure 2: Touch Screen Technologies

Actually, there are 11 categories within the touchscreen market, but projected capacitive screens

have taken the majority of the market. Resistive screens held the leading market share for many

years, but the higher-quality projected capacitive screens took the lead in 2010

Let's see how the screen of your tablet or smartphone responds to touch and slide of your fingers.

What there in between your fingers and mobile screen that is makes it happen?

With just swiping of your fingers you can control the whole functionality of your gadgets. It was

IBM, that introduced touch screen in mobiles for the first time in mobile technology's history and

since then almost every new Company is manufacturing its devices with this technology. Thanks to

brilliant minds behind this technology, Dr. Sam Hurst, Steve Jobs, Helwett & Packard and others.

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3. Advantages and Disadvantages of touch screens:

Advantage Disadvantage

Touching a visual display of choices requires

little thinking and is a form of direct manipulation that is easy to learn.

Touch screens are the fastest pointing

devices. Touch screens have easier hand eye

coordination than mice or keyboards. Touch screens are durable in public access

and in high volume usage. There are no loose pieces of hardware to be

damaged or lost. No extra work space is required as with

other pointing devices

User's hand may obscure the screen.

Screens need to be installed at a lower position and tilted to reduce arm fatigue.

Some reduction in image brightness may occur.

They cost more than alternative devices. These devices require massive computing

power which leads to slow devices and low battery life

Touchscreen devices usually has no

additional keys and this means when an application crashes, without crashing the OS,

you can't get to the main menu as the whole screen becomes unresponsive

Table 1: Advantages & Disadvantages of touch screens

4. Anatomy of a touchscreen: Knowing what you need is an important first step in designing a touchscreen product. Vendors in

the touchscreen supply chain frequently offer different pieces of the puzzle, often times combining

several to create a value chain for the end customer. There are four key elements:

1- Front panel or bezel: The front panel or bezel is the outermost skin of the end product. In some

products, this bezel will encompass a protective clear overlay to keep weather and moisture out

of the system, and to resist scratching and vandalism to the underlying sensor technology.

2- Touch controller: The touch-controller is generally a small microcontroller-based IC that sits

between the touch sensor and the embedded system controller. This IC can either be located on

a controller board inside the system or it can be located on a flexible printed circuit (FPC)

affixed to the glass touch sensor. This touch controller takes information from the touch sensor

and translates it into information that the PC or embedded system controller can understand.

3- Touch sensor: A touchscreen "sensor" is a clear glass panel with a touch-responsive surface.

This sensor may be placed over an LCD (Like resistive and capacitive systems) or on the frame

(in SAW and Infrared touch systems) so that the touch area of the panel covers the viewable

area of the video screen. There are many different touch-sensor technologies on the market

today, each using a different method to detect touch input. Fundamentally, most technologies

use an electrical current running through the panel that, when touched, causes a voltage or

signal change. This voltage change is sensed by the touch controller to determine the location of

the touch on the screen.

4- System software: This software allows the touchscreen sensor and system controller to work

together and tells the product's operating system how to interpret the touch-event information

that is sent from the controller.

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5. Resistive Touch Technologies: Before 2010 Resistive was the dominant type of touch screen technology. It is a low-cost solution

found in many touch screens, including hand-held computers, PDAs, consumer electronics and

point-of-sale-applications. The resistive screen is popular because of its relatively low price (at

smaller screen sizes), and ability to use a range of input objects like fingers, gloves, credit card, and

any stylus as the Resistive touchscreens are pressure sensitive. There are two different basic

resistive technologies: 4-wire (low cost, short life) is common in mobile devices and 5-wire (higher

cost, long life) is common in stationary devices.

5.1 Resistive Touch Structure:

A resistive system consists of a several

layers that detect and register the location

of the touch. The outermost layer is a

durable hard coating to protect the more

delicate touch sensors usually made of

Polyester .The innermost layer is a rigid

Glass Substrate .The exterior face of the

glass substrate is coated with a conductive

transparent layer. The interior face of the

polyester film is also coated with another

conductive transparent layer made of

Indium Tin Oxide (ITO). Between the

glass and the polyester sheet there are

thousands of tiny separator dots isolating

top and bottom conductive layers from each

other .See figure 3.

5.2 How does Resistive Touch Screen Work?

When an object such as a finger, presses down on a point on the panel's outer surface the two conductive

layers become connected at that point producing a switch closing in the circuit .See figure 4. The panel then

behaves as a pair of voltage dividers with connected outputs. This causes a change in the electrical voltage

which is registered as a touch event and sent to the controller for processing. The touch screen controller gets

the alternating voltages between the two layers and converts them into the digital X and Y coordinates of the

activated area. Once the coordinates are known, a special software driver translates the touch into

something that the operating system can understand.

Figure 3: Structure of the Resistive Touch panels

Figure 4: Working of resistive touchscreens

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5.3 Four-Wire Resistive touchscreen technology

All resistive touch screens use essentially the same voltage-driven operating principles. The

electrically simplest way to produce a resistive touch screen is to utilize 4-wire technology.

The goal of a 4-wire circuit is to be able

to produce two alternating linear

voltage gradients in both the X and Y

direction. To achieve this two resistive

circuits are used, a circuit in X-axis

and another one in Y-axis. Each circuit

consists of two bus bars and one of the

ITO conductive layers .See figure (5).

Therefore, Four-Wire technology use

two layers to create X- and Y-axis

measurements while in 5-Wire method

x-circuit and y-circuit are both on the

same layer of glass.

The bus bars are in essence broken up, producing a variety of resistor patterns in the perimeter of

the screen. These individual elements form adjacent geometric shapes consisting of low resistance

material that is screen printed directly onto the ITO substrate.

When a touch occurs. The touch point introduces a pair of voltages for X and Y direction.The X and

Y-axis data points are derived using both conductive planes . In the first phase of data collection, the

top conductive layer is electrically charged and the bottom conductive layer acts as the feedback

sending raw voltage of the touch point to the electronics ,deriving one-half of the full touch

coordinate. In the second phase, the bottom layer is electrically charged and the top layer serves to

send the voltage information to the electronics, completing the X and Y coordinate signal .See

figure(4).

As we see, Four-Wire

Technology must use the

top film to represent the

X or Y-axis depending

on the design. It is

important that the

resistance value remain

stable on both axis after

initial calibration.

frequent flexing of the

top layer upon single

locations (such as on and

off icons) will cause

mechanical damage to

the conductive cover coating changing its electrical characteristics (resistance) with use .See

figure(6).This damage will affect the accuracy of the axis that represented by the cover sheet.[MA10]

Figure 5: Four-Wire Resistive

Figure 6: Working of 4-Wire Systems

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The primary reason for this is the physical properties of the clear

conductive coating. ITO is a ceramic and, when coated onto a

flexible substrate, is therefore prone to crack if the base substrate is

deformed. If the ITO coating is cracked, the properties of the flexible

circuit will no longer allow for a linear voltage gradient to be

generated and the screen therefore becomes non-linear.

Another drawback of the 4-wire system is the fact that ITO on a

flexible substrate is affected with environmental changes, primarily

shifts in humidity and temperature because it is never fully

oxidized.It will expand and contract with changing conditions,

thereby causing changes to the initial resistance values.This change

results in what is known in the industry as “drift” to the touch point

location, which diminishes the touch screen reliability and results

permanent electrical failure of the touch screen. See figure (7).

The benefits of a 4-wire are its widespread usage, which has helped keep the cost low and prompted

numerous chip manufacturers to make electronics accessible and economical.

5.4 Five-Wire Resistive touchscreen technology:

Resistive 4-wire touch screens have long been a successful touch screen user interface for hand-held

devices. However mainstream industrial businesses such as warehousing, inventory control, retail,

hospitality and medical applications have placed new demands on the interface pushing 4-wire

resistive technology beyond its physical limit. This has prompted manufacturers to develop new and

more rugged resistive touch screens for these harsh environment applications.

