The trajectory obtained by the pen tip tracker and the filter is not suitable to perform handwriting recognition since most of the
recognition systems up to date assume that their input data is only formed by pen-down strokes. The system finds the position of the pen's ballpoint and checks for the presence of ink in this place. The ballpoint detector assumes that the pen tip is rougly conical in shape, in order to look for its projection onto the image plane. The following figure shows the points in which the boundaries of the pen tip were found using simple edge detection masks. The axis of the pen tip is located and the position of the ballpoint and the finger are found by using the image's brigthness profile along this axis.

The image's brigthness at and around the ballpoint position is measured in order to detect the presence of ink. Each point of the trajectory is later classified as pen up or pen down depending on this ink detection. In the page corresponding to results we show the performance of this algorithm working on several hadwriting sequences.

 Return to the pen interface page.

 Mario Enrique Munich - mariomu AT vision DOT caltech DOT edu