1. Introduction of Touch Technologies
EE174 – SJSU
Tan Nguyen

2. Touch Technologies Introduction Brief History Market and Trends
Touchscreen Technology
Resistive
Capacitive
Surface Acoustic Wave (SAW)
Infrared LED or Optical
Touchscreen System
Applications

3. 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. . .

4. Brief History
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)

5. Overall Touchscreen Market 2012-2017

6. Touchscreen Market 2007-2018 by Technology (Units)

7. 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

8. 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.

9. 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)

10. Analog Resistive Types: Constructions
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…

11. Analog Resistive Size range Controllers Advantages
1” to ~24” (>20” is rare)
Controllers
Many sources
Single chip, embedded in chipset/CPU, or “universal” controller board
Advantages
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

12. Analog Resistive Disadvantages Applications
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

13. Analog Resistive Suppliers Market trends
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

14. 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.

15. Surface Capacitive Advantages: Disadvantages:
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.

16. 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

17. Projected Capacitive
Uses sensors to measure capacitance, when finger touches screen, capacitance increases
Typical Capacitor Values:
Cp ~ 15 pF
Cf ~ .5 pF
Requires capacitance between object and sensor

19. Mutual Capacitance
Uses an array of capacitors (located at each intersection of conductor grid)

20. Mutual Capacitance
Capable of recognizing multiple touches (Multitouch)

23. 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.

24. Surface Acoustic Wave (SAW)
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.

25. 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.

26. 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

27. Surface Acoustic Wave (SAW)
Suppliers
Elo Touch Solutions and General Touch have >90% share
<10 suppliers
Market 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 2017
Applications
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.

28. Traditional Infrared
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.

29. Traditional Infrared Variations Size range Controllers
Bare PCB vs. enclosed frame; frame width & profile height;
no glass substrate; enhanced sunlight immunity; force-sensing
Size 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

30. Traditional Infrared Disadvantages Applications Suppliers
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 cost
Applications
Large displays (digital signage)
POS (limited)
Kiosks
Suppliers
IRTouch Systems, Minato, Nexio, OneTouch, SMK, Neonode…
10+ suppliers

31. 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.

32. 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.

33. 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.

34. 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.

35. Touch Technologies by Size & Application

36. Touch Technologies by Materials & Process

37. Touch Is An Indirect Measurement

38. References:
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39. Touch Technologies 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

40. 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