Touch Technology

Edited by Edward Inyoung Cho

Touch Technology • Display manufacturers and chip manufacturers worldwide have acknowledged the trend toward acceptance of

touch screens as a highly desirable user interface component and have begun to integrate touch screen function-ality into the fundamental design of their products.

Touch Screen Panel

Resistive Capacitive Infrared Surface Acoustic Wave

Mounted touch In cell touch

Resistive Touch A resistive touch screen panel is composed of several layers, the most important of which are two thin, electrically conductive layers separated by a narrow gap. When an object, such as a finger, presses down on a point on the panel's outer surface the two metallic layers become connected at that point: the panel then behaves as a pair of voltage dividers with connected outputs. This causes a change in the electrical current, which is registered as a touch event and sent to the controller for processing. The cover sheet consists of a hard outer surface with a coated inner side. When the outer layer is touched it causes the conductive layers to touch creating a signal that the analog con-troller can interpret and determine what the user wants to be done. Resistive touch is used in restaurants, factories and hospitals due to its high resistance to liquids and contaminants. A major benefit of resistive touch technology is it is extremely cost-effective. One disadvantage of resistive technology is its vulnerability of being damaged by sharp objects.

Resistive Panel Production Flow

Source from Display Bank

Capacitive Touch

A capacitive touch screen panel consists of an insulator such as glass, coated with a transparent conductor such as

indium tin oxide (ITO). As the human body is also an electrical conductor, touching the surface of the screen results

in a distortion of the screen's electrostatic field, measurable as a change in capacitance. Different technologies may

be used to determine the location of the touch. The location is then sent to the controller for processing. Unlike a

resistive touch screen, one cannot use a capacitive touch screen through most types of electrically insulating mate-

rial, such as gloves;

Pro. Cap. Touch Technology• Film and Glass Type • Glass Type

– Apple iPhone: X and Y electrode on glass – Samsung Galaxy S : Multi coating on glass

• DPW : Direct Patterned Window. Direct Coating on Glass

Dual Coating Type

Single Coating Type

Direct Patterned Window

Projected Capacitive

Touch

Film Type

Glass Type

Capacitive Touch Controller

Pro Cap Touch Control IC consists of Signal source, Multiplexer, A/D converter.

Projected Capacitive Touch

Projected Capacitive Touch (PCT) technology is a capacitive technology which permits more accurate and flexible operation, by

etching the conductive layer. An X-Y grid is formed either by etching a single layer to form a grid pattern of electrodes, or by

etching two separate, perpendicular layers of conductive material with parallel lines or tracks to form the grid (comparable to the

pixel grid found in many LCD displays).

The greater resolution of PCT allows operation without direct contact, such that the conducting layers can be coated with further

protective insulating layers, and operate even under screen protectors, or behind weather and vandal-proof glass. Due to the

top layer of a PCT being glass, PCT is a more robust solution versus resistive touch technology. Depending on the implementa-

tion, an active or passive stylus can be used instead of or in addition to a finger.

Pro. Cap. Touch Sensing Pattern

Touch Panel Configuration

iPhone Touch• 0.5 ㎜ touch panel on Glass • OCA Film, ITO in upper and bottom of Glass • Metal (Al+Mo) Coating for reducing Vessel width and enlarge the Display

Galaxy S Touch : On Cell Touch

Galaxy S Touch Pattern

DPW(Direct Patterned Window)

Pro. Cap. Touch Comparison

ITO Film type Dual Coating Type

Single layer Multi Coating Type

Direct Patterned Win-dow

Price Good Bad Bad Very Bad

Vessel Width Bad Very good Very good Very good

Thickness Bad Very bad Very good Very good

Operation Per-formance

Good Good Good Good

Large Display Very bad Good Good Very bad

Infrared Touch An infrared touchscreen uses an array of X-Y infrared LED and photodetector pairs around the edges of the screen to detect a disruption in the pattern of LED beams. These LED beams cross each other in vertical and horizontal patterns. This helps the sensors pick up the exact location of the touch.

A major benefit of such a system is that it can detect essentially any input including a finger, gloved finger, stylus or pen.

It is generally used in outdoor applications and point of sale systems which can't rely on a conductor (such as a bare finger) to activate the touchscreen. Unlike capacitive touchscreens, infrared touch screens do not require any patterning on the glass which in-creases durability and optical clarity of the overall system

Acoustic Touch

The key to the invention is that a touch at each position on the glass generates a unique sound. Four tiny transducers attached to the edges of the touch screen glass pick up the sound of the touch. The sound is then digitized by the controller and compared to a list of prerecorded sounds for every position on the glass. The cursor position is instantly updated to the touch location.

