TOUCHSCREEN TECHNOLOGY

NAVEEN CHAND ANSHUMANECE 4TH YEAR0703031057

INTRODUCTION TO THE TECHNOLOGY TOUCHSCREEN TECHNOLOGIES WORKING PROS & CONS APPLICATIONS

CONTENTS TO BE EXPLAINED...

A touch screen is an input device that allows users to operate a PC by simply touching the display screen.The display screen has a sensitive glass overlay placed on it and we could give the desired input by touching it. A touch screen is based on CRT (Cathode Ray Tube) technology, that accepts direct onscreen input. The ability for direct onscreen input is facilitated by an external (light pen) or an internal device (touch overlay and controller) .

INTRODUCING THE TECHNOLOGY

Working of Touch screen is a result of coordination of the following main components used in it.

Main touch screen componentsMain touch screen components:: Touch sensor Controller Software Drivers

WORKING OF TOUCHSCREEN

A touch screen sensor is a clear glass panel with a touch responsive surface which is placed over a display screen so that the responsive area of the panel covers the viewable area of the display 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

TOUCH SENSOR

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.

CONTROLLERS

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

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

SOFTWARE DRIVER

This allows the touch screen to work with existing software and allows new applications to be developed without the need for touch screen specific programming.

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

Continue…

Resistive Surface acoustic wave Capacitive Infrared Optical imaging Dispersive signal technology Acoustic pulse recognition

TECHNOLOGIES

Resistive touch screen monitor is composed of a flexible top layer and a rigid bottom layer separated by insulating dots, attached to a touch screen controller.The inside surface of each of the two layers is coated with a transparent metal oxide coating Pressing the flexible top sheet creates electrical contact between the resistive layers, producing a switch closing in the circuit.The controller gets the alternating voltages between the two layers and converts them into the digital X and Y coordinates of the activated area

RESISTIVE

WORKING OF RESISTIVE 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.

SURFACE ACOUSTIC WAVE

When you touch the screen, you absorb a portion of the wave traveling across it. The received signal is then compared to the stored digital map, the change recognized, and a coordinate calculated. . The digitized coordinates are transmitted to the computer for processing.

WORKING OF SAW TOUCH CREEN

A capacitive touch screen panel is coated with a material, typically indium tin oxide that conducts a continuous electrical current across the sensor. The sensor therefore exhibits a precisely controlled field of stored electrons in both the horizontal and vertical axes - it achieves capacitance. When the sensor's 'normal' capacitance field (its reference state) is altered by another capacitance field, i.e., someone's finger, electronic circuits located at each corner of the panel measure the resultant 'distortion' in the sine wave characteristics of the reference field and send the information about the event to the controller for mathematical processing... The Apple iPhone is an example of a product that uses capacitance touch screen technology.

CAPACITIVE

When the sensor's 'normal' capacitance field (its reference state) is altered by another capacitance field, i.e., someone's finger, electronic circuits located at each corner of the panel measure the resultant 'distortion' in the sine wave characteristics of the reference field and send the information about the event to the controller for mathematical processing... The Apple iPhone is an example of a product that uses capacitance touch screen technology.

WORKING OF CAPACITIVE TOUCH SCREEN

An infrared (IR) touch screen panel employs one of two very different methods. One method uses thermal induced changes of the surface resistance. This method is sometimes slow and requires warm hands. Another method is an array of vertical and horizontal IR sensors that detect the interruption of a modulated light beam near the surface of the screen. IR touch screens have the most durable surfaces and are used in many military applications that require a touch panel display.

INFRARED

A relatively-modern development in touch screen technology, two or more image sensors are placed around the edges (mostly the corners) of the screen. Infrared backlights are placed in the camera's field of view on the other sides of the screen. A touch shows up as a shadow and each pair of cameras can then be triangulated to locate the touch. This technology is growing in popularity, due to its scalability, versatility, and affordability, especially for larger units.

OPTICAL IMAGING

This system uses more than two piezoelectric transducers located at some positions of the screen to turn the mechanical energy of a touch (vibration) into an electronic signal. This signal is then converted into an audio file, and then compared to preexisting audio profile for every position on the screen. This system works without a grid of wires running through the screen, the touchscreen itself is actually pure glass, giving it the optics and durability of the glass out of which it is made.

ACOUSTIC PULSE RECOGNITION

PROS & CONS

Direct pointing to the objects. Fast Finger or pen is usable (No cable required) No keyboard necessary Suited to: novices, application for information retrieval etc

Low precision by using finger User has to sit or stand closer to the screen The screen may be covered more by using hand No direct activation to the selected function

Information system Device controls Customer Self-Services Public information system

APPLICATIONS

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