Back-Pointer ? Fitts´ law analysis of natural mobile camera based interactions

Typical mobile phone based interactions are performed by utilizing a touchscreen. Although natural to the user, this type of direct interaction results in blocking portions of the screen while interacting with the device because the finger or hand is directly on top of the display. Back Pointer presents an alternative input mechanism for mobile devices where the back facing camera captures the motion of the user´s index finger as it is moved. A user study was performed by 8 users who held a mobile phone in landscape mode with both hands and navigated a target selection challenge by moving the left index finger in 3D space on the back of the phone using both an opaque interface and a translucent interface where the finger was visible during the task. The study showed the opaque interface was not usable, unless the translucent interface was presented first. When presenting the translucent interface first, there was no significant difference in performance. The study also determined the average distance from the lens during the task, which could provide specifications for a macro camera dedicated for back of device camera based interactions.