2. Presented By
T. Anusha
Pin no: 18UE1A0401
Btech 4th year first sem
Electronic communication & eng
ineering
• Trinity college of engineering & tec
hnology
4. INTRODUCTION
A touch screen is a computer display screen
that is sensitive to human touch, allowing a
user to interact with the computer by touchi
ng pictures or words on the screen.
A touch screen is an input device that allows
users to operate a PC by simply touching th
e display screen which has a sensitive glass o
verlay placed on it .
A touch screen accepts direct onscreen inpu
ts.
5. HISTORY
In 1971, the first "touch sensor" was developed
by Doctor Sam Hurst (founder of Elographics)
while he was an instructor at the University of
Kentucky.
The University of Kentucky Research Foundat
ion named it as “Elograph”.
The "Elograph" was not transparent like moder
n touch screens.
In 1974, the first true touch screen incorporatin
g a transparent surface came.
6. FUNCTIONS OF TOUCH S
CREEN
Pressure sensitive activation-by finger or stylu
s.
Emulates mouse functions-click, double click,
& drag.
Touch screen & mouse can be used concurrent
ly.
Durable & scratch resistant coated surface.
Compatible with Windows 95,98,NT,2000,XP,
Macintosh,Linux.
7. HOW DOES A TOUCHSCREEN W
ORKS?
A basic touch screen has three main compo
nents:
touch sensor
controller
software driver
8. 1.TOUCH SENSOR
A touch screen sensor is a clear glass panel wit
h a touch responsive surface which is placed o
ver a display screen.
The sensor generally has an electrical current o
r signal going through it and touching the scree
n causes a voltage or signal change. This volta
ge change is used to determine the location of t
he touch to the screen.
9.
10. 2.CONTROLLER
The controller is a small
PC card that connects b
etween the touch senso
r and the PC.
It takes information fro
m the touch sensor and
translates it into inform
ation that PC can under
stand.
11. 3.SOFTWARE DRIVER
The driver is a software that allows the touch s
creen and computer to work together.
It tells the operating system how to interpret th
e touch event information that is sent from the
controller.
Most touch screen drivers today are mouse-e
mulation type drivers. This makes touching the
screen the same as clicking your mouse at the s
ame location on the screen.
16. Contd.
Pressing the flexible top sheet creates electrical
contact with the coating on the glass.
The touch screen controller gets the alternatin
g voltages between the two layers and converts
them into the digital X and Y coordinates of th
e activated area.
17. Advantages of Resistive Technolo
gy
Can be activated with any device
Low cost solution
Low power consumption
18. Disadvantages of Resistive Techn
ology
Poorer durability compared to other techn
ologies
Very short life, especially considering co
smetic wear
19. CAPACITIVE TOUCH SCREEN TECHN
OLOGY
In the capacitive system, a layer that stores el
ectrical charge is placed on the glass panel.
When a user touches, some of the charge is tran
sferred to the user, so the charge on the capaciti
ve layer decreases.
This decrease is measured in electrodes located
at each corner of the monitor.
The computer then calculates the coordinates, fr
om the relative differences in charge at each cor
ner.
20. Contd.
A finger touch draws
current from each co
rner.
Then the controller
measures the ratio o
f the current flow fro
m the corners and ca
lculates the touch lo
cation
21. Capacitive Technology
ADVANTAGES
More durable than
resistive
Higher transmittan
ce than resistive
DISADVANTAGES
Accepts input from
finger only.
Accuracy is depen
dent on capacitanc
e of person
22. SURFACE WAVE TECHNOLO
GY
It has a transmitting and receiving transducers for bot
h the X and Y axes.
The touchscreen controller sends a five-megahertz ele
ctrical signal to the transmitting transducer, which co
nverts the signal into ultrasonic waves within the glas
s.
These waves are directed across the front surface of t
he touchscreen by an array of reflectors.
23.
24. Contd.
Reflectors on the opposite side gather and dire
ct the waves to the receiving transducer, which
reconverts them into an electrical signal.
When you touch the screen, you absorb a porti
on of the wave travelling across it.
The receivers can detect a drop in amplitude a
nd thus coordinate is calculated.
25. ADVANTAGES
Very high transmittan
ce
Very high durability
DISADVANTAGES
Requires “soft” input
device
Surface obstructions c
an cause a false touc
h
26. INFRARED TOUCH SCREEN TECH
NOLOGY
IR makes use of a “frame” around the perimete
r of the display. On two sides there are closely
spaced IR LEDs and on the opposing two sides
there are matching photo transistors.
The LEDs are turned on in sequence and the si
gnal is read from the matching transistor. If no
signal is read, then that indicates a blocked IR
beam, meaning a touch.
27.
28. ADVANTAGES
Highest quality of unde
rlying image
Very high transmittanc
e
Very high durability and
reliability
DISADVANTAGES
Lower resolution than o
ther technologies
Surface obstructions ca
n cause a false touch
29. DISPERSIVE SIGNAL TECHNOL
OGY
This is the recent most techn
ology, introduced in 2002.
It uses sensors to detect the
mechanical (vibrational)ener
gy in the glass that occur du
e to a touch.
Complex algorithms then int
erpret this information and
provide the actual location o
f the touch.
30. APPLICATIONS
Public Information Displays
tourism displays, trade show displays
Customer Self-Service
stores, restaurants, transportation hubs, ATM and
airline e-ticket terminals.
And many more uses...
computerized gaming, student registration syste
ms, multimedia software, financial and scien
tific applications, and more.
31. CONCLUSION
Touchscreens, touch panels or touchscreen pan
els are display overlays which have the ability
to display and receive information on the same
screen.
Touchscreens also have assisted in recent cha
nges in the PDAs, making these devices more
usable.
