touch screen technology-bharadwaj

TOUCH SCREEN TOUCH SCREEN TECHNOLOGYTECHNOLOGY

Presented ByPresented By

SUBHAJIT BHARADWAJSUBHAJIT BHARADWAJ0301223250,8th sem0301223250,8th sem

Computer Sc.& Engg.Computer Sc.& Engg.

TALK FLOWTALK FLOW

INTRODUCTIONINTRODUCTION HISTORYHISTORY FUNCTIONSFUNCTIONS WORKINGWORKING DIFFRENT TOUCH SCREEN DIFFRENT TOUCH SCREEN

TECHNOLOGIESTECHNOLOGIES APPLICATIONAPPLICATION CONCLUSIONCONCLUSION

INTRODUCTIONINTRODUCTION A touch screen is a computer display screen A touch screen is a computer display screen

that is that is sensitive to human touchsensitive to human touch, allowing a , allowing a user to interact with the computer by user to interact with the computer by touching pictures or words on the screen.touching pictures or words on the screen.

A touch screen is an input device that allows users to operate a PC by simply touching the display screen which has a sensitive glass overlay placed on it .

A touch screen accepts direct onscreen inputs.

HISTORYHISTORY In 1971, the first "touch sensor" was In 1971, the first "touch sensor" was

developed by Doctor Sam Hurst (founder developed by Doctor Sam Hurst (founder of Elographics) while he was an instructor at of Elographics) while he was an instructor at the University of Kentucky.the University of Kentucky.

The University of Kentucky Research The University of Kentucky Research Foundation named it as “Elograph”. Foundation named it as “Elograph”.

The "Elograph" was not transparent like The "Elograph" was not transparent like modern touch screens.modern touch screens.

In 1974, the first true touch screen In 1974, the first true touch screen incorporating a transparent surface came.incorporating a transparent surface came.

FUNCTIONS OF TOUCH FUNCTIONS OF TOUCH SCREENSCREEN

Pressure sensitive activation-by finger or Pressure sensitive activation-by finger or stylus.stylus.

Emulates mouse functions-click, double click, Emulates mouse functions-click, double click, & drag.& drag.

Touch screen & mouse can be used Touch screen & mouse can be used concurrently.concurrently.

Durable & scratch resistant coated surface.Durable & scratch resistant coated surface. Compatible with Windows Compatible with Windows

95,98,NT,2000,XP,Macintosh,Linux.95,98,NT,2000,XP,Macintosh,Linux.

HOW DOES A TOUCHSCREEN HOW DOES A TOUCHSCREEN WORKS?WORKS?

A basic touch screen has three main A basic touch screen has three main components: components:

touch sensor touch sensor controller controller software driver software driver

1.TOUCH SENSOR1.TOUCH SENSOR

A touch screen sensor is a clear glass panel A touch screen sensor is a clear glass panel with a touch responsive surface which is with a touch responsive surface which is placed over a display screen.placed over a display screen.

The sensor generally has an electrical current The sensor generally has an electrical current or signal going through it and touching the or signal going through it and touching the screen causes a voltage or signal change. This screen causes a voltage or signal change. This voltage change is used to determine the voltage change is used to determine the location of the touch to the screen.location of the touch to the screen.

2.CONTROLLER2.CONTROLLER

The controller is a small PC card that connects between the touch sensor and the PC.

It takes information from the touch sensor and translates it into information that PC can understand.

3.SOFTWARE DRIVER3.SOFTWARE DRIVER

The driver is a software that allows the touch The driver is a software that allows the touch screen and computer to work together. screen and computer to work together.

It tells the operating system how to interpret It tells the operating system how to interpret the touch event information that is sent from the touch event information that is sent from the controller.the controller.

Most touch screen drivers today are Most touch screen drivers today are mouse-mouse-emulation type driversemulation type drivers. This makes touching . This makes touching the screen the same as clicking your mouse at the screen the same as clicking your mouse at the same location on the screen.the same location on the screen.

DIFFERENT TOUCH SCREEN DIFFERENT TOUCH SCREEN TECHNOLOGIESTECHNOLOGIES

RESISTIVERESISTIVE CAPACITIVECAPACITIVE SURFACE WAVESURFACE WAVE INFRAREDINFRARED DISPERSIVE SIGNAL DISPERSIVE SIGNAL

TECHNOLOGYTECHNOLOGY

RESISTIVE TOUCH SCREEN RESISTIVE TOUCH SCREEN TECHNOLOGYTECHNOLOGY

1.1. Polyester Film .Polyester Film .

2.2. Top Resistive Layer.Top Resistive Layer.

3.3. Conductive Transparent Metal Coating.Conductive Transparent Metal Coating.

4.4. Bottom Resistive Layer .Bottom Resistive Layer .

5.5. Insulating Dots .Insulating Dots .

6.6. Glass SubstrateGlass Substrate

Contd.Contd.

Pressing the flexible top sheet creates electrical contact with the coating on the glass.

The touch screen controller gets the The touch screen controller gets the alternating voltages between the two layers alternating voltages between the two layers and converts them into the digital X and Y and converts them into the digital X and Y coordinates of the activated area.coordinates of the activated area.

