You must have seen touch screens at
ATMs, cellphones, information kiosks
.Touch screen based system allows an
easy navigation around a GUI based
1971, the first "touch sensor" was
developed by Doctor Sam Hurst (founder
sensor called the "Elograph" was
patented by The University of Kentucky
1974, the first true touch screen
incorporating a transparent surface came on
the scene developed by Sam Hurst and
US3662105: Electrical Sensor Of Plane
Hurst; George S. , Lexington, KY
Parks; James E. , Lexington, KY
US3798370: Electrographic Sensor For
Determining Planar Coordinates
Hurst; George S. , Oak Ridge, TN
There are four popular touch
screen technologies but all of them have
three main components.
Touch sensitive surface
The software driver
touch sensitive surface is an extremely
durable and flexible glass or polymer touch
response surface, and this panel is placed
over the viewable area of the screen. In most
sensors there is an electric signal going
across the screen, and a touch on the surface
causes change in the signal depending on the
touch sensor technology used .This change
allows the controller to identify the location of
controller is a device that acts as the
intermediate between the screen and the
computer .It interprets the electrical signal
of the touch event to digital signal that
computer can understand. The controller
can be placed with the screen or housed
software driver is an interpreter that
converts what signal comes from the
controller to information that the operating
system can understand
Are composed of two flexible sheets
coated with a resistive material and
separated by an air gap or microdots.
When contact is made to the surface of
the touchscreen, the two sheets are
pressed together, registering the precise
location of the touch.
1. works well with almost any stylus-like
2. more desirable than a capacitive touch
screen, which has to be operated with a
capacitive pointer, such as a bare finger.
3. Low cost
4. technology can be made to support
the user cannot press a large hand down
on the screen while writing due to the
nature of passive touch screen.
the tradeoff is required between having a
dedicated implement (stylus) versus the
ability to use one's fingers as a stylus.
A capacitive touchscreen panel consists of
an insulator such as glass, coated with a
transparent conductor such as indium tin
Touching the surface of the screen results
in a distortion of the body's electrostatic
field, measurable as a change in
1. Since capacitive screens only respond to
materials which are conductive (human
finger used most commonly), they can
be cleaned with cloths without accidental
Are more responsive than resistive touch
A standard stylus cannot be used for
capacitive sensing unless it is tipped with
some form of conductive material, such as
anti-static conductive foam.
More expensive to manufacture and offer a
lesser degree of accuracy than resistive
Capacitive touch screens cannot be used
with gloves, and can fail to sense correctly
with even a small amount of water.
An Infrared touch screen uses an array of X-Y
infrared LED and photodetector pairs around
the edges of the screen to detect a disruption
in the pattern of LED beams.
major benefit: can detect any input including a
finger, gloved finger, stylus or pen.
they do not require any patterning on the glass
which increases durability and optical clarity of
the overall system.
In a strain gauge configuration, also called
force panel technology, the screen is
spring-mounted on the four corners and
strain gauges are used to determine
deflection when the screen is touched.
This is a relatively modern development in
touchscreen technology, in which two or more
image sensors are placed around the edges
(mostly the corners) of the screen. Infrared
back lights are placed in the camera's field of
view on the other side of the screen. A touch
shows up as a shadow and each pair of
cameras can then be triangulated to locate
the touch or even measure the size of the
touching object .
in 2002 by 3M, this system
uses sensors to detect the mechanical
energy in the glass that occurs due to a
touch. Complex algorithms then interpret
this information and provide the actual
location of the touch.
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
piezoelectric transducers located at
various positions around the screen to turn
the mechanical energy of a touch
(vibration) into an electronic signal.
screen hardware then uses an
algorithm to determine the location of the
touch based on the transducer signals.
touch screen itself is made of ordinary
glass, giving it good durability and optical
clarity. It is usually able to function with
scratches and dust on the screen with