Touch screens work by detecting the coordinates of a user's touch and can be used without an intermediate device like a mouse or keyboard. A digitizer converts analog signals from touches into digital signals for the device to understand. The four main technologies are resistive, capacitive, surface acoustic wave, and infrared. Resistive screens use layers that complete a circuit on touch while capacitive screens detect voltage changes from a touch. Surface acoustic wave screens use ultrasonic waves redirected by a touch. Infrared screens use LEDs and cameras to detect touches. Each technology has advantages and limitations in accuracy, durability, optical quality, and cost. Touch screens have become widely used due to their user-friendly interface.

1. Touch Screen Technology and
Digitizer
By: Devashree Kumari
BCA III
Roll no.: 20
Guide:
Mr. Ramesh Rawat

2. What is a touch screen?
• An electronic visual
display that locates the
coordinates of a users
touch within display
area.
• Works independently of
what is being
displayed on screen.[7]

3. When is it Applicable?
• It allows users to interact directly
with what is being displayed,
rather than indirectly using a
mouse or keyboard.
• Can be used without any
intermediate device.
• Found in modern smartphones,
video games, kiosks, navigation
systems, etc. . .
[1]

4. What Is a Digitizer?
The digitizer by definition is a device used to convert analog
signals into digital signals. In the case of our cell phones, this
device would be the glass that covers the LCD. It converts
your actions (press, swipe, etc) into a digital signal that your
phone understands. The data from the digitizer (glass) is
transferred to the phone by the attached digitizer flex cable
or digitizer flex ribbon.

5. Brief History
• Invented by E.A. Johnson (Royal
Radar Est.) around 1965 for air
traffic control.
• HP-150 home computer using
infrared technology in 1983.
• 1993 Apple’s Newton and
IBM’s Simon.
• 2002 Microsoft’s Windows XP Tablet.
• 2007 Apple’s iPhone (Multi-touch).
[6]

6. SIMON by IBM
• In 1992 IBM released the first smart phone
called Simon, with a touch screen interface
that allowed users to dial phone numbers. In
addition Simon was also able to send and
receive faxes, e-mails and cellular pages. Simon
featured many applications including an
address book, calendar, appointment
scheduler, calculator, world time clock,
electronic note pad, handwritten annotations
and standard and predictive stylus input
screen keyboards.

7. Touch Screen Technology
• Four different technologies used to make touch screens
today:
• Resistive
• Capacitive
• Surface Acoustic Wave (SAW)
• Infrared LED or Optical

8. Resistive Touch Screens
• Two layers of conductive
material.
• Touch creates contact
between resistive layers
completing circuit.
[2]

9. Resistive Touch Screens
• Voltage in circuit changes
based on position.
• Controller determines
location based on voltages.
• Any material can trigger
sensors.
[2]

10. Why Resistive?
• Advantages:
• Cost-effective and low power Requirements.
• Activated by any object.
• Accurate.
• Disadvantages:
• Polyester surface can be damaged.
• Only 75% light transmission.
• Lower endurance (~35 million touches).

11. Capacitive Touch Screens
• Glass panel with conductive
layer (Indium Tin Oxide).
• Small amount of voltage
applied to four corners of
touch screen.
[2]

12. Capacitive Touch Screens
• Touch draws minute
amount of current creating
voltage drop.
• Coordinates of point of
contact calculated by
controller.
[2]

13. Why Capacitive?
• Advantages:
• Durable surface material.
• High endurance (~255 million touches).
• Very accurate.
• Good optical quality.
• Disadvantages:
• Triggered only by bare finger or active stylus.

14. Surface Acoustic Wave Touch
Screens
• Surface consists of glass overlay with transmitting
and receiving transducers.

15. Surface Acoustic Wave Touch
Screens
• Electrical signals sent to the transmitting transducers
converts to ultrasonic waves .
• Waves are directed across screen by reflectors then
directed to receiving transducers.
[2]

16. Surface Acoustic Wave Touch
Screens
• When finger touches screen it absorbs waves.
• Received values are compared to stored digital
maps to calculate x and y coordinates.
[2]

17. Why SAW?
• Advantages:
• Best optical quality.
• High surface durability and seal.
• Activated by multiple sources .
• Disadvantages:
• Expensive.
• Contaminates on screen can cause false-touches.

18. • Uses infrared LEDs and matching photodetectors.
• Touching screen interrupts LEDs.
Infrared/Optical
Touch Screens
[2]

19. Infrared/Optical
Touch Screens
• Cameras detect reflected LED caused by touch.
• Controller able to calculate coordinates from
camera data.
[8]

20. Infrared/Optical
Touch Screens
• Advantages:
• High optical clarity.
• Durable surface.
• Supports multi-touch.
• Can scale to large sizes.
• Disadvantages:
• Expensive.
• Cameras can get out of alignment.

21. Touch Screen Technology Comparison Chart
Resistive Infrared SAW Capacitive
Touch
Resolution
High High Average High
Clarity Average Good Good Good
Operation Finger or Stylus Finger or Stylus Finger or Soft-
tipped Stylus
Finger only
Durability Can be
Damaged by
Sharp Objects
Highly Durable Susceptible to
Dirt and
Moisture
Highly durable

22. End..
• Though the touch screen technology contains some
limitations it’s very user friendly, fast, accurate, easy for
the novices & fun to operate. It has been widely accepted.
And now by just modifying a little it can replace the
mouse and key board completely in near future.

23. Bibliography
• www.wikipedia.org
• www.makeuseof.com
• www.techexplainer.wordpress.com
• www.inventors.about.com
• Google Images