TOUCH SCREEN tECHNOLOGY (a Comparative intro)

-kashif iqbalEce 7th sem

G.B. PANT ENGG. COLLEGE

introduction

Whether it’s on a mobile device, tablet, or medical device, technology in the field of electronics give tremendous revolution in passed decades.

One of the revolution can be easily seen in screen that plays an important role in making devices highly usable as it helps in direct interaction of user with the device but there exist difficulty in using input devices such as a mouse or keyboard (key pad).

Now the scenario has changed and we have a new technology in screen called Touch Screen Technology which provide a natural interface with the device

This technology means as simple as its name that is Touch the Screen and Activate Instructions (TSAI). Instead of the keyboard (keypad) or mouse we can operate or stimulate an instruction or command by touching on the screen

Evolution……. Of Touch 1960s

First touch screen to be a capacitive touch screen invented by E.A. Johnson at the Royal Radar Establishment, Malvern, UK, around 1965 – 1967

1990sThe nineties introduced smart phones and handhelds with touch screen technology. In 1993, Apple released the Newton PDA, equipped with handwriting recognition; and IBM released the first smart phone called Simon, which featured a calendar, note pad, and fax function, and a touch screen interface that allowed users to dial phone numbers.

2000sIn 2002, Microsoft introduced the Windows XP Tablet edition and started its entry into touch technology

TYPES OF TOUCH SCREEN TECHNOLOGY

Capacitive Touch Screen Resistive Touch Screen Acoustic touch Screen Infrared touch Screen Optical Touch Screen Dispersive Touch Screen

Touch Screen – Construction & working

ContructionThe key goals (while making touch ) are to recognize one or more fingers touching a display, to interpret the command that this represents, and to communicate the command to the appropriate application.

In the most popular techniques, there are typically four layers:

Top polyester coated with a transparent metallic conductive coating on the bottom

Adhesive spacer

Glass layer coated with a transparent metallic conductive coating on the top

Adhesive layer on the backside of the glass for mounting.

WorkingThere are three components used in touch screen technology for its working

Touch Sensor:- A touch screen sensor is a clear glass panel with a touchresponsive surface. The touch sensor/panel is placed over a display screen so that the responsive area of the panel covers the viewable area of the video screen. The sensor generally has an electrical current or signal going through it and touching the screen causes a voltage or signal change. This voltage change is used to determine the location of the touch to the screen.

Controller:- The controller, is the hardware that connects between the touch sensor and the PC or other devices. It converts the voltage changes on the sensor into signals and translates it into information that PC or other devices can understand. Controller is usually installed inside the monitor (or screen of other devices) or it is housed in a plastic case for external touch addons/overlays

  Software:- Software contains drivers that allows the touchscreen and computer to work

together and tells the computer, smartphone, game device, etc, what's happening on the sensor and the information coming from the controller. Who's touching what where; and allows the computer or smart phone to react accordingly.

Types of TouchSingle Touch

Single Touch occurs when a finger or stylus creates a touch event on the surface of a touch sensor or within a touch field so it is detected by the touch controller and the application can determine the X,Y coordinates of the touch event.

Single touch using finger

Single touch using stylus

Multi-TouchThe term "multi-touch" is now in common use to describe any touch screen that can recognize more than one point of contact; in effect the use of two or more fingers simultaneously

Resistive Touch Screen

Resistive LCD touchscreen monitors rely on touch overlay, which is composed of a flexible top layer and a rigid bottom layer separated by insulating dots, attached to a touchscreen controller.

The inside surface of each of the two layers is coated with a transparent metal oxide coating of Indium Tin Oxide (ITO) that facilitates a gradient across each layer when voltage is applied.

Pressing the flexible top sheet creates electrical contact between the resistive layers, producing a switch closing in the circuit. The control electronics alternate voltage between the layers and pass

the resulting X and Y touch coordinates to the touchscreen Controller.

The touchscreen controller data is then passed on to the computer operating system for processing.

Fig. : Resistive touch screen

Resistive Technology is divided into two broad categories:

• Four-wire resistive technology :- It uses both the upper and lower layers in the touchscreen "sandwich" to determine the X and Y coordinates. Typically constructed with uniform resistive coatings of ITO on the inner sides of the layers and silver buss bars along the edges, the combination sets up lines of equal potential in both X and Y.

Resistive Technology is divided into two broad categories

In the illustration below, the controller first applies 5V to the back layer. Upon touch, it probes the analog voltage with the coversheet, reading 2.5V, which represents a left-right position or X axis.

It then flips the process, applying 5V to the coversheet, and probes from the back layer to calculate an up-down position or Y axis.

At any time, only three of the four

wires are in use.

Four wire Resistive Touch screen

5-Wire Resistive Touchscreen

In the five-wire design, one wire goes to the coversheet (E) which serves as the voltage probe for X and Y.

Four wires go to corners of the back glass layer (A, B, C, and D). The controller first applies 5V to corners A and B and grounds C and D, causing voltage to flow uniformly across the screen from the top to the bottom.

Upon touch, it reads the Y voltage from the coversheet at E. Then the controller applies 5V to corners A and C and grounds B and D, and reads the X voltage from E again.

Copararision between Resitive and capacitive

ADVANTAGES DISADVANTAGE

Value solution Reduced optical clarity

Activated by any stylus or finger or glove inputs

Polyester surface can be damaged

High touch point resolution

Low cost sensors & power requirements

Not affected by dust or water

Extremely durable Requires bare finger or capacitive stylus

Very accurate Scratch can affect operation

Good optical clarity

Good resolution

Resistiv

e

Capacitiv

e

Capacitive Touch Screen

A capacitive touch screen panel is coated with a material (metal oxide ) that stores electrical charges. When the panel is touched, a small amount of charge is drawn to the point of contact.

