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Blankenbach / Pforzheim Univ. / www.displaylabor.de / Bachelor / Jan. 2013
Electronic Displays: Touch (short version) ET/IT & TI
1
Karlheinz Blankenbach
Pforzheim University, Germany
Prof. Dr. Karlheinz Blankenbach
Pforzheim University
Tiefenbronner Str. 65
D-75175 Pforzheim, Germany
Phone : +49 7231 - 28 - 6658
Fax : +49 7231 - 28 - 6060
Email : [email protected]
Web : www.displaylabor.de
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Electronic Displays: Touch (short version) ET/IT & TI
2 2
• Introduction
• Touch Screen Technologies
Overview
• Application Issues
• Summary
Some slides are from Touch
Screen tutorials given by
3M, Fujitsu, Walker Mobile &
Elo TouchSystems
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Touch Screens
• Easies many HMI concepts by direct input (command buttons etc.)
• Mature technologies available
• Allows easy input incl. characters and graphics e.g. smartphone
• Space saving compared to keyboard and mouse
Why ?
• Rise in some application system costs
• Reduced ambient light performance of display
• Inadequate performance of text input via stylus (is also an additional item !)
• Often more time consuming than keyboard and mouse
Why not ?
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Touch Screens
Why - because it is in !
Touch is not only technology – it is also user interface driven !
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Touch Screen Basics
Finger input:
- simple, no device required
- but low “resolution”
Sylus input:
- simple, high
resolution (> 50 ppi)
- stylus required
- SW for text input
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Touch Screen Applications
• Point of sale (POS) in restaurants, hospitality, post offices, …
• ATMs
• Industrial/process control
• Medical equipment
• Office equipment like copiers
• Retail
• Automotive: navigation, diagnostic systems
• Personal mobile device
• Kiosks: Point of information (POI), merchandising, tourism & museums,
digital photo printing stations, …
• Ticketing & vending incl. transportation
• Gaming, amusement, …
• Telecommunication
• Web phones
• Internet terminals
• Outdoor: Gas pumps, store window applications
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Touch Screen System
…includes
- Touch sensor
- Touch controller
- Software
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Touch Screen System
System becomes more complex
Route the touch screen cable away
from the LCD backlight inverter
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Touch Screen Cost Share
About the same price as for LCD !
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• Introduction
• Touch Screen Technologies
Overview
• Application Issues
• Summary
Analog resistive
Surface capacitive
Surface acoustic wave (SAW)
Infrared (IR)
Projected capacitive Optical
Acoustic pulse recognition
Dispersive signal technology
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Touch Technologies 1/2
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Touch Technologies 2/2
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Analog Resistive (I)
2009
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Analog Resistive (II)
Principle
‚Short„
To TS
controller
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Analog Resistive (III)
Spacer
visible
In-flight entertainment system
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Analog Resistive (IV)
x
y
2
1
R
Rx
4
3
R
Ry
‚Calculation„ of touch impact position
Multi touch ???
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Analog Resistive (V)
• Size range: 2” to ~26”
• Major applications:
- Mobile devices (replaced in smartphones by projected capacitive)
- Point of sale (POS) terminals
• 2006 market share
- 90% by volume
- 75% by revenue
• Selected suppliers:
- Elo TouchSystems, Fujitsu, Gunze, Touch International…
- 50+ suppliers worldwide
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Resistive Touch Screen Controller
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Resistive Touch Screen Board
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Resistive Touch Screen Protocol
Touch electronics use a communications protocol
- Embedded systems e.g. I2C, SPI, UART
- PC-based systems USB, RS232
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Capacitive Overview
(no multi-touch)
Only small changes of capacity
are forced by finger etc.
sophisticated touch controller
and algorithms needed
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Projected Capacitive (I)
Principle: Electrical field changes due to influence of dielectric parameter
Push (like whole touch awareness) by APPLE‟s IPHONE
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Projected Capacitive (II)
Screen
• A specially structured multi-layer
ITO-film is fully laminated to a
glass substrate.
• By the specially structured electrodes
an electric field will be „projected“
through the glass substrate.
• This electric field changes due to the
influence of a touch element (finger).
The dielectric parameter will change
and the controller can calculate the
position of this change.
• The touch finger does not need to
be conductive !
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Projected Capacitive (III)
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Projected Capacitive (IV)
Data acquisition path
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Projected Capacitive (V)
IPHONE Hardware
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Projected Capacitive (VI)
IPHONE integration
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Projected Capacitive (VII)
IPHONE HMI Examples
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Projected Capacitive Touch Integration
Source: Display Search 2012
“one glass”
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P-Cap Touch Signal Processing
- Control sensor electrodes to generate raw data
Noise avoidance via multiple techniques: Frequency Shifting, CDM, etc…
- Process data to convert to image data
- Derive and report data about finger touches (position, width, gestures)
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P-Cap Touch Screen Method
The basic construction of a projected capacitive sensor typically uses two
dielectrically separated layers of glass patterned with ITO that are configured
in rows and columns positioned perpendicularly to create a matrix. Projected
capacitive functionality is achieved by scanning along each axis, identifying
high capacitance lines, then determining a position by the intersection of
those high capacitance lines. This scanning system and the sensor pattern
allow potential decoding of multiple simultaneous touch points known as
„„multi-touch‟‟ capable.
Two capacitance
measurement methods:
- Capacitive Sensing (CSM)
- Charge Time Measure
Units (CTMU).
