Information Technology Reference
In-Depth Information
and it scales to large surfaces. So it can be used on arbitrary flat surfaces, such as
tables, augmented walls or whiteboards. However, the position of the pen is tracked
in relation to the external device and not in relation to the paper sheet. Moreover,
this approach is not able to detect which sheet the user is writing on. This makes this
approach hard to use in settings where users do not write on one single page but deal
with many pages. Ultrasonic tracking is utilized in commercial solutions that target
private end-users, for example the Pegasus Tablet NoteTaker
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. It has a resolution of
100 dpi.
Digitizing Tablets
Digitizing tablets are devices that capture pen input for computer applications. The
most common technology is patented by Wacom. A Wacom device has a flat surface
and generates a magnetic field. Using induction, the position of a specific stylus can
be detected on this surface. Figure 2.5 shows a Wacom Intuos4 graphics tablet
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.In
principle, digitizing tablets do not aim at supporting the use of a pen on paper. In-
stead, the tablet is used to directly interact with the digital system, e.g. for drawing
in a graphics application or for positioning the mouse pointer. However, the induc-
tion principle still works if one or several sheets of paper are positioned between the
graphics tablet and the stylus. For this reason, they can be used to track pen input on
real paper. This approach enables very high resolutions (about 1000 to 5000 dpi).
However, when used for capturing pen input on paper, it has the same drawbacks
as ultrasonic tracking. The user must manually calibrate the paper sheet and must
indicate page changes. Moreover, the interaction is restricted to the small surface of
the tablet. Therefore this approach is typically used only in research prototypes (e.g.
[88, 27, 150]).
Inductive Pens
The following techniques do not detect the position of the pen with respect to an
external reading device, but they encode positional information directly on paper.
Thereby local page coordinates can be detected without requiring the system to have
knowledge about the absolute position of the sheet of paper. It is the digital pen that
decodes its position, which makes external devices and calibration obsolete. As the
position which is encoded on the physical sheets can also contain a page identifier,
the pen is able to detect on which page it is used. Hence, it is not necessary to
manually indicate on which page the pen is currently used. Users can therefore
work very naturally with multiple sheets of paper.
Within the frame of the European Paper++ project, researchers have developed
an approach that leverages conductive ink [134, p. 26]. Positional information is
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http://www.pegatech.com
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http://www.wacom.com
