Touch Screen Technology
Touch screen provides a direct, interactive gesture based communication technology. A Touch screen is an electronic based optic display, able to detect and locate the touch around the display area. This technology allows a direct interaction with the display screen by a simple touch instead of the ordinary mouse, joystick or touchpads. The touch screen enables direct manipulation. Direct manipulation means, a user can directly or physically interact with the operating systems of digital systems like computer display or mobile phones, instead of typing command by command. Thus touch screen provides a very simple way to move files or folders on the screen, scroll the menus, make them zoom and lots more with a simple’ touch’ on the display area. Touch screen is sensitive to the touch of a finger, pointed finger nail, hand or some pointed device.Touch screen play a prominent role in tablet computers, smart phones, personal computers and game consoles. The popularity of such devices is driving the acceptance and demand of touch screen for functional and portable electronics fields.Currently there are many different touch screen technologies are available like capacitive, resistive, Surface Acoustic Wave etc. These all types of touch screens actually work in the same manner, even though the technologies are different from each other.
Brief overviews of different touch screen technologies are given below.
Resistive touch screen Technology:
The resistive touch screen resides of mainly two layers - a flexible top layer and a rigid bottom layer. The flexible upper layer is made with Polyethylene and the second or bottom layer is with glass. A conductive coating made up of Indium Tin Oxide (ITO) is provided for both the layers and also spacers are used for spacing. As long as the monitor is functional, an electric current flow occurs across the screen’s two layers. When a touch is made on the screen surface, the flexible layer push down and touches the glass (bottom) layer. Due to this, a variation in the electric field is detected. The coordinates of touching point is evaluated by controller section. When the coordinates are analyzed, the corresponding driver interprets the touch in to readable indications for the operating system to understand and react accordingly.
The Resistive Touchscreen transmits only 75% of light from the display monitor. The resistive touch screen further more split in to 4 wired, 5 wired, 6 wired, 7 wired and 8 wired resistive touch screen. The design and construction of all the types of resistive touch screen technologies are similar, but the method of determining the co-ordinates of touch is different from each other.
1. Four-wire Resistive Touch screen:
The four wire resistive touch screen technology is the simplest one regarding the others. In this four wire resistive touch screen, both the upper and lower layers are used to determine the axes locations (X and Y coordinate) of the touch. By developing a voltage gradient on the flexible layer, we can easily determine the X coordinate point of the touch. Similarly the Y coordinate point can be evaluated by developing a voltage gradient on the second layer.
2. Five-wire Resistive Touch screen:
For calculating the touch coordinates in the five wire resistive touch screen, it uses only the stable glass layer instead of the flexible upper layer. The lower glass layer is equipped with all the touch position sensing capabilities. In this five-wire resistive touch screen design system, one wire proceeded to the flexible layer and the other four wires are expanded to the four of the bottom or the second layer. The flexible layer operates as a voltage calibrating probe.
3. The Six and Seven wire resistive touch screen:
To improve the overall performance of the six-wire resistive touch screen technology, an additional ground layer is included behind the glass layer. But in the seven-wire resistive touch screen technology, there are two sense lines provided on the bottom layer.
4. Eight-wire Resistive Touch screen:
The Eight-wire Resistive Touchscreen is an alternative for four-wire Resistive Touch screen with an addition of four sensing points. These four sensing points are used to decrease the drift created by the changes in the environment and also to provide stabilization to the system. These Eight-wire Resistive Touchscreen systems employed in 10.4” sizes or larger sizes according to the significance of the drift.
Fig: Layers of Resistive Touch Screen and Resistive touch screen panel
Advantages of resistive touch screen technology:
- Resistive touch screen provides typically high resolution around 4096 x 4096 DPI.
- Resistive touch screen provides accurate touch controls.
- In Resistive touch screen, contact is made with fingers, any other pointed devices such as stylus or gloved fingers.
- The Resistive touch screen technology can be made to support multi touch inputs.
- Resistive touch screen technology offers relatively low cost.
- Resistive touch screen provides high resistance to water and dust.
- For handwriting recognition, Resistive touch screen is the best suited technology.
Disadvantages of Resistive Touchscreen technology:
- In Resistive Touchscreen, the finger touching required little pressure since the Resistive Touchscreen is not too sensitive.
