This paper presents a novel projected pixel localization principle for online geometric registration in dynamic projection mapping applications. We propose applying a time measurement of a laser projector raster-scanning beam using a photosensor to estimate its position while the projector displays meaningful visual information to human observers. Based on this principle, we develop two types of position estimation techniques. One estimates the position of a projected beam when it directly illuminates a photosensor. The other localizes a beam by measuring the reflection from a retro-reflective marker with the photosensor placed in the optical path of the projector. We conduct system evaluations using prototypes to validate this method as well as to confirm the applicability of our principle. In addition, we discuss the technical limitations of the prototypes based on the evaluation results. Finally, we build several dynamic projection mapping applications to demonstrate the feasibility of our principle.

The ideal AR x-ray vision should enable users to clearly observe and grasp not only occludees, but also occluders. We propose a novel selective visualization method of both occludee and oc-cluder layers with dynamic opacity depending on the user's gaze depth. Using the gaze depth as a trigger to select the layers has a essential advantage over using other gestures or spoken commands in the sense of avoiding collision between user's intentional commands and unintentional actions. Our experiment by a visual paired-comparison task shows that our method has achieved a 20% higher success rate, and significantly reduced 30% of the average task completion time than a non-selective method using a constant and half transparency.