Mobile devices have so far been personal tools. With their evolution of increased functionality, however, these devices have begun to be used in a shared fashion by multiple people. This chapter discusses techniques allowing multiple people to share mobile devices by projecting their displays and conducting intuitive manipulations on them. The chapter first shows overviews of systems and technologies related to location-aware projection and several interaction techniques. Then, a system called Hotaru that implements intuitive manipulation techniques on projected displays of multiple mobile devices is described. Hotaru allows a user to annotate or rotate a picture or a document on a projected display by using his finger and intuitively to transfer a file between multiple devices by overlapping their projected displays. User studies of Hotaru indicated that the proposed manipulation techniques could support multiple people in a single location in conducting their tasks. Research issues on projected displays of mobile devices are raised.
Key Terms in this Chapter
Finger Gesture Recognition: Finger gesture recognition is the interpretation of human finger gestures and the utilization of this as input for a computer. Computer vision techniques or those with inertial sensors (e.g., accelerometers) are mainly used for the recognition.
Colocated Collaboration: Colocated collaboration is a type of face-to-face collaboration where people share their place and time. However, colocated collaboration is different from a traditional face-to-face collaboration in that the former is usually discussed in the context of a computationally augmented environment.
Movable Projected Display: A projected display is a screen image of a computer projected onto a surface through a projector and used as a display for the computer. A projected display becomes movable when a computer with a projector is light and small, such as a mobile device.
Projectable Interface: A graphical user interface of a computer usually appears on its display and is manipulatable by using a mouse or a keyboard. A projectable interface is a user interface projected onto any surface such as a wall, and manipulatable by pointing or touching it with a laser pointer or a finger.
Manipulation by Projection: Manipulation by projection is a new technique that allows a user to manipulate an object by overlaying an image using a mobile projector. For example, by projecting a map image on an area where a robot is placed, a user can make the robot follow a path on the map. A user can translate or rotate the projected map by changing his standing point or rotating his mobile projector, in order to make the robot move as he intends.
Location-Aware Projection: Location-aware projection is the projection of a graphical image generated by a computer onto a surface based on the 3-D position and orientation of the computer or the locations of people who view the image.
Intuitive Manipulation Technique: Using a mouse and a keyboard as an input device for a computer is often irritating and awkward. Although less awkward and bothersome techniques using a mouse and keyboard have been investigated, one of the intuitive manipulation techniques is to use different devices or methods, for example, natural human gestures such as finger/hand gestures, speech/sounds and so on, as input to a computer.