touch screen sensor
DESCRIPTION
touch scereen sensorTRANSCRIPT
TECHNICAL SEMINAR
Presented By:V Rakesh kumar
06R51A0558MURTHY INSTITUTE OF
TECHNOLOGY
Touch Screen Sensor
What is a Touch screen?
TOUCH SCREENS A touch screen is a computer display screen that is
sensitive to human touch, allowing a user to interact with the computer by touching pictures or words on the screen.
How Does a Touch screen work? A basic touch screen has three main components: Touch sensor; Controller; Software driver.
The touch screen is an input device, so it needs to be combined with a display and a PC or other device to make a complete touch input system.
Touch Sensor
A touch screen sensor is a clear glass panel with a touch responsive surface. The touch sensor or panel is placed over a display screen so that the responsive area of the panel covers the viewable area of the video screen.
There are several different touch sensor technologies on the market today, each using a different method to detect touch input.
The sensor generally has an electrical current or signal going through it and touching the screen can cause a voltage or signal change. This change is used to determine the location of the touch to the screen.
Controller
The controller connects between the touch sensor and the PC. It takes information from the touch sensor and translates it into information that PC can understand.
The controller determines what type of interface/connection you will need on the PC.
Software Driver
The driver allows the touch screen and computer to work together. It tells the computer's 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 as same as clicking your mouse at the same location on the screen.
Touch Screen Technology Resistive touch screen Capacitive touch screen Infrared touch screen Surface acoustic wave (SAW) touch screen Strain gauge touch screen Optical imaging touch screen Dispersive signal technology touch screen
Resistive touch screen
Structure
Resistive touch screens consist of a glass panel that is coated with electrically conductive and resistive layers made with indium tin oxide (ITO) .The thin layers are separated by invisible spacers.
Types of resistive touch screens
4-wire resistive touch screens 5-wire resistive touch screens 8-wire resistive touch screens
Characteristics
Cost effective solutions Activated by a stylus, a finger or gloved hand Not affected by dirt, dust, water, or light 75%~85% clarify resistive layers can be damaged by a very sharp
object
Capacitive touch screen
Two types Projected-capacitive touch screen Surface -capacitive touch screen
Projected-capacitive touch screen
Projected capacitive touch screens have front and back protective glassproviding optical and strength enhancement options.
Its middle layer consists of a laminated sensor grid of micro-fine wires, andoptical enhancement options.
Structure
Surface -capacitive touch screen
Structure
Surface capacitive technology consists of a uniform conductive coating on a glass panel. Electrodes around the panel’s edge evenly distribute a low voltage across the conductive layer, creating a uniform electric field.
Surface-capacitive touch screen
Working principle
A human body is an electric conductor, so when you touch 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. Theoretically, the amount of current that drifts through the four electrodes should be proportional to the distance from the touch point to the four corners.
Characteristics:
Durable and resistant to scratches for demanding applications
Faster and more responsive Immune to surface contaminants Superior optical clarity, brighter display and less
surface reflection Must be touched by finger, will not work with
any non-conductive input
Infrared touch screen
Infrared (IR) technology relies on the interruption of an IR light grid in front of the display screen. The touch frame contains a row of IR-light emitting diode (LED) and photo transistors, each mounted on two opposite sides to create a grid of invisible infrared light.
The IR controller sequentially pulses the LEDs to create a grid of IR light beams. When a stylus, such as a finger, enters the grid, it obstructs the beams.
Infrared touch screen
Characteristics:
Clear as glass, improves reading ability Most durable surface
SAW touch screen
Principle: Surface waves are readily absorbed when a soft
object such as a fingertip touches the substrate. SAW Touch Screen use pure glass with
transmitting and receiving piezoelectric transducers for both the X and Y axes.
The touch screen controller sends an electrical signal to the transmitting transducer, which converts the signal into ultrasonic waves within the glass.
SAW touch screen
Characteristics:
Durable glass construction High optical clarity Activated by a finger, gloved hand or soft tip Not completely sealable, can be affected by
large amounts of dirt, dust, and / or water in the environment
Technology Capacitive SAW Infrared Resistive
Transparence Very good >92%
Very good >92%
Very good >92%
75%~85%
Resolution Good Good Limited due tospacing of IRsensors
good
SurfaceContaminants/durability
Resistant tomoisture andother surfacecontaminants
Adversely affected bymoisture orSurfacecontaminants
Potential forFalse activationor dead zonesFrom SurfaceContaminants
Unaffected by Surfacecontaminants.Polyester topsheet is easilyscratched
Sensor substrate Glass with ITO coating
Glass with ITO coating
Any substrate Polyester top sheet, glasssubstrate withITO coating
Display size 8.4"-21" 10.4"-30" 10.4"-60" up to 19"
Touch method Human touch finger, gloved
hand or soft tip Can use any pointing device
Can use any pointing device
Multi-touch technology
Multi-touch denotes a set of interaction techniques which allow computer users to control graphical applications with several fingers.
Products: Apple IPhone, iPod touch, MacBook Air, and
MacBook Pro Microsoft Surface ……