Pen input device and method for tracking pen position

A method for capturing the position of the writing tip of a pen input device on a writing surface during a writing operation, the method comprising:

• determining movement data while the writing tip contacts the writing surface during the writing operation, said movement data representing changes between successive positions of said writing tip on said writing surface, said determining said movement data comprises acquiring successive movement images using a first optical image sensor, producing movement image data representing said successive movement images, and determining said movement data from said movement image data using a movement detection engine that produces said movement data using said movement image data derived from said successive movement images captured using said first optical image sensor;
• determining position data at least once during said writing operation as part of a position detecting operation that is activated intermittently during said writing operation, said position data representing a position of said writing tip on said writing surface, said determining said position data comprises acquiring a position image using a second optical image sensor, producing position image data representing said position image, and determining said position data from said position image data using a position detection engine that produces said position data using said position image data derived from said position image captured using said second optical image sensor, said determining said position data includes using marks made on said writing surface by at least two writing operations as a positional reference, wherein each of said two writing operations includes said writing tip being in contact with said writing surface followed by said writing tip not being in contact with said writing surface;
• and
• linking said position data and said movement data.