Whether it’s on a mobile device, tablet, or medical
device, technology in the field of electronics give
tremendous revolution in passed decades.
One of the revolution can be easily seen in screen that
plays an important role in making devices highly usable as
it helps in direct interaction of user with the device but there
exist difficulty in using input devices such as a mouse or
keyboard (key pad).
Now the scenario has changed and we have a new
technology in screen called Touch Screen Technology
which provide a natural interface with the device
This technology means as simple as its name that is Touch
the Screen and Activate Instructions (TSAI). Instead of the
keyboard (keypad) or mouse we can operate or stimulate
an instruction or command by touching on the screen
First touch screen to be a capacitive touch screen invented
by E.A. Johnson at the Royal Radar
Establishment, Malvern, UK, around 1965 – 1967
The nineties introduced smart phones and handhelds
with touch screen technology. In 1993, Apple released the
Newton PDA, equipped with handwriting recognition; and
IBM released the first smart phone called Simon, which
featured a calendar, note pad, and fax function, and a touch
screen interface that allowed users to dial phone numbers.
In 2002, Microsoft introduced the Windows XP Tablet edition
and started its entry into touch technology
Touch Screen – Construction & working
The key goals (while making touch ) are to recognize one or
more fingers touching a display, to interpret the command that
this represents, and to communicate the command to the
In the most popular techniques, there are typically four layers:
Top polyester coated with a transparent metallic conductive
coating on the bottom
Glass layer coated with a transparent metallic conductive
coating on the top
Adhesive layer on the backside of the glass for mounting.
There are three components used in touch screen technology for its working
Touch Sensor:- A touch screen sensor is a clear glass panel with a touch
Controller:- The controller, is the hardware that connects between the touch sensor and the
Software:- Software contains drivers that allows the touchscreen and computer to work
responsive surface. The touch sensor/panel is placed over a display screen so that the
responsive area of the panel covers the viewable area of the video screen. The sensor
generally has an electrical current or signal going through it and touching the screen causes
a voltage or signal change. This voltage change is used to determine the location of the touch
to the screen.
PC or other devices. It converts the voltage changes on the sensor into signals and
translates it into information that PC or other devices can understand. Controller is usually
installed inside the monitor (or screen of other devices) or it is housed in a plastic case for
external touch addons/overlays
together and tells the computer, smartphone, game device, etc, what's happening on the
sensor and the information coming from the controller. Who's touching what where; and
allows the computer or smart phone to react accordingly.
Types of Touch
Single Touch occurs when a finger or stylus creates a touch event
on the surface of a touch sensor or within a touch field so it is
detected by the touch controller and the application can determine
the X,Y coordinates of the touch event.
The term "multi-touch" is now in common use to
describe any touch screen that can recognize
more than one point of contact; in effect the use
of two or more fingers simultaneously
Resistive Touch Screen
Resistive LCD touchscreen monitors rely on touch overlay, which is
composed of a flexible top layer and a rigid bottom layer separated by
insulating dots, attached to a touchscreen controller.
The inside surface of each of the two layers is coated with a transparent
metal oxide coating of Indium Tin Oxide (ITO) that facilitates a gradient
across each layer when voltage is applied.
Pressing the flexible top sheet creates electrical contact between the
resistive layers, producing a switch closing in the circuit. The control
electronics alternate voltage between the layers and pass
the resulting X and Y touch coordinates to the touchscreen Controller.
The touchscreen controller data is then passed on to the computer
operating system for processing.
Technology is divided into two
• Four-wire resistive technology :- It uses both
the upper and lower layers in the touchscreen
"sandwich" to determine the X and Y coordinates.
Typically constructed with uniform resistive
coatings of ITO on the inner sides of the layers
and silver buss bars along the edges, the
combination sets up lines of equal potential in
both X and Y.
Four wire Resistive Touch screen
In the illustration below, the
controller first applies 5V to the
back layer. Upon touch, it probes
the analog voltage with the
coversheet, reading 2.5V, which
represents a left-right position or
It then flips the process, applying
5V to the coversheet, and probes
from the back layer to calculate
an up-down position or Y axis.
At any time, only three of the four
wires are in use.
5-Wire Resistive Touchscreen
In the five-wire design, one wire goes to the
coversheet (E) which serves as the voltage
probe for X and Y.
Four wires go to corners of the back glass layer
(A, B, C, and D). The controller first applies 5V
to corners A and B and grounds C and
D, causing voltage to flow uniformly across the
screen from the top to the bottom.
Upon touch, it reads the Y voltage from the
coversheet at E. Then the controller applies 5V
to corners A and C and grounds B and D, and
reads the X voltage from E again.
Reduced optical clarity
Activated by any stylus or finger or
Polyester surface can be
High touch point resolution
Low cost sensors & power requirements
Not affected by dust or water
Requires bare finger or capacitive
Scratch can affect operation
Good optical clarity
Capacitive Touch Screen
A capacitive touch screen panel is coated with a material
(metal oxide ) that stores electrical charges. When the
panel is touched, a small amount of charge is drawn to
the point of contact.
