TOUCH SCREENTOUCH SCREEN TECHNOLOGY TECHNOLOGY

By, Pavan Kumar M.T. & Prathik G.

INTRODUCTIONINTRODUCTION

A touchscreen is a display that can detect the presence and location of a touch within the display area.

The term generally refers to touch or The term generally refers to touch or contact to the display contact to the display ofof the device by the device by

a finger or hand.a finger or hand.Touchscreen can also sense other Touchscreen can also sense other

passive objects, such as a passive objects, such as a stylus.

Continues…….Continues…….

The touchscreen has two main attributes:The touchscreen has two main attributes:

1.1. It enables one to interact with what is It enables one to interact with what is displayed directly on the screen, where it displayed directly on the screen, where it is displayed, rather than indirectly with a is displayed, rather than indirectly with a mouse or touchpad. mouse or touchpad.

2.2. It lets one do so without requiring any It lets one do so without requiring any intermediate device, again, such as a intermediate device, again, such as a stylus that needs to be held in the hand. stylus that needs to be held in the hand. Such displays can be attached to Such displays can be attached to computers or, as terminals, to networks. computers or, as terminals, to networks.

HistoryHistoryTouchscreens emerged from academic and

corporate research labs in the second half of the 1960s.

One of the first places where they gained some visibility was in the terminal of a computer-assisted learning terminal that came out in 1972 as part of the PLATO project.

The HP-150 from 1983 was probably the world's earliest commercial touchscreen computer.

It doesn't actually have a touchscreen in the strict sense, but a 9" Sony CRT surrounded by infrared transmitters and receivers which detect the position of any non-transparent object on the screen.

DevelopmentDevelopment

• The development of multipoint touchscreen The development of multipoint touchscreen facilitated the tracking of more than one facilitated the tracking of more than one finger on the screen, thus operations that finger on the screen, thus operations that require more than one finger are possible. require more than one finger are possible.

• These devices also allow multiple users to These devices also allow multiple users to interact with the touchscreen simultaneously.interact with the touchscreen simultaneously.

• With the influence of the multi-touch-enabled With the influence of the multi-touch-enabled iPhone and the Nintendo DS, the touchscreen iPhone and the Nintendo DS, the touchscreen market for mobile devices is projected to market for mobile devices is projected to produce 5 billion in 2009.produce 5 billion in 2009.

ConstructionConstruction

There are several principal ways to build a touchscreen:There are several principal ways to build a touchscreen:

• In the most popular techniques, the capacitive or resistive In the most popular techniques, the capacitive or resistive approach, manufactures coat the screen with a thin, transparent approach, manufactures coat the screen with a thin, transparent metallic layer.metallic layer.

• When a user touches the surface, the system records the change When a user touches the surface, the system records the change in the electrical current that flows through the display.in the electrical current that flows through the display.

• Dispersive-signal technology which 3M created in 2002, measures Dispersive-signal technology which 3M created in 2002, measures the piezoelectric effect — the voltage generated when mechanical the piezoelectric effect — the voltage generated when mechanical force is applied to a material — that occurs chemically when a force is applied to a material — that occurs chemically when a strengthened glass substrate is touched.strengthened glass substrate is touched.

Continues…….Continues…….

There are two infrared-based approachesThere are two infrared-based approaches..

• An array of sensors detects a finger touching or An array of sensors detects a finger touching or almost touching the display, thereby almost touching the display, thereby interrupting light beams projected over the interrupting light beams projected over the screen.screen.

• Bottom-mounted infrared cameras record Bottom-mounted infrared cameras record screen touches.screen touches.

• In each case, the system determines the In each case, the system determines the intended command based on the controls intended command based on the controls showing on the screen at the time and the showing on the screen at the time and the location of the touch.location of the touch.

TechnologiesTechnologiesThe types of technologies that can be found are asfollows:

Resistive:Resistive:

● The resistive touch screen uses a glass panel with a uniform conductive ITO(Indium Tin Oxide) coating on the side surface.

● A PET film is a tightly suspended over the ITO coating surface of a glass panel.

Working Principle:Working Principle:

• The microprocessor applies +5V to pin (X left) on the glass panel, and the voltage is uniformly decreasing to pin (X right) for 0V because of the resistive ITO coating on the glass substrate, and the PET film is grounded.

● When the screen is touched, it pushes the conductive ITO When the screen is touched, it pushes the conductive ITO coating on the PET film. That results the electrical contact, coating on the PET film. That results the electrical contact, producing the voltages. It presents the position touched. producing the voltages. It presents the position touched.

Continues…….Continues…….• When the touchscreen is touched, a voltage on the glass substrate proportional to the X position of the touch appears on the PET film.

