vineri, 13 aprilie 2012

What is a touch screen and how does it work?

Cell phones have come a long way since their inception, in the early 80’s. Back then, cell phones were as large as 2 bricks put together and could only work for a couple of minutes, as the batteries were very weak- although very large. Today, cell phones are the size of a credit card- and not much thicker, and can do stuff that usually is achievable on a computer. You can browse the web, download files, check your emails, view entire movies and listen to full length albums, all in one, long battery charge. But maybe the most appealing aspect of new cell phones is that the keyboard is now tactile, as the screen is touch sensitive. Most new phones don’t even have physical keyboards anymore, as everything can be done via the screen. Basically, the front of the cell phone is one big piece of glass which reacts to each touch you make on it. What most people don’t know is that there are more types of screens out there and the fact that the type of screen can influence both the price and the performance of the device. Next, let’s take a look at the three major types of touch screens and see each one’s advantages and disadvantages.

Resistive touch screens- this type of screen is the most basic type of touch sensitive out there and is, normally, the cheapest one. The principle behind it is quite complicated, but can be put into simpler words as well. On the top of the screen, there’s a layer of material that’s divided into many, many layers, similar to squares. This special material inside the layers is very sensitive and, when it’s touched, it sends a signal to a chip that calculates the position of the place where the action occurred. Resistive screens are not very precise all the time, as the chip can interpret incorrectly the action and can “understand” that you want to push the button next to it, for example. That’s why is better sometimes not to use the finger- which is quite big, but a stylus instead, which will be much more precise. Another disadvantage is that the screen has poor visibility outdoors.

Capacitive touch screens- this is the “natural evolution” of the resistive touch screen. The current is sent throughout the screen at all times, from corner to corner- left top corner to right bottom corner and right top corner to left bottom corner. Whenever you touch the screen, a certain deviation is calculated and thus localizing the area of the screen you touched. The capacitive touch screen is much more precise and has much better visibility in broad day light. Also, unlike resistive touch screens, capacitive ones can support multi touch gestures, which are very useful and fun to use while browsing web pages. Of course, capacitive displays are more expensive.

Infrared screens- this type of screen can be either heat sensitive or optical. Heat sensitive displays can calculate the point of impact if they’re touched by warm objects- that are the finger. Optical versions have an invisible grid above the display and the point of impact is calculated by finding the place where the grid is disrupted. This type of screen is the most expensive one, but it’s very precise and offers very good visibility outdoor, although extreme light and heat can disrupt performance.  

telefoane de vanzare, vand telefon

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