Information Technology Reference
Figure 7: The electronic pen.
A trackball is a small ball that is fixed to a support and can be moved
along any direction. A mouse uses a similar principle but the ball allows it to
be moved on a flat surface. The electronic pen (Figure 7) is used to digitize
whatever the user draws. It is coupled with a tablet: when the pen is passed
on the tablet its trace is recorded and digitized as an image. The main
drawback associated with this device is writing recognition that has to be
performed using dedicated software [11,13].
The touch screen is a pressure sensible screen without movable parts. It
can be used by unskilled people too and has the advantage that keyboards can
be simulated inside the screen thus reducing the working space .
The eye-tracker uses infrared sensors to acquire eye movements. The
users can control the pointer on the screen simply by fixating their gaze on it.
Nowadays this device has low accuracy.
Cameras are a very effective interaction system because video streams can be
processed nearly in real time to extract implicit inputs . A UC framework
should be equipped with one or more cameras with dedicated computing
resources to increase the rate of processed images per second [10,11].
4.1.4 Audio input devices
Audio data need very less storage space than video. Microphones are present
in all the vocal interfaces that are very useful for disabled people. Many
learning algorithms have been already developed for real-time command
interpretation. All of them need a training phase to recognize the user's voice.