Circuits located at each corner of the panel measure the
charge and send the information to the controller for
Capacitive touch screen panels must be touched with a
finger unlike resistive and surface wave panels that can
use fingers and stylus.
Surface capacitive technology
In this technology, only one side of the insulator is coated with a conductive layer. A
small voltage is applied to the layer, resulting in a uniform electrostatic field. When
touches 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.
it is moderately durable, has limited resolution and is prone to false signals from
parasitic capacitive coupling. It is therefore most often used in simple applications such
as industrial controls and kiosks
Projected capacitive technology
Projected Capacitive Touch (PCT) technology is a capacitive technology which permits
more accurate and flexible operation, by etching the conductive layer. An X-Y grid is
formed. A finger on a grid of conductive traces changes the capacitance of the nearest
traces. This change in trace capacitance is measured and finger position is computed.
The use of an X-Y grid permits a higher resolution than resistive technology. Projected
capacitive touch screens are clear, durable, solid state, scratch resistant and allow
gloved hand use.
Because of its high optical clarity and
accuracy, acoustic wave technology is typically
used in kiosk applications.
Acoustic wave touch screens use transducers
mounted at the edge of a glass overlay to emit
ultrasonic sound waves along two sides. These
waves are reflected across the surface of the glass
and received by sensors. A finger or other soft
tipped stylus absorbs some of the acoustic energy
and the controller measures the amplitude change
of the wave to determine touch location.
Infrared touch screens are primarily used for large
displays, banking machines, and in military
Infrared touch screens are based on light-beam
interruption technology. Instead of an overlay on the
surface, a frame surrounds the display. The frame has
light sources, or light emitting diodes (LEDs) on one
side and light detectors on the opposite side, creating
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 sensors.
Optical Touch Screens
Optical touch screen technology is ideal for large
LCD and plasma displays up to 100" diagonal.
Optical touch screen technology uses two line
scanning cameras located at the corners of the screen.
The cameras track the movement of any object close
to the surface by detecting the interruption of an infrared light source.
The light is emitted in a plane across the surface of the
screen and can be either active (infra-red LED) or
passive (special reflective surfaces).
Introduced in 2002 by 3M, this system uses sensors to detect
the Piezoelectricity in the glass that occurs due to a touch.
Complex algorithms then interpret this information and provide the
actual location of the touch.
The technology claims to be unaffected by dust and other outside
elements, including scratches.
Since there is no need for additional elements on screen, it also
claims to provide excellent optical clarity.
Also, since mechanical vibrations are used to detect a touch
event, any object can be used to generate these events, including
fingers and stylus.
A downside is that after the initial touch the system cannot detect a
Advantages & Disadvantages of other touch screens
Good optical clarity
excellent optical clarity
unaffected by dust
Durable glass front
mechanical vibrations are
used to detect a touch
Requires finger or sound absorbing stylus
Difficult to industrialize
Signal affected by surface liquids
Prone to scratches easily
Public Information Displays
trade show displays,
Retail and Restaurant Systems
valuable counter space can be saved
seating, reservation systems
Control and Automation Systems
In real-time by simply touching the screen and with a
graphical interface, operators can monitor and control complex
Personal Digital Assistants (PDAs). Other applications include
Computerized gaming, student registration systems,
Financial and scientific applications
MARKET OVERVIEW OF TOUCH SCREENS
The touch screen market's dynamics are altered by growing
shipment of Apple's iPhone and iPod and recently the iPad.
Projected capacitive touch technology is found to be more
adopted in mobile phones and tablets, Display Search forecasts
that projected capacitive will pass resistive touch technology to
become the leading touch technology in 2010, measured by
Advances in technology
Touchscreens can suffer from the problem of
fingerprints on the display. This can be mitigated by the
use of materials with optical coatings designed to
reduce the visible effects of fingerprint
oils, or oleophobic coatings as used in the iPhone 3GS,.
Using a chemical found in paint, called titanium dioxide
.When exposed to sunlight creates a "chain reaction
that creates free radicals, which penetrate the cell walls
of bacteria and fungi and damager their DNA."
Samsung's new transparent and flexible AMOLED
screens, you'll love 3M's new transparent and flexible
3M has developed a new type of touchscreen system
that's flexible, very thin, totally transparent, durable, and
capable of resolving more touch points than you have
fingers (and toes).
a flexible touchscreen bracelet phone could be a reality,
Touch screen bracelet
Flexible & transparent Touch screen
More advanced technology like the one from Japanese Company
Wacom, would bring multitouch capabilities where people
can work on more than on object simultaneously.
Work is still going on to make highly reliable , durable, responsive
, scratch and water proof multitouch touchscreen that can work
with both hands (simultaneously) of the user with great
Touch Screen capability enhance real and natural feeling of
working with pc or other devices for example Drag and drop with
touch is more real rather than with input devices like mouse .
The future of touch surface is touchscreen video projectors.
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