Unlike Four-Wire technology that must use

two opposing layers to create X- and Y- axis

measurements, Five-Wire Technology

Utilizes the bottom substrate for both X and

Y-axis measurements. The flexible

coversheet acts only as a voltage-measuring

probe. See figure 8. This means the touch

screen continues working properly even with

non-uniformity in the cover sheet's

conductive coating. The result is an accurate,

durable and reliable touch screen that offers

drift free operation.

Electrically, the 5-wire operates by applying a voltage to two adjacent corners of the resistor pattern

while the two opposing corners are grounded. This generates a semi- linear voltage gradient across

the entire surface of the screen in one axis. The top film, which is connected to the 5th wire, is used

only as a pick-off layer and, similar to a 4-wire touch screen, the voltage that applies at the point of

actuation will apply to the entire top circuit, which corresponds directly to the point of actuation.

Figure 7: Limitation of 4-Wire

Figure 8: Five-Wire Resistive

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To determine the second coordinate, the role of two diagonally opposing corners is reversed. See

figure (9).This generates a voltage gradient in a 90o offset direction. Again, the top circuit is used

only as a voltage pick-off to take the measurement for the second touch coordinate.

Because the top film is working only as a pick-up layer, it is not required to handle any current.

Hence it can tolerate resistance changes without impacting the reliability of the touch points’

accuracy from the base layer. Any cracks or fissures induced due to misuse or prolonged actuations

therefore do not affect the screen’s accuracy. It is for this reason the 5-wire is able to withstand

temperature, humidity and mechanical stresses. [MA10]

5-wire has been the resistive solution for tough environment applications such as industrial control

modules, POS applications and Kiosks for nearly 20 years, but has been limited to d iagonal sizes of

6.4'' or larger. This diagonal limitation prevented the technology from consideration in hand-held

applications, which are typically 3.9'' in diagonal or smaller.

5.5 Four-Wire vs. Five-Wire Resistive Touchscreen Technology:

Four-Wire Technology Five-Wire Technology

Durability 1 million-touch life max

(film/glass)

35 million finger touches with no performance

degradation

Cost Lower More expensive

Image Clarity 70% 80%

Design Flexibility Not available in spherical

designs

Advanced design allows flat and spherical designs

Screen Size All sizes 6.4" or larger

Application Commercial mobile stationary applications

Table 2: Differences Between 4-wire and 5-Wire

Figure 9: Working of 5-Wire Technology

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5.6 Digital Resistive Technology: The previous explained resistive technology is

widely called Analog Resistive to distinguish from

Digital Resistive. Digital resistive uses the same

technology of analog resistive except that it is

simply a matrix of analog resistive panels in one

screen. This technology has the advantage of

Multi-Touch in addition to analog resistive

advantages, but it is more expensive. See fig (10).

5.7 Pros and Cons of Resistive touchscreen technology:

Resistive

Advantages Disadvantages Works with finger, gloves, stylus or any

non-sharp object so it can be used in hospitals and restaurants.

Relatively easy to manufacture.

Lowest-cost touch technology

Widely available

Low power consumption

Resistant to screen contaminants

Less sensitive to scratches as compared to

capacitive screens

Not durable enough.

Loss of clarity of image.

Not recommended for public locations Non-zero touch-force. Exponential cost to manufacture as screen

sizes increase

Becomes non-responsive at temperature

extreme.

Poor multi-touch capability.

Table 3: Pros & Cons of Resistive touch Technology

Main limitations of technology:

1- Not durable enough: Resistive Touch Screens

are durable and resistant to humidity and liquid

spills. But they offer limited durability because

they are susceptible to vandalism and scratched.

The surface can be easily damaged by sharp

objects and the isolating dots can also be

damaged over time degrading the accuracy of

the touches. See figure (11).

2- Poor optical quality: less light transmittance than other touchscreen types. Transmission

typically in 80% to 85%.The decrease in light transmission is the result of metallic resistive and

conductive coatings

3- Not recommended for public locations: Resistive displays are less effective in public

environments due to the degradation in image clarity and the need for periodic recalibration

caused by the breakdown of the layers of resistive film, and its susceptibility to scratching.

4- Non-zero touch force(25-50 grams pressure sensitive)

5- No multi-touch: Can’t touch with two fingers on the same square

Best Usage: Restaurants, hospitals, factories, handheld applications (phones)

Figure 10: Digital Resistive Technology

Figure 11: Life cycle of the isolating dots

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6. Capacitive Touch Technologies:

Capacitive touch panels represent the second most widely used sensing method after resistive film

touch panels. Recently, capacitive popularity has grown, as it has become one of the leading

technologies used in touch screen devices. In 2001, it began appearing in consumer devices, such as

MP3-players and smart phones. This increase in attention is likely due to the effectiveness of its

design, its use of multi-touch technology, and the popularity of Apple products using this

technology: iPod Touch, iPhone and most recently the iPad.

Capacitive touchscreen displays

rely on the electrical properties of the human body to detect

when and where on a display the user touching. See figure (12). Because of this capacitive

displays can be controlled with very light touches of a finger,

generally they cannot be used

with a mechanical stylus or a

gloved hand.

There are two types of capacitive touchscreen generally available, surface and projected, and it’s the

latter that you’ll find in Apple's iPhone and iPod. The internal structures differ between the two

types. They are both based on the fact that the application of a finger changes the capacitance in a

local region enabling the system's electronics to detect a touch and determine its position on the

screen. Comparing with resistive, capacitive systems detect changes in electrical fields but don't

rely on pressure.

6.1 projected Capacitive Touch Technology:

6.1.1 How does it work?

The design of projected capacitive touch

screens is somewhat similar to that of resistive

touch screens, in that they both utilize 2 layers

of ITO See figure (13). An XY array is formed

either by etching a single 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 the

grid. This grid projects the electric field through

the top layer of glass- hence the name projected

capacitive touch screens. See figure (14).

Because of this projection, when the user

touches the top layer of glass it “changes the

measured capacitance values of the electrodes

closest to it”. This change in capacitance is due

to the slight electric charge contained in the human body.

Figure 12: Concept of Cpacitive technology

Figure 13: Projected Capacitive Structure

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These changes in capacitance are measured and calculated as touch points in a very similar way to

resistive touch screens, by using the X and Y components.[MA10]

Actually, there are many ways to build

projected capacitive screens. On lens, on cell

and in cell designs are the most dominant.

Suppliers with the simplest designs tend to be

the most successful, since complex screens

are more expensive to build. Technical

challenges include eliminating noise so that

touch gestures can be detected more

accurately, reducing power consumption of

the displays, handling the issue of sweaty

fingers, and the need to make the devices

both thin and strong.

A projected capacitive sensor array is designed so

that a finger will interact with more than one X

sensor and more than one Y sensor at a time . See

figure (15).This enables software to accurately

determine finger position to a very fine degree

through interpolation. For example, if X-sensors

1, 2 and 3 see signals of 3 mV, 10 mV, and 7 mV,

the center of the finger is at:

[(1 × 3) + (2 × 10) + (3 × 7)] / (3 + 10 + 7) = 2.2

Figure 15: Sensing Method Of projected Capacitive

Figure 14:Working Of Projected Capacitive

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6.1.4 Mutual-capacitance vs. Self-Capacitance:

There are two approaches to determining finger position with a projected capacitive touchscreen: measuring self-capacitance and measuring mutual

capacitance. Touchscreen solutions that measure self-capacitance measure an entire row or column for capacitive change.

Self-capacitance works OK for single-touch systems,

but with multi-touch systems there is no way to resolve the positional ambiguity that results from

more than one simultaneous touch on different parts of the screen.