Advantages of Resistive Advantages of Resistive TechnologyTechnology

Can be activated with any device Can be activated with any device Low cost solution Low cost solution Low power consumption Low power consumption

Disadvantages of Resistive Disadvantages of Resistive TechnologyTechnology

Poorer durability compared to other Poorer durability compared to other technologies technologies

Very short life, especially considering Very short life, especially considering cosmetic wear cosmetic wear

CAPACITIVE TOUCH SCREEN CAPACITIVE TOUCH SCREEN TECHNOLOGYTECHNOLOGY

In the In the capacitive systemcapacitive system, a layer that , a layer that stores stores electrical chargeelectrical charge is placed on the glass panel. is placed on the glass panel.

When a user touches, some of the charge is When a user touches, some of the charge is transferred to the user, so the charge on the transferred to the user, so the charge on the capacitive layer decreases.capacitive layer decreases.

This decrease is measured in electrodes located This decrease is measured in electrodes located at each corner of the monitor. at each corner of the monitor.

The computer then calculates the coordinates, The computer then calculates the coordinates, from the relative differences in charge at each from the relative differences in charge at each corner. corner.

Contd.Contd.

A finger touch draws A finger touch draws current from each current from each corner.corner.

Then the controller Then the controller measures the ratio of measures the ratio of the current flow from the current flow from the corners and the corners and calculates the touch calculates the touch locationlocation

Capacitive TechnologyCapacitive Technology

ADVANTAGESADVANTAGES

More durable than More durable than resistive resistive

Higher Higher transmittance than transmittance than resistive resistive

DISADVANTAGESDISADVANTAGES

Accepts input from Accepts input from finger only. finger only.

Accuracy is Accuracy is

dependent on dependent on capacitance of capacitance of personperson

SURFACE WAVE SURFACE WAVE TECHNOLOGYTECHNOLOGY

It has a transmitting and receiving transducers for It has a transmitting and receiving transducers for both the X and Y axes.both the X and Y axes.

The touchscreen controller sends a five-megahertz The touchscreen controller sends a five-megahertz electrical signal to the transmitting transducer, which electrical signal to the transmitting transducer, which converts the signal into ultrasonic waves within the converts the signal into ultrasonic waves within the glass.glass.

These waves are directed across the front surface of These waves are directed across the front surface of

the touchscreen by an array of reflectors. the touchscreen by an array of reflectors.

Contd.Contd.

Reflectors on the opposite side gather and Reflectors on the opposite side gather and direct the waves to the receiving transducer, direct the waves to the receiving transducer, which reconverts them into an electrical which reconverts them into an electrical signal.signal.

When you touch the screen, you absorb a When you touch the screen, you absorb a portion of the wave travelling across it. portion of the wave travelling across it.

The receivers can detect a drop in amplitude The receivers can detect a drop in amplitude and thus coordinate is calculated. and thus coordinate is calculated.


Very high Very high transmittance transmittance

Very high durability Very high durability


Requires “soft” input Requires “soft” input device device

Surface obstructions Surface obstructions can cause a false can cause a false touch touch

INFRARED TOUCH SCREEN INFRARED TOUCH SCREEN TECHNOLOGYTECHNOLOGY

IR makes use of a “frame” around the IR makes use of a “frame” around the perimeter of the display. On two sides there perimeter of the display. On two sides there are closely spaced IR LEDs and on the are closely spaced IR LEDs and on the opposing two sides there are matching photo opposing two sides there are matching photo transistors. transistors.

The LEDs are turned on in sequence and the The LEDs are turned on in sequence and the signal is read from the matching transistor. If signal is read from the matching transistor. If no signal is read, then that indicates a blocked no signal is read, then that indicates a blocked IR beam, meaning a touch. IR beam, meaning a touch.


Highest quality of Highest quality of underlying image underlying image

Very high Very high transmittance transmittance

Very high durability Very high durability and reliabilityand reliability


Lower resolution than Lower resolution than other technologies other technologies

Surface obstructions Surface obstructions can cause a false touch can cause a false touch

DISPERSIVE SIGNAL DISPERSIVE SIGNAL TECHNOLOGYTECHNOLOGY

This is the recent most technology, introduced in 2002.

It uses sensors to detect the mechanical (vibrational)energy in the glass that occur due to a touch.

Complex algorithms then interpret this information and provide the actual location of the touch.

APPLICATIONSAPPLICATIONS Public Information Displays tourism displays, trade show displays

Customer Self-Service stores, restaurants, transportation hubs, ATM and airline e-ticket terminals.

And many more uses... computerized gaming, student registration systems, multimedia software, financial and scientific applications, and more.

CONCLUSIONCONCLUSION

Touchscreens, touch panels or touchscreen Touchscreens, touch panels or touchscreen panels are display overlays which have the panels are display overlays which have the ability to display and receive information on ability to display and receive information on the same screen.the same screen.

Touchscreens also have assisted in recent Touchscreens also have assisted in recent changes in the PDAs, making these devices changes in the PDAs, making these devices more usable.more usable.