A touchscreen is a display that can
presence and location of a
touch within the display area.
The term generally refers to touch orThe term generally refers to touch or
contact to the displaycontact to the display ofof thethe
device bydevice by
a finger or hand.a finger or hand.
The touchscreen has two main attributes:The touchscreen has two main attributes:
1.1. It enables one to interact with what is displayedIt enables one to interact with what is displayed
directly on the screen, where it is displayed,directly on the screen, where it is displayed,
rather than indirectly with a mouse or touchpad.rather than indirectly with a mouse or touchpad.
2.2. It lets one do so without requiring anyIt lets one do so without requiring any
intermediate device, again, such as a stylus thatintermediate device, again, such as a stylus that
needs to be held in the hand. Such displays canneeds to be held in the hand. Such displays can
be attached to computers or, as terminals, tobe attached to computers or, as terminals, to
Touchscreens emerged from academic and
corporate research labs in the second half of the
One of the first places where they gained some
visibility was in the terminal of a computer-assisted
learning terminal that came out in 1972 as part of the
The HP-150 from 1983 was probably the world's
earliest commercial touchscreen computer.
It doesn't actually have a touchscreen in the strict
sense, but a 9" Sony CRT surrounded by infrared
transmitters and receivers which detect the position
of any non-transparent object on the screen.
• The development of multipoint touchscreenThe development of multipoint touchscreen
facilitated the tracking of more than one finger onfacilitated the tracking of more than one finger on
the screen, thus operations that require more thanthe screen, thus operations that require more than
one finger are possible.one finger are possible.
• These devices also allow multiple users to interactThese devices also allow multiple users to interact
with the touchscreen simultaneously.with the touchscreen simultaneously.
• With the influence of the multi-touch-enabledWith the influence of the multi-touch-enabled
iPhone and the Nintendo DS, the touchscreeniPhone and the Nintendo DS, the touchscreen
market for mobile devices is projected to produce 5market for mobile devices is projected to produce 5
billion in 2009.billion in 2009.
There are several principal ways to build a touchscreen:There are several principal ways to build a touchscreen:
• In the most popular techniques, the capacitive or resistive approach,In the most popular techniques, the capacitive or resistive approach,
manufactures coat the screen with a thin, transparent metallic layer.manufactures coat the screen with a thin, transparent metallic layer.
• When a user touches the surface, the system records the change inWhen a user touches the surface, the system records the change in
the electrical current that flows through the display.the electrical current that flows through the display.
• Dispersive-signal technology which 3M created in 2002, measuresDispersive-signal technology which 3M created in 2002, measures
the piezoelectric effect — the voltage generated when mechanicalthe piezoelectric effect — the voltage generated when mechanical
force is applied to a material — that occurs chemically when aforce is applied to a material — that occurs chemically when a
strengthened glass substrate is touched.strengthened glass substrate is touched.
There are two infrared-based approachesThere are two infrared-based approaches..
• An array of sensors detects a finger touching orAn array of sensors detects a finger touching or
almost touching the display, thereby interruptingalmost touching the display, thereby interrupting
light beams projected over the screen.light beams projected over the screen.
• Bottom-mounted infrared cameras record screenBottom-mounted infrared cameras record screen
• In each case, the system determines theIn each case, the system determines the
intended command based on the controlsintended command based on the controls
showing on the screen at the time and theshowing on the screen at the time and the
location of the touch.location of the touch.
The types of technologies that can be found are as
● The resistive touch screen
uses a glass panel with a
ITO(Indium Tin Oxide)
coating on the side surface.
● A PET film is a tightly
suspended over the ITO
coating surface of a glass
Working Principle:Working Principle:
• The microprocessor applies +5V to pin (X left) on the glass panel,
and the voltage is uniformly decreasing to pin (X right) for 0V
because of the resistive ITO coating on the glass substrate, and the
PET film is grounded.
● When the screen is touched, it pushes the conductive ITO coatingWhen the screen is touched, it pushes the conductive ITO coating
on the PET film. That results the electrical contact, producing theon the PET film. That results the electrical contact, producing the
voltages. It presents the position touched.voltages. It presents the position touched.
