Touch Screen Technology lecture slides for Undergraduate level


Contents
 1. Walkthrough
 2. Introduction
 3. Applications
 4. History, Evolution & Development
 5. Types of Touchscreen Technology
 i. Resistive
 ii. Capacitive
 iii. SAW iv. Infrared / Optical
6. Future Technology


Walk Through
 Call it an effort of human mind or a miracle from human heart
but this is all happening with technology.
 Just move the hand or walk your fingers over a thing and it
works.
 Yes, it is the interactive gesture based technology I am talking
about. Walkthrough


Introduction
 A touch screen is an electronic visual display that detect the
location and presence of touch in the display area
 This works by locating the coordinates of users touch
independent of what is being displayed on the screen


 In today’s world, Touch Screen Technology is omnipresent
 Starting from mobiles to home appliances almost all the
electronic devices comprise TST.
 It allows users to interact directly with what is being displayed,
rather than indirectly using an intermediate device like mouse or
keyboard
 Widely used in modern smartphones, video games, kiosks,
navigation systems, etc. Applications


History, Evolution & Development
 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)


 There are four main types of touchscreen technology namely: 1.
Resistive
 2. Capacitive
 3. Surface Acoustic Wave (SAW)
 4. Infrared LED or Optical Looking from an engineer’s
perspective, this revolutionary touchscreen technology is a 2
dimensional sensing device made of 2 sheets of material
separated by spacers Types of Touchscreen Technology


Resistive Touchscreen Technology
 A resistive touch screen panel is composed of several layers
 The most important of which are two thin, metallic, electrically
conductive layers separated by a narrow gap
 When an object, such as a finger, presses down on a point on the
panel's outer surface the two metallic layers become connected at
that point.
 This causes a change in the electrical current, which is registered
as a touch event and sent to the controller for processing. It is used
in Grocery Stores, Hotels, Restaurants and Retail Stores.


Advantages & Disadvantages
 Advantages
 1. Cost-effective solution
 2. Activated by any stylus
 3. Very accurate
 4. Low power requirements
 5. Liquids won't affect touch screen performance
 Disadvantages
 1. Polyester surface can be damaged
 2. Lower endurance (35 million touches)


 8” resistive touch screen will cost about $60
 4 and 5 wire touch screens don’t need controllers
 For those that do, they cost less than $5
 Any object can be used to activate the screen
 Not able to register multiple touches
 ~75% of light is transferred through (12.5% per layer)
 Some of the popular devices that use Resistive Touchscreen are
Nintendo DS, Nokia N97, HTC Touch Pro2, HTC Tattoo, Sony
Ericsson Satio, etc. Summary


Capacitive Touchscreen Technology
 A capacitive touch screen panel consists of an insulator such as
glass, coated with a transparent conductor such as indium tin
oxide (ITO)
 Small amount of voltage applied to four corners of touch screen,
draws minute amount of current creating voltage drop
 Coordinates of point of contact calculated by controller
 The capacitive systems transmit almost 90% of light from the
monitor


 Advantages
 1. Scratch resistant, durable surface
 2. High endurance (225 million touches)
 3. Very accurate
 4. Good optical clarity
 5. Liquids won't affect touch screen performance
 Disadvantages
 1. Does not work with gloved fingers or stylus


Summary
 8” capacitive touch screen costs about $100
 Controllers can be bought for less than $5
 Only conductive objects can be used to activate
 Able to register multiple touches
 ~88% of light is transferred through
 Some of the devices using capacitive touchscreen are Motorola
Xoom, Samsung Galaxy Tab, Samsung Galaxy SII, Apple’s iPad


Surface Acoustic Wave
 Touchscreen Technology
 The Surface Acoustic Wave Touchscreen technology contains two
transducers (transmitting and receiving) placed along the X-axis
and Y- axis of the monitor’s glass plate along with some reflectors.
 When the screen is touched, the waves are absorbed and a touch is
detected at that point. These reflectors reflect all electrical signals
sent from one transducer to another.
 This technology provides excellent throughput and image clarity.
 The waves propagate across the glass and are reflected back to the
sensors.


 Advantages
 1. Durable glass construction
 2. High optical clarity
 3. Activated by a finger, gloved hand, or soft tip stylus
 Disadvantages
 1. Moving liquids or condensation can cause false touches
 2. Solid contaminants create non-touch areas until removed
 3. Doesn't support drag or draw effectively
 4. Expensive


Summary
Prices for individual screens are unavailable
Any object can be used to activate the screen
Able to register multiple touches
~100% of light is transferred through
SAW touch screen technology is suggested for use in ATMs,
Amusement Parks, Gaming Environments, Industrial Control
Rooms etc


Infrared Touchscreen Technology
 An infrared touch screen uses an array of X-Y infrared LED and
photo detector pairs around the edges of the screen to detect a
disruption in the pattern of LED beams.
 Touching screen interrupts LEDs
 Cameras detect reflected LED caused by touch
 Controller able to calculate coordinates from camera data


 Advantages
 1. Highest quality of underlying image
 2. Very high transmittance
 3. Excellent anti-glare, with use of chemically etched glass
 4. Can be activated with almost any device
 5. Higher accuracy than other technologies
 6. Very high durability and reliability
 Disadvantages
 1. Surface obstructions can cause a false touch
 2. It is very sensitive and can be activated by stray touches.
 3. Low resolution
 4. Parallax problems


Summary
 Infra-red bezels have proven to be a very reliable technology for
use in ATMs, Medical Instrumentation and Transportation
Tracking applications
 8” infrared touch screen costs about $160
 Any object can be used to activate the screen
 Able to register multiple touches
 ~100% of light is transferred through


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


Future of Touchscreen Technology
 Touchscreen Technology has made a tremendous progress in
the past few years and the future beholds a lot of surprising
innovations
 As complex the technology gets as simpler the life becomes and
there we would be


Closing Thoughts
 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.

Touch Screen Technology lecture slides for Undergraduate level

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Touch Screen Technology lecture slides for Undergraduate level