Introduction ofTouch Technologies

EE174 – SJSUTan Nguyen

Touch Technologies

• Introduction• Brief History• Market and Trends• Touchscreen Technology

• Resistive• Capacitive• Surface Acoustic Wave (SAW)• Infrared LED or Optical

• Touchscreen System• Applications

Introduction• An electronic visual display that locates the coordinates of a users touch within display area• Works independently of what is being displayed on screen• Allows a display to be used as an input device, removing the keyboard and/or the mouse as the primary input device for interacting with the display's content• Can be used without any intermediate device • Being used in a wide variety of applications to improve human-computer interaction.• Because of its convenience, touchscreen technology solutions has been applied more and more to industries, applications, products and services, such as modern smartphones, video games, kiosks, navigation systems, POS, tablets, etc. . .

• Invented by E.A. Johnson (Royal Radar Est.) around 1965 for air traffic control• First "touch sensor" was developed by Dr Sam Hurst in 1971.• 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)

Brief History

Overall Touchscreen Market 2012-2017

Touchscreen Market 2007-2018 by Technology (Units)

Touchscreen Technology

There are four different technologies used to make touchscreens today: • Resistive• Capacitive (Surface and Projected

Capacitive)• Surface Acoustic Wave (SAW)• Infrared LED or Optical

The Big Three of Touchscreen Technology

• Resistive Touchscreens are the most common touchscreen technology. They are used in high-traffic applications and are immune to water or other debris on the screen. Resistive touchscreens are usually the lowest cost touchscreen implementation. Because they react to pressure, they can be activated by a finger, gloved hand, stylus or other object like a credit card. • Surface Capacitive Touchscreens provide a much clearer display than the plastic cover typically used in a resistive touchscreen. In a surface capacitive display, sensors in the four corners of the display detect capacitance changes due to touch. These touchscreens can only be activated by a finger or other conductive object. • Projected Capacitive Touchscreens are the latest entry to the market. This technology also offers superior optical clarity, but it has significant advantages over surface capacitive screens. Projected capacitive sensors require no positional calibration and provide much higher positional accuracy. Projected capacitive touchscreens are also very exciting because they can detect multiple touches simultaneously.

Resistive Technology• 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• Any material can trigger sensors

Indium Tin Oxide (ITO)

Polyethylene (PET)

Types:• 4-wire (low cost, short life) is common in mobile devices• 5-wire (higher cost, long life) is common in stationary devices• 6-wire & 7-wire, 8-wire = replacement only

Constructions• Film (PET) + glass (previous illustration) is the most common• Film + film (used in some cellphones) can be made flexible• Glass + glass is the most durable; automotive is the primary use• Film + film + glass, others…

Analog Resistive

Analog Resistive

Size range• 1” to ~24” (>20” is rare)Controllers• Many sources• Single chip, embedded in chipset/CPU, or “universal” controller boardAdvantages• Works with finger, stylus or any non-sharp object• Lowest-cost touch technology• Widely available (it’s a commodity)• Easily sealable to IP65 or NEMA-4• Resistant to screen contaminants• Low power consumption

Analog ResistiveDisadvantages• Not durable (PET top surface is easily damaged)• Poor optical quality - The flexible top layer has only 75%-80% clarity• If the ITO layers are not uniform, the resistance will not vary linearly across the sensor. Measuring voltage to 10 or 12-bit precision is required, which is difficult in many environments. • No multi-touch• Require periodic calibration to realign the touch points with the underlying LCD image.

Applications• Mobile devices (shrinking)• Point of sale (POS) terminals• Automotive• Industrial• Wherever cost is #1

PET: Polyethylene Terephthalate

Analog Resistive

Suppliers• Young Fast, Nissha, Nanjing Wally, Truly, EELY, Mutto, J-Touch…• 60+ suppliers

Market trends• Analog resistive is shrinking in units and revenue

● P-cap dominates in most consumer applications• Analog resistive is still significant in commercial applications

● Especially POS and industrial-control terminals

Surface Capacitive

The same phase voltage is imposed to the electrodes on the four corners, then a uniform electric field will be forming over the panel. When a finger touches on the panel, electrical current will flow from the four corners through the finger. Ratio of the electrical current flowing from the four corners will be measured to detect the touched point. The measured current value will be inversely proportional to the distance between the touched point and the four corners.