For example, if a user touches on the capacitive grid at locations X1, Y1 and X2, Y2, the energized

lines simply tell the chip that X1, X2, Y1, Y2 lines have all been touched. It doesn't know the combination thereof. It could be that the chip reports X1, Y2 and X2, Y1 were the touch locations. This problem is known as ghosting. See figure (16).

So, when input is one (or many) touch in self-capacitance

system output is only one capacitance value for whole panel. In contrast, in a mutual capacitance system Output

is an array of capacitance values for each X-Y intersection.

If two touches are present in a mutual capacitance system, this would be detected as (X1,Y1) and (X2,Y2),

whereas in a self-capacitance system it would be detected as (X1,X2,Y1,Y2), leaving two potential combinations of

coordinates. The self-capacitance ghosting problem is exponential and becomes impossible to solve as you transition to three or more touches. See figure (17).

A mutual capacitive array is interpreted as a complete touch surface that maintains the ability to resolve multiple touch points within each individual "small" screen. Because the capacitive coupling at each point in the matrix can be measured independently, it means that there is no

ambiguity in the reported coordinates for multiple touches. It is then technically possible to have unlimited touch recognition.

Figure 16: Self Capacitance

Figure 17: Mutual Capacitance

Table 4: Differences between Mutual-Capacitance & self-Capacitance

17

6.1.2 Projected capacitive technology advantages:

There are several benefits to using projected capacitive technology but the most important are:

1- Capacitive is very durable, because users touch the top of a glass or plastic substrate, while the

ITO layers are protected below. This makes projected sensing more accurate and repeatable than

other capacitive sensing methods. In addition, projected capacitive touchscreen Functions even

if glass is scratched or broken.

2- Projected capacitive touch screens are ''scanned'', meaning most of these screens are made up of

a matrix of rows and columns that are "read" one by one to get a reading or count. The result is

extremely precise. Scanning also has an advantage of being free of coordinate drift. This is

possible because the rows and columns are physically fixed and each measurement is made in

small area. Without the issue of coordinate drift, p-cap touch screens do not have to be

calibrated by the end-user as long as the touch screen is mounted on the same place on the

display.

3- Support multi-touch: Since projected-capacitive panels have multiple sensors, they can detect

multiple fingers simultaneously, which is impossible with some other technologies. In fact,

projective capacitance has been shown to detect up to ten fingers at the same time. This enables

exciting new applications based on multiple finger presses, including multiplayer gaming on

handheld electronics or playing a touchscreen piano.

4- If sensitivity is increased, projected capacitive can be operated with gloved fingers.

5- Projected capacitive responds to light touch. No pressure force is needed for detection.

6- High optical transmission: The capacitive system can transmit 90% of the light

7- Extreme long life time because it has no moving parts in operation.

8- Higher resolution than resistive and surface capacitive.

All these features make them ideal for harsh, industrial, or outdoor applications.

6.1.3 Projected capacitive technology drawbacks:

1- Low noise Immunity: 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.

2- Comparing with resistive, projected capacitive technology is relatively expensive: Projected

capacitive requires fine pattering, thus takes high processing cost.

3- will not react to any input device other than a finger or specially designed probe

4- Touch screens larger than 24'' (diagonal) are difficult to build.

These drawbacks can be improved or even be eliminated completely

18

6.2 Surface Capacitive Touchscreen Technology:

6.2.1 How does it work?

Surface capacitive is another form

of capacitive touch screen

technology. The primary difference

between surface capacitive and

projected capacitive is that surface

capacitive uses only one ITO

surface. See figure (18).This layer

calculates touch points using

principles that are very similar to

projected capacitive touch screens,

in that touch points are observed

by changes in capacitance if the

ITO layer in the touch screen.

However, these touch points are

measured in a very different way.

The computer measures the

change in capacitance from each corner of the ITO layer, and with these 4 separate

measurements, the X and Y coordinates of the touch point are calculated. In other words, the

touch screen system calculated the position of the touch from relative differences in charge at

each corner.

So, 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. 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.

Surface capacitive touch screens tend to be employed for applications that are large size (over

12inch), used by general public, and requiring high-quality looking, high resolution and high

durability.

6.2.2 Surface capacitive technology advantages:

1. This type of capacitive touch panel has a simpler structure than a projected capacitive touch

panel and for this reason offers lower cost.

2. Life span of more than more than 50 million touches in one location.

3. Surface capacitive technology is suitable for large size monitors.

4. Technology with fastest touch response time

5. Visibility is higher than projected capacitive because structure is only one glass layer.

Transmission typically 88% to 92%

6. Withstands contaminants and moving liquids on the screen, and continues to function over entire

touch screen area

Figure 18: Working Of Surface Capacitive

19

6.2.3 Surface capacitive technology disadvantages:

1. Poor multi-touch: it is structurally difficult to detect contact at two or more points at the same

time

2. A gloved finger, pen, stylus, or hard object will not work. As a result, it is inappropriate for use

in many applications, including medical and food preparation.

3. Scratches in the coatings can cause dead spots on the screens

4. moderately durable and has limited resolution

5. Prone to false signals from parasitic capacitive coupling.

It is therefore most often used in simple applications such as industrial controls and kiosks.

6.3 Pros and cons of capacitive touch technology:

Capacitive touch screens are very common in many consumer devices. Although there are two

different types of capacitive touch screens, their performance is very similar, with the exception

that projected capacitive touch screens are a little more accurate than surface capacitive touch

screens, but this difference is relatively negligible An important feature of this technology is its use

and application of multi-touch gestures. This is because less force is required to maintain a “touch

point”, making dragging and zooming items much easier. However, a drawback of this technology

is that you can only touch the screen with your finger. This means that stylus and gloves,

depending on their thickness, will not work with this technology. Another drawback is the cost of

the screen. These screens are more expensive than resistive touch screens. Overall, capacitive

touch screens are very effective in their current uses.

Main limitation of technology: Requires human touch, scratches in coatings cause dead spots and

Sensitive for electromagnetic interference.

21

7. SAW Touch Screen Technology: Surface Acoustic Wave touchscreen technology is widely used in applications that demand durability

and high image quality such as information directories, museum displays, training systems, gaming and

vending machines, and more. SAW technology uses an all-glass panel with no films or active layers,

giving it a higher clarity and durability than other resistive and capacitive touchscreen types.

7.1 How does it work? SAW technology uses ultrasonic waves that pass over the touch screen panel. Ultrasonic is a cyclic sound pressure wave with a frequency greater than the upper limit of the human hearing range. When

the panel is touched, a portion of the wave is absorbed and attenuated by the finger. This change in the

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

processing. See figure (19).

Actually, the surface wave system consists of pair of two transducers (one receiving and one sending)

which are placed along the x and y axes of the glass plate. The other important element of

SAW, Reflectors are also placed on the glass plate to reflect the electrical signal between the two transducers. The touch screen controller sends a 5 MHz electrical signal to the transmitting transducer,

which converts the electrical signal into ultrasonic waves. Each wave is spread

across the screen by bouncing off reflector arrays along the edges of the screen. These

mechanical waves are directed across the opposite side gather and direct the waves to the receiving transducer, which

reconverts them into an electrical signal. When the front surface of the touch screen

is touched, a portion of the energy of the acoustic wave is absorbed, thus changing

the received signal. See figure (20). The

signal is then compared to a stored reference signal, the change recognized, and a

coordinate calculated. This process happens

independently for both the X and Y-axis.

Figure 19: Surface Acoustic Wave

Figure 20: Working of SAW touch screen

21

7.2 Opportunities and Limitations of SAW Touch Technology:

Surface acoustic wave (SAW) touch panels were developed mainly to address the drawbacks of low light transmittance in resistive film and capacitive touch panels. SAW touchscreen structure has no

metallic layers on the screen, allowing for 100-percent light throughput and perfect image clarity. This makes the surface acoustic wave system better for displaying detailed graphics (both resistive

and capacitive systems have significant degradation in clarity).

