Touch screen computers have different types of touch screens, including mutual capacitance, self-capacitive, surface-capable, and resistive technology. They can detect fingers, nails, styluses, and other conductive objects. Some also use sound and light waves to locate touch movements. They are used in various devices such as tablets, cell phones, ATMs, and information kiosks.
A touch screen computer typically has one of several types of touch screens as the primary input device. Some touch screen systems also include a keyboard and mouse, while others don’t. A touch screen monitor can usually detect the presence and location of a finger, nail, or special stylus. Tablets, cell phones, and video games often use a touch screen computer monitor for input. Personal digital assistants (PDAs), bank ATMs and information kiosks can also use touch screens.
A mutual capacitance screen is sometimes used in a touch screen computer tablet. This type of screen can detect multiple touches simultaneously, allowing for more complex inputs. A grid of capacitive sensors etched behind a protected glass screen can detect the presence of fingers near any row-column intersection. It can also detect other conductive objects, such as a specially designed stylus or the palm of a hand. Its multi-touch capability makes it suitable for drawing applications such as handwriting input or Asian characters.
Two other types of capacitive displays are also used as touch screen computer monitors. A self-capacitive screen measures the current induced by the presence of a finger near its grid. Like a mutual capacitance shield, it can also detect other conductive objects, but can only detect one at a time. A surface-capable screen has a lower resolution and can also only detect one object at a time. Its glass screen has a solid conductive coating on the back that can be used to approximate the location of a touch.
Resistive technology is also often used in some types of touch screen computer monitors. When a finger, nail, or stylus presses down on a resistive screen, the flexible metal layers of the display touch at that point. Circuits that measure current flowing across the screen can determine this location. Like most other types of touch screens, it can only detect one touch at a time. Its physical nature requires pressure to register a touch and makes it more susceptible to damage than other types of touch screens.
Sound and light waves are also used to detect and locate the touch movements of some screens. An acoustic display transmits ultrasonic sound waves across the screen and measures the response. A finger or other object pointed close to the screen absorbs some of the sound waves, revealing its location to the control loop. Interrupted light waves can also be used for this purpose. In these displays, a grid of light-emitting diodes (LEDs) and corresponding photodetectors monitor the screen area.
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