• When the touchscreen is touched, a voltage on the glass substrate
proportional to the X position of the touch appears on the PET film.
•This voltage is digitized by the A/D Converter and subjected to an
averaging algorithm. Then it is stored and transferred to the host.
Hence, the X position is produced. The next electric cycle, Y position is
•Resistive touchscreen deliver cost-effective, consistent and durable
•Resistive technology include only 75% optical transparency and the
fact that a sharp object can damage the resistive layers.
Surface Acoustic Wave:
• On the pure glass substrate, there
are four piezoelectric transmitting
and receiving transducers on the
three corners for both the X and Y
• The SAW controller sends a 5
MHz electrical signal to the X-axis
and Y-axis transmitting transducers..
• When the touchscreen is touched, the finger absorbs a portion of the
wave passing across the surface of the panel.
• SAW can be used in any and all applications for the best possible
image clarity an unlimited life.
• Capacitive touchscreen is a four multi-layer glass.
• Small amount of voltage is applied to the electrodes on the four
• A human body is an electric conductor, so when touched the screen
with a finger, a slight amount of current is drawn, creating a voltage
drop. The current respectively drifts to the electrodes on the four
• The capacitive system has very long life (about 225 million clicks).
• IR eliminates the use of glass or plastic overlay that most other touch
technologies require in front of the display.
• High cost of the technology.
• IR increases the noise floor at the optical sensor
● Conventional optical-touch systems
use an array of infrared (IR) light-
emitting diodes (LEDs) on two
adjacent bezel edges of a display,
with photosensors placed on the two
opposite bezel edges to analyze the
system and determine a touch event.
Comparison of Technologies::
Technology Resistive SAW Infrared Capacitive
Durability: 5 years 5 years 3 years 2 years
Stability: High Higher High Ok
Transparency: Ok Good Good Ok
Touch: Anything Finger/ pen Sharp Conductive
Response time: <10ms 10ms <20ms <15ms
Advantages & Disadvantages:
• User friendly.
• Fast response.
• Error free input.
• Easy to install.
• Use finger, fingernail, gloved hand, stylus or any soft-tip
pointer to operate.
• Easy to clean and maintain.
• Compatible with Windows, Macintosh and Linux.
• Does not interfere mouse and keyboard function.
• Make computing easy, powerful and fun.
Stress on human fingers when used for more than a few minutes
at a time. (for example, ATMs).
Touchscreens can suffer from the problem of fingerprints on the display
• Library resource guidesLibrary resource guides
• Corporate informationCorporate information
• Public Transportation Schedule / StatusPublic Transportation Schedule / Status
• Airport terminal passenger internet andAirport terminal passenger internet and
email systemsemail systems
• Automated travel and entertainment ticketAutomated travel and entertainment ticket
• Shopping mall directoryShopping mall directory
• Gas stationsGas stations
• Point of salesPoint of sales
• Grocery storesGrocery stores
• Hospital and hotel directories (check-in,Hospital and hotel directories (check-in,
• Banks and Financial ReportingBanks and Financial Reporting
• Bank cash advance and teller machinesBank cash advance and teller machines
• Interactive computer gamesInteractive computer games
● Military control systemMilitary control system
● Scientific research labScientific research lab
Future Touchscreens Technology:Future Touchscreens Technology:
RPO’ s Digital Waveguide Touch:RPO’ s Digital Waveguide Touch:
• Minimal power requirements.Minimal power requirements.
• High inherent accuracy & precession.High inherent accuracy & precession.
• Zero-pressure touch & allows finger scrolling.Zero-pressure touch & allows finger scrolling.
• Allows100% display light output, picture definition and colourAllows100% display light output, picture definition and colour
• Low-cost & Excellent durability.Low-cost & Excellent durability.
3-dimensional Touchscreens3-dimensional Touchscreens
• Designers are trying to use touchscreen to simplify input
commands for largely unsophisticated computer users.
• Today, a larger share of population is PC literate, yet the
touchscreen has become adopted by computer users of all
abilities because it is simple, fast, and innovative.
• In future there is no usage of mouse and keyboards as they
will be replaced by touchscreens.
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