The invention provides for an optical imaging pen configured to capture
and decode infrared (IR) position tags from a page. The pen includes a
force sensor photodiode configured to sense when a nib of the pen is in
contact with the page, and an LED configured to project IR radiation onto
a portion of the page when the nib is in contact therewith. The pen also
includes an image sensor configured to image the portion of the page when
the nib is in contact therewith by receiving reflected IR radiation, and
at least one orthogonal accelerometer configured to sense motion of the
pen by sensing acceleration in x and y directions and integrating with
respect to time to produce an instantaneous velocity. The pen further
includes a controller arranged in signal communication with the
accelerometer, photodiode and image sensor, said controller configured to
control the photodiode and image sensor to capture, decode and encrypt
the tags into digital ink data, and to include the instantaneous velocity
of the pen into the digital ink data.