TOUCH SCREEN TECHNOLOGY

-B.Sucharitha (07H51A1208)

INTRODUCTION

A touch screen is an input device that allows users to operate a device by simply touching the display screen.

The display screen has a sensitive glass overlay placed on it and we can give the desired input by touching on it.

The term generally refers to touch or contact to the display of the device by a finger or hand.

HOW DOES A TOUCH SCREEN WORK…???

There are three basic systems that are used to recognize a person's touch:

• Resistive• Capacitive system • Surface Wave

(i)RESISTIVE

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

The sensor generally has an electric current or signal going through it and touching the screen causes a voltage or a signal change.

(ii) CAPACITIVE SYSTEM

This is a small device card that connects the sensor and the main hardware device.

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

(iii) SURFACE WAVE

It is the software that allows the touch screen and the device to work together.

It tells the main hardware device how to interpret the touch event information that is sent from the controller.

Most of the devices are a mouse-emulation type driver.

TOUCH SCREEN TECHNOLOGIES

Resistive touch screen Surface acoustic wave touch screen Capacitive touch screen Infrared touch screen Acoustic pulse technology 3M Dispersive Signal Technology (DST)

RESISTIVE TOUCH SCREEN

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

This causes a change in the electrical current, which is registered as a touch event and sent to the controller for processing.

SURFACE ACOUSTIC WAVE TOUCH SCREEN

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.

CAPACITIVE TOUCH SCREEN

A capacitive touch screen panel is one which consists of an insulator such as glass, coated with a transparent conductor such as Indium tin oxide (ITO).

As the human body is also a conductor, touching the surface of the screen results in a distortion of the screen's electrostatic field, measurable as a change in capacitance.

INFRARED TOUCH SCREEN

An infrared touch screen uses a ray 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.

ACOUSTIC PULSE RECOGNITION

This system uses piezoelectric transducers located at various positions around the screen to turn the mechanical energy of a touch (vibration) into an electronic signal.

The screen hardware then uses an algorithm to determine the location of the touch based on the transducer signals.

This touchscreen technology gives good durability and optical clarity.

It is usually able to function with scratches and dust on the screen with good accuracy.

The technology is also well suited to displays that are physically larger.

3M Dispersive Signal Technology (DST)

Traditional touch technologies detect touch locations by interrupting acoustic waves, optical fields or infrared light above the surface of the touch screen.

Dispersive Signal Technology (DST), however, precisely calculates touch locations within the glass substrate by analyzing the bending waves created by the user's touch.

This allows for fast, accurate and reliable touch performance that is unaffected by contaminants, scratches or static objects on the screen, as well as enabling stylus support and multi-user capability.

3M Dispersive Signal Technology (DST) is poised to become the touch technology standard for large-format interactive displays.

USAGE

Finger stress: With stressing the finger on the

desired area of the touch screen, the input is taken by the sensors of the screen.

Finger nail as stylus: With the help of touching the screen

with the finger mail which acts as the stylus, input can be taken by the sensors.

MULTI-TOUCH TECHNOLOGY On touchscreen displays, multi-touch refers to

the ability to simultaneously register three or more distinct positions of input touches.

ADVANTAGES

User friendly Fast response Error free input User finger, finger nail, gloved hand,

stylus or any soft tip pointer to operate 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.

CONCLUSION

Though the touch screen technology contains some limitations with it, it is fast, accurate, user friendly and fun to operate .It is being widely accepted.

With some modifications, it can completely replace mouse and keyboard completely in the near future.