Advantages:• Surface capacitive technology is suitable for large size monitors.• Surface capacitive sensor can respond to light touch, and no pressure force is needed for detection• Visibility is high because structure is only one glass layer.• Surface capacitive is structurally tough as it is made of one sheet of glass.• Surface capacitive does not get affected by moist, dust, or grease.• Parallax is minimized in surface capacitive.• Surface capacitive has high resolution and high response speed.• Highly sensitive (very light touch)

Disadvantages:• Surface capacitive can detect touches by fingers only• nurface capacitive technology does not support multi-touch.• Surface capacitive touch screen is likely to be affected by noise. Recently, tolerance for noise has been improved with various methods such as noise shielding.

Surface Capacitive

Self-Projected Capacitive

● Uses rows and columns of conductors (overlayed in a grid pattern) ● One capacitor for each row and for each column ● A controller detects changes in capacitance for each row & column ● Controller determines an (x,y) coordinate based on the changes

Projected Capacitive

• Uses sensors to measure capacitance, when finger touches screen, capacitance increases• Typical Capacitor Values:

Cp ~ 15 pFCf ~ .5 pF

• Requires capacitance between object and sensor

Mutual Capacitance

• Uses an array of capacitors (located at each intersection of conductor grid)

Mutual Capacitance• Capable of recognizing multiple touches (Multitouch)

http://large.stanford.edu/courses/2012/ph250/lee2/docs/art6.pdf

Surface Acoustic Wave (SAW)• SAW touch screen consists of

one glass sheet with transmitting transducers, receiving transducers, and reflectors.

• Transmitting transducers generate ultrasonic waves that travel over the panel surface.

• The ultrasonic waves are reflected by the reflectors and received by the receiving transducers.

• SAWs are sent out from the transmitting transducers, and traveling along the edge of panel. The reflectors located on the edge of the panel change directions of the SAWs at the angle of 90 degrees, thus the SAWs travel over the panel.

Once the SAWs reached the other side of the panel, their directions get changed again by the reflectors located on the other side, and travel toward the receiving transducers. Once the SAWs are received by the receiving transducers, they will be converted into electric signals.

There are routes on which the SAWs travel from the transmitting transducers to the receiving transducers. 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. Thus, the sensor will recognize which route was touched, and locate the touched point.

Surface Acoustic Wave (SAW)

Advantages:• Visibility is excellent because it consists of one glass layer. • SAW touch screen is notable for its durability. Even though the panel surface gets scratched, its sensing function will not be affected.• It is relatively easy to build a large size touch screen in SAW technology.• SAW touch screen does not get affected by external electric noise.• Accuracy of detecting touched points does not get affected by environment nor passage of time. Thus, it is free of maintenance.• Resolution is relatively high.

Disadvantage:• The frame areas need to be wide because transducers are located.• 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.

Surface Acoustic Wave (SAW)

Surface Acoustic Wave (SAW)Size range

• 6” to 52”Advantages• Visibility is excellent because it consists of one glass layer. • Finger, gloved hand & soft-stylus activation• Notable for its durability; can be vandal-proofed with tempered

or CS glass• SAW touch screen does not get affected by external electric

noise.• Accuracy of detecting touched points does not get affected by

environment nor passage of time. Thus, it is free of maintenance.

Disadvantages• Very sensitive to any surface contamination, including water• Relatively high activation force (50-80g typical)• Requires “soft” (sound-absorbing) touch object• Can be challenging to seal

Surface Acoustic Wave (SAW)

Suppliers• Elo Touch Solutions and General Touch have >90%

share• <10 suppliersMarket trends• Two-touch and zero-bezel SAW should help reduce

loss of share to p-cap in commercial applications• SAW will continue to grow moderately through

2017Applications• 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 on.

• An infrared touchscreen uses a grid pattern of LEDs and light-detector photocells arranged on opposite sides of the screen. • The LEDs shine infrared light in front of the screen—a bit like an invisible spider's web. • If you touch the screen at a certain point, you interrupt two or more beams. A microchip inside the screen can calculate where you touched by seeing which beams you interrupted. Since you're interrupting a beam, infrared screens work just as well whether you use your finger or a stylus.

