Unobtrusive Augmentation of Physical Environments

ii iii Abstract The fundamental idea of Augmented Reality (AR) is to improve and enhance our perception of the surroundings, through the use of sensing, computing and display systems that make it possible to augment the physical environment with virtual computer graphics. AR is, however, often associated with user-worn equipment, whose current complexity and lack of comfort limit its applicability in many scenarios. The goal of this work has been to develop systems and techniques for uncomplicated AR experiences that support sporadic and spontaneous interaction with minimal preparation on the user's part. This dissertation defines a new concept, Unobtrusive AR, which emphasizes an optically direct view of a visually unaltered physical environment, the avoidance of user-worn technology, and the preference for unencumbering techniques. The first part of the work focuses on the design and development of two new AR display systems. They illustrate how AR experiences can be achieved through transparent see-through displays that are positioned in front of the physical environment to be augmented. The second part presents two novel sensing techniques for AR, which employ an instrumented surface for unobtrusive tracking of active and passive objects. These techniques have no visible sensing technology or markers, and are suitable for deployment in scenarios where it is important to maintain the visual qualities of the real environment. The third part of the work discusses a set of new interaction techniques for spatially aware handheld displays, public 3D displays, touch screens, and immaterial displays (which are not constrained by solid surfaces or enclosures). Many of the techniques are also applicable to human-computer interaction in general, as indicated by the accompanying qualitative and quantitative insights from user evaluations. The thesis contributes a set of novel display systems, sensing technologies, and interaction techniques to the field of human-computer interaction, and brings new perspectives to the enhancement of real environments through computer graphics. iv v Acknowledgments