•This voltage is digitized by the A/D Converter and subjected to an averaging algorithm. Then it is stored and transferred to the host. Hence, the X position is produced. The next electric cycle, Y position is produced.

•Resistive touchscreen deliver cost-effective, consistent and durable performance

•Resistive technology include only 75% optical transparency and the fact that a sharp object can damage the resistive layers.

Surface Acoustic Wave:

• On the pure glass substrate, there are four piezoelectric transmitting and receiving transducers on the three corners for both the X and Y axes.• The SAW controller sends a 5 MHz electrical signal to the X-axis and Y-axis transmitting transducers..

• When the touchscreen is touched, the finger absorbs a portion of the wave passing across the surface of the panel.

• SAW can be used in any and all applications for the best possible image clarity an unlimited life.

Capacitive:

• Capacitive touchscreen is a four multi-layer glass.

• Small amount of voltage is applied to the electrodes on the four corners

• A human body is an electric conductor, so when touched the screen with a finger, a slight amount of current is drawn, creating a voltage drop. The current respectively drifts to the electrodes on the four corners.

• The capacitive system has very long life (about 225 million clicks).

Infrared:

• IR eliminates the use of glass or plastic overlay that most other touch technologies require in front of the display.

• High cost of the technology.

• IR increases the noise floor at the optical sensor

● Conventional optical-touch systems use an array of infrared (IR) light-emitting diodes (LEDs) on two adjacent bezel edges of a display, with photosensors placed on the two opposite bezel edges to analyze the system and determine a touch event.

Comparison of Technologies::

Technology Resistive SAW Infrared Capacitive

Durability: 5 years 5 years 3 years 2 years

Stability: High Higher High Ok

Transparency: Ok Good Good Ok

Touch: Anything Finger/ pen Sharp Conductive

Response time:

<10ms 10ms <20ms <15ms

Advantages & Disadvantages:

Advantages:

• User friendly.

• Fast response.

• Error free input.

• Easy to install.

• Use finger, fingernail, gloved hand, stylus or any soft-tip pointer to operate.

• Easy to clean and maintain.

• Compatible with Windows, Macintosh and Linux.

• Does not interfere mouse and keyboard function.

• Make computing easy, powerful and fun.

Disadvantages:

1)Finger stress:

Stress on human fingers when used for more than a few minutes at a time. (for example, ATMs).

2)Fingerprints:

Touchscreens can suffer from the problem of fingerprints on the display

Applications Public Access:•   MuseumsMuseums

•   Library resource guidesLibrary resource guides

•   Corporate informationCorporate information

•   Public Transportation Schedule / StatusPublic Transportation Schedule / Status

• Airport terminal passenger internet and Airport terminal passenger internet and email systemsemail systems

• Automated travel and entertainment Automated travel and entertainment ticket dispensersticket dispensers

• Shopping mall directoryShopping mall directory

Continues…….Continues…….

BusinessBusiness

•   Gas stationsGas stations

•   Point of salesPoint of sales

• RestaurantsRestaurants

•   Grocery storesGrocery stores

• Hospital and hotel directories (check-in, Hospital and hotel directories (check-in, registration)registration)

•   Banks and Financial ReportingBanks and Financial Reporting

•   Bank cash advance and teller machinesBank cash advance and teller machines

Continues…….Continues…….

Entertainment:Entertainment:

• Interactive computer gamesInteractive computer games

• CasinosCasinos

Government:Government:

●  Military control systemMilitary control system

●  Scientific research labScientific research lab

Future Touchscreens Future Touchscreens Technology:Technology:

RPO’ s Digital Waveguide Touch:RPO’ s Digital Waveguide Touch:• Minimal power requirements. Minimal power requirements.

• High inherent accuracy & precession.High inherent accuracy & precession.

• Zero-pressure touch & allows finger scrolling.Zero-pressure touch & allows finger scrolling.

• Allows100% display light output, picture definition and Allows100% display light output, picture definition and colour clarity.colour clarity.

• Low-cost & Excellent durability.Low-cost & Excellent durability.

3-dimensional Touchscreens3-dimensional Touchscreens

Conclusion:Conclusion:

• Designers are trying to use touchscreen to simplify input commands for largely unsophisticated computer users.

• Today, a larger share of population is PC literate, yet the touchscreen has become adopted by computer users of all abilities because it is simple, fast, and innovative.

• In future there is no usage of mouse and keyboards as they will be replaced by touchscreens.

References:

1. Wikipedia.

2. How stuff works.

3. Electronics for you.

Any Queries………?Any Queries………?