Additionally, the surface glass provides better durability and scratch resistance than a capacitive

touch panel. Another advantage is that even if the surface does somehow become scratched, the panel remains sensitive to touch. Structurally, this type of panel ensures high stability and long service life, free of changes over time or deviations in position, tested to over 50 million touches at

one point. Moreover, SAW touch panels can be deployed to a curved surface.

Weak points include compatibility with only fingers and soft objects (such as gloves) that absorb ultrasound surface elastic waves, something hard like a pen won't work. Because SAW panels can be activated by a very light touch, they may react to substances which can absorb acoustic energy

like water drops and small insects on the panel creating reported touch coordinates or false/unintended touch responses. Unsurprisingly, this type of touchscreens can be adversely

affected by surface contaminants and water, making it unsuitable for many industrial or commercial applications. Acoustic absorbing contaminants can cause SAW screens to perform with decreased sensitivity or create performance issues with the touchscreen. The biggest challenges are with

contaminants near or in the reflector patterns of the touchscreen. The contaminants can cause dead spots on the screen, requiring periodic cleaning of the sensor and sometimes recalibration. So, The

SAW type screen may not perform well in extremely dirty or dusty environments.

Surface Acoustic Wave Advantages Disadvantages

Better clarity than Resistive and Capacitive

Work almost with any stylus

Very high scratch immunity can be deployed to a curved surface provides superior resolution

Must use soft object to enable touch

Surface contaminants cause dead spots

Low weather immunity (water and dust)

Cannot be completely sealed

require periodic cleaning of sensor can be activated inadvertently by dirt

Table 5: Pros & Cons of Surface Acoustic Wave Technology

Best usage: Healthcare, Retail, Point of Sale, Hospitality and banking applications or other high

Traffic indoor environments. It is not recommended to use SAW panels in open environments.

22

8. Bending Wave Touchscreen Technology:

Bending-wave touch technology is simple in concept (Figure 21). A finger touch on a glass plate generates sound waves that propagate within

the glass. These sound waves are detected with “microphones” in the form of piezoelectric

transducers bonded to the glass. Resulting signals are digitized by electronics and numerically processed to reconstruct touch positions.

Bending-wave touchscreens and SAW touch

screens have much in common. Both are acoustic touch screens that require nothing more than a glass plate in the touch input area. Bending-wave and SAW touch screens share the valued features

of high transparency, no-wear mechanism for normal usage, and stable calibration based on the speed of sound.

However, bending-wave touch screens and SAW touch screens are only distant cousins and have some significant differences. For example, bending-wave touch screens are completely unpowered

signal sources (much like a receiving radio antenna), while SAW touch screens must be powered to constantly generate waves to illuminate touches. A particularly interesting difference concerns the effect of contaminants on the touch surface. When compared to SAW, bending waves travel inside

the glass substrate. Once excited, bending waves are difficult to stop. This is because bending-wave power is distributed throughout the entire thickness of the glass plate, while SAW power is

concentrated at the surface. Therefore, bending waves are little affected by contaminants on the touch surface such as water or even the palm of the user’s hand. [KH06]

The above discussion suggests that from a scientific perspective, bending-wave touch technology has much in its favor. Why did bending- wave technology not become a dominant touch technology

many years ago? The answer lies in the engineering challenges of the associated signal processing.

While simple in concept, bending-wave signal processing provides challenging complexities in

practice. Bending waves are highly dispersive. Bending waves typically reflect many times before damping away. Reflections add complexity to time signal processing.

One approach here is to add specially designed acoustic dampers at the glass perimeter to minimize reflected waves. Another approach is to limit touch-screen designs to very large sizes so that

reflections are fewer, weaker, and more delayed in time. In this fashion, t ime of signal-processing requirements can add design requirements, complicating the sensor’s construction.

Another complication is that actual finger touches are wave sources that are not ideal – they are similar to isolated radar pings. This is clearly the case for a dragging stylus. However, what a

human perceives as a quick touch continues for a finite amount of time. This compounds the signal complexity facing time of signal processing.

However, a new approach to bending-wave touch-screen signals processing called acoustic pulse recognition (APR) makes bending-wave signal complexity a benefit rather than a problem. The APR approach may be described as acoustic fingerprinting. When a touch signal is received, no attempt is made to compute an arrival time or otherwise clean up the signal. The signal in all its complexity is simply recorded much like collecting a fingerprint. Each location on the touch-screen surface has its own distinctive fingerprint. Signal complexity is now a friend. APR represents a step forward for bending wave touch-screen technology, one that holds the promise of allowing bending-wave to become a standard technology for touch screens. [KH06]

Figure 21: Conceptual drawing of a bending-wave touch screen

23

9. Infrared Touch Screen Technology:

9.1 How it works? Infrared touch screens are primarily

used for large displays, banking

machines, and in military

applications. Infrared touch screens

are based on light-beam

interruption technology. Instead of

an overlay on the surface, a frame

surrounds the display (figure 22).

The frame has light sources, or

light emitting diodes (LEDs) on

one side and light detectors (photo

sensor) on the opposite side. The

LED and photodiode pairs create an

optical grid across the screen.

When an object touches the screen,

the invisible light beam is

interrupted, causing a drop in the

signal received by the photo sensor.

The measured photo sensor outputs

can be used to locate a touch-point

coordinate. [I07]

So, Infrared technology relies on the interruption of an infrared light grid in front of the display

screen.

9.2 Limitation and consideration of Infrared Touchscreen: Widespread adoption of infrared touchscreens has been hampered by two factors: the relatively high

cost of the technology compared to competing touch technologies and the issue of performance in

bright ambient light. This latter problem is a result of background light increasing the noise floor at

the optical sensor, sometimes to such a degree that the touchscreen LED light cannot be detected at

all, causing a temporary failure of the touch screen. This is most pronounced in direct sunlight

conditions where the sun has a very high energy distribution in the infrared region.

In addition, Contaminants can also cause false activation on the screen inside the thick border that

is required for the frame. Another major issue with infrared touchscreen is that it is susceptible to

early activation before the finger or stylus has actually touched the surface. This Early activation

ability can be used to detect Z-axis, as we will see later.

Figure 22: Working of Infrared Touch Technology

24

However, certain features of infrared touch remain desirable and represent attributes of the ideal

touchscreen, including the option to eliminate the glass or plastic overlay that most other touch

technologies require in front of the display. In many cases, this overlay is coated with an electrically

conducting transparent material such as ITO, which reduces the optical quality of the display. This

advantage of optical touchscreens is extremely important for many device and display vendors since

devices are often sold on the perceived quality of the user display experience. [I07]

Another feature of infrared touch which has been long desired is the digital nature of the sensor

output when compared to many other touch systems that rely on analog-signal processing to

determine a touch position. These competing analog systems normally require continual re-

calibration, have complex signal-processing demands (which add cost and power consumption),

demonstrate reduced accuracy and precision compared to a digital system, and have longer-term

system-failure modes due to the operating environment.

Moreover, this technology has multi- touch capability because the beams of light are never fully

obstructed by the user’s touch.

Here are the most important pros and cons of Infrared touchscreen:

INFRARED

Advantages Disadvantages

Less re-calibration is needed which results in

higher accuracy, precision and system durability.

Excellent clarity, 100% light transmission,

doesn’t require a glass or plastic overlay.

Especially suitable for large-size (over 40

inch) touch screens.

Can be operated with finger, stylus, etc.

Less prone to vandalism (scratching etc.)

Support Multi-touch.

Expensive to manufacture.

Issue of performance in bright ambient light (e.g. sunlight)

Overlay sensitive, touch can be sensed before screen touched

Pollution in the active areas inside corners of the bezel may influence system function. Cleaning from time to time resolves this

issue.

