Touch panels principle of operation

PERIPHERAL DEVICES 

Bogdan Bartosiński 

Department of Metrology and Optoelectronics

URZĄDZENIA PERYFERYJNE 

SYSTEMÓW 

ELEKTRONICZNYCH 

3. Input devices 

Bogdan 

Bartosiński 

Department of Metrology and Optoelectronics

Track-ball 

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User interface devices 

works on the principle of opto-mechanical mouse 

the ball is much larger in diameter and is mounted on 

the upper part of the device


Logitech M570 track-ball 

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trackball stays in one place 

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perfect for tight workspaces 

you don’t have to move your arm to move cursor 

adjustable speed 

scroll wheel 

Back/Forward buttons 

advanced 2.4 GHz wireless 

1 AA battery, 18-month battery life


Logitech M570 track-ball


3D Spheric Mouse - Axotic


3D Spheric Mouse - Axotic

3D Spheric Mouse 

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freedom to rotate and move your virtual objects in 6 axis 

with only one hand 

the mouse lets you to use your fingers to rotate and your 

hand to move 

rotation 

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1000 dpi optical precision for rotations in 3 axis 

selectable stepping from 1° up to 90° 

rotation can be slowed down to 1/4 or accelerated 4x 

navigation 

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2170 dpi optical precision 

• adjustable acceleration

3D Spheric Mouse 


Area of application 

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3D modelers 

control in virtual reliality 

medical personnel wanting to better interact with and 

operate scanning equipment

Light pen 

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Light pen is a computer pointing light-sensitive 

device shaped like a pen and connected with a 

computer's CRT display 

Light pen is used to draw pictures directly onto the 

screen or select menu options 

Light pen does not shine light onto the screen, the 

screen beams into the pen 

Light pen detects change in brightness of nearby 

screen pixels when scanned by CRT electron beam 

and communicates the timing of this event to the 

computer.

Light pen 


Lens 

Amplifier 

Control Button 

Photoelectric cel

Light pen 

User interface devices

Light pen 

User interface devices


PANELS AND TOUCH SCREENS


PANELS AND TOUCH SCREENS 

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built with flat surface (the operational 

recognizing the pointer position 

field) and system of 

as a pointer can act special stylus or user finger 

device may be in the form of an independent panel or 

transparent screen built into the screen or monitor 

touchpad 

/ touchscreen



Touch screens around us 

small size 

large size 

Smartphone Camcorder Handheld Game Console 

Automotive navigation In flight Entertainment Tablet PC 

Office Automation Medical equipment Fitness machine 

Network Terminal Kiosk ATM Ticketing Maschine 

Factory Automation POS Arcady Game 

Large size Monitor Interactive White Board Digital Signage




In-flight Entertainment - Panasonic eFX system 

installed on a Delta Air Lines Boeing 737




Kiosk




Fitness machine with touch screen




ATM (Automated teller machine)




POS (Point of sale)




Arcade game




Digital Signage



Advantages 

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switch and buttons are not physically required, various input 

interfaces can be make by software 

with multi-touch function, various operations/inputs (eg: zoomin/zoom-out, 

rotation) are possible 

because a user operates an electronic device by directly 

touching the images on the display he is seeing, the operation 

will be intuitive, thus anyone can operate it from first use 

the whole unit is space-saving because display and input 

space are integrated 

unlike keyboard or physical switch, there will be no dirt, dust, 

and moisture getting into the spaces between buttons easy for 

maintenance



Drawbacks 

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since a display is directly touched, the display may get dirty, 

then become less-visible, a direct touch may also cause 

scratches on the screen that may cause malfunction in some 

cases 

unlike push-button and mouse, users will not feel "click" when 

a user input a touch screen, however, there are certain touch 

screens that provide "click feeling" when touched


Classification of touch panels 

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according to methods for determining the position 

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resistive 

capacitive 

technology 

technology 

surface acoustic wave technology 

infrared waves technology 

optical imaging technology 

acoustic pulse recognition technology 

according to placing 

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stand-alone touch panels 

• touch panels on displays and screens

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Touch panels principle of operation 

Resistive technology 

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two layers not contacted and 

separated by thin space 

• fixed bottom layer 

• flexible top layer 

when a fingertip presses down 

on the top layer the two layers 

touch to become connected at 

that point 

resistive layer - ITO (indium tin 

oxide), 90% In2O3 +10% SnO2



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4/8 and 5/6/7 wire version 

Advantages 

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great resolution 

the possibility of using stylus, finger 

light, water, dirt and dust does not affect proper operation 

Disadvantages 

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transparency 75 % 

sharp objects can damage the panel 

requires pressure



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digital matrix resistive technology 

Advantages 

• never needs calibration 

• multitouch, supports up to 10 simultaneous activations 

• simplicity of interface 

• no EMI shielding required 

Disadvantages 

• old type of the resistive technology 

• limited resolution 

• cannot support writing/drawing input



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digital matrix resistive technology