Circuits located at each corner of the panel measure the charge and send the information to the controller for processing.

Capacitive touch screen panels must be touched with a finger unlike resistive and surface wave panels that can use fingers and stylus.

Surface capacitive technologyIn this technology, only one side of the insulator is coated with a conductive layer. A small voltage is applied to the layer, resulting in a uniform electrostatic field. When touches surface a capacitor is dynamically formed. The sensor's controller can determine the location of the touch indirectly from the change in the capacitance as measured from the four corners of the panel.

it is moderately durable, has limited resolution and is prone to false signals from parasitic capacitive coupling. It is therefore most often used in simple applications such as industrial controls and kiosks

Projected capacitive technologyProjected 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. A finger on a grid of conductive traces changes the capacitance of the nearest traces. This change in trace capacitance is measured and finger position is computed. The use of an X-Y grid permits a higher resolution than resistive technology. Projected capacitive touch screens are clear, durable, solid state, scratch resistant and allow gloved hand use.

Fig. Capacitive Touch Screen

Acoustic wave touch screen

Because of its high optical clarity and accuracy, acoustic wave technology is typically used in kiosk applications.

Acoustic wave touch screens use transducers mounted at the edge of a glass overlay to emit ultrasonic sound waves along two sides. These waves are reflected across the surface of the glass and received by sensors. A finger or other soft tipped stylus absorbs some of the acoustic energy and the controller measures the amplitude change of the wave to determine touch location.

Fig. Acoustic Touch Screen

Infrared touch screens are primarily used for large displays, banking machines, and in military applications.

Infrared touch screens are based on light-beam interruption technology. Instead of an overlay on the surface, a frame surrounds the display. The frame has light sources, or light emitting diodes (LEDs) on one side and light detectors on the opposite side, creating an optical grid across the screen.When an object touches the screen, the invisible light beam is interrupted, causing a drop in the signal received by the photo sensors.

Infrared Touch Screens

Fig. Infrared Touch Screen

Optical Touch Screens

Optical touch screen technology is ideal for large LCD and plasma displays up to 100" diagonal.Optical touch screen technology uses two line scanning cameras located at the corners of the screen.

The cameras track the movement of any object close to the surface by detecting the interruption of an infra-red light source.

The light is emitted in a plane across the surface of the screen and can be either active (infra-red LED) or passive (special reflective surfaces).

Fig. Optical Touch Screen

Dispersive Introduced in 2002 by 3M, this system uses sensors to detect the Piezoelectricity in the glass that occurs due to a touch. Complex algorithms then interpret this information and provide the actual location of the touch.The technology claims to be unaffected by dust and other outside elements, including scratches. Since there is no need for additional elements on screen, it also claims to provide excellent optical clarity. Also, since mechanical vibrations are used to detect a touch event, any object can be used to generate these events, including fingers and stylus. A downside is that after the initial touch the system cannot detect a motionless finger.

Fig. Dispersive Touch Screen

Advantages & Disadvantages of other touch screens

Acoustic Infrared Dispersive

Good optical clarity

Accurate excellent optical clarity

Z-axis capability No overlay, unaffected by dust

Durable glass front

Superior image, mechanical vibrations are used to detect a touch event

Acoustic Infrared

Requires finger or sound absorbing stylus

Costly

Difficult to industrialize Low reliability

Signal affected by surface liquids Parallax problems

Prone to scratches easily Accidental activation

ADVANTAGES

DISADVANTAGES

Applications

Public Information Displays Tourism displays, trade show displays, Information kiosks

Retail and Restaurant Systems valuable counter space can be saved cash registers, seating, reservation systems Item selection

Control and Automation Systems In real-time by simply touching the screen and with a graphical interface, operators can monitor and control complex operations.

Assistive Technology Personal Digital Assistants (PDAs). Other applications include Digital jukeboxes, Computerized gaming, student registration systems, Multimedia software, Financial and scientific applications Smart classes

MARKET OVERVIEW OF TOUCH SCREENS

The touch screen market's dynamics are altered by growing shipment of Apple's iPhone and iPod and recently the iPad. Projected capacitive touch technology is found to be more adopted in mobile phones and tablets, Display Search forecasts that projected capacitive will pass resistive touch technology to become the leading touch technology in 2010, measured by revenues. 

Advances in technology

Touchscreens can suffer from the problem of fingerprints on the display. This can be mitigated by the use of materials with optical coatings designed to reduce the visible effects of fingerprint oils, or oleophobic coatings as used in the iPhone 3GS,.

Using a chemical found in paint, called titanium dioxide .When exposed to sunlight creates a "chain reaction that creates free radicals, which penetrate the cell walls of bacteria and fungi and damager their DNA."

Samsung's new transparent and flexible AMOLED screens, you'll love 3M's new transparent and flexible multi-touch surface3M has developed a new type of touchscreen system that's flexible, very thin, totally transparent, durable, and capable of resolving more touch points than you have fingers (and toes).

a flexible touchscreen bracelet phone could be a reality,

Touch screen bracelet Flexible & transparent Touch screen

Future Scope

More advanced technology like the one from Japanese Company

Wacom, would bring multitouch capabilities where people can work on more than on object simultaneously.

Work is still going on to make highly reliable , durable, responsive , scratch and water proof multitouch touchscreen that can work with both hands (simultaneously) of the user with great coordination

Touch Screen capability enhance real and natural feeling of working with pc or other devices for example Drag and drop with touch is more real rather than with input devices like mouse .

The future of touch surface is touchscreen video projectors. In a restaurant, for e.g., you can place your order using the surface of the table as the touch interface, instead of using a touch screen laptop. The ability to transform any surface in a touchscreen means lower costs, making the technology more cost effective.

Thank You