Touchscreens Finall New

7/30/2019 Touchscreens Finall New

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Touch Display-Touch Screen Mechanisms

Involved


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What is a touch screen?

An electronic visualdisplay that locates thecoordinates of a users

touch within display area

Works independently of what is beingdisplayed on screen

[7]


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Brief History

Invented by E.A. Johnson (RoyalRadar Est.) around 1965 for air traffic control

HP-150 home computer usinginfrared technology in 1983

1993 Apples Newton andIBMs Simon

2002 Microsofts Windows XPTablet

2007 Apples iPhone (Multi -touch )[6]


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Multi-Touch Architecture

to sense touch

Touch screensensor

To determinelocation

Touch screencontroller anddriver

Signal toexecute

application

Operatingsystem

Application

Capable of sensing multiplesimultaneous points

Capable of delivering sets of simultaneous points to the OS

Capable of forwarding multiplestreams of moving points (andacting on a defined subset of

them) Capable of decoding multiple

streams of moving points andtaking actions in response


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One Reason Why There Are So Many Technologies

Touch Technology

Resistive Surface capacitive

Surface acoustic wave Projected capacitive,Embedded (capacitive)

Camera-based & Infrared (allforms),

Planar scatter detection Embedded (light-sensing) Vision-based Acoustic Pulse Recognition &

Dispersive Signal Technology

Whats Being Measured

Voltage Current

Ultrasonic wave amplitude Change in capacitance

Absence or reduction in light

Presence of light Change in image Bending waves


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Resistive Touch Screens

Two layers of conductive material Touch creates contact between resistive layers completing circuit

Voltage in circuit changes based on position Controller determines location based on voltages


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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 )


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Capacitive Touch Screens

Glass panel with conductivelayer (Indium Tin Oxide)

electrodes around the panel'sedge distribute low voltageuniformly across the conductivelayer creating a uniform electric

field

[2]


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Projected Capacitive

It is of two types : self and mutual capacitance.

Self capacitance:


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Self-capacitance electrodevariations

Self capacitance Multiple separate slots

in a single layer Each slot is scanned

individually


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Mutual-capacitance principle

No touch

Touch


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Mutual capacitance example (Apple iPhone)


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Surface capacitance

Touch draws minuteamount of current creatingvoltage drop

Coordinates of point of contact calculated bycontroller

[2]


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Surface capacitance

Scratch-resistanttop coat

Hard coat with AGElectrode pattern

Conductive coating(ATO, ITO or TO)

Glass

Optional bottomshield (not shown)


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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 High cost


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Acoustic Wave Touch Screens-Surface Acoustic Wave

Surface consists of glass overlay with transmittingand receiving transducers


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[2]

Projected variation of amplitude of ultrasonic waves with time and distance


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Acoustic Pulse Recognition

Plain glass sensor with 4piezos on the edges

Table look-up of bending

wave samples (acoustic touch signatures)


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Acoustic Pulse Recognition


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Dispersive Signal Technology

Plain glass sensor with 4 piezos in

the corners

Real-time analysisof bending waves

in the glass (time of flight calculation )


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Why AWT?

Advantages: Best optical quality High surface durability and seal Activated by multiple sources

Disadvantages: Expensive Contaminates on screen can cause false-touches


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Uses infrared LEDs and

matching photo detectors

Touching screen interruptsLEDs

Optical or Infrared Touch ScreenTraditional infrared

[2]


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Waveguide Infrared

Principle


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Camera based optical


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Planar Scatter Detection Infrared (IR) light is injected in the

sensor substrate from the edges.

The IR light travels via TotalInternal Reflection within thesubstrate and is disturbed or scattered by any object touchingthe surface of the substrate.

The IR light is injected and

analyzed, scattered light from atouch points is detected at theedge of the sensor substrate andused to calculate the touch.


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Vision based When the user comes into

contact with the surface, the lightrays are frustrated, since they cannow pass through into the contactmaterial and the reflection is no

longer total at that point.

This frustrated light is scattereddownwards towards an infraredwebcam, capable of picking theseblobs up, and relaying them totracking software.


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Infrared/OpticalTouch Screens

Advantages:

High optical clarity Durable surface Supports multi-touch Can scale to large sizes

Disadvantages:

Expensive Cameras can get out of alignment


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Touch Screen Techniques-comparison

Technology MajorAdvantage

Major Flaw

Projected Capacitive Multi-touch Finger-only

Surface Capacitive Touch sensitivity High drift

Analog Resistive Low cost Low durability Surface Acoustic Wave Durability Soft touch object

Acoustic Pulse Recognition Any touch-object No touch & hold

Dispersive SignalTechnology

Any touch-object No touch & hold

Traditional Infrared Reliability High cost

Waveguide Infrared Low cost Contamination

Camera-Based Optical Scalability Profile height

Planar Scatter Detection Flush surface High cost

Vision-Based Multi-touch Rear projection

LCD In-Cell Integration Sensitivity


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Applications

Trade show displaysMuseum / tourism displaysPoint-of-sale terminalsRestaurant systemsEmployee time clocksIndustrial process controlsWorld Wide Web access kiosksHome automation systemsCasino and other gaming systemsComputer access for the physically disabled


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Latest in touch technology

Freescale is announcing a new industrial touch sensing technologythat'll even sense your swipes and prods through a film of water .itcan withstand noise, detect electrical interference and reduce falsetouches.

Chris Harrison, co-founder of a startup called Qeexo.new technologycalled FingerSense that adds a tiny acoustic sensor inside asmartphone to listen for and measure the vibrations of the object thattouches it.

The new LCD technology patent will allow Apple to fuse touchsensors into display circuitry, a change that could have a dramaticeffect on how thin smart phones or tablets can get.

Integration can further include eliminating redundant structuresand/or finding dual purposes
http://www.engadget.com/tag/freescalehttp://www.engadget.com/2012/02/21/pantech-element-review/http://www.engadget.com/2012/02/21/pantech-element-review/http://www.engadget.com/tag/freescale


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THANK YOU

Touchscreens Finall New

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