As the user moves the pointing device around the workspace, there is a natural tendency for the device to rotate, as shown in figure 4. This, in turn, may cause loss of tracking. In order to avoid loss of tracking, the smallest SSD value from each search is compared to a threshold. If the smallest SSD rises above this threshold, then the reference template is updated using the contents of the image at time k-1 at the detected position.
Tracking fingertips is an example of a simple fast visual process which can be used to change the nature of the interaction between man and machine. Vision can also be used to make the machine aware of the user by detecting, tracking and wathing his face.
Figure 4: Change in reference template as a function of finger orientation.