Monday, November 01, 2010

Technology Behind Touch Screens in Mobile Phones

Touch screen mobile phone seem to be a hot topic nowadays.Touch screen mobile phone will make you do not feel like clumsy just like you press the bottom on a normal phone. So, you can see that touch-screen phone is not only in good looks, but also they are easy to operate. Every day one company or the other is coming out with a new technology that they integrate into their handsets. Mobile phones are way more compact and uber cool. They now come with a plethora of features in them which make them a lot more than just phones.

Nowadays, with a mobile phone apart from making calls you can listen to music, watch movies, take photos etc. But off late, it seems to be that the key-based generation of mobile phones is losing their charm and touch screens are slowly crawling in. Touch screen phones come with rather screen sizes and are getting more user friendly as well. However, touch screens have their own pros and cons and for that we need to know the different type of touch screen display that these phones have. Different touch screens you ask?? Yes! There are basically three types of touch screen displays that are being used in mobile phones these days. So here’s a brief look at them. 

Resistive Touch screen:
Resistive touch screens are the most widely used displays used in touch screen mobile phones. These types of displays are cheap and are mostly resistant to water and dust, but are prone to getting scratched and cannot be used with sharp objects for fear of damage. Since the resisitive display is based on pressure touch, it cannot have a protective glass coating, and this is why such displays are delicate. You can however use any blunt object to touch it for it to respond, like for example a fingernail, stylus, etc. You however do need to apply a bit of pressure in order to press the touchscreen and they have a good lifespan of about 35 million clicks.

The screen is basically made of two layers and there is a layer of small plastic dots between the two layers. Electricity is constantly passed through each one of the layers and in the event of contact, a chain is formed. The amount of the electricity that is passing between the layers is then measured by the device, in order to determine the exact point of touch. The biggest drawback of these types of displays is that it they can’t recognize two simultaneous touches at the same moment. So if you are buying a touch screen phone and hoping for it to be a multi touch device, make sure it is mention on the box or ask the seller or better try to look for the specifications online. Or you may be stuck with a device that you weren’t looking to buy. In addition to this they are highly prone to being damaged and their sensitivity reduces when they gets scratched. Moreover they only allow 85% of the light emitted by the screen to be passed through.
Examples of Resistive touch Screen Phones: Samsung Corby, LG Cookie, Nokia 5800 XpressMusic, HTC Touch Pro 2.

Capacitive Touch screen:
Capacitive touch screen displays are basically of two types, one that can recognize multiple simultaneous touches and the other which can only recognize one point of touch at a time. The multi touch interface offers a more enjoyable UI and makes it more convenient to use the device. It requires little or no effort in order to make a gesture or press the virtual buttons and make the navigation much faster and more accurate. These types of touch screen displays are costlier than the resistive types however, they are much more resistant to scratches, moisture and dust. 

This type of touchscreen display employs just one layer which is known as the grid. It’s covered by an electro-conductive material which passes a continuous current through it at a certain frequency. When screen comes in contact with an object that is emitting a constant electric flow, for example a human finger (yes, the human body generates a certain amount of electricity), there is a change in the flow of the passing current contact point is determined.
These types of display are much more accurate, require no calibration and have an extremely long life of about 225 million clicks. In addition to this they also let through about 92% of the light emitted by the screen. There’s however one big disadvantage, they cannot be touched using just any object that you may like so in case you are not comfortable using your fingers you will have to purchase special capacitative pens in order to use the phone.
Examples of Capacitive touch screens phones: Apple iPhone, Sony Ericsson XPERIA, HTC Desire, Motorola Milestone.

Infrared Touch screen:
Infrared touch screens displays are the most expensive of the all the three types of displays mentioned in this article. They don’t require any physical force in order to operate, all that they need is a just a gentle touch. In addition to this advantage they are also not at all influenced by dust, moisture or scratches. Moreover they are also much higher in terms of durability when compared to the other ones. They are basically two types of infrared displays; optical and heat-sensitive.
The optical type of infrared display uses infrared beams, which are generated using LEDs and are not visible to the human eye. They work, using a number of sensors, which are arranged above and around the screen, forming a grid of invisible beams. If an object like a finger or a stylus touches the display, it interrupts the rays in a certain area and that helps determine the point of touch. It has an overall lifespan of about 7 years. The biggest disadvantage of this display is that a strong ambient light can reduce the productivity of this kind of a display.
The heat-sensitive type is more widely used type of infrared display, but it is rarely used in screens. It is mostly applied in other components of mobile devices like touch sensitive buttons. Some of the best examples of which are Samsung SGH-E900 and Samsung U600, which are only sensitive to warm touches. So in cold climates if your finger is at a lower temperature than the device and you touch this phone it won’t respond to your finger as its cold.

Tactile Touch Screens:
University of Glasgow researchers determined that people type more accurately on a touch screen when the phone vibrates to indicate that a button has been pressed correctly. The researchers affixed a high-end actuator to the back of a PDA (top two images). The researchers are also developing applications for multiple actuators on the phone (bottom two images). Eventually, similar, smaller actuators could be used inside mobile devices.

While the touch-screen interface looks beautiful, it will most likely suffer from the same drawback that plagues many other mobile gadgets with touch screens: no tactile feedback. A button on a flat, slick display simply doesn't feel like a button, and as a result, people are prone to making errors with them.


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