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digital matrix resistive tchnology



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Resistive technology – 4 wire 

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resolution 1024 x 1024 points 

durability 100 000 - 

Rysunki – EloTouchsystems / Electronic Design 

3 000 000 touches



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Resistive technology – 4 wire



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X+ X- Y+ Y- 

Standby Gnd Hi-Z Hi-Z Pull up/Int 

X-Coordinate Gnd Vcc Hi-Z Hi-Z/ADC 

Y-Coordinate Hi-Z Hi-Z/ADC Gnd Vcc



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Rysunki –Electronic Design



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resolution 4096 x 4096 points 

durability 35 000 000 

touches 

bottom layer resistive 

(measurement in both axes) 

top layer only conductive

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ADC 

Vcc 

Gnd 

Gnd 

Gnd 

Gnd 

Vcc 

Vcc 

Vcc 

UL UR LL LR Sense 

Standby Gnd Hi-Z Hi-Z Hi-Z Pull up/Int 

X-Coordinate Gnd Vcc Gnd Vcc HI-Z / ADC 

Y-Coordinate Gnd Gnd Vcc Vcc HI-Z / ADC

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the 5 wire resistive touch screen provides outstanding 

endurance and reliability compared to 4-wire resistive touch 

screens 

touch endurance of 5 wire touch screen is guaranteed for 35 

million touches, 

5 wire film does not use coordinates on the film side and 

hence forms and maintains stable coordinates 

calibration is required only while setting up the system and 

thus a very effective maintenance-free environment is 

provided

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resolution (of Controller): 4096*4096 

material: film 

on glass 

light transmission: 75-85% 

touch activation force: touch force 45g to 110g 

deviation of error:

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comparison resistive technology 

– 4 wire vs 5 wire

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Projected Capacitive technology 

Advantages: 

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light transmission 90% 

high resolution abilities 

supports multiple touches 

long life, no moving parts 

Disadvantages 

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susceptible to electrical noise 

need dedicated controller 

high processing cost



• Projected Capacitive technology 

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capacitance is continually sensed 

by receivers on the screen 

when a finger touches the surface 

of the display, there is a change in 

the level of capacitance 

for every intersection of the X/Y 

(sense/drive) lines the capacity 

change is measured (mutual 

capacitance), interpreted and 

converted to XY coordinates that 

correspond to the actual touch 

position



•Projected Capacitive technology 

electrodes



•Projected Capacitive technology



•Projected Capacitive technology - 3M Multi-touch Display 

M2256PW (22") 

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20 finger input for hand 

accommodation and multi- 

users 

Fast 6 millisecond touch 

response for 20 simultaneous 

finger input 

Compatible with Windows 7 

Supports standard gestures 

Works with nitrile, latex and 

vinyl gloves 

1680x1050 resolution

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projected capacitive has high durability and long life because 

it has no moving parts in operation 

is superior in environment resistance, thus strong at raining, 

wind, and temperature change – is used for digital signage 

and at outdoors terminals 

touch coordinates are drift free 

high resolution abilities 

multi-touch capable - 

up to 20 fingers 

works with finger, gloves and any pointing device 

flexible sensors can be contoured to curved surfaces

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sensitivity of the sensor can be adjusted 

projected capacitive responds to light touch, no pressure 

force is needed for detection 

projected capacitive requires an advanced technology to 

measure electrostatic capacitance, a projected capacitive 

touch screen and controller need to be designed together 

projected capacitive is susceptible to electrical noise 

(LCD) 

the notable application of projected capacitive is smartphone 

(Apple iPhone), portable PC, mobile game, audio player

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Surface Capacitive technology 

Advantages 

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capacitive does not get affected 

by light, moist, dust, or grease 

light transmission up to 85% 

over 160 million touches without 

noticeable degradation 

Disadvantages 

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surface capacitive can detect 

touches by fingers only 

basically it does not detect input 

by gloved hand.



• Surface Capacitive technology 

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voltage is applied to all corners 

of touch screen 

when you touch the screen with 

a finger, a current is drawn 

the amount of current that drifts 

through the electrodes should be 

proportional to the distance from 

the touch point to the four 

corners 

the controller calculates the 

proportion of the current passed 

through the four electrodes and 

figures out the X/Y coordinate of 

a touch point



• Surface Capacitive technology




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is suitable for large size monitors 

does not support multi-touch 

is likely to be affected by noise 

sensor can respond to light touch, and no pressure force is needed 

visibility is high because structure is only one glass layer 

application surface capacitive touch screens 

• tend to be employed for applications used by general public, 

and requiring high-quality looking and high durability 

• are used on ATM, ticketing machine, kiosk, POS, office and 

factory automation, arcade games, medical and food industry 

• medical uses - medical instrument, research equipment and 

patient monitoring system 

• transportation - inner vehicle control panel 

• amusement fields such as casino gaming




elo 2239L 22-inch 

Open-Frame Touchmonitor 

elo 1915L 19-inch 

Desktop Touchmonitor



Surface acoustic wave technology (SAW)



