04-11-2016, 02:08 PM
1464548562-Touchscreentechnology.pptx (Size: 599.74 KB / Downloads: 4)
What is Touch Screen ?
It is input device normally layered on electronics visual display of an information processing system.
User give i/p or control system through simple touch with fingers.
It is the most user friendly input device used to interface with a PC.
History and Development
In 1971 Dr. Sam Hurst, founder of Elographics developed the first touch opaque sensor “Elograph” at the University of Kentucky.
In 1974 He developed the first real touch screen.
In 1977, Elographics ( an organisation) developed a curved glass sensor called the touch screen.
How does a Touch screen Work?
Main touch screen components:
Touch sensor
Controller
Software driver
Touch sensor:
A touch screen sensor is a clear glass panel with a touch responsive surface which is placed over a 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
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.
Name of some IC controllar used in PC card are AR1000 Series, TSC2003, TSC2014,
Software Driver:
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.
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.
Touch Screen Technologies are:
Resistive
Capacitive
Surface Acoustic Wave (SAW)
1. Resistive Touch Screens:
Panel is composed of several layers. Two are thin, electrically conductive separated by narrow gap by insulating balls.
When press down on a point then that two layers connected at that point and panels behaves as voltage dividers.
Cause a change in electrical current which is registered as a touch events and sent to controller for processing.
Advantages of Resistive
High Resolution and Accuracy .
Fast Response .
Pressure-activated by finger with a very light touch .
Disadvantages of Resistive
Only 75 % Clarity .
Resistive layers can be damaged by a sharp object.
2. Capacitive Touch screen
Consists of an insulator such as glass, coated with a transparent conductor such as indium tin oxide (ITO).[2][3]
In capacitive system, a layer that stores electrical charge is placed on the glass panel of the monitor. When a user touches the monitor with his or her finger, some of the charge is transferred to the user, so the charge on the capacitive layer decreases.
Transmits almost 90 percent of the light
from the monitor and gives much clearer
picture than the resistive system.
3. Surface Acoustic Wave Technology
It based upon emission and absorption of sound waves.
It uses ultrasonic waves that pass over the screen panel.
Made of a glass overlay with a transducers for both the X and Y axes. Function of tranducers are transmitting & receiving the ultrasonic wave.
When screen panel touched portion of wave is absorbed.
This changes in wave registered the position of touch event & send informationto controller for processing.
Advantages of Surface Acoustic Wave
Excellent Image Clarity
Excellent Durability
High Resolution
Fast Touch Response
Disadvantages of Surface Acoustic Wave
Must be touched by finger, gloved hand, or soft-tip stylus. Something hard like a pen won't work
It can be affected by large amounts of grease, water, or dirt on the touchscreen