touch screen technology report and ppt

[seminar surveyer]

---

BY
S.ABDUL KAREEM

[attachment=7751]

How Does a Touchscreen Work?  
A basic touchscreen has three main components:
1 Touch sensor;
2 Controller;
3 Software driver.
The touchscreen 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/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. Controllers are available that can connect to a Serial/COM port (PC) or to a USB port. Specialized controllers are also available that work with DVD players and other devices.
Software Driver
The driver allows the touchscreen 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. This allows the touchscreen to work with existing software and allows new applications to be developed without the need for touchscreen specific programming.
Touchscreen Technology
Resistive touchscreen
Capacitive touchscreen
Infrared touchscreen
Surface acoustic wave (SAW) touchscreen
Strain gauge touchscreen
Optical imaging touchscreen
Dispersive signal technology touchscreen
Resistive touchscreen
Structure
Resistive touch screens consist of a glass or acrylic panel that is coated with electrically conductive and resistive layers made with indium tin oxide (ITO) .The thin layers are separated by invisible spacers.

4-wire resistive touchscreen
5-wire resistive touchscreen
The construction of the panels are similar with 4-wire technology, but for a 5-wire touch screen all four bus bars are connected to the lower, non-flexible layer of the screen. The flexible layer is always used as a sense layer to read the voltage connection point to the bottom layer.

8-wire resistive touchscreen

Resistive touchscreen
Characters:
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

Projected-capacitive touchscreen
Structure
Projected capacitive touchscreens 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.
Projected-capacitive touchscreen
During a touch, capacitance forms between the finger and the sensor grid.The embedded serial controller in the touchscreen calculates touch location coordinates and transmits them to the computer for processing.
Surface-capacitive touchscreen
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 touchscreen
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. The controller precisely calculates the proportion of the current passed through the four electrodes and figures out the X/Y coordinate of a touch point.

Capacitive touchscreen
Characters:
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 touchscreen
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 (LEDs) 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. One or more photo transistors from each axis detect the absence of light and transmit signals that identifies the x and y coordinates.
Infrared touchscreen
Infrared touchscreen
Characters:
Clear as glass, improves reading ability
Most durable surface

SAW touchscreen
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.
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 calculate.

SAW touchscreen
SAW touchscreen
Characters:
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

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
……