Quite similar to the foot control, the hand control uses hand gestures for browsing through medical images. The LEAP Motion tracks the user's hands with infrared cameras and LEDs. Thus, it allows to recognize complex hand gestures, so that the user is able to give commands just with his hands. Even though the Unreal Engine plugin provided to use the LEAP Motion has already a set of gestures implemented, we decided to design our own gesture. We called this gesture the Roll Gesture
One can use the roll gesture by rotating the arm around the radial bone. With the hand pointing at about ten o'clock, the scrolling is paused. Roting it clockwise, one can scroll forwars, backwards when rotating the arm counter clockwise. There are two different scrolling speeds. If the rotation of the lower arm becomes greater, then the acceleration is increased. It is possible to use either the right arm, or the left arm, but not both at the same time, although it is allowed to change the active arm during the usage.
During our testing phase, the leap motion controller was attached to the HMD on the user's forehead. If we used our system during an actual surgery, of course the controller would have been attached to another surface, for example to the screen showing the images to browse. Since the leap motion gets confused, if more than one pair of arms are recognized, it might be a problem, but otherwise it is strictly forbidden in surgery that the employees are restricting each other's motion space.
The LEAP motion controller is able to capture the user's hands in a hemispherical area to a one metre distance.