An Optical Pen Tracking System as Alternative Pointing Device

A webcam together with a standard pen can replace a mouse as pointing device for many common user interaction tasks. We provide an implementation of a dedicated image-processing component integrated in a ready-to-use software tool that acts as mouse alternative. The image-processing component is responsible for tracking the head of a pen based on shape and colour information retrieved in a quick and integrated initial pen-calibration phase on the basis of a Hough transform triggered by a simple motion detection cycle. The tracked 2D position of the pen-head seen by the webcam is used to smoothly position the mouse cursor. Combined with an auto-clicking mechanism we can replace mouse-based user interaction. The system tolerates changing lighting conditions to a certain degree, does not need time-consuming geometric camera calibration and thus works with off-theshelf webcams. First user experiences show that this technology can partially replace mouse interaction for Repetitive Strain Injury (RSI) patients as well as completely replace mouse interaction within dedicated environments such as presentation booths or simple games.