Adaptive Display of Virtual Content for Improving Usability and Safety in Mixed and Augmented Reality
In mobile augmented reality, a number of barriers still exist that make head worn devices unsafe and difficult to use. One of these problems is the display of content in or around the user's field of view, which can result in occlusion of physical objects, distractions, interference with conversations, and a limited view of the user's natural environment. This thesis proposes the use of dynamic content display and field of view manipulation techniques as a step towards overcoming these safety and usability issues. More specifically, I introduce novel strategies for dynamic content movement, gaze depth tracking techniques for automated content management, and hands free spatial manipulation of the user's field of view. In combination with a number of new head mounted display prototypes, these methods can decrease the invasiveness of and increase the usability of head worn displays and related mixed and augmented reality applications. In addition to proposing frameworks and strategies for improving usability and safety, new information about the human eye, brain, and perception of virtual content are revealed and discussed. In order to conduct an initial comparison of standard mobile interfaces to head mounted displays, I first describe pilot experiments that study user tendencies related to viewing and placing text in mobile environments. The experiments studied smartphone and head mounted display use, and tested general environmental awareness and performance between the two devices for concentration intensive mobile tasks. Results showed that head mounted displays already have some advantages in terms of environmental awareness, but more importantly, users would prefer text that is affixed to visible locations in the background rather than affixed to a single point on the head mounted display screen. Since users' environments are constantly and dynamically changing, variables like lighting conditions, human or vehicular obstructions in users' paths, and scene variation interfered with viewing content. Consequently, I proposed the use of a new dynamic text management system that actively manages the appearance and movement of text in a user's field of view. Research to date lacked a method to migrate user centric content such as e mail or text messages throughout a user's environment while mobile. Unlike most current annotation and view management systems, my strategy utilizes camera tracking to find dark, uniform regions along the route on which a user is travelling in real time. I then implement methodology to move text from one viable location to the next to maximize readability. Because interpersonal interactions such as conversations and gestures are of particular importance, I also integrate face detection into the movement strategy to help prevent virtual content from occluding or interfering with a user's conversation space. A pilot experiment with 19 participants showed that the text placement of the dynamic text algorithm is preferred to text in fixed location configurations. A second experiment on real time videos comparing automatic and manual text placement showed that this strategy can mimic human placement tendencies with approximately 70% accuracy. A last experiment testing the conversation management algorithm showed a 54.8% reduction in the