Surface acoustic wave (SAW) technology uses ultrasonic waves that pass over the touch-screen panel. When the panel is touched, a portion of the wave is absorbed. This change in the ultrasonic waves registers the position of the touch event and sends this information to the controller for processing. Surface wave touchscreen panels can be damaged by outside elements. Contaminants on the surface can also interfere with the functionality of the touch-screen

Gestural Interface • Wired gloves. These can provide input to the computer about the position and rotation of the hands using mag-

netic or inertial tracking devices. Furthermore, some gloves can detect finger bending with a high degree of accu-racy (5-10 degrees), or even provide haptic feedback to the user, which is a simulation of the sense of touch. [18] The first commercially available hand-tracking glove-type device was the DataGlove, [19] a glove-type device which could detect hand position, movement and finger bending. This uses fiber optic cables running down the back of the hand. Light pulses are created and when the fingers are bent, light leaks through small cracks and the loss is registered, giving an approximation of the hand pose.

• Depth-aware cameras. Using specialized cameras such as time-of-flight cameras, one can generate a depth map of what is being seen through the camera at a short range, and use this data to approximate a 3d represen-tation of what is being seen. These can be effective for detection of hand gestures due to their short range capa-bilities.[20]

• Stereo cameras. Using two cameras whose relations to one another are known, a 3d representation can be ap-proximated by the output of the cameras. To get the cameras' relations, one can use a positioning reference such as a lexian-stripe or infrared emitters.[21] In combination with direct motion measurement (6D-Vision) gestures can directly be detected.

• Controller-based gestures. These controllers act as an extension of the body so that when gestures are performed, some of their motion can be conveniently captured by software. Mouse gestures are one such exam-ple, where the motion of the mouse is correlated to a symbol being drawn by a person's hand, as is the Wii Remote, which can study changes in acceleration over time to represent gestures. [22][23][24] Devices such as the LG Electronics Magic Wand, the Loop and the Scoop use Hillcrest Labs' Freespace technology, which uses MEMS accelerometers, gyroscopes and other sensors to translate gestures into cursor movement. The software also compensates for human tremor and inadvertent movement. [25] [26] [27]

• Single camera. A normal camera can be used for gesture recognition where the resources/environment would not be convenient for other forms of image-based recognition. Although not necessarily as effective as stereo or depth aware cameras, using a single camera allows a greater possibility of accessibility to a wider audience. [28]

Common Multi-Touch Ges-ture

Tap Double Tap Long Press Scroll Pan

Flick Two Finger Tap Two Finger Scroll Pinch Two hand Pinch

Unpinch Two hand Un-pinch

Rotate Two hand rotate

Gorilla Arm

• "Gorilla arm" was a side-effect of vertically-oriented touch-screen or light-pen use. In periods of prolonged use, users' arms began to feel fatigue and/or discomfort. This effect contributed to the decline of touch-screen input despite initial popularity in the 1980s.[40][41]

• Gorilla arm is not a problem for short-term use, since they only in-volve brief interactions which do not last long enough to cause go-rilla arm

Technology Comparison(1)

Technology Strong Weak

Resistive Easy mounting Fast response High resolution

Low light transmittance Very fragile

Capacitive High Durability Fast Response Multi touch support

Only Electrode Difficult in mounting

Infrared High Durable High light transmittance Multi touch support

Difficult in mounting Large vessel size Low response time Error in outside use Limited in design

Acoustic High durability High light transmittance

Weak in liquid Weak in contamination of sensor

Technology Comparison(2)

Touch Market ECO System

Production Flow of Melfas

IC

TSM

IC

TSM

Source from MELFAS IR, Nov. 2011

Major Touch Sensor Controller Sup-plier

MELFAS ATMEL Cypress Synaptics

Korea US US US

Touch ICTouch Screen Module

Touch Key Module Touch IC Touch IC

Touch ICTouch Screen Panel Touch Key Module

Turnkey Solution IC IC IC & Module

DPW(Direct Patterned Window)1-layer solution 2-layer solution

2-layer solution 2-layer solution 2-layer solution Touch pad

Touch Market Forecast(1)

Touch Screen market projected US$10B in 2013Capacitive touch screen share 80% of Market in 2013 Tablet PC shipment 50M in 2011 to 130M in 2013

Worldwide Touch Screen Market (Sales revenue in $100M)

Worldwide Touch Mobile Phone Market (Shipment Unit : Million)

Source from Melfas IR, Nov. 2011

Touch Phone Market Forecast(3)Global Mobile Phone-Touch Phone Market Forecast (unit: Million)

Mobile Phone Touch Phone Touch adaptation rate

Source from : Displaybank