A Framework for Relating Head-Mounted Displays to Mixed Reality Displays

The Head Mounted Display (HMD) is discussed as a subset of Mixed Reality (MR) displays. A definition of MR is given, in terms of image mixtures along a Reality-Virtuality (RV) Continuum, including the subclasses of augmented reality (AR) and augmented virtuality (AV). In relation to actual task execution, the relative need for local guidance information versus more global planning and navigational information is discussed. A taxonomic framework for classifying MR systems is presented, in terms of not only the RV continuum, but also the degree of centricity of the observer relative to a nominal viewpoint and the extent of control-display congruence. Several practical examples of MR systems are presented, all from the domain of surgery, and for each a volume within the MR design space is proposed.