Information Technology Reference
In-Depth Information
Fig. 2.5
Wacom Intuos 4 digitizing tablet (photo copyright Wacom)
encoded directly on paper by printing a grid of linear barcodes with conductive ink
on paper documents. This ink is barely visible to the human eye. A digital pen mea-
sures the inductivity and decodes from the barcodes its two-dimensional position.
The resolution of this technique is not high enough to capture handwritings but it
allows for distinguishing larger hot-spot areas on a document.
Anoto Technology
Anoto digital pen and paper [4] is the currently most mature solution for capturing
pen input on paper. An Anoto digital pen behaves like an ordinary ballpoint pen and
leaves visible ink traces. Moreover, it has a built-in infrared camera and a processing
unit to detect a specific pattern on the print products. By analyzing this pattern, the
pen can decode its position and electronically capture all pen traces made. This
is done at a frame rate of approximately 75 Hz and with a spatial resolution of
about 850 dpi. In addition to the position in the two-dimensional coordinate space,
current pens register pen tip force and timestamps. The technology further allows
for detecting the rotary and tilt angles of the pen although this is not supported by
the firmware of current pens. Anoto pens include a battery and can therefore be used
in mobile conditions. An Anoto pen is depicted in Fig. 1.2 on p. 12.
Depending on the capabilities of the pen, data is temporally buffered on the pen
until it is synchronized with a computer via USB or Bluetooth. Alternatively the data
is streamed in real-time to a nearby computing device using a Bluetooth connection.
