Information Technology Reference
In-Depth Information
Data-embedding Pens
A recent direction of research examines data-embedding pens [81]. In addition to
leaving visible ink traces, a data-embedding pen visually encodes digital data onto
the paper document. Liwicki et al. present a prototype device that features, in ad-
dition to an ordinary ink refill, a tiny ink-jet head. This ink-jet head can print a
sequence of dots in a bright color close to the handwritten traces. This dotted line
encodes a sequence of binary data, which can be subsequently decoded by using op-
tical image processing. A data-embedding pen can be used for instance for encoding
metadata of the handwriting, such as the time of writing, the ID of the author or the
geo-coordinates of the current location. Alternatively, the pen can encode the tem-
poral sequence in which the pen traces have been written. Such information about
the writing process can improve recognition of scanned handwriting.
2.1.5 Digital Output on Paper
We have discussed a variety of approaches that allow systems to capture paper con-
tents and input made on paper. To conclude the section on technologies, we will
briefly discuss how systems can provide
output
directly on paper. While a straight-
forward way consists of (re-)printing a document, this is not very interactive, since
each update requires a new printout. We will have a look at technologies that enable
more dynamic output on paper.
Projection
The projection approach uses paper as a passive display onto which digital contents
are projected. The position and orientation of the paper surface is tracked in real-
time. The system then projects the display contents onto this surface. This enables
not only to simulate screens, but also to overlay physical objects with additional
digital information. If the performance of the tracking system is sufficently high
and the projected image is correctly adjusted to fit the physical surface, the paper
surface can be moved around freely and behaves similar as if it was an active display.
However, even in state-of-the-art solutions, the projected image is slightly lagging
behind the paper surface if the surface is moved quickly.
This approach is relatively straightforward if paper is used only on a flat sur-
face. With the influential Augmented Surfaces system [123], Rekimoto and Saitoh
demonstrated that a single camera and a standard projector are sufficient for tracking
paper on a 2d surface. If the user is allowed to freely move and rotate paper surfaces
in three dimensions, things get more complicated. In this case, the surface is not
necessarily perpendicular to the orientation of the projector. So the projected image
has to be distorted such that the projected image appears undistorted to an observer.
Early examples are Dynamic Shader Lamps [7] and PaperWindows [40]. Most so-