Table 6: Pros & Cons of Traditional Infrared touch Technology

Best usage: Infrared touch screens are often used in manufacturing and medical applications because they can be completely sealed and operated using any number of hard or soft materials. It is

also used in outdoor applications and Point-Of-Sale systems which can't rely on a conductor (such

as a bare finger) to activate the touchscreen.

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10. Optical Imaging Touch Technology: Optical imaging touchscreens are a touchscreen revolution. Optical imaging is a relatively new

touch screen technology that is very quickly expanding its fan base because of the scalability and

versatility it offers. It is especially feasible for large units or devices. This touch screen technology

is unlike others in that it can even recognize the size of the object touching the screen. This is

because it uses an infrared backlight and image sensors along the screen sides. When an image

touches the screen it casts a shadow and two image sensors can triangulate the position of the object

that touches the screen as well as on the size of the object based the shadow the object casts.

10.1. How it works?

Optical imaging touchscreen technology is a photonics-based technology that differs from the previous

touch technologies in that it uses optical imaging techniques to "see" and record the touch point. Optical

imaging is a simple touch screen using cameras (or image sensors) in order to detect and pinpoint touch

points (figure 23). Two cameras or more are placed around the edges (mostly the corners) of the screen,

Working together to track the movement of any object close to the surface by detecting the interruption

of an infrared light beams. The light is emitted by Infrared backlights placed in the camera's field of

view on the other sides of the screen. A simple image processing techniques are used to combine the

output of the two cameras placed. A touch shows up as a shadow and each pair of cameras can then be

triangulated to locate the touch or even measure the size of the touching object.

Figure 23: working of Camera-based touch technology

(a) The basic elements that comprise a camera-based optical touch screen are two cameras, a distributed light source around the

periphery, and a controller. (b) When possible, triangulation is accomplished using the sides of touching object, producing four

sets of coordinates for each object.

The location of the touch can be calculated using mathematical techniques based on principles of

triangulation, as also shown in Fig. The angles A and B between the top of the screen and the touch

point are found by analyzing each camera’s output and determining the pixel location of the

shadow. The distance W between the cameras is fixed, so the X-Y location of the touch point can be

calculated using the tangents of A and B as follows: Y = X*Tan (A) and Y = (W-X)* Tan (B) .

Hence we can find X from the resulting equation, X = W*Tan (B)/ [Tan (A) + Tan (B)] .

Note that this is an intentionally oversimplified explanation; real-world calculations are much more

sophisticated, taking into account factors such as lens distortion and sensor skew.

26

10.2. Pros and Cons of camera-based technology:

Optical imaging touchscreen technology revolutionizes the way we interface with computer technology. Unlike many touch screen displays, the entire screen, corners included, is sensitive to

the touch. This technology uses optical components. No surface coatings are used on the screens - hence images are kept crystal clear. Any method can be used to touch the screen: a finger, a gloved

hand or any pointer. Only a light touch is required. Optical imaging technology provides touch sensitivity over the whole screen, including the corners.

By using image sensors at two corners of the screen, Optical imaging Touch “sees” the touching object from two angles. The result is extreme accuracy, with no contact pressure required. In addition,

scratches on the touch surface will not affect the touch screen operation. No special coatings and films

are needed—there’s nothing to scratch, wear out, or cloud the display image. The screen can be sealed

against dirt, dust, and moisture, ideal for heavily used kiosks in public areas .

Camera-based Optical touch is also Multi-touch capable. It accommodates multiple touch points with exceptional precision. You can touch the screen anywhere, with anything like a finger, a pen, a

credit card. Even the lightest touch will be registered. Annotations are fast and precise.

In addition, it is easily to mount an overlay touch onto

a standard LCD or plasma monitor, converting it into a fully functional, interactive touch screen (figure 24).

The overlay uses a robust design to provide touch solutions suitable for high- traffic, public environments. This model connects through a plug-

and-play HID-compliant USB interface for power + connectivity. Easily turn any large Plasma or LCD

into an interactive touch screen. The system integrator or end user can install it over a monitor, without the need to open the display's enclosure and possibly void

warranties. This advantage makes touch ability more dynamic. [I07]

Optical imaging provides a solution without calibration drift. Once the touch screen has been

calibrated it does not require any further adjustment. This means virtually zero maintenance costs. Optical

touch typically is found in large format displays and enjoys popularity with digital signage applications. Optical touch is the cheapest choice for large format screens.

Optical Imaging

Advantages Disadvantages

100% image clarity.

Cost effective for large displays

No calibration drifts.

Operation unaffected by screen scratching.

Easy to manufacture.

Can be retrospectively incorporated into existing non-touch screen.

Can use anything to create the touch.

Ambient light can affect the systems performance.

The Profile of the frame is typically high.

Limited to large sizes.

Table7: Benefits and Drawbacks of Optical Imaging touch

Figure 24: Camera-based overlay can easily convert any LCD screen into touchscreen

27

High levels (direct sunlight) of ambient light can affect the systems performance and result in

missed touch or unintended touches. Direct sunlight on the camera lens can disrupt the camera's

ability to accurately detect touch response. Optical-based technology is also subject to the effects of

on-screen contaminants. If the camera view is blocked by an object or contaminant on the touch

surface then the screen may not be able to resolve touch points elsewhere on the screen, especially

in the vicinity of the obstruction.

10.3. Future of Camera based touchscreen technology: Optical camera-based touch’s strongest penetration has been in the Windows 7 desktop space.

Competitive touch technologies in this space are surface acoustic wave (SAW) and analog multi-

touch resistive (AMR). Neither of these technologies currently has more than a few percent market

share in the desktop space. Projected capacitive, the newest entry in the desktop space, entered the

market in the second half of 2010. Camera-based touch’s applications in the large format space are

found in four main applications as follows:

- Interactive information kiosks, such as way finders and directories.

- Digital signage, in both commerce and branding environments.

- Interactive whiteboards in education and training, in both schools and businesses.

- Conference rooms.

The primary competitive touch technology in the large-format space is traditional infrared, although

iSuppli forecasts that optical touch’s penetration in large-format applications will be almost double

(187%) that of traditional infrared by 2013 (figure 25).

“Camera-based optical touch offers high optical performance, robustness and scalability, and is a

very strong candidate for the signage and professional market. In addition, its cost-effective scaling

is an advantage against competing technologies such as IR.” [G10]

Figure 25: The Future of Optical Imaging Touch tech.

28

11. Comparison study: Every single one of the different touch technologies has its own strengths and weaknesses and is

therefore used in very different applications. In the end of this study you will find that there is no

perfect touch technology.

11.1. Light Transmittance:

The resistive system, due to its metallic coated layers, decreases light transmittance and the image is

not optimally clear. The capacitive system also reduces the amount of transmitted light, 90% as

compared to 75% in resistive, again due to its metallic coated capacitive layer. In the Acoustic and

the optical systems the ~100% transmission of light is accomplished due to the lack of metallic

layers such as resistive and capacitive systems.

11.2 The durability: Capacitive and resistive systems are sensitive to scratches which can produce errors. The screen

durability of the surface acoustic wave and the optical systems is such that razor blades can be used

to remove paint on the display surface.

Environmental elements can also impact the durability of the touch screen comp uter displays. If the

display systems are to be located outside a building, the presence of water can be a critical issue

especially in SAW technology.

11.3 Calibration Stability: In resistive touch screens, due to the deformation and warping of the ITO layer, the screens

performance will be changed. This change creates a need to recalibrate the screen. This problem, however, is not found in capacitive touch screens. This is because the ITO layers are less susceptible to damage. Additionally, this is capable “because the system can self-calibrate for

environmental changes and is better able to adapt to environmental issues than resistive technology”.

Infrared touch-screen calibration is very stable because the physical location of the LEDs and phototransistors define the geometry of the infrared beams. This difference has a large impact on

the use of each of the devices. Since capacitive and infrared devices do not need to be calibrated, they are more accurate than resistive devices after some wear. This d ifference between capacitive

and resistive also increases because the ITO layers in resistive devices deteriorate over time. Capacitive touch screens are, therefore, more accurate and more durable than resistive touch screens.