- Relatively the Resistive Touchscreen may be more prone to damage.
- The Resistive Touchscreen transmits only 75% of light from the display monitor
- Resistive touch screen can be easily damaged by poking, scratching and by any impact.
- A periodic recalibration is required for the resistive touch screens.
Popular Brands of Resistive Touchscreen Technology:
- The popular devices like, Nintendo DS, HTC Touch Pro2, Nokia N97, Sony Ericsson Satio, HTC Tattoo, Samsung Champ Duos, Spice Mi-270 , Nokia C2-02 etc. are commonly use the Resistive Touchscreen technology.
- Resistive Touchscreen is commonly used in hospitals, restaurants and factories due to their high resistance to fluids and pollutant.
Capacitive touch screen technology:
The capacitive touch screen made up of an insulator like glass. In Capacitive touch screen, the glass is coated or covered with a transparent conductive material like Indium Tin Oxide. Since human body has the ability to conduct electricity, a simple touch in to the capacitive touch screen results in the malformation of the screen surface’s electrostatic field, which may be quantifiable as a variation in capacitance. In Capacitive touch screen, Varieties of techniques are employed for determining the touch locations on the screen. Then the controller processes these touch locations.
Advantages of Capacitive touch screen technology:
- Multi touch can be implemented in this capacitive touchscreen.
- Capacitive touch screen technology is moderately durable.
- Capacitive touch screen technology provides high resistance to scratches and impacts.
- Capacitive touch screens are easy to clean.
- Faster typing speeds can be achieved using this capacitive touch screen technology.
- The capacitive touch screen transmits about 90% of light from the display monitor.
- Capacitive touch screen is responsive than the other resistive touch.
- In capacitive touch screen, we can easily touch the screen without much pressure
Disadvantages of Capacitive touch screen technology:
- Capacitive touch screen are less accurate than the others.
- The capacitive touch screen does not respond to any other objects instead of human finger or skin. So we can’t work with a gloved hand or a stylus
- Capacitive touch screen are more expensive than others.
- Capasitive touch screen can be easily used without any pointed objects.
Popular Brands that use capacitive touch screen technology:
- 3M Micro touch screens.
- Capacitive touch screens are used in Samsung, LG and other famous brand smartphones
- Capacitive touch screen used in Apple Smartphones
- Samsung's Super AMOLED screens.
- Windows-based phones also use capacitive touch screen technology.
Surface acoustic waves touch screen technology:
The surface acoustic wave touch screen uses acoustic waves such as sound waves and also ultrasonic waves, which can be passed over the touch display panel. There are two transducers- a transmitting and the other one is the receiving, is used in the Surface acoustic wave touch screen technology. These two transducers are placed along the X and Y axis of the touch monitor’s glass plate layer. Some reflectors are also placed along with these glass plates. The acoustic or the ultrasonic waves spread across the glass plate and bouncing off by the sensors. When we make a touch on the screen, since the waves pass over the screen, a small part of the wave gets absorbed. So there is a change in the wave’s transmission occurred over the touch panel surface. This change in the waves due to the touch can be identified and send it to the controller for the evaluation and processing of the touch position on the screen. The surface acoustic wave touch screen can be easily damaged by the contaminants and other outside elements.
Advantages of Surface Acoustic Wave (SAW) Touchscreen technology:
- Surface Acoustic Wave Touchscreen has excellent ability to withstand pressure, wear or damage.
- The Surface Acoustic Wave Touchscreen technology can provide a response to the Z coordinate axis.
- The Surface Acoustic Wave Touchscreen offers a stable drift free performance.
- The Surface Acoustic Wave Touchscreen offers excellent image transparency.
- Surface Acoustic Wave Touchscreen provides high resolution
- Surface Acoustic Wave Touchscreen enables maximum light transmission over the touch screen.
- Surface Acoustic Wave Touchscreen provides high optical clarity and also high transmission rates.
- A periodic calibration should need for the Surface Acoustic Wave Touchscreen.
Disadvantages of Surface Acoustic Wave Touchscreen technology:
- Surface Acoustic Wave Touchscreen can’t be supported with the NEMA environments.
