Mobile computing devices allow people to access their digital content from everywhere. In order to be light and portable, mobile devices have a compact shape rendering the display relatively small. As a result, mobile devices have only a small amount of screen real estate, which limits the ability of users to work productively, collaboratively, and comfortably. Recent progress in projection technology has led to a new class of interaction devices; mobile projectors. Today, mobile projectors, also referred to as pico projectors, are small and lightweight enough to be comfortably held in one hand. They provide a large yet mobile display. Pico projectors have been embedded into mobile phones and cameras, prototyped as interactive stand-alone devices, used in research projects as part of wearable systems, utilized as gaming devices, and have been used for collaboration. Although it is expected that in 2015 more than 27 million mobile projectors will be sold, few research projects have investigated handheld projector interaction and little is known about the human factors underlying interaction methods, user performance, and interface design.
The main aim of this dissertation is the exploration, implementation, and evaluation of peephole interaction, an interaction method particularity suited to mobile projection interaction. Over the course of this research, we developed interactive handheld projector prototypes that enabled the first tests of peephole interaction outside laboratories. These prototypes were then used to conduct experiments and user tests in order to analyze user performance, find key characteristics of peephole interaction, and evaluate mobile projection interaction. As a result, this dissertation addresses a wide range of human factors issues. We provide deep insights into target acquisition modeling for peephole interaction, show that spatial memory performance can be improved by using peephole interaction on handheld projectors, study simulator sickness during handheld projector interaction, and we propose a solution to eliminate the chance of accidently blinding bystanders with a mobile projector.