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P-Cap Touch Screen Board
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P-Cap Touch Screen HW & SW
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Surface Acoustic Wave (SAW)
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Integrated Touch
In-cell light sensors
capture position like
a flat camera
Multi touch !
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• Integration of an array of TFT optical sensors into the LCD‟s backplane
• Like a “camera without a lens”
• Works with finger, stylus, light-pen or laser pointer
• Works as a scanner (e.g., for business cards)
• TMD was in 2003, SHARP announced MP for 2008
Image on 2.6” VGA (300 ppi)
Integrated Touch
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Camera Based
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Radar Touch
• Excellent for large sized screens
• Gesture OK
• Lacks of multi touch by
geometric blocking
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Dual & Multi Touch
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Mobile Infrared Touch
Source: Walker, public and private
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Comparison
Technology Multi-
touch Resolution
Form factor
(bezel) Cost
Resistive
No
100+ dpi,
any object
Up to 5mm on all
sides Low
Surface
Capacitive No
10 dpi , only finger; no pen input
Minimal Medium
Projected
Capacitive Yes
10 dpi - only
works with a
human finger
Minimal High
- All touch screens reduce clarity and enhance reflectivity of the display
- All touch screens rise power consumption:
LCD – Backlight or emissive luminance must be enhanced
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Electronic Displays: Touch (short version) ET/IT & TI
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• Introduction
• Touch Screen Technologies
Overview
• Application Issues
• Summary
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Touch Technology Comparison
Source: M. Jones
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Touch Technology Comparison for Applications
Source: M. Jones
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Touch Screens & Ambient Light
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Touch Screens & System • Total cost of ownership: Consider initial purchase price plus long-term
costs including operation and maintenance
• Accepted input devices
Is it important that the application work with a finger, a gloved finger, a
metal stylus, a nonconductive stylus, a credit card, and/or a long fingernail?
• Durability: How harsh is the intended environment?
Will the system be used in the public sector (vandal considerations)?
• Image quality of the underlying display: Are clarity, brightness and
readability of the display important to the application?
• Sealability and chemical resistance: Is the screen/device likely to be
subjected to spills and/or cleaning with harsh chemicals?
• Reliability: What is the impact of any downtime for repair?
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• Introduction
• Touch Screen Technologies
Overview
• Application Issues
• Summary
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Summary
• Touch screens have many advantages like HMI
• Mature technologies available
• Integration needs some expertise incl. ambient light
• Not every touch technology is suitable for dedicated applications
Touch has many benefits
but need some system considerations
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Summary
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Touch Screen Companies
Name Internet Technology
A D Metro www.admetro.com C, R
Bergquist www.bergquistcompany.com R
Chi Lin Technology/
NextWindow
www.chilintech.com.tw
www.nextwindow.com
R, Opt
DigiTech Systems www.digitechsys.co.kr C, R
EGalax www.egalax.com.tw Cont
Elo TouchSystems www.elotouch.com APR, C, IR,
PC, R, SAW
Fujitsu www.fcai.com R
Gunze www.gunzeusa.com R
Hampshire www.hampshirecompany.com Cont
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Touch Screen Companies
Name Internet Technology
Horizon Technology www.horizontechnology.com SAW
Immersion www.immersion.com TF
IRTouch Systems www.irtouch.com IR
Northpoint Techn. www.northpointech.com C, R
Smart Technologies www.smarttech.com Opt
SMK Electronics www.smkusa.com IR, R, TF
Touch International www.touchinternational.com C, IR, PC, R
Touch KO/ White
Electronic Designs
www.touchko.com
www.wedc.com
PC, R
Wacom www.wacom.com EMR
Zytronic www.zytronic.co.uk PC
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What Touch Screen Technology Is It ? (I)
• If it responds, it‟s either infrared or optical
- Resistive needs pressure
- Surface & projected capacitive need a finger
- Surface acoustic wave needs a sound-absorbing contact
- APR/DST (bending wave) needs a firmer touch
• Block the corners of the screen with something opaque
- If it still responds to a touch away from the corners, it‟s infrared
(IR transceivers are distributed all around the periphery)
- If it stops responding, it‟s optical
(imaging cameras are located in the corners)
Brush the screen very lightly with Kleenex
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What Touch Screen Technology Is It ? (II)
• If it didn‟t respond, poke it with a toothpick
- If it responds, it‟s resistive or APR/DST (bending wave)
- Surface & projected capacitive need a finger
- Surface acoustic wave needs a sound-absorbing contact
- Check to see if the surface moves ever so slightly when you
poke it with the toothpick (watch a reflection of a light source
on the surface of the screen and try several locations)
- If the surface moves, it‟s resistive (the surface is PET)
- If the surface doesn‟t move, it‟s APR/DST (bending wave)
the surface is glass
Brush the screen very lightly with Kleenex
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What Touch Screen Technology Is It ? (III)
If it didn‟t respond, touch it with a pencil eraser
- If it responds, it‟s surface acoustic wave
- Surface acoustic wave needs a sound-absorbing contact
- If it doesn‟t respond, it‟s either surface or projected capacitive
- Surface capacitive and projected-capacitive need a finger
- Check for faintly visible straight or jagged lines in a repeating
pattern in the darkest areas of the screen (the lines are most
visible when the screen is powered off and you‟re looking at
the surface using reflected light)
- If you see lines, it‟s projected capacitive
(you‟re seeing the transparent conductors on the sensor)
- If you don‟t see any lines, it‟s surface capacitive
Brush the screen very lightly with Kleenex