- Since the Surface Acoustic Wave Touchscreen uses the glass overlay, there is more chance for the breaking of glass overlay.
- Surface Acoustic Wave Touchscreen cannot perform in wash-down situations.
- Surface Acoustic Wave Touchscreen is expensive compared to the other touch screen.
- Surface Acoustic Wave Touchscreen is easily affected by dust, water and dirt in the environment.
Popular Brands that use Surface Acoustic Wave Touchscreen technology:
- Surface Acoustic Wave Touchscreen can be used in Amusement Parks, ATMs, banking sectors, Industrial Control Rooms, KIOSK and Gaming Environments.
Infrared Touchscreen Technology:
In the infrared touch screen, there uses an array of X and Y axes equipped with infrared LEDs and pair of photo detectors, around the border of the touch screen. The infrared LED beams used in the infrared touch screen intersect one another in horizontal and vertical patterns. When there is a touch occurred in the infrared touch screen, this disrupts the LED beam patterns and this disruption in the beam pattern will help the sensors to identify the exact touching location.
Advantages of infrared touch screen technology:
- In infrared touch screen 100% light transmission occurred over the touch screen.
- Infrared touch screen is more accurate than other touch screen.
- Infrared touch screen can be touched with any objects having width greater than 4mm.
- Infrared touch screen is resistant to water, dust etc.
- Infrared touch screen provides a scratch proof touch screen.
- Infrared touch screen guarantees long life durability.
- Infrared touch screen can be easily installed and operated.
- Infrared touch screen is available in different customized sizes along with slandered size.
Disadvantages of Infrared Touch screen technology:
- Infrared Touch screen offers decreased touch resolution.
- There is no protection layer included, for the display surface.
- Infrared Touch screen technology is expensive than other touch screens.
Popular Brands that use Infrared Touch screen Technology:
- Infrared Touch screen can be used in Ticketing machines, Medical instrumentation.
- Infrared Touch screen can be used in Commercial transportation, ATMs.
- Infrared Touch screen can be used in large plasma displays, Classroom whiteboard, Public venue directory, Traffic management etc.
Multi touch screen technology:
The multi touch screen detects the multi touches made on the screen surface area over the same time. The multi touch screens requires some of the common customary functionalities like zooming out, zooming in, virtual keyboard, rotating objects etc. for interfacing purposes. Multi touch permits more than two fingers to be used at same time over the same screen surface. Multi touch can be now used in many applications like smart phones, restaurants and for business application levels etc. The multi touch allows us to use multi- finger gestures to carry out things like pinching on the screen for zoom in etc.
Applications of Multi touch screen technology:
- Multi touch can be used in smart phones like Samsung Galaxy, Nokia N8, Apple iPad, iPhone, Microsoft Touch table, Nexus S and many more.
In many movies and TV shows we might have noticed that a group of persons watching videos, data or images on a big transparent touch screens on tables or on a wall. These types of technologies that we see in the movies are implemented by some researchers in Korea. Korea Advanced Institute of Science and Technology (KAIST) research team have taken this technology concept and build a new ‘TransWall’ – transparent touch screen, which is not only transparent but also can receive the input data and is able to display the data or contents on each of the two sides of its screen display and also it provides haptic feedback to the end user.
The researchers developed a T-shape frame work with two upward mounted projectors, which is able to project data and visuals on the two sides of the display or screen. The transparent screen is built with a clear holographic film ingrained between two plexi-glass sheets. Those sheets are bordered with 2 rectangular infra-red touch sensor frames. The surface transducer is bind with plexi-glass above the frames, and attached with microphones. The frame on each side will detect the user finger touch location and movement on the plexi-glass screen. These collected data from the transwall is transmitted to a computer, which alters the images that will be projected on the holographic film. Thus the user can select objects, flip pages, draw lines and can perform all the usual touch screen activities. The users on both sides are able to view the contents on either side at the same time. There is a transducer, which causes the touch screen to vibrate according to the commands so that a user can feel that he is using just touching fingers on a large screen and accessing with ease like a touch screen mobile phone. The microphones used in this system helps the users to communicate with each other.
Applications of Transparent Display:
- LG displays, Samsung Smart window
- 3-D Desktops, games etc.Touch Scree