Traditional Infrared

Traditional InfraredVariations• Bare PCB vs. enclosed frame; frame width & profile

height;no glass substrate; enhanced sunlight immunity; force-sensingSize range• 8” to 150”Controllers• Mostly proprietary, except IRTouch (China)Advantages• Scalable to very large sizes• Multi-touch capable (only 2 touches, and with some

“ghost” points)• Can be activated with any IR-opaque object• High durability, optical performance and sealability• Doesn’t require a substrate

Disadvantages• Profile height (IR transceivers project above touch

surface)• Bezel must be designed to include IR-transparent

window• Sunlight immunity can be a problem in extreme

environments• Surface obstruction or hover can cause a false

touch• Low resolution• High costApplications• Large displays (digital signage)• POS (limited)• KiosksSuppliers• IRTouch Systems, Minato, Nexio, OneTouch, SMK,

Neonode…• 10+ suppliers

Traditional Infrared

COMPONENTS OF TOUCHSCREEN

A basic touchscreen system has three main components:

• A touch screen.• A controller• Software driver.

The touchscreen is an input device, so it needs to be combined with a display and a PC or other device to make a complete touch input system.

Touch Screen

The touchscreen is the face of a touchsystem and the user's first contact point with the system. Its importance cannot be overstated, since it defines the quality and tactile feel of the touch system, and offers the only user interface. Key functional properties of the touchscreen are its optical transparency, its hardiness to wear and tear, and its touch accuracy. In all these areas, five-wire technology excels.

Controller• The controller - essentially the brain of the touch system - contains a microprocessor, analog-to-digital converters, and microchips to enable communication with the host PC. • The controller powers the touchscreen, controls the excitation, and interprets the information received from the touchscreen. • The controller filters the returning touchscreen data and converts it into raw touch coordinates, which are then sent to the PC by a digital software protocol. • A good controller will also perform substantial error-checking to detect abnormal or inconsistent touches and filter them out. • The controller determines what type of interface/connection you will need on the PC. Controllers are available that can connect to a Serial/COM port (PC) or to a USB port (PC or Macintosh). • Specialized controllers are also available that work with DVD players and other devices.

Software Driver

• The driver is a software update for the PC system that allows the touchscreen and computer to work together. • The driver software, residing on the host PC, is required to manage the raw coordinate data coming from the controller, apply calibration algorithms, position the mouse cursor, and generate mouse clicks. • Other important tasks include routines to define the video alignment parameters, and screening of incoming touch data for errors, inconsistencies, and integrity. • Good driver software will also offer diagnostic information in troubleshooting situations.

Touch Technologies by Size & Application

Touch Technologies by Materials & Process

Touch Is An Indirect Measurement

http://www.walkermobile.com/Touch_Technologies_Tutorial_Latest_Version.pdf

http://ijcaonline.net/volume6/number8/pxc3871433.pdfhttp://www.dmccoltd.com/english/museum/touchscreens/technologies/https://www.touchsystems.com/surfacecapacitive

slideplayer.com/slide/1722274/https://www.sparkfun.com/datasheets/LCD/HOW%20DOES%20IT%20WORK.pdfhttps://www.google.com/search?q=ibm+simon+ebay&rlz=1C1AVNC_enUS582US583&oq=ibm+sim&aqs=chrome.2.0j69i57j0l4.12508j0j8&sourceid=chrome&es_sm=122&ie=UTF-8#q=royal+radar+establishment+touch+screen+picturehttp://www.elotouch.com/resources/newtotouch/hardware.asphttp://www.dawar.com/touch-screen-tools Http://www.cypress.com/?docID=17212http://www.computerworld.com/article/2491831/computer-hardware/how-it-works--the-technology-of-touch-screens.htmlhttp://www.explainthatstuff.com/touchscreens.htmlhttp://www.computerworld.com/article/2491831/computer-hardware/how-it-works--the-technology-of-touch-screens.html?page=3

References:

• Optical:• Traditional Infrared• Waveguide Infrared (DVT by RPO)• Multi-Touch Infrared• Camera-Based Optical• Planar Scatter Detection (PSD by FlatFrog)• Vision-Based

• Other Touch Technologies• Force-Sensing

• Conclusions• Touch Technology vs. Application• Usability, Performance, and Integration

Characteristics• Touch Technology Primary Advantages and

Flaws• Predictions for the Future

Touch Technologies

Two Basic Categories of Touch

• Opaque (non-transparent) touch• Dominated by the controller chip suppliers

• Atmel, Cypress, Synaptics, etc.• One technology (projected [self]

capacitive)• Sensor is typically developed by the

device OEM• Notebook touchpads are the highest-

revenue application• Synaptics, Alps and ELAN have the

majority of the market• Sensors are all two-layer projected

capacitive• Transparent touch on top of a display

• Dominated by the touch module manufacturers (150+ worldwide)

• 6 fundamental technologies with ~20 types