Surface acoustic wave technology (SAW)



Surface Surface acoustic wave technology (SAW)



Surface Surface acoustic wave technology (SAW) 

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one glass sheet with transmitting transducers, receiving 

transducers, and reflectors 

transmitting transducers generate ultrasonic waves 

the ultrasonic waves are reflected by the reflectors and received 

by the receiving transducers 

there are routes on which the SAWs travel from the transmitting to 

the receiving transducers and each route has its own distance 

if one of the routes is touched by a finger, the pulse will be 

absorbed, and the SAW on the route will not be received by the 

receiving transducers 

the sensor will recognize which route was touched, and locate the 

touched point



Surface Surface acoustic wave technology (SAW) 

Specification 

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input method: finger or gloved hand (cloth, leather, or rubber) 

activation 

position accuracy standard deviation of error: less than 0.080" 

(2mm) 

available sizes: 5.0" to 46" 

light transmission: 92% or higher 

resolution: 4096 x 4096 

durability: 50 000 000 touches in one location without failure 

touch point drift: does not drift, one-time calibration is enough



Surface Surface acoustic wave technology (SAW) - features 

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SAW touch screen consists of one glass layer so visibility is 

excellent 

screen has long life, and its glass surface is strong against 

scratch, even though the panel surface gets scratched, its 

sensing function will not be affected 

it is easy to build a large size touch screen in SAW technology 

SAW touch screen does not get affected by external electric 

noise



Surface Surface acoustic wave technology (SAW) - features 

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resolution is relatively high 

detecting function of SAW technology can be affected by 

water droplet, oil and so on, malfunction can be caused by 

those factors 

SAW touch screen does not detect a touch by hard 

materials which do not absorb pulse 

SAW is usually employed for large size applications such as 

kiosk, arcade game, automated cash dispenser, medical 

equipment, office automation, factory automation, financial 

field, and so one



Infrared Touch Technology 

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LEDs and phototransistors 

located vis-a-vis in pairs 

making X Y matrix 

when the infrared LEDs are 

turned on, the 

phototransistors located 

opposite to the LEDs will be 

turned on 

if an infrared light is blocked 

by a finger, then the opposite 

phototransistor will be off



Infrared Touch Technology



Infrared Touch Technology



Infrared Touch Technology –specification 

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input method - finger or gloved hand activation 

touch activation force - no minimum touch activation is 

required with IR touch technology 

typical accuracy 0.047” (21 points / inch) 

minimum accuracy 0.22” (5 points / inch) (for 15" diagonal) 

minimum stylus size 0.25”



Features of Infrared technologies 

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Light transmission is 100% because no film or glass needs to cover 

the surface 

Infrared touch screen can be operated with wet fingers or dirty 

gloves. Thus, it is employed for applications that require high 

reliability such as plant control system, factory automation and ATM. 

No physical nor electrical contacts are required for sensing method. 

Thus, the sensor is stress free and is highly durable. 

Compared with other technologies, infrared technology is stronger 

against electrostatic and magnetic noises. 

Infrared technology can support multi-touch. 

Infrared technology is suitable for large size panel. 

Because an infrared technology uses lights for sensing, the detecting 

function can be affected by strong light such as direct sunlight.



Features of Infrared technologies 

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The resolution of basic infrared technology is not as good as other 

technologies. Thus, it is not suitable for applications that require 

precise inputs. 

It is generally considered that infrared technology is difficult to be 

applied to small size panel. 

Infrared technology usually requires a certain space for installation. 

Thus, the device tends to be large. 

Infrared technology detects anything that blocks lights. Thus, it may 

wrongly detect insects or dusts. 

The advantages of infrared technology are environment resistance, 

no limitation on input materials, and easiness of maintenance. Due to 

these merits, infrared touch screens are used on ATM, factory 

automation, plant control system, ticketing machines, medical 

equipment, Kiosk, POS, interactive whiteboard.