11.4 Stylus Flexibility: Another difference between the types of touch screens is the type of input devices allowed. In both

resistive and optical systems, you can use nearly any object to create a touch point. The only

limitation on resistive systems is that the object needs to be somewhat pointed while. This means

that these touch screens allow for the use of fingers or a stylus. Surface acoustic touch panels can be

activated by a finger or any soft object like gloves in surface acoustic systems stylus mustn't have

hard surface. This is a great benefit over capacitive touch screens, where a user can only use a

finger or an object made up of conductive material to create touch points. Capacitive touchscreen is

not responsive to stylus, gloves or other object. The flexibility of using a stylus or finger allows for

greater accuracy, and also allows the technology to be used in varied ways.

29

11.5 Size: Infrared and optical imaging touch screens are by far the biggest of the touch screen technologies.

The size of resistive and capacitive touch screens is relatively similar, due to the similar nature of

their technologies. While resistive and capacitive screens have the potential to be large, they do not

perform as well as the optical technologies. This is because optical technologies uses sets of

infrared LEDs and either cameras or sensors to detect the changes. Having a large capacitive or

resistive system would require a large amount of wire throughout the screen; wires of that size

would increase the chance for malfunction in detection, as well as wear and tear.

11.6 Applications:

Optical touch screens are best suited to devices like the Microsoft Surface, which require a very

large touch screen. Capacitive touch screens are best suited for high end, portable electronic

devices, and devices that need to perform consistently in many conditions. This is because of its

durability, accuracy, multi- touch support and ease, and its aesthetically pleasing appearance.

Finally, resistive touch screens are best suited for mobile applications, in which conditions will be

consistent.

11.7 Cost:

One area where resistive screens win out is on price, since capacitive screens (plus their associated

controller chips and other trimmings) usually cost around half as much again as their resistive

counterparts. Capacitive touch screens are more expensive than resistive touch screens because the

systems of circuitry and measurement are more complex. This isn’t too significant in a high-end

smart phone where the margins tend to be pretty large, but it becomes an issue for entry- level

devices. SAW are more expensive than resistive and capacitive touch screens. But infrared are the

most expensive. In large format touch displays optical imaging is the simplest for manufacture

hence it is the cheapest.

11.8 TOUCHSCREEN RESOLUTION

The resolution, or number of touch active points on the touchscreen, affects the level of pointing precision and selection errors. For example, a capacitive screen has a touch resolution of 256 x 256

and an infrared screen has a resolution of 25 x 40 due to limitations on the number of light beams that can be placed around the screens. Therefore, a higher resolution screen provides additional touch points allowing greater pointing precision because the software can average all the points that

have been touched and there are less selection errors as touch points are mapped more easily to the targets on the display.

31

12. Practical Guide to determine which type is your touchscreen:

When encountering infrared, resistive, surface wave and capacitive touch screens during travel and daily life, the curious technologist can quickly determine the touch-screen type. Simple experiments

reveal much about the basic touch-detection mechanisms of mainstream touch technologies. Infrared: If a light brush with a piece of tissue paper is sufficient to trigger a touch, it is likely an infrared touch screen.

Resistive: If a poke with a toothpick activates a touch screen that is not an infrared touch screen, it is a resistive touch screen. Resistive touch screens are activated by sufficient pressure to close an air

gap between a plastic membrane and an underlying substrate such as a glass plate. SAW: If a touch screen is activated by the eraser end of a pencil, and it is not an infrared or resistive touch screen, it is in all probability a surface-wave touch screen.

Capacitive: If a touch screen cannot be activated by a firm touch with the eraser end of a pencil, it is a capacitive touch screen.

4-WIRE 5-WIRE Projected Surface cap SAW

Infrared Camera

Type Surface Technique (Electrical) Surface Technique (Electrical) Edge (Acoustic) Edge Technique (Optical)

Technology Pressure to switch on Electrostatic field Ultrasonic

wave Light interruption

Light transmittance 70% 75-88% >88% 88-93% 90 - 92% 92-99% 92-100%

Resolution Moderated Moderated High High High Low Moderated

SIZE (inch) 1.7" to 24" 10.4" to 24" 2.8" to 10.4 6.4” to 32” 8” to 30” 8" to 150" >12"

COST Lowest Moderate LOW Moderate HIGH Highest LOW

Life Expectancy >1 million >35 million >100 million >50 million >50 million Very Long term reliability

Stylus Flexibility Anything Anything Only Conductive Must be Soft Anything Anything

Calibration stability Low Moderate Moderate Low Lowest High Highest

Multi-Touch NO NO >10 NO 2 2 5

Overlay needed YES YES YES YES NO NO NO

Contamination HIGH Best HIGH High Low Moderate Moderate

Scratch Immunity LOW Moderate Moderate LOW HIGH HIGH HIGH

Weather Immunity LOW HIGH Moderate Moderate LOWEST HIGHEST HIGH

Sunlight Readability Moderate Moderate HIGH HIGH HIGH LOW LOW

Measurement Voltage Voltage Capacitance Current Time delay Absence of light

Response Time <10 ms <15 ms <15 ms <15 ms 10 ms <20ms 9-22ms

Activation Force 10-100 g 10-100 g Forceless Forceless 10-100 g Forceless Forceless

Operating temperature -10 to 60°C -10 to +60°C -20 to +70°C -20 to +50°C -30 to +50°C

Power Consumption 5V DV 5V DV DC 6V DC 6V 12V DC 5V DV 5V DV

Commercial example HTC

Diamond

-- The iPhone -- Lenevo PC Nexio 42" HP TouchSmart

Major advantage Low cost Any stylus Multi-touch -- High clarity Durability Scalability

Major Flaw Low visibility High cost Finger only High drift Delicate Ambient light Profile height

Table 7: A brief Comparsion between different touch technologies

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13. Multi Touch Technology: Touch technology is intuitive—simply touch the screen to get what you want. Multi-touch takes

the experience to the next level. Multi-touch allows you to use more than one finger (or any

object) to stretch, rotate, or shrink an object, scroll through menus, and efficiently operate any

software program. Multi-touch goes beyond the capabilities of any traditional pointing device,

allowing you to tap into the potential of this cutting edge technology.

“Multi-touch technology has been around since early research at the University of Toronto in

1982”. The uses of this technology are very vast, allowing for greater human-computer interaction.

As multi- touch functionality grows in popularity, more applications become available to take

advantage of its capabilities. In addition to applications for PCs and kiosks, multi- touch is

especially well-suited for entertainment and multimedia programs. Multi-touch technology also

encourages working together especially with Large-format displays which allow people to

collaborate more efficiently, and multi-touch makes these systems even more intuitive and natural.

13.1. Why Multi-Touch Has Become So Important? 1. Apple: Apple established multi-touch as a “must-have” for coolness. The result is that people of all

ages expect every display they see to be touchable with multiple fingers

2. Gaming: Gaming is a natural for multi-touch.

3. Unintended touches: One of the major values of multi-touch is to allow the system to ignore

unintended touches (pa lm rejection, grip suppression, etc.). As desktop screens become more

horizontal (recline) this will become even more important.

4. Multi-user collaboration: When two people want to collaborate on a large screen (e.g. a student and

teacher on an interactive “whiteboard” LCD), multi-touch is essential.

13.2. How Many Touches Are Enough? The industry has multiple answers: Microsoft has settled on 5 touches for Win8; they wanted 10 at

first. The p-cap touchscreen suppliers under 30” either say “10” or “as many as possible” (e.g.,

3M’s p-cap supports 60+ touches). The large-format touchscreen suppliers say that 40 is enough.

