A vision based motion interface for mobile phones

In this paper we present an interface system for the control of mobile devices based on motion and using existing camera technology. In this system the user can control the phone's functions by performing a series of motions with the camera and each command is defined by a unique series of these motions. A sequence of motion features is produced using the phone's camera and these characterise the translation motion of the phone. These sequences of motion features are classified using _Hidden Markov Models_ (HMMs). In order to improve the robustness of the system the results of this classification are then filtered using a likelihood ratio and the entropy of the sequence to reject possibly incorrect sequences. When tested on 570 previously unseen motion sequences the system incorrectly classified only 5 sequences