Optical Imaging technology












Optical Imaging technology 

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the infrared lights are emitted from the infrared imaging 

sensors (CCD camera)) 

these lights are reflected by the retro-reflective tapes on 

the sides and come back to the infrared imaging sensors 

from the same angles as emitted 

if the touch screen is touched, the infrared light will be 

blocked and not come back to the infrared imaging 

sensors (a shadow will appear on the blocked point) 

the angles between the two infrared imaging sensors and 

the touching object will be measured using DSP




Advantages 

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technique scales to very large displays 

functions with scratches and surface wear 

(120 inches) 

touch activated by bare finger, gloved finger, or stylus 

transmission is typically > 90% 

Disadvantages 

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moving liquids or solid contaminants may cause false touches 

requires a bezel design to house the edge positioned camera 

system 

touch occurs slightly above the actual surface 

• limited to 2 resolvable points with 2 cameras




Benefits 

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delivers a true multi-touch (recognizing up to 5 independent 

touch points with Windows 8 operating system) 

no pressure needed to activate touch response 

stable, no-drift performance - 

no calibration required 

recognizes touch from virtually any object



Optical Imaging technology - features 

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any input device, such as a paintbrush, finger, pen, or stylus will 

work 

surface coating overlays are not used on the touch screen surface 

optical imaging scales to very large displays, making it possible to 

create interactive conference and teaching settings




Applications 

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interactive digital signage 

retail and shopping malls 

way-finding 

hotels and casinos 

healthcare and medical institutions 

corporate environments 

kiosks and self-service system




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Touch functionality 

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Single touch 

Dual touch 

Multi-touch 

Product types 

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Overlay frame 

Display solution



Optical Imaging technology - NextWindow 

Sizes 17” to 30” 

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Desktop 2S 

Dual touch 

2 CMOS sensors 

Windows 7 certified 

Desktop 6S 

5 point multi-touch 


Windows 8 certified



Optical Imaging technology - NextWindow Desktop 6S 

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5 point multi-touch 


Windows 8 certified 

Sizes 17” to 30”



Optical Imaging technology NextWindow 

NextWindow ProfileTouch




Camera bar Attachment straps 

NextWindow Overlay Touch Panel 2406 USB




NextWindow Overlay Touch Panel 2406 USB




Multi-Touch Interactive Whiteboard




Model No VB-83MT VB-90MT VB-108MT 

Active area (Diagonal) 78" 85" 100" 

Size 1800*1470*125 mm 1945*1560*130 mm 2500*1570*130 mm 

Weight 55 kg 66 kg 85 kg 

Projection Proportion 4:3 4:3 16:9 

Touch Technology Optical Infrared Imaging 

Input Method Touching and writing by finger or any untransparent objects 

Interface 5M USB2.0 cable 

Touch Resolution 32767*32767 

Touch Accuracy ±0.1 mm 

Interactive multi touch Whiteboard 

with Optical Infrared Imaging






Acoustic pulse recognition technology



Acoustic pulse recognition technology 

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the Acoustic Pulse Recognition (APR) touchscreen consist 

of a glass overlay with 4 piezoelectric transducers attached 

to the back surface 

the transducers pick up the acoustic wave generated upon 

a touch, and convert it to an electronic signal 

the signal is then digitized by the controller and compared 

to a prerecorded acoustic profile for every position on the 

glass 

the cursor position is instantly updated to the touch 

location




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Benefits 

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optics and durability of pure glass 

works with finger, glove, pen, credit card, fingernail 

resistant to water, dust, grease 

works even with scratches 

excellent drag performance 

one time factory calibration, no drift 

small and large sizes 

palm rejection




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Specification 

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input methods: finger, finger nail, gloved hand, or stylus 

activation 

light transmission: 90% ±5 

positional accuracy: 1% max. error 

touch activation force: typically 55 to 85 grams




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Applications 

• restaurant and hospitality automation 

• retail, Point-of-Sale (POS) terminals 

• pharmacy automation 

• industrial automation 

• office automation



Near Field Imaging technology 

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two laminated glass sheets with a 

patterned transparent, conductive 

layer between 

an excitation AC waveform supplied 

to the conductive layer to generate a 

low strength electrostatic field 

the near field is modulated by finger 

contact with the front layer of glass 

a resultant differential signal is 

created, making it possible by the 

system firmware to accurately 

recognizes the location of the touch



Near Field Imaging technology 

Advantages: 

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excellent image clarity and high 

transmissivity 

can be operated with gloves through moisture, dirt, 

and other surface contaminants 

stable over extreme environmental conditions 

can withstand scratches and other surface damage 

caused by abrasives, chemicals, or vandalism 

Disadvantages: 

• very expensive and requires complex circuits and 

technology


Touch panels market forecast


Touch panels market forecast 

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Projected-capacitive touch has grown very fast in the last few 

years since it was first popularized by iPhone and iPod 

Projected capacitive is the first serious challenger to the 

long-term dominance of analog resistive in the touch-screen 

world 

Optical-imaging touchscreen technology can be very cost- 

effective in large sizes (>10 inch) because it requires only 

two cameras and an infrared source, as optical imaging has 

taken off, more companies are entering the market 

Surface acoustic wave (SAW) has been one of the 

workhorses of the touch industry for over 20 years. It has 

been widely used in kiosks and other public applications. 

From 2009, it has supported twotouch.

Touch panels principle of operation

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