The answer actually depends on the application:

For a small mobile device, 2-5 (one hand) are enough

For a single-user app on any device it’s hard to see why more than 10 (two hands) are needed

For a multi-user app, it depends: For a 55- inch gaming table, 40 (8 hands) is not unreasonable.

For a 65-inch interactive “whiteboard” LCD, 20 (4 hands) is probably enough, although an argument can be made for 40

An important feature of capacitive touch screens is their ability to recognize and calculate multiple

touch points at one time. This technology is traditionally associated with capacitive touch screens, but is

not limited to this technology. It can also be found in optical touch screens and is beginning to appear in

resistive touch screens. Currently, multi-touch technology is being used with a purpose similar to the

function keys (Control, Alt, Option, Command, etc.) on a standard keyboard. By adopting these

functions, the user is able to complete the same tasks as before, but with one hand. With advances in

hardware, multi touch will allow multiple users to access the same device simultaneously, like the

Microsoft Surface’s capability of 300 plus touches. While the hardware is available to create such

devices, software implementation is holding back the growth of multi touch.

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14. Cheek check and Z-axis: Cheek check:

Most controllers are capable of sending a message indicating when a

large number of locations are being touched at the same time. On stand-

alone devices, attribute is customarily used to determine the phone is

next to the face or the device has been put away in a pocket –signaling

that the touches to the screen should be ignored (figure 26).

Z-axis:

Another attribute of some touch screen technologies is that the touch screen does not actually need

to be touched to be activated. The touch screen's level of sensitivity can be controlled by

electronics. In most cases, the designer will require a physical touch to activate a coordinate.

However, the sensitivity can be increased, adding what is sometimes called a Z-axis or Pre-touch,

so that the simple placement of a hand near the touch screen can be detected.

15. Touch Screen OS: While Windows 7 has been a major PC success, the Windows Phone remains a distant runner-up

compared to iOS and Android. Windows tablets running 7 have been largely ignored. Windows 8 is

Microsoft’s answer to the touchscreen revolution.

During Microsoft’s Windows 8 launch event, the company paraded a variety of flashy new devices

in front of us, and almost all of them featured a touchscreen. We’ve known for a while that

Microsoft built Windows 8 optimized for touchscreens.

Windows 8 looks really exciting, but users told that extensive use on a non-touch laptop is

frustrating because the OS is always encouraging you to touch the screen. This is not only bad news

for anyone upgrading an older laptop, but also for people who work more efficiently using the track

pad and keyboard.

Basic Screen specification requirements for win8 Touch OS:

- Minimum of 5 simultaneous touches

- Respond to first touch in < 25 ms

- Subsequent touches must be < 15 ms at 100 Hz for all touches

- Pixel-level (< 1 mm) accuracy, including edges and corners

- No jitter when stationary; < 1 mm when moving 10 mm

- Finger separation >= 12 mm horizontal/vertical, 15 mm diagonal

- Pre-touch < 0.5 mm

Figure 26: Ignored Touch

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16. Interaction: For now, the latest developments in touch screen technology include what is considered as an

interactive touch screen—it is perceived that the screen shapes itself allowing a user to click a

button. This technology will change the way we consume, learn and interact with each other.

Devices that were designed to make our lives easier to control now appear to be controlling us. The

proliferation of technology and our reliance on it is now becoming a familiar part of modern life.

Many people welcome the intrusion as it brings with it unprecedented levels of social interactions,

entertainment and other things that enrich us. But many owners of smartphones and tablets appear

to be inextricably attached to their devices and this attachment permeates their entire home life; not

even time spent with their nearest-and-dearest can break the eye-to-screen bond. This is a

significant social change, this is the touchscreen life.

One definition of sustainability is the improvement of the quality of life by making life more

enjoyable and less burdensome. Touch screen technology fits within this definition very well.

Touch screen devices make life more enjoyable by creating a fun and intuitive user interface. This

is a reason that the iPhone, iPod Touch, and similar devices are so successful. By allowing the user

to operate the device in many different ways, the devices are more versatile and create a better

interface for many applications. With a better interface, the devices become more enjoyable to use,

and allow for other applications of the device. Sustainability also pertains to making life less

burdensome.

Touch screens are very sustainable because of the vast amount of applications that can be done on

one device. This can be seen very easily in the iPhone and Microsoft Surface. Before the iPhone,

many people carried around a cell phone, iPod, and PDA. With the implementation of a versatile

touch screen, the iPhone and other touch screen devices are able to do the tasks of all three of these

devices. This is because of the adaptability of the interface. The Microsoft Surface is similar to the

iPhone because it makes many applications available to the user. Users are able to transfer contact

information, calendars, pictures, etc. with just the touch of a finger. The sustainability aspects of

both of these devices show the importance of these technologies.

With the proliferation of low-cost, large format displays, many customers are demanding to make

these displays interactive. Typically large-format displays range from 32 inches up to 82 inches.

Public displays are intended for out-of-home viewing by multiple people. Touchscreen

manufacturers have responded to meet this need in different ways. Some have chosen to develop

purpose-built technologies specifically designed for large-format displays, while others have scaled

up existing technologies to accommodate these larger sizes.

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17. Market Trends:

17.1. The Recent History: Touchscreens are the hottest thing in user interfaces for everything from phones to laptops to tablet

computers such as the iPad. The late 2000s often attribute Apple as responsible for the touchscreen.

The company did not invent the touchscreen, but innovated it. The technology became more useful

and commercially available to a widespread audience. In 2007, Apple released the most innovated

touchscreen technology anyone had yet seen. The iPhone interface is completely touch-based,

including the notorious virtual keyboard. Apple's line of iPhones led to other devices like the iPod

Touch and the iPad .

After shaking the mobile industry with the iPhone, the late 2000s saw a race among tech

competitors to make the best tablet. Apple, Microsoft, Amazon, Samsung, Google and other giants

have all made several devices with touchscreen technology.

Sales of laptops are falling, but sales of touchscreen devices, such as tablets and smartphones, are

rising. Touch screens have now been widely incorporated into a huge number of everyday devices.

They will continue to be a growing area for innovation in electronic systems. Touchscreens have

turned into one of the fastest-growing display markets since Apple launched the iPhone in 2007.

They’re now appearing on all sorts of devices, and the touchscreen market is growing 10 times

faster than the overall display market. Mobile phones are the largest volume market for touchscreen

panels; over 40% of mobile phones use touchscreens in 2012, with nearly complete market share

within 10 years. [KK11]

17.2. Mainstream technologies: The current market leading technology is projected

capacitive touch (figure 27). Projected capacitive growth

has been explosive since being popularized by Apple in

2007, and many tablet PCs manufacturers have adopted

it. This technology became the top touch solution in

2010 in terms of revenue. Due to the pressure to reduce

cost and materials, conventional add-on type projected

capacitive touch is evolving in three directions: sensor-

on-cover, on-cell, and in-cell. Today, the biggest market

for projected capacitive touch screens is in mobile and

smart phones, but tablets are right behind and quickly

gaining momentum. [C12]

Resistive technology is widely used in small size (> 10

inch) healthcare and hospitality applications as well as

high-volume retail environments. Embedded touch

technology is currently the leading emerging touch

technology and on-cell technology in particular has the

biggest potential for small size consumer electronics, but

is also suitable for medium size applications.

Figure 27: Touch screen Modules distribution

35

Resistive is shrinking in units and revenue being replaced by projected capacitive in most consumer applications although it is still significant in commercial applications, especially POS and industrial. Surface capacitive has leveled off and will start to shrink. It will be an irrelevant,

obsolete technology in 5-10 years.

Infrared (IR) and surface acoustic wave (SAW) touch technologies are mainly relevant for specialized touch devices, such as ATMs and banking and financial applications, as well as eBooks and mobile phones to some extent.

Optical- imaging touchscreen technology can be very cost-effective in large sizes (>10 in.) “By 2013, optical imaging will emerge as the leading single touch-screen technology in the signage and

professional display market, accounting for 25.6 percent of worldwide unit shipments. The dominant use for optical imaging touch-screen technology will be in conference rooms.”[G10]

“Capacity in 2010 and 2011 was slightly higher -- 13% -- than demand, but this level of oversupply is healthy, given the rapid pace of growth in the touch industry,” said Jennifer Colegrove, Ph.D.,

VP, emerging display technologies for NPD DisplaySearch. “However, the glut is expected to more than double in 2012, to 27%, causing touch sensor prices to reduce rapidly. The oversupply will

also force touch suppliers to move to larger size applications to utilize capacity, such as notebook and all- in-one PCs, ATM/finance and point of informa tion,” Dr. Colegrove noted.

17.3. 2013 Trends: The market for touch screens is already large

(figure 29). Only a few years ago the true mass

consumer market use of touch screens was

conditioned by Apple's adoption of projected

capacitive touch screen technology for the

iPhone in 2007. After this other global players,

such as Samsung and LG Electronics, also

started to use touch technology for their wide

range of products. Today, touch screen

interfaces are becoming increasingly common

in mobile consumer devices (figure 28).

Leading the touch screen technology market

are high-end mobile consumer-electronic

devices, such as smart phones and tablets.[C12]

In terms of shipments of touch screen panels

used in handsets, resistive touch screen

shipments are expected to decrease in 2013 due

to Nokia, one of the largest users of the

technology, using more projected capacitive touch screen technology in its handsets.

In December 2012 DIGITIMES Research forecasted that Global touch screen shipments are

expected to reach 1.75 billion units in 2013, up 17.2% on year. Among the shipments,

approximately 1.28 billion or 73% are estimated to be for handsets (including smartphones), which

will be a 14.2% on-year increase. Shipments for touch screens used in tablets meanwhile are

expected to reach 233 million units, up 38.2% on year, while touch screens for PCs are expected to

reach 26.33 million in 2013, up 251.3% on year. [J12]

Figure 28: Market Size for touch modules by device size in 2012

36

The latest market research expects over 800 million smartphones sold (figure 30). PCs are still one

of the most successful classes of devices in the ICT sector. Next year could be approximately 390

million new units – including 235,500,000 155,700,000 notebooks and desktop devices - go to the

customers. Sales of tablets will increase to nearly 166 million. A significant proportion of flat

computer will account for seven- inch devices. E-readers remain a niche product with a certain

connotation, According to a recent estimate, the sales in 2013 amounted to around 18 million units,

According to iSuppli Research.

The smartphone boom shows no signs of slowing down. IDC’s analysts are predicting 800 million

smartphones to be shipped in 2013. The tablet market is expected to keep its momentum too, with

7-inch tablets taking a significant share of the market.

Tablet PC is a fast-growing application for

touch screens. Shipments tripled in 2010 and

reached 79.6 million in 2011. Growth

continues to be strong, with NPD

DisplaySearch forecasting more than 130

million touch screens for tablet PCs in 2012,

and more than 190 million in 2013. Revenues

for touch screens in tablet PCs are expected to

grow by more than $3 billion in 2013,While

total touch revenues are about 17 billion US$

in 2013(fig 29). NPD DisplaySearch forecasts

touch screen penetration on notebook PCs will

increase from 2% in 2011 to about 8% in 2013 .[S12]

Figure 29: Touch screen shipment forecast in 2013

Figure 29: Global Touch screen market Revenues

37

17.4. What is Next? “There are lots of opportunities in the touchscreen market,” said Jennifer Colegrove, vice president of emerging display technology at Display Search. “The market is doubling this year (2011) and will double

again by 2017.” [SP10]

Apart from adding touch functionality to more and more commercial consumer devices, the next big topic and opportunity will be the replacement of indium tin oxide (ITO), especially in projected

capacitive and resistive touch technologies; the two mainstream technologies. Today, half of the costs of projected capacitive touch screen modules come from the ITO sensor. The replacement of this widely used ITO sensor electrode material will not only change the game entirely in terms of

costs, but also open the gate to bendable, rollable and stretchable electronics with touch functionality.

The touch screen market is expected to triple in 2022 of the next decade [C12]. The next big markets for touch screens are eBooks, (mobile) game consoles, car displays and navigation devices as well

as digital cameras for small to medium size displays. Bigger touch screens over 10 inches can be increasingly found in laptops and PC monitors as well as other screens and TVs. “Demand is

growing for thinner, light weight, and lower cost touch panels and devices. In addition, we see strong touch screen growth over the next several years in larger display applications” noted Jennifer Colegrove, PhD, Vice President of Emerging Display Technologies at NPD DisplaySearch.

Over the next few years, adoption by all- in-one PCs and automobile monitors are expected to be leading contributors to touch screen market growth [S12]. Touch technologies with high

transmittance, low power consumption, multi-touch, or gesture recognition will benefit the most from these applications. NPD DisplaySearch forecasts that sensor on cover will surpass other add-

on type projected capacitive touch and become the leading touch technology in 2015 in terms of revenue. In addition, NPD DisplaySearch forecasts strong touch screen growth over the next several years driven by demand in larger display applications.

In ten years from now, projected capacitive touch technology will continue to lead the market as

panel costs are decreasing .Due to extremely low cost, resistive touch technology will continue to lead the market in price sensitive applications that need precise touch .The rise of embedded touch technology, currently the leading emerging touch technology, will be conditioned by more and

more LCD manufacturers entering the field.

While displays aren’t nearly as attractive as the tablets and smartphones they go into, they’re an interesting market to observe because they show what happens when the entire manufacturing world pursues a hot trend. Sometimes the window for making profits in such a market is only open

for a nanosecond. Of course, the market is fraught with risks, as any commodity hardware market is. If there’s a

slowdown in demand, or a new technology emerges, the existing suppliers could face a big drop in demand. For example, Makers of resistive screens have moved from

64 to 91 in the past two years, but the size of that market has shrunk.

The future of touch surface is touchscreen video projectors (figure 30). In a restaurant, for e.g., you can

place your order using the surface of the table as the touch interface, instead of using a touch screen laptop. The ability to transform any surface in a touchscreen

means lower costs, making the technology more cost effective. [MA10]

Figure 30: Touchscreen Projectors

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18. Conclusion:

Through this seminar we have tried to present currently existing and trending solutions for

touchscreen technology. As you can see, there are a lot of existing solutions, b ut none of them is the

best. We have shown each of these technologies in less or more details, and also tried to make

differences between them understandable and obvious. Hope we have succeeded doing that, and

also, succeeded in making awareness of these technologies larger.

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19. References:

[MA10]: Mudit, B.; Anand, B.: Comparative Study of Various Touchscreen Technologies.

International Journal of Computer Applications, Vol. 6 – No.8, pp.0975 – 8887, September 2010.

[KK11]: Ken, P.; Keunjong, K.: Touch Panel Overweight Maintain. Hundai Research Industry Analysis, pp.1– 18, Korea, November 24, 2011.

[G10]: Geoff, W.: Touch On the Consumer Desktop and In Large-Format. NextWindow FPD International 2010, pp.1– 41, 2010.

[J12]: Jason Y., DIGITIMES Research, Taipei, Friday 28 December 2012.

[KH06]: Ken, N.; Henry, D.: Information Display. Acoustic Pulse Recognition Enters Touch-Screen Market, pp.22– 25, 12/2006.

[I07]: Ian, M.: Information Display. An Overview of Optical-Touch Technologies, pp.26– 30, 12/2007. [C12]: Cathleen Thiele: Touchscreen market to reach $14 billion in 2012. http://www.convertingquarterly.com/industry-news/articles/id/4067/touchscreen-market-to-reach-14-billion-in-2012.aspx ,March 23 2012 [SP10]: San J., Paul S.: Touch screen Market Update. Display Research, pp. 1-20, Nov 10, 2010

Questions: MHSH2025@Gmail.com